U.S. patent application number 14/358060 was filed with the patent office on 2014-10-16 for thermally integrated process and apparatus for purification and separation of components of a synthesis gas.
The applicant listed for this patent is AIR LIQUIDE GLOBAL E&C SOLUTIONS GERMANY GMBH, L'Air Liquide, Societe Anonyme Pour I'Exploitation des Procedes Georges Claude. Invention is credited to Guylaine Callens, Antoine Hernandez, Pascal Marty, Manfred Meyer, Denis Prost, Alexander Schriefl, Jean-Marc Tsevery, Marie-Pascal Victor.
Application Number | 20140305162 14/358060 |
Document ID | / |
Family ID | 47146435 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140305162 |
Kind Code |
A1 |
Callens; Guylaine ; et
al. |
October 16, 2014 |
Thermally Integrated Process and Apparatus for Purification and
Separation of Components of a Synthesis Gas
Abstract
Process for the purification and separation of a synthesis gas
stream containing hydrogen, carbon monoxide and carbon dioxide in
which synthesis gas is purified in a purification unit (W)
involving a methanol washing step to remove carbon dioxide, the
carbon dioxide depleted synthesis gas is purified by adsorption (P)
to produce a purified synthesis gas stream and the purified gas
stream is sent to a cryogenic separation unit (C) where it is
cooled and separated by cryogenic separation in a column of a
column system, at least one stream (13) enriched in carbon monoxide
is removed from a column of the column system, warmed and divided
in two, one part of the stream being removed from the cryogenic
separation unit as a first stream, the other part of the stream
forming a second stream (13B, 15B) and being sent to the
purification unit wherein it is warmed and the warmed second stream
is mixed with the first stream.
Inventors: |
Callens; Guylaine; (Fresnes,
FR) ; Hernandez; Antoine; (Le Plessis Trevise,
FR) ; Marty; Pascal; (Bry Sur Marne, FR) ;
Meyer; Manfred; (Friedrichsdorf, DE) ; Prost;
Denis; (Antony, FR) ; Schriefl; Alexander;
(New Delhi, IN) ; Tsevery; Jean-Marc; (Lieusaint,
FR) ; Victor; Marie-Pascal; (Paris, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
L'Air Liquide, Societe Anonyme Pour I'Exploitation des Procedes
Georges Claude
AIR LIQUIDE GLOBAL E&C SOLUTIONS GERMANY GMBH |
Paris
Frankfurt |
|
FR
DE |
|
|
Family ID: |
47146435 |
Appl. No.: |
14/358060 |
Filed: |
November 13, 2012 |
PCT Filed: |
November 13, 2012 |
PCT NO: |
PCT/EP2012/072522 |
371 Date: |
May 14, 2014 |
Current U.S.
Class: |
62/617 |
Current CPC
Class: |
B01D 53/1475 20130101;
F25J 2260/02 20130101; Y02P 20/152 20151101; F25J 2210/42 20130101;
Y02P 20/125 20151101; C01B 2203/042 20130101; C01B 2203/047
20130101; F25J 2205/40 20130101; Y02C 10/06 20130101; C01B 2203/046
20130101; Y02P 20/10 20151101; B01D 2252/2021 20130101; C01B
2203/0475 20130101; Y02P 20/129 20151101; Y02C 20/40 20200801; F25J
3/0271 20130101; C01B 3/52 20130101; C01B 2203/0485 20130101; F25J
3/08 20130101; F25J 2220/02 20130101; F25J 3/0276 20130101; C01B
3/506 20130101; Y02P 20/151 20151101; F25J 3/0252 20130101; F25J
2205/60 20130101; C01B 2203/0415 20130101; F25J 2205/50 20130101;
C01B 3/56 20130101; F25J 3/0261 20130101; F25J 3/0223 20130101 |
Class at
Publication: |
62/617 |
International
Class: |
F25J 3/08 20060101
F25J003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2011 |
EP |
11306476.0 |
Claims
1-15. (canceled)
16. A process for the purification and separation of a synthesis
gas stream containing hydrogen, carbon monoxide and carbon dioxide,
the method comprising the steps of: purifying the synthesis gas in
a purification unit using a methanol washing step to remove carbon
dioxide to form a carbon dioxide depleted synthesis gas; purifying
the carbon dioxide depleted synthesis gas by adsorption to produce
a purified synthesis gas stream; sending the purified synthesis gas
stream to a cryogenic unit where the purified synthesis gas stream
is cooled and separated by cryogenic separation in the cryogenic
separation unit to produce an enriched carbon monoxide stream; and
dividing the enriched carbon monoxide stream into a first part and
a second part, wherein the first part is removed from the cryogenic
separation unit to form a first stream, wherein the second part is
sent to the purification unit wherein the second part is warmed and
then mixed with the first stream.
