Device for producing liquid from flue gas with low energy consumption and method for using same

1 . A device for producing liquid from flue gas with low energy consumption, comprising a CO 2 and N 2 low-temperature medium-pressure adsorption system, an energy utilization system, a low-temperature filtration gas low-temperature compression system, a CO 2 low-temperature purification system ( 101 ), and a nitrogen liquid device system ( 100 ); the systems are interconnected through pipelines and valves, wherein the CO 2 and N 2 low-temperature medium-pressure adsorption system comprises a flue gas cooler ( 1 A), a first gas-liquid separator ( 1 B), a compression system ( 1 C), a drying system ( 1 D), a gas expander system, and a low-temperature medium-pressure adsorption device ( 1 H), which is used to cool, pressurize, dewater, and perform low-temperature adsorption separation of CO 2 and N 2 from the flue gas; the energy utilization system comprises an electric heater ( 2 E), a CO 2 compressor ( 2 A), a heat utilizer ( 2 B), and a second cooler ( 2 C), which is used to pressurize, recover heat and cool desorbed gas obtained from the CO 2 and N 2 low-temperature medium-pressure adsorption system; the low-temperature filtration gas low-temperature compression system comprises a low-temperature compressor ( 3 A), which is used for low-temperature pressurization of the low-temperature medium-pressure filtered gas obtained from the CO 2 and N 2 low-temperature medium-pressure adsorption system, the CO 2 low-temperature purification system ( 101 ) is used to further purify and liquefy the low-temperature medium-pressure gas obtained from the energy utilization system, to obtain a liquid CO 2 product; and the nitrogen liquid device system ( 100 ) is used to distill and liquefy medium-pressure gas discharged from the low-temperature compression system, to obtain a liquid nitrogen product;

one end of a flue gas cooler ( 1 A) in the CO 2 and N 2 low-temperature medium-pressure adsorption system is connected to a flue gas discharge port, while the other end is connected to a first gas-liquid separator ( 1 B), in the first gas-liquid separator ( 1 B), the liquid is discharged through a water outlet ( 13 ) of the first gas-liquid separator, and the gas enters the compression system ( 1 C) through a gas outlet ( 12 ) of the first gas-liquid separator for compression, cooling, and dewatering, the compressed, cooled, and dewatered flue gas enters the drying system ( 1 D) through a first pipeline ( 14 ) to dehydrate and dry thoroughly, so that the flue gas emitted from the drying system ( 1 D) has a water content of ppm level, the drying system ( 1 D) is connected to a gas expander system, wherein the gas expander system consists of a first expander boosting end ( 1 E), a first cooler ( 1 F), and a gas expansion end ( 1 G), the flue gas with ppm-level water content sequentially enters the first expander boosting end ( 1 E), the first cooler ( 1 F), and the gas expansion end ( 1 G) through the second pipeline ( 15 ), the gas expansion end ( 1 G) then enters the low-temperature medium-pressure adsorption device ( 1 H) through a rear third pipeline ( 18 ), where the CO 2 in the low-temperature medium-pressure flue gas is adsorbed and captured using the low-temperature medium-pressure adsorption principle, a crude CO 2 gas with a carbon purity of 85-90% is obtained at a desorption gas outlet ( 19 ) of the low-temperature medium-pressure adsorption device, and a medium-pressure crude nitrogen gas with a CO 2 concentration of less than 1 ppm is obtained at the low-temperature medium-pressure filtered gas outlet ( 20 ) of the low-temperature medium-pressure adsorption device; the nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%, thus achieving the purpose of carbon nitrogen separation, the low-temperature medium-pressure filtered gas outlet ( 20 ) is also connected to the low-temperature medium-pressure adsorption device ( 1 H) through a fourth pipeline ( 32 ), so that a portion of the low-temperature filtered gas enters the low-temperature medium-pressure adsorption device ( 1 H) through the fourth pipeline ( 32 ) as cold-blowing regeneration gas, to cold-blow the adsorbent in the low-temperature medium-pressure adsorption device ( 1 H);

