Note: Descriptions are shown in the official language in which they were submitted.
CA 02565477 2006-10-24
STEAM CEIVERATIblyApEARAT'C.JS AND METHM
FIELD OF THE YN'VENTTax
The present invention relates to a steam generator and in particular to a
steam
generation apparatus and method replacing natural gas as fuel with a selected
portion of
bitumen, asphaltines or heavy oil optini.ised for desired energy or steam
production.
BACKGROUM QT' THE IlVVENICI4N
Steam is often used in industrial processes. For example, steam can be used
for heat
exchange, as a power source for driving turbines, etc.
In the petroleum industry, for example, a particular application is for the
generation of
steam for the recovery of bitumen or heavy oil. A conlmon process utilized for
the in situ
recovcry of heavy oil or bitumen is to inject steam underground pursuant to
which the
viscosity of bitumen or heavy oil is decreased such that it flows and is
capable of being
pumped to the surface. For this, steam ganeraaon apparatus commonly called
steam injection
boilcrs ("SIB") are used to generate steam of the required/desired quality or
quantities. These
boilers are typically fired with natural gas (which is piped to the boiler) in
order to heat water
to generate the desired steam.
The current art typically uses natural gas as the fuel to fire most oilfield
steam
generation boilers. For in situ recovery of bitumen or heavy oil, prominent
processes utilized
are steam assisted gravity drainage ("SAGD") and cyclic steam stimulation
("CSS"). The
SAGD process is presently the most commonly used process for recent and new
projects due
to its enhanced efficacy in the recovery of bitumen or heavy oil. Generally,
80% quality steam
is requiredJdesired to be generated by the boiler in specified volumes per
hour depending on
output capabilities of the boiler, as well as ateam output requirements for
the recovery and
extraction process. Exceeding 80% quality renders a project uneconomical,
largely due to
water treatnnent costs. Conversely, lower than 80% quality steam introduces
lnefficiencies to
d1e process utilized for heavy oil or bitumen recovery and, hence, Is also
undesirable from a
cost-effectiveness perspective. Typically ll-ie qaality of the steam will
degrade as heat
exchange surfaces foul over the run time of the equipment.
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CA 02565477 2006-10-24
Typical probletns generally encountered under conventional steam generation
boilers
include (but are not linmited to):
a) failure to maintain 80% quality steam (or such other quality of steam as
required or desired) at the outlet of the boiler - often (ower quality steam
is generated;
and
b) cost of fuel, typically na.tural gas, to fire the boilers used for steam
generation (plus the cost of associated pipeline construction and maintenance
to bring
the natural gas or other fuel to the boiler).
In addition, problems typical for pipeline transport of produced bitumen
includc that
the availability and handling of diluent increases the overall cost of
transporting the bitumen
to upgrading facilities, pipalines are required to return diluent to the
production facility, and
electrical power required at the production facility and pipeline facilities
often requires
expensive transmission lines from the power host or supplier.
It has been proposed previously to convert to other fuels so that propane or
light fuel
oils could be utilized to fire the boilers instead of natural gas. However, as
with natural gas, a
source for the propane or ligbt fuel oils would need to be located nearby in
order to be piped
to the boiler, thus increasing costs. Moreover, the heat input to the boiler
will change due to
the difference in rhe energy density of the new fuels, resulting in a drop in
the steam quaIity
and/or the production of less steam and, in turn, less heavy oil or bitumen
being produced.
Liquid fuels will create a longer flame, in other words, of different shape
than that for which
the combustion chamber was designed and built to accorAmodate. As suah,
existing boilers
will have to be derated such that existing fire boxes can be utilized to
accommodate the
ditferently shaped name when liquid fuel is used.
Moreover, an alternative processes which utilize solvents instead of steam to
reduce
the viscosity of heavy oil or bitumen is presently being employed for the
recovery and
extraction of heavy oil and bitumen. However, while possessing the advantage
that it does not
require natural gas for firing the boiler or for that matter the boiler (and
related ancillary
equipment) or the water which is heated to create steam, still must overcome a
significant cost
disadvantage relative to the SAGD and CSS processes for recovering and
extracting heavy oil
or bitumen.
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CA 02565477 2006-10-24
Canadian patent application No. 2,149,617, published August 21, 2004, teaches
a
method for enabling the use of a heavy oil residuum" by converting it to a
useful product.
The method involves the use of a heavy oil residuum which is substantially non
flowable. The
viscosity of the residuum is reduced by the application of heat and use a
diluent. This method
appears to suggest the use of that a diluent to reduce viscosity of the
residuurn, and the
maldng of an emulsion with the heavier residuum, and subsequently with water,
and then
burning the resultant product to produce energy as heat. The burning of the
residuum
emulsion result in a net energy contribution from the residuum's combustion.
