Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPMATUS F~R THERMAL TREATMENT
OF A HYDROCARBON STREAM
Field of the Invention
This invention relates to an apparatus in which the
~iscosity of hydrocarb~ns can be reduced through thermal
treatment, thereby improving the transportability of the
hydrocarbons.
Back~round of the Invention
Vertical tube reactors which use a subterranean U-
tu~e configuration for pro~iding a hydrostatic column of
fluid sufficient to provide a selected pressure are
known. ~his type of reactor has been primarily used for
the direct wet oxidation of materials in a waste stream
but may algo be used for pyrolysis, alkylation,
hydrolysis and hydrogenation of waste streams. As
exemplified by the following patents, reactors of this
nature typically comprise a subterranean vertical U-tube
reactor system consisting of influent and effluent
conduits concentrically arranged for heat exchange, a
reaction zone at the bottom of the reactor, and in some
cases, a jacket containing heated media for the external
heating of the reaction zone, and pipes to supply oxygen
or other reactant gases.
Bauer, in U.S. Patent No. 3,449,247 (1969),
disclo6es a method for the wet oxidation of fluid sewage
mixed with combustable refuse. Air is pumped into the
influent stream at the well head and is pumped directly
into the reaction zone from a subterranean compressed
air storage chamber. Pressure in the reaction zone
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produced by the hydrostatic head may be augmented by a
pressure regulating device on the effluent stream.
Lawless, in U.s. Patent No. 3,606,999 (1971),
discloses a method and apparatus for carrying out
oxidation of sewage or aqueous industrial waste. In
addition to the U-tube conduits, the apparatus includes
gas venting and supply lines, floats and sparges. Air
and/or other reactant gases are introduced to the
reaction zone through gas lines travelling down the feed
pipe (inner conduitJ to the sparges. Air released from
the sparges and product gases are trapped in the floats,
lending buoyancy to the same. The floats are used to
support the feed pipe.
Land, in U.S. Patent No. 3,464,855 (1969),
discloses a method for the aqueous digestion of wood
chips. The patent discloses a ~ariation on the U-tube
appara~us in that the well installations contain at
least three concentric annular passages. Countercurrent
coaxial flow paths containing the wood chip solution
comprise two of the annular spaces. The coaxial flow
paths are in fluid communication with each other at the
soaking reservoir at the well bottom. Additional
annular spaces, which are not in fluid communication
with reactant materials in the countercurrent coaxial
flow paths, are described as carrying steam or other
heated fluids to serve as a source of external heat to
reactant material in surrounding annular spaces. A
valve or plate on the reaction product effluent and a
reactant influent pump augment the hydrostatic pressure
of material within the coaxial pathways.
Titmas, in V.S. Patent No. 3,853,759 (1974),
discloses 8 method for pyrolysis, alkylation, hydrolysis
and hydrogenation of raw sewage and f~r the
devulcanization of aqueous rubber solutions in an oxygen
deficient environment. Titmas has a steam or heat
energy line running axially down the center of the liner
~inner condult) to deli~er steam or other heated media
to the reaction zone. The reaction zone is within an
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1327952
orifice created by annular rings arranged on the inner
surface of the liner and the outer surface of the steam
line; steam or other heated medium is injected into the
orifice to maximize pressure and temperature in the
orifice area. The liner conduit may be suspended for
the purposes of accommodating metal expansion upon
heating.
~ cGrew, in Patent No. 4,272,383 (1981), discloses a
method and apparatus for the wet oxidation of sewage
sludge. The first or outer conduit of the U-tube has a
closure at its lower end and the second or inner conduit
terminates and is suspended above the outer conduit
closure. The reaction zone, which is located within the
bottom portion of the outer conduit, is temperature
controlled by heat exchange with a heated media in a
surrounding annular jacket. The apparatus further
comprises a pump for pumping influent into the downgoing
flow pipe. Oxygen or other reactant gas may be
introduced into the downgoing flow passage at the
surface and at inlets at spaced intervals below the
ground surface level to form enlarged nTaylor" gas
bub~les within the influent.
Bain, in U.S. Patent No. 4,778,586 (1988),
discloses a method and apparatus for the treatment of
whole crude to reduce its ~iscosity and render it more
suitable for transportation by pipeline or ship. The V-
tube apparatus contains three concentric annular
passages. ~wo of *hese passages, the downcomer and the
riser, cont~in the hydrocarbon stream and are in fluid
communication with each other at the well bottom in the
reaction zone. The third annular passage is a jacket
located adjacent to portions of the riser and downcomer
corresponding to the reaction zone. The heat exchange
~lu~d circulated through the jacket provides the
external source of heat used to raise the temperature of
the stream to the reaction temperature. Temperature
sensors in or above the reaction zone can be used to
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~ control the temperature of the jacket heat exchange
fluid and minimize formation of coke on conduit walls.
Although the U-tube configuration of the above-
cited patents contain inner and outer conduits in heat
exchange relationship, annular jackets surrounding the
reaction zone with heating media therein and/or air or
yas conduits at a variety of locations and depths, none
of the patents suggest or disclose an apparatus which
would be useful for the direct oxidative heating of a
hydrocarbon stream. Further, none of these patents
suggest or disclose the central placement and downstream
orientation of oxidant nozzles in the stream within the
reaction zone, feedback control relationship between
oxidant conduit valves, which control the oxidant flow
rate to the nozzles, and temperature monitors located in
or above the reaction zone.
The present invention involves an apparatus useful
in the method described in copending and commonly
assigned U.S. Patent 4,818,371, "Improved Viscosity
Reduction by Direct Oxidative Heating", issued April 4,
1989. Said patent describes a method for
providing direct oxidative heating of hydrocarbon
material to reduce viscosity thereof with reduced coke
formation on reactor walls. The method of U.S. Patent
4,818,371 involves direct heating of the hydrocarbon
influent stream by dispensing an oxidant centrally in
the influent stream, rather than external heating of the
influent stream by using heating elements or media in a
jacket in heat exchange relationship with the conduit
containing the reaction zone. The apparatus of the
present invention uses central placement and downstream
orientation of oxidant nozzles in the hydrocarbon stream
within the reaction zone to achieve the direct oxidative
heatin~ described in the process of Serial No. OS8,878.
The present invention further involves a feedback
contrcl mechanism between temperature monitors in or
above the reaction zone and oxidant conduit valves.