17. A process according to claim 16, wherein the second part of the
enriched carbon monoxide stream is removed from the cryogenic
separation unit at a temperature below 20.degree. C.
18. A process according to claim 17, wherein the second part of the
enriched carbon monoxide stream is removed from the cryogenic
separation unit at a temperature above -65.degree. C.
19. A process according to claim 16, wherein the second part of the
enriched carbon monoxide stream is warmed in the purification unit
to a temperature between -40.degree. C. and 40.degree. C. and then
mixed with the first stream within the cryogenic separation
unit.
20. A process according to claim 16, wherein the second part of the
enriched carbon monoxide stream is warmed against the synthesis gas
upstream of the methanol wash column.
21. A process according to claim 16, wherein the second part of the
enriched carbon monoxide stream is warmed against an intermediate
liquid side-stream or bottom liquid stream from the methanol wash
column.
22. A process according to claim 16, wherein the second part of the
enriched carbon monoxide stream is warmed against carbon dioxide
depleted synthesis gas from the methanol wash column.
23. A process according to claim 16, wherein the second part of the
enriched carbon monoxide stream is warmed against a stream removed
from a flash column of the purification unit.
24. An apparatus for the purification and separation of a synthesis
gas stream containing hydrogen, carbon monoxide and carbon dioxide,
the apparatus comprising: a purification unit comprising a methanol
washing column and a heat exchanger, the purification unit
configured to purify the synthesis gas to remove carbon dioxide; an
adsorption unit in fluid communication with the purification unit
and configured to receive the synthesis gas from the purification
unit and provide further purification to produce a purified
synthesis gas stream; a cryogenic separation unit in fluid
communication with the adsorption unit and configured to receive
the purified synthesis gas stream from the adsorption unit and cool
and separate the purified synthesis gas stream to form an enriched
carbon monoxide stream and a hydrogen enriched stream, the
cryogenic separation unit comprising a column system and a heat
exchange line; the heat exchange line configured to warm the
enriched carbon monoxide stream and the hydrogen enriched stream;
means for dividing the enriched carbon monoxide stream into a first
stream and a second stream, wherein the heat exchanger of the
purification unit is configured to receive the second stream from
the cryogenic separation unit; and means for removing the second
stream from the heat exchanger and mixing the second stream with
the first stream.
25. The apparatus according to claim 24, wherein the apparatus is
configured such that the heat exchanger of the purification unit
receives the second stream at a temperature between -65.degree. C.
and 20.degree. C.
26. The apparatus according to claim 24, comprising a means for
sending to the heat exchanger synthesis gas upstream of the
methanol wash column of the purification unit.
27. The apparatus according to claim 24, comprising a means for
sending to the heat exchanger of the purification unit an
intermediate liquid side-stream from the methanol wash column.
28. The apparatus according to claim 24, comprising a means for
sending to the heat exchanger of the purification unit a bottom
liquid stream from the methanol wash column.
29. The apparatus according to claim 24, comprising a means for
sending to the heat exchanger of the purification unit carbon
dioxide depleted synthesis gas from the methanol wash column.
30. The apparatus according to claim 24, wherein the purification
unit includes a flash column and means for sending liquid from the
methanol wash column to the flash column and means for sending a
stream removed from the flash column to the heat exchanger of the
purification unit.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a .sctn.371 of International PCT
Application PCT/EP2012/072522, filed Nov. 13, 2012, which claims
the benefit of EP11306476.0, filed Nov. 14, 2011, both of which are
herein incorporated by reference in their entireties.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention refers to a thermally integrated
process and apparatus for the purification and separation of
components of a synthesis gas.