C.ynited States Publication no. US 2005/0218037 published October 6, 2005,
teaches a
system for heating multiphase residues containing water, oil and solids to
obtain hydrocarbons
and other useful pmducts. This system comprises a tubular reactor provided
with a fixed pitch
screw conveyor where the multiphase residue is heated under reduced pressure
and in the
pxesence of an inert gas, the heating being carried out in distinct
temperature zones with a first
zone of cvaporation of free and emulsifted water and extraction of light
hydrocarbons, a
second zone of thermal desorption and a third zone of mild pyrolysis, the
various hydrocarbon
fractions being collected in condensers at the relevant stages, while the
solids are separated
for post-treatment and industrial use,
SUMMARY OF THE IN'VEIVTION
The present invention provides a steam generation apparatus for replacing
natural gas
as the fuel for f'iring a boiler with a liquid fuel comprised at least in part
by bitumen,
tasphaltines or heavy oil that may be locally produced, while maintaining the
net undesirable
emissions arising from the combustion of heavy oil or bitumen to a level which
are within
current environmental guidelines and legislation, and const.antly and
consistently producing
80% quality steam or such other quality of steam as may be required or
desired. The liquid
fuel includes a variable and energy/cost optimized component of bitumen,
asphaltines or
heavy oil, which may be locally produced.
The present invention provides a steam generation apparatus which uses bitumen
or
heavy oil produced from the field in order to separate heavier ends of the
produced
hydrocarbons for use as fuel. The lighter products from the included
separation equipment are
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CA 02565477 2006-10-24
blended into the produced bitumen, thus also increasing the API gravity of the
mixed materiai
and reducing the amount of diluent required for pipeline transportation. The
technology may
be employed by existing open pit mining operations for the generation of steam
and power by
burning asphaltines or bitumen components rather than natural gas.
In accordance with a broad aspect of the present invention, there is provided
a steam
generation apparatus replacing natural gas as fuel with a liquid fuel from a
component of a
feedstock, the feedstock being bitumen, asphaltine or heavy oil, comprising a
refinery for
separating products from the feedstock, some of the products to be used to
provide the liquid
fuel; a steam generation subsystem fueled at least in part by the liquid fuel;
a product tank
system for storing the products from the refinery with a delivery system to
deliver selected
components of the products to parts of the apparatus, particularly those of
the products used to
provide the liquid fuel.
In accordance wich another broad aspect of the pmsent invention, there is
provided a
steam generation apparatus where the refinery is provided with the ability to
separate and
produce several different products such as produced gas vapour, condensates,
gas oil or
vacuum gas oil draws depending upon the niakeup of the fecdstock, with the
bottom product
of the tower being an asphaltine, where, in a preferred embodiment, the
modulation of the
energy output is done by adjustment of the refinery's output of asphaltene or
other product to
adjust the amount and nature of the liquid fuel provided by the asphaltene or
other product
In accordanco with anothcr broad tttpcct-of tF,e-proacnt iflvention; a-mothoE}
of - - -- ---- -- --
generating energy in the form of steam is provided using liquid fuel from a
component of a
feedstock, the feedstock being bitumen, asphaltine, or heavy oil, comprising
the steps of in a
refinery, separating products from the feedstock, some of the products to be
used to provide
the liquid fuel, in a steam generation subsystem, burning the liquid fuel,
through a product
tank system for storing the products from the refinery using a delivery system
to deliver
selected components of the products to parts of the apparatus, patticularly
those of the
products used to provide the liquid fuel to fire the steam generation
operation, and in a
preferred embodiment, where the refinery is provided with the ability to
separate and produce
several different producta such as produced gas vapour, condensates, gas oil
or vacuum gas
oil draws depending upon the makeup of the feedstock, with the bottom product
of the tower
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CA 02565477 2006-10-24
being an asphaltine, and in a nother embodiment, where the modulation of the
energy output
is done by 4ustment of the refinery's output of asphaltene or other product to
adjust the
amount and nature of the liquid fuel provided by the asphaltene or other
product.