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Summar~ of the Invention
The present invention comprises an apparatus useful
for reducing the viscosity of a hydrocarbon stream by
direct oxidative heating. A vertical tube reactor is
disposed within a substantially vertical well bore in
the earth. The reactor comprises an influent c~nduit
and an effluent conduit. The influent conduit is in
fluid communication with the effluent conduit with each
of said conduits having an upper and a lower zone. The
influent conduit is adapted to receive an influent
hydrocarbon stream and conduct the stream substantially
downward. The effluent conduit is adapted to conduct an
effluent product stream substantially upward. The upper
zones of the conduits are adapted to bring the influent
stream and effluent product stream into heat exchange
contact with one another and produce a heated influent
stream. An oxidant injection nozzle is located within
at least one of the lower zones and is adapted to
introduce oxidant into the core portion of the heated
influent stream substantially parallel with and in the
direction of the flow of the ~tream. The resulting
reaction between the oxidant and hydrocarbons in the
stream produces the product stream.
In another embodiment, the instant invention
comprises the foregoing apparatus in which an oxidant
conduit is located within the well bore and travels
substantially parallel to the influent and effluent
conduits. The oxidant conduit is operatively connected
with the oxidant injection nozzle to supply oxidant to
said nozzle. The apparatus can also comprise a means
for controlling the flow rate of the oxidant within the
oxidant conduit. The controlling means is operatively
associated with the oxidant conduit and is adapted to
adjust the flow rate of oxidant through the oxidant
conduit.
In another embodiment, the appar~tus of the instant
invention comprises a temperature sensing means located
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downstream of the nozzle. The temperature sensing meansis adapted to detect the temperature of the hydrocarbon
stream and provide an output proportional to said
temperature.
In further embodiment, the apparatus of the instant
invention comprises a vertical tube reactor disposed
within a substantially vertical well bore. The
apparatus comprises concentrically arranged inner and
outer conduits having an upper and lower zone. The
influent conduit is adapted to receive an influent
hydrocarbon stream and conduct the stream substantially
downward. The effluent conduit is adapted to conduct an
effluent product stream formed from said influent stream
substantially upward. The conduits provide heat
exchange contact between the influent stream and the
effluent product stream to produce a h~ated influent
stream. An oxidant injection nozzle is located within
the lower zone of the effluent conduit. The nozzle is
adapted to introduce oxidant into the core portion of
the heated influent stream substantially parallel to and
with the flow of the stream to produce the effluent
product stream. At least one means for sensing
temperature is located within the effluent conduit
downstream from the nozzle and is adapted to produce an
output proportional to the temperature. A conduit for
conducti~g oxidant from the surface of the well bore to
the nozzle i6 located within the inner conduit, travels
substantially parallel to the conduit and is connected
to the nozzle. A means for controlling the flow rate of
oxidant within said oxidant conduit is operatively
associated with the oxidant conduit. This control means
is adapted to be adjusted in response to output from the
temperature sen6ing means and change the oxida~t flow
rate in a preselected proportion to the output. In a
further embodiment, this apparatus comprises at least
two oxidant in~ection nozzles spaced longitudinally
apart in the effluent conduit. Each of the nozzles is
separately associated with a means for controlling the
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flow rate of oxidant. The association is adapted to
provide separate control of oxidant flow to each of said
nozzles.
B~ie _Description of the Drawina
Fig. 1 is a schematic representation of a preferred
embodiment of the present invention.
Fig. 2 is a schematic representation of another
preferred embodiment of the present invention.
Fig. 2A is a schematic representation of an
embodiment of the oxidant flow control system and oxygen
and nitrogen delivery system for the reactor apparatus
of Fig. 2.
Fig. 2B is a schematic representation of an
embodiment of the surface facilities associated with the
reactor apparatus of Fig. 2.
Fig. 3 is a schematic representation of a thir~
preferred embodiment of the present invention.
Detailed Desc~iption of the Invention
As used herein, the term ~boundary layer" is
defined as the thin layer of the hydrocarbon stream
immediately adjacent to reactor walls or other
stationary surfaces in the reactor vessel, this layer
being characterized by ~ery~ low fluid velocities.
As used herein, the term ncore portion~ is defined
as the portion of the hydrocarbon stream other than the
boundary layer which is characterized by flow velocities
which are higher than boundary layer flow velocities.
The core portion can be in laminar or turbulent flow.
As used herein, the term ~bulk temperaturen is
defined as the average temperature in a cross-sectional
segment of t~e core portion in the hydrocarbon stream in
which there is sufficient mixing of the stream to
achieve a substantially uniform temperature throughout
the segment.
As used herein, the term "coking temperature" is
defined as a bulk temperature at which there is at least
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about 0.5 weight percent solid coke formation in a 24
hour period (based on the hydrocarbon stream).
As used herein, the nreaction pressure~ is defined
as a pressure or range of pressures in the reaction zone
at which the rate of viscosity reduction is
substantially increased.
As used herein, a hydrocarbon stream in nmultiphase
flown means a stream containing a component that, under
pressure and temperature conditions existing during heat
exchange between the influent and effluent streams, is
gaseous and causes the flow of said stream to be
turbulent. However, under pressure and temperature
conditions greater than those in the heat exchange area,
including those conditions in the reaction zone, the
component is liquid.
The present invention involves a reactor vessel
apparatus useful for providing an incremental amount of
heat to a hydrocarbon stream by introducing an oxidizing
agent into the core portion of the stream. The reactor
vessel is comprised of an influent conduit and an
effluent conduit in heat exchange relation with each
other, at least one oxidant injection nozzle located in
either or both the influent and/or effluent conduits, a
conduit adapted to transport oxidant to the nozzles and
valve means in the oxidant conduit to control oxidant
flow to the nozzles. Additionally, the apparatus can
further comprise one or more of the following elements:
a heat exchange area located a~ove and in fluid
communication with the influent and effluent conduits
for use in heating the influent stream: a heater above
and in fluid communication with the influent conduit for
heating the influent stream; a pump to increase the
initial pressure Or the hydrocarbon stream: static
mixers in the reaction zone: emergency apparatus to
flood the oxidant lines with inert or non-reactive gas
to avoid an explosion in the event hydrocarbon stream
enters the oxidant line; an additional annular space or
jacket surrounding the portion of conduit corresponding
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to the reaction zone with heated media therein toexternally heat the reaction zone: a conduit to receive
the effluent stream from the effluent conduit and
conduct it to a separation/compression unit; one or more
temperature monitors in the conduits; one or more
pressure monitors in the conduits: and/or a conduit to
convey gas or volatile liquids from the
separation/compression unit to the influent conduit for
mixing with the influent stream.
