Low-pressure ammonia synthesis process

Abstract

The invention provides a low-pressure ammonia synthesis process which comprises the following steps: 1) performing deep cooling air separation on air so as to obtain nitrogen and oxygen, and performing pure oxygen self-heat conversion on the oxygen with a natural gas so as to obtain a mixed gas with CO and H2; ) performing electrolysis water separation so as to obtain hydrogen; 3) mixing the hydrogen with the nitrogen so as to obtain an ammonia synthesis raw material gas, and performing primary ammonia synthesis in a first ammonia synthesis tower filled with an iron-based catalyst, wherein the synthesis pressure is 5-7MPa; 4) feeding the mixed gas discharged from the first ammonia synthesis tower into a second ammonia synthesis tower filled with a ruthenium-based catalyst, and performing secondary ammonia synthesis, wherein the synthesis pressure is 4-6MPa. By adopting the process, the ammonia synthesis process is divided into two sections which are implemented at specific pressure in the presence of specific types of catalysts and raw material gases of specific hydrogen to nitrogen ratios, ammonia synthesis process requirements are met, stable process operation is ensured, and the net value of ammonia at the outlets of the ammonia synthesis towers and the utilization rates of nitrogen and hydrogen are increased.

Description

technical field

[0001] The invention belongs to the technical field of ammonia synthesis, and in particular relates to a low-pressure ammonia synthesis process. Background technique

[0002] Ammonia is one of the important inorganic chemical products and occupies an important position in the national economy. Except that liquid ammonia can be directly used as fertilizer, nitrogen fertilizers used in agriculture, such as urea, ammonium nitrate, ammonium phosphate, ammonium chloride and various nitrogen-containing compound fertilizers, all use ammonia as raw material. Therefore, synthetic ammonia plays an important role in the national economy. The world's annual synthetic ammonia output has reached more than 100 million tons, of which about 80% of ammonia is used to produce chemical fertilizers, and 20% is used as raw materials for other chemical products.

[0003] As we all know, synthetic ammonia is directly synthesized by nitrogen and hydrogen under high temperature, high...

Examples

Embodiment 1

[0057] The present embodiment provides a kind of low-pressure ammonia synthesis process, comprising the following steps:

[0058] 1) Carry out cryogenic air separation to air, obtain nitrogen and oxygen, described oxygen and natural gas carry out pure oxygen autothermal conversion, obtain containing CO and H 2 The mixed gas; moreover, containing CO and H 2 The mixed gas is passed into the waste heat boiler to recover heat, and high-pressure steam is obtained, which is used to pressurize the raw material gas for the synthesis of ammonia; finally, the mixed gas is separated by electrolysis of water to obtain hydrogen; the hydrogen and nitrogen Mixed to form synthetic ammonia raw material gas, where S2 <10ppm, the molar ratio of hydrogen to nitrogen is 1.7:1;

[0059] 2) the above-mentioned synthetic ammonia raw material gas is 5000h with space velocity -1 The primary ammonia synthesis is carried out in the first ammonia synthesis tower filled with iron-based catalyst, the synt...

Embodiment 2

[0069] The present embodiment provides a kind of low-pressure ammonia synthesis process, comprising the following steps:

[0070] 1) Carry out cryogenic air separation to air, obtain nitrogen and oxygen, described oxygen and natural gas carry out pure oxygen autothermal conversion, obtain containing CO and H 2 The mixed gas; moreover, containing CO and H 2 The mixed gas is passed into the waste heat boiler to recover heat, and high-pressure steam is obtained, which is used to pressurize the raw material gas for the synthesis of ammonia; finally, the mixed gas is separated by electrolysis of water to obtain hydrogen; the hydrogen and nitrogen Mixed to form synthetic ammonia raw material gas, where S2 <10ppm, the molar ratio of hydrogen to nitrogen is 1.5:1;

[0071] 2) The above-mentioned synthetic ammonia raw material gas is 6000h with space velocity -1 The primary ammonia synthesis is carried out in the first ammonia synthesis tower filled with iron-based catalyst, the synt...