In accordance with another aspect of the present Invention, lighter portions
of the
products of the refinery are added to produced bitumen, asphaltines or heavy
oil as diluent for
reducing the produced material's viscosity in order to facilitate a reduction
in the amount of
extraneously provided diluent required to meet pipeline specifications for
transport, and
which in another embodiment also provides for the use of generated power
(whether heat in
steam or electrical power generated from produced steam or otherwise) to
provide heat to
surface equipment to increase efficiencies in cold ambient temperatures or
which also
provides for the use of power (whether heat in steam or electrical) to elevate
pipeline
temperature$ to reduce diluent requirements in dilbit by reducing viscosity
with temperature
increase of pipeline (and included dilbit)
CA 02565477 2006-10-24
BRIEF DFSCRIPTIOx or THE DRAWINGS
A futther, detailed, description of the invenaon, briefly described above,
will follow
by refercnce to the following drawings of specific embodiments of the
invention. These
drawings depict only typical embodiments of tho invention and are therefore
exemp]ary and
descriptive but are not to be considered limiting of its scope. In the
drawings:
FIG. 1 is a partial schematic showing a feed drum and pumps of the present
invention.
FIG. 2 is a partial schematic showing heat exchangers and an alternate
application of
the heater described in the prior art.
FIG. 3 is a partial schematic showing a vacuum t.owar and pumps of the present
invention.
FIG. 4 is a partial schematic showing the blending and storage tanks of the
present
invention.
FIG. 5 is a partial schema.dc showing an off-gas compressor system within the
present
invention.
F1G. 6 is a partial schematic showing the Bitumen Firing Unit steam generator
of the
prior art, and flash drums of the system, configured for use in accordance
with the present
invention.
FIG. 7 is a partial schematic showing a Bitumen Firing Unit steam generator
and flash
drums configured for use within the present invention.
FIG. 8 is a partial schernatic showing the Bitumen Firing Unit steam generator
and
flash drums configured for use within the present invention.
FIG. 9 is a partial schematic showing the low pressure steaun flash drum of
the present
invention.
FIG. 10 is a partial schematic showing the power generation system of the
present
invention.
FIG. 11 is a partial schematic showing the flare system of the present
invention.
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CA 02565477 2006-10-24
nFmAIY.Eri riFSCRETYON OF THE IlWENTION
The present invention generally comprises bitumen feed surge vessel, heat
exchanger
system, a heater, a vacuum towe.r, an off-gas compressor, product eankage, and
tlow control
system, a steam generation system, a power generation system, and a flare
system.
It is to be understood that the description following is an embodiment of the
present
invention, is descriptive and exemplary but no limiting, and that there are
substitutions and
replacements of certain process equipment or process steps which will be
apparent to those
sldlled in the att, and which are claimed as pan of this invention.
Bitumen Feed Surge Drum
Referring to FIG. 1, in this embodiment bitumen is dewatered utilizing
standard
SAGD equipYnent prior to entering through a feed surge drum 10 through supply
line 1. The
feed surge drum 10 has an internal baffle (not shown) and a boot for water
separation. The
boot on the drum 10 will be contralled with an interface level control. The
drum 10 is purged
with nitrogen 11 for pressure control on the drum 10. The drum 10 ideally does
not produce
significant amounts of hydrocarbon vapour off the drum 10 because of the low
operating
temperature. Any smRll amount of hydrocarbon vapours is safely disposed of in
the closed
flare system Ehrough valve 12. The drum 10 also provides the ability to
automatically
bypassproduced bitumen from the drum 10 to bitumen blend tanks 61 or 62
through line 6 as
shown in FIG. 4. A bitumen feed pump 13 provide the pressure to deliver the
bitumen to two
locations. The primary feed line 4 will be flow controlled through the feed
heat exchangers
21, 22, 23, 24 and through a heater 30 (asphMtine fired) and into a vacuum
tower 40. The
flow rate of the bitumen into the exchanger train is set by matching the
firing requirements of
the heaters with the asphaltine production from the bottom of tower 40. The
level in the
Residual Storage tank 64 will automatically reset the flow into the exxchanger
train to maintain
the balance. The secondary line 6 will bypass the vacuum tower 40 for blending
with the
vacuum gas oils and then sent to the bitumen blend tanks 61 and 62.
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CA 02565477 2006-10-24
Feed Heat Exchanee Train
Referring to FIG. 1 and 2, in.this embodiment, the bitumen enters a heat
exchanger
system 20 essentially dry. The heat exchanger system 20 consists of four
series. First
exchanger 21 in the series will be used as a pre-condenser for the Vacuum
column overheads.
Second exchanger 22 in the series preheats the bitumen against the gas oil
product
Third exchanger 23 in the system is a cross between the vacuum gas oil and the
bitumen.
Founh exchanger 24 in the series is a cross between the asphaltines and the
bitumen. The heat
exchanger train takes advantage of the available heat in the system in order
to minimize the
energy requirements of the BFU heater 30.
