Low energy consumption liquid production device using flue gas and method of using same

Abstract

To provide: a device which produces liquid by utilizing flue gas with low energy consumption; and a use method thereof.SOLUTION: A device includes: a CO2 and N2 intermediate pressure adsorption system; an energy utilization system; a low-temperature filtration gas low-temperature compression system; a CO2 low-temperature purification system; and a nitrogen liquid device system which are connected by a tube line and a valve therebetween. The CO2 and N2 intermediate pressure adsorption system includes a flue gas cooler, a first gas-liquid separator, a compression system, a drying system, a gas expansion system, and a low-temperature intermediate pressure adsorption device. An energy utilization system includes: an electric heater, a CO2 compressor, a heat utilization device, and a cooler. The low-temperature filtration gas low-temperature compression system includes a low-temperature compression machine. The CO2 low-temperature purification system causes a liquid CO2 product to be obtained. The nitrogen liquid device system is used in such an application as to distill and liquefy intermediate pressure gas discharged from the low-temperature compression system to obtain a liquid nitrogen product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of flue gas, and to a low energy consumption liquid production device using flue gas and a method for using the same. [Background technology]

[0002] CO2 separation and capture technologies for energy use mainly include absorption, adsorption, membrane separation, and low-temperature phase change separation. Solution absorption is the most mature CO2 capture method, and is used in many industrial applications around the world to extract carbon dioxide from flue gas. It can separate CO2 from constant-concentration flue gas at atmospheric pressure, with high throughput and high purity. However, regenerating the solution after absorption requires a large amount of heat, consumes resources, and requires constant replenishment after a certain period of use. Chemical absorbents are toxic and corrosive, which has a significant impact on the environment and is expensive to manufacture and capture. Membrane separation uses thin polymer membranes to separate gases based on the differences in their permeability, driven by pressure differences. This technology is limited in terms of large-scale application. Pressure swing adsorption technology has many advantages, such as easy regeneration of the absorbent, good durability of the absorbent, and simple equipment, but the cost and energy consumption of ambient pressure swing adsorption technology for flue gas with low carbon dioxide concentrations are still very high.

[0003] Chinese Patent CN107899376A discloses an apparatus and method for combined capture and recovery of carbon dioxide and nitrogen from flue gas, which is a membrane separation recovery method, but membranes have high requirements for the purity of the gas source, a short service life, low product purity, and are expensive, making them unsuitable for industrialized large-scale production.

[0004] Chinese Patent CN210825439U discloses a system for simultaneously recovering carbon dioxide and nitrogen from the flue gas of a coal-fired power plant boiler. The system includes a flue gas pretreatment system, a PSA1 system, a PSA2 system, a carbon dioxide compression and purification system, a carbon dioxide distillation and storage system, and a PSA nitrogen production system. Although these systems can maximize the capture of carbon dioxide and nitrogen, they have problems with product purity of only about 99.9%, limited flexibility in equipment operation, and high energy consumption.

[0005] Chinese Patent CN216481836U discloses a system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas. The system includes a flue gas pretreatment system, a carbon-nitrogen separation system, a carbon dioxide secondary purification system, and a nitrogen concentration and purification system, which can recover the maximum amount of carbon dioxide and nitrogen. However, the carbon-nitrogen separation system, the carbon dioxide secondary purification system, and the nitrogen concentration and purification system all use ambient temperature variable pressure adsorption technology, and the adsorption pressure reaches 0.2-1.0 MPa, which results in relatively high energy consumption.

[0006] Chinese Patent CN115790076A discloses an apparatus and method for recovering carbon dioxide and nitrogen from flue gas. The apparatus includes a pre-treatment system, a carbon dioxide and nitrogen separation system, a nitrogen purification and liquefaction system, and a carbon dioxide purification and liquefaction system. The system uses the large amount of cooling capacity released by the vaporization of LNG (liquefied natural gas) to drive the liquefaction of carbon dioxide and nitrogen in the flue gas, which significantly reduces energy consumption and costs. However, the system consumes a large amount of LNG and has strict requirements for the LNG source. The low-temperature adsorption is performed under atmospheric pressure, which results in poor adsorption efficiency, a large volume of adsorption equipment, and high costs. Summary of the Invention [Problem to be solved by the invention]

[0007] In light of the above technical background, the present invention aims to provide an apparatus for producing liquids from flue gas with low energy consumption and a method for using the same. By utilizing the cooling capacity released when compressed gas expands, and combining low-temperature and medium-pressure adsorption technology, and combining the compression of various compressors and the expansion cooling technology of expanders in the apparatus, producing liquids from flue gas has high economic and social value. [Means for solving the problem]

[0008] The present invention includes a low-temperature medium-pressure CO2 and N2 adsorption system, an energy utilization system, a low-temperature filtered gas low-temperature compression system, a CO2 low-temperature purification system, and a nitrogen liquid device system, which are connected to each other by tubing lines and valves. The low-temperature medium-pressure CO2 and N2 adsorption system includes a flue gas cooler, a first gas-liquid separator, a compression system, a drying system, a gas expansion system, and a low-temperature medium-pressure adsorption device, and is used for cooling, pressurizing, and dehydrating flue gas, and for low-temperature adsorption separation of CO2 and N2. The energy utilization system includes an electric heater, a CO2 compressor, a heat utilization unit, and a second cooler, and is used for the low-temperature adsorption separation of CO2 and N2. The low-temperature filtered gas low-temperature compression system includes a low-temperature compressor and is used for low-temperature pressurization of the low-temperature medium-pressure filtered gas obtained from the CO2 and N2 low-temperature medium-pressure adsorption systems. The CO2 low-temperature purification system is used to further purify and liquefy the low-temperature medium-pressure gas obtained from the energy utilization system to obtain liquid CO2 products. The nitrogen liquid production system is used to obtain liquid nitrogen products by distilling and liquefying the medium-pressure gas from the low-temperature compression system, thereby providing a low-energy consumption liquid production device that utilizes flue gas.

[0009] Preferably, one end of the flue gas cooler of the low-temperature and medium-pressure CO2 and N2 adsorption system is connected to the flue gas outlet, and the other end is connected to the first gas-liquid separator. The liquid in the first gas-liquid separator is discharged from the water outlet of the first gas-liquid separator. The gas enters the compression system through the gas outlet of the first gas-liquid separator, undergoes compression, cooling and dehydration. The compressed, cooled and dehydration-removed flue gas enters the drying system through the first tube line for thorough dehydration and drying. The moisture content of the flue gas leaving the drying system is at ppm level. The drying system is connected to the rear gas expander system, which includes the first expander booster end, the first cooler and the gas expansion end. The flue gas with a moisture content of ppm level passes through the second tube line and gradually enters the first expander booster end, the first cooler and the gas expansion end. The gas that arrives at the gas expansion end enters the low-temperature medium-pressure adsorption unit through the third tubular line at the rear, and uses the principle of low-temperature medium-pressure adsorption to adsorb and capture CO2 in the flue gas. Crude carbon dioxide gas with a carbon purity of 85-90% is obtained from the desorbed gas outlet of the low-temperature medium-pressure adsorption unit. Medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 pmm is obtained from the low-temperature medium-pressure filtered gas outlet of the low-temperature medium-pressure adsorption unit. The nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%, achieving the purpose of carbon and nitrogen separation. The low-temperature medium-pressure filtered gas outlet is further connected to the low-temperature medium-pressure adsorption unit through the fourth tubular line, and a portion of the low-temperature filtered gas enters the low-temperature medium-pressure adsorption unit through the fourth tubular line as a gas for blowing and cooling the regeneration gas, and blows and cools the adsorbent in the low-temperature medium-pressure adsorption unit.

[0010] Preferably, the desorption gas outlet of the low-temperature medium-pressure adsorption device is connected to a CO2 compressor in an energy utilization system to compress the crude carbon dioxide. The CO2 compressor is sequentially connected to a heat converter, a second cooler, and a CO2 low-temperature purification system, of which the second cooler further cools the cooled and compressed crude carbon dioxide so that the carbon dioxide gas compressed by the second cooler meets the raw material temperature and pressure requirements of the CO2 low-temperature purification system. The CO2 low-temperature purification system is used to purify and purify the compressed low-temperature CO2, and industrial-grade or food-grade carbon dioxide can be obtained. The CO2 low-temperature purification system is connected to a heat converter through a ninth tubing line, and the heat converter is connected to the fourth tubing line of the low-temperature medium-pressure adsorption device. The low-temperature regeneration gas from the CO2 low-temperature purification system is heated and then introduced into the low-temperature medium-pressure adsorption device for use as heated regeneration gas.

[0011] Preferably, the rear of the low-temperature medium-pressure filtered gas outlet of the low-temperature medium-pressure adsorption device is gradually connected to the low-temperature compressor in the low-temperature filtered gas compression system and a nitrogen liquid system, and all or most of the low-temperature filtered gas is pressurized by the low-temperature compression system and then sent to the nitrogen liquid system, which is used to further distill and liquefy the low-temperature pressurized filtered gas using the principle of low-temperature distillation to obtain liquid nitrogen product. A tenth tube line is installed behind the tenth tube line, and the rear of the tenth tube line is divided into two routes, one of which is gradually connected to a heat converter and an electric heater, and the electric heater is connected to the sixth tube line, which is connected to a drying system, and the waste gas and regeneration gas from the nitrogen liquid system are heated to a required temperature and then fed to the drying system to be heated as regeneration gas. The other route of the tenth tube line is directly connected to the sixth tube line, and the waste gas and regeneration gas from the nitrogen liquid system are directly fed to the drying system to be used as blown cooling gas.

[0012] Preferably, the CO2 low-temperature purification system includes a third condenser, an evaporator, a liquefier, and a third distillation column, wherein the third condenser is installed above the third distillation column and the evaporator is installed below it, and the liquefier is installed separately from the tower, the second cooler is connected to the evaporator, the evaporator is connected to the liquefier, the liquefier is connected to the third distillation column through an eighth tube line, the third distillation column is connected to the third condenser, and the third condenser is connected to the third distillation column through a seventh tube line to form a circuit, a condensate inlet passage and a condensate vapor outlet passage are opened above the third condenser, a ninth tube line is opened below the third distillation column and connected to a heat utility, and a fifth tube line is opened at the bottom of the third distillation column to obtain liquid carbon dioxide product.

[0013] Preferably, the nitrogen liquid device system comprises a circulating compression system, a high-temperature gas expander, a heat exchanger, a second gas-liquid separator, a distillation column system and a supercooler, wherein the circulating compression system comprises a first compressor and a second compressor, and a second expander booster end, a first expansion end and a second expansion end are respectively installed on the high-temperature gas expander, the supercooler comprises a first supercooler, a second supercooler and a third supercooler, and the distillation column system comprises a first distillation column and a second distillation column, wherein a first condenser is installed above the second distillation column and a third condenser is installed above the second distillation column. A second condenser is installed, and the low-temperature compressor is connected to the heat exchanger and the first distillation column. Two branch tube lines are opened on the first distillation column, of which the first branch tube line of the first distillation column is connected to the first subcooler, the first condenser, the second distillation column, the second subcooler, and the second condenser. The upper part of the second condenser is connected to the second subcooler, the first subcooler, and the heat exchanger through a tube line. The heat exchanger is connected to the tenth tube line, which is used for regenerating the drying system. The second branch tube line of the first distillation column is directly connected to the first condenser and the heat exchanger, respectively. The first condenser is also provided with two branch tube lines, the first branch tube line of which is connected to the first distillation column and the second branch tube line of which is connected to the second gas-liquid separator; the second distillation column is also provided with two branch tube lines, the first branch tube line of which is connected to the second condenser and the second branch tube line of which is connected to the heat exchanger; the second condenser is also provided with two branch tube lines, the first branch tube line of which is connected to the second distillation column and the second condenser the second branch tube line is connected to the second gas-liquid separator and the third supercooler, one end of the third supercooler is connected to the liquid nitrogen product passage, and the other end is connected to the heat exchanger through the first throttle valve and the third supercooler, the second gas-liquid separator is connected to the heat exchanger, and the heat exchanger is connected to the first compressor and the second compressor, the first branch tube line of the second compressor is connected to the high and low temperature gas expander, the heat exchanger, the second expansion end, and finally to the second gas-liquid separator through the second expansion end to form a circulation system;The second branch tube line of the second compressor is connected to a heat exchanger, a first expansion end, a heat exchanger, and finally to the first compressor through a heat exchanger to form a circulation system. The heat exchanger is directly connected to a second gas-liquid separator, and a second throttle valve is installed on the connecting tube line, which uses the principle of cryogenic distillation to further purify and liquefy the low-temperature nitrogen-containing gas obtained from the low-temperature compressor, thereby obtaining liquid nitrogen product.

[0014] A method for using the above-mentioned low energy consumption liquid production device by utilizing flue gas, the method comprising the steps of: 1) Flue gas pretreatment: Flue gas is compressed, cooled, dehydrated, and dried to reduce the moisture content of the treated flue gas to a level of <1 ppm. 2) Rough gas separation of CO2 and N2: The gas in step 1) is passed through a gas expander system to obtain crude carbon dioxide gas with a carbon purity of 85-90% and medium-pressure crude nitrogen with a carbon dioxide concentration of less than 1 ppm, and the nitrogen purity of the medium-pressure crude nitrogen is 87-93%. 3) Purification of liquid CO2 products obtained by liquefaction: In step 2), the crude carbon dioxide with a carbon concentration of 85-90% is passed through a CO2 low-temperature purification system to obtain a liquid CO2 product. 4) Purification of liquid N2 products obtained by liquefaction: The medium pressure nitrogen in step 2) having a carbon dioxide concentration of less than 1 ppm is passed through a nitrogen liquid system to obtain a liquid N2 product.

[0015] Preferably, the specific method of step 1 is as follows: the discharged normal temperature and pressure flue gas enters the inlet of a flue gas cooler, and the cooling medium cools the flue gas; the cooled flue gas passes through a first gas-liquid separator to remove condensed water in the flue gas, and the water is discharged through a water outlet of the first gas-liquid separator; the cooled flue gas passes through a gas outlet of the first gas-liquid separator to enter a compression system for compression, cooling and water removal; the pressurized medium-pressure flue gas passes through a first tube line to enter a drying system for further water removal and drying, so that the moisture content of the medium-pressure flue gas exiting the drying system is less than 1 ppm.

[0016] Preferably, the specific method of step 2 is as follows: the gas that is subsequently boosted into the booster end of the first expander of the gas expander system is further cooled by a first cooler, and then enters the gas expansion end for expansion and cooling; the expanded low-temperature and medium-pressure gas enters a low-temperature and medium-pressure adsorption device to adsorb and capture CO2 in the low-temperature and medium-pressure flue gas using the principle of low-temperature and medium-pressure adsorption; crude carbon dioxide gas with a carbon purity of 85-90% is obtained from the desorbed gas outlet of the low-temperature and medium-pressure adsorption device; and medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 ppm is obtained from the low-temperature and medium-pressure filtered gas outlet of the low-temperature and medium-pressure adsorption device, with a nitrogen purity of 87-93%, thereby achieving the purpose of carbon-nitrogen separation; the low-temperature and medium-pressure adsorption device is adapted to switch between adsorption, desorption, regeneration and blow-cooling through valves and tubing lines.

[0017] Preferably, the specific step of obtaining liquid CO2 from step 3 is as follows: the desorbed gas from the desorbed gas outlet of the low-temperature, medium-pressure adsorption device enters the CO2 compressor of the energy utilization system to increase the pressure of the crude carbon dioxide gas; the pressurized, high-temperature, high-pressure gas is then passed through a heat exchanger for heat exchange, absorbing and utilizing the heat of the pressurized crude carbon dioxide gas; and after being cooled, it enters a secondary cooler to further cool the cooled and pressurized crude carbon dioxide gas. The pressurized carbon dioxide gas in the secondary cooler meets the feed temperature and pressure requirements of the CO2 low-temperature purification system, where the feed temperature is 20-30°C and the pressure is 2.0-2.5 MPa. The pressurized low-temperature CO2 then enters the CO2 low-temperature purification system for purification and purification, obtaining industrial- or food-grade carbon dioxide. The low-temperature regeneration gas extracted from the ninth tube line of the CO2 low-temperature purification system can be reheated using a heat converter. The heated regeneration gas is then passed through the low-temperature, medium-pressure adsorption device to heat the adsorbent that needs to be regenerated, eliminating the need to rely on external energy sources for regeneration of the low-temperature, medium-pressure adsorption device.

[0018] Preferably, in the specific step of obtaining liquid N2 from step 4, all or most of the crude nitrogen gas having a carbon dioxide concentration of less than 1 ppm output from the low-temperature medium pressure adsorption device is subjected to low-temperature filtration, and the filtered gas is compressed in a low-temperature compressor of a low-temperature compression system and then directly input into a nitrogen liquid system. When blow-cooling is required for regenerating the adsorbent in the low-temperature medium pressure adsorption device, part of the low-temperature filtered gas is input into the low-temperature medium pressure adsorption device through the fourth tube line as a regeneration gas blow-cooling gas to blow-cool the adsorbent in the low-temperature medium pressure adsorption device. The pressurized filtered gas enters the nitrogen liquid system for distillation and liquefaction. The waste gas regeneration gas output from the nitrogen liquid system enters a heat utility through the tenth tube line and is heated, then further entered into an electric heater to be heated to the required temperature, and then input into the second inlet of the drying system to be used as heated regeneration gas. The waste gas regeneration gas output from the nitrogen liquid system is also directly input into the second inlet of the drying system through the tenth tube line to be used as a blow-cooling gas.

[0019] Preferably, the specific CO2 gas purification method in the CO2 low-temperature purification system is as follows: the crude carbon dioxide entering the CO2 low-temperature purification system first enters an evaporator to evaporate the liquid at the bottom of the third distillation column, and after being cooled, enters a liquefier to be cooled to saturation temperature and then enters the middle of the third distillation column to participate in distillation; in the third condenser, the gas exiting the top of the third distillation column is condensed and then participates in distillation as the reflux liquid at the top of the third distillation column; and enters the third condenser through the condensate passage; the condensate, which provides cooling power, is heated and vaporized to obtain liquid carbon dioxide product at the bottom of the third distillation column; the liquid carbon dioxide product is output from the fifth tube line at the bottom of the third distillation column; and the gas extracted from the ninth tube line at the middle and upper part of the third distillation column enters a heat utility to be heated.

[0020] Preferably, the specific N2 gas purification method in the nitrogen liquid system is as follows: the gas entering the nitrogen liquid system is supercooled by a heat exchanger until saturated, and then enters the distillation column system; the distillation column system has a double tower structure; a part of the medium pressure nitrogen exiting the top of the first distillation column is condensed by a first condenser; the liquid nitrogen part is refluxed to the top of the first distillation column; and a part enters the second gas-liquid separator; the liquid extracted from the bottom of the first distillation column is supercooled through a first supercooler and then enters the first condenser to be used as cooling capacity; and after heating, it exits the first condenser and is used as cooling capacity. It enters the bottom of the distillation column and participates in distillation. Part of the low-pressure nitrogen from the top of the second distillation column is condensed by the second condenser, and the liquid nitrogen part is refluxed to the top of the second distillation column. Part of it enters the second gas-liquid separator. Another part of the medium-pressure nitrogen gas from the top of the first distillation column is reheated in the heat exchanger and then compressed in the second compressor of the cyclic compression system. Another part of the low-pressure nitrogen from the top of the second distillation column is reheated by the heat exchanger and then compressed in the first and second compressors of the cyclic compression system. The first gas compressed by the second compressor is The high and low temperature gas enters the second expander booster end of the expander to be boosted, and after boosting, it enters the heat exchanger to be cooled. Some of the gas is extracted from the middle of the heat exchanger and enters the second expansion end to be expanded. The expanded fluid enters the second gas-liquid separator. The remaining gas is extracted from the bottom of the heat exchanger and enters the second gas-liquid separator through the second throttle valve. The other gas directly enters the heat exchanger and is extracted from the middle and upper part of the heat exchanger to be expanded in the first expansion end. The expanded gas also enters the heat exchanger to be reheated, and then enters the first and second compressors of the cyclic compression system to be compressed back and forth. The liquid is compressed and separated into gas and liquid in the second gas-liquid separator, after which the liquid flows out from the liquid outlet of the second gas-liquid separator and is supercooled in the third supercooler, a portion of the liquid is adjusted in flow rate by the first throttle valve and reheated in the third supercooler, the reheated liquid flows into the heat exchanger and is further reheated and discharged from the nitrogen liquid system as waste gas, the remaining liquid is extracted from the liquid nitrogen product passage and used as high-purity liquid nitrogen product, the gas in the second gas-liquid separator flows out from the gas outlet of the second gas-liquid separator and is reheated in the heat exchanger,The liquid from the bottom of the second distillation column is subcooled by the second subcooler and then enters the evaporation side of the second condenser to be evaporated. The evaporated gas is reheated by the second subcooler and the first subcooler. The reheated liquid enters the heat exchanger for further reheating and then leaves the nitrogen liquid system as waste gas.

[0021] Preferably, the adsorbent used in the low-temperature medium-pressure adsorption device is mainly composed of molecular sieves, silica gel, and activated carbon. Two units are installed, but they can be used alone or simultaneously. The drying system consists of two dryers connected in parallel, and the two dryers can be used alone or simultaneously. [Effects of the Invention]

[0022] The low energy consumption liquid production device and method for using flue gas provided by the present invention have the following beneficial effects: 1) This device and method can meet the demands of different temperature zones and pressures by using a perfect combination of compression and expansion according to the different temperature and pressure conditions of each system. 2) This device and method uses deep low-temperature and medium-pressure adsorption technology to achieve carbon and nitrogen separation, efficiently obtaining relatively high-content crude carbon dioxide gas and nitrogen gas, and by using an energy utilization system to effectively utilize the compression heat of the compressor, the heating power of the device and the power of the electric heater are reduced, thereby reducing overall energy consumption. 3) The present invention utilizes the low-temperature and medium-pressure adsorption separation characteristics to separate CO2 and N2 efficiently and at low cost, and at the same time, uses low-temperature precision distillation to purify and liquefy CO2 and N2, thereby efficiently obtaining high-purity liquid carbon dioxide and high-purity liquid nitrogen. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a simplified flowchart of the present invention. [Figure 2] 1 is a structural diagram of a nitrogen liquid device system. [Figure 3] 1 is a structural schematic diagram of a carbon dioxide low-temperature purification system. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described in detail below with reference to the drawings. As shown in Fig. 1, the present invention comprises a low-temperature medium-pressure CO2 and N2 adsorption system, an energy utilization system, a low-temperature filtered gas low-temperature compression system, a CO2 low-temperature purification system 101, and a nitrogen liquid unit system 100, which are connected to each other by tubing lines and valves. The low-temperature medium-pressure CO2 and N2 adsorption system comprises a flue gas cooler 1A, a first gas-liquid separator 1B, a compression system 1C, a drying system 1D, a gas expansion system, and a low-temperature medium-pressure adsorption unit 1H, which is used for cooling, pressurizing, and dehydrating flue gas, and for low-temperature adsorption separation of CO2 and N2. The energy utilization system comprises an electric heater 2E, a CO2 compressor 2A, a heat utilization unit 2B, a second The low-temperature filtered gas low-temperature compression system includes a low-temperature compressor 3A and is used to low-temperature compress the low-temperature medium-pressure filtered gas obtained from the low-temperature medium-pressure adsorption system of CO2 and N2. The CO2 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 CO2 product. The nitrogen liquid production system 100 is used to obtain a liquid nitrogen product by distilling and liquefying the medium-pressure gas from the low-temperature compression system, thereby providing a low-energy consumption liquid production device that utilizes flue gas.

[0025] The inlet 10 of the flue gas cooler of the low-temperature and medium-pressure CO2 and N2 adsorption system is connected to the flue gas outlet, and the outlet of the flue gas cooler is connected to the first gas-liquid separator 1B, of which the liquid is discharged from the water outlet 13 of the first gas-liquid separator, and the gas is discharged from the gas outlet 12 of the first gas-liquid separator into the compression system 1C, where it is compressed, cooled and dehydrated. The flue gas after compression, cooling and dehydrated enters the drying system 1D through the first tube line for thorough dehydration and drying, and the moisture content of the flue gas leaving the drying system 1D is at the ppm level. The drying system 1D is connected to the rear gas expander system, of which the gas expander system consists of the first expander booster end 1E, the first cooler 1F and the gas expansion end 1G, and the flue gas with a moisture content of ppm level passes through the second tube line 15 and gradually enters the first expander booster end 1E and the first cooler 1D. F enters the gas expansion end 1G, which then enters the low-temperature medium-pressure adsorption unit 1H through the third tube line 18 at the rear. The CO2 in the flue gas is adsorbed and captured using the principle of low-temperature medium-pressure adsorption, and crude carbon dioxide gas with a carbon purity of 85-90% is obtained from the desorbed gas outlet 19 of the low-temperature medium-pressure adsorption unit. Medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 pmm is obtained from the low-temperature medium-pressure filtered gas outlet 20 of the low-temperature medium-pressure adsorption unit. The nitrogen purity of the medium-pressure crude nitrogen is 87-93%, achieving the purpose of carbon and nitrogen separation. The low-temperature medium-pressure filtered gas outlet 20 is further connected to the low-temperature medium-pressure adsorption unit 1H through the fourth tube line 32. A portion of the low-temperature filtered gas enters the low-temperature medium-pressure adsorption unit 1H through the fourth tube line 32 as blown-cooled regeneration gas to blow-cool the adsorbent in the low-temperature medium-pressure adsorption unit 1H.

[0026] The desorbed gas outlet 19 of the low-temperature medium-pressure adsorption device is connected to a CO2 compressor 2A in the energy utilization system to increase the pressure of the crude carbon dioxide. The outlet 141 of the CO2 compressor is connected to a first inlet 21 of a heat utilization device to absorb and utilize the thermal energy of the pressurized crude carbon dioxide gas, which is cooled itself. The first outlet 22 of the heat utilization device is connected to a second cooler 2C to further cool the cooled and pressurized crude carbon dioxide gas in the second cooler 2C, so that the carbon dioxide gas pressurized by the second cooler meets the raw material temperature and pressure requirements of the CO2 low-temperature purification system 101. The outlet 23 of the cooler is connected to a CO2 low-temperature purification system 101, which is used to purify and purify pressurized low-temperature CO2, and can obtain industrial-grade or food-grade carbon dioxide. The CO2 low-temperature purification system 101 is connected to the second inlet 106 of the heat utility through a ninth tubular line 24, and the second outlet 25 of the heat utility is connected to the fourth tubular line 32 on the low-temperature medium-pressure adsorption device 1H. The low-temperature regeneration gas output from the CO2 low-temperature purification system 101 is heated and then introduced into the low-temperature medium-pressure adsorption device 1H for use as heated regeneration gas.

[0027] The low-temperature medium-pressure filtered gas outlet 20 of the low-temperature medium-pressure adsorption unit 1H is connected to the inlet 31 of the low-temperature compressor of the low-temperature filtered gas compression system, and the outlet 33 of the low-temperature compressor is connected to the inlet 34 of the nitrogen liquid system. All or most of the low-temperature filtered gas coming out of the low-temperature medium-pressure adsorption unit 1H is compressed by the low-temperature compression system and then sent to the nitrogen liquid system 100. The nitrogen liquid system 100 is used to further distill and liquefy the low-temperature pressurized filtered gas using the principle of cryogenic distillation to obtain liquid nitrogen products. The nitrogen liquid system 100 is connected to the third inlet 107 of the heat utilization unit by one end of the tenth tube line 26. The third outlet 111 of the utilization device is connected to the inlet 103 of the electric heater by the fifth tube line 27, and the outlet 28 of the electric heater is connected to the drying system 1D by the sixth tube line 102. This allows the waste gas regeneration gas from the nitrogen liquid system 100 to be heated to the required temperature and then introduced into the drying system 1D to heat the regeneration gas. The other end of the nitrogen liquid system 100 is directly connected to the sixth tube line 102 of the drying system 1D by the tenth tube line 26. This allows the waste gas and regeneration gas from the nitrogen liquid system 100 to be directly introduced into the drying system 1D and used as blown cooling gas.

[0028] The CO2 low-temperature purification system 101 includes a third condenser 4F, an evaporator 4D, a liquefier 4E, and a third distillation column 4G, of which the third condenser 4F, the third distillation column 4G, and the evaporator 4D are uniformly arranged in the tower from top to bottom, and the liquefier 4E is installed separately outside the tower. The outlet 23 of the condenser is connected to the inlet end 104 of the evaporator, and the outlet end 45 of the evaporator is connected to the liquefier 4E. The liquefier 4E is connected to the first inlet 108 of the third distillation column through an eighth tube line 46. The first outlet 42 of the distillation column is connected to the inlet 109 of the third condenser, and the outlet of the third condenser is connected to the second inlet 43 of the third distillation column through a seventh tube line 110. A condensate inlet passage 48 and a condensate vapor outlet passage 49 are provided above the third condenser 4F. A ninth tube line 24 is provided at the bottom of the third distillation column 4G and is connected to the second inlet 106 of the heat utility. A fifth tube line 47 is provided at the bottom of the third distillation column 4G and is used to obtain liquid carbon dioxide product.

[0029] The nitrogen liquid device system 100 includes a circulating compression system, a high-temperature gas expander, a heat exchanger 5A, a second gas-liquid separator 5H, a distillation column system, and a subcooler. The circulating compression system is composed of a first compressor 5K1 and a second compressor 5K2. A second expander booster end 5P, a first expansion end 5T, and a second expansion end 5U are respectively installed on the high-temperature gas expander. The subcooler is composed of a first subcooler 5D, a second subcooler 5F, and a third subcooler 5J. The distillation column system is composed of a first distillation column 5B, a first condenser 5C, a second distillation column 5E, and a second condenser 5G. The low-temperature compression The outlet 33 of the heat exchanger is connected to the first passage inlet 34 of the heat exchanger, the first passage outlet 112 of the heat exchanger is connected to the first inlet 60 of the first distillation column, the first outlet 61 of the first distillation column is connected to the first passage inlet 113 of the first supercooler, the first passage outlet 114 of the first supercooler is connected to the first inlet 62 of the first condenser, the first outlet 64 of the first condenser is connected to the first inlet 115 of the second distillation column, one way of the second outlet 50 of the first distillation column is connected to the second inlet 116 of the first condenser and the other way is connected to the third passage inlet 117 of the heat exchanger, and one way of the second outlet 63 of the first condenser is connected to the second inlet 11 of the first distillation column. 8, and the other line is connected to the first inlet 119 of the second gas-liquid separator, the first outlet 65 of the second distillation column is connected to the first passage inlet 120 of the second supercooler, the first passage outlet 121 of the second supercooler is connected to the first inlet 66 of the second condenser, the first outlet 70 of the second condenser is connected to the second passage inlet 122 of the second supercooler, the second passage outlet 71 of the second supercooler is connected to the second passage inlet 123 of the second supercooler, the second passage outlet 72 of the first supercooler is connected to the second passage inlet 84 of the heat exchanger, and the second passage outlet 124 of the heat exchanger is connected to the tenth tube line 26, It is used for regenerating stem 1D, and one way of the second outlet 68 of the second distillation column is connected to the second inlet 160 of the second condenser, and the other way is connected to the fourth passage inlet 67 of the heat exchanger, one way of the second outlet 69 of the second condenser is connected to the second inlet 125 of the second distillation column, and the other way is connected to the second inlet 126 of the second gas-liquid separator, the liquid outlet 80 of the second gas-liquid separator is connected to the first passage inlet 138 of the third supercooler, the first passage outlet 81 of the third supercooler is connected to the inlet 137 of the first throttle valve V4, and the outlet 82 of the first throttle valve V4 is connected to the second passage inlet 127 of the third supercooler,The second passage outlet 83 of the third supercooler is connected to the second passage inlet 84 of the heat exchanger, the first passage outlet 81 of the third supercooler is connected to the liquid nitrogen product passage 85, the liquid nitrogen at the bottom of the second gas-liquid separator 5H is supercooled by the third supercooler 5J and then flows out from the liquid nitrogen product passage 85, the gas outlet 78 of the second gas-liquid separator is connected to the fifth passage inlet 128 of the heat exchanger, the fourth passage outlet 74 of the heat exchanger and the fifth passage outlet 79 of the heat exchanger are connected to the inlet 52 of the first compressor of the cyclic compression system, the third passage outlet 51 of the heat exchanger and the outlet 53 of the first compressor are connected to the second compressor inlet 129 of the cyclic compression system, the outlet 54 of the second compressor and one way are connected to the inlet 55 of the high and low temperature gas expander, and the other way is connected to the eighth passage inlet 130 of the heat exchanger, the eighth passage outlet of the heat exchanger The port 131 is connected to the first expansion end inlet 58 of the high and low temperature gas expander, the first expansion end outlet 59 is connected to the seventh passage inlet 132 of the heat exchanger, the seventh passage outlet 133 of the heat exchanger is connected to the first compressor inlet 52, the booster end outlet 56 of the high and low temperature gas expander is connected to the sixth passage inlet 134 of the heat exchanger, the sixth passage outlet 1 of the heat exchanger is connected to the second expansion end inlet 75 of the high and low temperature gas expander, the second expansion end outlet 76 is connected to the fourth inlet 139 of the second gas-liquid separator, the sixth passage outlet 2 of the heat exchanger is connected to the inlet 77 of the second throttle valve V3, and the outlet 140 of the second throttle valve V3 is connected to the third inlet 135 of the second gas-liquid separator, and the low temperature nitrogen-containing gas obtained from the low temperature compressor is further purified and liquefied using the principle of cryogenic distillation to obtain liquid nitrogen product.

[0030] A method for using a flue gas-utilizing low energy consumption liquid production device, the method comprising the steps of: 1) Flue gas pretreatment: Flue gas is compressed, cooled, dehydrated, and dried to reduce the moisture content of the treated flue gas to a level of <1 ppm. 2) Rough gas separation of CO2 and N2: The gas in step 1) is passed through a gas expander system to obtain crude carbon dioxide gas with a carbon purity of 85-90% and medium-pressure crude nitrogen with a carbon dioxide concentration of less than 1 ppm, and the nitrogen purity of the medium-pressure crude nitrogen is 87-93%. 3) Purification of liquid CO2 products obtained by liquefaction: In step 2), the crude carbon dioxide having a carbon concentration of 85-90% is passed through a CO2 low-temperature purification system 101 to obtain a liquid CO2 product; 4) Purification of liquid N2 products obtained by liquefaction: The medium pressure nitrogen in step 2) having a carbon dioxide concentration of less than 1 ppm is passed through a nitrogen liquid system 100 to obtain a liquid N2 product.

[0031] In the specific method of step 1, the discharged normal temperature and pressure flue gas enters the flue gas cooler inlet 10, and the cooling medium cools the flue gas. The cooled flue gas passes through the first gas-liquid separator 1B to remove condensed water in the flue gas, and the water is discharged through the water outlet 13 of the first gas-liquid separator. The cooled flue gas passes through the gas outlet 12 of the first gas-liquid separator and enters the compression system 1C for compression, cooling and dehydration. The pressurized medium-pressure flue gas is entered into the first tube line 14 of the drying system 1D for further dehydration and drying, so that the moisture content of the medium-pressure flue gas exiting the drying system 1D is less than 1 ppm.

[0032] The specific method of step 2 is as follows: the gas that is pressurized after entering the booster end 1E of the first expander of the gas expander system is further cooled by the first cooler 1F and then entered into the gas expansion end 1G for expansion and cooling; the expanded low-temperature and medium-pressure gas enters the low-temperature and medium-pressure adsorption device 1H to adsorb and capture CO2 in the low-temperature and medium-pressure flue gas using the principle of low-temperature and medium-pressure adsorption; crude carbon dioxide gas with a carbon purity of 85-90% is obtained from the desorbed gas outlet 19 of the low-temperature and medium-pressure adsorption device; and medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 ppm is obtained from the low-temperature and medium-pressure filtered gas outlet 20 of the low-temperature and medium-pressure adsorption device, with a nitrogen purity of 87-93%, thereby achieving the purpose of carbon-nitrogen separation. The low-temperature and medium-pressure adsorption device can switch between adsorption, desorption, regeneration and blow-cooling through valves and tubing lines.

[0033] The specific steps for obtaining liquid CO2 from step 3 are as follows: the desorbed gas from the desorbed gas outlet 19 of the low-temperature medium-pressure adsorption device enters the CO2 compressor 2A of the energy utilization system, where it is pressurized relative to the crude carbon dioxide gas; the pressurized high-temperature, high-pressure gas enters the heat exchanger 2B, where it absorbs and utilizes the heat of the pressurized crude carbon dioxide gas; after being cooled, it enters the secondary cooler 2C, where it further cools the cooled and pressurized crude carbon dioxide; and the pressurized carbon dioxide gas in the secondary cooler 2C meets the raw material temperature and pressure requirements of the CO2 low-temperature purification system 101. The raw material temperature is 20-30°C and the pressure is 2.0-2.5MPa, and then it enters the CO2 low-temperature purification system 101 to purify and purify the pressurized low-temperature CO2, obtaining industrial-grade or food-grade carbon dioxide. The low-temperature regeneration gas extracted from the ninth tube line 24 of the CO2 low-temperature purification system 101 can be reheated using the heat utility 2B, and the heated regeneration gas enters the low-temperature medium-pressure adsorption device 1H to heat and regenerate the adsorbent that needs to be regenerated, eliminating the need to rely on external energy for regeneration of the low-temperature medium-pressure adsorption device.

[0034] In the specific step of obtaining liquid N2 from step 4, all or most of the crude nitrogen gas having a carbon dioxide concentration of less than 1 ppm output from the low-temperature medium-pressure adsorption unit 1H is subjected to low-temperature filtration, and the filtered gas is compressed in the low-temperature compressor 3A of the low-temperature compression system and then directly input into the nitrogen liquid system 100. When blow-cooling is required to regenerate the adsorbent in the low-temperature medium-pressure adsorption unit 1H, part of the low-temperature filtered gas is input into the low-temperature medium-pressure adsorption unit 1H through the fourth tube line 32 as regeneration gas for blow-cooling to blow-cool the adsorbent in the low-temperature medium-pressure adsorption unit 1H. The pressurized filtered gas is input into the nitrogen liquid system 100 for distillation and liquefaction. The waste gas regeneration gas output from the tenth tube line 26 of the nitrogen liquid system 100 is input into the heat utility 2B to be heated, and then further input into the electric heater 2E to be heated to the required temperature before being input into the second inlet 136 of the drying system to be used as heated regeneration gas. The waste gas regeneration gas output from the tenth tube line 26 of the nitrogen liquid system 100 is also directly input into the inlet 136 of the drying system to be used as blow-cooling gas.

[0035] The specific CO2 gas purification method used in the CO2 low-temperature purification system 101 is as follows: the crude carbon dioxide entering the CO2 low-temperature purification system 101 first enters the evaporator 4D to evaporate the liquid at the bottom of the third distillation column 4G, and after being cooled, enters the liquefier 4E to be cooled to saturation temperature, and then enters the middle of the third distillation column 4G to participate in distillation. In the third condenser 4F, the gas exiting the top of the third distillation column 4G is condensed and used as the reflux liquid at the top of the third distillation column to participate in distillation. The condensate enters the third condenser 4F via the condensate line 48, and the condensate, which provides cooling power, is heated and vaporized to obtain liquid carbon dioxide product at the bottom of the third distillation column 4G. The liquid carbon dioxide product is output from the fifth tube line 47 at the bottom of the third distillation column 4G, and the gas extracted from the ninth tube line 24 at the middle and upper part of the third distillation column 4G enters the heat utility 2B to be heated.

[0036] The specific N2 gas purification method in the nitrogen liquid system 100 is as follows: the gas entering the nitrogen liquid system is supercooled to a saturated state by the heat exchanger 5A, and then enters the distillation column system. The distillation column system has a double tower structure. Part of the medium-pressure nitrogen exiting the top of the first distillation column 5B is condensed by the first condenser 5C, and the liquid nitrogen part is refluxed to the top of the first distillation column 5B, and part enters the second gas-liquid separator 5H. The liquid extracted from the bottom of the first distillation column 5B is supercooled through the first supercooler 5D, and then enters the first condenser 5C as cooling capacity. After being heated, it exits the first condenser 5C and enters the bottom of the second distillation column 5E to participate in distillation. A portion of the low-pressure nitrogen exiting the top of the second distillation column 5E is condensed by the second condenser 5G, and the liquid nitrogen portion is refluxed to the top of the second distillation column 5E. A portion of the medium-pressure nitrogen gas exiting the top of the first distillation column 5B is reheated in the heat exchanger 5A and then enters the second compressor 5K2 of the cyclic compression system to be compressed. Another portion of the low-pressure nitrogen exiting the top of the second distillation column 5E is reheated by the heat exchanger 5A and then enters the cyclic compression system. The gas flows into the first compressor 5K1 and the second compressor 5K2 of the system and is compressed successively. The gas compressed by the second compressor 5K2 is boosted in pressure at the second expander booster end 5P of the high and low temperature gas expander. After boosting, the gas flows into the heat exchanger 5A and is cooled. Some of the gas is extracted from the middle of the heat exchanger 5A and expanded at the second expansion end 5U. The expanded fluid flows into the second gas-liquid separator 5H. The remaining gas is extracted from the bottom of the heat exchanger 5A and passes through the second throttle valve V3 to the second gas-liquid separator 5H. The other gas flows directly into the heat exchanger 5A and then flows into the heat exchanger 5A. The gas is extracted from the upper middle portion of the refrigerant passage and enters the first expansion end 5T for expansion. The expanded gas is then reheated in the heat exchanger 5A, and then enters the first compressor 5K1 and the second compressor 5K2 of the circulating compression system for sequential compression. The gas is then separated into gas and liquid in the second gas-liquid separator 5H. The liquid then flows out of the liquid outlet 80 of the second gas-liquid separator and is supercooled by the third supercooler 5J. Some of the liquid is adjusted in flow rate by the first throttle valve V4 and enters the third supercooler 5J for reheating. The reheated fluid enters the heat exchanger 5A for further reheating.The waste gas is discharged from the nitrogen liquid system 100, and the remaining liquid is extracted from the liquid nitrogen product passage 85 and used as high-purity liquid nitrogen product. The gas in the second gas-liquid separator 5H flows out from the gas outlet 78 of the second gas-liquid separator, is reheated by the heat exchanger 5A, and enters the first compressor 5K1 and the second compressor 5K2 of the cyclic compression system to be compressed in succession. The liquid from the bottom of the second distillation column 5E is subcooled by the second subcooler 5F and then enters the evaporation side of the second condenser 5G to be evaporated. The evaporated gas is reheated by the second subcooler 5F and the first subcooler 5D in succession. The reheated fluid enters the heat exchanger 5A for further reheating and is discharged from the nitrogen liquid system 100 as waste gas.

[0037] The adsorbents used in the low-temperature medium-pressure adsorption device 1H are mainly molecular sieves, silica gel, and activated carbon. Two units are installed, but they can be used alone or simultaneously. The drying system 1D consists of two dryers arranged in parallel, and the two dryers can be used alone or simultaneously.

[0038] The outlet pressure of the compression system 1C described in the present invention is coupled with the gas expansion system, low-temperature compressor 3A, and CO2 compressor 2A. The outlet pressure of the compression system 1C not only needs to consider the energy consumption of the compression system 1C itself, the low-temperature compressor 3A, and the CO2 compressor 2A, but also the cooling capacity of the gas expander system. It also needs to consider whether the pressure at the expansion outlet of the gas expansion end 1G satisfies the efficient adsorption of the low-temperature medium-pressure adsorption device 1H. It also needs to consider whether the temperature at the expansion outlet of the gas expansion end 1G can effectively adsorb the expanded gas from the gas expansion end 1G without freezing. It also needs to consider the input cost, drying effect, and adsorption effect of the drying system 1D and the low-temperature medium-pressure adsorption device 1H. The adsorbents used in the low-temperature medium-pressure adsorption device 1H are mainly molecular sieves, silica gel, and activated carbon. Two units are installed, but they can be used alone or simultaneously. The drying system 1D consists of two dryers arranged in parallel, and the two dryers can be used alone or simultaneously.

[0039] The present invention uses an energy utilization system to effectively utilize the compression heat of the CO2 compressor 2A, and the heated regeneration gas required for the low-temperature medium-pressure adsorption device 1H and drying system 1D can be obtained by reheating it in the energy utilization device 2B.This avoids relying on external thermal energy during the regeneration of the low-temperature medium-pressure adsorption device 1H, and reduces the heating power of the electric heater 2E, resulting in significant savings in overall energy consumption.

[0040] Example 1 As shown in Figure 1, normal temperature and pressure flue gas (temperature about 50°C, pressure about 0.1 MPaA, molar composition about 12% CO2, 73% N2, 8% H2O, 6% O2, 0.984% Ar, 100 ppm CO, 50 ppm NO2, 10 ppm SO2) that meets the ultra-low emission standard enters the cooler inlet 10, where the flue gas is cooled to about 6°C by the cooling medium. After cooling, the flue gas passes through gas-liquid separator 1B to remove condensed water in the flue gas, and the water is separated into gas and liquid. The cooled flue gas is discharged from the water outlet 13 of the separator and enters the compression system 1C from the outlet 12 of the gas-liquid separator for compression, cooling and dehydration. The saturated flue gas with a pressure of about 0.8 MPaA and a temperature of about 6°C enters the first tube line 14 of the drying system 1D for further dehydration and drying. After the moisture content of the flue gas leaving the drying system 1D becomes 1 ppm or less, it enters the first expander booster end of the gas expander system and is increased to about 1.6 MPaA. The low-temperature / medium-pressure adsorption unit 1H is then compressed and further cooled to about 6°C in the first cooler 1F before being expanded in the gas expansion unit 1G. The low-temperature / medium-pressure gas, with a pressure of about 0.41 MPaA and a temperature of about -81°C, enters the low-temperature / medium-pressure adsorption unit 1H, where it uses the principle of low-temperature / medium-pressure adsorption to adsorb and capture CO2 from the low-temperature / medium-pressure flue gas. The low-temperature / medium-pressure filtered gas outlet 20 of the low-temperature / medium-pressure adsorption unit produces low-temperature / medium-pressure nitrogen gas with a relatively high nitrogen purity and a carbon dioxide content of less than 1 ppm, at a pressure of about 0.4 MPa, thereby achieving the purpose of carbon-nitrogen separation. The low-temperature / medium-pressure adsorption unit 1H can switch between adsorption, desorption, regeneration and blow-cooling through valves and tubing. The adsorbents used in the low-temperature / medium-pressure adsorption unit 1H are mainly composed of molecular sieves, silica gel and activated carbon. When desorption is performed in the low-temperature / medium-pressure adsorption unit 1H, crude carbon dioxide with a carbon purity of 85-90% is obtained from the desorption gas outlet 19 of the low-temperature / medium-pressure adsorption unit.

[0041] The desorbed gas (temperature: about 10°C, pressure: about 0.11 MPaA, molar composition: about 92% CO2, 8% N2, 50 ppm NO2, 10 ppm SO2) coming out of the desorbed gas outlet 19 of the low-temperature medium-pressure adsorption device enters the CO2 compressor 2A of the energy utilization system, where it is pressurized to about 2.3 MPa. When the outlet temperature reaches about 100°C, it is put into the heat utilization device 2B for heat exchange, absorbing and utilizing the heat of the pressurized crude carbon dioxide gas. After it is cooled, it enters the second cooler 2C, where it further cools the cooled and pressurized crude carbon dioxide. The pressurized carbon dioxide gas in the second cooler 2C is cooled to about 25°C, so as to meet the raw material temperature and pressure conditions of the CO2 low-temperature purification system. Then, The pressurized low-temperature CO2 enters the CO2 low-temperature purification system to purify and purify it, obtaining industrial- or food-grade carbon dioxide. When the low-temperature medium-pressure adsorption unit 1H is heated, the low-temperature regeneration gas (temperature approximately -12.7°C, pressure approximately 2.3 MPaA, molar composition approximately 98.5% CO2, 1.5% N2, 20 ppm CO, 2 ppm NO2, 1 ppm SO2) extracted from the ninth tube line 24 of the CO2 low-temperature purification system can be reheated to approximately 90°C using the heat converter 2B. The heated regeneration gas enters the low-temperature medium-pressure adsorption unit 1H to heat and regenerate the adsorbent that needs to be regenerated, thereby avoiding the reliance on external thermal energy for the regeneration of the low-temperature medium-pressure adsorption unit 1H.

[0042] All or most of the medium pressure crude nitrogen gas (temperature about -87°C, pressure about 0.4MPaA, molar composition 92% N2, 7.5% O2, 1.4% Ar, 120 ppm CO, 1 ppm CO2) with a carbon dioxide concentration of less than 1 ppm coming out of the low temperature medium pressure adsorption unit 1H is low temperature filtered, and the filtered gas is fed to the low temperature compressor 3A of the low temperature compression system and compressed to about 0.9 MPaA and -10°C, and then directly fed into the nitrogen liquid system. When blow-cooling is required for the regeneration of the adsorbent in the low temperature medium pressure adsorption unit 1H, part of the low temperature filtered gas is fed into the low temperature medium pressure adsorption unit 1H through the fourth tube line 32 as regeneration gas for blow-cooling, and then fed into the low temperature medium pressure adsorption unit 1H. The adsorbent in step 1H is blown and cooled, and the pressurized filtered gas is introduced into the nitrogen liquid system for distillation and liquefaction. When heating is required for drying system 1D, the waste gas regeneration gas coming out of the tenth tube line 26 of the nitrogen liquid system is introduced into the heat utilization device 2B to be heated to 90°C, and then into the electric heater 2E to be heated to about 170°C, and then into the second inlet 136 of the drying system to be used for heating the regeneration gas. When blow-cooling is required for drying system 1D, the atmospheric waste gas regeneration gas coming out of the tenth tube line 26 of the nitrogen liquid system is directly introduced into the inlet 136 of the drying system to be used as blow-cooling gas.

[0043] As shown in Figure 2, the gas (pressure about 0.9 MPaA, temperature about -10°C) entering the nitrogen liquid system is subcooled to saturation by heat exchanger 5A, then enters the distillation column system and distilled. Part of the medium pressure nitrogen exiting the top of distillation column 5B is condensed by first condenser 5C, and the liquid nitrogen part is refluxed to the top of first distillation column 5B, and part enters second gas-liquid separator 5H. The liquid extracted from the bottom of first distillation column 5B is subcooled through first subcooler 5D and then enters first condenser 5C to be used as cooling capacity and heating. After that, it leaves the first condenser 5C and enters the bottom of the second distillation column 5E to participate in distillation. Part of the low-pressure nitrogen exiting the top of the second distillation column 5E is condensed by the second condenser 5G, and the liquid nitrogen part is refluxed to the top of the second distillation column 5E. Part of it enters the second gas-liquid separator 5H. Another part of the medium-pressure nitrogen gas exiting the top of the first distillation column 5B is reheated in the heat exchanger 5A and then enters the second compressor 5K2 of the cyclic compression system and compressed to about 2.5 MPaA. Another part of the low-pressure nitrogen exiting the top of the second distillation column 5E is reheated by the heat exchanger 5A. The gas flows into the first compressor 5K1 and the second compressor 5K2 of the circulating compression system and is compressed to about 2.5 MPaA successively. The gas compressed by the second compressor 5K2 is boosted into the second expander booster end 5P of the high and low temperature gas expander. After boosting, the gas enters the heat exchanger 5A and is cooled. Some of the gas is extracted from the middle of the heat exchanger 5A and enters the second expansion end 5U and is expanded to about 0.39 MPaA. The expanded fluid enters the second gas-liquid separator 5H. The remaining gas is extracted from the bottom of the heat exchanger 5A and passes through the second throttle valve V3 to be sent to the second gas-liquid separator. The other gas flows directly into the heat exchanger 5A and is extracted from the upper middle part of the heat exchanger 5A and enters the first expansion end 5T for expansion. The expanded gas then enters the heat exchanger 5A again to be reheated, and then enters the first compressor 5K1 and the second compressor 5K2 of the circulating compression system to be compressed to about 2.5 MPaA. The fluid undergoes gas-liquid separation in the second gas-liquid separator 5H, and the liquid flows out of the liquid outlet of the second gas-liquid separator 5H and is subcooled in the third subcooler 5J. Some of the liquid is then cooled to about 0.5 MPaA by the first throttle valve V4.The flow rate is adjusted to 13 MPaA and reheated in the third subcooler 5J. The reheated fluid enters the heat exchanger 5A for further reheating and is discharged from the nitrogen liquid system as waste gas. The remaining liquid is extracted from the liquid nitrogen product line 85 and used as high-purity liquid nitrogen product. The gas in the gas-liquid separator 5H flows out from the gas outlet 12 of the gas-liquid separator and is reheated in the heat exchanger 5A. It then enters the first compressor 5K1 and the second compressor 5K2 of the cyclic compression system and is compressed to 2.5 MPaA. The liquid from the bottom of the second distillation column 5E is subcooled in the second subcooler 5F and enters the evaporation side of the second condenser 5G for evaporation. The evaporated gas is reheated in the second subcooler 5F and the first subcooler 5D, respectively. The reheated fluid enters the heat exchanger 5A for further reheating and is discharged from the nitrogen liquid system as waste gas.

[0044] As shown in Figure 3, the crude CO2 (temperature approximately 25°C, pressure approximately 2.3 MPaA, molar composition approximately 92% CO2, 8% N2, 50 ppm NO2, 10 ppm SO2) entering the CO2 low-temperature purification system is evaporated from the liquid at the bottom of distillation column 4G by evaporator 4D, which is cooled to approximately -10°C and then enters liquefier 4E to be cooled to saturation at approximately -17°C, before entering the middle of third distillation column 4G to participate in distillation. In third cooler 4F, the gas exiting the top of distillation column 4G is condensed and used as reflux liquid for the top of the distillation column to participate in distillation. It enters third condenser 4F via condensate inlet 48, where the condensate, which provides cooling power, is heated and vaporized to obtain industrial-grade liquid carbon dioxide product at the bottom of distillation column 4G. Regeneration gas is extracted from the ninth tube line 24 of distillation column 4G.

[0045] The specific embodiments described herein are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Those skilled in the art may make modifications or variations to the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or variations made by those skilled in the art without departing from the spirit and technical ideas described in the present invention still fall within the scope of the claims of the present invention.

Claims

1. The low-temperature and medium-pressure CO2 and N2 adsorption system includes an energy utilization system, a low-temperature filtered gas low-temperature compression system, a CO2 low-temperature purification system (101) and a nitrogen liquid device system (100), which are connected by mutual tubing lines and valves. The low-temperature and medium-pressure CO2 and N2 adsorption system includes a flue gas cooler (1A), a first gas-liquid separator (1B), a compression system (1C), a drying system (1D), a gas expansion system and a low-temperature and medium-pressure adsorption device (1H). ... The energy utilization system includes an electric heater (2E), a CO2 compressor (2A), a heat utilization unit (2B), and a secondary cooler (2C), and the CO2 compressor (2A), heat utilization unit (2B), and secondary cooler (2C) of the energy utilization system are used to compress, utilize heat, and cool the desorbed gas obtained through the low-temperature adsorption separation by the low-temperature medium-pressure adsorption device (1H) of the low-temperature medium-pressure adsorption system for CO2 and N2. The system includes a low-temperature compressor (3A), which is used to apply low-temperature pressure to the low-temperature medium-pressure filtered gas obtained from the low-temperature medium-pressure filtered gas outlet (20) of the low-temperature medium-pressure adsorption device (1H), the CO2 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 CO2 product, and the nitrogen liquid device system (100) is used to obtain a liquid nitrogen product through distillation and liquefaction of the medium-pressure gas coming out of the low-temperature compression system, The desorbed gas outlet (19) of the medium-pressure adsorption device is connected to a CO2 compressor (2A) in the energy utilization system to increase the pressure of the crude carbon dioxide, and the CO2 compressor (2A) is sequentially connected to a heat utilization device (2B), a second cooler (2C), and a CO2 low-temperature purification system (101), and low-temperature regeneration gas required for regenerating the adsorbent in the low-temperature medium-pressure adsorption device (1H) is extracted from the ninth tube line (24) of the CO2 low-temperature purification system (101).

2. One end of the flue gas cooler (1A) of the CO2 and N2 low-temperature and medium-pressure adsorption system is connected to the flue gas outlet, and the other end is connected to the first gas-liquid separator (1B). The liquid in the first gas-liquid separator (1B) is discharged from the water outlet (13) of the first gas-liquid separator. The gas enters the compression system (1C) through the gas outlet (12) of the first gas-liquid separator, where it is compressed, cooled, and dehydrated. The compressed, cooled, and dehydrated flue gas enters the drying system (1D) through the first tube line (14) for thorough dehydration. The flue gas from the drying system (1D) is dried by water, and the moisture content of the flue gas is at the ppm level. The drying system (1D) is connected to a downstream gas expander system, which is composed of a first expander booster end (1E), a first cooler (1F), and a gas expansion end (1G). The flue gas with moisture content at the ppm level gradually enters the first expander booster end (1E), the first cooler (1F), and the gas expansion end (1G) through the second tube line (15). The low-temperature medium-pressure adsorption device (1H) absorbs and captures CO2 in the flue gas, and obtains crude carbon dioxide gas with a carbon purity of 85-90% from the desorbed gas outlet (19) of the low-temperature medium-pressure adsorption device. The low-temperature medium-pressure adsorption device also obtains medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 pmm from 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 85-90%. 7-93%, achieving the purpose of carbon and nitrogen separation; the low-temperature medium-pressure filtered gas outlet (20) is further connected to a low-temperature medium-pressure adsorption unit (1H) through a fourth tubular line (32); a portion of the low-temperature filtered gas enters the low-temperature medium-pressure adsorption unit (1H) through the fourth tubular line (32) as a gas for blowing and cooling the regeneration gas, thereby blowing and cooling the adsorbent in the low-temperature medium-pressure adsorption unit (1H).

3. 1. The low-energy liquid production device using flue gas as claimed in claim 2, wherein the second cooler (2C) further cools the cooled and pressurized crude carbon dioxide so that the carbon dioxide gas pressurized by the second cooler (2C) meets the raw material temperature and pressure requirements of the CO2 low-temperature purification system (101), the CO2 low-temperature purification system (101) is used to purify and purify the pressurized low-temperature CO2, and industrial-grade or food-grade carbon dioxide can be obtained, the CO2 low-temperature purification system (101) is connected to a heat utility (2B) through a ninth tubing line (24), and the heat utility (2B) is connected to a fourth tubing line (32) on the low-temperature medium-pressure adsorption device (1H), and the low-temperature regeneration gas from the CO2 low-temperature purification system (101) is heated and then introduced into the low-temperature medium-pressure adsorption device (1H) to be used as heated regeneration gas.

4. The downstream side of the low-temperature medium-pressure filtered gas outlet (20) of the low-temperature medium-pressure adsorption device is gradually connected to the low-temperature compressor (3A) of the low-temperature filtered gas compression system and the nitrogen liquid system (100). All or most of the low-temperature filtered gas is compressed by the low-temperature compression system and then sent to the nitrogen liquid system (100). The nitrogen liquid system (100) is used to further distill and liquefy the low-temperature pressurized filtered gas to obtain liquid nitrogen products. A tenth tube line (26) is installed downstream of the tenth tube line (26). The downstream side of the tenth tube line (26) is divided into two paths, one of which is gradually connected to a heat utilization unit (2B) and an electric heater.

3. The device for producing liquids with low energy consumption by utilizing flue gas as claimed in claim 2, characterized in that the tenth tube line (26) is connected to a heater (2E), the electric heater (2E) is connected to a sixth tube line (102), and the sixth tube line (102) is connected to a drying system (1D), so that the waste gas and regeneration gas from the nitrogen liquid system (100) are heated to a required temperature and then fed into the drying system (1D) to be heated as regeneration gas; the other side of the tenth tube line (26) is directly connected to the sixth tube line (102), so that the waste gas and regeneration gas from the nitrogen liquid system (100) are fed directly into the drying system (1D) to be used as blow-cooling gas.

5. The CO2 low-temperature purification system (101) includes a third condenser (4F), an evaporator (4D), a liquefier (4E), and a third distillation column (4G), of which the third condenser (4F) is installed above the third distillation column (4G) and the evaporator (4D) is installed below it, and the liquefier (4E) is installed separately from the tower, the second cooler (2C) is connected to the evaporator (4D), the evaporator (4D) is connected to the liquefier (4E), the liquefier (4E) is connected to the third distillation column (4G) through an eighth tube line (46), and the third distillation column (4G) is connected to the third condenser (4F), The third condenser (4F) is connected to the third distillation column (4G) through a seventh tube line (110) to form a circuit, and a condensate inlet passage (48) and a condensate vapor outlet passage (49) are provided above the third condenser (4F), a ninth tube line (24) is provided below the third distillation column (4G) to connect to the heat utilization device (2B), and a fifth tube line (47) is provided at the bottom of the third distillation column (4G) to obtain a liquid carbon dioxide product.

6. The nitrogen liquid device system (100) comprises a circulating compression system, a high-temperature gas expander, a heat exchanger (5A), a second gas-liquid separator (5H), a distillation column system and a supercooler, of which the circulating compression system comprises a first compressor (5K1) and a second compressor (5K2), and the high-temperature gas expander is provided with a second expander booster end (5P), a first expansion end (5T) and a second expansion end (5U), respectively; the supercooler comprises a first supercooler (5D), a second supercooler (5F) and a third supercooler (5J); and the distillation column system comprises a first distillation column (5B) and a third supercooler (5C). The system comprises two distillation columns (5E), of which a first condenser (5C) is installed above the second distillation column (5B), and a second condenser (5G) is installed above the second distillation column (5E). The low-temperature compressor (3A) is sequentially connected to the heat exchanger (5A) and the first distillation column (5B). Two branch tube lines are installed on the first distillation column (5B), of which the first branch tube line of the first distillation column (5B) is sequentially connected to the first supercooler (5D), the first condenser (5C), the second distillation column (5E), the second supercooler (5F), and the second condenser (5G). The upper part of the second condenser (5G) is connected to the chute. The first condenser (5C) is also provided with two branch tube lines, the first branch tube line of which is connected to the first distillation column (5B), the first subcooler (5F), the first subcooler (5D), and the heat exchanger (5A) through the tube lines. The heat exchanger (5A) is connected to the tenth tube line (26) and is used for regenerating the drying system (1D). The second branch tube line of the first distillation column (5B) is directly connected to the first condenser (5C) and the heat exchanger (5A), respectively. The first condenser (5C) is also provided with two branch tube lines, the first branch tube line of which is connected to the first distillation column (5B), and the second branch tube line of the first condenser (5C) is The second distillation column (5E) is also provided with two branch tube lines, the first branch tube line of which is connected to the second condenser (5G), and the second branch tube line of which is connected to the heat exchanger (5A). The second condenser (5G) is also provided with two branch tube lines, the first branch tube line of which is connected to the second distillation column (5E), and the second branch tube line of which is connected to the second gas-liquid separator (5H) and the third subcooler (5J).One end of the third supercooler (5J) is connected to the liquid nitrogen product passage, and the other end is connected to the heat exchanger (5A) through the first throttle valve (V4) and the third supercooler (5J). The second gas-liquid separator (5H) is connected to the heat exchanger (5A), and the heat exchanger (5A) is connected to the first compressor (5K1) and the second compressor (5K2). The second compressor (5K2) is provided with two branch tube lines, and the first branch tube line of the second compressor (5K2) passes through the high and low temperature gas expander (5P), the heat exchanger (5A), the second expansion end (5U), and finally to the second expansion end (5U).

5. The low-energy-consumption liquid producing device using flue gas as claimed in claim 4, characterized in that the second branch tube line of the second compressor (5K2) is sequentially connected to the heat exchanger (5A), the first expansion end (5T), the heat exchanger (5A), and finally connected to the first compressor (5K1) through the heat exchanger (5A) to form a circulation, the heat exchanger (5A) is directly connected to the second gas-liquid separator (5H), and a second throttle valve (V3) is installed on the connecting tube line, so that the low-temperature nitrogen-containing gas obtained from the low-temperature compressor is further purified and liquefied to obtain liquid nitrogen product.

7. 1) a flue gas pretreatment stage, in which flue gas is compressed, cooled, dewatered and dried, so that the moisture content of the flue gas after treatment is less than 1 ppm; 2) a crude CO2 and N2 gas separation step in which the gas from step 1) is passed through a gas expander system to obtain crude carbon dioxide gas having a carbon purity of 85-90% and medium-pressure crude nitrogen gas having a carbon dioxide concentration of less than 1 ppm, the nitrogen purity of the medium-pressure crude nitrogen gas being 87-93%; 3) purification of the liquid CO2 product obtained by liquefaction, in which the crude CO2 having a carbon concentration of 85-90% in step 2) is passed through a CO2 low-temperature purification system to obtain a liquid CO2 product; and 4) Purifying the liquid N2 product obtained by liquefaction by passing the medium pressure nitrogen in step 2) having a carbon dioxide concentration of less than 1 ppm through a nitrogen liquid system to obtain a liquid N2 product; A method for using the low energy consumption liquid production device using flue gas according to any one of claims 1 to 6.

8. 10. The method for using a flue gas-utilizing low-energy-consumption liquid production device according to claim 7, wherein the specific method of step 1 is as follows: the discharged normal-temperature normal-pressure flue gas enters the flue gas cooler inlet (10), and the cooling medium cools the flue gas; the cooled flue gas passes through a first gas-liquid separator (1B) to remove condensed water in the flue gas, and the water is discharged through a water outlet (13) of the first gas-liquid separator; the cooled flue gas passes through a gas outlet (12) of the first gas-liquid separator to enter a compression system (1C) for compression, cooling and water removal; the pressurized medium-pressure flue gas passes through a first tubular line (14) to enter a drying system (1D) for further water removal and drying, so that the water content of the medium-pressure flue gas exiting the drying system (1D) is less than 1 ppm.

9. As a specific method of the step 2, the gas that is pressurized after entering the pressure booster end (1E) of the first expander of the gas expander system is further cooled by the first cooler (1F), and then enters the gas expansion end (1G) for expansion and cooling. The expanded low-temperature medium-pressure gas enters the low-temperature medium-pressure adsorption device (1H), which adsorbs and captures CO2 in the low-temperature medium-pressure flue gas, and produces crude carbon dioxide with a carbon purity of 85-90% from the desorption gas outlet of the low-temperature medium-pressure adsorption device (1H).

10. The method for using a flue gas-utilizing, low-energy consumption liquid production device according to claim 7, wherein the low-temperature, medium-pressure adsorption device (1H) is used to obtain a low-temperature, medium-pressure filtered gas outlet (20) of the low-temperature, medium-pressure adsorption device (1H) from which a medium-pressure crude nitrogen gas having a carbon dioxide concentration of less than 1 ppm is obtained, and the nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%, thereby achieving the purpose of carbon-nitrogen separation. The low-temperature, medium-pressure adsorption device (1H) is used to switch between adsorption, desorption, regeneration and blow-cooling through valves and tubing lines.

10. The specific steps for obtaining liquid CO2 from step 3 are as follows: the desorbed gas from the desorbed gas outlet (19) of the low-temperature medium-pressure adsorption device enters the CO2 compressor (2A) of the energy utilization system to increase the pressure of the crude carbon dioxide gas; the pressurized high-temperature high-pressure gas is sent to the heat exchanger (2B) for heat exchange, absorbing and utilizing the heat of the pressurized crude carbon dioxide gas; and after being cooled, it enters the second cooler (2C) to further cool the cooled and pressurized crude carbon dioxide; the pressurized carbon dioxide gas in the second cooler (2C) meets the raw material temperature and pressure requirements of the CO2 low-temperature purification system (101), where the raw material temperature is 20-30°C and the pressure is 2.

10. The low-temperature CO2 purification system (101) extracts low-temperature CO2 from the ninth tube line (24) of the low-temperature CO2 purification system (101), and the extracted low-temperature regeneration gas can be reheated using a heat converter (2B). The heated regeneration gas can be reheated into the low-temperature medium-pressure adsorption device (1H) to heat and regenerate the adsorbent that needs to be regenerated. This eliminates the need to rely on external energy sources for the regeneration of the low-temperature medium-pressure adsorption device (1H).

11. In the specific step of obtaining liquid N2 from step 4, all or most of the crude nitrogen gas having a carbon dioxide concentration of less than 1 ppm output from the low-temperature medium pressure adsorption unit (1H) is subjected to low-temperature filtration, and the filtered gas is compressed in the low-temperature compressor (3A) of the low-temperature compression system and then directly introduced into the nitrogen liquid system (100). When blow-cooling is required for the regeneration of the adsorbent in the low-temperature medium pressure adsorption unit (1H), a part of the low-temperature filtered gas is introduced into the low-temperature medium pressure adsorption unit (1H) through the fourth tube line (32) as a gas for blow-cooling the regeneration gas, thereby blow-cooling the adsorbent in the low-temperature medium pressure adsorption unit (1H). The compressed filtered gas is then introduced into the nitrogen liquid system (100). The waste gas regeneration gas from the nitrogen liquid system (100) is introduced into the heat utilization device (2B) through the tenth tube line (26) to be heated, and then introduced into the electric heater (2E) to be heated to a required temperature, and then introduced into the second inlet of the drying system (1D) to be used as heated regeneration gas; and the waste gas regeneration gas from the nitrogen liquid system (100) is also introduced into the second inlet of the drying system through the tenth tube line (26) directly to be used as blown cooling gas.

12. The specific CO2 gas purification method in the CO2 low-temperature purification system (101) is as follows: the crude carbon dioxide entering the CO2 low-temperature purification system (101) first enters the evaporator (4D) to evaporate the liquid at the bottom of the third distillation column (4G), and after being cooled, it further enters the liquefier (4E) to be cooled to a saturation temperature, and then enters the middle of the third distillation column (4G) to participate in distillation; the gas exiting the top of the third distillation column (4G) is condensed in the third cooler (4F) and then evaporated as the reflux liquid at the top of the third distillation column (4G). The gas extracted from the third distillation column (4G) through the fifth tube line (47) is vaporized, and the gas extracted from the ninth tube line (24) at the middle and upper part of the third distillation column (4G) is introduced into the heat utilization device (2B) for heating.

13. The specific method of purifying N2 gas in the nitrogen liquid system (100) is as follows: the gas entering the nitrogen liquid system (100) is supercooled to a saturated state by a heat exchanger (5A), and then enters a distillation column system. The distillation column system has a double tower structure, and a portion of the medium pressure nitrogen exiting the top of the first distillation column (5B) is condensed by a first condenser (5C), and the liquid nitrogen portion is returned to the top of the first distillation column (5B), and a portion enters a second gas-liquid separator (5H), and the liquid extracted from the bottom of the first distillation column (5B) is supercooled through a first supercooler (5D) and then The low-pressure nitrogen gas from the top of the second distillation column (5E) is condensed by the second condenser (5G), and the liquid nitrogen portion is refluxed to the top of the second distillation column (5E). A portion of the medium-pressure nitrogen gas from the top of the first distillation column (5B) is reheated in the heat exchanger (5A) and then compressed in the second compressor (5K2) of the cyclic compression system, and then returned to the top of the second distillation column (5E). The other part of the low pressure nitrogen coming out from the circulating compressor is reheated by the heat exchanger (5A) and then enters the first compressor (5K1) and the second compressor (5K2) of the circulating compression system to be compressed in succession. The first gas compressed by the second compressor (5K2) enters the second expander booster end (5P) of the high and low temperature gas expander to be boosted. After boosting, it enters the heat exchanger (5A) to be cooled. Some of the gas is extracted from the middle of the heat exchanger (5A) and enters the second expansion end (5U) to be expanded. The expanded fluid enters the second gas-liquid separator (5H), and the remaining gas is extracted from the bottom of the heat exchanger (5A). The gas from the other path directly enters the heat exchanger 5A and is extracted from the upper middle portion of the heat exchanger 5A and enters the first expansion end 5T for expansion. The expanded gas is then reheated in the heat exchanger 5A and then enters the first compressor 5K1 and the second compressor 5K2 of the circulating compression system for successive compression. The second gas-liquid separator 5H separates the fluid into gas and liquid, and the liquid flows out of the liquid outlet of the second gas-liquid separator 5H and is subcooled by the third subcooler 5J.A part of the liquid is adjusted in flow rate by the first throttle valve (V4) and enters the third subcooler (5J) to be reheated. The reheated liquid enters the heat exchanger (5A) 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 passage (85) to be used as high-purity liquid nitrogen product. The gas in the second gas-liquid separator (5H) flows out from the gas outlet of the second gas-liquid separator (5H) and is reheated by the heat exchanger (5A) and is supplied to the first compressor (5K1) of the cyclic compression system. ) and the second compressor (5K2) and compressed successively, the liquid discharged from the bottom of the second distillation column (5E) is subcooled by the second subcooler (5F) and then enters the evaporation side of the second condenser (5G) to be evaporated, the evaporated gas is reheated successively by the second subcooler (5F) and the first subcooler (5D), the reheated fluid enters the heat exchanger (5A) for further reheating, and is discharged from the nitrogen liquid system (100) as waste gas.

14. The method for using a low-energy consumption liquid production device using flue gas as described in claim 11, characterized in that the adsorbent used in the low-temperature medium-pressure adsorption device (1H) is mainly composed of molecular sieve, silica gel, and activated carbon, and two units are installed, but they can be used alone or simultaneously, and the drying system (1D) consists of two dryers connected in parallel, and the two dryers can be used alone or simultaneously.

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