the desorption gas outlet ( 19 ) of the low-temperature medium-pressure adsorption device is connected to the CO 2 compressor ( 2 A) in the energy utilization system, to compress and boost the crude CO 2 gas; the CO 2 compressor ( 2 A) is sequentially connected to the heat utilizer ( 2 B), the second cooler ( 2 C), and the CO 2 low-temperature purification system ( 101 ), the second cooler ( 2 C) further cools the cooled and pressurized crude CO 2 gas, such that the pressurized crude CO 2 gas exiting from the second cooler ( 2 C) meets the temperature and pressure requirements of the CO 2 low-temperature purification system ( 101 ), the CO 2 low-temperature purification system ( 101 ) is used to purify and refine the pressurized low-temperature CO 2 , yielding industrial-grade or food-grade CO 2 , the CO 2 low-temperature purification system ( 101 ) is connected to the heat utilizer ( 2 B) through a ninth pipeline ( 24 ), and the heat utilizer ( 2 B) is connected to the fourth pipeline ( 32 ) of the low-temperature medium-pressure adsorption device ( 1 H), to heat the low-temperature regeneration gas exiting from the CO 2 low-temperature purification system ( 101 ), which then enters the low-temperature medium-pressure adsorption device ( 1 H) as heated regeneration gas;

the low-temperature medium-pressure filtered gas outlet ( 20 ) of the low-temperature medium-pressure adsorption device is sequentially connected to the low-temperature compressor ( 3 A) and the nitrogen liquid device system ( 100 ) in the low-temperature filtered gas compression system at the rear, to pressurize all or most of the low-temperature filtered gas, which then enters the nitrogen liquid device system ( 100 ), the nitrogen liquid device system ( 100 ) is used to further refine and liquefy the pressurized low-temperature filtered gas to obtain the liquid nitrogen product, a tenth pipeline ( 26 ) is arranged at the rear of the nitrogen liquid device system ( 100 ), the tenth pipeline ( 26 ) is branched into two routes at the rear, one route is sequentially connected to the heat utilizer ( 2 B) and the electric heater ( 2 E), the electric heater ( 2 E) is connected to a sixth pipeline ( 102 ), and the sixth pipeline ( 102 ) is connected to the drying system ( 1 D), to heat the waste gas regeneration gas from the nitrogen liquid device system ( 100 ) to a required temperature before entering the drying system ( 1 D) as the regeneration gas for heating, the other route of the tenth pipeline ( 26 ) is directly connected to the sixth pipeline ( 102 ), to feed the waste gas regeneration gas from the nitrogen liquid device system ( 100 ) to directly enter the drying system ( 1 D) as cold blow gas for cold blowing;

the CO 2 low-temperature purification system ( 101 ) comprises a third condenser ( 4 F), an evaporator ( 4 D), a liquefier ( 4 E), and a third distillation column ( 4 G), wherein the third condenser ( 4 F) is mounted above the third distillation column ( 4 G), and the evaporator ( 4 D) is mounted below the third distillation column ( 4 G), the liquefier ( 4 E) is arranged separately outside the column; the second cooler ( 2 C) is connected to the evaporator ( 4 D), and the evaporator ( 4 D) is connected to the liquefier ( 4 E), the liquefier ( 4 E) is connected to the third distillation column ( 4 G) through an eighth pipeline ( 46 ); the third distillation column ( 4 G) is connected to the third condenser ( 4 F), and the third condenser ( 4 F) is connected to the third distillation column ( 4 G) through a seventh pipeline ( 110 ) to form a closed loop, a condensation liquid inlet channel ( 48 ) and a condensation gas outlet channel( 49 ) are formed in the third condenser ( 4 F), a ninth pipeline ( 24 ) is provided below the third distillation column ( 4 G) and is connected to the heat utilizer ( 2 B), a fifth pipeline ( 47 ) is provided at the bottom of the third distillation column ( 4 G) for obtaining the liquid CO 2 product;

the nitrogen liquid device system ( 100 ) comprises a circulating compression system, a high and low-temperature gas expander, a heat exchanger ( 5 A), a second gas-liquid separator ( 5 H), a distillation column system, and a subcooler, the circulating compression system consists of a first compressor ( 5 K 1 ) and a second compressor ( 5 K 2 ), the high and low-temperature gas expander is equipped with a second expander boosting end ( 5 P), a first expansion end ( 5 T), and a second expansion end ( 5 U), the subcooler consists of a first subcooler ( 5 D), a second subcooler ( 5 F), and a third subcooler ( 5 J), the distillation column system consists of a first distillation column ( 5 B) and a second distillation column ( 5 E), wherein a first condenser ( 5 C) is mounted above the first distillation column ( 5 B), and a second condenser ( 5 G) is mounted above the second distillation column ( 5 E), the low-temperature compressor ( 3 A) is sequentially connected to the heat exchanger ( 5 A) and the first distillation column ( 5 B), the first distillation column ( 5 B) is provided with two branch pipelines, wherein the first branch of the first distillation column ( 5 B) is sequentially connected to the first subcooler ( 5 D), the first condenser ( 5 C), the second distillation column ( 5 E), the second subcooler ( 5 F), and the second condenser ( 5 G), the second condenser ( 5 G) is sequentially connected to the second subcooler ( 5 F), the first subcooler ( 5 D), and the heat exchanger ( 5 A) through pipelines at the top; the heat exchanger ( 5 A) is connected to the tenth pipeline ( 26 ) for the regeneration of the drying system ( 1 D), the second branch pipeline of the first distillation column ( 5 B) is directly connected to the first condenser ( 5 C) and the heat exchanger ( 5 A) separately; the first condenser ( 5 C) is also provided with two branch pipelines, wherein the first branch pipeline of the first condenser ( 5 C) is connected to the first distillation column ( 5 B), and the second branch pipeline of the first condenser ( 5 C) is connected to the second gas-liquid separator ( 5 H); the second distillation column ( 5 E) is provided with two branches, wherein the first branch of the second distillation column ( 5 E) is connected to the second condenser ( 5 G), and the second branch of the second distillation column ( 5 E) is connected to the heat exchanger ( 5 A); the second condenser ( 5 G) is also provided with two branches, wherein the first branch of the second condenser ( 5 G) is connected to the second distillation column ( 5 E), and the second branch of the second condenser ( 5 G) is sequentially connected to the second gas-liquid separator ( 5 H) and the third subcooler ( 5 J); one end of the third subcooler ( 5 J) is connected to the liquid nitrogen product channel, and the other end is connected to the heat exchanger ( 5 A) through a first throttle valve (V 4 ) through the third subcooler ( 5 J), the second gas-liquid separator ( 5 H) is connected to the heat exchanger ( 5 A), and the heat exchanger ( 5 A) is sequentially connected to the first compressor ( 5 K 1 ) and the second compressor ( 5 K 2 ), the second compressor ( 5 K 2 ) is provided with two branches, wherein the first branch of the second compressor ( 5 K 2 ) is sequentially connected to the high and low-temperature gas expander ( 5 P), the heat exchanger ( 5 A), and the second expansion end ( 5 U), and finally connected to the second gas-liquid separator ( 5 H) for circulation through the second expansion end ( 5 U), the second branch of the second compressor ( 5 K 2 ) is sequentially connected to the heat exchanger ( 5 A), the first expansion end ( 5 T), the heat exchanger ( 5 A), and finally connected to the first compressor ( 5 K 1 ) for circulation through the heat exchanger ( 5 A), the heat exchanger ( 5 A) is directly connected to the second gas-liquid separator ( 5 H), and a second throttle valve (V 3 ) is provided on the connecting pipeline, using the low-temperature distillation principle, the low-temperature nitrogen-containing gas obtained from the low-temperature compressor ( 3 A) is further purified and liquefied, so as to obtain the liquid nitrogen product.

2 . A method for using a device for producing liquid from flue gas with low energy consumption, comprising the following steps:

Pre) providing the device for producing liquid from flue gas with low energy consumption, wherein the device comprises a CO 2 and N 2 low-temperature medium-pressure adsorption system, an energy utilization system, a low-temperature filtration gas low-temperature compression system, a CO 2 low-temperature purification system ( 101 ), and a nitrogen liquid device system ( 100 ); the systems are interconnected through pipelines and valves, wherein the CO 2 and N 2 low-temperature medium-pressure adsorption system comprises a flue gas cooler ( 1 A), a first gas-liquid separator ( 1 B), a compression system ( 1 C), a drying system ( 1 D), a gas expander system, and a low-temperature medium-pressure adsorption device ( 1 H), which is used to cool, pressurize, dewater, and perform low-temperature adsorption separation of CO 2 and N 2 from the flue gas; the energy utilization system comprises an electric heater ( 2 E), a CO 2 compressor ( 2 A), a heat utilizer ( 2 B), and a second cooler ( 2 C), which is used to pressurize, recover heat and cool desorbed gas obtained from the CO 2 and N 2 low-temperature medium-pressure adsorption system; the low-temperature filtration gas low-temperature compression system comprises a low-temperature compressor ( 3 A), which is used for low-temperature pressurization of the low-temperature medium-pressure filtered gas obtained from the CO 2 and N 2 low-temperature medium-pressure adsorption system, the CO 2 low-temperature purification system ( 101 ) is used to further purify and liquefy the low-temperature medium-pressure gas obtained from the energy utilization system, to obtain a liquid CO 2 product; and the nitrogen liquid device system ( 100 ) is used to distill and liquefy medium-pressure gas discharged from the low-temperature compression system, to obtain a liquid nitrogen product;

one end of a flue gas cooler ( 1 A) in the CO 2 and N 2 low-temperature medium-pressure adsorption system is connected to a flue gas discharge port, while the other end is connected to a first gas-liquid separator ( 1 B), in the first gas-liquid separator ( 1 B), the liquid is discharged through a water outlet ( 13 ) of the first gas-liquid separator, and the gas enters the compression system ( 1 C) through a gas outlet ( 12 ) of the first gas-liquid separator for compression, cooling, and dewatering, the compressed, cooled, and dewatered flue gas enters the drying system ( 1 D) through a first pipeline ( 14 ) to dehydrate and dry thoroughly, so that the flue gas emitted from the drying system ( 1 D) has a water content of ppm level, the drying system ( 1 D) is connected to a expander system, wherein the gas expander system consists of a first expander boosting end ( 1 E), a first cooler ( 1 F), and a gas expansion end ( 1 G), the flue gas with ppm-level water content sequentially enters the first expander boosting end ( 1 E), the first cooler ( 1 F), and the gas expansion end ( 1 G) through the second pipeline ( 15 ), the gas expansion end ( 1 G) then enters the low-temperature medium-pressure adsorption device ( 1 H) through a rear third pipeline ( 18 ), where the CO 2 in the low-temperature medium-pressure flue gas is adsorbed and captured using the low-temperature medium-pressure adsorption principle, a crude CO 2 gas with a carbon purity of 85-90% is obtained at a desorption gas outlet ( 19 ) of the low-temperature medium-pressure adsorption device, and a medium-pressure crude nitrogen gas with a CO 2 concentration of less than 1 ppm is obtained at the low-temperature medium-pressure filtered gas outlet ( 20 ) of the low-temperature medium-pressure adsorption device; the nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%, thus achieving the purpose of carbon nitrogen separation, the low-temperature medium-pressure filtered gas outlet ( 20 ) is also connected to the low-temperature medium-pressure adsorption device ( 1 H) through a fourth pipeline ( 32 ), so that a portion of the low-temperature filtered gas enters the low-temperature medium-pressure adsorption device ( 1 H) through the fourth pipeline ( 32 ) as cold-blowing regeneration gas, to cold-blow the adsorbent in the low-temperature medium-pressure adsorption device ( 1 H);

the desorption gas outlet ( 19 ) of the low-temperature medium-pressure adsorption device is connected to the CO 2 compressor ( 2 A) in the energy utilization system, to compress and boost the crude CO 2 gas; the CO 2 compressor ( 2 A) is sequentially connected to the heat utilizer ( 2 B), the second cooler ( 2 C), and the CO 2 low-temperature purification system ( 101 ), the second cooler ( 2 C) further cools the cooled and pressurized crude CO 2 gas, such that the pressurized crude CO 2 gas exiting from the second cooler ( 2 C) meets the temperature and pressure requirements of the CO 2 low-temperature purification system ( 101 ), the CO 2 low-temperature purification system ( 101 ) is used to purify and refine the pressurized low-temperature CO 2 , yielding industrial-grade or food-grade CO 2 , the CO 2 low-temperature purification system ( 101 ) is connected to the heat utilizer ( 2 B) through a ninth pipeline ( 24 ), and the heat utilizer ( 2 B) is connected to the fourth pipeline ( 32 ) of the low-temperature medium-pressure adsorption device ( 1 H), to heat the low-temperature regeneration gas exiting from the CO 2 low-temperature purification system ( 101 ), which then enters the low-temperature medium-pressure adsorption device ( 1 H) as heated regeneration gas;

the low-temperature medium-pressure filtered gas outlet ( 20 ) of the low-temperature medium-pressure adsorption device is sequentially connected to the low-temperature compressor ( 3 A) and the nitrogen liquid device system ( 100 ) in the low-temperature filtered gas compression system at the rear, to pressurize all or most of the low-temperature filtered gas, which then enters the nitrogen liquid device system ( 100 ), the nitrogen liquid device system ( 100 ) is used to further refine and liquefy the pressurized low-temperature filtered gas to obtain the liquid nitrogen product, a tenth pipeline ( 26 ) is arranged at the rear of the nitrogen liquid device system ( 100 ), the tenth pipeline ( 26 ) is branched into two routes at the rear, one route is sequentially connected to the heat utilizer ( 2 B) and the electric heater ( 2 E), the electric heater ( 2 E) is connected to a sixth pipeline ( 102 ), and the sixth pipeline ( 102 ) is connected to the drying system ( 1 D), to heat the waste gas regeneration gas from the nitrogen liquid device system ( 100 ) to a required temperature before entering the drying system ( 1 D) as the regeneration gas for heating, the other route of the tenth pipeline ( 26 ) is directly connected to the sixth pipeline ( 102 ), to feed the waste gas regeneration gas from the nitrogen liquid device system ( 100 ) to directly enter the drying system ( 1 D) as cold blow gas for cold blowing;

the CO 2 low-temperature purification system ( 101 ) comprises a third condenser ( 4 F), an evaporator ( 4 D), a liquefier ( 4 E), and a third distillation column ( 4 G), wherein the third condenser ( 4 F) is mounted above the third distillation column ( 4 G), and the evaporator ( 4 D) is mounted below the third distillation column ( 4 G), the liquefier ( 4 E) is arranged separately outside the column; the second cooler ( 2 C) is connected to the evaporator ( 4 D), and the evaporator ( 4 D) is connected to the liquefier ( 4 E), the liquefier ( 4 E) is connected to the third distillation column ( 4 G) through an eighth pipeline ( 46 ); the third distillation column ( 4 G) is connected to the third condenser ( 4 F), and the third condenser ( 4 F) is connected to the third distillation column ( 4 G) through a seventh pipeline ( 110 ) to form a closed loop, a condensation liquid inlet channel ( 48 ) and a condensation gas outlet channel( 49 ) are formed in the third condenser ( 4 F), a ninth pipeline ( 24 ) is provided below the third distillation column ( 4 G) and is connected to the heat utilizer ( 2 B), a fifth pipeline ( 47 ) is provided at the bottom of the third distillation column ( 4 G) for obtaining the liquid CO 2 product;

the nitrogen liquid device system ( 100 ) comprises a circulating compression system, a high and low-temperature gas expander, a heat exchanger ( 5 A), a second gas-liquid separator ( 5 H), a distillation column system, and a subcooler, the circulating compression system consists of a first compressor ( 5 K 1 ) and a second compressor ( 5 K 2 ), the high and low-temperature gas expander is equipped with a second expander boosting end ( 5 P), a first expansion end ( 5 T), and a second expansion end ( 5 U), the subcooler consists of a first subcooler ( 5 D), a second subcooler ( 5 F), and a third subcooler ( 5 J), the distillation column system consists of a first distillation column ( 5 B) and a second distillation column ( 5 E), wherein a first condenser ( 5 C) is mounted above the first distillation column ( 5 B), and a second condenser ( 5 G) is mounted above the second distillation column ( 5 E), the low-temperature compressor ( 3 A) is sequentially connected to the heat exchanger ( 5 A) and the first distillation column ( 5 B), the first distillation column ( 5 B) is provided with two branch pipelines, wherein the first branch of the first distillation column ( 5 B) is sequentially connected to the first subcooler ( 5 D), the first condenser ( 5 C), the second distillation column ( 5 E), the second subcooler ( 5 F), and the second condenser ( 5 G), the second condenser ( 5 G) is sequentially connected to the second subcooler ( 5 F), the first subcooler ( 5 D), and the heat exchanger ( 5 A) through pipelines at the top; the heat exchanger ( 5 A) is connected to the tenth pipeline ( 26 ) for the regeneration of the drying system ( 1 D), the second branch pipeline of the first distillation column ( 5 B) is directly connected to the first condenser ( 5 C) and the heat exchanger ( 5 A) separately; the first condenser ( 5 C) is also provided with two branch pipelines, wherein the first branch pipeline of the first condenser ( 5 C) is connected to the first distillation column ( 5 B), and the second branch pipeline of the first condenser ( 5 C) is connected to the second gas-liquid separator ( 5 H); the second distillation column ( 5 E) is provided with two branches, wherein the first branch of the second distillation column ( 5 E) is connected to the second condenser ( 5 G), and the second branch of the second distillation column ( 5 E) is connected to the heat exchanger ( 5 A); the second condenser ( 5 G) is also provided with two branches, wherein the first branch of the second condenser ( 5 G) is connected to the second distillation column ( 5 E), and the second branch of the second condenser ( 5 G) is sequentially connected to the second gas-liquid separator ( 5 H) and the third subcooler ( 5 J); one end of the third subcooler ( 5 J) is connected to the liquid nitrogen product channel, and the other end is connected to the heat exchanger ( 5 A) through a first throttle valve (V 4 ) through the third subcooler ( 5 J), the second gas-liquid separator ( 5 H) is connected to the heat exchanger ( 5 A), and the heat exchanger ( 5 A) is sequentially connected to the first compressor ( 5 K 1 ) and the second compressor ( 5 K 2 ), the second compressor ( 5 K 2 ) is provided with two branches, wherein the first branch of the second compressor ( 5 K 2 ) is sequentially connected to the high and low-temperature gas expander ( 5 P), the heat exchanger ( 5 A), and the second expansion end ( 5 U), and finally connected to the second gas-liquid separator ( 5 H) for circulation through the second expansion end ( 5 U), the second branch of the second compressor ( 5 K 2 ) is sequentially connected to the heat exchanger ( 5 A), the first expansion end ( 5 T), the heat exchanger ( 5 A), and finally connected to the first compressor ( 5 K 1 ) for circulation through the heat exchanger ( 5 A), the heat exchanger ( 5 A) is directly connected to the second gas-liquid separator ( 5 H), and a second throttle valve (V 3 ) is provided on the connecting pipeline, using the low-temperature distillation principle, the low-temperature nitrogen-containing gas obtained from the low-temperature compressor ( 3 A) is further purified and liquefied, so as to obtain the liquid nitrogen product;

