Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR SEPARATING AND RECOVERING ETHANE AND HEAVIER
HYDROCARBONS FROM LNG
BACKGROUND OF THE INVENTION
[0001] The present invention example relates to the field of processing
gasses in a
liquid or fluid phase such as for LNG (Liquified Natural Gas) and NGL (Natural
Gas
Liquids) as known in the oil and gas industry and the recovery of C2 and C2+
(ethane +)
components from the hydrocarbon fluid streams. More particularly, the present
invention
relates to the recovery of ethane and less volatile compounds from hydrocarbon
fluid streams
such as, from near atmospheric or more pressure, stored or transported
cryogenic LNG
liquid/fluid feed streams, with practical and economic design and operation of
equipment to
achieve this.
[0002] This invention relates to a process for separation of less volatile
compounds,
such as ethane and less volatile compounds from hydrocarbon mixed streams for
example
liquefied natural gas (LNG) or other such as petrochemical refinery streams.
It is anticipated
it could find utility in non-hydrocarbon related applications.
[0003] Background Art
[0004] Natural gas is being more often liquefied and transported in ocean
going LNG
tankers to LNG receiving terminals, worldwide. The LNG can then be re-
vaporized and
transported via pipelines carrying natural gas. The LNG can have other less
volatile
components besides the predominantly methane (methane usually makes up more
than 50%
of the LNG). It is usually necessary to remove various amounts of the less
volatile
components either to meet compositional specifications or Heating Value
contractual Willis,
or in order to obtain greater value from the less volatile heavier compounds.
This may be
carried out at production, storage, loading terminals or receiving terminals.
Storage of LNG
presents the problem of uncontrollable "roll overs" caused by density
inversions.
[0005] U.S. Patent No. 6,510,706 (Stone et al.) (January 28, 2003)
discloses a process
for removing hydrocarbons less volatile than methane from a pressurized liquid
natural gas
(PLNG). PLNG is heated in a heat exchanger, thereby vaporizing at least a
portion of the
PLNG. The partially vaporized PLNG is passed to a fractionation column. A
liquid stream
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enriched with hydrocarbons (C<sub>2</sub>+ or C<sub>3</sub>+) less volatile than methane
is withdrawn
from a lower portion of the fractionation column and a vapor stream lean in
the hydrocarbons
less volatile than methane is withdrawn from an upper portion of the
fractionation column.
The withdrawn vapor stream is passed to the heat exchanger to condense the
vapor to
produce PLNG lean in hydrocarbons less volatile than methane.
[0006] U.S. Patent No. 7,165,423 (Winningham) (January 23, 2007) discloses
a
process for the extraction and recovery of ethane and heavier hydrocarbons
(C2+) from LNG.
The process covered by this patent maximizes the utilization of the beneficial
cryogenic
thermal properties of the LNG to extract and recover C2+ form the LNG using a
unique
arrangement of heat exchange equipment, a cryogenic fractionation column and
processing
parameters that essentially eliminates (or greatly reduces) the need for gas
compression
equipment minimizing capital cost, fuel consumption and electrical power
requirements. This
invention may be used for one or more of the following purposes: to condition
LNG so that
send-out gas delivered from an LNG receiving and regasification tenninal meets
commercial
natural gas quality specifications; to condition LNG to make Lean LNG that
meets fuel
quality specifications and standards required by LNG powered vehicles and
other LNG
fueled equipment; to condition LNG to make Lean LNG so that it can be used to
make CNG
meeting specifications and standards for commercial CNG fuel; to recover
ethane, propane
and/or other hydrocarbons heavier then methane from LNG for revenue
enhancement, profit
or other commercial reasons.
[0007] U.S. Patent No. 7,631,516 (Cuellar et al.) (December 15, 2009)
discloses a
process and apparatus for the recovery of ethane, ethylene, propane,
propylene, and heavier
hydrocarbons from a liquefied natural gas (LNG) stream is disclosed. The LNG
feed stream
is divided into two portions. The first portion is supplied to a fractionation
column at an
upper mid-column feed point. The second portion is directed in heat exchange
relation with a
warmer distillation stream rising from the fractionation stages of the column,
whereby this
portion of the LNG feed stream is partially vaporized and the distillation
stream is totally
condensed. The condensed distillation stream is divided into a "lean" LNG
product stream
and a reflux stream, whereupon the reflux stream is supplied to the column at
a top column
feed position. The partially vaporized portion of the LNG feed stream is
separated into vapor
and liquid streams which are thereafter supplied to the column at lower mid-
column feed
positions. The quantities and temperatures of the feeds to the column are
effective to maintain
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the column overhead temperature at a temperature whereby the major portion of
the desired
components is recovered in the bottom liquid product from the column.
[0008] U.S. Patent No. 7,216,507 (Cuellar et al.) (May 15, 2007) discloses
a process
and apparatus for the recovery of ethane, ethylene, propane, propylene, and
heavier
hydrocarbons from a liquefied natural gas (LNG) stream is disclosed. The LNG
feed stream
is divided into two portions. The first portion is supplied to a fractionation
column at an
upper mid-column feed point. The second portion is directed in heat exchange
relation with a
warmer distillation stream rising from the fractionation stages of the column,
whereby this
portion of the LNG feed stream is partially heated and the distillation stream
is totally
condensed. The condensed distillation stream is divided into a "lean" LNG
product stream
and a reflux stream, whereupon the reflux stream is supplied to the column at
a top column
feed position. The partially heated portion of the LNG feed stream is heated
further to
partially or totally vaporize it and thereafter supplied to the column at a
lower mid-column
feed position. The quantities and temperatures of the feeds to the column are
effective to
maintain the column overhead temperature at a temperature whereby the major
portion of the
desired components is recovered in the bottom liquid product from the column.
[0009] U.S. Patent No. 7,010,937 (Wilkinson et al.) (March 14, 2006)
discloses a
process for liquefying natural gas in conjunction with producing a liquid
stream containing
predominantly hydrocarbons heavier than methane is disclosed. In the process,
the natural gas
stream to be liquefied is partially cooled, expanded to an intermediate
pressure, and supplied
to a distillation column. The bottom product from this distillation column
preferentially
contains the majority of any hydrocarbons heavier than methane that would
otherwise reduce
the purity of the liquefied natural gas. The residual gas stream from the
distillation column is
compressed to a higher inteimediate pressure, cooled under pressure to
condense it, and then
expanded to low pressure to form the liquefied natural gas stream.
[0010] U.S. Patent Publication No. 20080098770 (Ransbarger) (May 1, 2008)
discloses a liquefied natural gas (LNG) facility employing an intermediate
pressure
distillation column for recovery of ethane and heavier components from the
processed natural
gas stream in a way that increases operational stability and minimizes capital
and operating
costs.
[0011] U.S. Patent Publication No. 20090221864 (Mak) (September 3, 2009)
discloses that LNG is processed in contemplated plants and methods such that
refrigeration
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content of the LNG feed is used to provide reflux duty to the demethanizer and
to further
condense a vapor phase of the demethanizer overhead product. In such plants,
the
demethanizer provides a bottom product to a deethanizer, wherein a
demethanizer side draw
provides refrigeration to the deethanizer overhead product to thus form an
ethane product and
deethanizer reflux.
[0012] There are other processes to separate the heavier than methane
hydrocarbons
from LNG. However, the present innovation involves independent experimenting
of all
variations until arriving at a complete and a flexible viable process showing
reduction of the
design to practice by using the industry standard based design "HYSYS CD"
computer
software Simulations tool (offered by Hypotech Company, Canada) which in
addition
supports the inventors' "practical" equipment design, sizing and the
operational information
necessary for providing the required enablement's for anyone skilled in the
art or science.
[0013] Additionally, to address the issues presented by the prior art
systems, the
inventors believe that use of the present invention can be made to mitigate
problems of the
uncontrollable "roll overs" (caused by density inversions) in storage, through
a process to
separate and recover ethane from such LNG with ethane content as low as about
1% and
lower. A part of the even leaner Lean LNG product as part of a liquid flash
product of the
Lean LNG product of this invention can be recycled to storage as part of a
"roll over" control
method. The separated heavier components have many uses such as for example,
petrochemical feedstocks or liquid fuels.
BRIEF SUMMARY OF THE INVENTION
[0014] To address the forgoing desires, the present invention describes a
process for
separating and recovering ethane and heavier hydrocarbons from LNG. In one
embodiment
of the present invention the steps include providing an undivided feedstock
stream containing
Rich LNG wherein the Rich LNG is in liquid form from a storage tank or other
source, the
Rich LNG comprising C1 and C2+ hydrocarbons, the Rich LNG having an ambient
storage
temperature and pressure. The next step involves pressurizing the feedstock
Rich LNG from
storage pressure up to a desired pressure followed by pumping the feedstock
Rich LNG into
the cool side of a heat exchanger, the heat exchanger having a cool side and a
hot side. The
desired pressure is typically dictated by any downstream process steps
involving the heat
exchanger, and/or is dictated by critical pressure properties of the desired
gas and liquid
mixture in the column.
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[0015] Then, the feedstock Rich LNG is heated within the heat exchanger
while
maintaining the feedstock Rich LNG below its bubble point to avoid
vaporization while in
the heat exchanger. In a preferred embodiment, the step of maintaining the
feedstock Rich
LNG below its bubble point to avoid vaporization while in the heat exchanger
is achieved by
regulating the pressure in the heat exchanger to maintain the Rich LNG in its
liquid phase
with no vaporization.
[0016] The undivided feedstock Rich LNG feed stream is directed from the
heat
exchanger to a processing column, the column comprising one or more stream
entry ports
along the height of the column to permit directing the stream into the column
at one or more
desired entry locations along the height of the column. The process then
involves generating
in the column a desired mixture comprising an overhead gas stream comprising
lighter
hydrocarbon products and a desired bottoms liquid stream comprising heavier
hydrocarbon
products. The overhead gas stream is directed from the column to the hot side
of the heat
exchanger. The next step involves cooling and condensing the overhead gas
stream against
the cold Rich LNG feedstock stream to foini, in whole or in substantial part,
a liquid
comprising Lean LNG product stream, any remaining incidental uncondensed
overhead gas
stream remaining as a gas.
[0017] The condensed product stream is then directed from the hot side of
the heat
exchanger to a receiving vessel. The liquid Lean LNG product is pumped from
the receiving
vessel to a desired location. The bottoms liquid stream is directed from the
column to one or
more reboiler arrangements wherein heating of the bottoms liquid stream in the
reboiler takes
place. At least a portion of the heated bottoms stream are preferably returned
to the column,
the column being further outfitted with one or more heated bottoms stream
entry ports along
the height of the column to permit directing the heated bottoms stream into
the column at one
or more desired heated bottoms stream product entry locations along the height
of the
column.
[0018] The column bottoms stream is discharged directly from the column or
from
the reboiler and the bottoms stream is transferred to a desired location. Any
gas in the
receiving vessel is transferred to a desired location.
[0019] In another embodiment, this process may further comprise the steps
of:
directing the feedstock Rich LNG from the heat exchanger through a valve and
into a
degasser; directing the liquid stream from the degasser into the processing
column, the
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column being further outfitted with one or more degasser liquid stream entry
ports along the
height of the column to permit directing the degasser liquid stream into the
column at one or
more desired degasser liquid product entry locations along the height of the
column; and
directing any gas stream in the degasser to the column, the column being
further outfitted
with one or more degasser gas stream entry ports along the height of the
column to permit
directing the degasser gas stream into the column at one or more desired
degasser gas product
entry locations along the height of the column.
[0020] A portion of the column bottoms stream may be directed to the
degasser to
warm the feedstock and alter the composition of the total feed to the column.
[0021] The process may include the additional steps of recovering heat
from the
column bottoms stream.
[0022] In a preferred embodiment of the process, the NGL product comprises
a
desired high or low percentage of ethane.
[0023] In another embodiment, the Lean LNG stream may be directed to a
storage
facility or to further processing to vaporize the Lean LNG.
[0024] In one embodiment. at least some of the Lean LNG stream is directed
to the
column, the column being further outfitted with one or more Lean LNG stream
entry ports
along the height of the column to permit directing the Lean LNG stream into
the column at
one or more desired Lean LNG product entry locations along the height of the
column.