BACKGROUND
[0003] The term "synthesis gas" is generally applied to gaseous
mixtures which can be used to synthesize other organic compounds.
In this particular case, it refers to a mixture of carbon monoxide,
hydrogen, carbon dioxide as main components and methane, water,
nitrogen, acid gas (CO.sub.2), sulphides (H.sub.2S, COS), cyanides
(HCN), ammonia and heavy hydrocarbons as secondary components.
[0004] Coal (or petcoke or residue) gasification is often used to
produce synthesis gas, presents many advantages with regards to
operating costs and is developing more and more, especially in
countries like China.
[0005] Acid gases, such as carbon dioxide and hydrogen sulphide
contained in the synthesis gas are removed through a purification
unit via washing by a solvent. As an example, the Rectisol.RTM.
unit (RU) is a well known physical wash process to remove acid
gases and sulphides in cold methanol (-20.degree. C.; -70.degree.
C.). In this process the synthesis gas is first cooled against cold
products produced by the purification unit itself, methanol being
primarily injected into the synthesis gas to prevent the formation
of ice. The synthesis gas is then sent to the bottom of a washing
column where hydrogen sulphide and COS are removed by washing with
liquid methanol solvent rich in carbon dioxide, coming from the
upper part of the column. The carbon dioxide contained in the
synthesis gas is absorbed by washing with clean liquid methanol at
the top of the column. Purified synthesis gas, which is free from
carbon dioxide and COS and hydrogen sulphide, is withdrawn at the
top of the column (absorber). The methanol rich in carbon dioxide
and sulphur compounds is removed at the bottom of the wash column
and regenerated by a series of expansion steps down to a medium
pressure, so as to produce a flash gas. The methanol rich in carbon
dioxide from the upper section is also regenerated by expansion
down to a lower pressure to produce a second flash gas. The medium
and low pressure expansions serve to remove the acid gases from the
solvent. The solvent is then further regenerated by warm
regeneration so as to produce clean methanol.
[0006] The purified gas leaving the top of the absorber is then
further purified by adsorption and sent to a cold box where it may
be treated by washing with liquid nitrogen, liquid carbon monoxide
or liquid methane or by partial condensation.
[0007] Flash gas from the cold box may be produced from a phase
separator of a partial condensation step or from an intermediate
distillation column.
[0008] "Low Temperature Technology in Coal Refining" by W. H.
Scholz, Chemical Economy and Engineering Review, Vol 14, January
1982 suggests that an ammonia synthesis gas could be warmed in a
Rectisol.RTM. plant.
SUMMARY OF THE INVENTION
[0009] One aim of the present invention is to optimize the heat
balance (integration of cold) between the purification unit and the
cold box.
[0010] According on an object of the invention, there is provided a
process for the purification and separation of a synthesis gas
stream containing hydrogen, carbon monoxide and carbon dioxide in
which synthesis gas is purified in a purification unit involving a
methanol washing step to remove at least carbon dioxide, the carbon
dioxide depleted synthesis gas is purified by adsorption to produce
a purified synthesis gas stream and the purified gas stream is sent
to a cryogenic unit where it is cooled and separated by cryogenic
separation in a column system to produce at least one stream
enriched in carbon monoxide, at least one said stream enriched in
carbon monoxide is divided in two, one part of the stream being
removed from a column of the cryogenic separation unit as a first
stream, the other part of the stream forming a second stream and
being sent to the purification unit wherein it is warmed and the
warmed second stream is mixed with the first stream.
[0011] Optionally: [0012] the second stream is removed from the
cryogenic separation unit at a temperature below 20.degree. C.
[0013] the second stream is removed from the cryogenic separation
unit at a temperature above -65.degree. C. [0014] the second stream
is warmed in the purification unit to a temperature between
-40.degree. C. and 40.degree. C. and then mixed with the first
stream within the cryogenic separation unit. [0015] the second
stream is warmed against the synthesis gas upstream of the methanol
wash column scrubber and/or against an intermediate liquid
side-stream or bottom liquid stream from the methanol wash column
and/or against carbon dioxide depleted synthesis gas from the
methanol wash column and/or against a stream removed from a flash
column of the purification unit.