1) Flue gas pre-treatment:

Performing compression, cooling, dewatering, and drying treatment on the flue gas, wherein the water content of the treated flue gas is less than 1 ppm;

2) Coarse separation of CO 2 and N 2 gases:

Introducing the gas from the step 1) into the gas expander system to obtain crude carbon dioxide gas with a carbon purity of 85-90%, and medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 ppm, wherein the nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%;

3) Purification and liquefaction to obtain the liquid CO 2 product

Introducing the crude CO 2 gas with a carbon purity of 85-90% obtained from the step 2) into the CO 2 low-temperature purification system ( 101 ) to obtain the liquid CO 2 product; and

4) Purification and liquefaction to obtain the liquid N 2 product:

Introducing the medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 ppm obtained from the step 2) into the nitrogen liquid device system ( 100 ) to obtain the liquid N 2 product.

3 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 2 , wherein the specific method for the step 1 comprises: feeding the flue gas emitted at normal temperature and pressure into a flue gas cooler inlet ( 10 ), cooling the flue gas with a cooling medium, passing the cooled flue gas through the first gas-liquid separator ( 1 B) to remove condensed water from the flue gas, and discharging the water through the water outlet ( 13 ) of the first gas-liquid separator; the cooled flue gas subsequently flows through a gas outlet ( 12 ) of the first gas-liquid separator into the compression system ( 1 C) for compression, cooling, and dewatering, the pressurized medium-pressure flue gas is then conveyed through the first pipeline ( 14 ) into the drying system ( 1 D) for further dewatering and drying, such that the water content of the medium-pressure flue gas exiting from the drying system ( 1 D) is less than 1 ppm.

4 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 2 , wherein the specific method for the step 2 comprises: pressurizing at the first expander boosting end ( 1 E) of the gas expander system, cooling by the first cooler ( 1 F), expanding and cooling at the gas expansion end ( 1 G), feeding the expanded low-temperature medium-pressure gas into the low-temperature medium-pressure adsorption device ( 1 H), adsorbing and capturing CO 2 in the low-temperature medium-pressure flue gas according to the principle of low-temperature medium-pressure adsorption, to obtain the crude CO 2 with a carbon purity of 85-90% from the desorbed gas outlet of the low-temperature medium-pressure adsorption device ( 1 H), and obtain medium-pressure crude nitrogen with a CO 2 concentration of less than 1 ppm from the low-temperature medium-pressure filtered gas outlet ( 20 ) of the low-temperature medium-pressure adsorption device ( 1 H); the nitrogen purity of the medium-pressure rough nitrogen gas is 87-93%, thereby achieving the separation of carbon and nitrogen, the low-temperature medium-pressure adsorption device ( 1 H) switches between adsorption, desorption, regeneration, and cold blowing through valves and pipelines.

5 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 2 , wherein the specific steps for obtaining liquid CO 2 in the step 3 comprise: feeding the desorbed gas from the desorption gas outlet ( 19 ) of the low-temperature medium-pressure adsorption device into the CO 2 compressor ( 2 A) in the energy utilization system, pressurizing the crude CO 2 gas, feeding the pressurized high-temperature high-pressure gas into the heat utilizer ( 2 B) for heat exchange, adsorbing and utilizing the thermal energy of the pressurized coarse CO 2 gas, causing the gas to cool, then entering the second cooler ( 2 C), and further cooling the crude CO 2 gas, such that the pressurized crude CO 2 gas exiting from the second cooler ( 2 C) meets the temperature and pressure requirements for the raw materials entering the CO 2 low-temperature purification system ( 101 ), the raw material temperature is 20-30° C., and the pressure is 2.0-2.5 MPaA, the gas then enters the CO 2 low-temperature purification system ( 101 ), to purify and refine the pressurized low-temperature CO 2 to obtain industrial-grade or food-grade CO 2 , the low-temperature regeneration gas is extracted from the ninth pipeline ( 24 ) of the CO 2 low-temperature purification system ( 101 ) and can be reheated using the heat utilizer ( 2 B), the reheated regeneration gas then enters the low-temperature medium-pressure adsorption device ( 1 H), to heat and regenerate an adsorbent requiring regeneration, which eliminates the need for external heat energy during the regeneration process of the low-temperature medium-pressure adsorption device ( 1 H).

6 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 2 , wherein the specific steps for obtaining liquid N 2 in the step 4 comprise: compressing all or most of the medium-pressure crude N 2 gas with a carbon dioxide concentration of less than 1 ppm from the low-temperature medium-pressure adsorption device ( 1 H) by the low-temperature compressor ( 3 A) in the low-temperature filtration gas low-temperature compression system, and directly entering the nitrogen liquid device system ( 100 ), when the adsorbent in the low-temperature medium-pressure adsorption device ( 1 H) requires cold blowing for regeneration, a portion of the low-temperature filtered gas as cold blow regeneration gas is fed into the low-temperature medium-pressure adsorption device ( 1 H) through the fourth pipeline ( 32 ), to cold-blow the adsorbent in the low-temperature medium-pressure adsorption device ( 1 H), the pressurized filtered gas then enters the nitrogen liquid device system ( 100 ) for distillation and liquefaction, the waste gas regeneration gas from the nitrogen liquid device system ( 100 ) is fed into the heat utilizer ( 2 B) through the tenth pipeline ( 26 ) to be heated, then enters the electric heater ( 2 E) to be further heated to the required temperature, and enters a second inlet of the drying system ( 1 D) as heated regeneration gas, the waste gas regeneration gas from the nitrogen liquid device system ( 100 ) can also be directly fed into the second inlet of the drying system ( 1 D) through the tenth pipeline ( 26 ) as cold blow gas.

7 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 5 , wherein the specific method for purifying CO 2 gas in the CO 2 low-temperature purification system ( 101 ) comprises: feeding the crude CO 2 gas entering the CO 2 low-temperature purification system ( 101 ) into the evaporator ( 4 D) to evaporate the liquid from the bottom of the third distillation column ( 4 G), cooling, then entering the liquefier ( 4 E) to be cooled to the saturation temperature, and entering the middle section of the third distillation column ( 4 G) to undergo distillation, in the third condenser ( 4 F), the gas from the top of the third distillation column ( 4 G) is condensed and returned as the reflux liquid at the top of the third distillation column ( 4 G) to undergo distillation, and enters the third condenser ( 4 F) through the condensation liquid inlet channel ( 48 ) to be heated and vaporized to provide cooling energy, the liquid CO 2 product is obtained at the bottom of the third distillation column ( 4 G), and the liquid CO 2 product is output through the fifth pipeline ( 47 ) at the bottom of the third distillation column ( 4 G), and is then extracted through the ninth pipeline ( 24 ) from the upper part of the third distillation column ( 4 G) to enter the heat utilizer ( 2 B) for heating.

8 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 6 , wherein the specific method for purifying the N 2 gas in the nitrogen liquid device system ( 100 ) comprises: overcooling the gas entering the nitrogen liquid device system ( 100 ) to a saturated state in the heat exchanger ( 5 A) and then entering the distillation column system, the distillation column system adopts a dual-column distillation process, a portion of the medium-pressure nitrogen gas from the top of the first distillation column ( 5 B) is condensed in the first condenser ( 5 C), with the condensed liquid nitrogen portion returning to the top of the first distillation column ( 5 B), and a portion enters the second gas-liquid separator ( 5 H), the liquid extracted from the bottom of the first distillation column ( 5 B) is overcooled in a first subcooler ( 5 D) and then enters the first condenser ( 5 C) as a coolant, after heating, the liquid exits from the first condenser ( 5 C) and enters the bottom of the second distillation column ( 5 E) for further distillation, a portion of the low-pressure nitrogen gas exiting from the top of the second distillation column ( 5 E) is condensed in the second condenser ( 5 G), with the liquid nitrogen portion returning to the top of the second distillation column ( 5 E), while a portion enters the second gas-liquid separator ( 5 H), another portion of the medium-pressure nitrogen gas exiting from the top of the first distillation column ( 5 B) is reheated in the heat exchanger ( 5 A) and then enters the second compressor ( 5 K 2 ) in the circulating compression system for compression, another portion of the low-pressure nitrogen gas exiting from the top of the second distillation column ( 5 E) is reheated in the heat exchanger ( 5 A) and enters the first compressor ( 5 K 1 ) and the second compressor ( 5 K 2 ) sequentially in the circulating compression system for compression, the gas compressed by the second compressor ( 5 K 2 ) is directed into the second expander boosting end ( 5 P) of the high and low-temperature gas expander for pressurization, and after pressurization, enters the heat exchanger ( 5 A) for cooling, a portion of the gas is extracted from the middle of the heat exchanger ( 5 A) and enters the second expansion end ( 5 U) for expansion, the expanded fluid then enters the second gas-liquid separator ( 5 H), the remaining gas is extracted from the bottom of the heat exchanger ( 5 A), throttled through the second throttle valve (V 3 ), and enters the second gas-liquid separator ( 5 H); another portion of gas directly enters the heat exchanger ( 5 A) and is extracted from the upper part of the heat exchanger ( 5 A) into the first expansion end ( 5 T) for expansion, the expanded gas enters the heat exchanger ( 5 A) for reheating and then enters the first compressor ( 5 K 1 ) and the second compressor ( 5 K 2 ) sequentially for compression in the circulating compression system, after gas-liquid separation in the second gas-liquid separator ( 5 H), the liquid flows out from the liquid outlet of the second gas-liquid separator ( 5 H), and is overcooled by the third subcooler ( 5 J), and a portion of the liquid is throttled through the first throttle valve (V 4 ) and enter the third subcooler ( 5 J) to be reheated, the reheated fluid enters the heat exchanger ( 5 A) to be further reheated and discharged as waste gas from the nitrogen liquid device system ( 100 ); the remaining liquid is extracted from the liquid nitrogen product channel ( 85 ) as a high-purity liquid nitrogen product, the gas in the second gas-liquid separator ( 5 H) exits through the gas outlet of the second gas-liquid separator ( 5 H), enters the heat exchanger ( 5 A) to be reheated, and then enters the first compressor ( 5 K 1 ) and the second compressor ( 5 K 2 ) sequentially for compression in the circulating compression system, the liquid from the bottom of the second distillation column ( 5 E) is overcooled in a second subcooler ( 5 F) and then evaporated on the evaporation side of the second condenser ( 5 G), the evaporated gas is reheated successively through the second subcooler ( 5 F) and the first subcooler ( 5 D), the reheated fluid enters the heat exchanger ( 5 A) for further reheating and is discharged as waste gas from the nitrogen liquid device system ( 100 ).

9 . The method for using the device for producing liquid from flue gas with low energy consumption according to claim 6 , wherein the adsorbent used in the low-temperature medium-pressure adsorption device ( 1 H) is primarily a molecular sieve, silica gel, and activated carbon, and is configured with two units, which can be used individually or simultaneously, the drying system ( 1 D) consists of two drying tanks connected in parallel, and the two drying tanks can be used individually or simultaneously.