[0025] The process may also comprise the additional steps of: directing at
least some
of the Lean LNG stream into one or more additional heat exchangers; heating
the Lean LNG
within the one or more heat exchangers while maintaining the Lean LNG below
its bubble
point to avoid vaporization while in the heat exchanger; directing the Lean
LNG from the
heat exchanger through a valve and into a degasser or other vessel; directing
the liquid stream
from the degasser or other vessel to a desired location; and directing any gas
stream in the
degasser or other vessel to a desired location. In one embodiment, the liquid
stream may be
directed from the degasser or other vessel into another heat exchanger
arranged in series
relationship and these additional steps be completed.
[0026] In one embodiment of the process, the Lean LNG stream is directed
to a Rich
LNG feedstock storage containing a level of Rich LNG feedstock, the storage
further
comprising one or more jet or sparger systems located along the height of the
storage to
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permit introduction of the Lean LNG stream into the storage either above
and/or within the
level of stored Rich LNG feedstock.
[0027] In another embodiment, the Lean LNG stream is directed to any
stored source
of LNG, wherein it is sparged into the stored source of LNG at a desired
location.
[0028] In yet another embodiment, any gas phase in the receiving vessel is
transferred
to a compressor wherein the gas phase is compressed and then the compressed
gas is directed
to a desired location. The compressed gas may be directed into a heat
exchanger wherein the
compressed gas is condensed to form a full or partial condensate Lean LNG, the
condensate
then being directed to a desired location. The condensate Lean LNG stream may
be directed
to a storage facility. In one embodiment, at least some of the condensate Lean
LNG stream is
directed to the column, and introduced into the column via the one or more
Lean LNG stream
entry ports to pellnit directing the Lean LNG stream into the column at one or
more desired
locations along the height of the column. The heat exchanger may be cooled by
an external
refrigeration stream or by by a second LNG stream.
[0029] In one embodiment, of the process, a second cold LNG stream is
introduced
directly into the degasser to mix with the feedstock Rich LNG. In another
embodiment, the
second cold LNG stream may be introduced directly into the column, the column
being
further outfitted with one or more LNG stream entry ports along the height of
the column to
permit directing the LNG stream into the column at one or more desired LNG
stream product
entry locations along the height of the column.
[0030] In one embodiment of the operation of the process, the step of
cooling and
condensing the overhead gas stream against the cold Rich LNG feedstock stream
does not
form any incidental gas.
[0031] In one embodiment of the process, the discharged bottoms stream
comprises
up to 99% of the C2 hydrocarbons in the Rich LNG feedstock and substantially
all of the C3+
as a NGL, the NGL product additionally meeting without any further processing
close to or
substantially a Pipeline Quality Specification of = or < 0.5%v C1.
[0032] In another embodiment, the discharged bottoms stream comprises an
NGL
Product of substantially with TVP of up to = or < 400 psig, up to C1= or
<0.5%v, up to
51%mol C2 or more fraction.
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[0033] In yet another embodiment, the Rich LNG feedstock comprises between
1%
mole C2 to that exceeding 40 to 50 mole % C2.
[0034] The process of the present disclosure may run in a high "ethane
recovery"
(90% or more) mode to recover up to 99% ethane and substantially 100% propane.
[0035] In one embodiment, the processing column employed comprises about
10
theoretical trays. The column has flexible configurations and preferably is
configured and
integrated in a multitude of operability and functional configurations
selected from the group
consisting of distillation columns, extractive distillation columns, reboiled
absorption
columns, absorption columns, lean oil absorber columns, fractionation columns,
stripping
columns, refluxed stripping columns, and reboiled stripping columns.
[0036] In one embodiment, substantially no tail gas (gas from condensed
overhead
stream) is formed even where there is as low as 1% C2 in the feedstock.
[0037] In operation of the process, NGL of Pipeline Quality specs is
produced, even
when the system is operating in deep high ethane extraction mode (90% plus).
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0038] FIG. 1A is a flow diagram of a HYSYS Simulation of a LNG processing
plant
in accordance with the present invention.
[0039] FIG. 1B is the detail area 1B shown in FIG. 1A.
[0040] FIG. 2A is another flow diagram of a HYSYS Simulation of a LNG
processing plant in accordance with the present invention adding additional
processing
options to those described in connection with FIG. 1A.
[0041] FIG. 2B is enlarged view of detail area 2B shown in FIG. 2A.
DETAILED DESCRIPTION OF THE INVENTION
[0042] The present invention is generally concerned with the practical
recovery or
separation of less volatile components from a mix of other components as for
example in this
instance methane rich stream is separated from a stream of less volatile
components than
methane as may consist in LNG and such streams.
[0043] Also disclosed are designs for a novel but practical method and an
arrangement, management and control of it to achieve such separation while at
the same time
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providing means and direction for achieving practical sizing and/or design
and/or operation
of the equipment used in perfoirning the separations.
[0044] It further is designed and shown as for in this instance to take a
"rich" in
varying degrees, in lower volatile components than methane in LNG (termed
"rich LNG")
stream, from its storage or transport conditions of but particularly liquid
form, as far as
possible maintain that phase or form while cross exchanging its cold energy
condition to
absorb heat from one of the product streams particularly the lean in the less
volatile
components LNG (termed "lean LNG") stream obtained from equipment further
downstream
such as the vapor overhead stream from the processing column or by heating by
other means
of heating. This is a particular difference with the present innovation from
other existing prior
art offered or provided by others, in that the other prior aft provides a
design criteria or
direction or instructions requiring a portion of the Rich LNG feed stream or
splits of the Rich
LNG stream be vaporized before feeding it to the processing column. As
demonstrated for
the present invention in the normal Ethane Recovery mode and provided result
tables, there is
no vaporization of the Rich LNG feed stream (stream 2) until the system is
operated in an
Ethane Rejection mode.
[0045] In other words, heat is exchanged in this heat exchanger (herein
identified as
LNG exchanger) while maintaining a liquid phase for the rich LNG stream and at
the same
time condensing the lean LNG vapor or mixed phase stream obtained from the
processing
column arrangement shown downstream from the LNG exchanger; and more
particularly not
vaporizing it in the LNG exchanger as one of the criteria for overall control,
thereby resulting
in a practical and reasonably sized heat exchanger. The type of heat exchanger
can be any of
the heat exchanger systems known in the art. The reference to a heat exchanger
can include
an individual heat exchanger or a multitude of individual heat exchangers. One
manner in
which to maintain the mixture in its liquid state is to maintain the mixture
substantially or
discernibly below bubble point. This can be achieved via the regulation of the
pressure in the
exchanger, e.g., by pressurizing the feedstock stream with a pump (or other
motive power
system) prior to entry into the exchanger and by maintaining sufficient back
pressure in the
system downstream of the exchanger (e.g., at the column or other location or
pressure
restrictor) to maintain the desired pressure in the exchanger. Maintaining the
desired pressure
in the exchanger permits the system to maintain liquid regimes for LNG coming
in and LNG
leaving the exchanger. This provides economy by conserving pressuring energy
both in
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terms of avoiding the use of unnecessary equipment and regarding the end
PIPELINE
gasifying/compressions.
[0046] A provision is provided to degas the liquid stream if necessary
prior to feeding
the warmed rich LNG to the processing column as a safety feature or a
particular operational
feature, prior to feeding the liquid stream at a top or high position in the
processing column.
[0047] In the processing column the more volatile part of LNG is stripped
from the
less volatile part.
[0048] Further, the present invention avoids the usual or particular prior
art
instructions or necessity of pre-vaporizing in part or such and/or of
splitting the feed stream
prior to or after the LNG heat exchanger and/or having to have any part of or
the whole feed
stream pre-vaporized prior to feeding the processing column.
[0049] Further, the invention provides
method/process/system/operations/means for
practical and/or simplicity of design with resultant economy of equipment
and/or utilities
and/or operations.
[0050] This invention makes the design practicable and/or economic whereas
some
prior art designs or systems or methods or process(es) require additional
utilities or
equipment or as demonstrated have equipment design tending towards infinite or
indeterminate heat exchange surface areas required of LNG exchanger design or
have
impractical temperature crosses in the LNG exchanger.
[0051] Further, the invention provides
method/process/system/operations/means for
design and operation in particularly eliminating compression/recompression of
the Lean LNG
methane rich vapor product of the processing column by re-
converting/condensing it fully
back to liquid. The processing column may be employed in various modes of
operation. The
processing column can function as any type of column, such as for example and
not by way
of limitation, as a distillation column, extractive distillation column,
reboiled absorption
column, absorption column, lean oil absorber column, fractionation column,
stripping
column, refluxed stripping column, reboiled stripping column, and the like.
These columns
can be emulated in various proportions effectively making this a hybrid column
with various
degrees of functions of these column configurations with additional pressure
swing
functionality or pressure variability functionality to match most effective
use of this process
of disclosure.
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[0052] Highlights of the present invention include: unique arrangement of
the pre-
column, at/within-column, and post-column major parts of the process; flexible
variability of
the RLNG source pressure (via pump 22 or other motive power system) ¨ this
pressure
control is important for the rest of the process; the heat exchanger 30
operation; regulating
internal pressure of the RLNG-cold side of exchanger via a back-pressure
controller (33); the
feed composition/enthalpy variability options with item degasser 40; the
column operability
functions -- variability with multiple optional combinations of column source
streams and
their locations on the column, the variability of column pressure and its
effect on its
operations (via back pressure controller (16)); the overall combination of
items downstream
of stream 8 and 9 to provide variability of the pressure on the exchanger
condensing hot side;
and optional process embodiment to re-produce LLNG as vaporized LLNG without
compression equipment with economy of equipment/complexity/energy.
[0053] A flexibility integrated methodology and system for extracting less
volatile
components from a fluid stream working in high percentage or low percentage
extracting
modes is disclosed, such as, showing the extracting/rejecting of ethane in
this inventive
process (of extracting NGL from LNG) while not requiring vaporization of Rich
LNG
(RLNG) prior to separation in to LNG/NGL in a column(s) and essentially on a
large part
eliminating the requirements of compressing (optional) any gas to produce Lean
LNG
(LLNG) while taking the feed RLNG extracting its NGLs in the processing system
and
reproducing Lean LNG of spec from Rich LNG.
[0054] Referring to FIGS. 1A, 1B, 2A and 2B there is shown a flow diagram
of a
LNG processing plant used in a HYSYS software simulation in accordance with
the present
invention. The Tables set forth below contain the operational parameters used
in the
HYSYS simulations of the methods of the present invention. The process flow
diagram
shown in the Figures is further described as follows:
[0055] It is contemplated that the major equipment involved in the process
will be:
[0056] A. Feed pump 22 for Rich LNG from storage/transport location 20,
[0057] B. (Optional Rich LNG sub-cooler utilizing LNG "cold") 13,
[0058] C. LNG Exchanger 30,
[0059] D. Degasser vessel 40 (optionally can be an inline degasser).
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[0060] E. Processing Column (or fractionation column) 50, its internals
(Trays or
Packing) and Reboiler (collectively called "Column"),
[0061] F. Column Bottom Discharge pump,
[0062] G. Receiving Vessel 70 for the condensed Column Overhead stream
7, 9,
[0063] H. (Optionally, in any other contemplated modes of operation,
compressor
80 for tail gas stream 11 from Receiving Vessel 70),
[0064] I. Discharge Pump 74 for the Lean LNG condensed stream 10, 10A,
[0065] J. Flash, Pump and distribution equipment (not shown) for
product Lean
LNG (stream 10A or its partial product as an option equipment to further
recycle part of the
Lean LNG (stream 10A) back to storage 20 as "Roll Over" control method
wherever it is
implemented.
[0066] More particularly, referring to the figures, an LNG (or RICH LNG)
stream 1 is
pumped via pump 22 from a storage location 20 (e.g., tank 20 having LNG level
20A)
through suitable conduit through a valve 24, where it becomes labeled stream
1A. It will be
understood by those of ordinary skill in the art that suitable conduit is used
throughout the
flow diagram to connect together the various components as shown to permit (as
described)
fluid communication between components for transporting the various product
streams
therein. Stream 1A is directed into the cool side of a heat exchanger 30 via
heat exchanger
inlet 31, and is discharged out of the heat exchanger 30 as stream 2 via heat
exchanger outlet
32. As will be further described below, the heat exchanger 30 has a hot side
that is in turn
receiving one or more warm process stream(s), particularly the overhead stream
7 from a
processing column 50. The warmed LNG stream 2, in its liquid state, is passed
through a
valve 33 where it becomes stream 3 or 3A. The valve 33 can be used to, e.g.,
regulate the
pressure of stream 3 and 3A, for example, to lower the pressure of stream 3
after stream 3
exits the heat exchanger 30 prior to entering the processing column 50. In one
embodiment,
the warmed LNG stream 3, still in liquid state, is then passed into a
degassing vessel 40 via
degasser inlet 43, though no vaporization is anticipated under the normal
modes of operation
of the invention. The degassed liquid stream 4 is discharged, via degasser
lower outlet 44 for
discharging stream 4, from the vessel 40 and is fed to the processing column
50 at desired
location(s) (using an optional pump 48, as may be desired). The degassed gas
stream 5 is
discharged, via degasser upper outlet 45, from the vessel 40 and is fed to the
processing
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column 50 at desired location(s) via inlet(s) 55 (and in connection with
suitable valve(s)
17D). In another embodiment, the warmed LNG stream 3A, still in liquid state,
is then
passed directly to the processing column 50 and introduced into the column at
any desired
location via one or more suitable inlet ports (not shown).
[0067] The processing column 50 is outfitted with one or more processing
column
inlet(s) 54 for receiving stream 4 at various locations along the height of
the column 50 (in
connection with suitable valve(s) 17E). The column 50 is also outfitted with
one or more
processing column inlet(s) 55 for receiving stream 5 at various locations
along the height of
the column 50. In the processing column 50, the more and less volatile
components are
separated and the lighter components ("overhead", stream 7) predominantly are
discharged
out of the column 50 from the upper section (via processing column outlet 57)
and the less
volatile components ("bottoms", stream 6) are discharged from a lower section
(via
processing column outlet 56).
[0068] The column bottoms may be directed to storage or end use locations
or be
circulated to be mixed with the warmed feed stream or alternatively connected
to another
portion of the column (which can be piped to be able to provide inlet to the
column at various
stages or locations in the column for flexibility) that would optimize the NGL
extraction with
C2 extraction or Rejection mode operations or to obtain specified NGL
requirements.
[0069] The bottoms (stream 6) from processing column 50 are discharged
(via
discharge port 56) to a pump (not shown) which may circulate some of the
bottoms back to
the column 50 or the degassing vessel 40. For example, the bottoms (stream 6)
may be
directed into any type of column bottoms reboiler arrangement 60 via reboiler
inlet 66. The
reboiler has an energy stream 60A for heat in the reboiler 60. The NGLs from
stream 6 may
be discharged from the reboiler 60 as NGL stream 6A via reboiler outlet 66A.
NGL stream
6A may be recycled to degasser 40 (through suitable valve 17C) and introduced
therein via
degasser inlet 46. NGL stream 6A may also be recycled (as stream 6A-1) to the
processing
column 50 and introduced therein via various processing column inlet(s) 56A
for receiving
stream 6A-1 at various locations along the height of the column 50 in
coordination with
suitable valve(s) 17F. The end product NGLs from stream 6 may also be
discharged from the
reboiler 60 as NGL stream 6 via reboiler outlet 66B where they can be directed
to a desired
end use/storage location (not shown), or where they could be directed to a
splitting junction /
valve 85 via inlet 86. The splitter/valve 85 could direct stream 6 out the
outlet 87 (as stream
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6A) or out the outlet 88 (as stream 6) to a desired location (not shown). The
liquid NGLs
could also be boiled within the reboiler and directed, via reboiler outlet 66C
as stream 6C, to
the processing column 50 and introduced therein via various processing column
inlet(s) 56C
for receiving stream 6C at various locations along the height of the column 50
in coordination
with suitable valve(s) 1711.
[0070] In the processing column 50, the lighter components ("overhead",
stream 7)
predominantly leave the column 50 from the upper section (via processing
column outlet 57
for discharging stream 7) and are then directed through valve 16 (used to
regulate pressure)
where stream 7 becomes labeled as stream 8. Alternatively, stream 7 could be
directed
through a compressor (not shown) whereafter stream 7 would be labeled stream
8,
[0071] The overhead stream 7, 8 is directed into the hot side of the heat
exchanger 30
via heat exchanger inlet 38 where the stream 8 is cooled and condensed against
the Rich LNG
stream in the LNG exchanger 30. In this manner, the overhead methane rich
vapor stream (7,
8) from the column 50 is diverted to the LNG exchanger 30 where it is
condensed in cross
exchange of heat with the cold Rich LNG feed (1A) and is anticipated to
condense up to
100% into Lean LNG liquid (stream 9) which is then directed out of the
exchanger 30 via
exchanger outlet 39. The Lean LNG (stream 9) (which is a C1-rich mixture of
liquid and
gas)) is directed into and stored in a surge drum or receiving vessel 70 (via
vessel inlet 71).
The Lean LNG stream may be moved from the vessel 70 (as liquid stream 10) via
vessel
outlet 72 by way of a pump 74 at a required/desired pressure (stream 10A).
[0072] Stream 10A (Lean LNG) can then be further directed to storage or
other
desired location (e.g., storage tank, pressurized pipeline, not shown).
[0073] Stream 10A (Lean LNG) may also be routed through a splitter or
junction /
valve 75 (via inlet 76). Stream 10A may be directed through valve 75 (via
outlet 77) as
stream 10E to a desired location or storage facility for the Lean LNG product.
For example,
and referring to FIG. 1B (which illustrates detail area 1B from FIG. 1A),
stream 10E (Lean
LNG) may be directed to one or more further heat exchanger processing unit(s)
1C. The
stream 10E would enter heat exchanger 100 and depart as stream 1OF through a
valve 200 or
other pressure maintenance system (for maintaining the desired pressure in the
heat
exchanger 100 to maintain the Lean LNG in liquid form as it is heated in the
heat exchanger
much like with the operation of exchanger 30 described herein) where stream
1OF becomes
stream 10G. The heat exchanger 100 also receives desired heat transfer stream
99A (which
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can be an independent hot stream or a hot side stream from another part of the
process) which
then transfers thermal energy and departs exchanger 100 as stream 99B (which
can be
directed to other locations as desired). Much like with stream 3, stream 10G
is fed into a
degasser or other receiving vessel 300 where the liquid phase can then be
directed out as
Lean LNG stream 10H and any gas can be directed out as gas stream 25A. Side
stream 99C
can pass through the vessel 300 (to, e.g., transfer thennal energy) and exit
the vessel as side
stream 99D. Gas stream 25A can then pass through a valve 700 where it becomes
gas stream
25B and can then be directed to a desired location, such as, by joining it
with gas product
stream 12A to create gas product stream 12B. Liquid stream 1011 can be then
directed to a
desired location, such as, an inlet stream 10H for another heat exchanger
processing unit.
[0074] For example, still referring to FIG. 1B, a second heat exchanger
processing
unit could be tied into the first heat exchanger processing unit 1C in series
fashion. For
example, the liquid product stream 10H (from unit 1C) would enter another heat
exchanger
400 and depart as stream 10J through a backpressure/level control valve 500 or
other pressure
maintenance system (for maintaining the desired pressure in the heat exchanger
400 to
maintain the Lean LNG in liquid form as it is heated in the heat exchanger
much like with the
operation of exchanger 30 described herein) where stream 10J becomes stream
10K. The
heat exchanger 400 also receives desired heat transfer stream 99E (which can
be an
independent stream or a side stream from another part of the process) which
then transfers
thermal energy and departs exchanger 400 as stream 99F (which can be directed
to other
locations as desired). Much like with stream 3, stream 10K is fed into another
degasser or
other receiving vessel 600 where the liquid Lean LNG phase can then be
directed out as Lean
LNG stream 10L and any gas can be directed out as stream 25C. Side stream 99G
can pass
through the vessel 600 (to, e.g., transfer thermal energy) and exit the vessel
as side stream
9911. Gas stream 25C can then pass through a valve 800 where it becomes gas
stream 25D
and can then be directed to a desired location, such as, by joining it with
gas product stream
12B to create gas product stream 12C. Liquid stream 10L can be then directed
to a desired
location, such as, an inlet stream 10L for yet another heat exchanger
processing unit (not
shown). As will be understood, any desired number of heat exchanger processing
units may
be arranged in series relationship. Further, it will be understood that Lean
LNG stream 10E
may be directed to one or more heat exchanger processing units that are
themselves arranged
in parallel fashion. It will be further understood that the various streams
exiting the heat
exchangers and degassers could also be directed to other equipment
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combining/separating/collecting liquid LLNG and gas after the degassers, etc.
As such, there
is great versatility in the arrangement, configuration and number of heat
exchanger
processing units that may be employed. The LLNG is maintained in liquid foul'
as it
traverses through the exchanger(s) (where it is heated), and then after
passing through the
backpressure/level control valve, it may then vaporize where the liquid/vapour
mixture is
directed into the next degasser or a vessel or a collection of equipment, such
as a pipe header,
etc. When the liquid from the degasser is directed to the next heat exchanger,
this provides a
liquid stream feed to the heat exchanger which permits a more compact
exchanger resulting
in greater economy. The heat source for the heat exchangers can be air, as in
air exchangers,
or sea water, as in sea water exchangers, or other heat sources known in the
art.
[0075] Referring back to FIG. 1A, stream 10A may be directed out of valve
75 (via
outlet 78) as stream 10B to be recycled and introduced into the processing
column 50 via
processing column inlet(s) 58 for receiving stream 10B at various locations
along the height
of the column 50 in connection with valve(s) 17G. The processing column 50
receives, when
required in its operating mode, a cold Lean LNG (stream 10B) at a point in the
column
calculated for a particular combination of pressures and fluid compositions to
enhance its C2
Recovery or its C2 Rejection mode of operation.
[0076] Additionally, Lean LNG stream 10A could be diverted out of valve 75
via
outlet 79 (as stream 10C, 10D, with assistance of pump 74A as may be
necessary) back to
storage tank 20 to permit the Lean LNG product of this invention to be
recycled to storage as
part of a "roll over" control method. For example, it is contemplated
spreading a part of the
Lean LNG product 10A (as streams 10C, 10D) as a further and part product of
the Lean
LNG flash of product of the Lean LNG product of this invention which can be
recycled to
storage as part of a "roll over" control method. In another embodiment, it is
contemplated
spreading a processed or cooled LNG product 10A, 10C within or above a stored
quantity of
LNG (such as is stored in tank 20) as part of a "roll over" control method via
one or more jets
or spargers (20B, 20C) within the tank 20. The sparged LNG product 10A, 10C
can be
introduced within (20B) or above (20C) a stored quantity of LNG (e.g., in tank
20 having
LNG level 20A and one or more jets/spargers 20B, 20C). Also, it is
contemplated sparging a
processed LNG product 10A, 10C, 10D comprising of vapor and/or liquid flash of
this
disclosed process, within or above a stored quantity of LNG in tank 20.
SUBSTITUTE SHEET (RULE 26)
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[0077] Additionally, referring again to receiving vessel 70, tail gas
stream 11 may be
directed from receiving vessel 70, via outlet 73 into a compressor 80 (via
compressor inlet
81) whereafter the compressed gas stream 12 emerges from compressor via outlet
82 and may
be directed to a desired location. The compressor has an energy stream 80A for
driving the
compressor 80.
[0078] In one embodiment (referring to FIG. 2A, FIG. 2B), stream 12 may be
directed into a heat exchanger CDX 90 via inlet 91 to cool stream 12. The Lean
LNG cooler
gas stream 12B (emerging from exchanger outlet 92) may be directed (as stream
12C) to be
merged along with stream 10A and delivered to a desired location, or may be
directed (as
stream 12D) to be merged with stream 10B for recycling to the processing
column 50.
Optionally, the heat exchanger 90 may utilize an external refrigeration option
14, such as via
coolant lines 14A, 14B to provide coolant.
[0079] In another embodiment, for example, and referring to FIG. 1B (which
illustrates detail area 1B from FIG. 1A), stream 12 may be directed through
valve 900 where
it becomes gas product stream 12A where it is directed to a desired location,
along with
potential other gas product streams 12B, 12C as described above.
[0080] Additionally, a cold LNG stream 13 (or other desired cold stream,
such as, a
lean oil extraction / absorption stream) may be introduced into the heat
exchanger 90 (via
inlet 94) and directed out of the heat exchanger (via outlet 93) as stream 15.