[0016] According to a further object of the invention, there is
provided an apparatus for the purification and separation of a
synthesis gas stream containing hydrogen, carbon monoxide and
carbon dioxide including a purification unit comprising a methanol
washing column and at least one heat exchanger, wherein synthesis
gas is purified to remove carbon dioxide, an adsorption unit
wherein the carbon dioxide depleted synthesis gas from the
purification unit is further purified by adsorption to produce a
purified synthesis gas stream, a cryogenic separation unit wherein
the purified synthesis gas stream from the adsorption unit is
cooled and separated by cryogenic separation in a column of a
column system to produce at least one stream enriched in carbon
monoxide, means for removing said at least one stream enriched in
carbon monoxide from a column of the column system, a heat exchange
line for warming the stream, means for dividing the stream into a
first stream and a second stream, means for removing the first
stream from the cryogenic separation unit, means for removing the
second stream from the cryogenic separation unit, means for sending
the second stream to the heat exchanger of the purification unit
and means for removing the warmed second stream from the heat
exchanger and mixing it with the first stream.
[0017] Optionally: [0018] the means for removing the second stream
from the cryogenic separation unit are connected to the cryogenic
separation unit in such a way that the second stream is sent to the
heat exchanger of the purification unit at a temperature between
-65.degree. C. and 20.degree. C. [0019] the apparatus comprises
means for sending to the heat exchanger synthesis gas upstream of
the methanol wash column of the purification unit and/or an
intermediate liquid side-stream and/or the bottom liquid stream
from the methanol wash column and/or carbon dioxide depleted
synthesis gas from the methanol wash column. [0020] the
purification unit includes a flash column and means for sending
liquid from the methanol wash column to the flash column and means
for sending a stream removed from the flash column to the heat
exchanger of the purification unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, claims, and accompanying drawings. It is to
be noted, however, that the drawings illustrate only several
embodiments of the invention and are therefore not to be considered
limiting of the invention's scope as it can admit to other equally
effective embodiments.
[0022] FIG. 1 shows an embodiment of the invention.
[0023] FIG. 2 shows an embodiment of the invention.
DETAILED DESCRIPTION
[0024] The invention will be described in greater detail with
reference to the attached figures. FIG. 1 shows the process
according to an embodiment of the invention and FIG. 2 shows the
detail of a Rectisol.RTM. type purification unit to be used in the
process according to the invention.
[0025] In FIG. 1, one or several products from the cold box (CO,
H.sub.2, H.sub.2+CO mixture, flash gas and/or cold box purges) are
heated up to ambient temperature in an exchanger of the
purification unit. The heated stream or streams is/are mixed with a
corresponding stream or streams (having the same composition) at
the cold box outlet or in cold box warm exchanger depending on the
return temperature.
[0026] Synthesis gas 1 from a synthesis gas generation unit (not
shown--gasifier as an example) is cooled in a heat exchanger 3 and
sent to a purification unit W which uses a solvent washing step
(methanol as an example). The synthesis gas is treated in unit W to
remove acid gases, such as carbon dioxide and hydrogen sulphide.
The purified synthesis gas 7 at -65.degree. C. to -35.degree. C. is
sent to an adsorption unit P, to remove solvent and carbon dioxide
traces, forming gas 11. Gas 11 at between -35.degree. C. and
-65.degree. C. is divided into two parts. One part 11 is used to
cool the synthesis gas in exchanger 3. The synthesis gas 11 is
thereby warmed to a temperature around ambient, i.e. between
0.degree. C. and 45.degree. C. and is then sent to the cryogenic
distillation unit C where it is cooled down from the ambient
temperature in warm heat exchanger HX and cold heat exchanger CX
before being separated by cryogenic distillation in a column system
to form a product gas 13, such as carbon monoxide and a further gas
15 which is a flash gas or a purge gas, each gas being removed from
a column of the column system.
