GB2030973A - Creación de Inventos y Patentes con Inteligencia Artificial

GB2030973A – Treatment of ammonia synthesis purge gas
– Google Patents

GB2030973A – Treatment of ammonia synthesis purge gas
– Google Patents
Treatment of ammonia synthesis purge gas

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Publication number
GB2030973A

GB2030973A
GB7839880A
GB7839880A
GB2030973A
GB 2030973 A
GB2030973 A
GB 2030973A
GB 7839880 A
GB7839880 A
GB 7839880A
GB 7839880 A
GB7839880 A
GB 7839880A
GB 2030973 A
GB2030973 A
GB 2030973A
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GB
United Kingdom
Prior art keywords
purge gas
liquid
pressure
hydrogen
expanded
Prior art date
1978-10-10
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Granted

Application number
GB7839880A
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GB2030973B
(en

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Petrocarbon Developments Ltd

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Petrocarbon Developments Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1978-10-10
Filing date
1978-10-10
Publication date
1980-04-16

1978-10-10
Application filed by Petrocarbon Developments Ltd
filed
Critical
Petrocarbon Developments Ltd

1978-10-10
Priority to GB7839880A
priority
Critical
patent/GB2030973B/en

1979-10-10
Priority to US06/083,952
priority
patent/US4255406A/en

1979-10-10
Priority to IT26382/79A
priority
patent/IT1125479B/en

1979-10-10
Priority to IN1051/CAL/79A
priority
patent/IN152360B/en

1980-04-16
Publication of GB2030973A
publication
Critical
patent/GB2030973A/en

1982-10-27
Application granted
granted
Critical

1982-10-27
Publication of GB2030973B
publication
Critical
patent/GB2030973B/en

Status
Expired
legal-status
Critical
Current

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Classifications

C—CHEMISTRY; METALLURGY

C01—INORGANIC CHEMISTRY

C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF

C01C1/00—Ammonia; Compounds thereof

C01C1/02—Preparation, purification or separation of ammonia

C01C1/04—Preparation of ammonia by synthesis in the gas phase

C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst

C01C1/0476—Purge gas treatment, e.g. for removal of inert gases or recovery of H2

C—CHEMISTRY; METALLURGY

C01—INORGANIC CHEMISTRY

C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C

C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen

C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification

C01B3/506—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification at low temperatures

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES

F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE

F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification

F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation

F25J3/0605—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the feed stream

F25J3/062—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES

F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE

F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification

F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation

F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream

F25J3/068—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of H2/N2 mixtures, i.e. of ammonia synthesis gas

C—CHEMISTRY; METALLURGY

C01—INORGANIC CHEMISTRY

C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C

C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas

C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas

C01B2203/0465—Composition of the impurity

C—CHEMISTRY; METALLURGY

C01—INORGANIC CHEMISTRY

C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C

C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas

C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas

C01B2203/0465—Composition of the impurity

C01B2203/048—Composition of the impurity the impurity being an organic compound

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES

F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE

F25J2210/00—Processes characterised by the type or other details of the feed stream

F25J2210/20—H2/N2 mixture, i.e. synthesis gas for or purge gas from ammonia synthesis

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES

F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE

F25J2245/00—Processes or apparatus involving steps for recycling of process streams

F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES

F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE

F25J2270/00—Refrigeration techniques used

F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES

F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE

F25J2280/00—Control of the process or apparatus

F25J2280/02—Control in general, load changes, different modes («runs»), measurements

Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE

Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

Y02P20/00—Technologies relating to chemical industry

Y02P20/50—Improvements relating to the production of bulk chemicals

Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Description

1
GB 2 030 973 A 1
SPECIFICATION
Treatment of ammonia synthesis purge gas
This invention relates to an improvement in the treatment of ammonia synthesis purge gas.
5 In a widely practised process, ammonia is synthesised at superatmospheric pressure from a synthesis gas comprising hydrogen and nitrogen ideally in a ratio of 3 parts hydrogen to 1 part nitrogen by volume. However, in commercial 10 processes, the ammonia synthesis gas also generally contains methane (about 1 mole %) introduced with the hydrogen, and argon (about 0.3 mole%) introduced with the nitrogen.
The methane and argon take no part in the 15 ammonia synthesis and are therefore removed along with the unreacted hydrogen and nitrogen from the ammonia product which condenses out. To improve the efficiency of the process, the gas stream containing the unreacted nitrogen and 20 hydrogen, and also containing the methane and argon impurities, is recycled to the ammonia synthesis reaction zone where it mixes with fresh nitrogen and hydrogen containing fresh amounts of these impurities, and thus these impurities tend 25 to accumulate in the reaction zone as time proceeds, thereby lowering the partial pressure of the reacting mixture and hence reducing ammonia yield. Action therefore has to be taken to prevent the concentration of these impurities in the reactor 30 exceeding an acceptable level.
To this end, it is general practice to withdraw continuously from the recycling gas stream a purge gas stream which is at superatmospheric pressure and which generally will have a 35 combined content of 10 to 11% of argon and methane. The major components of this purge gas stream, which will have the same constitution as the recycling gas stream, are’of course hydrogen and nitrogen of which the hydrogen is the more 40 valuable. It is therefore desirable to recover as much as possible of this hydrogen for return to the ammonia synthesis reaction zone.
In practice, this is achieved in a hydrogen recovery plant wherein the purge gas stream is 45 subjected to partial condensation at sub-ambient temperatures to separate a hydrogen-enriched gaseous stream, which will also contain some nitrogen, from a condensed material which will comprise most of the argon and methane and the 50 remainder of the nitrogen and hydrogen. The gaseous hydrogen-rich stream may then be recycled to the ammonia synthesis reaction zone or otherwide used and it will be understood that since it is generally not economic to operate the 55 process in such manner that ail the argon and methane is separated out, the rate at which the purge gas stream is withdrawn from the recycling gas stream will depend inter alia on the efficiency of the separation in the hydrogen recovery plant. 60 Thus in current practice it is found advantageous to recover a product consisting of approximately 90% hydrogen, 9% nitrogen and about 1 % of a mixture of methane and argon.
The purge gas, which is available from the synthesis plant at a high pressure, which may be 150—300 bar, is generally treated in the low temperature separation unit at pressures varying from 40 to 70 bar and the hydrogen-nitrogen product is returned at close to this pressure to an intermediate stage of the synthesis gas compressor. The actual recovery pressure may be varied according to the design of this compressor in line with the interstage pressures of the multistage machine.
At least a part of the refrigeration required in the separation unit is supplied by expanding the condensate to a low pressure, which may be 2 to 4 bar, and evaporating it in thermal contact with the high pressure purge gas. However, in current practice this refrigeration is generally inadequate and has to be supplemented by the production of some additional cold supplied by an external refrigeration cycle.
The amount of additional refrigeration required is reduced and the temperature of its supply raised by increasing the pressure at which the purge gas is admitted to the hydrogen recovery unit. Thus with an operating pressure around 50 bar it is necessary to use an external nitrogen cycle with work-expansion of the nitrogen in a turbine in a temperature range around —70°C. However if the operating pressure is raised to 70 bar, it is sufficient to install an ammonia refrigeration unit with a lower capacity and an evaporating temperature around —30°C.
On the other hand, operation of the recovery unit at the higher pressure of 70 bar, while advantageous for cold production, does not in every case enable the methane and argon to be removed from the purge gas to a sufficiently low level to satisfy the requirement of the synthesis plant. Thus, in present design practice, operation at 50 bar can reduce the residual argon and methane content to 1 % or even slightly less, whereas operation at 70 bar will, according to current practice, leave around 1.5% of these so-called «inserts» in the hydrogen-nitrogen product.
We have now developed a process whereby the amount of refrigeration which needs to be applied in the hydrogen recovery unit of an ammonia synthesis purge gas treatment plant may be reduced and which can enable external refrigeration to be eliminated entirely.
Alternatively or additionally, the temperature at which refrigeration is applied may be raised while still maintaining a satisfactorily low content of inerts in the hydrogen-nitrogen product.
According to the present invention there is provided a process for the recovery of hydrogen from purge gas from an ammonia synthesis plant which comprises:
(a) cooling a high pressure stream of said purge gas to a sub-ambient temperature at which substantially all of the methane and argon contained in said purge gas stream and a portion of the nitrogen condense,
(b) expanding liquid and vapour components of the cooled high pressure stream to an intermediate pressure.
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GB 2 030 973 A 2
(c) phase separating liquid and vapour components of the cooled and expanded purge gas stream,
(d) expanding separated liquid component 5 from step (c), and
(e) heating expanded separated liquid component from step (d) and separated vapour component from step (c) in heat exchange with said high pressure stream of
10 purge gas to cool the latter.
The invention further provides a method of synthesing ammonia by reacting a synthesis gas comprising nitrogen and hydrogen at superatmospheric pressure in a reaction zone with 15 recycling of unreacted gas to the reaction zone and wherein a purge gas stream is withdrawn at superatmospheric pressure from the gas being recycled, is subjected to a recovery process comprising steps (a) to (e) above and at least a 20 portion of said separated vapour component is recycled to the reaction zone.
Preferably the high pressure stream of purge gas is at a pressure of at least 70 bar.
The expansion of the liquid and vapour 25 components may be carried out directly on the liquid-vapour mixture formed in step (a), for example in a single valve, or alternatively the liquid vapour mixture may be fed to a preliminary separator from which the liquid and vapour are 30 withdrawn and expanded separately, for example through separate valves before being subjected to phase separation step (c).
In the latter case, the separately expanded streams are preferably recorhbiried in of prior to 35 the separator in which phase separation step (c) is carried to enable a degree of equilibration of the separated phases to occur. To promote such equilibration, the separately expanded gaseous stream is preferably admitted to the separator in 40 which phase separation step (c) is carried out below the level of liquid therein. Similarly the separately expanded liquid stream is preferably admitted above said level.
Preferably in carrying out the process of the 45 invention, ammonia purge gas at a pressure equal to or greater than 70 bar is fed to a hydrogen recovery unit and is cooled by counter-current heat exchange with hydrogen-nitrogen product and with evaporating condensate to a temperature at 50 which almost all of the methane and argon and a part of the nitrogen condense; the resulting liquid-vapour mixture is expanded to an intermediate pressure which is preferably 20 to 40 bar lower than the feed pressure; the expanded mixture is 55 fed to a separator at said intermediate pressure; a gaseous hydrogen-nitrogen mixture, preferably containing about 1 % or less of methane and argon, and condensate mixture comprising methane, argon and some nitrogen are recovered; 60 the hydrogen-nitrogen mixture is returned in heat-exchange with the high pressure purge gas; the condensate is expanded to a low pressure, preferably 2 to 4 bar; and the expanded condensate is evaporated and warmed in heat 65, exchange with the high pressure purge gas.
The invention will now be described in more detail by way of example with particular reference to the accompanying drawings of which Figure 1 is a simplified flow diagram of a conventional ammonia synthesis purge gas separation plant and Figures 2 to 4 illustrate modes of operation according to the invention.
Referring to Figure 1 which illustrates a conventional process, numerals 1,2 and 3 denote heat exchangers, 4 is a liquid-vapour separator and 5, 6 and 10 are expansion valves. Purge gas at 150 bar enters the hydrogen recovery unit through line 11, is expanded to 50 bar in expansion valve 5 controlled by pressure controller P5, is cooled in heat exchanger 1 with returning hydrogen-nitrogen product and evaporating condensate, further cooled to —70°C in exchanger 2 with a nitrogen cycle (not shown), and finally cooled to —180°C in exchanger 3 with hydrogen-nitrogen product and evaporating condensate. The resulting liquid-vapour mixture leaves exchanger 3 through line 12 and passes to separator 4. A gas consisting of hydrogen and nitrogen and containing 1% of a mixture of methane and argon leaves the separator through line 13, is warmed in exchangers 3 and 1 and leaves as product through line 14. Condensate, consisting of methane, argon, nitrogen and a small amount of dissolved hydrogen, leaves the separator 4 through line 15, is expanded to 3 bar in the expansion valve 6, controlled by pressure controller P6, then is evaporated in exchanger 3 and warmed in exchanger 1, finally leaving through line 16.
In order to lowerthe temperature range in which the condensate evaporates, a small stream of hydrogen is expanded through valve 10 and injected into the condensate.
Referring now to Figure 2, in which like .
numerals are used where appropriate, the purge gas at 150 bar enters through line 11 and is expanded to 70 bar in valve 5. It is cooled in exchanger 1 with returning product and evaporated condensate and further cooled in exchanger 2 to 33°C with evaporating liquid ammonia. It is then cooled to —180°C in exchanger 3, and expanded to an intermediate pressure of 48 bar in expansion valve 7, controlled by pressure controller P7. At this pressure it enters separator 4, where it is separated into a vapour containing 1 % of a mixture of methane and argon, which is warmed in exchangers 3 and 1, leaving through line 14,
and a condensate, which is withdrawn through line 1 5, expanded to 2 bar in valve 6, warmed and ? evaporated in exchangers 3 and 1 and withdrawn through line 16. To ensure equilibrium downstream of valve 7, a suitable mixing device may be inserted in the pipeline.
In Figure 3 the purge gas, which again enters at 150 bar, is expanded in valve 5 to 90 bar. It is then cooled in a single heat exchanger to about —180 °C and further expanded to an intermediate pressure of 50 bar in valve 7, controlled by pressure controller P7. At this pressure it enters separator 4, where it is separated into a vapour
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GB 2 030 973 A 3,
containing 1 % of methane and argon and a condensate. The vapour is removed through line 13 and warmed in exchanger 1, and the condensate is withdrawn through line 15, expanded to 2 bar in 5 valve 6 and warmed in exchanger 1, leaving through line 16. No additional refrigeration, whether by way of a nitrogen cycle or with evaporating liquid ammonia, is necessary for efficient operation of the plant.
10 In the process illustrated in Figure 4 (which otherwise operates in a similar manner to that illustrated in Figure 3) the high pressure stream, after cooling in heat exchanger 1, but still at a pressure of about 90 bar is subjected to a 15 preliminary phase separation in separator 9. The separated liquid and vapour components are then expanded separately through valves 7 and 8 to the same intermediate pressure and fed to a further phase separator 4. A particular advantage of 20 passing liquid and vapourthrough the separate . valves 7 and 8 is that two-phase flow in a single valve is avoided, thus reducing the likelihood of instability and control difficulties. The liquid and vapour components are then introduced into 25 phase separator 4 respectively above and below the level of liquid therein thus ensuring that the separated liquid and vapour are at least partially equilibrated at the intermediate pressure. Thereafter operation is as in Figure 3. 30 The introduction of the intermediateexpansion valve(s), permitting the purge gas to be cooled at one pressure and separation to take place at another lower pressure, results in an increased flexibility of the process, e.g. allowing the external 35 refrigeration to be reduced or eliminated, its temperature to be raised where it is still required, with a corresponding reduction in power consumption, and/or the inerts content of the hydrogen-nitrogen product to be adjusted to 40 satisfy the requirements of the ammonia synthesis plant.
This flexibility is demonstrated in the following Table, in whichj^l denotes the pressure at which the purge gas is cooled, P2 the pressure in the final 45 separator,xtheinertscontentofthe hydrogen-•nitrogen product,T the temperature at which, if at all, refrigeration is required, and Q the amount of refrigeration needed by a hydrogen recovery unit associated with a 1000 ton/day ammonia 50 synthesis plant. In every case the tail gas
(evaporated condensate) is asumed to leave the hydrogen recovery unit at 3 bar abs.
Table
Example
P1 bar
P2 bar
X
M%
T
°C
Q
Kcal/hr.
A
50
50
1.0
-70
10,000
B
70
70
1.4
-30
4,000
C
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50
1.0
-33
5,000
D
90
50
1.0
0
It will be seen that, in comparison with Example A, the procedure of Example B, which dpes not utilise the present invention, while reducing the amount of refrigeration needed and raising the temperature at which it is required, delivers a product of lower purity. But the procedure of Example C, while still halving the refrigeration needed in Example A and raising the refrigeration supply temperature from —70 to —33°C,
maintains the inerts content of the product at 1 %. In’Example D, which also makes use of the invention, raising the entry pressure P1 to 90 bar enables external refrigeration to be eliminated entirely, while still maintaining the desired product purity.

Claims (13)

1. A process for the recovery of hydrogen from purge gas from an ammonia synthesis plant which comprises:
(a) cooling a high pressure stream of said purge gas to a sub-ambient temperature at which substantially all of the methane and argon contained in said purge gas stream and a portion of the nitrogen condense,
(b) expanding liquid and vapour components of the cooled high pressure stream to an intermediate pressure,
(c) phase separating liquid and vapour components of the cooled and expanded purge gas stream,
(d) expanding separated liquid component from step (c), and
(e) heating expanded separated liquid component from step (d) and separated vapour component from step (c) in heat exchange with said.high pressure stream of purge gas to cool the latter.

2. A process according to Claim 1 wherein the high pressure stream of purge gas it at a pressure of at least 70 bar.

3. A process according to Claim 1 or Claim 2 wherein the expansion of the liquid and vapour components is carried out directly on the liquid-vapour mixture formed in step (a).

4. A process*according to Claim 1 or Claim 2 wherein prior to the expansion of the liquid and vapour components, liquid/vapour mixture formed in step (a) is fed to a preliminary separator from which liquid and vapour are withdrawn and expanded separately to said intermediate pressure before being subjected to phase separation step (c).

5. A process according to Claim 4 wherein the separately expanded streams are recombined in or prior to the separator in which phase separation step (c) is carried out to enable a degree of equilibration of the separated phases to occur.

6. A process according to Claim 5 wherein the separately expanded gaseous stream is admitted to the separator in which phase separation step (c) is carried out below the level of liquid therein.

7. A process according to Claim 6 wherein the separately expanded liquid stream is admitted above said level.
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GB 2 030 973 A 4

8. A process according to Claim 1 and comprising the steps of (1) feeding ammonia purge gas at a pressure equal to or greater than 70 bar to a hydrogen recovery unit where it is
5 cooled by counter-current heat exchange with hydrogen-nitrogen product and with evaporating condensate to a temperature at which almost all of the methane and argon and a part of the nitrogen condenses; (2) expanding the resulting 10 liquid-vapour mixture to an intermediate pressure; (3) feeding the expanded mixture from step (2) to a separator at said intermediate pressure; (4) recovering a gaseous hydrogen-nitrogen mixture and a condensate mixture comprising methane, 1 5 argon and some nitrogen; (5) returning the hydrogen-nitrogen mixture in heat-exchange with the high pressure purge gas; (6) expanding the condensate to a low pressure; and (7) evaporating and warming the expanded condensate in heat 20 exchange with the high pressure purge gas.

9. A process according to Claim 8 wherein the hydrogen-nitrogen mixture recovered in step (4) contains about 1% or less of methane and argon.

10. A process according to Claim 8 or Claim 9
25 wherein in step (6) the condensate is expanded to a pressure of from 2 to 4 bars.

11. A process according to any preceding claim in which the liquid and vapour components of the cooled high pressure stream are expanded to an
30 intermediate pressure which is from 20 to 40 bar lower than the pressure of the high pressure stream.

12. A process for the recovery of hydrogen from purge gas from an ammonia synthesis plant
35 according to claim 1 and substantially as hereinbefore described with particular reference to any of Figs. 2,3 and 4 of the accompanying drawings.

13. A method of synthesising ammonia, by 40 reacting a synthesis gas comprising nitrogen and hydrogen at superatmospheric pressure in a reaction zone with recycling of reacting gas to the reaction zone and wherein a purge gas stream is withdrawn at superatmospheric pressure from the 45 gas being recycled. Is subjected to a recovery process as claimed in any preceding claim and at least a portion of the separated vapour component is recycled to the reaction zone.
Printed for Her Majesty’s Stationery Office by the Courier Press, Leamington Spa, 1980, Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.

GB7839880A
1978-10-10
1978-10-10
Treatment of ammonia synthesis purge gas

Expired

GB2030973B
(en)

Priority Applications (4)

Application Number
Priority Date
Filing Date
Title

GB7839880A

GB2030973B
(en)

1978-10-10
1978-10-10
Treatment of ammonia synthesis purge gas

US06/083,952

US4255406A
(en)

1978-10-10
1979-10-10
Treatment of ammonia synthesis purge gas

IT26382/79A

IT1125479B
(en)

1978-10-10
1979-10-10

BLEEDING GAS TREATMENT IN THE SUMMARY OF AMMONIA

IN1051/CAL/79A

IN152360B
(en)

1978-10-10
1979-10-10

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

GB7839880A

GB2030973B
(en)

1978-10-10
1978-10-10
Treatment of ammonia synthesis purge gas

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Publication Date

GB2030973A
true

GB2030973A
(en)

1980-04-16

GB2030973B

GB2030973B
(en)

1982-10-27

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Priority Date
Filing Date

GB7839880A
Expired

GB2030973B
(en)

1978-10-10
1978-10-10
Treatment of ammonia synthesis purge gas

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US
(1)

US4255406A
(en)

GB
(1)

GB2030973B
(en)

IN
(1)

IN152360B
(en)

IT
(1)

IT1125479B
(en)

Cited By (5)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

EP0119001A2
(en)

1983-02-14
1984-09-19
Exxon Research And Engineering Company
Improved cryogenic production of ammonia synthesis gas

EP0160412A2
(en)

1984-04-25
1985-11-06
Imperial Chemical Industries Plc
Ammonia synthesis

US4592903A
(en)

1983-11-10
1986-06-03
Exxon Research & Engineering Co.
Low severity hydrocarbon steam reforming process

EP0247220A1
(en)

1986-05-27
1987-12-02
Roger Warren Parrish
Process for manufacture of ammonia

EP0282165A1
(en)

1987-03-02
1988-09-14
Air Products And Chemicals, Inc.
Method and plant for recovering hydrogen and argon from ammonia synthesis purge gas

Families Citing this family (8)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

US4594233A
(en)

1985-01-04
1986-06-10
Parrish Roger W
Process for manufacture of ammonia

US4793832A
(en)

1986-04-14
1988-12-27
Fmc Corporation
Air purification and temperature controlling system and method

US5100635A
(en)

1990-07-31
1992-03-31
The Boc Group, Inc.
Carbon dioxide production from combustion exhaust gases with nitrogen and argon by-product recovery

GB2265320A
(en)

1992-03-17
1993-09-29
Process Scient Innovations
Removing liquids from compressed gas

US5458663A
(en)

1993-11-29
1995-10-17
Basf Corporation
Apparatus for removing emissions by condensation and precipitation

US5433761A
(en)

1993-11-29
1995-07-18
Basf Corporation
Energy efficient apparatus for removing emissions

US5433769A
(en)

1993-11-29
1995-07-18
Basf Corporation
Energy efficient process for removing emissions

US5431715A
(en)

1993-11-29
1995-07-11
Basf Corporation
Process for removing emissions by condensation and precipitation

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Assignee
Title

DE1230407B
(en)

1964-08-22
1966-12-15
Basf Ag

Process for separating ammonia from the circulating gas of the ammonia synthesis

DE1815532A1
(en)

1968-12-18
1970-06-25
Linde Ag

Process for generating cold

GB1274504A
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1969-09-30
1972-05-17
Petrocarbon Dev Ltd
Improvements in or relating to the synthesis of ammonia

GB1460681A
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1975-02-06
1977-01-06
Petrocarbon Dev Ltd
Treatment of ammonia synthesis purge gas

1978

1978-10-10
GB
GB7839880A
patent/GB2030973B/en
not_active
Expired

1979

1979-10-10
IN
IN1051/CAL/79A
patent/IN152360B/en
unknown

1979-10-10
IT
IT26382/79A
patent/IT1125479B/en
active

1979-10-10
US
US06/083,952
patent/US4255406A/en
not_active
Expired – Lifetime

Cited By (7)

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Publication number
Priority date
Publication date
Assignee
Title

EP0119001A2
(en)

1983-02-14
1984-09-19
Exxon Research And Engineering Company
Improved cryogenic production of ammonia synthesis gas

EP0119001A3
(en)

1983-02-14
1987-04-08
Exxon Research And Engineering Company
Improved cryogenic production of ammonia synthesis gas

US4592903A
(en)

1983-11-10
1986-06-03
Exxon Research & Engineering Co.
Low severity hydrocarbon steam reforming process

EP0160412A2
(en)

1984-04-25
1985-11-06
Imperial Chemical Industries Plc
Ammonia synthesis

EP0160412A3
(en)

1984-04-25
1988-12-28
Imperial Chemical Industries Plc
Ammonia synthesis

EP0247220A1
(en)

1986-05-27
1987-12-02
Roger Warren Parrish
Process for manufacture of ammonia

EP0282165A1
(en)

1987-03-02
1988-09-14
Air Products And Chemicals, Inc.
Method and plant for recovering hydrogen and argon from ammonia synthesis purge gas

Also Published As

Publication number
Publication date

IT1125479B
(en)

1986-05-14

IN152360B
(en)

1983-12-31

US4255406A
(en)

1981-03-10

IT7926382D0
(en)

1979-10-10

GB2030973B
(en)

1982-10-27

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