CN-122015425-A - Cold energy air separation system based on liquid air energy storage

CN122015425ACN 122015425 ACN122015425 ACN 122015425ACN-122015425-A

Abstract

The invention relates to a cold energy air separation system based on liquid air energy storage, 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, 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, the cold energy supply unit is used for providing cold energy for the system, and the energy storage unit comprises a liquid air storage tank connected with the air compressor. The system adopts a compression expansion throttling mode to refrigerate when no additional cold energy is supplied.

Inventors

FAN JIAKUN
YAO QIANLIN
LIU PEIYUAN
YANG FAN
XU JIAWEI
WU JIANHONG
CHEN JU
QIU ZAOYANG
YAN XU
YANG LIANG
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. A cold energy air separation system based on liquid air energy storage, 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 tower (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 tower air inlet of the rectification tower (31), a nitrogen outlet at the top of the lower tower of the rectification tower (31) is connected with an air inlet of the argon rectification system (41), the other nitrogen outlet of the rectification tower (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 top of the lower tower of the rectification tower (31) after being liquefied, so that cold energy transmission is completed; The system comprises a cold energy supply unit, a first liquid nitrogen pump (57), a second liquid nitrogen pump (33) and a liquid nitrogen storage tank (36), wherein when LNG provides cold energy, liquid nitrogen from an LNG cold tank (13) is compressed and further cooled and throttled in a first subcooler (14) to form pressure liquid nitrogen, a part of the pressure liquid nitrogen is returned to the first subcooler (14) and the LNG cold tank (13) to serve as a cold source, the rest of the pressure liquid nitrogen enters a main cold tank (32) to throttle and then enters a first heat exchanger (35) to exchange heat with the pressure nitrogen pumped out by a lower tower of a rectifying tower (31), is gasified and then enters the main cold tank (32) to be reheated and then returns to the first nitrogen booster (11), the first nitrogen booster (11) is connected with the LNG cold tank (13), when LNG does not provide cold energy, the cold energy required by the system is transferred to nitrogen from liquid air, and the nitrogen in the main cold tank (32) is subjected to heat exchange and condensation with liquid air to form liquid nitrogen into liquid nitrogen through the second liquid nitrogen heat exchanger (55), and then enters the second liquid nitrogen tank (33) after providing circulating pressure through the liquid nitrogen pump (57), and finally enters the liquid nitrogen storage tank (36); the energy storage unit comprises a liquid air storage tank (51) connected with the air compressor (2) and is used for providing liquid air for the air compressor (2).
2. Cold energy air separation system based on liquid air energy storage according to claim 1, characterized in that the air purification system comprises two adsorbers (4) arranged in parallel.
3. The cold energy air separation system based on liquid air energy storage according to claim 2, wherein the adsorber (4) is of a double-layer bed structure, the bottom is activated alumina, the upper is a molecular sieve, when one is running, the other is regenerated, and the regenerated air source is a main cold box (32) for conveying polluted nitrogen.
4. The cold energy air separation system based on liquid air energy storage according to claim 1, wherein the rectification unit further comprises a second heat exchanger (38), the second heat exchanger (38) is respectively connected with the rectification tower (31) and the argon rectification system (41), and part of nitrogen generated by the rectification tower (31) is supercooled and throttled by the second heat exchanger (38) and then is sent to the upper tower top of the rectification tower (31) to serve as upper tower reflux liquid to participate in upper tower rectification of the rectification tower (31).
5. The cold energy air separation system based on liquid air energy storage 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), the low-pressure pure nitrogen is sent 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), partial low-temperature low-pressure nitrogen pumped in the rectifying column (31) is pressurized by the third nitrogen booster (53), and the liquefied air of the cold energy supply unit is sent into the liquid nitrogen storage tank (36) as product liquid nitrogen after being liquefied in the first liquid nitrogen heat exchanger (54), liquid oxygen is pumped out of the middle layer bottom of the rectifying column (31), and the liquid oxygen is sent out of the main cooling tank (32) as product liquid oxygen after being supercooled by the second heat exchanger (38).
6. Cold energy air separation system based on liquid air energy storage according to claim 1, characterized in that the energy storage unit comprises an air compression cooling assembly, a molecular sieve (23), an air cooling box (26) and a liquid air storage tank (51) connected in series in sequence, the liquid air storage tank (51) being connected with the air compressor (2).
7. The cold energy air separation system based on liquid air storage according to claim 6, wherein the air compression cooling assembly comprises a first air compressor (21), a first air cooler (22), a second air compressor (24) and a second air cooler (25) connected in series.
8. The cold energy air separation system based on liquid air energy storage according to claim 7, wherein the liquid air is stored at night, air enters the molecular sieve (23) from the first air compressor (21) after being cooled by the first air cooler (22), air enters the second air compressor (24) after being dehydrated and decarbonized in the molecular sieve (23), then enters the air cooling box (26) after being cooled by the second air cooler (25), one air stream entering the air cooling box (26) is pumped through the air expansion machine (27) to provide cold energy, one air stream is directly cooled into liquid and then is depressurized by the liquid air throttle valve (28) to be further cooled into the air separation tank to carry out gas-liquid separation, the separated gas is returned to the air cooling box (26) to provide cold energy for the air separation tank and then enters the second air compressor (25), and the separated liquid enters the liquid air storage tank (51) to store.
9. The cold energy air separation system based on liquid air energy storage according to claim 8, wherein the liquid air releases energy in daytime, when LNG is supplied with cold energy, the liquid air in the energy release stage is pumped into the first liquid air-nitrogen heat exchanger (54) from the liquid air storage tank (51) to exchange heat with high-purity nitrogen discharged from the top of the rectifying tower (31), the released cold energy of the liquid air after heat exchange becomes an air return air compressor (2), and the high-purity nitrogen after heat exchange absorbs cold energy and enters the liquid nitrogen storage tank (36); And when no LNG provides cold energy, the liquid air is pumped into a second liquid-air nitrogen heat exchanger (55) from a liquid air storage tank (51) to exchange heat with nitrogen in the energy release stage, the liquid air releases cold energy to become air, and the air is further cooled in an ethylene glycol cooler (56) to release cold energy to ethylene glycol and then returns to an air compressor (2), and the nitrogen is condensed into liquid nitrogen and then enters a liquid nitrogen storage tank (36).
10. The cold energy air separation system based on liquid air energy storage according to claim 1, wherein an argon fraction gas is led out from the lower part of the upper tower of the rectifying tower (31) and is sent into an argon rectifying system (41) for rectification, so that the oxygen content is reduced, the oxygen-enriched liquid air led out after supercooling is throttled and is sent into the rectifying tower as a first cold source, liquid nitrogen led out from the middle part of the rectifying tower (31) is supercooled through a second heat exchanger (38) as a second cold source, pressure nitrogen led out from the lower tower top of the rectifying tower (31) is used as a heat source to evaporate liquid argon, meanwhile, the nitrogen is liquefied, 99.999% of refined liquid argon is obtained through full rectification argon, and finally the argon rectifying system (41) is led out into a liquid argon storage tank (42) as product liquid argon.

