GB2096754A - Method of separating ammonia and hydrogen from ammonia synthesis gases - Google Patents
Method of separating ammonia and hydrogen from ammonia synthesis gases Download PDFInfo
- Publication number
- GB2096754A GB2096754A GB8210295A GB8210295A GB2096754A GB 2096754 A GB2096754 A GB 2096754A GB 8210295 A GB8210295 A GB 8210295A GB 8210295 A GB8210295 A GB 8210295A GB 2096754 A GB2096754 A GB 2096754A
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- GB
- United Kingdom
- Prior art keywords
- ammonia
- pressure
- gas
- hydrogen
- stage
- Prior art date
- 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.)
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Classifications
-
- 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
-
- 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
- C01C1/0458—Separation of NH3
- C01C1/047—Separation of NH3 by condensation
-
- 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
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Analytical Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Hydrogen, Water And Hydrids (AREA)
Abstract
The invention relates to a method for the complex separation of ammonia and hydrogen from the ammonia synthesis residual gases by means of partial condensation. The object of the invention is to minimise the expenditure of energy for the recompression of the hydrogen to be separated, to separate the liquid fractions (nitrogen, methane, argon, ammonia) with a minimal hydrogen content, and to obtain a maximum of ammonia from the flash gases. The problem is solved in that with a heat exchange of the individual fluids to be effected, the pressure of the let-down circuit gas is reduced in several stages, along with partial condensations, to pressures which are adapted to the suction pressures of the compression stages of the synthesis gas compressor and, in the case of the last flash stage, to the fuel gas system pressure. The problem is furthermore solved in that following an ammonia separation to be effected, the product flash gas I is adapted, with the hydrogen proportion thereof, to the suction pressure of the synthesis gas compressor and, with the liquid proportion thereof, to the fuel gas system pressure.
Description
SPECIFICATION
Method of separating ammonia and hydrogen from ammonia synthesis gases
The invention relates to the complex ammonia and hydrogen recovery from the ammonia
synthesis residual gases by making use of partial condensation.
There are known ammonia synthesis processes wherein the product flash gas I is either burnt as
fuel gas or is re-compressed to the pressure of the circuit let-down gas in order to be subjected with
this gas to an ammonia elutriation or an ammonia condensation by using an external refrigerating
circuit. Deficiencies of these solutions are the insufficient utilisation of the product flash gas I
materialwise during the combustion thereof or the non-exploitation of the pressure of the circuit let
down gas as well as the additional energy consumption for the separate refrigeration.In British Patent
1,460,681 it has been proposed to cool the purge gas stream, which was liberated from ammonia in a
manner not described in the patent, by means of flashing and to decompose it by a counter-flow
exchange and a partial condensation into residual gas and a hydrogen fraction which is returned to the
synthesis reactor. The disadvantages of this solution are that the pressure energy contained in the
purge gas and the refrigerating effect proportional to this energy is not utilised and that the hydrogen
fraction produced is passed to the suction side of the synthesis gas compressor, thus causing an
additional expenditure of energy, and that the useful materials contained in the purge gases are not
utilised.
It is the aim of the invention to minimise the expenditure of energy for the re-compression of the
hydrogen fractions from the circuit let-down gas, and to produce the liquid fractions (methane, argon,
nitrogen) with a minimal proportion of hydrogen, and to separate a maximum of ammonia from all flash
gases, and to re-use the hydrogen proportion of the product flash gas I.
It is the object of the invention to eliminate the deficiencies of the known solutions in that a
method making better use of the energy of the synthesis process is proposed for a very far-reaching
recovery of the ammonia and the hydrogen and for the return of the hydrogen into the reactor circuit
with a minimal expenditure of energy.
