CN111634883B - Pretreatment method and system for synthesis ammonia feed gas - Google Patents

Pretreatment method and system for synthesis ammonia feed gas Download PDF

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CN111634883B
CN111634883B CN202010475706.9A CN202010475706A CN111634883B CN 111634883 B CN111634883 B CN 111634883B CN 202010475706 A CN202010475706 A CN 202010475706A CN 111634883 B CN111634883 B CN 111634883B
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low
heat exchanger
temperature
plate
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CN111634883A (en
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梁威
刘海军
李忙刚
李腾
董博
王小宁
王连喜
柴自高
张长江
刘浩
谢辉
李�杰
唐小龙
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Xian Shaangu Power Co Ltd
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    • 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
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
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    • 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
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
    • F25J3/0219—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
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    • 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
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    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
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    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
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    • F25J3/0257—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of nitrogen
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    • 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
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
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    • F25J3/0276—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of H2/N2 mixtures, i.e. of ammonia synthesis gas
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    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
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    • F25J3/028—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of noble gases
    • F25J3/0285—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of noble gases of argon
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    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04769—Operation, control and regulation of the process; Instrumentation within the process
    • F25J3/04793—Rectification, e.g. columns; Reboiler-condenser
    • F25J3/048—Argon recovery
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
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    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • 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
    • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
    • C01B2203/1258—Pre-treatment of the feed
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/02—Processes or apparatus using separation by rectification in a single pressure main column system
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/72—Refluxing the column with at least a part of the totally condensed overhead gas
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    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/32—Compression of the product stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • F25J2270/00—Refrigeration techniques used
    • F25J2270/14—External refrigeration with work-producing gas expansion loop
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    • F25J2270/00—Refrigeration techniques used
    • F25J2270/42—Quasi-closed internal or closed external nitrogen refrigeration cycle
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Abstract

A pretreatment method and system for synthesis ammonia feed gas comprises a dehydration device, a mercury removal device and a cryogenic separation device; the dehydration device is used for cooling and dehydrating the raw material gas; the mercury removal device is used for removing mercury from the dehydrated raw gas output by the dehydration device and purifying the dehydrated raw gas; the cryogenic separation device comprises a plate-fin heat exchanger group and is used for cooling the purified raw material gas output by the mercury removal device and outputting low-temperature purified raw material gas; the cryogenic separation device also comprises a gas-liquid separation unit, wherein the gas-liquid separation unit is used for separating the low-temperature purified raw gas output by the plate-fin heat exchanger group into gas and liquid to output low-temperature purified gas, and the low-temperature purified gas is heated by the plate-fin heat exchanger group to obtain the raw gas after ammonia synthesis and purification. Through reasonable setting to part structure, impurity in the high-efficient desorption ammonia synthesis feed gas to make a CNG product export with impurity gas through the mode of rectification purification, increase product added value, adopt circulating nitrogen gas booster expansion simultaneously, improve the energy efficiency, reduce whole device transformation cost and operation consumption.

Description

Pretreatment method and system for synthesis ammonia feed gas
Technical Field
The invention belongs to the technical field of coal chemical industry, and particularly relates to a pretreatment method and a pretreatment system for synthesis ammonia feed gas.
Background
The ammonia synthesis reaction in the ammonia synthesis device is a core section of the whole device and is also an important section for determining the energy consumption of the whole device, the ammonia synthesis reaction has strict requirements on the N/H ratio and the content of the synthesis ammonia raw material gas, and the ammonia synthesis reaction can cause the reduction of the reaction efficiency and the increase of the energy consumption of the ammonia synthesis device for impurity gases and inert gases such as methane, argon and the like in the synthesis ammonia raw material gas component.
At present, in the national process of updating and eliminating the traditional normal pressure coal gasification mode, the main components of the ammonia synthesis feed gas generated by new alternative coal gasification are as follows: hydrogen (67-72 mol%), nitrogen (22-24 mol%), methane (4-10 mol%), argon (0.4-0.6 mol%), water (saturated state), and methane and argon are not involved in the reaction as inert gases in the ammonia synthesis section, and consume a great deal of idle work in the compression and reaction processes of the system, so that the energy consumption of the system is increased and the net value of ammonia synthesis is reduced, which brings serious challenges to the ammonia synthesis section of the ammonia synthesis factory. Therefore, the methane and the argon in the feed gas of the synthetic ammonia are effectively removed, and the methane product with economic value is prepared, so that the added value of the device is improved, and the method has important practical significance and technical advancement.
Disclosure of Invention
The invention aims to provide a pretreatment method and a pretreatment system for synthesis ammonia feed gas, which are used for efficiently removing impurities in the ammonia synthesis feed gas, preparing impurity gas into CNG (compressed natural gas) product for output in a rectification and purification mode, increasing the added value of the product, simultaneously adopting circulating nitrogen to pressurize and expand, improving the energy efficiency and reducing the transformation cost and the operation consumption of the whole device.
