U.S. patent application number 11/428478 was filed with the patent office on 2007-01-18 for systems and methods for producing synthesis gas.
Invention is credited to Gerard Grootveld, Pieter Lammert Zuideveld.
Application Number | 20070011945 11/428478 |
Document ID | / |
Family ID | 35427328 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070011945 |
Kind Code |
A1 |
Grootveld; Gerard ; et
al. |
January 18, 2007 |
SYSTEMS AND METHODS FOR PRODUCING SYNTHESIS GAS
Abstract
The present invention relates to a system for producing
synthesis gas comprising CO and H.sub.2. The system comprises a
first gasification reactor and a second gasification reactor. The
first one has an inlet for a first oxygen containing stream, an
inlet for a first carbonaceous stream, and an outlet for raw
synthesis gas produced in the first gasification reactor. The
second one has an inlet for a second oxygen containing stream, an
inlet for a second carbonaceous stream, and an outlet for raw
synthesis gas produced in the second gasification reactor. A source
of an oxygen containing stream is selectively connected to the
inlet for the first oxygen containing stream of the first
gasification reactor and to the inlet for the second oxygen
containing stream of the second gasification reactor via a
distributor.
Inventors: |
Grootveld; Gerard;
(Amsterdam, NL) ; Zuideveld; Pieter Lammert;
(Amsterdam, NL) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
35427328 |
Appl. No.: |
11/428478 |
Filed: |
July 3, 2006 |
Current U.S.
Class: |
48/197R ;
48/61 |
Current CPC
Class: |
C01B 13/0229 20130101;
C01B 2203/1241 20130101; C01B 2210/0046 20130101; C10J 2300/093
20130101; C01B 3/36 20130101; C10K 3/04 20130101; C01B 2203/025
20130101; C01B 2203/065 20130101; C01B 2203/0283 20130101; C10J
3/723 20130101; C01B 2203/141 20130101; C10J 2300/0959 20130101;
C10K 1/08 20130101; Y02P 30/00 20151101; Y02P 30/30 20151101; C10J
3/00 20130101; C10J 3/721 20130101; C01B 2203/84 20130101; C01B
2203/86 20130101; C01B 2210/0082 20130101; C01B 3/48 20130101 |
Class at
Publication: |
048/197.00R ;
048/061 |
International
Class: |
C10J 3/46 20060101
C10J003/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 5, 2005 |
EP |
05106072.1 |
Claims
1. A system for producing synthesis gas comprising CO and H.sub.2,
the system comprising: a first gasification reactor comprising a
first-reactor oxygen inlet for a first oxygen-containing stream, a
first-reactor fuel inlet for a first, carbonaceous stream, and a
first-reactor outlet for raw synthesis gas produced in the first
gasification reactor; a second gasification reactor comprising a
second-reactor oxygen inlet for a second oxygen-containing stream,
a second-reactor fuel inlet for a second carbonaceous stream, and a
second-reactor outlet for raw synthesis gas produced in the second
gasification reactor; an oxygen source of an oxygen containing
stream; and a distributor for fluidly connecting the oxygen source
to the first-reactor oxygen inlet and to the second-reactor oxygen
inlet, the distributor being arranged to selectively connect the
oxygen source to the first or second gasification reactor.
2. The system of claim 1, wherein the oxygen-containing stream
comprises greater than 50 vol. % O.sub.2.
3. The system of claim 1, wherein the oxygen-containing stream
comprises greater than 99 vol. % O.sub.2.
4. The system of claim 1, wherein the first carbonaceous stream is
selected from the group consisting of a particulate and a liquid
stream and the second carbonaceous stream is selected from a group
consisting of a gaseous and liquid stream and a mixture
thereof.
5. The system of claim 1, wherein the first carbonaceous stream is
a particulate stream.
6. The system of claim 5, wherein the second carbonaceous stream is
a gaseous stream.
7. The system of claim 1, wherein the second carbonaceous stream is
a gaseous stream.
8. The system of claim 7, wherein the first carbonaceous stream is
a liquid stream.