Description

Cold energy air separation system based on liquid air energy storage Technical Field The invention relates to a cold energy air separation system based on liquid air energy storage, and belongs to the technical field of liquid air 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, due to the problem of unstable output of the LNG receiving station, intermittent production stoppage of the cold energy space division may occur, and during the production stoppage period, not only the sales amount may be reduced, but also long-term users may be lost, and there is a need for a method for enabling the cold energy space division to operate normally without LNG. Disclosure of Invention According to the technical problem, the invention provides the cold energy air separation system based on liquid air energy storage, which adopts the liquid air energy storage technology, and adopts a compression expansion throttling mode to refrigerate when no additional cold energy is supplied, so that the prepared cold energy is transferred to the air separation instead of LNG to circulate to supply cold for the air separation, and the cold energy air separation can also operate under the condition of no LNG external delivery. Meanwhile, the liquid air stores energy to liquefy and store cold energy in the night electric low-valley period, and the cold energy is transferred to the air separation process as high-purity nitrogen for discharging air in the whole day, so that the yield of the air separation liquid nitrogen product every day is improved. In order to achieve the above purpose, the present invention adopts the following technical scheme: a cold energy air separation system based on liquid air energy storage, 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 lower tower top 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 lower tower top of the rectification tower after being liquefied, so that cold energy transmission is completed; The system comprises a cold energy supply unit, a first nitrogen booster and a liquid nitrogen pump, wherein when LNG provides cold energy, liquid nitrogen from an LNG cold box is compressed and further cooled and throttled in a first subcooler to form pressure liquid nitrogen, a part of the pressure liquid nitrogen is returned to the first subcooler and the LNG cold box to serve as a cold source, the rest of the pressure liquid nitrogen enters the first heat exchanger to exchange heat with the pressure nitrogen pumped out by a lower tower of a rectifying tower after entering the main cold box to be gasified, then enters the main cold box to be reheated and returns to the first nitrogen booster, and the first nitrogen booster is connected with the LNG cold box; And the energy storage unit comprises a liquid air storage tank connected with the air compressor and is used for providing liquid air for the air compressor. Preferably, the air purification system comprises two adsorbers arranged in parallel. In the cold energy air separation system based on liquid air energy storage, preferably, the absorber is of a double-layer bed structure, the bottom is of activated alumina, the upper part is of a molecular sieve, when one of the two systems operates, the other system regenerates, and a regenerated air source is used for conveying polluted nitrogen for the main cold box. The cold energy air separation sys