In order to solve the technical problems, the invention adopts the following technical scheme:
the pretreatment method of the synthesis ammonia feed gas specifically comprises the following steps:
S1, cooling ammonia synthesis feed gas to 10-20 ℃ and removing water in the feed gas to 1ppmv;
S2, removing trace mercury from the dehydrated feed gas output by the S1 to 0.01 mug/Nm 3, and removing dust to obtain purified feed gas;
S3, cooling the purified raw material gas output by the S2 to-160 to-175 ℃, and then performing gas-liquid two-phase separation to separate low-temperature purified gas I and first methane low-temperature liquid, wherein the temperature of the low-temperature purified gas I is-160 to-175 ℃, and the mole percentage of methane is 0.83-0.98%;
S4, heating the first methane low-temperature liquid separated in the S3 to-130 to-150 ℃, and then performing pressure-reducing gas-liquid two-phase separation to separate low-temperature purified gas II and second methane low-temperature liquid, wherein the pressure of the low-temperature purified gas II is 3.0-4.0 MPa (G), the temperature is-140 to-150 ℃, and the methane mole percentage is 1.9-2.5%;
s5, heating the low-temperature purified gas I of S3 to obtain ammonia synthesis purified raw material gas I, heating the low-temperature purified gas II of S4 to compress and purify, and cooling to obtain ammonia synthesis purified raw material gas II;
S6, mixing the raw material gas I after ammonia synthesis and purification with the raw material gas II after ammonia synthesis and purification, and cooling the mixed raw material gas after ammonia synthesis and purification to obtain purified gas, wherein the temperature of the purified gas is between-180 ℃ and-200 ℃, and the mole percentage of methane is 0.85% -1.02%;
Preferably, the method further comprises:
s71, throttling and reducing the second methane low-temperature liquid of the S4 to 0.8-1.3 MPa (G), and separating gas phase and liquid phase to obtain liquid methane, wherein the molar content of methane in the liquid methane is 92-95%;
And S72, heating the liquid methane in the step S71 to obtain the compressed natural gas.
Preferably, the nitrogen expansion refrigeration comprises:
S81, compressing and cooling the nitrogen at normal temperature and low pressure, cooling the nitrogen at low temperature to-90 to-120 ℃, and further pressurizing, expanding and refrigerating to obtain the nitrogen at low temperature, wherein the temperature of the nitrogen at low temperature is-180 to-190 ℃ and the pressure is 0.03-0.06 MPa (G);
s82, providing cold energy for gas-liquid two-phase separation in S6 by a part of the expansion low-temperature nitrogen;
S83, heating the other part of the expansion low-temperature nitrogen, and returning to S71 for circulation.
A pretreatment system for synthesis ammonia feed gas comprises a dehydration device, a mercury removal device and a cryogenic separation device; the dehydration device is used for cooling and dehydrating the raw material gas; the mercury removal device is used for removing mercury from the dehydrated raw gas output by the dehydration device and purifying the dehydrated raw gas; the cryogenic separation device comprises a plate-fin heat exchanger group and is used for cooling the purified raw material gas output by the mercury removal device and outputting low-temperature purified raw material gas; the cryogenic separation device also comprises a gas-liquid separation unit, wherein the gas-liquid separation unit is used for separating the low-temperature purified raw gas output by the plate-fin heat exchanger group into gas and liquid to output low-temperature purified gas, and the low-temperature purified gas is heated by the plate-fin heat exchanger group to obtain the raw gas after ammonia synthesis and purification.
Preferably, the gas-liquid separation unit further separates low-temperature purified raw material gas output by the plate-fin heat exchanger group into gas and liquid to output liquid methane, and the liquid methane is heated by the plate-fin heat exchanger group to obtain compressed natural gas; the molar content of methane in the liquid methane is 92-95%.
Preferably, the gas-liquid separation unit comprises a first dehydrogenation separator, the input end and the output end of the first dehydrogenation separator are connected with the plate-fin heat exchanger group, and the first dehydrogenation separator is used for separating gas and liquid of low-temperature purified raw gas output by the plate-fin heat exchanger group and outputting low-temperature purified gas I and first methane low-temperature liquid; heating the low-temperature purified gas I through a plate-fin heat exchanger group to obtain raw material gas I after ammonia synthesis and purification;
The gas-liquid separation unit also comprises a second dehydrogenation separator, the input end and the output end of the second dehydrogenation separator are connected with the plate-fin heat exchanger group, the first methane low-temperature liquid is subjected to pressure reduction gas-liquid two-phase separation through the second dehydrogenation separator after being heated by the plate-fin heat exchanger group, and the low-temperature purified gas II and the second methane low-temperature liquid are output; heating the low-temperature purified gas II through a plate-fin heat exchanger group to obtain raw material gas II after ammonia synthesis and purification;
The gas-liquid separation unit also comprises a methane rectifying tower, the input end of the methane rectifying tower is connected with the output end of the second dehydrogenation separator, and the output end of the methane rectifying tower is connected with the plate-fin heat exchanger group; the methane rectifying tower is used for carrying out gas-liquid two-phase separation on the second methane low-temperature liquid output by the second dehydrogenation separator and outputting liquid methane and non-condensable gas; the liquefied natural gas is obtained after the temperature of the liquid methane is raised by the plate-fin heat exchanger group, and the non-condensable gas is sent out of the cryogenic separation device after the temperature of the non-condensable gas is raised by the plate-fin heat exchanger group.