9. The system of claim 1, wherein the oxygen source comprises an
air separation unit having a maximum oxygen capacity of less than
80% of the sum of the oxygen requirements for the first and the
second gasification reactors.
10. The system of claim 9, wherein the maximum oxygen capacity of
the air separation unit is less than 65% of the sum of the oxygen
requirements for the first and the second gasification
reactors.
11. The system of claim 1, further comprising a second first
gasification reactor.
12. The system of claim 1, further comprising a shift converter
being connected to the first-reactor outlet and the second-reactor
outlet, in which shift converter at least a part of the CO in the
synthesis gas may be reacted to produce CO.sub.2 and H.sub.2.
13. A method of producing synthesis gas comprising CO and H.sub.2,
from a carbonaceous stream using an oxygen-containing stream, the
method comprising the steps of: (a) injecting a first carbonaceous
stream and a first oxygen containing stream into a first
gasification reactor, the first oxygen-containing stream
originating from a source of oxygen; (b) at least partially
oxidising the first carbonaceous stream in the first gasification
reactor, thereby obtaining a first raw synthesis gas; (c) removing
the first raw synthesis gas obtained in step (b) from the first
gasification reactor; (d) injecting a second carbonaceous stream
and a second oxygen-containing stream into a second gasification
reactor, and wherein the second oxygen containing stream originates
from the source of oxygen used in step (a); (e) at least partially
oxidising the second carbonaceous stream in the second gasification
reactor, thereby obtaining a second raw synthesis gas; and (f)
removing the second raw synthesis gas obtained in step (e) from the
second gasification reactor; wherein the first and second
gasification reactors are used alternately.
14. The method of claim 13, wherein the oxygen containing stream
comprises greater than 50 vol. % O.sub.2.
15. The method of claim 13, wherein the oxygen containing stream
comprises greater than 99 vol. % O.sub.2.
16. The method of claim 13, wherein the first carbonaceous stream
is selected from a group consisting of a particulate and a liquid
stream and the second carbonaceous stream is selected from a group
consisting of a gaseous and liquid stream and a mixture
thereof.
17. The method of claim 13, wherein the first carbonaceous stream
is a particulate stream.
18. The method of claim 17, wherein the second carbonaceous stream
is a gaseous stream.
19. The method of claim 13, wherein the second carbonaceous stream
is a gaseous stream.
20. The method of claim 19, wherein the first carbonaceous stream
is a liquid stream.
21. The method of claim 13, further comprising the steps of: (g)
transporting at least one of the first synthesis gas removed in
step (c) and the second synthesis gas removed in step (f) to a
shift converter; and (h) reacting at least a part of the CO
comprised in the at least one of the first and second synthesis gas
transported in step (g) to produce CO.sub.2 and H.sub.2.
22. A method using a spare gasification reactor in a process to
generate power from a source of petroleum coke in one or more
parallel operated gasification reactors, which spare reactor is
capable of preparing a spare synthesis gas mixture comprising
carbon monoxide and hydrogen by partial oxidation of at least one
of a vacuum residue and natural gas, using up to a maximum first
volume of oxygen per hour as obtained from an air separation unit,
and wherein power is generated from the petroleum coke by (aa)
partial oxidation of the petroleum coke using up to a maximum
second volume of oxygen per hour as obtained from the air
separation unit, to yield a synthesis gas mixture, (bb) using at
least one of the synthesis gas mixture as obtained from step (aa)
and the optional spare synthesis gas mixture to generate power
wherein a maximum capacity of the air separation unit is less than
the sum of the maximum first and second oxygen volumes per
hour.
23. The method of claim 22, further comprising a step of isolating
carbon dioxide prior to the power generation.
24. The method of claim 23, wherein the carbon dioxide is isolated
in a gas turbine.
25. The method of claim 22 carried out in the system of claim
1.
