CN-122015426-A - Cold energy air separation system based on mixed refrigerant deep cooling

Abstract

The invention relates to a cold energy air separation system based on mixed refrigerant deep cooling, which comprises an air pretreatment unit, a rectification unit and an energy storage unit, wherein the air pretreatment unit comprises an air filter, an air compressor, a first cooler and an air purification system which are sequentially connected in series, the rectification unit comprises a rectification tower, a main cooling box, a first heat exchanger and an argon rectification system, an air outlet of the air purification system is connected with an air inlet of the main cooling box, an air outlet of the main cooling box is connected with an air inlet of a lower tower of the rectification tower, a nitrogen outlet at the lower tower top of the rectification tower is connected with an air inlet of the argon rectification system, the other nitrogen outlet of the rectification tower is connected with an air inlet of the first heat exchanger, a liquid nitrogen inlet of the first heat exchanger is connected with a liquid nitrogen outlet of the LNG cooling box, the mixed refrigerant deep cooling unit comprises a mixed refrigerant compressor, a mixed refrigerant cooler and a mixed refrigerant heat exchanger which are sequentially connected in series, and the energy storage unit comprises a liquid air storage tank which is connected with the air filter and is used for providing air for the air filter.

Inventors

• FAN JIAKUN
• LI YUJING
• YUAN SIQI
• YANG FAN
• XU JIAWEI
• WU JIANHONG
• YAN XU
• YANG LIANG
• CHEN JU
• QIU ZAOYANG
• GAI XIAOGANG

Assignees

• 中海石油气电集团有限责任公司

Dates

Publication Date

20260512

Application Date

20260205

Claims (10)

1. 1. A cold energy air separation system based on mixed refrigerant cryogenic cooling, comprising: The air pretreatment unit comprises an air filter (1), an air compressor (2), a first cooler (3) and an air purification system which are sequentially connected in series; The rectification unit comprises a rectification column (31), a main cooling box (32), a first heat exchanger (35) and an argon rectification system (41), wherein an air outlet of the air purification system is connected with an air inlet of the main cooling box (32), an air outlet of the main cooling box (32) is connected with a lower column air inlet of the rectification column (31), a lower column top nitrogen outlet of the rectification column (31) is connected with an air inlet of the argon rectification system (41), the other nitrogen outlet of the rectification column (31) is connected with an air inlet of the first heat exchanger (35), a liquid nitrogen inlet of the first heat exchanger (35) is connected with a liquid nitrogen outlet of the LNG cooling box (13), and nitrogen exchanges heat with liquid nitrogen from the LNG cooling box (13) in the first heat exchanger (35) and returns to the lower column top of the rectification column (31) after being liquefied, so that cold quantity transmission is completed; the mixed refrigerant cryogenic unit comprises a mixed refrigerant compressor, a mixed refrigerant cooler (23) and a mixed refrigerant heat exchanger which are sequentially connected in series, wherein the mixed refrigerant heat exchanger is connected with an LNG cold box (13) and is used for providing cold energy for LNG; An energy storage unit comprising a liquid air reservoir connected to the air filter (1) for providing air to the air filter (1).
2. 2. Cold energy air separation system based on mixed refrigerant cryogenic according to claim 1, characterized in that the air purification system comprises two adsorbers (4) arranged in parallel.
3. 3. Cold energy air separation system based on mixed refrigerant cryogenic cooling according to claim 2, characterized in that the adsorber (4) is of double-deck structure, the bottom is activated alumina, the upper is molecular sieve, when one is running, the other is regenerated, and the regeneration air source is delivering dirty nitrogen to the main cooling tank (32).
4. 4. Cold energy air separation system based on mixed refrigerant deep cooling according to claim 1, characterized in that the rectification system further comprises a second heat exchanger (38), the second heat exchanger (38) is respectively connected with the rectification column (31) and the argon rectification system (41), and part of nitrogen generated by the rectification column (31) is supercooled and throttled by the second heat exchanger (38) and then sent to the upper column top of the rectification column (31) to be used as upper column reflux liquid to participate in upper column rectification of the rectification column (31).
5. 5. The cryogenic air separation system based on mixed refrigerant according to claim 4, wherein the second heat exchanger (38) is further connected with the main cooling tank (32), the main cooling tank (32) is connected with the first nitrogen booster (11), low-pressure pure nitrogen is obtained from the top of the upper column of the rectifying column (31), and the low-temperature low-pressure nitrogen is fed into the first nitrogen booster (11) as raw material nitrogen of liquid nitrogen products after being reheated to a certain temperature by the second heat exchanger (38) and the main cooling tank (32), and is partially discharged.
6. 6. The cold energy air separation system based on mixed refrigerant deep cooling according to claim 5, wherein the rectifying unit further comprises a second liquid separation tank (33) and a liquid nitrogen storage tank (36), two ends of the second liquid separation tank (33) are respectively connected with the LNG cold tank (13) and the first heat exchanger (35), dirty nitrogen is obtained at an upper tower of the rectifying tower (31), the dirty nitrogen is sent out after being reheated by the second heat exchanger (38) and the main cold tank (32), a part of the dirty nitrogen is used as regeneration gas of the air purification system, the rest of the air is emptied, and liquid nitrogen from the LNG cold tank (13) enters the second liquid separation tank (33) to be subjected to gas-liquid separation, and is sent into the liquid nitrogen storage tank (36) as product liquid nitrogen.
7. 7. The cryogenic air separation system based on mixed refrigerant according to claim 5, wherein the rectifying unit further comprises a first subcooler (14), and two ends of the first subcooler (14) are respectively connected with the LNG cold box (13) and the second liquid separation tank (33).
8. 8. Cold energy air separation system based on mixed refrigerant sub-cooling according to claim 1, characterized in that the mixed refrigerant compressor comprises a first stage mixed refrigerant compressor (21) and a second stage mixed refrigerant compressor (22) connected in series.
9. 9. Cold energy air separation system based on mixed refrigerant sub-cooling according to claim 1, characterized in that the mixed refrigerant heat exchanger comprises a first mixed refrigerant heat exchanger (24) and a second mixed refrigerant heat exchanger (25).
10. 10. Cold energy air separation system based on mixed refrigerant cryogenic cooling according to claim 1, characterized in that the energy storage unit further comprises a first liquid separation tank, a liquid air pump and an air expander, the liquid air storage tank, the liquid air pump, the air expander and the first liquid separation tank being connected in series in sequence, the first liquid separation tank being connected with the air filter (1).