[0027] The rest of gas 11 from adsorption unit P forms parts 11A
which is warmed up in the purification unit W to form warmed gas
11A which is mixed with warmed gas 11 from exchanger 3 and is sent
at ambient temperature to the cryogenic distillation. Gas 13A is
formed by a portion of the product gas 13 of the cryogenic
distillation unit but removed from the warm heat exchanger HX at
between -65.degree. C. to 20.degree. C. Gas 13A is warmed in heat
exchanger 3 against the feed synthesis 1 Gas 13B is a portion of
gas 13B, warmed in the purification unit and mixed with Gas 13A;
The mixture is sent to the warm heat exchanger HX or downstream of
the heat exchanger HX outside the cryogenic unit C.
[0028] Similarly a portion 15A of gas 15 is removed from the warm
heat exchanger HX and/or the cold heat exchanger CX at between
-65.degree. C. to 20.degree. C. and divided in two, part 15B being
warmed in the purification unit W and part 15A being warmed in
exchanger 3. The rest of stream 15 is warmed in heat exchanger HX
to form a purge gas. The two warmed streams are mixed to form
stream 15A and sent back to stream 15. The mixing point is either
within the warm heat exchanger HX via stream 15C or downstream of
the heat exchanger HX outside the cryogenic unit C.
[0029] FIG. 2 illustrates a Rectisol.RTM. process for acid gas
removal with indication of locations for warming cold gases 11,
11A, 13A, 13B, 15A and 15B (mentioned as gas A in FIG. 3). The
process removes carbon dioxide and hydrogen sulphide, in
particular. The solvent used is chilled methanol with the
advantages of ready availability, high stability and high
solubility characteristics for CO.sub.2, H.sub.25 and COS meaning
that the solvent circulation rate is relatively small compared to
other wash systems. This results in low utility consumption figures
(steam, cooling water, electricity . . . ). The Rectisol.RTM.
process is especially suitable for high sour gas concentrations and
high pressures. The apparatus includes a methanol absorption column
K01 for removing CO.sub.2 and/or H.sub.2S, a regeneration column
K02 also called MP flash column, a low-pressure flash regeneration
column K03 and a hot regenerator column K04.
[0030] The raw synthesis gas 101 is cooled in a series of heat
exchangers 103, 105, 113. In the first heat exchanger 103, the raw
feed gas is cooled against cold synthesis gas A coming from the
cryogenic unit C, for example a liquid nitrogen wash unit, and
against the purified gas 112 exiting the H.sub.2S/CO.sub.2
absorption column K01. In the second heat exchanger 105, the raw
feed gas is cooled against colder fluid A from the cryogenic unit.
The condensed water and BTX/naphtha are then separated in a gas
separator 107 and sent to battery limits. Water is removed from the
feed gas in order to avoid water build-up in the methanol loop: if
the water content is too high, solubility of methanol drops. A
water wash column 109 is included to remove NH3. The gas 111 is
sent to a third cooling step in exchanger 113. In the exchanger
113, the gas 111 is then further cooled against gas A from the
cryogenic unit C, against the purified gas 112 exiting the
H.sub.2S/CO.sub.2 absorption column K01 and against CO.sub.2
product 141 coming from the re-absorber CO.sub.2 product column
K03. Additionally the gas may be cooled against recycle top gas 127
coming from the MP flash column K02. The cooled gas 111 is then
sent to the H.sub.2S/CO.sub.2 absorption column K01.
[0031] The gas is sent to the bottom pre-wash section of the
absorption column K01 where trace components like NH.sub.3, and HCN
and BTX are absorbed with a small stream of
CO.sub.2-sub-cooled-laden methanol. The pre-wash methanol 115
leaves the bottom of the absorption column K01 and is sent to the
hot regenerator column K04.