26. A process to prepare hydrogen from a source of petroleum coke
in one or more parallel operated gasification reactors employing a
spare gasification reactor, which spare reactor is capable of
preparing an optional spare synthesis gas mixture comprising carbon
monoxide and hydrogen, by partial oxidation of at least one of a
vacuum residue and natural gas, using up to a maximum first volume
of oxygen per hour as obtained from an air separation unit, and
wherein hydrogen is prepared from the petroleum coke by (aa1)
partial oxidation of the petroleum coke using up to a maximum
second volume of oxygen per hour as obtained from the air
separation unit to yield a synthesis gas mixture, (bb1) subjecting
at least one of the synthesis gas mixture as obtained from step
(aa1) and the optional spare synthesis gas mixture to a water gas
shift step to obtain shifted gas, (cc1) subjecting the shifted gas
to a gas separation step to obtain a hydrogen enriched mixture,
wherein the maximum capacity of the air separation unit is less
than the sum of the maximum first and second oxygen volumes per
hour.
27. The process of claim 26, wherein the gas separation step
comprises a pressure swing absorbing process.
28. The process of claim 26 carried out in the system of claim 1.
Description
CROSS REFERENCE TO AN EARLIER APPLICATION
[0001] Priority is claimed of European patent application No.
05106072.1 filed Jul. 5, 2005.
FIELD OF THE INVENTION
[0002] The present invention relates to systems and methods for
producing synthesis gas comprising CO and H.sub.2 from a
carbonaceous stream using an oxygen containing stream.
BACKGROUND OF THE INVENTION
[0003] Generally in such systems and methods, a carbonaceous stream
such as coal, brown coal, peat, wood, coke, soot, or other gaseous,
liquid or solid fuel or mixture thereof, is partially combusted in
a gasification reactor using an oxygen containing gas such as
substantially pure oxygen or (optionally oxygen enriched) air or
the like, thereby obtaining synthesis gas (CO and H.sub.2),
CO.sub.2 and optionally a slag. In case where slag is formed during
the partial combustion, it drops down and is drained through an
outlet located at or near the reactor bottom.
[0004] The hot product gas, which may be referred to as raw
synthesis gas, is typically quenched in a quench section which is
located downstream of the gasification reactor. In the quench
section a suitable quench medium such as water, cold gas, recycled
synthesis gas or the like is introduced into the raw synthesis gas
in order to cool it.
[0005] After the quenching, the raw synthesis gas is further
processed, e.g. to remove undesired components from it or to
convert the CO into methanol and various other hydrocarbons. The
H.sub.2 may be used a product gas or used for e.g. hydrocracking
purposes.
[0006] WO-A-99/55618 describes a process to prepare a synthesis gas
by means of two parallel-operated processes. One process is the
partial oxidation, also referred to as gasification, of a biomass
feed. In the parallel process, a natural gas is used as feed for a
steam reforming process. Synthesis gas mixtures from both processes
are combined.
[0007] WO-A-02/090250 describes a process to prepare a synthesis
gas by means of two parallel-operated partial oxidation processes.
In one process a solid or liquid feed is used as feed and in the
parallel process a natural gas is used as feed. Synthesis gas
mixtures from both processes are combined.
[0008] Known gasification reactors which operate on a liquid and
especially on a solid feed, such as coal as in WO-A-02/090250,
usually have a relative low availability. After a certain operating
period, the reactor typically has to be shut down for a while, to
check and repair the internals, if necessary. As a result no
synthesis gas is produced for a while, or the syngas production is
substantially halved as would be in the case of the process of
WO-A-02/090250.
[0009] The above problem is even more pertinent in cases where the
gasification reactor uses a particulate carbonaceous feed stream,
such as coal and especially petroleum coke, that is intended to
produce H.sub.2 as the main product. If the gasification process is
applied in a refinery environment, using petroleum coke as the feed
to the gasification process, a high H.sub.2 availability, usually
greater than 98% of the year, and/or a high synthesis gas
availability for generating power is desired. Hydrogen is used for
the various refinery processes such as hydrotreating,
hydrofinishing, hydrocracking and catalytic dewaxing. Disruptions
in either the hydrogen or the power supply in a refinery is not
desired. It is an object of the present invention to at least
minimize the above problem.
[0010] It is a further object to provide a system ensuring a high
availability of synthesis gas, while using as few components as
possible.