BFU Heater
Referring to FIG. 2 and 3, a BFU heater 30 has been completely described in US
Patent No. 6,990,930. In this embodiment, the BFU heater 30 has been adopted
for use within
a vacuum column system. The temperature of the bitumen entering a vacuum tower
40 is
controlled on the outlet of the BFU heater 30. The temperature of the bitumen
may be
controlled by adjusting the flow rate of the asphaltines entering the burners.
The atomizing
steam flow rate is flow controlled based on a fixed ratio with the asphaltine
flow.
Hydrocarbon gas produced from the vacuum tower 40 may also be burned in the
BFU heater
30. The BFU heater 30 can have other services in addition to heating the
bitumen. A first
service is to superheat low pressure atomizing steam, a second service is to
superheat high-
pressure steam for power generation, and a third service is to share duty with
the OTSG (Once
Through Steam Generators) for higher steam quality. The merits of providing or
using these
varlous services would be determined based on individual project requiroments.
Vacuum Tower
Referring to p'TG. 3 and 4, in this embodiment, a refining step is taken using
a vacuum
tower 40, which is primarily used to separate the asphaltines frorn the
balance of the gas oils
and fuel gas contained in the bitumen feed. Stripping steam is used to enhance
saparatlon
efficiency. The steam is controlled at a desired flow rate. The ratio of steam
to bitumen is
typical for refinery vacuum tower 40 applications.
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CA 02565477 2006-10-24
There are typically a number of products that are removed fxom the vacuum
tower 40
during and resulting from its processing of the bitumen feedstock. Asphaltines
are removed
from the bottom of tha vacuum tower 40. Vacuum gas oil (VGO) and gas oil (GO)
are
removed from middle of the vacuum tower 40. Condensate is removed as a liquid
product
from a reflux drum 44. These three products are cooled though heat exchangers
22, 23 and 24
against the incoming bitumen, combined and pumped by pumps 41, 42 and 43 to
the bitumen
blend tho tanka 61, 62. Vacuum tower bottoms are pumped Into the Resid Storage
Tank 64.
The product temperature of the gas oil and vacuum gas oil may be controlled
with a bypass.
This will maintain a constant or desired velocity on the bitumen side of the
heat exchangers
22, 23 and 24 for fouling control and prevention considerations.
The vacuum tower 40 overheads are pre-cooled against the bitumen through
exchanger 21 on line 8 and then further condensed in an overhead condenser 45.
The vacuum
tower overhead temperature is controlled with a hot gas bypass around the
overhead
condenser 45. The internal pressure in the column is controlled with a back
pressure control
into the suction of the off gas compressor 51 shown in FIG. 5 though Iine 7b.
The two phase overhead product is separated in the overhead reflux drum 44.
The
vacuum tower reflux pump 46 returns the reflux back to the top of the vacuum
tower 40 under
flow control. The condensate product is removed from the overhead reflux drum
44 under
level control, blended with the VOO and GO and pumped to tanks 61 and 62
through line 7a.
Water is separated in the boot of the overhead reflux drum 44 and is sent
through line
7 c to the unit battery limit for treatment in offsite facilities. The level
in the boot is controlled
with an interf$ce level control (not shown). The requirement for a water pump
will be
determined as required for a specific project needs.
The vapour product off the reflux drum 44 is eompressed in down stream
equipment
and then used as fuel gas for the heater 30 and flare header sweep gas.
Asphaltines are removed from the botto= of the vacuum tower 40 and arc pumped
by
pump 43 into a product tank 64 for storage through line 8. The temperature of
asphaltines
entering the product tank 64 will be controlled by bypassing a portion of the
BFW (Boiler
Feed Water) around the heat exchanger 25. This will allow a relatively
constant continuous
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CA 02565477 2006-10-24
flow of asphaltine through the exchanger 25 such that minimum velocity can be
maintained
for control and prevention of fouling considerations.
Off Gas Compressor
Referring to FIG. 5, the off gas compressor 51 has two main functions: one is
as a
vacuum source for the vacuum tower 40; and the other is to inorease the
discharge pressure of
the fuel gas to acceptable levels.
An off gas cooler 52 and off gas knock out drum 53 are included in this
embodiment.
The Knock out dium 53 will typically be a two phase separator. The compressed
fuel gas will
used as fuel in the hoater 30 though line 31 and flaro header sweep gas though
line 107. The
condensed hydrocsrbons will be blended with the condensate from the reflux
drum 44 and
used to increase the API of the blended bitumen.
Product Tanks
Four 40,000 bbl product tanks 61, 62, 63 and 64 typically are specified for a
facility.