According to the invention, the method proceeds in that the pressure of the circuit let-down gas,
which has been purged from ammonia, is reduced in three stages in such a way that the pressure in the
first separator is adapted to the suction pressure of the third stage of the synthesis gas compressor and
the pressure in the second separator is adapted to the suction pressure of the first stage of the
synthesis gas compressor and the pressure in the third separator is adapted to the pressure of the fuel
gas system of the ammonia synthesis.The hydrogen fraction from the second flash stage is partly fed
into the product flash gas I fraction, which has a low ammonia content, and partly into the product flash
gas II fraction, which has a low ammonia content, in order to ensure that the necessary low
temperature close to the triple point of the ammonis is reached in the process stages of the ammonia
partial condensation. The hydrogen fraction of the third flash stage is utilised together with the
hydrogen fraction of the second flash stage in the hydrogen recovery from the product flash gas I for
cooling foreign media, e.g. nitrogen in argon plants, and is finally fed into a suitable fuel gas system.
Due to the removal of this gas and the fact that it is not returned to the synthesis circuit, there does not
occur any helium enrichment in the synthesis circuit.
The hydrogen from the product flash gases which is not required for setting the temperature of
the ammonia partial condensation is used either for the cooling and liquifying of circuit nitrogen in
downstream argon production plants or for the counter-flow cooling of the circuit let-down gas, the
fraction from the second separator being passed to the suction side of the synthesis gas compressor.
An exemplified embodiment will be described with reference to the accompanying drawing.
Circuit let-down gas (KEG) enters a complex hydrogen and ammonia separation plant through a
line 1, is cooled in a heat exchanger 9 to close to above the triple point of ammonia, and is fed through
a line 2 to a separator 12, in which the phase separation is effected. The liquid phase, the ammonia, is
withdrawn through the line 3, is reduced in pressure in the valve 1 is fed through the line 4 to the
heat exchanger 9, where it evaporates in a counter-flow to the circuit let-down gas and, in doing so, is
heated to close to the inlet temperature of the latter, before leaving the plant through the line 5. The
gas phase, which has been largely liberated from ammonia, is withdrawn from the separator through
the line 6, is reduced in pressure in the valve 10 to such an extent that the refrigeration requirement of
this plant part can be met thereby.Subsequently, there is effected via the line 7 in the heat exchanger
9 the heating thereof in a counter-flow to the circuit let-down gas up to close to the inlet temperature
of the latter. The heated gas phase is fed through the line 8 to the adsorber 13 for the removal of the
residual ammonia. The now ammonia-free circuit let-down gas enters the heat exchanger 38 through
the line 14, is subjected to cooling and partial condensation in the exchanger, emerges through the line 1 5 and is fed via the valve 1 6 to the separator 17, its pressure being so reduced that its is adapted to a
medium stage of the synthesis gas compressor.The gas phase, which is rich in hydrogen, leaves the
separator through the line 28, is then heated in the heat exchanger 38 to close to the inlet temperature
of the ammonia-liberated circuit let-down gas and is withdrawn from the plant through the line 29. The
liquid phase leaves the separator 17 through the line 18, is fed via the valve 1 9 to the separator 20, its pressure being so reduced that it is adapted to the pressure prevailing on the suction side of the synthesis gas compressor.The gas phase, which is rich in hydrogen, leaves the separator 20 through the line 30, is introduced both through the valve 39 and the line 40 and through the line 76, the valve 77 and the line 78 into the product flash gases which have been largely purged from ammonia and which are the product flash gas I and the fuel gas stream III, in order to provide the necessary refrigerating effect for these plant parts. That proportion of the hydrogen fraction from the separator 20 which is not required for meeting the necessary aforementioned refrigerating effect enters the heat exchanger 43 through the line 31 and leaves this exchanger through the line 32, during which process there is effected the cooling of nitrogen or other media (e.g. in argon production plants), which flow through the heat exchanger 43 through the lines 41 and 42.This proportion of the hydrogen fraction may be fed through the line 33 to the heat exchanger 38 and may then leave this exchanger in a heated state through the line 34.