Description

Cold energy air separation system based on mixed refrigerant deep cooling Technical Field The invention relates to a cryogenic cold energy air separation system based on mixed refrigerant, and belongs to the technical field of liquid energy storage. Background The air separation using LNG cold energy is a novel air separation process technology, and the difference between the process and the conventional air separation process is that the LNG cold energy is used for replacing mechanical refrigeration in the conventional air separation at the cost of consuming a large amount of electric energy, so that the energy consumption of a system is greatly reduced. The main cost of the air separation device depends on the energy consumption level, the energy consumption level of the LNG cold energy air separation process is relatively low, and the power consumption of the air separation process can be sufficiently reduced by utilizing the LNG cold energy to cool and liquefy the air. However, in actual operation, as the expansion storage tank of the LNG receiving station increases the boil-off amount, the LNG export temperature may increase, and the cold energy space division may decrease, and a method for maintaining the normal output of the cold energy space division even under the condition of increasing the LNG temperature is needed. Disclosure of Invention According to the technical problem, the invention provides a cryogenic cold energy air separation system based on mixed refrigerant, which adopts a mixed refrigerant refrigeration technology, and adopts a mixed refrigerant compression throttling mode to perform refrigeration when LNG cold energy is insufficient, so that the prepared cold energy can reduce the temperature of LNG, and the cold energy air separation can also operate under the condition that the temperature of the LNG is not increased. In order to achieve the above purpose, the present invention adopts the following technical scheme: A cold energy air separation system based on mixed refrigerant cryogenic cooling, comprising: The air pretreatment unit comprises an air filter, an air compressor, a first cooler and an air purification system which are sequentially connected in series; The rectification unit comprises a rectification tower, a main cooling box, a first heat exchanger and an argon rectification system, wherein an air outlet of the air purification system is connected with an air inlet of the main cooling box, an air outlet of the main cooling box is connected with a lower tower air inlet of the rectification tower, a nitrogen outlet at the top of the lower tower of the rectification tower is connected with an air inlet of the argon rectification system, another nitrogen outlet of the rectification tower is connected with an air inlet of the first heat exchanger, a liquid nitrogen inlet of the first heat exchanger is connected with a liquid nitrogen outlet of the LNG cooling box, and nitrogen exchanges heat with liquid nitrogen from the LNG cooling box in the first heat exchanger and returns to the top of the lower tower of the rectification tower after being liquefied, so that cold energy transmission is completed; The mixed refrigerant cryogenic unit comprises a mixed refrigerant compressor, a mixed refrigerant cooler and a mixed refrigerant heat exchanger which are sequentially connected in series, wherein the mixed refrigerant heat exchanger is connected with the LNG cold box and is used for providing cold energy for LNG; and the energy storage unit comprises a liquid air storage tank connected with the air filter and is used for providing air for the air filter. The cold energy air separation system based on mixed refrigerant cryogenic cooling preferably comprises two adsorbers arranged in parallel. In the cold energy air separation system based on mixed refrigerant cryogenic cooling, preferably, the adsorber is of a double-layer bed structure, the bottom is active alumina, the upper part is a molecular sieve, when one operates, the other regenerates, and a regeneration air source is used for conveying polluted nitrogen for the main cooling box. The cold energy air separation system based on mixed refrigerant deep cooling preferably further comprises a second heat exchanger, the second heat exchanger is respectively connected with the rectifying tower and the argon rectifying system, and part of nitrogen generated by the rectifying tower is sent to the upper tower top of the rectifying tower as upper tower reflux liquid after being supercooled and throttled by the second heat exchanger to participate in upper tower rectification of the rectifying tower. And preferably, the second heat exchanger is also connected with the main cooling tank, the main cooling tank is connected with the first nitrogen booster, low-pressure pure nitrogen is obtained from the top of the upper tower of the rectifying tower, and the low-temperature low-pressure nitrogen is fed into the first nitrogen booste