U.S. Patent 4,818,371, discloses a process
in which an incremental amount of heat is added to a
hydrocarbon stream by introducing an oxidizing agent
into the core portion of the stream. The oxidizing
agent rapidly oxidizes components in the stream in an
exothermic oxidation reaction. By distributing this
heat in the ~oving stream, an increase in the bulk
temperature of the stream is provided. This increased
bulk temperature or ~reaction temperature" is the
temperature at which the rate of viscosity reduction is
substantially increased. The oxidation reaction is
controlled so that the increased bulk temperature
(reaction temperature) is below the coking temperature.
Maintaining the bulk temperature below the coking
temperature limits the temperature of the boundary layer
in the reactor vessel which prevents excessive formation
of coke on the walls of the reactor vessel.
The viscosity of a hydrocarbon feed can be
significantly reduced without the formation of
substantial coke deposits on the walls of the reactor
vessel. While the process of coking is not fully
understood, it has been reported that increased severity
of condit~ons increase coke formation. It is Xnown that
materials such as asphaltenes are more likely to form
coke. Once these materials precipitate and solidify on
surfaces, it is difficult to dissolve them before coke
deposits are formed. CoXe tends to build on the reactor
wall or other heating surface because in most systems
these surfaces must be heated significantly above the
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desired reaction temperature to attain bulk temperatures
sufficient to effect acceptable rates of viscosity
reduction. Such ~external heating" promotes coke
formation on reactor walls. As used herein, the term
"external heat source~ does not apply to the heat
provided to the influent stream by thermal communication
with the effluent product stream.
The direct oxidative heating process disclosed in
U.S. Patent 4,818,371 minimizes these problems
ass~ciated with external heating. The increment of heat
necessary to increase the bulk temperature of the stream
to effect substantially increased rates of viscosity
reduction is provided by internal heating through direct
oxidation of components in the core portion of the
stream. Consequently, coke formation on reactor walls
or other surfaces in the reactor vessel is substantially
reduced since these surfaces and the boundary layer of
feed adjacent to the surfaces are not heated above the
coking temperature.
While practice of the direct oxidative heating
process substantially reduces formation of coke on
reactor vessel walls, some coke formation can occur over
time. The amount of coke build-up is affected by the
type of feed, the quantity of feed which is processed as
well as process conditions. While some coke build-up
can be tolerated in most viscosity reduction processes,
the direct oxidative heating process is less sensitive
to coke formation than systems which rely entirely on
external heating. Coke formation on reactor walls
insulates the reactor and decreases the amount of heat
added to the stream by an external heat source. ~o
~aintain reguired temperatures ~or viscosity reduction,
external heat mUst be increased which causes additional
coke formation. However, there is a significant
advantage in the direct oxidative heating process since
coke formation in the reactor does not require
additional external heating because the final increment
of heat is provided internally. The amount of coke
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formation in such a process which would necessitate a
decoking procedure depends on the particular reaction
vessel in use and the point at which the operation
becomes impaired by coke buildup.
In the direct cxidative heating process, the
exothermic reaction is controlled so that the bulk
temperature remains below the coking temperature. It
should be appreciated that between the region in the
reactor vessel where the oxidation reaction occurs and
where mixing of the stream has achieved a substantially
uniform temperature throughout a cross-sectional segment
of the stream, localized temperatures above the coking
temperature can occur. Such temperatures can cause some
coke formation in the stream. These coke particles,
however, can be substantially prevented from adhering to
any surfaces by the physical action of the flow of the
stream.
The direct oxidative heating process of U.S. Patent
4,818,371 is broadly applicable to reducing the viscosity
of hydrocarbon feeds. The terms "hydrocarbon stream"
and ~hydrocarbon feed~ are used interchangeably herein
to mean a liquid stream which contains primarily
hydrocarbonaceous components but can also contain
smaller amounts of other components, for example, water.
This process is especially useful for treating heavy oil
crudes of a nature and viscosity which renders them
unsuitable for direct pipeline transport. This includes
feeds having a viscosity above about 1000 centipoise
(cp) at 25C (unless otherwise indicated, viscosity
referrred to herein is at 25C), a pour point above
about 15C or an API gravity at 25C of about 15 and
below. The advantages of reduced viscosity, increased
API gravity and/or reduced pour point can be achieved in
the instant apparatus without regard to the initial
viscosity, API gravity or pour point of the feed.
Additionally, if desired, a diluent can be added to the
feed strea~ or to the reaction product from the process
in order to further reduce the viscosity. Heating of
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the product in order to reduce the viscosity or maintain
an acceptable viscosity for a particular pipeline or
transportation medium is also possible.
Hydrocarbon feeds which can be used in the present
apparatus include, but are not limited to, heavy whole
crude oil, tarsands, bitumen, kerogen, and shale oils.
Examples of heavy crude oil are Venezuelan Boscan crude
oil, Canadian Cold Lake crude oil, Venezuelan Cerro
Negro crude oil and California Huntington Beach crude
oil. In practice, the most significant reductions in
viscosity are achieved when the starting feed is more
viscous.
The vertical tube reactor apparatus of the instant
invention has a heat exchange section, a combustion
zone, and a reaction zone. ~he heat exchange section is
adapted to provide for heat exchange between the
influent hydrocarbon feed stream and the effluent
product stream. The com~ustion zone is the region in
which oxidi2ing agent is introduced into the core
portion of the hydrocarbon stream and oxidizes
components in the stream. The reaction zone is the
region in which the bulk temperature of the hydrocarbon
stream is greater than the maximum temperature achieved
by heat exchange. There can be substantial overlap
between the combustion zone and the reaction zone.
In the direct oxidation process of Serial No.
058,878, the hydrocarbon feed stream comprising a core
portion and a boundary layer is introduced into the
inlet of the vertical tube reactor. The influent
hydrocarbon strea~ is at a first temperature (Tl) and an
initial pre~sure tP1)- As the influent hydrocarbon
stream travels down the influent conduit Df the vertical
tube reactor, the pressure increases due to the
hydrostatic column of fluid. Additionally, the
temperature of the influent stream increases to a second
temperature ~2) due to heat exchange with the e~fluent
product stream. An oxidizing agent is introduced into
the core portion of the hydrocarbon stream to increase
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the bulk temperature of the hydrocarbon stream to a pre-
selected reaction temperature (TrX).