The liquid fraction from the separator 20 passes through the line 21 and the valve 22 into the separator 23, its pressure being reduced, so as to minimise by this means the hydrogen content of the
liquid fraction. The pressure in the separator 23 is adapted to the pressure of the fuel gas system. The liquid fraction, in which only a few tenths percent of hydrogen are left, is withdrawn through the line 24, is regulated with respect to quantity by means of the valve 25, is fed through the line 26 to the heat exchanger 38 and is abducted therefrom through the line 27.The phase rich in hydrogen is withdrawn through the line 35 and is mixed via the line 68 with the hydrogen fraction arriving through the line 69, is then fed through the line 70 to the heat exchanger 75, in which it is heated against nitrogen or other media to be cooled, which pass through the heat exchanger 75 through the lines 73 and 74, before it emerges through the line 72. However, this hydrogen fraction may be fed through the line 36 to the heat exchanger 38 and may be withdrawn therefrom in a heated state through the line 37.
Product flash gas I (PEG I) enters the heat exchanger 54, and thus the plant, through the line 48, is initially cooled down to close to above the triple point of the ammonia and is passed through the line 49 into the separator 47. From this separator ammonia is withdrawn in a liquid state through the line 50, is reduced in pressure by means of the valve 51 to a gauge pressure of a few hundredths MPa, is fed through the line 52 to the heat exchanger 54, is heated therein in a counter-flow to the product flash gas I and is abducted from the plant through the line 53.The product flash gas I, which has been liberated from ammonia in the separator 47 to a very large extent, is withdrawn from the separator through the line 44, is slightly cooled by means of the hydrogen fraction fed from the line 40 and is fed through the line 45 to the heat exchanger 54, is heated therein in a counter-flow to the product flash gas I to close to the inlet temperature of the latter and is fed through the line 46 to the adsorber 55 for the purpose of removing the residual ammonia.
Ammonia-free product flash gas I subsequently enters the heat exchanger 60 through the line 56, is cooled and partially condensed in this exchanger, and is subsequently separated into a gas phase and a liquid phase in the separator 61 via the line 57. The gas phase rich in hydrogen leaves the separator through the line 58, passes into the heat exchanger 60, wherein it is heated to close to the inlet temperature of the product flash gas I, which has been liberated from ammonia, and is removed from the plant through the line 59.
The liquid phase leaves the separator 61 through the line 62 and is passed via the valve 63 to the separator 64, its pressure being so reduced that it is adapted to the fuel gas system. The liquid fraction, in which only a few tenths percent of hydrogen are left, is withdrawn through the line 65, is regulated with respect to quantity by means of the valve 71, is then fed to the heat exchanger through the line 66 and is abducted from this exchanger as fuel gas II through the line 67.
The gas phase, which is rich in hydrogen, passes through the line 69 into the line 68, wherein it is mixed with the hydrogen fraction, which flows therein, from the separator 23.
A product flash gas II enters the plant through the line 86, is cooled in the heat exchanger 88 to close to above the triple point of the ammonia and is fed through the line 87 to the separator 81.
Ammonia is withdrawn therefrom through the line 82, is reduced in pressure by means of the valve 83 to a gauge pressure of a few hundredths MPa, is thereafter heated through the line 84 in the heat exchanger 88 in a counter-flow to the product flash gas II, and is subsequently abducted from the plant through the line 85. The product flash gas II containing only traces of ammonia is withdrawn from the separator 81 through the line 79, is slightly cooled by the addition of the medium-pressure hydrogen fraction from the line 78 and is fed to the heat exchanger 88. Therein, it is heated in a counter-flow to the still untreated product flash gas II to close to the inlet temperature of the latter and is then abducted from the plant as fuel gas III through the line 80.
An addition of proportions of the medium-pressure hydrogen fraction to the plant parts serving for separating ammonia from the product flash gases may be effected in the lines 49 and 87 before the gas enters the separators 47 and 81 respectively.
Hereinafter, there are shown selected values of state, the points of state corresponding to the
numbering given in Figure 1.