[0032] The synthesis gas is then routed up via a chimney tray into
the H.sub.2S-absorption section of the absorption column K01
(bottom section) where H.sub.2S and COS are removed by dissolution
in CO.sub.2-saturated methanol coming from the CO.sub.2-absorbtion
section (top section). The methanol solvent is fed to the top of
the Absorption section on flow control proportional to the inlet
gas flow. The CO.sub.2+H.sub.2S-laden methanol 116 leaves the main
sump of the absorber column K01 and is routed to the MP-Flash
Column K02 for regeneration. The de-sulfurised gas then enters the
lower washing part of the CO.sub.2-absorption section via another
chimney tray. An additional sulphur-free feed gas stream may also
be fed to the column at this point.
[0033] In the CO.sub.2-absorption section, the gas is washed with
cold, flash regenerated methanol used as main wash methanol and
with cold, hot regenerated methanol used as fine wash methanol. Due
to the heat of absorption of the CO.sub.2, the methanol 117, 123 is
heated up considerably and needs to be cooled on its way down the
column. Therefore, in the lower part of the CO.sub.2-absorbtion
section, the gas is scrubbed with CO.sub.2-laden methanol which is
cooled against gas A from the cryogenic unit C in exchangers 119,
121. The cold purified gas 112 exiting the absorber K01 is then
routed to the adsorption unit P of FIGS. 1 and 2.
[0034] The bottom liquid 135 from flash column K02 is sent to the
top of column K03 following cooling in exchanger 136 against stream
A.
[0035] The LP flash column K03 receives the bottom liquid 135 and
137 from column K02 and produces a CO.sub.2 rich stream 141 and an
off-gas stream, which is sent to the atmosphere. In hot regenerator
K04 the methanol is finally regenerated by stripping with methanol
vapours. The overheads being an acid gas with sulphur content
suitable to be processed in a Claus sulphur recovery unit. The
bottoms product, stream 125, is the finewash methanol fed on top of
absorber K01.
[0036] The stream A is thus used to cool at least one of the
following fluids: methanol removed at an intermediate point of the
absorption column K01, synthesis gas which is to be treated in
absorption column K01, bottom liquid from the MP flash column K02,
which then feeds the LP flash column K03.
[0037] Among the advantages of the invention are: [0038] reduction
of the adsorbent volume, of the drying bottle size, of the bed
regeneration flowrate and of the regeneration heater steam
consumption, as impurity adsorption is improved at low temperature;
[0039] reduction of the cold box warm exchanger size; [0040]
optimization of the purification unit heat balance, the unit
operating at a lower temperature, thanks to the additional
refrigeration available at the cold box outlet; and [0041]
optimization of the overall purification unit efficiency and cold
box energy consumption (power consumption of frigorific cycle
compressor).
[0042] While the invention has been described in conjunction with
specific embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description. Accordingly, it is
intended to embrace all such alternatives, modifications, and
variations as fall within the spirit and broad scope of the
appended claims. The present invention may suitably comprise,
consist or consist essentially of the elements disclosed and may be
practiced in the absence of an element not disclosed. Furthermore,
if there is language referring to order, such as first and second,
it should be understood in an exemplary sense and not in a limiting
sense. For example, it can be recognized by those skilled in the
art that certain steps can be combined into a single step.
[0043] The singular forms "a", "an" and "the" include plural
referents, unless the context clearly dictates otherwise.
[0044] "Comprising" in a claim is an open transitional term which
means the subsequently identified claim elements are a nonexclusive
listing (i.e., anything else may be additionally included and
remain within the scope of "comprising"). "Comprising" as used
herein may be replaced by the more limited transitional terms
"consisting essentially of" and "consisting of" unless otherwise
indicated herein.
[0045] "Providing" in a claim is defined to mean furnishing,
supplying, making available, or preparing something. The step may
be performed by any actor in the absence of express language in the
claim to the contrary a range is expressed, it is to be understood
that another embodiment is from the one.
[0046] Optional or optionally means that the subsequently described
event or circumstances may or may not occur. The description
includes instances where the event or circumstance occurs and
instances where it does not occur.
[0047] Ranges may be expressed herein as from about one particular
value, and/or to about another particular value. When such
particular value and/or to the other particular value, along with
all combinations within said range.
[0048] All references identified herein are each hereby
incorporated by reference into this application in their
entireties, as well as for the specific information for which each
is cited.
* * * * *