Stream 15 may
be diverted (as stream 15A) into the degasser 40 (via inlet 47) in connection
with suitable
valve 17B. Stream 15 may also be directed (as stream 15B) (in connection with
suitable
valve 17A) into processing column 50 via processing column inlet(s) 59 for
receiving stream
15B at various locations along the height of the column 50 (in association
with valve(s) not
shown). Although only one inlet 59 is shown, multiple inlets, at various
locations along the
length of the column could be employed to introduce stream 15B into the
column. Stream 13
can be a stream, e.g. but not limited to, C1-rich or a C2-rich or a C3-rich or
a C4-rich or a
rich LNG or a Lean LNG which can act as the cooling colder stream used to
condense any
vapors in stream 12 in the heat exchanger 90 to give a partially or fully
condensed stream
12B.
[0081] Stream 13 in another instances or embodiments, but not limited to,
can be a
what is teimed a "Lean Oil" absorber stream that can be used to cool stream 12
in the Heat
exchanger 90 or in another instance, bypass the exchanger 90 as stream 15,
which in turn can
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be another feed stream to the processing column as stream 15A or stream 15B to
affect
extraction of less volatile components from the VLNG/RLNG or be used to
control
separation behavior of products and operation of the processing column 50.
Effectively it is
an optional part of the inventive disclosure and embodiment, that is used to
additionally or
further control hydrocarbon mixture separation behaviors in the column similar
to where the
column bottoms (stream 6A or 6A-1) are used to alter feed composition to the
column or
separately directly fed to the column via various location connections in the
column one
instance of result as shown and demonstrated in Table 6.
[0082] An external refrigeration option 14 is provided in which may
comprise any
other material stream of choice which is a refrigerating/cooling stream (14A,
14B) that cools
the stream 12 in the exchanger 90 producing a condensed fully liquid or
partially liquid
stream 12B.
[0083] For a better understanding of the operation of the present
invention, reference
is made to the following Tables in connection with process flow diagrams
illustrated in the
drawings,
SUBSTITUTE SHEET (RULE 26)
o
o
,-i
h TABLE 1 - FIG 1 TABLE 2 -
FIG 2 TABLE 3 - FIG 3
in
,-i
,-i Vapour Fraction 0.00 0.00 0.00 . Vapour Fraction
0.00 0.00 0.00 Vapour Fraction 0.00 0.00 0.00
el Temperature [F] -260.00 -126.79 119.04 .
Temperature [F] -260.00 -124.07 146.76 Temperature [F] -
260.00 -123.37 143.45
ci)
C.)
a, C1 0.98 1.00 0.01 C1 0.53
0.97 0.01 C1 0.39 0.96 0.01
C2 0.01 0.00 0.50 C2 0.22
0.02 0.46 C2 0.32 0.03 0.51
C3 0.01 0.00 0.29 C3 0.14
0.00 0.29 C3 0.12 0.00 0.19
iC4 0.00 0.00 0.05 iC4 0.03
0.00 0.06 iC4 0.04 0.00 0.07
nC4 0.00 0.00 0.05 nC4 0.05
0.00 0.10 nC4 0.08 0.00 0.13 r.D.
C5's 0.00 0.00 0.02 C5's 0.01
0.00 0.03 C5's 0.02 0.00 0.03 CN1
C6+ 0.00 0.00 0.03 C6+ 0.02
0.00 0.04 C6+ 0.03 0.00 0.04 11.1
ko
-I
H VOLFI ow (Ethane) VOLFI ow (Ethane)
VOLFI ow (Ethane) D
Lc)1
[barrel/day] 6356.35 1197.50 5164.17
[barrel/day] 142556.61 8138.67 134475.94
[barrel/day] 202278.20 7859.77 194437.13 Ct
o
col VOLFI ow (Propane) VOLFI ow (Propane)
VOLFI ow (Propane) I-
H
11 [barrel/day] 3337.23 213.83
3124.46 . [barrel/day] 89321.06 1059.51 88268.67 [barrel/day]
75459.14 589.61 74870.88
.1.
o 1.1.1
C \ I cz!
1
lO 7-i
Cn
C \ I
in
11.1
co TABLE 4 - FIG 4 TABLE 5 - FIG 5 -
FAILED CASE TABLE 6 - FIG 6 - READJUSTED CASE
H
CO Name 0-RICH LNG 0-LEAN LNG
O-NGL Name 0-RICH LNG 0-LEAN LNG O-NGL Name
0-RICH LNG 0-LEAN LNG O-NGL D
C \ I
0 Vapour Fraction 0.00 0.00 0.00 Vapour Fraction
0.00 0.00 0.00 Vapour Fraction 0.00 0.00 0.00
P
4
Cn
o Temperature [F] -260.00 -
97.33 162.21 Temperature [F] -260.00 Temperature [F] -
260.00 -118.37 121.74
Ca
a Pressure [psig]
,-, 10.00 550.00 555.00 Pressure
[psig] 10.00 550.00 555.00 Pressure [psig] 10.00
600.00 605.00 D
= Molar Fl ow [I bmol e/hr] 109804.69
60407.94 53482.33 Molar Flow [I bmol e/hr] 109804.69 Molar Flow [I
bmole/hr] 109804.69 98516.48 11333.33 Cn
CI
C1 0.39 0.70 0.01 C1 0.87
C1 0.87 0.97 0.01
C2 0.32 0.26 0.42 C2 0.09
C2 0.09 0.03 0.64
cle, C3 0.12 0.03 0.21 C3 0.03
C3 0.03 0.00 0.26
c
iC4 0.04 0.01 0.08 iC4 0.01 iC4
0.01 0.00 0.09
= nC4 0.08 0.01 0.15 nC4 0.00
nC4 0.00 0.00 0.00
cA Cp2
el C5's 0.02 0.00 0.04 . C5's 0.00
C5's 0.00 0.00 0.00
h
.7r C6+ 0.03 0.00 0.05 . C6+ 0.00
C6+ 0.00 0.00 0.00
in
o VOLFI ow (Ethane)
VOLFI ow (Ethane) VOLFI ow (Ethane)
el
[barrel/day] 202278.20 89593.20
131357.21 . [barrel/day] 56796.57 [barrel/day] 56796.57
15135.38 41754.11
el op VOLFI ow (Propane) VOLFI ow (Propane)
VOLFI ow (Propane)
0 0
0 [barrel/day] 75459.14 11210.88 67118.70 [barrel/day]
19270.43 [barrel/day] 19270.43 1585.35 17709.47
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[0085] Referring to the top row of each Table, the Table number and
Figure number
are referenced, and the Stream labels on the second row are shown. The 3
streams shown in
this Summary of Tables above are the Feed Stream ("0-RICH LNG" also referred
to herein as
"RICH LNG") and Lean LNG Product Stream ("0-LEAN LNG" or "LEAN LNG") and the
NGL Product stream ("O-NGL" or "NGL") results.
[0086] Key: (Description = Stream Name) ::
[0087] C2+ rich feed Rich LNG = 0-RICH-LNG (Liquid)
[0088] C1 rich lean LNG product = 0-LEAN LNG
[0089] C2+ rich NGL product = O-NGL
[0090] As seen from the analysis of stream "0-RICH LNG" of Table 1
through to
Table 6, the invention has been designed to handle C2 compositions of LNG of
from about
+/- 1% stored at about atmospheric and more particularly approximately 10 PSIG
and -260 F
to a C2+ content range that extends even beyond 32+% (shown) and (not shown)
beyond
even 52% Mol of C2 stored at 10 PSIG and -232 F.
[0091] DETAILED TABLES for all relevant streams:
[0092] As a means of the explanation of the Figures, Tables 1A through 6A
are
provided giving more detailed data description of the parameters for the
design and operation
of the process plant. It will be apparent to one skilled in the art having the
benefit of the
present disclosure, that the present invention could be practiced by following
the present
disclosure of the diagrams/Figures and the accompanying data Tables. The
current disclosure
is indicative of reasonable assumptions typically made by those skilled in the
art, including
rounding of the data, ambient conditions and heat losses not accounted and not
shown but
contemplated where required.
[0093] Key:
[0094] The rows showing label "Name" is for Stream Labels in that row and
which
are directly referenced to stream data from the FIG. 1A process flow diagram.
[0095] First row indicates the Table Number.
SUBSTITUTE SHEET (RULE 26)
,--1
t-- TABLE 1A - FIG 1
in ,
V ....... ,=
,
r
Name 0-RICH LNG 0-LEAN LNG
O-NGL 1 1A 2 3 4 5
,--1
,--1
Vapour Fraction 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 1.0000
el
ci)
Temperature [F] -260.0 -126.8 119.0 -
260.0 -260.0 -162.4 -162.8 -162.8 -162.8
E=1 Pressure [psig] 10.0 550.0 555.0
700.0 700.0 693.0 560.0 555.0 555.0
c.)
00 Molar Flow [lbmole/hr] 109,804.7 108,088.0
1,784.4 109,804.7 109,804.7 109,804.7 109,804.7 109,804.7
-
C1 0.9800 0.9960 0.0081
0.9800 0.9800 0.9800 0.9800 0.9800 0.9998
C2 0.0100 0.0019 0.4999
0.0100 0.0100 0.0100 0.0100 0.0100 0.0002
C3 0.0051 0.0003 0.2938
0.0051 0.0051 0.0051 0.0051 0.0051 0.0000 csi
iC4 0.0008 0.0000 0.0477
0.0008 0.0008 0.0008 0.0008 0.0008 0.0000 cNi
LU
ko nC4 0.0009 0.0000 0.0541
0.0009 0.0009 0.0009 0.0009 0.0009 .. 0.0000 -I
H
D
1
in C5's 0.0003 0.0000 0.0182
0.0003 0.0003 0.0003 0.0003 0.0003 0.0000 Ce
0
' C6+ 0.0005 0.0000 0.0305
0.0005 0.0005 0.0005 0.0005 0.0005 0.0000 I-
co
H
LU
0 VOLFlow (Ethane) [ ba rrel/day] 6,356.35 1,197.50
5,164.17 6,356.35 6,356.35 6 356 35 6,356.35 6,356.35 -
LU
,=
li) C7:1 VOLFlow (Propane) [barrel/day] 3,337.23 213.83
3,124.46 3,337.23 3,337.23 3,337.23 3,337.23 3,337.23 -
1
u)
C \ I r r r r
r 3 3'
co
LU
co Name 6 6A 7 8
9 10 10B 11 12 I-
H
C Vapour Fraction 0.0000 0.0000 1.0000
1.0000 0.0000 0.0000 0.0000 1.0000 <empty> D
0
Temperature [F] 119.0 119.0 -125.0 -
125.0 -127.1 -127.1 -126.8 -127.1 <empty> P
4
U)
c.) Pressure [psig] 555.0 555.0 550.0
550.0 543.0 543.0 550.0 543.0 555.0 co
Molar Flow [lbmole/hr] 1,784.4 -
120,030.1 120,097.8 120,097.8 120,097.8 12,009.8 - -
D
u)
C1 0.0081 0.0081 0.9961
0.9960 0.9960 0.9960 0.9960 0.9986 0.9986
74 C2 0.4999 0.5002 0.0019
0.0019 0.0019 0.0019 0.0019 0.0006 0.0006
W
1-4 C3 0.2938 0.2937 0.0003
0.0003 0.0003 0.0003 0.0003 0.0000 0.0000
Pat
.el iC4 0.0477 0.0477 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
cr E-1
el nC4 0.0541 0.0540 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
t--
.re
in C5's 0.0182 0.0182 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
el C6+ 0.0305 0.0305 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
,-1
VOLFlow (Ethane) [ ba rrel/day] 5,164.17 -
1,325.24 1,330.55 1,330.55 1,330.55 133.06 - -
O c:,
c) VOLFlow (Propane) [barrel/day] 3,124.46 -
236.53 237.59 237.59 237.59 23.76 - -
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[0097] TABLE 1A
(in conjunction with the process flow diagram of FIG. 1A) shows
the processing of LNG with 1% C2 in an Ethane Recovery mode, resulting in a
recovery of
81% of C2 and 94% of C3, with the rest of the component recoveries reflected
in Tables 1
and 1A. Regarding the data in TABLE 1A, (and in reference to FIG. 1A) it is
noted that
stream 2 is maintained as a liquid with minimal reflux (stream 10B, with <
than 1% C2 - as
same as C2 in Lean LNG) and 0 bottoms recycle (stream 6A). No
compression/recompression is required for tail stream 11 which can be tied
into a gasification
system and pipeline much more economically at a higher pressure with just some
addition of
heat and compression to even higher pressure if desired. For example,
referring to streams
1A, 2 and 3, the vapour fraction is zero thereby indicating that there is no
vaporization of the
LNG stream. Stream 5 reflects a "default" stream/pipe for vapor to leave if
any gas degasses
¨ so always a Vapour Fraction of "1" - a simulation stream vapor and liquid
from any vessel.