Embodiment 3

[0081] The present embodiment provides a kind of low-pressure ammonia synthesis process, comprising the following steps:

[0082] 1) Carry out cryogenic air separation to air, obtain nitrogen and oxygen, described oxygen and natural gas carry out pure oxygen autothermal conversion, obtain containing CO and H 2 The mixed gas; moreover, containing CO and H 2 The mixed gas is passed into the waste heat boiler to recover heat, and high-pressure steam is obtained, which is used to pressurize the raw material gas for the synthesis of ammonia; finally, the mixed gas is separated by electrolysis of water to obtain hydrogen; the hydrogen and nitrogen Mixed to form synthetic ammonia raw material gas, where S2 <10ppm, the molar ratio of hydrogen to nitrogen is 2.5:1;

[0083] 2) the above-mentioned synthetic ammonia raw material gas is 4000h with space velocity -1The primary ammonia synthesis is carried out in the first ammonia synthesis tower filled with iron-based catalyst, the synth...

technical field

[0001] The invention belongs to the technical field of ammonia synthesis, and in particular relates to a low-pressure ammonia synthesis process. Background technique

[0002] Ammonia is one of the important inorganic chemical products and occupies an important position in the national economy. Except that liquid ammonia can be directly used as fertilizer, nitrogen fertilizers used in agriculture, such as urea, ammonium nitrate, ammonium phosphate, ammonium chloride and various nitrogen-containing compound fertilizers, all use ammonia as raw material. Therefore, synthetic ammonia plays an important role in the national economy. The world's annual synthetic ammonia output has reached more than 100 million tons, of which about 80% of ammonia is used to produce chemical fertilizers, and 20% is used as raw materials for other chemical products.

[0003] As we all know, synthetic ammonia is directly synthesized by nitrogen and hydrogen under high temperature, high...

Examples

Embodiment 1

[0057] The present embodiment provides a kind of low-pressure ammonia synthesis process, comprising the following steps:

[0058] 1) Carry out cryogenic air separation to air, obtain nitrogen and oxygen, described oxygen and natural gas carry out pure oxygen autothermal conversion, obtain containing CO and H 2 The mixed gas; moreover, containing CO and H 2 The mixed gas is passed into the waste heat boiler to recover heat, and high-pressure steam is obtained, which is used to pressurize the raw material gas for the synthesis of ammonia; finally, the mixed gas is separated by electrolysis of water to obtain hydrogen; the hydrogen and nitrogen Mixed to form synthetic ammonia raw material gas, where S2 <10ppm, the molar ratio of hydrogen to nitrogen is 1.7:1;

[0059] 2) the above-mentioned synthetic ammonia raw material gas is 5000h with space velocity -1 The primary ammonia synthesis is carried out in the first ammonia synthesis tower filled with iron-based catalyst, the synt...

Embodiment 2

[0069] The present embodiment provides a kind of low-pressure ammonia synthesis process, comprising the following steps:

[0070] 1) Carry out cryogenic air separation to air, obtain nitrogen and oxygen, described oxygen and natural gas carry out pure oxygen autothermal conversion, obtain containing CO and H 2 The mixed gas; moreover, containing CO and H 2 The mixed gas is passed into the waste heat boiler to recover heat, and high-pressure steam is obtained, which is used to pressurize the raw material gas for the synthesis of ammonia; finally, the mixed gas is separated by electrolysis of water to obtain hydrogen; the hydrogen and nitrogen Mixed to form synthetic ammonia raw material gas, where S2 <10ppm, the molar ratio of hydrogen to nitrogen is 1.5:1;

[0071] 2) The above-mentioned synthetic ammonia raw material gas is 6000h with space velocity -1 The primary ammonia synthesis is carried out in the first ammonia synthesis tower filled with iron-based catalyst, the synt...

Embodiment 3

[0081] The present embodiment provides a kind of low-pressure ammonia synthesis process, comprising the following steps:

[0082] 1) Carry out cryogenic air separation to air, obtain nitrogen and oxygen, described oxygen and natural gas carry out pure oxygen autothermal conversion, obtain containing CO and H 2 The mixed gas; moreover, containing CO and H 2 The mixed gas is passed into the waste heat boiler to recover heat, and high-pressure steam is obtained, which is used to pressurize the raw material gas for the synthesis of ammonia; finally, the mixed gas is separated by electrolysis of water to obtain hydrogen; the hydrogen and nitrogen Mixed to form synthetic ammonia raw material gas, where S2 <10ppm, the molar ratio of hydrogen to nitrogen is 2.5:1;

[0083] 2) the above-mentioned synthetic ammonia raw material gas is 4000h with space velocity -1The primary ammonia synthesis is carried out in the first ammonia synthesis tower filled with iron-based catalyst, the synth...

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