[0011] It is an even further object to provide an alternative
system for producing synthesis gas.
SUMMARY OF THE INVENTION
[0012] The present invention provides a system for producing
synthesis gas comprising CO and H.sub.2, the system comprising
first and second gasification reactors.
[0013] The first gasification reactor may comprise a first-reactor
oxygen inlet for a first oxygen-containing stream, a first-reactor
fuel inlet for a first, carbonaceous stream, and a first-reactor
outlet for raw synthesis gas produced in the first gasification
reactor.
[0014] The second gasification reactor may comprise a
second-reactor oxygen inlet for a second oxygen-containing stream,
a second-reactor fuel inlet for a second carbonaceous stream, and a
second-reactor outlet for raw synthesis gas produced in the second
gasification reactor.
[0015] The system further comprises an oxygen source of an oxygen
containing stream and a distributor for fluidly connecting the
oxygen source to the first-reactor oxygen inlet and to the
second-reactor oxygen inlet, the distributor being arranged to
selectively connect the oxygen source to the first or second
gasification reactor.
[0016] In another aspect the present invention provides a method of
producing synthesis gas comprising CO and H.sub.2, from a
carbonaceous stream using an oxygen-containing stream, the method
comprising at least the steps of: [0017] (a) injecting a first
carbonaceous stream and a first oxygen containing stream into a
first gasification reactor, the first oxygen-containing stream
originating from a source of oxygen; [0018] (b) at least partially
oxidising the first carbonaceous stream in the first gasification
reactor, thereby obtaining a first raw synthesis gas; [0019] (c)
removing the first raw synthesis gas obtained in step [0020] (b)
from the first gasification reactor; [0021] (d) injecting a second
carbonaceous stream and a second oxygen-containing stream into a
second gasification reactor, wherein the second oxygen containing
stream originates from the source of oxygen used in step (a);
[0022] (e) at least partially oxidising the second carbonaceous
stream in the second gasification reactor, thereby obtaining a
second raw synthesis gas; [0023] (f) removing the second raw
synthesis gas obtained in step (e) from the second gasification
reactor.
[0024] The first and second gasification reactors may function at
the same time, but it is especially preferred that the first and
second gasification reactors are used alternately.
[0025] The method may further comprise optional steps of: [0026]
(g) transporting the first synthesis gas removed in step (c) or the
second synthesis gas removed in step (f) to a shift converter; and
[0027] (h) reacting at least a part of the CO in the first or
second synthesis gas transported in step (g) in the shift converter
to produce CO.sub.2 and H.sub.2.
[0028] The first carbonaceous stream may comprise a particulate
carbonaceous stream which may comprise a petroleum coke.
[0029] The second carbonaceous feed may be a gaseous stream which
may comprise at least one of the vacuum residue feed of the coking
process and natural gas, preferably natural gas.
[0030] The invention further provides a method using a spare
gasification reactor in a process to generate power from a source
of petroleum coke in one or more parallel operated gasification
reactors, which spare reactor is capable of preparing a spare
synthesis gas mixture comprising carbon monoxide and hydrogen by
partial oxidation of at least one of a vacuum residue and natural
gas, using up to a maximum first volume of oxygen per hour as
obtained from an air separation unit.
[0031] Power generation based on petroleum coke may then optionally
be obtained by [0032] (aa) partial oxidation of the petroleum coke
using up to a maximum second volume of oxygen per hour as obtained
from the air separation unit, to yield a synthesis gas mixture,
[0033] (bb) using at least one of the synthesis gas mixture as
obtained from step (aa) and the optional spare synthesis gas
mixture to generate power.
[0034] Carbon dioxide may advantageously be isolated prior to the
power generation in, for example, a gas turbine. Carbon dioxide may
be subjected to sequestration or suitably used for agricultural
uses or enhanced oil recovery.