However, there is no "flow quantity" in stream 5 ¨ Molar Flow ¨ the dash (¨)
means zero.
SUBSTITUTE SHEET (RULE 26)
,--1
t--- TABLE 2A -FIG 2
...............................................................................
.. r .......
P
...............................................................................
..............................
2
?.
Name 0-RICH LNG 0-LEAN LNG
O-NGL 1 1A 3 .. 4 .. 5
,--1
,--1
Vapour Fraction 0.0000 0.0000 .. 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 1.0000
el
ci)
Temperature [F] -260.0 -124.1 146.8 -
260.0 -260.0 -187.2 -186.4 -186.4 -186.4
E=1 Pressure [psig] 10.0 550.0 555.0 700.0
700.0 693.0 560.0 555.0 555.0
c.)
00 Molar Flow [Ibmole/hr] 109,804.7 59,224.0
50,642.2 109,804.7 109,804.7 109,804.7 109,804.7
109,804.7 -
Cl 0.5279 0.9723 0.0084
0.5279 0.5279 0.5279 0.5279 0.5279 0.5278
C2 0.2243 0.0237 0.4587
0.2243 0.2243 0.2243 0.2243 0.2243 0.2243
C3 0.1365 0.0030 0.2925
0.1365 0.1365 0.1365 0.1365 0.1365 0.1365 csi
iC4 0.0265 0.0002 0.0573
0.0265 0.0265 0.0265 0.0265 0.0265 0.0265 cNi
LU
ko nC4 0.0475 0.0002 0.1028
0.0475 0.0475 0.0475 0.0475 ........ 0.0475 0.0475 -I
H
D
1
in C5's 0.0122 0.0000 0.0265
0.0122 0.0122 0.0122 0.0122 0.0122 0.0122 Ce
0
1
co C6+ 0.0166 0.0000 0.0359
0.0166 0.0166 0.0166 0.0166 0.0166 0.0166 I-
H
LU
0 VOLFlow (Ethane) [barrel/day] 142,556.61 8,138.67
134,475.94 142,556.61 142,556.61 142,556.61 142,556.61
142,556.61LU
-
C \ I
M
1
li) C'll VOLFlow (Propane) pa ne) [ ba rrel/day] 89,321.06
1,059.51 .. 88,268.67 .. 89,321.06 .. 89,321.06
Ccc\ ooI ,
89,321.06 89,321.06 r
89,321.06
-
Name 6 6A 7 8
9 10 10B 11 12
uLU)
I-
H
C Vapour Fraction 0.0000 0.0000 1.0000
1.0000 0.0000 0.0000 0.0000 1.0000 <empty> D
0
Temperature [F] 146.8 146.8 -102.9 -
102.8 -124.3 -124.3 -124.1 -124.3 <empty> P
4
U)
o Pressure [psig] 555.0 555.0 550.0 550.0
543.0 543.0 550.0 543.0 555.0 03
U)
Molar Flow [Ibmole/hr] 50,642.2 - -
65,743.0 65,804.4 65,804.4 65,804.4 6,580.4 -
D
C1 0.0084 0.0084 0.9725
0.9723 0.9723 0.9723 0.9723 0.9930 0.9930
C2 0.4587 0.4583 0.0236
0.0237 0.0237 0.0237 0.0237 0.0062 0.0062
W
1-4 C3 0.2925 0.2927 0.0030
0.0030 0.0030 0.0030 0.0030 0.0003 0.0003
Pat
-el iC4 0.0573 0.0573 0.0002
0.0002 0.0002 0.0002 0.0002 0.0000 0.0000
cr E-1
el nC4 0.1028 0.1029 0.0002
0.0002 0.0002 0.0002 0.0002 0.0000 0.0000
t--
.rr C5's 0.0265 0.0265 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
in
el C6+ 0.0359 0.0359 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
,-1
-
VOLFlow (Ethane) [barrel/day] 134,475.94 8,984.97
9,042.97 9,042.97 9,042.97 904.30 -
-
0 c:,
c) VOLFlow (Propane) pa ne) [ ba rrel/day] 88,268.67 -
1,170.11 1,177.23 1,177.23 1,177.23 117.72 -
-
CA 02818326 2013-05-16
WO 2012/054729
PCT/US2011/057106
-24-
[0099] TABLE 2A
(in conjunction with the process flow diagram of FIG. 1A) shows
the processing of LNG with 22% C2 in an Ethane Recovery mode, resulting in a
recovery of
94% of C2 and 99% of C3, with the rest of the component recoveries reflected
in Tables 2
and 2A. Regarding the data in TABLE 2A (and in reference to FIG. 1A), it is
noted that
steam 2 is maintained as liquid with minimal reflux (stream 10B, with > than
2% C2 - as
same as C2 in Lean LNG) and 0 bottoms recycle (stream 6A). No
compression/recompression is required for stream 11 ¨ which can be tied into a
gasification
system and pipeline much more economically at a higher pressure with just some
addition of
heat and compression to even higher pressure if desired.
SUBSTITUTE SHEET (RULE 26)
,--1
t--- TABLE 3A - FIG 3
en V
................. V ...... , r ...... r .......
Name 0-RICH LNG 0-LEAN LNG
O-NGL 1 1A 2 3 4 5
,--1
,--1
Vapour Fraction 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 1.0000
el
cr)
Temperature [F] -260.0 -123.4 143.4 -
260.0 -260.0 -206.0 -205.1 -205.0 -205.0
E=1 Pressure [psig] 10.0 550.0 555.0
700.0 700.0 693.0 560.0 555.0 555.0
c.)
00 Molar Flow [lbmole/hr] 109,804.7 43,372.6
66,450.9 109,804.7 109,804.7 109,804.7 109,804.7 109,804.7
-
Cl 0.3861 0.9649 0.0085
0.3861 0.3861 0.3861 0.3861 0.3861 0.3861
C2 0.3182 0.0313 0.5055
0.3182 0.3182 0.3182 0.3182 0.3182 0.3182
C3 0.1153 0.0023 0.1891
0.1153 0.1153 0.1153 0.1153 0.1153 0.1153 csi
cNi
iC4 0.0430 0.0003 0.0708
0.0430 0.0430 0.0430 0.0430 0.0430 0.0430 LU
ko nC4 0.0770 0.0003 .. 0.1270
0.0770 0.0770 0.0770 0.0770 0.0770 0.0770
H
D
1
in C5's 0.0198 0.0000 0.0327
0.0198 0.0198 0.0198 0.0198 0.0198 0.0198 Ce
0
1 C6+ 0.0268 0.0000 0.0443
0.0268 0.0268 0.0268 0.0268 0.0268 0.0268 I-
rn
H
LU
0 VOLFlow (Ethane) [ ba rrel/day] 202,278.20 7,859.77
194,437.13 202278.20 202,278.20 202,278.20 202,278.20
202,278.20 - LU
C \ I
VOLFlow (Propane) pa ne) [ ba rrel/day] 75,459.14 589.61 74,870.88
75,459.14 75,459.14 75,459.14 75,459.14 75,459.14 -
u)
C \ I r r r r
r r r
rn
LU
CO Name 6 6A 7 8
9 10 10B 11 12 I-
H
C Vapour Fraction 0.0000 0.0000
1.0000 1.0000 0.0000 0.0000 ... 0.0000 1.0000 <empty> D
C \ I
I-
0
Temperature [F] 143.4 143.6 -98.3 -
98.2 -123.6 -123.6 -123.4 -123.6 <e mpty> P
4
CO
o Pressure [psig] 555.0 555.0 550.0
550.0 543.0 543.0 550.0 543.0 555.0 03
Molar Flow [lbmole/hr] 66,450.9 -
48,172.9 48,191.8 48,191.8 48,191.8 4,819.2 - -
U9
'el
en C1 0.0085 0.0085 0.9649
0.9649 0.9649 0.9649 0.9649 0.9906 0.9906
6T4
1-4 C2 0.5055 0.5049 0.0312
0.0313 0.0313 0.0313 0.0313 0.0079 0.0079
;c1 C3 0.1891 0.1893 0.0023
0.0023 0.0023 0.0023 0.0023 0.0002 0.0002
'el
E-1 iC4 0.0708 0.0709 0.0003
0.0003 0.0003 0.0003 0.0003 0.0000 0.0000
cr
el nC4 0.1270 0.1271 0.0003
0.0003 0.0003 0.0003 0.0003 0.0000 0.0000
h
.re C5's 0.0327 0.0327 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
en
el C6+ 0.0443 0.0444 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
,-1 47:7
VOLFlow (Ethane) [ ba rrel/day] 194,437.13 -
8,714.37 8,733.08 8,733.08 8,733.08 873.31 - -
O c:,
c) VOLFlow (Propane) pa ne) [ ba rrel/day] 74,870.88 -
653.77 655.12 655.12 655.12 65.51 - -
CA 02818326 2013-05-16
WO 2012/054729
PCT/US2011/057106
-26-
[00101] TABLE 3A
(in conjunction with the process flow diagram of FIG. 1A) shows
the processing of LNG with 32% C2 in an Ethane Recovery mode, resulting in a
recovery of
96% of C2 and 99% of C3, with the rest of the component recoveries reflected
in Tables 3
and 3A. Regarding the data in TABLE 3A (and in reference to FIG. 1A), it is
noted that
stream 2 is maintained as a liquid with minimal reflux (stream 10B, with >
than 3% C2 - as
same as C2 in Lean LNG) and 0 bottoms recycle (stream 6A). No
compression/recompression required for stream 11 ¨ which can be tied into a
gasification
system and pipeline much more economically at a higher pressure with just some
addition of
heat and compression to even higher pressure if desired.
SUBSTITUTE SHEET (RULE 26)
,-1
t--- TABLE 4A - FIG 4
in
Name 0-RICH LNG 0-LEAN LNG
O-NGL 1 1A 2 3 4 5
,-1
,-1
Vapour Fraction 0.0000 0.0000 0.0001
0.0000 0.0000 0.0000 0.0053 0.0000 1.0000
el
ci)
Temperature [F] -260.0 -97.3 162.2 -
260.0 -260.0 -45.0 -45.3 30.0 30.0
E=1 Pressure [psig] 10.0 550.0 555.0 700.0
700.0 693.0 560.0 555.0 555.0
c.)
00 Molar Flow [Ibmole/hr] 109,804.7 60,407.9
53,482.3 109,804.7 109,804.7 109,804.7 109,804.7
141,879.5 21,413.8
Cl 0.3861 0.6961 0.0086
0.3861 0.3861 0.3861 0.3861 0.2011 0.6692
C2 0.3182 0.2562 0.4243
0.3182 0.3182 0.3182 0.3182 0.3656 0.2697
C3 0.1153 0.0311 0.2106
0.1153 0.1153 0.1153 0.1153 0.1626 0.0397 csi
iC4 0.0430 0.0053 0.0840
0.0430 0.0430 0.0430 0.0430 0.0638 0.0072 cNi
LU
ko nC4 0.0770 0.0069 0.1526
0.0770 0.0770 0.0770 0.0770 0.1156 .. 0.0095 -I
H
D
1
Lc) C5's 0.0198 0.0008 0.0400
0.0198 0.0198 0.0198 0.0198 0.0302 0.0012 Ce
0
1
co C6+ 0.0268 0.0008 0.0545
0.0268 0.0268 0.0268 0.0268 0.0411 0.0012 I-
H
LU
0 VOLFlow (Ethane) [barrel/day] 202,278.20 89,593.20
131,357.21 202,278.20 202,278.20 202,278.20 202,278.20
300,230.85 33,437.23 LU
C \ I
li) C'll VOLFlow (Propane) [ ba rrel/da y] 75,459.14 11,210.88
67,118.70 75,459.14 75,459.14 75,459.14 75,459.14
137,505.77 5,070.95 u)
C \ I
coLU
co Name 6 6A 7 8
9 10 10B 11 12 I-
H
C Vapour Fraction 0.0001 0.0000 1.0000
1.0000 0.0000 0.0000 0.0000 1.0000 <empty> D
0
Temperature [F] 162.2 162.2 9.1 16.7
-97.4 -97.4 -97.3 -97.4 <empty> P
4
V)
o Pressure [psig] 555.0 555.0 550.0 550.0
543.0 543.0 550.0 543.0 555.0 03
Molar Flow [Ibmole/hr] 106,964.7 53,488.6
96,600.6 100,679.9 100,679.9 100,679.9 40, -
272.0 D
-
V)
C1 0.0086 0.0086 0.7243
0.6961 0.6961 0.6961 0.6961 0.9445 0.9445
C2 0.4243 0.4243 0.2337
0.2562 0.2562 0.2562 0.2562 0.0513 0.0513
W
1-4 C3 0.2106 0.2106 0.0275
0.0311 0.0311 0.0311 0.0311 0.0015 0.0015
Pat
-el iC4 0.0840 0.0840 0.0045
0.0053 0.0053 0.0053 0.0053 0.0001 0.0001
cr E-1
el nC4 0.1526 0.1526 0.0059
0.0069 0.0069 0.0069 0.0069 0.0001 0.0001
t--
.re C5's 0.0400 0.0400 0.0007
0.0008 0.0008 0.0008 0.0008 0.0000 0.0000
in
el C6+ 0.0545 0.0545 0.0007
0.0008 0.0008 0.0008 0.0008 0.0000 0.0000
,-1 e7
VOLFlow (Ethane) [barrel/day] 262,714.43 131,389.87
130,682.44 149,321.99 149,321.99 149,321.99 59,728.80
-
el
-
0 c:,
c) VOLFlow (Propane) [ ba rrel/day] 134,237.40 67,117.57
15,813.24 18,684.80 18,684.80 18,684.80 7,473.92 - -
CA 02818326 2013-05-16
WO 2012/054729
PCT/US2011/057106
-28-
[00103] TABLE 4A (in conjunction with the process flow diagram of FIG. 1A)
shows
the processing of LNG with 32% C2 in an Ethane Controlled Rejection mode,
resulting in a
recovery of 65% of C2 and 89% of C3, with the rest of the component recoveries
reflected
Tables 4 and 4A. Regarding the data in TABLE 4A (and in reference to FIG. 1A),
it is noted
that stream 2 is maintained as a liquid with minimal reflux (stream 10B, with
> than 25% C2
- as same as C2 in Lean LNG) and a particular bottoms recycle (stream 6A). No
compression/recompression required for stream 11 ¨ which can be tied into a
gasification
system and pipeline much more economically at a higher pressure with just some
addition of
heat and compression to even higher pressure if desired. TABLE 4A reflects the
addition of a
recycle stream 6A resulting in a changing of enthalpy/composition. This
results in some
vapor "quantity" that flows out as stream 5 (which is a vapor stream by
default from a
"separator/vessel" in simulations and is always Vapour Fraction and so a "1"
and the other
side Stream 4 by default is always a liquid = "0" Vapour Fraction.
SUBSTITUTE SHEET (RULE 26)
v:.
o
,-.
r--- TABLE 5A- FIG 5
in
Name 0-RICH LNG 0-LEAN LNG
O-NGL 1 1A 2 3 4 5
,--1
,--1
Vapour Fraction 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.1305 0.0000 1.0000
eg
ci)
Temperature [F] -260.0 -124.1 111.3 -
260.0 -260.0 -102.0 -111.4 -97.7 -97.7
E=. Pressure [psig] 10.0 550.0 555.0 700.0
700.0 693.0 560.0 555.0 555.0
c.)
Po Molar Flow [lbmole/hr] 109,804.7
109,804.7
Cl 0.8710
0.8710
C2 0.0894
0.0894
C3 0.0294
0.0294 cli
cNi
iC4 0.0100
0.0100 L.0
ko nC4 -
- -I
H
D
1
in C5's -
- Ce
o
1 - C6+
- I-
co
H
LU
o VOLFlow (Ethane) [barrel/day]
56,796.57 56,796.57 LU
C \ I
01
1
VOLFlow (Propane) [barrel/day] 19,270.43
19,270.43 u)
C \ I
coLU
m Name 6 6A 7 8
9 10 1013 11 12
H
I-
C Vapour Fraction 0.0000 0.0000 ..
1.0000 1.0000 0.0000 ...... 0.0000 0.0000 1.0000 <empty>
D
C \ I
l-
o
Temperature [F] 111.3 111.2 -108.8 -
108.6 -124.3 -124.3 -124.1 -124.3 <empty> P
4
CO
o Pressure [psig] 555.0 555.0
550.0 550.0 543.0 543.0 550.0 543.0 555.0 CO
D
Molar Flow [lbmole/hr]
(i)
C1
C2
W
1-4 C3
Pat
-el iC4
cr E-1
el nC4
r---
7e C5's
in
C6+
,-1
,-1 ;17
el c) VOLFlow (Ethane) [barrel/day]
i-i
0c:,
co VOLFlow (Propane) [barrel/day]
CA 02818326 2013-05-16
WO 2012/054729
PCT/US2011/057106
-30-
[00105] TABLE 5A (in conjunction with the process flow diagram of FIG. IA)
shows
the processing of LNG with 8.9% C2 in the same operating mode as TABLE 4/4A.
It fails (as
seen in TABLE 5/5A) and cannot perfoim unless the inventive design changes in
the
operating mode are made as in TABLE 6/6A. With respect to the data in TABLE 5A
and 6A
and in reference to the figures ¨ it shows that for one of various pressure
and temperature for
stream 2, when permitted or allowed to vaporize in stream 2 TABLE 5A, the
system fails and
when maintained as a liquid as in stream 2 of TABLE 6A, the system along with
all the other
parameters performs. TABLE 5A demonstrates that control of column pressure
drives the
feasibility of the process as well. TABLE 5A demonstrates the effect of
changing the column
pressure slightly from 605 psig to 555 psig. The failure translates down to
the exchanger
which goes into a "temperature cross" or an impractical or uneconomic
exchanger design.
Stream 2 is liquid until let down in pressure at the valve down to stream 3 (
exchanger
pressure Stream 2 was 693 psig and valve let it down as stream 3 to 560 psig ¨
partly
vaporizing).
SUBSTITUTE SHEET (RULE 26)
o
o
,--1
h TABLE 6A - FIG 6
In
0
,--1 Name 0-RICH LNG 0-LEAN LNG
O-NGL 1 1A 2 3 4 5
,--1
= Vapour Fraction 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 1.0000
el
ci)
Temperature [F] -260.0 -118.4 121.7 -
260.0 -260.0 -114.8 -115.6 -96.3 -96.3
-1.- Pressure [psig] 10.0 600.0 605.0
700.0 700.0 693.0 605.0 605.0 605.0
c.)
a, Molar Flow [lbmole/hr] 109,804.7 98,516.5
11,332.1 109,804.7 109,804.7 109,804.7 109,804.7 100,028.8
21,137.1
C1 0.8710 0.9702
0.0081 0.8710 0.8710 0.8710 0.8710 0.7543 0.9594
02 0.0894 0.0265 0.6364
0.0894 0.0894 0.0894 0.0894 0.1628 0.0359
03 0.0294 0.0027 0.2622
0.0294 0.0294 0.0294 0.0294 0.0613 0.0037 F,
iC4 0.0100 0.0004 0.0933
0.0100 0.0100 0.0100 0.0100 0.0214 0.0005 c4
Lu
nC4 0.0000 0.0000
- - 0.0000 .. 0.0000 _1
- -
-
H
D
J., C5's 0.0000 0.0000
- - 0.0000 0.0000 re
- -
-
0
i
ro C6+ 0.0000 0.0000
- - 0.0000 0.0000 1-
- -
-
H
LU
0 VOLFlow (Ethane) [barrel/day] 56,796.57 15,135.38
41,748.37 56,796.57 56,796.57 56,796.57 56,796.57
94,285.31 4,394.97 LU
lf) Cr) VOLFlow (Propane) [barrel/da! 19,270.43 1,585.35
17,707.62 19,270.43 19,270.43 19,270.43 19,270.43
36,538.92 467.90 (0
C \I
ro
LU
co Name 6 6A 7 8
9 10 10B 11 12 I-
H
C Vapour Fraction 0.0000 0.0000 1.0000
1.0000 0.0000 0.0000 0.0000 1.0000 <empty> D
C \I
I-
0
Temperature [F] 121.7 121.7 -104.0 -
104.0 -118.6 -118.6 -118.4 -118.6 <empty> I=
4
Cf)
o Pressure [psig] 605.0
605.0 600.0 600.0 593.0 593.0 600.0 593.0 605.0 co
Molar Flow [lbmole/hr] 22,664.3 11,361.2 164,179.2
164,194.1 164,194.1 164,194.1 65,677.7 - D
Cf)
01 0.0081 0.0081 0.9701
0.9702 0.9702 0.9702 0.9702 0.9904 0.9904
-t
02 0.6364 0.6368 0.0266
0.0265 0.0265 0.0265 0.0265 0.0088 0.0088
w
W C3 0.2622 0.2620
0.0027 0.0027 0.0027 0.0027 0.0027 0.0004 0.0004
=
</ iC4 0.0933 0.0931 0.0004
0.0004 0.0004 0.0004 0.0004 0.0000 0.0000
el nC4 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
h
,r C5's 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
In
0
el
06+ 0.0000 0.0000 0.0000
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
,-,
VOLFlow (Ethane) [barrel/day] 83,496.74 41,883.71
25,273.80 25,225.64 25,225.64 25,225.64 10,090.25
el
- -
0 0
c) VOLFlow (Propane) [barrel/dal 35,415.24 17,736.39
2,648.48 2,642.25 2,642.25 2,642.25 1,056.90 - -
CA 02818326 2013-05-16
WO 2012/054729
PCT/US2011/057106
-32-
[00107] TABLE 6A (in conjunction with the process flow diagram of FIG. 1A)
shows
It shows the processing of LNG with 8.9% C2 in an Ethane Controlled Rejection
mode. With
respect to the data in TABLE 6A (and in reference to FIG. 1A), it is noted
that stream 2 is
maintained as a liquid with some reflux (stream 10B, with > than 2% C2 - as
same as C2 in
Lean LNG) and 0 bottoms recycle (stream 6A). No compression/recompression is
required
for stream 11 ¨ which can be tied into a gasification system and pipeline much
more
economically at a higher pressure with just some addition of heat and
compression to even
higher pressure if desired. One of the practical aspects of the invention is,
and it being one
subject of the invention, that the pressure has to be changed for the Column
as shown (FIG.
1A, TABLES 6/6A) for the system to be able to perfoint as expected, with other
choice of
parameters essentially kept the same, resulting in a recovery of 74% of C2 and
92% of C3,
with the rest of the component recoveries reflected in TABLES 6 and 6A. In
TABLE 6A,
although streams 4 and 5 are shown at pressure of 560 psig it is normally
boosted to whatever
pressure the column requires for its operation (which should have been 605psig
in this case
TABLE 6A ¨ going to processing column at 600psig). This is accomplished
"intrinsically"
in the simulation at the column, bit it could have been shown explicitly (as
nominally shown
for the TABLE 5A (555 psig going to column operating at 550 psig).
[00108] In the present invention, it is desired to have the pressure at
stream 2
sufficiently high so there is no need for boosting of pressure mentioned, as
at the valve there
is stream 2 @ 693psig and the valve will control the pressure drop from stream
3 pressure to
provide sufficient pressure for streams 4 & 5 ¨ nominally at 605 psig - to
supply flow to the
processing column at pressure 600psig.
[00109] As noted above, FIG. 2A is another flow diagram of a HYSYS
Simulation of a
LNG processing plant in accordance with the present invention. It illustrates
the employment
of additional processing options to those outlined in connection with FIG. 1A
and Tables 1-6.
Specifically, FIG. 2A adds processing options related to introduction of a
cold LNG or other
cold desired stream into stream 12 as described above. FIG. 2B provides an
enlarged view of
detailed area 2B of FIG. 2A (but has relevance also to the teachings of FIG.
1A). FIG. 2B
illustrates a detail of the processing column area and exemplary optional
connections thereon
for receiving various streams.
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[00110] The current process parameters adopted for this disclosure are
traditional
British units. Though not shown for this disclosure the use of SI units is
anticipated and
contemplated where required.
[00111] For convenience, the Tables reflect all Stream Flows, Temperatures,
Vapor
Fractions, Compositions (shown in Mole Fractions), and further including
volumetric flows
of the two key components, C2 and C3, which are used to evaluate Recovery
Performances.
The typical parameters of measurement are indicated within the Tables.
[00112] The present invention permits flexibility in optimizing the
processing column
operation in its modes of operation. In Ethane (C2) Rejection mode, the
processing column
is optimized to produce more methane C1 as an overhead stream (and less C2+ in
the bottom
stream). In Ethane Extraction mode, the processing column is optimized to
produce more
ethane+ (C2+) fractions from the bottoms stream. The use of reflux stream 10B
permits
reintroduction of methane rich liquid to the processing column as a reflux to
optimize the
processing column, to increase or manipulate the purity of the methane
overhead stream 7, or
to increase or control the C2+ fraction in the bottom stream 6. The present
invention permits
many points of flexibility and control for operational optimization. The
processing column
may be optimized (via, e.g., reflux, bottoms recycle) to shift the C2 fraction
in the column to
exit the column as part of the overhead stream (C2 rejection mode) or as part
of the bottoms
stream (C2 extraction mode). A typical NGL specification seeks to remove C1
content to
less than 1-10%. With the present system, the C1 content of the NGL stream can
be reduced
to less than 0.5%. System pressure plays a key role in this process as is
outlined in the
TABLES.
[00113] It is contemplated a process for separating less volatile compounds
from more
volatile compounds, more particularly hydrocarbons, for example the compounds
less volatile
than methane, in an LNG stream (herein called "Rich LNG").
[00114] It is contemplated to take an available normally low pressure
cryogenic feed
LNG and pump it to a higher pressure.
[00115] It is contemplated the higher pressure LNG stream 1A is pumped to a
LNG
Exchanger 30 to cross exchange heat with other stream(s) (e.g., stream 8).
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[00116] It is contemplated the cold stream is the Rich LNG (streams 1, 1A)
and the
warm stream is any of the streams from further downstream process(es), more
particularly in
this instance the overhead vapor stream 7 from the processing column 50.
[00117] It is contemplated the Rich LNG stream 1A is heated in the LNG
exchanger
30 while maintaining it in its liquid phase and state.
[00118] It is contemplated the LNG exchanger 30 to be of any particular
suitable
design or network of exchangers.
[00119] It is contemplated feeding the wathied Rich LNG stream 3 to a
degassing
vessel 40.
[00120] It is contemplated any vapor (stream 5) from the degasser vessel
40 be passed
to the processing column 50.
[00121] It is contemplated the liquid (stream 4) from the degasser 40 is
passed to an
upper section of the processing column 50.
[00122] It is contemplated a draw is taken from the processing column
bottoms or
bottom stream 6 is passed to the degasser (stream 6A) or a point in the column
(stream 6A-1).
[00123] It is contemplated the degasser 40 can be a liquid full vessel
where no vapor or
gas is evolved.
[00124] It is contemplated the degasser 40 can be of a simplest of device
to whatever is
dictated by the conditions.
[00125] It is completed the processing column 50 is effectively a reboiled
absorber
complete with the processing column 50 and a reboiler 60.
[00126] It is contemplated a stream (10B) is drawn from the Lean LNG and
returned to
the processing column 50.
[00127] It is contemplated the draws from the two draws, one from Lean LNG
and one
from the processing column bottom streams are available to work in tandem in
any amounts
and combinations at their inlet locations to the column.
[00128] It is contemplated the plant is operated in a way to manage the
Temperature
Approach within the LNG exchanger 30 so that the whole mangement can perform
practically, economically, and reasonably.
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[00129] It is contemplated the plant is operated in a way to manage the
LMTD (Log
Mean Temperature Difference) within the LNG exchanger 30 so that the whole
arrangement
can perfoini practically, economically, and reasonably.
[00130] It is contemplated controlling the processing column 50 pressure to
effectively
control the LNG exchanger 30 functions.
[00131] It is contemplated controlling the LNG exchanger 30 to function
practically by
controlling the processing column 50 pressure.
[00132] It is contemplated controlling the LNG exchanger 30 to function
practically by
controlling the processing column pressure and Rich LNG feed pressure.
[00133] It is contemplated controlling the LNG exchanger to function
practically by
controlling the processing column 50 pressure and/or Rich LNG feed pressure
and/or streams
to/from the column 50.
[00134] It is contemplated controlling the LNG exchanger to function
practically by
controlling the Rich LNG feed pressure.
[00135] It is contemplated controlling the LNG exchanger function and/or
product
stream compositions and/or separations of the components received in the
system, more
particularly components of feed stream of Rich LNG, practically by controlling
the
processing column pressure and/or Rich LNG feed pressure and/or streams and
their
properties and their inlet/outlet locations to/from the column.
[00136] It is contemplated controlling the processing column 50 pressure to
effectively
control the LNG exchanger operation functions and the overall function of the
whole
interdependent system.
[00137] It is contemplated managing the Rich LNG feed pressure to manage
the
various operations and operability of the system to perform.
[00138] It is contemplated controlling temperature of stream(s) to or from
the LNG
exchanger either directly or indirectly.
[00139] The HYSYS run data tables included here provide example description
of the
system behavior and operation. The HYSYS run data tables and figures, taken
together,
provide substantial description of the system to enable one to design a system
to operate in
practice.
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[00140] It is contemplated withdrawing the methane rich stream as the vapor
stream
from an upper section of the processing column 50.
[00141] It is contemplated sending the vapor stream 7 to the LNG exchanger
30 for
condensation.
[00142] It is contemplated the less volatile than methane liquid stream mix
is
withdrawn from the lower section of the processing column 50.
[00143] It is contemplated a part of the Lean LNG product as a further and
part
product of the Lean LNG flash of product of the Lean LNG product of this
invention can be
recycled to storage as part of a "roll over" control method.
[00144] It is contemplated introducing a technique and method for control
of storage
LNG "Roll Overs".
[00145] It is contemplated spreading a part of the Lean LNG product as a
further and
part product of the Lean LNG flash of product of the Lean LNG product of this
invention
which can be recycled to storage as part of a "roll over" control method.
[00146] It is contemplated spreading a processed or cooled LNG product
within or
above a stored quantity of LNG as part of a "roll over" control method via
jets or spargers.
[00147] It is contemplated sparging a processed product of this disclosed
process,
within or above a stored quantity of LNG as part of a "roll over" control
method via jets or
spargers.
[00148] It is contemplated sparging a processed LNG product comprising of
vapor
and/or liquid flash of this disclosed process, within or above a stored
quantity of LNG as part
of a "roll over" control method via jets or spargers.
[00149] In a more narrative form to elucidate further the separation of
Rich LNG into
methane rich Lean LNG and methane depleted NGL product the present disclosure
describes
a process in this example more particularly described for separating and
recovering ethane
and heavier hydrocarbons from LNG, and could be applied to streams of other
slates of
hydrocarbons or non-hydrocarbons or their mixes.
[00150] The present invention includes an option to include compression.
[00151] The present invention is also directed to a process that
practically eliminates
requirements for compression or recompression of gas prior to returning a
resulting product
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Lean LNG in its liquid form after processing the Rich LNG. In this embodiment,
the process
comprises the steps comprise of:
[00152] (a) Pumping (22) Rich LNG (0-RICH LNG) from anywhere near to
atmospheric pressure of for example about 10 PSIG pressure and about -260 F
up to 700
PSIG or more (stream 1) depending on composition and conditions of the feed
LNG to be
processed.
[00153] (b) Heating the LNG (stream 1A) in an LNG exchanger 30 in a manner
so that
it is still maintained in a liquid condition (stream 2), in cross exchange
with a warmer and
methane rich vapor stream (8) received back from a processing column 50,
particularly
overhead vapor stream (7) from further downstream of the LNG exchanger 30.
[00154] The warmed Rich LNG (2, 3) is channeled to degasser equipment 40
ranging
from a simple T Pipe device to a substantially liquid full vessel if desired.
[00155] (c) The degassed liquid (4) from the degasser 40 is flowed to a
point in the
upper section of the processing column 50.
[00156] (d) The processing column 50 operates at a pressure commensurate
but
selectable along with the full range of pressure of the pumped Rich LNG (1,
1A) from
atmospheric to 700 PSIG, and anticipated above if the equilibrium conditions
of the
processing column 50 fluids allows separation.
[00157] (e) The processing column 50 produces a methane rich overhead vapor
stream
(7) from the top section of the column and an essentially NGL stream (6, O-
NGL) from the
bottom section of the column 50.
[00158] (f) The processing column 50 receives when required in its
operating mode a
cold Lean LNG stream (10B) at a point in the column calculated for a
particular combination
of Pressures and fluid compositions to enhance its C2 Recovery or its C2
Rejection mode of
operation.
[00159] (g) The Rich LNG feed (3,4) is similarly calculated for its best
feed point in
the column 50, starting at the top section of the column, with any associated
gas (5) from the
degasser 40 similarly calculated (though as demonstrated in the HYSYS result
Tables
included here under noinial C2+ recovery mode no vaporization is anticipated
(Tables 1,2,3)
¨ except where a mode of operation such as in Ethane Rejection it may be
incidental to the
mode of operation (Tables 4, 6).
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[00160] (h) The processing column 50 is demonstrated here working
successfully with
theoretical trays.
[00161] (i) The column 50 has at least one contemplated reboiler 60
connected to the
column for providing heat to the column operation.
[00162] (j) At least one C2+ enriched liquid stream is drawn from the
column (6) and
heated in the reboiler prior to returning the boiled stream (6C) back to the
column 50.
[00163] (k) Optionally, a stream (6A) for recycle to the column 50 could be
drawn
from the reboiler 60 directly or the Product NGL Stream (6) and recycling that
stream to the
degasser 40 Or at a point in the column 50.
[00164] (1) A stream (6A) for recycle to the column could be drawn from the
NGL
Product stream (6) and thence leaving the column arrangements as a NGL product
stream (0-
NGL).
[00165] (m) The drawn stream (6A) is pumped and recycled to the degasser 40
or
directly at a point (not shown) calculated to fit the operation in the column
50 for a particular
operational condition.
[00166] (n) The column 50 can be made to operate at various pressures (see
streams 6
and 7) to meet the various interdependent parameters of the whole facility and
desired
perfoimance.
[00167] (o) The overhead methane rich vapor stream (7, 8) from the column
50 is
diverted to (8) the LNG exchanger 30 where it is condensed in cross exchange
of heat with
the cold Rich LNG feed (1A) where it ideally condenses up to 100% into Lean
LNG liquid
(9),
[00168] (p) The Lean LNG (9) is stored in a surge drum / receiving vessel
70, prior to
pumping it (10A, 0-LEAN LNG) to storage or Pipeline at the required pressure.
[00169] (q) A part of the Lean LNG (0-LEAN LNG) product of (p) (e.g.,
stream 10D)
as an option will be recycled to storage as part of a "roll over" control
method.
[00170] (r) This is the contemplated introduction of a technique and method
for control
of storage LNG "Roll Overs".
[00171] (s) From (q) it is contemplated spreading the part of the Lean LNG
product
(10D) as a further and part product of the Lean LNG flash of product of the
Lean LNG
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product of this invention which can be recycled to storage as part of a "roll
over" control
method.
[00172] (t) In the storage section 20 it is contemplated spreading a
processed or cooled
LNG product (10D) within or above a stored quantity of LNG as part of a "roll
over" control
method via jets or spargers (20C, 20B) relative to the LNG level 20A in the
storage tank 20.
[00173] (u) Further it is contemplated sparging a processed product of this
disclosed
process, within (via jet(s)/sparger(s) 20B) or above (via jet(s)/sparger(s)
20C) a stored
quantity of LNG having an LNG level 20A in the tank 20 as part of a "roll
over" control
method via jets or spargers.
[00174] (v) One option is also contemplated for sparging a processed LNG
product
comprising of vapor and/or liquid flash of this disclosed process, within or
above a stored
quantity of LNG as part of a "roll over" control method via jets or spargers.
[00175] The present invention provides advantages and features
distinguishing over
the systems of the prior art. For example, a flexible and streamlined NGL and
C2+
extraction/rejection process is disclosed and as embodied for processing
liquid, rich or virgin
(feed composition) LNG (hereinafter called RLNG or also called VLNG) and
essentially
producing one, a liquid lean LNG (hereinafter may be called LLNG) product and
second,
liquid NGL (hereinafter also referred to as NGL) product(s) without the need
of any of the
typical compression or expansion work equipment, which however can be an
optional part(s)
of other embodiments (which as shown in one embodiment here, as an optional
item (which
further as demonstrated here requires 0 (zero) compression power, meaning
there is no need
for one in the instances shown with 0 (zero) horsepower). The present
invention is a pressure
flexible - source/(feed composition) flexible - product flexible - operation
flexible -
equipment and capital wise economic system/method/process.
[00176] In this process, a liquid phase hydrocarbon stream such as in this
instance rich
LNG (termed RLNG, or until its composition is affected/changed, called virgin
LNG
(VLNG)) which is rich in heavier/(less volatile) hydrocarbon components than
such as in this
instance methane, is introduced into the system as liquid phase VLNG from
storage or
transport system/pipeline. The liquid phase VLNG is introduced either in
pressured state to
or thence pumped (in a VLNG Pump) up to a pressure that as part of the
inventive
device/method/process supports the whole system's various parts' operating
pressures as part
of this inventive system. The stream is then passed via a heat exchanger
(herein sometimes
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called LNG exchanger, essentially a single exchanger but optionally more or a
network of
exchangers) while keeping it all as part of this inventive process essentially
maintained in the
heat exchanger(s) in a liquid phase with the controlled applied pressures
(variable). The heat
exchange takes place by picking up heat from the processing column (further
downstream)
vapor overhead stream (OVHD). The stream is then directed to a back pressure
holding
valve/device/(or back pressure from a downstream equipment/column) to maintain
the stream
in liquid phase. The stream is then sent to a mixer/separator/vessel/device
(here called
degasser) wherein the VLNG can be degassed of inert or light(er) components
such as
hydrogen, nitrogen, H2S, CO2, etc., but not limited to and thereafter, the gas
stream is
connected up to the processing column as gas/vapor inlet to the column. The
gas stream can
also be mixed with other optional streams.
[00177] Optionally (essentially depending on the mode of operation of the
flexible
system presented), a composition and enthalpy change can be effected to the
VLNG via the
degasser by optionally mixing with another stream which changes the
state/composition of
the feed VLNG prior to feeding (FEED) it to the processing/fractionation
column. The
stream is then directed to a column (wherein the vapor/liquid streams from the
degasser can
be connected at any number(s) of optimal feed locations on the fractionation
column either as
VLNG feed or changed composition feed stream or vapor and liquid streams.
Pumping could
be added where needed to pump the feed liquid to the processing column.
[00178] The present disclosure teaches pumping the RLNG from storage
temperature
and pressure to any particular pressure up to (and beyond if required) any
process mixture
thermodynamic critical pressure required in the column.
[00179] No stream division is contemplated in the present disclosure, as
taught in the
prior art, where of splitting of RLNG is contemplated for reflux purpose to
column either
from upstream of exchanger(s) or downstream of exchangers.
[00180] No vaporization of feed with original LNG composition is
contemplated with
the present process: the present teaching being to maintain the feed Rich LNG
stream in its
liquid form below its bubble point traversing the heat exchanger as an
essentially sub-cooled
liquid. No vaporization of Feed Rich LNG is "required" (vs. prior art) in any
heat exchanger
for feed or a portion of feed to the Column.
[00181] The use of a degasser is important in some modes of
operation/flexibility.
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[00182] Column pressures ranging from 50 psig to 1600 psig and more
particularly
100 psig to 700 psig and even more particularly ranging from 400 psig to 700
psig with
embodiments of close to 550 psig to 600 psig are included within the scope of
the present
disclosure.
[00183] No Rich LNG feed split is taken pre/post exchanger(s) (as noted in
other prior
art teachings) for purpose of feeding to column as column cold reflux and feed
streams.
Unlike with the prior art, no splits are taken of Feed Rich LNG stream to
separately feed
Column as feed and reflux.
[00184] In the present disclosure, the feed location on the column varies
according to
the mode of operation dictated from the hybrid functionality of the column
described herein.
[00185] Various of the following columns can be emulated in various
proportions
effectively making this a hybrid column with various degrees of functions of
the following
column configurations with additional pressure swing functionality or pressure
variability
functionality to match most effective use of this process of disclosure:
Distillation column;
Extractive distillation column; Reboiled absorption column; Absorption column;
Stripping
column; Refluxed stripping column; and Reboiled stripping column.
[00186] The teachings of the present disclosure of employing a bottoms
reboiler
arrangement does not rule out the use of side exchangers and stream
optimizations integrated
to the column for heat distribution or recoveries; and further particularly
heat recovery
integration of bottoms discharge stream.
[00187] Column temperatures are managed by managing the bottoms exchanger
temperature and feed stream properties to the column as demonstrated in the
various streams
to and from the column shown in TABLES 1A to 6A embodiments; stream 6 being
indicative
of bottoms temperature.
[00188] The present disclosure teaches obtaining almost 100% liquid lean
LNG via
condensing in the LNG exchanger against the cold of feed Rich LNG being
processed as
shown in the embodiments.
[00189] In one embodiment of the present process, the process can achieve
up to 99%
ethane recovery.
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[00190] For NGL and C2-Recovery/Rejection modes of operation the present
teachings can achieve industry/commercial Pipeline Specification (<0.5%v C1
content, <600
psi TVP), NGL product without any further processing to achieve this result.
[00191] The present teaching can perfonn in "most" of the desirable modes
liquid
Lean LNG and high C2+ recoveries without any need for compression equipment.
[00192] A smaller Column is contemplated than other arts ¨ the column of
the present
invention can require about 10 theoretical trays vs. others requiring about 20
trays.
[00193] The present invention teaches a versatile Column ¨ a Column with
hybrid-
configurations and perfoimance.
[00194] The present invention provide for economy of all equipment - number
and
duties.
[00195] One difference in the present process from the prior art is a
reduction in the
number of equipment and complexities of equipment/process/Degrees-of-Freedom.
Another
difference is that the present invention provides a system with ability to
avoid temperature
crosses in the LNG exchanger.
[00196] Yet another difference in this invention/process is that liquid
state is
maintained for the feed LNG (RLNG/VLNG) from storage to being warmed in
exchanger(s)
to liquid feed to degasser to column (optionally liquid feed can be connected
directly to
column) in contrast to the prior art teachings of vaporizing or partially
vaporizing feed
stream(s) or split parts of streams in exchanger/exchangers prior to feeding
the VLNG
stream(s) to the column. One manner in which to maintain the mixture in its
liquid state is to
maintain the mixture substantially or discernibly below bubble point. It is an
object of the
present invention to suppress as much as possible vaporization of rich LNG in
the heat
exchanger, and the present invention does not require the step of vaporizing
at least a portion
of the rich LNG prior to passing it to the fractionation column. Another
difference in this
inventive design/process is that liquid state is maintained for the feed LNG
(RLNG/VLNG)
from storage to being warmed in exchanger(s) to liquid feed to mixing-
vessel/degasser
wherein composition/enthalpy change is effected and the vapor/liquid outlets
of mixing-
vessel/degasser connected to optimal points in the processing column
(optionally mixed
composition effected feed stream can be connected directly to column without
vapor/liquid
separation, as an optional embodiment not fully shown here) in contrast to the
prior art
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teachings of vaporizing or partially vaporizing VLNG feed stream(s) or split
parts of streams
in exchanger/exchangers prior to feeding it to the column variously as non-
composition-
changed liquids/vaporized forms of VLNG.
[00197] Still
another difference from the prior art is with one embodiment shown, a
column bottoms liquid stream is recycled to the column via mixing in the
degasser
(vessel/device) changing the composition/enthalpy of the feed LNG which was up
to this
point VLNG (virgin LNG) prior to mixing with the warm bottoms stream. Yet
another
difference from the prior art is that the fractionation / processing column
pressure is
controlled to manage the LNG exchanger operation so that VLNG is kept in its
liquid state
while exchanging heat from the warmer processing column OVHD (overhead)
stream. A
further difference is that VLNG pump pressuring can be controlled flexibly
depending on
VLNG composition and state as a utility to make the overall system work as
required in
tandem with processing column pressure operation selection.
[00198] Another
difference is that the column pressure is controlled/controllable to
prevent "temperature crosses" in the LNG exchangers ("temperature crosses"
being typical
to other art) essentially making this inventive process as a whole
practical/feasible and
drastically reducing complexities of exchangers or networldbanks of exchangers
otherwise
required to overcome "temperature crosses" or overcome undesirable/uneconomic
exchanger
design otherwise needed to overcome narrow "temperature approaches" or
"temperature
pinch" characteristics.
[00199] A further
difference from the prior art is that the OVHD stream can be
essentially fully condensed while exchanging heat and cooling down against the
VLNG (or
other optional streams/refrigeration not shown) without need for recompression
prior to
condensing as the LLNG liquid Product. Yet another difference is that the
invention provides
the ability for a purified lean LNG (LLNG) to be split and utilized as reflux
in the processing
column. The
invention also provides, optionally, combinations of VLNG-
Pump/Column/LNG-Exchanger/Bottoms-Recycle pressures/temperatures/compositions
that
can be adjusted to adjust slates of required product or BTU specifications for
OVHD LLNG.
[00200] Another
difference over the prior art is that the present invention provides,
optionally, combinations of VLNG-Pump/Column/LNG-Exchanger/Bottoms-Recycle
pressures/temperatures/compositions that can be flexibly adjusted (essentially
utilizing
VLNG-pump pressure, valves, processing column pressure with valves, stream
recycles,
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reflux) to adjust slates of required product specifications for NGL products
for varying C2+
extraction/rejection content. Optionally, another difference and embodiment
indicated is with
certain combinations of operations vapor stream 11 from vessel 70 if generated
which as gas
stream can be condensed in a heat Exchanger CXG 90 after compression (80) and
the
condensed portion (12) can be mixed in with the LLNG (12D) or with the reflux
(15A, 15B)
to the column or degasser.
[00201] Yet another difference from the prior art is that optionally the
stream 13 (or
can be independent from process refrigeration/cooling stream 14A, 14B) can be
used for
condensing stream 12 from the compressor 80, and stream 13 may comprise
another RLNG
or other desirable stream to be processed or to enhance the operation that can
be added in or
mixed with the main VLNG or optionally connected directly to the column.
[00202] Any person skilled in the art or science, particularly one who is
used to
Process Engineering skills will, having had the benefit of the present
disclosure, recognize
many modifications and variations to the specific embodiment(s) disclosed. As
such, the
present disclosure, including examples, should not be used to limit or
restrict the scope of the
invention or their equivalents. Although embodiments have been shown
illustrating
operation of the processes of the present disclosure, those of ordinary skill
in the art having
the benefit of this disclosure could create other alternative embodiments that
are within the
scope of this invention. For example, with the benefit of the present
disclosure, those of
ordinary skill in the art will appreciate and understand that modifications
and alternative
embodiments to the process or method or system or improvements disclosed
herein and
comprise any feature described, either individually or in combination with any
feature, in any
configuration or individual steps or processes or combination of individual
steps or processes
for equipment design, operating, separating or recovering components of
varying volatilities
from Liquefied Natural Gas (LNG) or any other mix of hydrocarbons or other
fluid mixes in
a fluid phase.
[00203] References:
[00204] The following represents an exemplary list of U.S Patent
references:
[00205] U.S. Patent No. 6,510,706 (Stone et al.) (January 28, 2003).
[00206] U.S. Patent No. 7,165,423 (Winningham) (January 23, 2007).
[00207] U.S. Patent No. 7,631,516 (Cuellar et al.) (December 15, 2009).
[00208] U.S. Patent No. 7,216,507 (Cuellar et al.) (May 15, 2007).
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CA 02818326 2013-05-16
WO 2012/054729
PCT/US2011/057106
-45-
[00209] U.S. Patent No. 7,010,937 (Wilkinson et al.) (March 14, 2006).
[00210] U.S. Patent Publication No. 20080098770 (Ransbarger) (May 1, 2008).
[00211] U.S. Patent Publication No. 20090221864 (Mak) (September 3, 2009).
[00212] All references referred to herein are incorporated herein by
reference as
providing teachings known within the prior art. While the apparatus and
methods of this
invention have been described in teinis of preferred embodiments, it will be
apparent to those
of skill in the art that variations may be applied to the process and system
described herein
without departing from the concept and scope of the invention. All such
similar substitutes
and modifications apparent to those skilled in the art are deemed to be within
the scope and
concept of the invention. Those skilled in the art will recognize that the
method and
apparatus of the present invention has many applications, and that the present
invention is not
limited to the representative examples disclosed herein. Moreover, the scope
of the present
invention covers conventionally known variations and modifications to the
system
components described herein, as would be known by those skilled in the art.
While the
apparatus and methods of this invention have been described in terms of
preferred or
illustrative embodiments, it will be apparent to those of skill in the art
that variations may be
applied to the process described herein without departing from the concept and
scope of the
invention. All such similar substitutes and modifications apparent to those
skilled in the art
are deemed to be within the scope and concept of the invention as it is set
out in the following
claims.
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