SYSTEM AND METHOD FOR SYNTHESIS OF CRYOGENICALLY BOUND AMMONIA WITH WASHING WITH LIQUID NITROGEN

Claims

1. A system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing, the system comprising: a liquid nitrogen flushing module, an ammonia synthesis module, a first pipeline and a second pipeline; the liquid nitrogen flushing module comprises a cold container, and the ammonia synthesis module comprises an apparatus for synthesizing ammonia and an ammonia separator; The first pipeline connects the ammonia synthesis apparatus to the cold container and serves to introduce the process gas obtained in the ammonia synthesis apparatus into the cold container for cooling; the second pipeline connects the cold container and the ammonia separator and serves to introduce the process gas cooled in the cold container into the ammonia separator for separation.

2. A system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing according to claim 1, characterized in that the cold container is a cold container into which gaseous nitrogen feedstock is supplied from the air separation section.

3. A system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing according to any one of claims 1 and 2, characterized in that the liquid nitrogen flushing module contains at least two cold containers and one nitrogen flushing tower, wherein the at least two cold containers are connected in series as a first cold container and a last cold container, wherein the first cold container is connected between the ammonia synthesis apparatus and the ammonia separator via a first pipeline and a second pipeline, wherein the first cold container is a cold container into which gaseous nitrogen feedstock is supplied from the air separation section, and the last cold container is connected to the nitrogen flushing tower.

4. A system for the synthesis of cryogenically bound ammonia with liquid nitrogen flushing according to any one of claims 1 to 3, characterized in that the liquid nitrogen flushing module comprises three cold containers and one nitrogen flushing tower, wherein the three cold containers are connected in series as a first cold container, a second cold container and a third cold container, each of the cold containers is provided with an inlet for purified gas, an outlet for purified gas, an inlet for fuel gas and an outlet for fuel gas, wherein the first cold container is further provided with an inlet for gaseous nitrogen feedstock, an outlet for gaseous nitrogen feedstock, an inlet for process gas and an outlet for process gas, and both the second cold container and the third cold container are provided with an inlet for gaseous hydrogen feedstock, an outlet for gaseous hydrogen feedstock, an inlet for gaseous nitrogen feedstock and an outlet for gaseous nitrogen feedstock;the second ammonia cooler is connected downstream of the ammonia synthesis apparatus, wherein one end of the first pipeline is connected to the process gas outlet of the second ammonia cooler, and the other end of the first pipeline is connected to the process gas inlet of the first cold container, one end of the second pipeline is connected to the process gas outlet of the first cold container, and the other end of the second pipeline is connected to the process gas inlet of the ammonia separator; the third cold container is additionally connected to a nitrogen flushing tower.

5. A system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing according to any one of paragraphs 1-4, characterized in that the system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing satisfies one or more of the following conditions: 1) cold containers are plate-fin heat exchangers; and 2) the cryogenically bound ammonia synthesis system with liquid nitrogen flushing further comprises an insulating container, wherein the liquid nitrogen flushing module is completely located inside the insulating container, the insulating container is provided with a cold gas inlet, and the cooling energy is supplied through the cold gas inlet to the insulating chamber to reduce cold losses in the liquid nitrogen flushing module.

6. A system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing according to any one of paragraphs 1-5, characterized in that the system for synthesizing cryogenically bound ammonia with liquid nitrogen flushing satisfies one or more of the following conditions: 1) the ammonia synthesis module further comprises a compression apparatus, a circulation apparatus, a first ammonia cooler, a second ammonia cooler and a circulation circuit; the compression apparatus and the circulation apparatus are connected in series upstream of the ammonia synthesis apparatus; the circulation circuit connects the ammonia separator to the circulation apparatus, and the circulation circuit is used to return circulating gas from the ammonia separator to the circulation apparatus; the first ammonia cooler is located in the ammonia synthesis apparatus, the second ammonia cooler is connected downstream of the ammonia synthesis apparatus, one end of the first pipeline is connected to the second ammonia cooler, and the other end of the first pipeline is connected to a cold container; in addition, the ammonia synthesis module further comprises a cold gas heat exchanger and a water cooler, between the first ammonia cooler and the water cooler a process gas pipeline is located, and both the circulation loop and the process gas pipeline pass through the cold gas heat exchanger, which ensures heat exchange between the circulation gas in the circulation loop and the process gas in the process gas pipeline; and 2) the cryogenically bound ammonia synthesis system with liquid nitrogen flushing further includes a nitrogen mixing module, the nitrogen mixing module is connected between the liquid nitrogen flushing module and the ammonia synthesis module, and the nitrogen mixing module is used to supply reaction gas to the ammonia synthesis module; In addition, the nitrogen inlet of the nitrogen mixing module is used to receive nitrogen from the air separation section.