Further, the device also comprises a nitrogen expansion refrigeration device, which is used for circularly refrigerating the circulated nitrogen through compression, cooling and supercharging expansion to provide cold energy for the cryogenic separation device; the nitrogen expansion refrigeration device comprises a nitrogen compressor and a second cooler which are sequentially connected with the plate-fin heat exchanger group and used for compressing and cooling normal-temperature low-pressure nitrogen, the output end of the second cooler is connected with the plate-fin heat exchanger group, and the compressed and cooled nitrogen is further cooled through the plate-fin heat exchanger group; the nitrogen expansion refrigeration device also comprises a booster expander, wherein the input end and the output end of the booster expander are connected with the plate-fin heat exchanger group and are used for further pressurizing and expanding the high-pressure low-temperature nitrogen output by the plate-fin heat exchanger group for refrigeration and outputting the expanded low-temperature nitrogen; and (3) providing cold energy for the methane rectifying tower by one part of the expansion low-temperature nitrogen, heating the other part of the expansion low-temperature nitrogen by a plate-fin heat exchanger group, and inputting the heated part of the expansion low-temperature nitrogen into a nitrogen compressor for circulation.
Further, the device also comprises a purified gas compression module, which is used for compressing the low-temperature purified gas II purified gas after heating the plate-fin heat exchanger group and outputting the raw gas II after synthesizing and purifying ammonia; the purifying gas compression module comprises a purifying gas compressor and a third cooler which are sequentially connected, and the low-temperature purifying gas II after the temperature rise of the plate-fin heat exchanger group is compressed and purified by the purifying gas compressor and then cooled by the third cooler, so that the raw material gas II after the ammonia synthesis and purification is obtained.
Preferably, the mercury removal device comprises a mercury removal tower and a dust filter which are connected in sequence, the dehydrated raw material gas output by the dehydration device is subjected to mercury removal by the mercury removal tower, and then the purified raw material gas is obtained after dust removal by the dust filter; the dehydration device comprises a first cooler, a dehydrator and a drying tower which are connected in sequence, raw material gas is cooled by the first cooler, and dehydrated by the dehydrator and the drying tower to obtain dehydrated raw material gas.
Preferably, the purified feed gas I for ammonia synthesis and the purified feed gas II for ammonia synthesis are mixed and cooled by a first cooler to obtain purified gas.
Compared with the prior art, the invention has the advantages that:
(1) According to the pretreatment method and the pretreatment system for the synthesis ammonia feed gas, impurities in the ammonia synthesis feed gas are removed by adopting a cryogenic separation and low-temperature rectification method, the methane component in the ammonia synthesis feed gas is reduced to be less than or equal to 1.2%, the recovery rate of hydrogen in the ammonia synthesis feed gas is ensured to be more than or equal to 99.5% while the methane component in the ammonia synthesis feed gas is reduced, the purification requirement and the hydrogen recovery rate requirement of the ammonia synthesis feed gas are met, and the impurity gas is produced into a CNG product through rectification purification, so that the added value of the product is increased.
(2) The pretreatment method and the pretreatment system for the feed gas of the synthetic ammonia, disclosed by the invention, adopt a circulating nitrogen pressurizing expansion flow for refrigeration, simplify the flow of cryogenic separation of methane from the feed gas of the synthetic ammonia, greatly reduce the investment and the occupied area of a refrigerant proportioning system required by a mixed refrigerant compressor, reduce the device transformation cost, and are very suitable for the transformation project of the old synthetic ammonia device.
(3) According to the pretreatment method and the pretreatment system for the feed gas of the synthetic ammonia, through reasonable arrangement of the component structure, the first cooler and the dehydrator are arranged in the dehydration device, and through cooling and coarse removal of saturated water in the feed gas, the adsorption effect of the drying tower of the dehydration device can be greatly improved, the regeneration energy consumption base of the adsorbent of the drying tower is effectively reduced, the service cycle of the adsorbent of the drying tower of the device is prolonged, and the overall operation consumption of the device is reduced.
Drawings
FIG. 1 is a schematic diagram of the connection of the modules of the present invention;
Fig. 2 is a schematic view of the device connection of the present invention.
Meaning of the individual reference numerals in the drawings:
1-dehydration device, 2-mercury removal device, 3-cryogenic separation device, 4-nitrogen expansion refrigeration device and 5-purified gas compression module; 11-a first cooler, 12-a dehydrator and 13-a drying tower; 14-a mercury removal tower, 15-a dust filter; 16-plate-fin heat exchanger group, 17-first dehydrogenation separator, 18-first throttle valve, 19-second dehydrogenation separator, 20-second throttle valve, 21-methane rectifying tower; 22-nitrogen compressor, 23-second cooler, 24-booster expander; 25-a purge gas compressor, 26-a third cooler.
The details of the invention are explained in further detail below with reference to the drawings and the detailed description.
Detailed Description
The following specific embodiments of the present application are provided, and it should be noted that the present application is not limited to the following specific examples, and all equivalent changes made on the basis of the technical scheme of the present application fall within the protection scope of the present application.
In the present invention, unless otherwise indicated, terms of orientation such as "upper" and "lower" are used generally with reference to the drawings in which corresponding figures are drawn, and "inner" and "outer" are defined with reference to the inner and outer of the corresponding component profiles.