[0035] Hydrogen may optionally be obtained in said preferred
embodiment from the petroleum coke by [0036] (aa1) partial
oxidation of the petroleum coke using up to a maximum second volume
of oxygen per hour as obtained from the air separation unit to
yield a synthesis gas mixture, [0037] (bb1) subjecting at least one
of the synthesis gas mixture as obtained from step (aa1) and the
optional spare synthesis gas mixture to a water gas shift step to
obtain shifted gas, [0038] (cc1) subjecting the shifted gas to a
gas separation step to obtain a hydrogen enriched mixture.
[0039] The gas separation step may comprise or consist of a
pressure swing absorbing process (PSA).
[0040] Irrespective of whether power is generated and/or hydrogen
produced, the maximum capacity of the air separation unit is
preferably less than the sum of the maximum first and second oxygen
volumes per hour.
[0041] The invention will hereinafter be illustrated by way of
example in more detail with reference to the accompanying
non-limiting drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0042] In the accompanying drawing:
[0043] FIG. 1 schematically shows a process scheme for performing a
method according the present invention.
[0044] For the purpose of this description, a single reference
number will be assigned to a line as well as a stream carried in
that line. Same reference numbers refer to similar components.
DETAILED DESCRIPTION
[0045] Reference is made to FIG. 1. FIG. 1 schematically shows a
system 1 for producing synthesis gas.
[0046] The system 1 comprises a first gasification reactor 2, a
second gasification reactor 3, an oxygen source 4 and a shift
converter 5. In the embodiment shown in FIG. 1, the first
gasification reactor 2 is a coal gasification reactor and the
second gasification reactor 3 is a gas gasification reactor.
[0047] In the system 1 according to FIG. 1 a particulate coal
containing stream 10 and an oxygen containing stream 60 are fed at
inlets 6 and 7, respectively, into the coal gasification reactor
2.
[0048] Similarly, a gas containing stream 30 and an oxygen
containing stream are 70 are fed into the gas gasification reactor
3 at inlets 9 and 11.
[0049] During normal use of the embodiment of FIG. 1 only the coal
gasification reactor 2 is in function; the gas gasification reactor
3 functions as a spare unit for producing synthesis gas in case the
coal gasification reactor 2 is out of order or on hot standby.
[0050] If the coal gasification reactor 2 is functioning, the
oxygen source 4 feeds an oxygen containing stream 50 to the
distributor 25 which selectively connects the source 4 to the coal
gasification reactor 2 via lines 50 and 60. At this point no oxygen
is fed to the gas gasification reactor 3.
[0051] The carbonaceous stream 10 is partially oxidised in the
gasification reactor 2 thereby obtaining raw synthesis gas 20
(removed via outlet 8) and a slag (removed via stream 90). To this
end usually several burners (not shown) are present in the
gasification reactor 2.
[0052] The synthesis gas 20 produced in the coal gasification
reactor 2 is usually fed to a quenching section (not shown); herein
the raw synthesis gas is usually cooled.
[0053] As shown in the embodiment of FIG. 1, the synthesis gas 20
leaving the reactor 2 at outlet 8 is optionally further processed
in a shift converter 5, to react at least a part of the CO to
produce CO.sub.2 and H.sub.2, thereby obtaining a shift converted
gas stream 80 which may be further processed or sold as such.
[0054] If desired, the synthesis gas stream 20 may be processed
before entering the shift converter 5, e.g. in a dry solids removal
unit (not shown) to at least partially remove dry ash in the raw
synthesis gas 20. Also, the synthesis gas 20 may be fed to a wet
gas scrubber (not shown).
[0055] If the coal gasification reactor 2 needs to be periodically
checked, the gas gasification reactor 3 is started up (or is
already on hot standby). The coal gasification reactor 2 is then
shut down and the distributor 25 no longer feeds oxygen (via stream
60) to the coal gasification reactor 2, but connects the oxygen
source 4 to the gas gasification reactor 3 via streams 50 and 70.
The synthesis gas 40 removed from the gas gasification reactor 3 at
outlet 12, may be processed similarly as the stream 20 and is also
fed to the shift converter 5. In case a slag would be formed in the
gasification reactor 3, a slag stream is removed via line 100.
[0056] According to an advantageous embodiment of the invention,
the synthesis gas 40 is fed to the same shift converter 5 as stream
20 originating from the coal gasification reactor 2. Before stream
40 is fed to the same shift converter it is preferred to remove any
solids from synthesis gas 20 in for example a separate dry solids
removal step. Before stream 40 is fed to the same shift converter
it is preferred to subject the synthesis gas to a separate wet gas
scrubber. With "separate" is here meant, that when the spare second
gasification reactor 3 is used the synthesis gas 40 does not pass
the dry solids removal step and/or the wet gas scrubber used for
stream 20.
[0057] As soon as the coal gasification reactor 2 is ready for use
again, the coal gasification reactor 2 may be restarted. Then the
distributor 25 may switch off the oxygen stream 70 to the gas
gasification reactor 3, and oxygen is fed again through line 60 to
coal gasification reactor 2. The gas gasification reactor 3 may
then be shut down or for instance put on hot standby until later
use. Thus, in the embodiment of FIG. 1 the reactors 2 and 3 are
used alternately.
[0058] The person skilled in the art will readily understand that,
if desired, the switching between the reactors 2 and 3 may proceed
gradually. Thus, if the reactor 2 is to be shut down, the
distributor 25 gradually decreases the oxygen stream 60 to reactor
2, at the same time increasing the oxygen stream 70 to reactor 3.
As a result, the distributor 25 feeds oxygen to both reactors 2,3
at the same time for a certain period.
[0059] In the embodiment of FIG. 1 the system 1 may comprise an
inlet for sulphur addition to sulfidise the catalyst being present
in the shift converter 5. Hereby one and the same shift converter 5
can be used for the two different carbonaceous streams 10,30 (in
this case, a "sour shift conversion" takes place in shift converter
5). Alternatively, a desulfurisation unit (not shown) may be
present (thereby resulting in a "sweet shift conversion" in shift
converter 5).
[0060] As the shift converter 5 is already known per se, it is not
further discussed here in detail.
[0061] It has been contemplated that synthesis gas can be produced
while ensuring a very high availability of the synthesis gas, even
if the gasification reactor intended for the particulate
carbonaceous stream is out of order.
[0062] Further it has been contemplated that the above may be
achieved using a very simple system.
[0063] The combination of a gasification reactor intended for a
particulate carbonaceous stream and a different type gasification
reactor is contemplated more economic than if two gasification
reactors intended for a particulate carbonaceous stream would be
used which may be an important advantage.
[0064] The first and second gasification reactors may be any
suitable reactor for partially oxidizing the respective
carbonaceous stream. If desired more than one first and second
gasification reactors may be used thereby obtaining a system
comprising more than two gasification reactors being connected to
the distributor.
[0065] The second gasification reactor may be used as a spare
reactor, which may only be used if the first gasification does not
operate, for example due to a failure to operate. In such an
embodiment it is possible to limit the capacity of the air
separation unit to a capacity, which is required to perform the
gasification in the first gasification only. In case the first
gasification fails, the second gasification can advantageously take
over the preparation of synthesis gas, thereby making use of the
oxygen manufacturing capacity, which is at that time not used by
said first gasification reactor. As a result, the availability of
synthesis gas may be ensured, even if the first gasification
reactor or one of the first gasification reactors is out of order
or on hot standby, while minimizing the required capacity of the
oxygen manufacturing unit, suitably the air separation unit.
[0066] The first, particulate carbonaceous stream may be obtained
from a high carbon containing feedstock such as naturally occurring
coal, biomass or synthetic cokes. Synthetic coke is also referred
to as petroleum coke. Petroleum coke is a by-product of a widely
applied crude oil refining process. Petroleum coke may also be
obtained as the by-product of a tar sands upgrading process as for
example described in US-A-2002/0170846. In this publication a
process is described wherein the heavy oil fraction of a bitumen or
tar sands feed is converted into a gas oil product by means of a
fluid coking process. Petroleum coke may for example be prepared by
delayed coking, which is probably the most widely used coking
process. Delayed coking uses a heavy residual oil as a feedstock.
During delayed coking, heavy residual oil is introduced into a
furnace, heated to about 480.degree. C., and pumped into coking
drums. The coking process initiates the formation of coke and
causes it to solidify on the drum wall. Thermal decomposition
drives off lower boiling products, which are removed continuously.
When this reaction is complete, the drum is opened, and coke is
removed. The first, particulate carbonaceous stream may be dry or
wet. In the latter case the first stream is in the form of a
slurry.
[0067] The first carbonaceous stream may also be a liquid stream.
Suitable liquid streams are vacuum residues as obtained from crude
mineral oils or tar sand oils or the asphalt fraction as obtained
from a de-asphalting process using the vacuum residues as obtained
from crude mineral oils or tar sand oil. Preferably the second
carbonaceous stream is a gaseous stream as will be described below
in case the first carbonaceous stream is such a liquid stream.
[0068] The second carbonaceous stream may be a substantially liquid
or gaseous stream (or a combination of one or more thereof)
suitable to be partially oxidized in the second gasification
reactor, a gaseous stream being preferred. As a liquid stream e.g.
oil, a condensate, a vacuum or atmospheric distillate or asphalt or
other residue may be used.
[0069] The use of the vacuum residue feed of the coking process may
be advantageous in situations wherein the coking operation itself
fails to prepare the petroleum coke feed for the first gasification
reactor. This will result in that the first gasification reactor
fails to operate. The feed to the coking process may then be
suitably used in the second gasification reactor.
[0070] As a gaseous stream for example natural gas, methane,
ethane, propane, refinery gases, etc. may be used. Preferably the
second carbonaceous stream is a gaseous stream, most preferably
natural gas or mixtures of natural gas and refinery gasses,
suitably refinery gasses comprising methane and ethane. A gaseous
feed is preferred because the gasification reactor and the
downstream gas processing steps may be of a more simple design.
Furthermore the hydrogen to carbon monoxide molar ratio will be
higher, resulting in less carbon dioxide by-product being made in
the water shift reaction.
[0071] The source of an oxygen containing stream may be any
suitable source. Preferably substantially pure oxygen or
(optionally oxygen enriched) air or the like is used. Further,
preferably a single source is used and is connected to both the
first and the second gasification reactor(s). Preferably, the
oxygen containing stream comprises >50 vol. % O.sub.2,
preferably >90 vol. % O.sub.2, more preferably >95 vol. %
O.sub.2, even more preferably >99 vol. % O.sub.2.
[0072] A preferred source of oxygen comprises a so-called air
separation unit, wherein an oxygen containing stream can be
prepared. Such air separation units and processes are well known
and are also referred to as cryogenic air separation. In such a
process compressed air is cooled and cleaned prior to cryogenic
heat exchange and distillation into oxygen, nitrogen, and
optionally, argon rich streams. Pressurizing these streams for
delivery is accomplished by gas compression, liquid pumping or
combinations of pumping followed by compression.
[0073] The maximum capacity of the air separation unit is
preferably less than the sum of the oxygen requirements for
gasification of the petroleum coke feed and the oxygen requirement
for gasification of the natural gas feed as described above.
[0074] The capital investment for an air separation unit is very
high. Thus processes, which require a lower oxygen capacity for the
same synthesis gas production, are desired. In a preferred
embodiment of the present invention the maximum capacity of the air
separation unit is less than 80% of the sum of the oxygen
requirements for the first and the second gasification reactor(s),
especially if two first gasification reactors and one second
gasification reactor are used. More preferably this percentage is
less than 65%, especially when one first gasification reactors and
one second gasification reactor are used. By definition the lower
boundary for this percentage is 50%.
[0075] The person skilled in the art will readily understand that
the distributor may have different embodiments as long as it is
arranged to selectively connect the source of oxygen to the first
or second gasification reactor.
[0076] With the term `raw synthesis gas` is meant that this product
stream may--and usually will--be further processed, e.g. in a dry
solid remover, wet gas scrubber, a shift converter or the like.
[0077] The person skilled in the art will readily understand that
the present invention may be modified in various ways without
departing from the scope as defined in the claims.
* * * * *