In this embodiment, tanks 61 and 62 will be used as day tattks for the
blending of gas oil,
vacuum gas oil, condensate, diluent and bitumen. Ti3e blending will occur on-
line and
agitators have been included in the tanks 61, 62 to ensure uniformity of the
dilbit. Additional
storage space within the tank has been provided for quality control prior to
transferring the
dilbit into the pipeline. The tanks 61 and 62 can be used as emergency storage
for produced
bitumen. The tank 63 is a floating roof tank for diluent storage. The
asphaltine fuel system
will be designed with a continuously circulating system to ensure that the
lines remain
flowing.
Steam Generation Euuinment
Referring to FIG. 6 through FIG. 9, clesired steam generation 70 is the result
of a
balance between asphaltine production from the bottom of vacuum tower 40 and
over-all
system demand for sbeaun production, for example: form.ation *stiruulation,
power generation
or process use, more typically a mixed set of those uses. The flow rate of
bitumen into the
vacuum tower 40 is set to niaintain that balance. Fluetuations in the energy
balance can be
aceommodated by the surge time in the storage tank 64.
CA 02565477 2006-10-24
For example, boiler feed water of appropriate quality for 1600 psig steam will
typically be available &oxn offsite facilities. A boiler feed water pump 17
has been included to
increase the pressure of the boiler feed water appropriate to the required
steam pressure. The
boiler feed water flowed though Gne 1 to the heat exchanger 24 will be
preheated against the
vacuum tower asphaltines.
Stesun is generated using a combination of once-through steam generator and
separately fired coils within the heater 72a-72f. The once-through steam
generator and the
heater coils will be fired with asphaltines and/or fuel gas. Based on project
requirements, the
f'ired equipment may be designed for multiple fuel applications, i.e.
asphaltines, bitumen or
natural gas. This flexibility may be required for stait-up purposes if there
is no source of
stored heavy fuel or if energy demands fluctuate or costs are such that the
energy capable of
being provided by asphaltines alone is sub-optimal. The combination of once-
through steam
generator and the heater 30 will produce steam consistently at 80% quality
without up-grading
typical water treatment facilities.
Flash drums 71a-71f are shown here for each of the steam generators 72a-72f.
The
condensate that is recovered from the high pressure f7ash drums 71a 71f is
pumped by pumps
73a-73f back to the inlet of the once-through steam generator and heater 72a-
72f.
High pressure condensate is also let down to 150 psig as a source for
generating low
pressure steam. A flash drum 64 has been provided as the knock-out dnun for
generating the
150 psig steam. Condensate from the flash drum 64 is used as the continuous
blow down for
the steam system. This condensate is sent to the unit battery limit for
disposal offsite. The 150
psig s[eara is flow controlled into the vacuum tower 40 for stripping steam.
The low pressure
steam is also superheated in the heater and used for atomizing steam.
Power Generation Ecruigment
Referring to FIG. 10, power generation equipment 80 has been provided to power
all
the electrical needs for the equipment described. Additional power generation
can be
accommodated based on desired energy outputs. Adjustments can be made to the
design of
the vacuum tower 40 such that additional asphaltines can be separated from the
bitumen and
used in the production of steam. This adjustment to the heat and refining
balance can have at
least some of the following material benefits: Fir.st, a SAGD facility can
become an island
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CA 02565477 2006-10-24
with no incoming tran.smission lines; and Second, a SAGD facility could be a
net exporter of
power depending upon the ability to sell or use the excess power; and last,
ad.clitional
condensate, gas oil and vacuum gas oil is pmduced and can be used as diluent
components to
further reduce bitumen viscosity bringing a further net reduction in diluent
and diluent support
requirements and associated costs and facility complexity.
For example, dry, high pressure steam is superheated in a separate coil in the
heater
30. The high pressure superbeated steam is then used in a condensing steam
turbine generator
81 though line 2 to generate the necessary power. It is also possible that an
extraction turbine
could be specified as an alternative to generating the lower pressure steam.
The condensate
from the steam turbine generator is further cooled in a surface condenser and
vapours
removed in a downstream atmospheric flash drum 83. The lower pressure
condensate is
pumped back to the boiler feed water feed pump 17 and used as blow down from
the steam
system.
Y+9are
Referring to FIG. 11, vessels in hydrocarbon service will be protected from
overpressure with a closed flare system 90. The Flare system 90 will be
designed based on
API RP 521. The flare system in a profeired embodiment will include the flare
distribution
system, a knock out drum 91, a knock out drum pumps 92 and a flare stack 93.
Liquids
collected in the knock out drum can be returned to the feed surge drum
12