The ammonia synthesis feed gas of the invention comprises the following main components: hydrogen (67-72 mol%), nitrogen (22-24 mol%), methane (4-10 mol%), argon (0.4-0.6 mol%), water (saturated state), and removing impurities from the ammonia synthesis feed gas by cryogenic separation and low-temperature rectification, wherein the methane component in the ammonia synthesis feed gas is reduced to 0.85-1.02 mol%, and the pretreated purified gas argon is 0.33-0.35 mol% as supplementary assessment indexes.
The pretreatment method of the synthesis ammonia feed gas specifically comprises the following steps:
S1, cooling ammonia synthesis feed gas to 10-20 ℃ and removing water in the feed gas to 1ppmv;
S2, removing trace mercury from the dehydrated feed gas output by the S1 to 0.01 mug/Nm 3, and removing dust to obtain purified feed gas;
S3, cooling the purified raw material gas output by the S2 to-160 to-175 ℃, and then performing gas-liquid two-phase separation to separate low-temperature purified gas I and first methane low-temperature liquid, wherein the temperature of the low-temperature purified gas I is-160 to-175 ℃, and the mole percentage of methane is 0.83-0.98%;
S4, heating the first methane low-temperature liquid separated in the S3 to-130 to-150 ℃, and then performing pressure-reducing gas-liquid two-phase separation to separate low-temperature purified gas II and second methane low-temperature liquid, wherein the pressure of the low-temperature purified gas II is 3.0-4.0 MPa (G), the temperature is-140 to-150 ℃, and the methane mole percentage is 1.9-2.5%;
s5, heating the low-temperature purified gas I of S3 to obtain ammonia synthesis purified raw material gas I, heating the low-temperature purified gas II of S4 to compress and purify, and cooling to obtain ammonia synthesis purified raw material gas II;
S6, mixing the raw material gas I after ammonia synthesis and purification with the raw material gas II after ammonia synthesis and purification, and cooling the mixed raw material gas after ammonia synthesis and purification to obtain purified gas, wherein the temperature of the purified gas is between-180 ℃ and-200 ℃, and the mole percentage of methane is 0.85% -1.02%;
the temperature rise of the first methane low-temperature liquid, the low-temperature purified gas I and the low-temperature purified gas II is realized by heat exchange with the input purified raw material gas;
The function is as follows: the methane component in the ammonia synthesis feed gas is reduced to less than or equal to 1.2 percent, so that the purification requirement of the ammonia synthesis feed gas and the hydrogen recovery rate requirement are met.
Specifically, the method further comprises the following steps: s71, throttling and reducing the second methane low-temperature liquid of the S4 to 0.8-1.3 MPa (G), and separating gas phase and liquid phase to obtain liquid methane, wherein the molar content of methane in the liquid methane is 92-95%; s72, heating the liquid methane in the step S71 to obtain compressed natural gas;
The function is as follows: the recovery rate of hydrogen in the ammonia synthesis feed gas is ensured to be more than or equal to 99.5 percent while the methane component in the ammonia synthesis feed gas is reduced, and impurity gas is prepared into CNG products for output in a rectifying and purifying mode, so that the added value of the products is increased.
Specifically, the method further comprises the following steps:
S81, compressing and cooling the nitrogen at normal temperature and low pressure, cooling the nitrogen at low temperature to-90 to-120 ℃, and further pressurizing, expanding and refrigerating to obtain the nitrogen at low temperature, wherein the temperature of the nitrogen at low temperature is-180 to-190 ℃ and the pressure is 0.03-0.06 MPa (G);
s82, providing cold energy for gas-liquid two-phase separation in S6 by a part of the expansion low-temperature nitrogen;
s83, heating the other part of the expansion low-temperature nitrogen, and returning to S71 for circulation;
The function is as follows: the refrigeration adopts a circulating nitrogen pressurizing expansion process, so that the process of cryogenic separation of methane from ammonia synthesis raw material gas is simplified, and the refrigerant proportion required by a mixed refrigerant compressor is greatly reduced.
A pretreatment system for synthesis ammonia feed gas comprises a dehydration device 1, a mercury removal device 2 and a cryogenic separation device 3;
The dehydration device 1 is used for cooling and dehydrating the raw material gas; the function is as follows: cooling ammonia synthesis feed gas (7.0-8.0 MPa (G), 40 ℃) from an upstream working section to 10-20 ℃, and removing water in the feed gas to 1ppmv to perform the next stage mercury removal, thereby achieving the purpose of improving the mercury removal process efficiency;
The mercury removal device 2 is used for removing mercury from and purifying the dehydrated raw gas output by the dehydration device 1; the function is as follows: the dehydrated feed gas sulfur-impregnated activated carbon is subjected to removal of trace mercury to 0.01 mug/Nm 3, dust filtration and purification are carried out to remove 99.9% of particles with the particle diameter of more than 5 mu m, the feed gas H2O less than or equal to 1ppmv and Hg less than or equal to 0.01 mug/Nm 3 entering the next stage of cryogenic separation process is ensured, and the purpose of improving the efficiency of the cryogenic separation process is achieved;
The cryogenic separation device 3 comprises a plate-fin heat exchanger group 16, wherein the plate-fin heat exchanger group 16 is used for cooling the purified raw material gas output by the mercury removal device 2 and outputting low-temperature purified raw material gas; the cryogenic separation device 3 further comprises a gas-liquid separation unit, wherein the gas-liquid separation unit is used for separating the low-temperature purified raw gas output by the plate-fin heat exchanger group 16 into gas and liquid to output low-temperature purified gas, and the low-temperature purified gas is heated by the plate-fin heat exchanger group 16 to obtain raw gas after ammonia synthesis and purification;
The function is as follows: the purified raw gas after dehydration and mercury removal is cooled to low-temperature purified raw gas (-160 to minus 175 ℃) through a plate-fin heat exchanger group 16, the low-temperature purified gas (0.85 to 1.02 mol percent of methane and 0.33 to 0.35 mol percent of argon) is separated by a gas-liquid separation unit, the low-temperature purified gas exchanges heat with the purified raw gas through the plate-fin heat exchanger group 16 and is heated, and then the ammonia synthesized purified raw gas is output, and the methane component in the raw gas after ammonia synthesis purification is reduced to less than or equal to 1.2 percent, so that the purification requirement of the ammonia synthesized raw gas is met.