Table of selected parameters of the plant part "Decomposition of the circuit let-down gas"
Points of state 1 5 8 29 18 30 21 35 27
Quantity proportion 1.065 0.065 1.0 0.597 0.403 0.0433 0.3597 0.0231 0.3366
Pressure MPa 32 0.15 20 10.5 10.5 3.0 3.0 0.35 0.35
Concentrations
% by volume H2 57.70 0 61.6 93.99 13.53 93.89 4.30 61.44 0.33
N2 18.87 20.1 4.25 43.73 5.31 56.26 34.99 57.74
Ar 4.85 0.2 5.3 0.88 11.92 0.60 13.49 3.04 14.21
CH4 12.02 12.9 0.88 30.82 0.20 25.95 0.53 27.72
NH3 6.56 99.8 0.1 0 0 0 0 0 0
Table of selected parameters of the plant parts "Decomposition of the product flash gases I and II"
PEG/ PEG//
Points of state 48 46 53 56 59 67 62 86 80 85
Quantity proportion 1.0 0.961 0.079 0.961 0.521 0.41 0.44 1 0.764 0.2364
Pressure MPa 2.3 2.1 0.11 2.0 1.9 0.35 1.9 1.63 1.63 0.11
Concentrations
% by volume H2 41.0 46.71 46.71 81.95 0.08 0.17 17.80 23.31
N2 15.0 15.85 0.01 15.85 14.80 18.00 18.09 7.40 9.69 0.01
Ar 4.8 4.88 4.88 1.96 9.09 9.07 2.60 3.40
CH4 31.0 32.22 0.09 32.22 1.29 72.83 72.67 48.30 62.22 0.11
NH3 8.2 0.34 99.9 0.34 - - - 23.90 0.38 99.88
Claims (6)
1. A method for the separation of ammonia and hydrogen from the ammonia synthesis gases by partial condensation without using external refrigeration, in that the circuit let-down gas having the pressure of the synthesis loop or a pressure below this pressure is liberated from ammonia to a very large extent in a condensation stage (9/12) at approx. 200 K, and downstream of the NH3 separator (12) is reduced in pressure at the most to a pressure that prevails on the suction side of the second or third stage of the synthesis gas compressor, whereafter there is effected the adsorptive fine purging from residual ammonia, which is to be carried out in known manner and which is followed by a three-stage partial condensation in such a way that upstream of a separator (17) of the first condensation stage there is effected-in accordance with the pressure adjustment in the ammonia condensation process section-the pressure adjustment to the value that is adapted to the suction side of the second or third stage of the synthesis gas compressor and the high-pressure hydrogen fraction obtained in the first separator (17) is fed, following heating in the heat exchanger (38), to the suction side of the second or third stage of the synthesis gas compressor, whereas the pressure of the liquid fraction from the separator (1 7) is reduced to a value that is adapted to the suction side of the first stage of the synthesis gas compressor, and in that the thus formed medium-pressure hydrogen fraction is fed in a partial quantity to the ammonia condensation stage (54, 47) of the product flash gas I for setting the separation temperature of approx.