It is preferred that the difference between the
second temperature and the reaction temperature is small
because less feed must be consumed in the oxidation
reaction to provide the necessary heat and fewer
oxidation products are formed. Additionally, the
greater the temperature difference, the larger the
combustion zone which is needed to provide the necessary
heat to increase the bulk temperature of the stream from
the second temperature to the reaction temperature. It
is preferred that the tempsrature increment between the
reaction temperature and the second temperature of the
hydrocarbon stream is less than about 35C and more
preferably less than about 25C.
In order to achieve the second temperature (T2)
necessary for the process to operate efficiently, it is
necessary for the heat exchange between the influent
hydrocarbon stream and the effluent product stream to be
more efficient than those disclosed in the known patents
relating to vertical tube reactors. The temperature of
the influent stream achievable by heat exchange with the
reaction product is limited by a number of factors
including the temperature of the reaction product, the
heat exchange surface area, and the velocities of the
hydrocarbon ctreams. In order to achieve the necessary
heat exchange efficiencies, it has been found that at
least one of and preferably both the influent feed
stream and the product stream are in substantially
vertical multiphase flow. It has been found that when
both streams are in substantially vertical multiphase
flow an increase in heat exchange efficiency of at least
about 100~ can be achieved compared to heat exchange
when neither stream is in multiphase flow. This allows
a second temperatUre ~T2) to be attained which is
sufficiently close to the necessary reaction temperature
to allow direct oxidative heating by introducing an
oxidizing agent.
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The oxidizing agent is a material which rapidly
exothermically oxidizes the ~ydrocarbon feed under
chosen reaction conditions. T~e agent is selected s~
that essentially all Df the age~t reacts with the feed.
Various oxidizing ag~nts are suitable for use in this
process. Such agents include, but are not limited to
oxygen and hydrogen peroxide. The oxidizing agent can
bè opti~nally mixed with a nonreactive gas, such as
nitrogen, and air or enriched air can be used in the
present process. Pref-erahly-e~r~c~ed air is used.
The amount of the oxidizing agent injected into the
hydrocarbon stream affects the amount of heat generated
by the oxidation reaction and is the primary factor for
controlling the temperature increase in the stream from
the Dxi~ation reaction. The amount of oxidizing agent
required ~or a particular volume of hydrocarbon feed in
operation ~f the invention can be substantially defined
with four variables: (1) the hea~ required to raise the
temperat~re o~ that volume o~ the feed from the second
tempersture to a reaction temperature, (2) the heat of
crao~ing ~f that volume of the feed, (3) the heat loss
from that volume of the feed to the environment in the
reaction zone, and ~4) the heat of combustion of the
particular feed. The sum of th~e first three of these
quantiti~ egual the amount o~ heat that must be
generat~d from the oxidation of some portion of the
feed. ~hD amount of feed which ~L~t be oxidized depends
on the heat of combust~cn of the particular feed.
With regard to the variables discussed above, it is
apparent that as the difference between the second
temperat~re and the reaction temperature increases an
increased flow rate of oxidizing agent is necessary to
generate additional heat by the oxidation of a larger
amount ~ the feed. As st~ted above, the amount of
oxidizing agent reyuired in the process is also
dependent on the heat of cra~king of the feed. This
characteristic i~ ~aria~le ~etween feeds. The oxidizing
agent flow rate is als~ a~*ected by heat loss from the
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hydrocarbon stream to the environment. A greater heat
1QSS requires more heat generation initially and,
therefore, the use of more oxidizing agent.
In the direct oxidative heating process, the amount
of oxidizing agent introduced to the reactor vessel is
used to control the oxidation reaction. The desired
flow rate for a given concentration can be estimated by
calculation using the variables discussed above. If the
exact value for each variable is known, the amount of
oxidizing agent required (assuming the heat of oxidation
is known) can be determined. In practice, these values
must ordinarily be estimated. Such an estimate can be
used to determine an initial flow rate of oxidizing
agent to use; however, actual control is based on a
measured variable such as the bulk temperature of the
hydrocarbon stream. The bulk temperature downstream
from the oxidation reaction is ordinarily monitored.
The bulk temperature should remain below the coking
temperature 80 that the reactor walls and boundary layer
are not heated to a temperature at which excessive coke
formation occurs. If the bulk temperature becomes too
high, the flow of oxidizing agent is reduced until the
preselected bulk temperature is attained. If the bulk
temperature i8 too low to achieve acceptable viscosity
reductiDn, the amount of oxidizing agent introduced into
the stream is increased until the appropriate reaction
temperature i8 attained. Monitoring the pressure in the
reaction zone can also be used to control the amount of
oxidizing agent introduced in*o the hydrocarbon stream.
The detection of pressure surges or fluctuations
indicates that the amount of oxidizing agent being
introduced into the hydrocarbon stream should be
decreased.
As used herein, the term nreaction temperature"
refers to the maximum bulk temperature of the
hydr~carbon stream reached in the process. It is
understood that some thermal cracking can occur at lower
temperatures. The term nreaction zone" refers to the
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region in the process which begins at the point theoxidizing agent is introduced and ends where heat
exchange between the reaction product effluent stream
a~d the influent hydrocarbon stream begins. The maximum
useful bulk temperature in the process is the coking
temperature of the particular feedstock. In ordinary
operation, the bulk temperature of the hydrocarbon
stream is maintained below the coking temperature. At a
minimum, the reaction temperature used for practice of
the process is high enough to initiate some thermal
cracking reaction. For most feeds, the reaction
temperature is above about 300C and less than about
475C, more typically in the range of about 350c to
about 450C, and more often in the range of about 375c
to about 435C.
The hydrocarbon stream in the reaction zone is
preferably maintained under a superatmospheric pressure
typically above about 1,000 pounds per square inch
absolute (psia). The high pressure serves to maintain
volatile components in the hydrocarbon stream in liquid
phase. The pressure also maintains products and by-
products from the oxidation reaction and thermal
cracking reaction in solution in the hydrocarbon stream.
It is important to maximize the liquid phase in the
reaction zone to minimize the concentration of
asphaltenes and other coke precursors to avoid their
precipitation from the hydrocarbon phase and possible
deposition on internal reactor surfaces with subsequent
coke formation. A small volume fraction of the stream
can be in vapor phase and, in fact, a small volume of
vapor phase can be beneficial in promoting mixing of the
stream for rapid distribution of heat from the oxidation
reaction throughout the core portion of the stream.
Preferably the ~apor phase should amount to no more than
about 10 volume percent of the hydrocarbon stream. If
the vapor pha~e comprises a substantial percent of the
stream volume, it can become difficult to maintain a
pressure balance in the reactor vessel.
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As discussed hereinabove, at least a portion of the
pressure on the hydrocarbon stream is achieved by a
hydrostatic column of fluid. If it is desired that the
reaction pressure be greater than that generated by the
hydrostatic head, the initial pressure of the
hydrocarbon feed stream can be increased by using a
pumping means for example, centrifugal or positive
displacement pumps, to provide the desired total
reaction pressure. The feed stream to the influent
conduit ~ay be pumped in one or more stages.
Upon introduction of the oxidizing agent into the
hydrocarbon stream, oxidation of components of the
stream occurs upon contact with the oxidizing agent. In
a localized area immediately downstream from
introduction of the agent, the temperature of the stream
can be substantially higher than the reaction
temperature because the oxidation reaction occurs
essentially upon contact of the agent with hydrocarbon
materials and is substantially complete before the heat
generated by the reaction is distributed in the stream.
The use of oxygen as the oxidizing agent results in
essentially a flame front in the hydrocarbon stream. It
is desirable to very guickly distribute the heat from
thè oxidation reaction throughout the core portion to
produce a su~stantially uniform temperature in the core
portion, i.e. essentially a uniform bulk temperature.
Mixing of the core portion ordinarily occurs essentially
immediately as a result of turbulent flow of the
hydrocarbon stream within the reaction vessel. If the
flow ~elocity of the stream is low enough that the
stream is in laminar flow, mixing can be induced with,
for example, static mixers.
The rate at which the oxidizing agent is introduced
into the hydrocarbon stream can be conveniently
expres6ed as an amount of oxidizing agent per unit
volume of the hydrocarbon stream. The flow rate of the
oxidizing agent is controlled so that the heat generated
by the oxidation reaction does not increase the bulk
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327952
temperature of the hydrocarbon stream above the coXingtemperature. For example, in a typical operation in
which the hydrocarbon stream comprises whole crude oil
and oxygen is the oxidizing agent, the flow rate of
oxygen is preferably less than about 40 scf/bbl
~standard cubic feet per barrel), more preferably less
than about 30 scf/bbl and most preferably less than
about 20 scf/bbl.
The primary gaseous product of the oxidation
reaction has been found to be carbon dioxide, which
correlates closely with introduction of oxygen to the
reactor. Other gases are also produced as by-products
of the present process; however, these appear to
correlate with temperature fluctuations in the stream
rather than the combustion reaction. The major
component of this gas make has been found to be methane,
although substantial amounts of carbon monoxide may be
present as well, with smaller amounts of ethane,
propane, hydrogen, carbon monoxide, and hydrogen sulfide
also being produced.
In the direct oxidative heating process, it is
important to maintain a positive pressure at the point
of introduction of the oxidizing agent into the stream.
Otherwise, the hydrocarbon feed can flow into the
oxidizing agent feedline possibly resulting in a violent
oxidation reaction. Safe operation of the process
therefore, requires that the oxidizing agent be at a
pressure greater than the pressure of the feed at the
point of injection. To maintain a positive oxidizing
agent flow and prevent the danger of hydrocarbon backup
into the oxidizing agent addition line, a pressure drop
across the i~jection nozzle of at least about 50 psi,
and ~ore preferably about 100 psi is preferred.
For safety reasons, it is also preferred to provide
sn emergency system in the event of a mechanical failure
in the injection system. Such an emergency system
floods the in~ection line with a non-reactive gas, such
as nitrogen, during an injection system failure to
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1327952
prevent hydrocarbon material from entering the injectionline and producing an explosive reaction with the
oxidizing agent.
The spatial placement of the oxidizing agent
injection nozzle can significantly affect the
temperature of regions of the boundary layer as well as
the reactor vessel wall. If the nozzle is placed within
the core portion of the hydrocarbon stream close to the
boundary layer, the resulting oxidation reaction can
heat the boundary layer and the reactor vessel and cause
substantial coke formation on the vessel. Likewise, if
the injection nozzle is placed centrally within the core
portion of the hydrocarbon stream but is directed toward
a reactor wall or other surface, the resulting reaction
can overheat the boundary layer and reactor vessel.
Another danger associated with placement of the
oxidizing agent injection nozzle is that if the nozzle
is too near the reactor vessel wall or is pointed toward
the reactor vessel wall, the oxidation reaction can
degrade or melt the wall causing a system failure. In
operation of the process, the oxidizing agent injection
nozzle is preferably in a substantially central position
in the core portion of the hydrocarbon stream and is
directed to provide a flow of oxidizing agent
substantially parallel to the ~low of the hydrocarbon
stream. This placement of the nozzle acts to localize
the oxidation reaction within the core portion of the
hydrocarbon stream away from the boundary layer, thereby
minimizing the temperature in the boundary layer.
The injection nozzle should also be oriented
relative to the flow of the hydrocarbon stream so that
heat generated ~y the oxidation reaction is carried away
~rom the nozzle to prevent thermal degradation of the
nozzle itself. Injection of the oxidizing agent in the
same direction as the flow of the hydrocarbon stream,
given a sufficient flow rate, successfully removes heat
from the nozzle.
.
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Heat loss to the outside environment from the
central portion of the stream outward is anticipated as
heat is generated internally by direct oxidative
heating. S~me heat loss can occur even if the reactor
vessel is insulated. Consequently, it may be necessary
to use multiple sites for introduction of oxidizing
agents to provide sufficient heat for viscosity
reduction or to maintain a given temperature for a
longer time than possible with a single injection site.
In this embodiment, the injection sites are spaced so
that as the bulk temperature of the stream falls below a
temperature at which acceptable viscosity reduction is
occurring, the stream passes another injection site to
provide additional heat.
The instant invention can be more readily under-
stood after a description of preferred embodiments. As
will be understood by those skilled in the art, other
apparatuses and configurations can be used in the
practice of the present invention.
Fig. 1 depicts a subterranean vertical reactor 2
disposed in a well bore 4. The term NverticalN is used
herein to mean that the tubular reactor is disposed
toward the earth's center. It is contemplated that the
tubular reactor can be oriented several degrees from
true vertical, i.e. normally within about 10 degrees.
The reactor can be disposed within the well bore
such that the outer reactor wall serves as the well
casing or such that an annulus 5 is formed between the
outer reactor wall and the bore wall. In the latter
embodi~ent, the well bore can be cased. In the
embodiment in which there is an annulus, heat loss to
the surrounding earth i8 minimized by filling the
annulus 5 with an insulating cement . Filling the
annular space with cement serves three purposes in
addition to insulating the reaction vessel: (1) it
supports the outer conduit vertically; (2) it isolates
the various formation zones and prevents communication
of fluids and hydrocarbons between them; and ~3) it
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fills the void space around the outer conduit and
prevents subsequent sloughing.
The influent and effluent conduits of the reactor
can be arranged as concentric inner conduit 10 and outer
conduit 14, with the influent and effluent conduits
comprising the inner and outer conduits respectively, or
alternately compri~ing the outer and inner conduits
respectively. These alternate configurations allow the
flow of the hydrocarbon stream to be in either
direction.
In the embodiment depicted in Figs. 1 and 3, the
outer conduit is closed at the bottom of the well bore
with a suitable material 7 such as cement. In the
embodiment of Fig. 2, t~e outer conduit is closed by an
end piece and is suspended such that it terminates above
the bottom of the well bore.
The inner conduit can terminate above the enclosure
material as depicted in Fig. 1, or it can terminate in
and be restrained by the enclosure material 7, as
depicted in Fig. 3. Alternately, the inner conduit can
connect with the end piece of the outer conduit as
illustrated in Fig. 2. In the Fig. 2 embodiment, the
inner conduit can either be attached to the end piece of
the outer conduit or be merely resting on it.
In any of the embodiments for the inner conduit,
thermal expansion during start up must be accommodated.
In the configuration of Fig. 3 in which the terminal
ends of the inner and outer conduits are restrained by a
material such as cement, the inner conduit is stressed
an amount equal to the thermal expansion expected during
warm up. Likewise, in the embodiment of Fig. 2 in which
the inner conduit is attached to the end piece of the
outer conduit, the inner conduit is stressed an amount
equal to the thermal expansion expected during warm up.
Such a construction allows the inner conduit to be in a
relaxed 6tate during operation of the thermal treatment
process. Fluid communication between inner and outer
conduits in Figs 2 and 3 is provided by the place~ent of
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327952
openings 13 in the inner conduit wall near the b~ttom of
the conduit.
In a preferred embodiment depicted in Fig. 1 in
which the inner conduit is suspended above the enclosure
material 7, thermal expansion is accommodated by
suspending the inner conduit such that it terminates a
sufficient distance above the outer conduit closure to
allow for thermal expansion during warm up. The
terminating and opening of the inner conduit provides
fluid communication between inner and outer conduits
during operation although additional openings in the
sides of the conduit can be provided as desired.
The preferred construction materials used for the
influent and effluent conduits depend on the nature of
the hydrocarbon feed and the particular operating
conditions. The hydrocarbon feed or crude can contain
corrosives, such as hydrogen sulfide, naphthenic acid,
polythionic and inorganic salts, or components that will
generate said acids and salts under the operating
conditions used. Additionally, the feed can contain
water which can increase corrosion particularly by
inorganic salts present in the feed. Corrosion by such
agents can be minimized by the selection of appropriate
materials. A combination of ~aterials may be necessary
to resist all corrosive agents present in a feed. The
acid and salt corrosion rates for construction materials
vary with te~perature.
For naphthenic acid corrosion, which is greatest at
temperatures above 450F, type 316L stainless steel,
which c~ntains molybdenum, is a preferred material of
construction. For polythionic acid corrosion, types 347
or 347H stabilized stainless steel are preferred
materials of construction. However, if both naphthenic
and polythionic acid corrosion are of concern, then type
316L is a preferred construction material. For
inorganic salt corrosion, which is normally greatest in
areas of water phase separation, Monel is a preferred
material of construction. Water phase separation is
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1327952
more likely at those depths of the reactor where the
hydrostatic pressure is sufficient to liquify water
vapor, even though temperatures can be 200c to 450c.
If the hydrocarbon feed contains hydrogen sulfide,
naphthenic acid, polythionic and inorganic salts, and
water phase separation is likely, the following
materials are preferred:
- in high temperature regions (at least 450F),
type 316 L stainless steel;
- in low temperature regions (below 45~F), at
depths where water phase separation is likely,
Monel; and
- in low temperature regions (below 450F) at
depths where water phase separation d~es not
exceed 10% by weight of the stream, carbon
steel.
If the hydrocarbon feed contains hydrogen sulfide,
naphthenic acid, polythionic acid and inorganic salts,
but no more than 10~ water phase separation is
anticipated, the following materials can be used:
- in high temperature regions (at least 450F),
type 316L stainless steel; and
- in low temperature regions ~below 450F),
carbon steel or 316L stainless steel. ;
Although either carbon steel or 316L can be used in
low temperature regions, use of 316L minimizes the
replacement of equipment due to corrosion.
In a preferred embodiment depicted in Fig. i, the
outer effluent conduit 14 is concentrically arranged
around the inner influent conduit 10. The flow of the
untreated hydrocarbon feed stream is directed through
liné 6 and into influent conduit 10 to the reaction zone
12 and up the concentric effluent conduit 14. This
arrangement provides for heat exchange between the
outgoing product stream and the incoming feed stream.
During start up, untreated hydrocarbon feed is
introduced into the vertical tube reactor system through
feed inlet 6, the flow rate being controlled by a
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metering means such as valve 8. The hydrocarbon feed
stream passes through influent conduit lo into reaction
zone 12 and up through concentric effluent conduit 14
exiting through discharge line 16. During this
operation unless external heat is provided to the
hydrocarbon feed stream, the initial temperature Tl is
e~ual to the final heat exchange temperature T2 and i5
also equal to the maximum temperature in the reaction
zone TrX (assuming no heat loss to the environment).
In order to achieve the necessary temperature T2 at
which oxidant can advantageously be introduced, the
hydrocarbon stream is heated. This heating can be
accomplished by an abo~e-ground heating means 18. The
heating means may be any of a variety of heaters known
to those skilled in the art, such as a fired heater
which uses gaseous fuel recovered in the surface
facilities and/or supplemental fuel. The necessary heat
can also be provided by an external heating means 20
surrounding the reaction zone. Preferably, external
heating means 20 is a jacket surrounding the reaction
zone through which a heat exchange fluid is passed
through inlet line 24 and outlet line 26. Normally,
this mode of operation is used when the outer conduit
receives the influent stream. In another configuration
not shown, the influent conduit io can also be jacketed
to allow external heating of the hydrocarbon stream at
this location in addition to or instead of heating the
reaction zone. Alternatively, the external heating
means 20 can be used in conjunction with the above
ground heating means 18 to provide the hydrocarbon feed
stream at the desired temperature T2. Normally, the
feed stream is recycled through the vertical reactor
until the desired temperature (T2) is reached.
The temperature of the hydrocarbon stream is
determined by temperature monitors 30 which can be
located in the hydrocarbon stream throughout the
vertical tube reactor system. Under normal operating
conditions, it is preferred that there be one
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1327952
temperature monitor l~cated downstream of each injector
within the reaction zone.
As the hydrocarbon stream passes down through
influent conduit l0, pressure on any particular volume
segment increases due to the hydrostatic column of fluid
above that volume segment in the stream. Under normal
operatinq conditions, it is preferred that no pressure
monitors be located within the reaction zone. Instead,
pressure is preferably monitored at pressure monitors 28
located at the inlet and/or outlet of the reactor. The
pressure in the reaction zone can be calculated by
summing the pressure at the reactor inlet or outlet and
the pressure exerted by the hydrostatic column of fluid
at the depth corresponding to the reaction zone. The
pressure exerted by the hydrostatic column can be
readily calculated by a skilled artisan.
Once the desired temperature T2 has been attained
by external heating of the hydrocarbon stream, oxidant
is introduced through line 34 and nozzles 32 to provide
the incremental heat necessary to reach the desired
reaction temperature.
The nozzles for introducing the oxidizing agent are
arranged in the conduits according to the desired method
of operation. If the influent or effluent conduits are
the outer and inner conduits respectively, the nozzles
can be placed in one or both of the influent and/or
effluent conduits. Alternately, if the influent and
effluent conduits are the inner and outer conduits
respectively, the nozzles can be placed in one or ~oth
of the influent and/or effluent conduits. In each of
these embodiments, the orientation of the oxidant
in~ectlon nozzle are in the direction of flow of the
hydrocarbon stream. In the preferred embodiment of Fig.
1, the effluent conduit is the outer concentric conduit
14 and the oxidant is directed upward into the upflowing
hydrocarbon stream in the effluent conduit at nozzles
32.
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1327952
Flow rate of the oxidant is controlled by a
metering means such as valve 36 which in turn can be
controlled directly or indirectly by output from
selected temperature monitors 30 and/or pressure
monitors 2~. Output from temperature monitor 30 and
pressure monitor 28 can also be used to control,
directly or indirectly, other factors that determine
temperature. These can include the temperature of media
in the jacXet 20 providing external heat to the reaction
zone and/or the influent hydrocar~on stream pump rate.
Temperature ~onitors are typically thermocouple devices.
A means can be provided for receiving a signal from the
thermocouple and adjusting the oxidizing agent metering
means to adjust the flow of oxidizing agent in order to
maintain the temperature of the hydrocarbon stream in
the reaction zone within a preselected range of
temperatures. Although manual adjustment can be used
for controlling oxidant flow, automated adjusting or
metering means is preferred. For example, a
proportional controller with reset or a proportional
integrated controller can be used.
The number of nozzles in the reaction zone is
determined by the guantity of heat required to produce
the desired increase in temperature from T2 to Trx. The
demand for a high rate of product output (short transit
time in the reaction zone) and/or for a significant
reduction in ~iscosity requires a greater input of heat
energy. To provide greater heat input, a plurality of
oxidant injection nozzles can be employed. Additional
oxidant injection nozzles 38 can be provided downstream
from the initial nozzles 32. The downstream nozzles are
sufficiently distanced downstream from upstream nozzles
to avoid damage from the flamefront associated with
upstream nozzles. Vnder normal operating conditions, it
is expected that about three to ten nozzles are located
in the reaction zone. In a preferred embodiment
depicted in Fig. 1, the initial nozzles 32 are located
near the bottom of the effluent conduit 14. Additional
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3279~2
nozzles 38 can be located downstream of the initialnozzles. This configuration provides the advantage that
vapor phase regions formed during the oxidation reaction
readily flow upward with the product stream. In an
embodiment where the nozzles are placed in the influent
c~nduit, static or slowly moving vapor phase regions or
bubbles could be formed in the influent conduit. This
could disrupt flow of the hydrocarbon stream, cause
pressure fluctuations, and/or result in reduced heat
exchange.
The material used in the construction of the
nozzles depends on the operating temperature in the
reaction zone and the corrosion as well as the erosion
characteristics of the feedstream. ~or example, 316L
steel can be used where naphthenic acid corrosion is of
concern. Other materials which can be used to prepare
the nozzle or the nozzle tip include ceramics and
tungsten carbide materials.
As discussed hereinabove, for safety reasons it is
important to maintain a positive pressure in line 34
relative to the pressure of the hydrocarbon at the
oxidant injection nozzle. This prevents hydrocarbon
feed from flowing into the oxidizing agent feed line 34
possibly resulting in a violent oxidation reaction.
Therefore, the oxidizing agent should be at a pressure
greater than the pressure of the hydrocarbon feed at the
point of in;ection. Nitrogen can be introduced into
line 34 through line 42 with the flow being controlled
by a metering means such as valve 44. Ordinarily, in
operation line 34 is purged with nitrogen prior to
introduction of oxidizing agent. For safety purposes,
an emergency system can be provided in which valve 44 is
activated and non-reactive gas introduced into line 34
in the event oxidant flow is interrupted. Normally, a
device such as a check valve 40 is present in the line
34 to prevent reverse flow of feed into the oxidant
supply. A means for detecting oxidant flow rate can
also be placed in line 34. Oxidant flow rate is
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13279~2
typically determined ~y measuring the change in pressureover a segment of oxidant line 34 at or near the
surface.
The oxidant conduits that supply oxidizing agent to
the nozzles c~n be arranged in any convenient
configuration. In the embodiment of Fig. 1, oxidant
conduit 34 is positi~ned along the external surface of
the reactor outer conduit to the level at which the
nozzles are placed. At this point, the oxidant conduit
penetrates the reactor outer conduit wall and connects
with the nozzles. In the event the nozzles are located
within the reactor inner conduit, the oxidant conduit
penetrates the reactor inner conduit wall.
In another em~odiment, the oxidant conduit
traverses the external surface of the reactor inner
conduit until it reaches nozzle level, at which point it
extends to and connects with the nozzle. The oxidant
conduit penetrates the wall reactor inner conduit if a
nozzle is loca~d in ~e inner conduit.
In a third, more-preferre~ embodiment illustrated
in Fig. 3, the oxidant conduit is positioned down the
inside of the reactor inner conduit. The oxidant
conduit branches at the level at which a nozzle is
located and connects therewith. Other embodiments for
positionin~ the oxidant conduit will be apparent to
those skilled in the art and are encompassed herein.
A preferred construction material for the oxidant
conduits is moly~num ~Dn*aining Inconel 625 because of
its corrosion resistance to an aqueous, high temperature
environment containing 2 Due to its molybdenum
content, Inconel 625 also has resistance to naphthenic
acid corrosion.
The temperature of the effluent product stream can
be lower than ~he reaction temperature when it initially
comes in heat exchange contact ~ith the influent stream
due to some heat loss to the environment. The
temperature of the effluent product stream is
continually decreased ~y thermal communication with the
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influent stream until a final temperature (Tf) is
attained as the effluent exit~ the reactor system.
The effluent hydrocarbon stream passes upward
through effluent conduit 14 and out of heat exchange
contact with influent hydrocarbon feed stream exiting
the reactor through line 16~ The product can pass to a
sepasation/compression unit 46 in which carbon dioxide
and other gases are separated from liquid product and a
more volatile fraction of the hydrocarbon stream can
also be segregated. The separation/compression unit 46
is a combination of separators and compressors operated
at selected temperatures and presures for the purpose of
separating desired gaseous and liquid hydrocarbon
fractions. Volatile components usuall~ boiling below
about 40C can be recycled through line 48 into the
influent hydrocarbon feed stream. This can be done to
induce vertical multiphase flow in the influent stream
to substantially increase the efficiency of heat
exchange between the influent and effluent streams. The
volatile liquid fraction recycled to the influent
conduit is of a composition such that it is in the
gaseous phase under pressure existing during the heat
exchange process between the influent and effluent
streams and in a liquid phase under the greater
pressures existing below the heat exchange area in the
reaction zone.
During start up when external heat is being
supplied to increase the temperature of the hydrocarbon
stream, the complete stream can be recycled, for
example, through line 48 in order to minimize the total
volume of hydrocarbon which must be heated by external
means. When the desired temperature T2 has been
attained f~r the hydrocarbon stream in the reactor
system, heat from the external heat source can be
terminated. In Fig. 3, the effluent stream is brought
into thermal communication with the influent stream in
an above-ground heat exchanger 19 to provide a higher
initi~l temperature of the influent stream. The above-
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13279~2
ground heat exchanger additionally provides a safety
mechanism in the event of fouling downstream in the
reactor vessel. The above-ground exchanger can be any
of a variety of exchangers known to those skilled in the
art, including a shell-and-tube exchanger. Shell-and-
tube exchanger construction material can be carbon steel
if the operating temperature of the exchanger is below
450F. If the operating temperature is above 450F, the
shell can be composed of carbon steel overlaid with type
316L, and the tubes can be composed entirely of 316L.
Fig. 2 depicts an embodiment in which the flow of
the hydrocarbon stream is in the opposite direction from
that of Figs. 1 and 3. The outer conduit functions as
an influent conduit 10, while the inner conduit
functions as an effluent conduit 14. Fig. 2 also
differs from Fig. 1 in that the inner conduit 14 is
connected to an end piece 11 which closes the terminal
end of the outer conduit 10. The terminal end of the
inner conduit 14 may merely rest on end piece 11 or may
be detachably fixed thereto. Fixing the inner conduit
to the end piece in a detachable manner allows for
removal of the inner conduit from the reactor for
cleaning purposes. The inner conduit can be detachably
affixed to the end piece using for example, a female
threaded coupling device formed in the end piece and
adapted to recei~e and retain the threaded terminal end
of the inner conduit. -
Insulating cement 9 is depicted in the annulus
between the well bore wall 4 and the outer influent
conduit 10. Oxidant nozzles 32 are located in the
effluent conduit 14, but may alternately be located in
both the effluent conduit 14 and influent conduit 10, as
indicated by the placement of phantom nozzle 33 in the
influent nozzle 10. The location of the phantom nozzle
is representative only and not definiti~e with respect
to actual or relative location. Actual location would
be determined by the desired span of the reaction zone.
.
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1327952
Fig. 2A depicts a mechanism for controlling the
oxidant flow rate in response to temperature monitor
output shown in association with Fig. 2. Symbols "Al"
and ~A2~ represent points of relation between Figs. 2
and 2A. Flow controller 35 receives a signal from the
temperature detector thermocouples 30 of Fig. 2 and
adjusts the metering means 37 on oxidant line 34. As
output from the thermocouples 30 indicates excessive
temperatures in the reaction zone, flow controller 35
sends a signal to metering means 37 to reduce oxidant
flow rate. As output from the thermocouples 30
indicates reaction zone temperatures below a preselected
range, flow controller 35 activates the metering means
37 to increase oxidant flow rate. Also depicted in Fig.
2A is a gas analyzer 39 connected to means for
differential control 41 of oxygen to nitrogen ratio in
the oxidant supply line. In response to quantitative
analysis of gases in line 34, the means for differential
control 41 of oxygen and nitrogen adjusts valves 36 and
44 to bring the rativ of said gases into a preselected
range. A vent mechanism 43, controlled by a pressure
sensor 45 on line 34, is activated to release gases from
line 34 when t~e pressure therein exceeds a preselected
limit.
Fig. 2B depicts the surface facilities associated
with the reactor embodiment of Fig. 2. Symbols nBlN and
~B2~ represent points of relation between Figs. 2 and
2B. Above-ground heat exchanger 19 brings incoming
hydrocarbon feed in line 6 into heat exchange contact
with the ef~luent product stream. Product stream in
line 16 then enters the separation/compression unit 46
for separation of a volatile fraction from the liquid
product. The volatile fraction can be recycled through
line 4~ to influent conduit 14 to induce vertical
multiphase flow in the influent stream to substantially
increase the efficiency of heat exchange in the reactor
between the influent and effluent streams.
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In the embodiment of Fig. 3, the flow of the
hydrocarbon stream is the same as in Fig. 1. Fig. 3
features an above ground heat exchanger 19 that brings
effluent and influent streams into heat exchange contact
outside of the reactor itself. The oxidant supply line .-
34 of Fig. 3 travels within and substantially parallel
to the influent conduit 10 and branches at appropriate
depths to supply nozzles 32 and 38. Oxidant control
valve 44 allows for control of the oxidant flow rate at
nozzles 32 and 38. Check valve 40 on oxidant supply
line 34 is present to prevent reverse flow of
hydrocarbon feed into the oxidant supply.
While various embodiments of the present invention
have been described in detail, it is apparent that
modifications and adaptations will occur to those
skilled in the art. However, it is to be expressly
understood that such modifications and adaptations are
within the spirit and scope of the present invention, as
set forth in the following claims.
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