Specifically, the gas-liquid separation unit further separates the low-temperature purified raw material gas output by the plate-fin heat exchanger group 16 into gas and liquid to output liquid methane, and the liquid methane is heated by the plate-fin heat exchanger group 16 to obtain compressed natural gas; the molar content of methane in the liquid methane is 92% -95%;
The function is as follows: the low-temperature purified raw material gas (-160 to-175 ℃) output by the plate-fin heat exchanger group 16 is separated by a gas-liquid separation unit to obtain liquid methane, and the liquid methane exchanges heat with the purified raw material gas through the plate-fin heat exchanger group 16 and heats up to output compressed natural gas, so that the purification requirement of the ammonia synthesis raw material gas is met, and meanwhile, the recovery rate of hydrogen in the ammonia synthesis raw material gas is ensured to be more than or equal to 99.5%, and the hydrogen recovery rate requirement of the ammonia synthesis raw material gas is met; and impurity gas is prepared into CNG products (liquefied natural gas) through rectification and purification, so that the added value of the products is increased.
The gas-liquid separation unit comprises a first dehydrogenation separator 17, the input end and the output end of the first dehydrogenation separator 17 are connected with the plate-fin heat exchanger group 16, the first dehydrogenation separator 17 is used for separating gas and liquid of low-temperature purified raw gas output by the plate-fin heat exchanger group 16 and outputting low-temperature purified gas I and first methane low-temperature liquid; the low-temperature purified gas I is heated by a plate-fin heat exchanger group 16 to obtain raw material gas I after ammonia synthesis and purification;
The function is as follows: the first dehydrogenation separator 17 separates the gas phase and the liquid phase of the low-temperature purified raw material gas to obtain low-temperature purified gas I (-160 to-175 ℃ and methane mole percent less than or equal to 1%) and first methane low-temperature liquid (-160 to-175 ℃ and methane mole percent of 23 to 38%, nitrogen mole percent of 58 to 71% and hydrogen mole percent of 4 to 6%), and the low-temperature purified gas I is subjected to heat exchange and temperature rise with the purified raw material gas through the plate-fin heat exchanger group 16 to obtain ammonia synthesized purified raw material gas I (30 to 40 ℃ and methane mole percent less than or equal to 1%), and the first methane low-temperature liquid is subjected to the next separation process;
The gas-liquid separation unit further comprises a second dehydrogenation separator 19, the input end and the output end of the second dehydrogenation separator 19 are connected with the plate-fin heat exchanger group 16, the first methane low-temperature liquid is subjected to temperature rise through the plate-fin heat exchanger group 16 and then subjected to pressure reduction gas-liquid two-phase separation through the second dehydrogenation separator 19, and low-temperature purified gas II and second methane low-temperature liquid are output; heating the low-temperature purified gas II through a plate-fin heat exchanger group 16 to obtain raw gas II after ammonia synthesis and purification;
The function is as follows: the second dehydrogenation separator 19 separates the first methane low-temperature liquid into a gas-liquid two-phase by pressure reduction again, separates low-temperature purified gas II (3.0-4.0 MPa, -130-150 ℃ and methane mole percent less than or equal to 3.5%) and second methane low-temperature liquid, and carries out heat exchange and temperature rise on the low-temperature purified gas II and the purified raw gas through the plate-fin heat exchanger group 16 to obtain raw gas II (30-40 ℃ and methane mole percent less than or equal to 3.5%) after ammonia synthesis and purification, and the second methane low-temperature liquid carries out the next separation procedure;
Wherein the first methane low-temperature liquid is sent to the second dehydrogenation separator 19 through the first throttle valve 18 after being heated by the plate-fin heat exchanger group 16;
The gas-liquid separation unit further comprises a methane rectifying tower 21, the input end of the methane rectifying tower 21 is connected with the output end of the second dehydrogenation separator 19, and the output end of the methane rectifying tower 21 is connected with the plate-fin heat exchanger group 16; the methane rectifying tower 21 is used for performing gas-liquid two-phase separation on the second methane low-temperature liquid output by the second dehydrogenation separator 19, and outputting liquid methane and non-condensable gas; heating liquid methane by a plate-fin heat exchanger group 16 to obtain liquefied natural gas, and heating non-condensable gas by the plate-fin heat exchanger group 16 to send out of the cryogenic separation device 3;
The function is as follows: the second methane low-temperature liquid is separated in a gas-liquid phase of a methane rectifying tower 21, the lower the methane purity of the methane-rich liquid is, the higher the methane purity is, finally, a methane liquid product with the methane content of 92-95% is discharged from the bottom of the methane rectifying tower, and the methane liquid product is sent out of a cryogenic separation device 3 as CNG (compressed natural gas) product for external transportation after heat exchange and temperature rise of the methane liquid product and purified raw gas through a plate-fin heat exchanger group 16; the non-condensable gas at the top of the methane rectifying tower 21 is sent out of the cryogenic separation device 3 after heat exchange and temperature rise are carried out between the non-condensable gas and the purified raw material gas through the plate-fin heat exchanger group 16;
wherein the second methane cryogenic liquid output from the second dehydrogenation separator 19 is transferred to the methane rectification column 21 via a second throttling valve 20.
Specifically, the device also comprises a nitrogen expansion refrigeration device 4, which is used for providing refrigeration capacity for the cryogenic separation device 3 through the cyclic refrigeration of compression, cooling and supercharging expansion of the cyclic nitrogen;
The nitrogen expansion refrigeration device 4 comprises a nitrogen compressor 22 and a second cooler 23 which are sequentially connected with the plate-fin heat exchanger group 16 and used for compressing and cooling normal-temperature low-pressure nitrogen, the output end of the second cooler 23 is connected with the plate-fin heat exchanger group 16, and the compressed and cooled nitrogen is further cooled through the plate-fin heat exchanger group 16;
The nitrogen expansion refrigeration device 4 further comprises a booster expander 24, wherein the input end and the output end of the booster expander 24 are connected with the plate-fin heat exchanger group 16 and are used for further pressurizing and expanding the high-pressure low-temperature nitrogen output by the plate-fin heat exchanger group 16 for refrigeration and outputting the expanded low-temperature nitrogen; part of the expansion low-temperature nitrogen provides cold energy for the methane rectifying tower 21, and the other part of the expansion low-temperature nitrogen is heated by the plate-fin heat exchanger group 16 and then is input into the nitrogen compressor 22 for circulation;
the function is as follows: the circulating refrigeration process of compression, cooling and pressurizing expansion of the circulating nitrogen provides cold for the whole ammonia synthesis raw material gas to remove methane and purifying methane-rich gas to prepare CNG products, simplifies the flow of cryogenic separation of methane from the ammonia synthesis raw material gas, greatly reduces the investment and occupied area of a refrigerant proportioning system required by a mixed refrigerant compressor, reduces the device transformation cost, and is very suitable for the old synthetic ammonia device transformation project.
Specifically, the device also comprises a purified gas compression module 5, which is used for compressing the low-temperature purified gas II purified gas after heating the plate-fin heat exchanger group 16 and outputting the raw gas II after synthesizing and purifying ammonia; the purified gas compression module 5 comprises a purified gas compressor 25 and a third cooler 26 which are sequentially connected, and the low-temperature purified gas II heated by the plate-fin heat exchanger group 16 is compressed and purified by the purified gas compressor 25 and then cooled by the third cooler 26, so as to obtain the raw gas II after ammonia synthesis and purification.
Specifically, the mercury removal device 2 comprises a mercury removal tower 14 and a dust filter 15 which are connected in sequence, and the dehydrated raw material gas output by the dehydration device 1 is subjected to mercury removal by the mercury removal tower 14 and then subjected to dust removal by the dust filter 15 to obtain purified raw material gas; the function is as follows: the mercury removal tower 14 is used for removing trace mercury in the dehydrated feed gas sulfur-impregnated activated carbon to 0.01 mug/Nm 3, the dust filter 15 is used for filtering the dust in the feed gas and purifying the dust to more than 5 mu m to remove 99.9%, so as to ensure the feed gas H 2O≤1ppmv、Hg≤0.01μg/Nm3 entering the next stage of cryogenic separation process, and achieve the purpose of improving the efficiency of the cryogenic separation process;
The dehydration device 1 comprises a first cooler 11, a dehydrator 12 and a drying tower 13 which are connected in sequence, wherein raw material gas is cooled by the first cooler 11 and dehydrated by the dehydrator 12 and the drying tower 13 to obtain dehydrated raw material gas; the function is as follows: saturated water in the raw material gas is cooled and coarsely removed through the first cooler and the dehydrator, so that the adsorption effect of a drying tower of a dehydration device can be greatly improved, the regeneration energy consumption base of the adsorbent of the drying tower is effectively reduced, the service cycle of the adsorbent of the drying tower of the device is prolonged, and the overall operation consumption of the device is reduced.
Specifically, the raw material gas I after ammonia synthesis and purification is mixed with the raw material gas II after ammonia synthesis and purification, and cooled by a first cooler 11 to obtain purified gas; the function is as follows: the raw material gas I after ammonia synthesis and purification and the raw material gas II after ammonia synthesis and purification are mixed and cooled by the first cooler 11 to obtain purified gas, and the purified gas is sent to a downstream ammonia synthesis working section, wherein the methane component in the purified gas is reduced to less than or equal to 1.2 mole percent, and the purification requirement of the raw material gas for ammonia synthesis and the hydrogen recovery requirement are met.
The equipment adopted by each device in the system is the existing equipment.
Examples
The feed gas of an ammonia synthesis section contains 4-10 mol percent of methane and 0.4-0.6 mol percent of argon, and according to the requirement of the subsequent ammonia synthesis reaction, the methane in the feed gas needs to be removed to less than 1.5 mol percent and the argon is removed as far as possible, and the main volume percent of the feed gas of the ammonia synthesis section is as follows:
The normal temperature and high pressure ammonia synthesis raw gas from the upstream working section sequentially enters a first cooler 11, a dehydrator 12 and a drying tower 13 of a dehydration device 1, the raw gas is cooled to 10-20 ℃ and the moisture in the raw gas is removed to 1ppmv, and then the trace mercury in the raw gas is removed to 0.01 mug/Nm 3 through sulfur-impregnated activated carbon in a mercury removal tower 14. The feed gas entering the cryogenic separation plant 3 ensures H 2O≤1ppmv、Hg≤0.01μg/Nm3.
The purified raw gas after dehydration and mercury removal enters a plate-fin heat exchanger group 16, the temperature is reduced to about-160 to-175 ℃, the purified raw gas is sent into a first dehydrogenation separator 17 for gas-liquid two-phase separation, low-temperature purified gas I (-160 to-175 ℃ and 0.83 to 0.98 mole percent of methane) and first methane low-temperature liquid are separated, and the low-temperature purified gas I is sent out of a cryogenic separation device 3 after heat exchange and temperature rise with the purified raw gas through the plate-fin heat exchanger group 16 and then sent to a downstream ammonia synthesis section after heat exchange and temperature rise with a first cooler 11.
The first methane low-temperature liquid is heated to minus 130 ℃ to minus 150 ℃ after part of cold energy is recovered by the plate-fin heat exchanger group 16, is sent into the second dehydrogenation separator 19 for pressure reduction gas-liquid two-phase separation, and separates low-temperature purified gas II (3.0 to 4.0MPa (G), -140 ℃ to minus 150 ℃ and methane mole percent of 1.9 to 2.5%) and second methane low-temperature liquid, wherein the low-temperature purified gas II is sent out of the cryogenic separation device 3 after heat exchange and heating with purified raw material gas by the plate-fin heat exchanger group 16, is compressed by the purified gas compressor 25 and is cooled by the third cooler 26, and is mixed with purified raw material gas I, and the mixed purified gas comprises 0.85 to 1.02 mole percent of methane and 0.33 to 0.35 mole percent of argon.
The second methane low-temperature liquid is throttled and depressurized to 0.8-1.3 MPa (G) further, then enters the methane rectifying tower 21 from the middle part of the methane rectifying tower 21, the operating temperature of the methane rectifying tower 21 is minus 130-minus 170 ℃, the tower top pressure is about 0.75MPa (G), finally, a methane liquid product with 92-95 mol percent of methane content is discharged from the tower bottom of the methane rectifying tower 21, and is subjected to heat exchange with purified raw material gas through a plate-fin heat exchanger group 16, and is sent out of a cryogenic separation device to be used as CNG (compressed natural gas) product for external transportation.
The Aspen software is used for carrying out numerical simulation calculation on thermal data of the device, the hydrogen recovery rate of the purified gas of the synthetic ammonia reaches 99.5-99.7 mol percent, the impurity gas is removed to 0.85-1.02 mol percent of methane and 0.33-0.35 mol percent of argon, the purified gas completely meets the requirement of ammonia synthesis, and the energy consumption of the subsequent synthetic ammonia can be greatly reduced. The molar percentage of methane is 92-95%, the molar percentage of nitrogen is 2-4%, the molar percentage of argon is 3-4%, and the power consumption of the process is about 0.45-0.49 kwh/Nm 3. The low-temperature cold energy of the purified gas is coupled with the raw material gas of the dehydration device by heat exchange, so that liquid drops in the raw material gas are separated in advance, the dehydration load of the dehydration device can be reduced by about 50% -70%, the adsorption effect of a drying tower of the dehydration device can be greatly improved, and the regeneration energy consumption of an adsorbent of the drying tower can be effectively reduced by 200-300 kwh.
The circulating nitrogen pressurizing expansion refrigeration process is adopted, so that the traditional method for separating methane by deep cooling is simplified, the investment and the occupied area of a refrigerant proportioning system required by a mixed refrigerant compressor are greatly reduced, the device transformation cost is reduced, and the method is very suitable for the transformation project of an old synthetic ammonia device.

Claims (3)

1. The pretreatment system for the synthesis ammonia feed gas is characterized by comprising a dehydration device (1), a mercury removal device (2) and a cryogenic separation device (3);
The dehydration device (1) is used for cooling and dehydrating the raw material gas;
The mercury removal device (2) is used for removing mercury from the dehydrated raw gas output by the dehydration device (1) and purifying the dehydrated raw gas;
The cryogenic separation device (3) comprises a plate-fin heat exchanger group (16), wherein the plate-fin heat exchanger group (16) is used for cooling the purified raw material gas output by the mercury removal device (2) and outputting low-temperature purified raw material gas;
The cryogenic separation device (3) further comprises a gas-liquid separation unit, wherein the gas-liquid separation unit is used for separating low-temperature purified raw material gas output by the plate-fin heat exchanger group (16) into gas and liquid to output low-temperature purified gas, and the low-temperature purified gas is heated by the plate-fin heat exchanger group (16) to obtain raw material gas after ammonia synthesis and purification;
The gas-liquid separation unit comprises a first dehydrogenation separator (17), wherein the input end and the output end of the first dehydrogenation separator (17) are connected with the plate-fin heat exchanger group (16), the first dehydrogenation separator (17) is used for separating the gas phase and the liquid phase of low-temperature purified raw gas output by the plate-fin heat exchanger group (16) and outputting low-temperature purified gas I and first methane low-temperature liquid; the low-temperature purified gas I is heated by a plate-fin heat exchanger group (16) to obtain raw material gas I after ammonia synthesis and purification;
The gas-liquid separation unit further comprises a second dehydrogenation separator (19), the input end and the output end of the second dehydrogenation separator (19) are connected with the plate-fin heat exchanger group (16), the first methane low-temperature liquid is subjected to gas-liquid two-phase separation by the second dehydrogenation separator (19) after being heated by the plate-fin heat exchanger group (16), and low-temperature purified gas II and second methane low-temperature liquid are output; heating the low-temperature purified gas II through a plate-fin heat exchanger group (16) to obtain raw gas II after ammonia synthesis and purification;
The gas-liquid separation unit further comprises a methane rectifying tower (21), the input end of the methane rectifying tower (21) is connected with the output end of the second dehydrogenation separator (19), and the output end of the methane rectifying tower (21) is connected with the plate-fin heat exchanger group (16); the methane rectifying tower (21) is used for carrying out gas-liquid two-phase separation on the second methane low-temperature liquid output by the second dehydrogenation separator (19) and outputting liquid methane and non-condensable gas; the liquefied natural gas is obtained after the temperature of the liquid methane is raised by the plate-fin heat exchanger group (16), and the non-condensable gas is sent out of the cryogenic separation device (3) after the temperature of the non-condensable gas is raised by the plate-fin heat exchanger group (16);
The device also comprises a nitrogen expansion refrigeration device (4) which is used for circularly refrigerating the circulated nitrogen through compression, cooling and supercharging expansion to provide cold energy for the cryogenic separation device (3);
The nitrogen expansion refrigeration device (4) comprises a nitrogen compressor (22) and a second cooler (23) which are sequentially connected with the plate-fin heat exchanger group (16) and are used for compressing and cooling normal-temperature low-pressure nitrogen, the output end of the second cooler (23) is connected with the plate-fin heat exchanger group (16), and the compressed and cooled nitrogen is further cooled through the plate-fin heat exchanger group (16);
the nitrogen expansion refrigeration device (4) further comprises a booster expander (24), wherein the input end and the output end of the booster expander (24) are connected with the plate-fin heat exchanger group (16) and are used for further pressurizing and expanding and refrigerating high-pressure low-temperature nitrogen output by the plate-fin heat exchanger group (16) and outputting expanded low-temperature nitrogen;
One part of the expansion low-temperature nitrogen provides cold energy for the methane rectifying tower (21), and the other part of the expansion low-temperature nitrogen is heated by the plate-fin heat exchanger group (16) and then is input into the nitrogen compressor (22) for circulation;
The gas-liquid separation unit also separates low-temperature purified raw material gas output by the plate-fin heat exchanger group (16) into gas and liquid to output liquid methane, and the liquid methane is heated by the plate-fin heat exchanger group (16) to obtain compressed natural gas;
the molar content of methane in the liquid methane is 92-95%.
2. The pretreatment system of synthesis ammonia feed gas according to claim 1, wherein the device further comprises a purified gas compression module (5) for compressing the low-temperature purified gas II purified gas after heating the plate fin heat exchanger group (16) and outputting the purified feed gas II for ammonia synthesis;
The purifying gas compression module (5) comprises a purifying gas compressor (25) and a third cooler (26) which are sequentially connected, and the low-temperature purifying gas II heated by the plate-fin heat exchanger group (16) is compressed and purified by the purifying gas compressor (25) and then cooled by the third cooler (26) to obtain the raw gas II after ammonia synthesis and purification.
3. The pretreatment system for synthesis ammonia feed gas according to claim 2, wherein the mercury removal device (2) comprises a mercury removal tower (14) and a dust filter (15) which are connected in sequence, and the dehydrated feed gas output by the dehydration device (1) is subjected to mercury removal by the mercury removal tower (14) and then subjected to dust removal by the dust filter (15) to obtain purified feed gas;
The dehydration device (1) comprises a first cooler (11), a dehydrator (12) and a drying tower (13) which are sequentially connected, raw material gas is cooled by the first cooler (11), and dehydrated by the dehydrator (12) and the drying tower (13) to obtain dehydrated raw material gas.
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CN104986734A (en) * 2015-06-24 2015-10-21 杭州中泰深冷技术股份有限公司 Synthesis ammonia and synthesis gas self-circulation cryogenic separation purifying device and purifying method thereof
CN204752197U (en) * 2015-06-24 2015-11-11 杭州中泰深冷技术股份有限公司 Synthetic ammonia synthetic gas self -loopa cryogenic separation purifier
DE102017006552A1 (en) * 2017-05-30 2018-12-06 Linde Aktiengesellschaft Process for the recovery of gas products
CN212669206U (en) * 2020-05-29 2021-03-09 西安陕鼓动力股份有限公司 Pretreatment system for synthesis ammonia raw material gas

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