7. A method for synthesizing cryogenically bound ammonia with washing with liquid nitrogen, the method comprising the following steps: introducing a reaction gas into an ammonia synthesis apparatus for synthesizing ammonia, thereby obtaining a process gas; introducing the process gas into the cold container of the washing section with liquid nitrogen to cool the process gas, wherein the process gas is subjected to heat exchange to a temperature in the range of from -77.7°C to the ambient temperature, and, in addition, the process gas is subjected to heat exchange to a temperature in the range of from -70°C to -10°C; and the cooled process gas is fed into the ammonia separator for separation, the liquid ammonia is collected, and the separated gas is returned as cycle gas to the ammonia synthesis apparatus.

8. A method for synthesizing cryogenically bound ammonia with washing with liquid nitrogen according to paragraph 7, characterized in that the process gas is subjected to heat exchange to a temperature in the range from -20°C to -10°C.

9. A method for synthesizing cryogenically bound ammonia with washing with liquid nitrogen according to any one of paragraphs. 7, 8, characterized in that in the liquid nitrogen washing section, purified gas and / or fuel gas passing through a cold container is used to cool the process gas, and the temperature of the purified gas and / or fuel gas, which exchanges heat with the process gas, is in the range from -65°C to -50°C.

10. A method for synthesizing cryogenically bound ammonia with washing with liquid nitrogen according to any of paragraphs 7-9, characterized in that the ammonia synthesis is performed using a system for synthesizing cryogenically bound ammonia with washing with liquid nitrogen according to any of paragraphs 1-6; In addition, the method for cryogenic synthesis of ammonia with washing with liquid nitrogen preferably includes the following steps: introducing the reaction gas into the ammonia synthesis apparatus to synthesize ammonia, thereby obtaining process gas; introducing process gas into the cold container through a first pipeline to cool the process gas; and the cooled process gas is fed into the ammonia separator through a second pipeline for separation and the separated gas is returned to the ammonia synthesis apparatus; and furthermore, when the cryogenically bound ammonia synthesis system with liquid nitrogen flushing is additionally equipped with a liquid nitrogen flushing module according to paragraph 4, the method for producing the reaction gas includes the following steps: sequentially feeding the gaseous nitrogen feedstock from the air separation section into the first cold container for heat exchange and then feeding it into the second cold container, feeding the gaseous hydrogen feedstock from the low methanization section into the second cold container, then sequentially passing the gaseous nitrogen feedstock and the gaseous hydrogen feedstock through the third cold container and the nitrogen washing tower for cooling and separating to obtain a low-temperature purified gas and a fuel gas, sequentially passing the purified gas and the fuel gas through the third cold container, the second cold container and the first cold container for stepwise heat exchange and increasing the temperature, feeding the purified gas into a nitrogen mixing apparatus for mixing with nitrogen from the air separation section and adjusting the ratio of hydrogen and nitrogen to 3:1 to form a reaction gas; and furthermore, when the cryogenically bound ammonia synthesis system with liquid nitrogen flushing is further equipped with a cold gas heat exchanger according to paragraph 6, the temperature of the process gas is reduced by means of the cold gas heat exchanger to 40°C - -5°C, preferably reduced to 30°C; when the cryogenically bound ammonia synthesis system with liquid nitrogen flushing is further equipped with a first ammonia cooler according to claim 6, the temperature of the process gas is reduced by the first ammonia cooler to 30°C-8°C, preferably reduced to 15°C; and when the cryogenically bound ammonia synthesis system with liquid nitrogen flushing is additionally equipped with a second ammonia cooler according to item 6, the temperature of the process gas is reduced by means of the second ammonia cooler to 15°C - -12°C, preferably reduced to -5°C.