A device for recovering carbon dioxide and nitrogen from flue gas, the device comprises a pretreatment system, a CO2 and N2 separation system, a N2 purification and liquefaction system, and a CO2 purification and liquefaction system, which are connected to each other by pipelines and valves, wherein the pretreatment system comprises a high-temperature NG cooler, a gas-liquid separator, a booster fan, and a dryer, which are used for removing water and cooling flue gas;
- the CO2 and N2 separation system comprises a low-temperature LNG cooler and a cryogenic adsorption device, which are used for further cooling and adsorbing the pretreated flue gas to separate CO2 and N2;
- the N2 purification and liquefaction system comprises a set of N2 distillation and liquefaction device consisting of a raw material compressor, a heat exchanger, a cooler, a gas-liquid separator, and a distillation system, which are used for further purifying and liquefying nitrogen-containing gas obtained from the CO2 and N2 separation system;
- the CO2 purification and liquefaction system comprises a set of CO2 distillation and liquefaction device consisting of a CO2 compressor, a cooler, an evaporator, a condenser, a liquefier, and a purification tower, which are used for further purifying and liquefying desorbed gas obtained from the CO2 and N2 separation system;
- a first inlet of the high-temperature NG cooler of the pretreatment system is connected to a flue gas discharge port, flue gas is further cooled by high-temperature cooling capacity NG, the cooled flue gas passes through a first outlet of the high-temperature NG cooler, most of water in the flue gas is removed by the gas-liquid separator, and the water is discharged via a water outlet of the gas-liquid separator;
- the cooled flue gas passes through a gas outlet of the gas-liquid separator, is pressurized by the booster fan, and then enters the dryer via a channel for further drying;
- the dryer in the pretreatment system is connected to an inlet of the low-temperature LNG cooler, and the pretreated dry flue gas is reduced to about a boiling point temperature of CO2 by LNG cold energy;
- an outlet of the low-temperature LNG cooler is connected to an inlet of the cryogenic adsorption device, CO2 in the cryogenic flue gas is adsorbed and captured by the principle of cryogenic adsorption, crude carbon dioxide gas with high carbon purity is obtained in a desorbed gas outlet of the cryogenic adsorption device, and nitrogen-containing gas with high nitrogen purity and carbon dioxide content below 1 ppm is obtained in a discharged gas outlet of the cryogenic adsorption device, thereby achieving a purpose of carbon-nitrogen separation;
- an adsorbent used in the cryogenic adsorption device is mainly molecular sieve or activated carbon;
- the discharged gas outlet of the cryogenic adsorption device is connected to an inlet of the raw material compressor of the N2 purification and liquefaction system to pressurize the nitrogen-containing gas;
- an outlet of the raw material compressor is connected to a first inlet of the cooler, a first outlet of the cooler is connected to a first inlet of the heat exchanger, a second inlet of the cooler is connected to a high-temperature cooling capacity NG inlet pipeline, and a second outlet of the cooler is connected to an NG discharge pipeline;
- a first outlet of the heat exchanger is connected to the distillation system, a nitrogen outlet of the distillation system is connected to a second inlet of the heat exchanger, a second outlet of the heat exchanger is connected to an inlet of a circulating compressor, an outlet of the circulating compressor is connected to a third inlet of the heat exchanger, a third outlet of the heat exchanger is connected to a first inlet of the gas-liquid separator, and a liquid nitrogen product is obtained at a bottom of the gas-liquid separator and flows out via a first outlet of the gas-liquid separator;
- a second outlet of the gas-liquid separator is connected to a sixth inlet of the heat exchanger, and the sixth inlet is connected to the second outlet of the heat exchanger;
- an emptying gas outlet of the distillation system is connected to a fourth inlet of the heat exchanger, and a fourth outlet of the heat exchanger is connected to an emptying pipeline;
- an LNG liquid inlet is connected to a fifth inlet of the heat exchanger, and a high-temperature cooling capacity NG outlet is connected to a fifth outlet of the heat exchanger;
- the nitrogen-containing gas obtained from the CO2 and N2 separation system is further purified and liquefied by the principle of cryogenic distillation to obtain a high-purity liquid nitrogen product, and the distillation system is a single-tower distillation or double-tower distillation system;
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- the desorbed gas outlet of the cryogenic adsorption device is connected to an inlet of the CO2 compressor of the CO2 purification and liquefaction system to pressurize the crude carbon dioxide gas;
- an outlet of the CO2 compressor is connected to a first inlet of the cooler, a first outlet of the cooler is connected to an inlet of the evaporator, a second inlet of the cooler is connected to the high-temperature cooling capacity NG inlet pipeline, and a second outlet of the cooler is connected to the NG discharge pipeline;
- an outlet of the evaporator is connected to a first inlet of the liquefier, a first outlet of the liquefier is connected to a middle inlet of the purification tower, a second inlet of the liquefier is connected to the high-temperature cooling capacity NG inlet pipeline, and a second outlet of the liquefier is connected to the NG discharge pipeline;
- a first inlet of the condenser is connected to the high-temperature cooling capacity NG inlet pipeline, and a first outlet of the condenser is connected to the NG outlet pipeline;
- and an industrial grade liquid carbon dioxide product is obtained at a bottom of the purification tower, and a first outlet at the bottom of the purification tower is connected to a storage system or a carbon dioxide refining system for secondary purification of CO2 to obtain food grade carbon dioxide;
- and a second outlet of the purification tower is connected to the exhaust gas emptying pipeline.