200 K of the low-ammonia fraction formed in the separator (47) and with a second partial quantity is used for setting the separation temperature of approx. 200 K in the ammonia condensation stage (88/81) of the product flash gas II and with a third partial quantity is employed for the cooling of nitrogen in a downstream argon production plant (43) or in the heat exchanger (38) of the circuit letdown gas proportion for cooling, and in'that the liquid fraction from the third separation stage (23) is heated in the heat exchanger (38) of the circuit let-down gas proportion and is fed to the fuel gas system, whereas the low-pressure hydrogen fraction of this separation stage (23) is combined with the low-pressure hydrogen fraction of the hydrogen recovery proportion of the product flash gas I decomposition and is used for N2 cooling, and in that the product flash gas I, which has been purged from NH3 in the NH3 condensation stage (54/47) and the downstream NH3 residual adsorption unit (55), is partially condensed in a first condensation stage (61) at a pressure that has been adapted to the suction pressure of the synthesis gas compressor and the pressure of the liquid phase obtained during this process is reduced in a second condensation stage (64) to a pressure that is adapted to the fuel gas system, the liquid fraction from this second separation stage (64) being heated in the heat exchanger (60) of the product flash gas I proportion and is fed to the fuel gas system, whereas the hydrogen fraction obtained in the first condensation stage is heated in the heat exchanger (60) and is fed to the suction side of the synthesis gas compressor, and in that the product flash gas II is purged from NH3 to a very large extent in a condensation stage (88/81) by condensation of the NH3, during which process the necessary temperature of approx. 200 K is set by the addition of a partial quantity of the medium-pressure hydrogen fraction from the separator (20) and the product flash gas II purged from NH3 is fed to the fuel gas system.
2. A method as claimed in Claim 1, characterised in that the helium content in the synthesis loop is kept constant with the low-ammonia fraction from the plant part for ammonia separation (88/81) from the product flash gas 11.
3. A method as claimed in Claim 1, characterised in that the quantities of the medium-pressure and low-pressure hydrogen fractions which are required for setting the temperature in the separators (47 and 81) of the ammonia condensation stages of the product flash gases are controlled according to the temperatures of the respective product flash gases entering the separators.
4. A method as claimed in Claims 1 and 3, characterised in that the medium-pressure hydrogen fraction formed is re-compressed to the plant inlet pressure of the gas used in the synthesis.
5. A method as claimed in Claims 1 and 3, characterised in that instead of being delivered into the fuel gas system, the liquid fractions from the separators (23 and 64) are fed to an adjacent or downstream argon production plant for the complete recovery of the argon, nitrogen and methane content.
6. A method for the separation of ammonia and hydrogen from ammonia synthesis gases as claimed in Claim 1 and substantially as described herein.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DD81229173A DD160409A1 (en) | 1981-04-13 | 1981-04-13 | SEPARATION OF AMMONIA AND HYDROGEN FROM GASEN |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2096754A true GB2096754A (en) | 1982-10-20 |
| GB2096754B GB2096754B (en) | 1984-11-14 |
Family
ID=5530316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8210295A Expired GB2096754B (en) | 1981-04-13 | 1982-04-07 | Method of separating ammonia and hydrogen from ammonia synthesis gases |
Country Status (3)
| Country | Link |
|---|---|
| DD (1) | DD160409A1 (en) |
| DE (1) | DE3211041A1 (en) |
| GB (1) | GB2096754B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0160412A2 (en) * | 1984-04-25 | 1985-11-06 | Imperial Chemical Industries Plc | Ammonia synthesis |
| CN107228526A (en) * | 2017-07-03 | 2017-10-03 | 成都深冷液化设备股份有限公司 | A kind of LNG flashed vapours carry helium, denitrogenation and reliquefaction installation |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3553972A (en) * | 1968-11-19 | 1971-01-12 | American Messer Corp | Cryogenic recovery of hydrogen from ammonia synthesis gas |
| GB1460681A (en) * | 1975-02-06 | 1977-01-06 | Petrocarbon Dev Ltd | Treatment of ammonia synthesis purge gas |
-
1981
- 1981-04-13 DD DD81229173A patent/DD160409A1/en not_active IP Right Cessation
-
1982
- 1982-03-25 DE DE19823211041 patent/DE3211041A1/en active Granted
- 1982-04-07 GB GB8210295A patent/GB2096754B/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN107228526A (en) * | 2017-07-03 | 2017-10-03 | 成都深冷液化设备股份有限公司 | A kind of LNG flashed vapours carry helium, denitrogenation and reliquefaction installation |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2096754B (en) | 1984-11-14 |
| DE3211041C2 (en) | 1992-05-14 |
| DE3211041A1 (en) | 1982-12-30 |
| DD160409A1 (en) | 1983-07-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |