| CPC F25J 3/04527 (2013.01) [F23B 80/02 (2013.01); F23L 7/007 (2013.01); F25J 3/04284 (2013.01); F25J 3/04848 (2013.01); F27B 7/42 (2013.01)] | 8 Claims |
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1. A carbon-based oxygen-enriched combustion method for recirculation of flue gas from a cement kiln, wherein a system required by the combustion method comprises a dedicated pressurized oxygen preparation device, a pressurized oxygen buffer tank, an atmospheric-pressure oxygen preparation device, an atmospheric-pressure oxygen buffer tank, a first dedicated efficient oxygen/recirculating flue gas mixer, a second dedicated efficient oxygen/recirculating flue gas mixer, a third dedicated efficient oxygen/recirculating flue gas mixer, a recirculating flue gas fan, a carbon-based air fan and a recirculating flue gas recovery device;
the dedicated pressurized oxygen preparation device comprises a filter, a turbine air compressor, an air pre-cooling unit, alternately used molecular sieve adsorbers, an electric heater, a main heat exchanger, a rectifying tower I, a main condenser-evaporator I, a rectifying tower II, a main condenser-evaporator II, a rectifying tower III, a main condenser-evaporator III, a supercooler, an expander and a liquid nitrogen pump, wherein the turbine air compressor is an original supporting air compressor system of the cement kiln;
the filter, the turbine air compressor, the air pre-cooling unit, the alternately used molecular sieve adsorbers and the electric heater are disposed outside a cold box, the main heat exchanger, the rectifying tower I, the main condenser-evaporator I, the rectifying tower II, the main condenser-evaporator II, the rectifying tower III, the main condenser-evaporator III, the supercooler, the expander and the liquid nitrogen pump are disposed inside the cold box, the main condenser-evaporator I is disposed on the rectifying tower I, the main condenser-evaporator II is disposed on the rectifying tower II, and the main condenser-evaporator III is disposed at a bottom of the rectifying tower III;
the filter, the turbine air compressor, the air pre-cooling unit, the alternately used molecular sieve adsorbers and the main heat exchanger are connected sequentially, and the main heat exchanger is connected to a raw air inlet at a bottom of the rectifying tower I;
a liquid air outlet at the bottom of the rectifying tower I is connected to the supercooler, the supercooler is connected to the main condenser-evaporator I, a connecting pipe between the supercooler and the main condenser-evaporator I is provided with a throttle valve, an oxygen-enriched air outlet of the main condenser-evaporator I is connected to a bottom of the rectifying tower II, and a liquid air outlet of the main condenser-evaporator I is connected to the main condenser-evaporator II;
a pressurized nitrogen outlet at a top of the rectifying tower I is respectively connected to the main condenser-evaporator I, the main condenser-evaporator III and the main heat exchanger, and a liquid nitrogen outlet of the main condenser-evaporator I is connected to the top of the rectifying tower I; and the main heat exchanger is connected to a pressurized nitrogen product supply pipe;
an oxygen-enriched liquid air outlet at the bottom of the rectifying tower II is respectively connected to the main condenser-evaporator II and a top of the rectifying tower III, and connecting pipes between the oxygen-enriched liquid air outlet at the bottom of the rectifying tower II and the main condenser-evaporator II and between the oxygen-enriched liquid air outlet at the bottom of the rectifying tower II and the top of the rectifying tower III are respectively provided with a throttle valve; and a waste nitrogen outlet of the main condenser-evaporator II is connected to the supercooler, the supercooler is connected to a waste nitrogen inlet of the main heat exchanger, a waste nitrogen outlet of the main heat exchanger is respectively connected to an external vent pipe and the electric heater, and the electric heater is connected to the alternately used molecular sieve adsorbers;
a low-pressure nitrogen outlet at a top of the rectifying tower II is connected to the main condenser-evaporator II, a liquid nitrogen outlet of the main condenser-evaporator II is respectively connected to the top of the rectifying tower II and an inlet of the liquid nitrogen pump, and an outlet of the liquid nitrogen pump is connected to the top of the rectifying tower I;
the main condenser-evaporator III is located at the bottom of the rectifying tower III, an oxygen outlet of the rectifying tower III is connected to the main heat exchanger, the main heat exchanger is connected to a pressurized oxygen product supply pipe, a liquid nitrogen outlet of the main condenser-evaporator III is connected to the top of the rectifying tower I, and a liquid oxygen outlet of the rectifying tower III is connected to a liquid oxygen product supply pipe;
pressurized waste nitrogen at the top of the rectifying tower III is connected to the supercooler, the supercooler is connected to the main heat exchanger, a partial reheating outlet of the main heat exchanger is connected to the expander, and the expander is connected to the waste nitrogen inlet of the main heat exchanger;
a process of preparing a pressurized oxygen product by using the dedicated pressurized oxygen preparation device comprises the following steps:
step I: after dust and mechanical impurities are removed from raw air through the filter, sending the filtered raw air to the turbine air compressor such that the air is compressed to a set pressure; and then pre-cooling the air by the air pre-cooling unit, and purifying the air by the alternately used molecular sieve adsorbers;
step II: enabling a part of the purified raw air to serve as instrument air, and sending the remaining part to the main heat exchanger such that the purified raw air is cooled to a saturation temperature and has a certain moisture content, which is then sent into the bottom of the rectifying tower I to participate in rectification;
step III: after the air is rectified by the rectifying tower I, obtaining liquid air and pressurized nitrogen, enabling the liquid air to be supercooled by the supercooler, throttled by the throttle valve and sent into the main condenser-evaporator I to exchange heat with the pressurized nitrogen as a cold source such that the liquid air is vaporized into oxygen-enriched air, introducing the oxygen-enriched air into the bottom of the rectifying tower II to participate in rectification, and at the same time, introducing a part of the liquid air from the main condenser-evaporator I into the main condenser-evaporator II to serve as the cold source; introducing a part of the pressurized nitrogen into the main condenser-evaporator I to exchange heat with the liquid air as a heat source such that the pressurized nitrogen is liquefied into liquid nitrogen, and introducing the liquid nitrogen into the top of the rectifying tower I to serve as a reflux; and introducing another part of the pressurized nitrogen into the main condenser-evaporator III to serve as a heat source, and enabling the remaining part of the pressurized nitrogen to be reheated by the main heat exchanger and sent out of the cold box to serve as a pressurized nitrogen product;
step IV: after the liquid nitrogen and the oxygen-enriched air are rectified by the rectifying tower II, obtaining oxygen-enriched liquid air from the bottom of the rectifying tower II, and obtaining low-pressure nitrogen from the top of the rectifying tower II; enabling a part of the oxygen-enriched liquid air to be throttled by the throttle valve and sent into the main condenser-evaporator II to exchange heat with the low-pressure nitrogen as a cold source such that the oxygen-enriched liquid air is vaporized into waste nitrogen, enabling the waste nitrogen to be reheated by the supercooler and the main heat exchanger and sent out of the cold box, enabling a part of the waste nitrogen to serve as regeneration gas of the alternately used molecular sieve adsorbers and the remaining part to be vented, and enabling the remaining part of the oxygen-enriched liquid air to be throttled by the throttle valve and sent into the top of the rectifying tower III to participate in rectification; and introducing the low-pressure nitrogen into the main condenser-evaporator II to exchange heat with the oxygen-enriched liquid air as a heat source such that the low-pressure nitrogen is liquefied into liquid nitrogen, introducing a part of the liquid nitrogen into the top of the rectifying tower II to participate in rectification, and enabling the remaining part of the liquid nitrogen to be pressurized by the liquid nitrogen pump and sent into the top of the rectifying tower I to serve as the reflux;
step V: after the oxygen-enriched liquid air is rectified by the rectifying tower III, obtaining liquid oxygen and pressurized waste nitrogen, enabling the liquid oxygen to serve as a cold source of the main condenser-evaporator III and exchange heat with the pressurized nitrogen introduced from the rectifying tower I such that the liquid oxygen is vaporized into gaseous oxygen, and enabling a part of the gaseous oxygen to be reheated by the main heat exchanger and sent out of the cold box as a pressurized oxygen product and the remaining part of the gaseous oxygen to serve as uprising gas of the rectifying tower III; after the pressurized nitrogen is liquefied into liquid nitrogen, introducing the liquid nitrogen into the top of the rectifying tower I to serve as the reflux, and at the same time, introducing a part of the liquid oxygen from the bottom of the rectifying tower III to serve as a liquid oxygen product; and enabling the pressurized waste nitrogen to be reheated by the supercooler, partially reheated by the main heat exchanger and expanded by the expander, then enabling the expanded waste nitrogen to be reheated by the main heat exchanger and sent out of the cold box, and enabling a part of the obtained waste nitrogen to serve as the regeneration gas of the alternately used molecular sieve adsorbers and the remaining part to be vented;
the pressurized nitrogen product prepared by the dedicated pressurized oxygen preparation device has a purity of less than 3 ppmO2 and a pressure of 0.68-0.95 MpaG; and the pressurized oxygen product prepared has a purity of 90-99.6% and a pressure of 0.1-0.3 MpaG;
the first dedicated efficient oxygen/recirculating flue gas mixer, the second dedicated efficient oxygen/recirculating flue gas mixer and the third dedicated efficient oxygen/recirculating flue gas mixer each comprise an oxygen channel, an oxygen channel regulating valve, a recirculating flue gas channel, an oxygen sparger, a mixer, a carbon-based oxygen-enriched product channel and an oxygen concentration analyzer; the oxygen sparger is a hollow cylinder, a peripheral wall of the hollow cylinder is uniformly provided with a plurality of small holes, and the mixer is a hollow cylinder; the oxygen channel regulating valve is disposed on the oxygen channel, an outlet of the oxygen channel communicates with an end portion of the oxygen sparger, and the oxygen sparger and a part of the oxygen channel are inserted into the mixer through a side wall of the mixer; and an outlet of the recirculating flue gas channel communicates with one end of the mixer, an inlet of the carbon-based oxygen-enriched product channel communicates with the other end of the mixer, and the oxygen concentration analyzer is disposed on the carbon-based oxygen-enriched product channel;
a pressurized oxygen product outlet of the dedicated pressurized oxygen preparation device is connected to the pressurized oxygen buffer tank, a first outlet of the pressurized oxygen buffer tank is connected to an inlet of the oxygen channel of the first dedicated efficient oxygen/recirculating flue gas mixer, a second outlet of the pressurized oxygen buffer tank is connected to an inlet of the oxygen channel of the second dedicated efficient oxygen/recirculating flue gas mixer, and a pressurized nitrogen product outlet of the dedicated pressurized oxygen preparation device is connected to a dust collector of the cement kiln;
an atmospheric-pressure oxygen product outlet of the atmospheric-pressure oxygen preparation device is connected to the atmospheric-pressure oxygen buffer tank, and an outlet of the atmospheric-pressure oxygen buffer tank is connected to an inlet of the oxygen channel of the third dedicated efficient oxygen/recirculating flue gas mixer;
an inlet of the recirculating flue gas recovery device is connected to a recirculating flue gas outlet of a preheater of the cement kiln, an outlet of the recirculating flue gas recovery device is divided into two paths, one path is connected to the recirculating flue gas fan, an outlet of the recirculating flue gas fan is respectively connected to an inlet of the recirculating flue gas channel of the first dedicated efficient oxygen/recirculating flue gas mixer and an inlet of the recirculating flue gas channel of the second dedicated efficient oxygen/recirculating flue gas mixer, and the other path is connected to an inlet of the recirculating flue gas channel of the third dedicated efficient oxygen/recirculating flue gas mixer;
an outlet of the carbon-based oxygen-enriched product channel of the first dedicated efficient oxygen/recirculating flue gas mixer is provided with a throttle valve and used to provide a medium-pressure carbon-based oxygen-enriched product which serves as coal supply air of the rotary kiln and a precalciner, an outlet of the carbon-based oxygen-enriched product channel of the second dedicated efficient oxygen/recirculating flue gas mixer is divided into three paths, one path is provided with a throttle valve and used to provide a low-pressure carbon-based oxygen-enriched product which serves as swirling air of a burner of the rotary kiln, another path is provided with a throttle valve and used to provide a high-pressure carbon-based oxygen-enriched product which serves as internal axial flow air of the burner of the rotary kiln, and the other path is provided with a throttle valve and used to provide a high-pressure carbon-based oxygen-enriched product which serves as external axial flow air of the burner of the rotary kiln; and an outlet of the carbon-based oxygen-enriched product channel of the third dedicated efficient oxygen/recirculating flue gas mixer is connected to the carbon-based air fan, an outlet of the carbon-based air fan is connected to a grate cooler, and the grate cooler is respectively connected to the rotary kiln and the precalciner;
the combustion method comprises the following steps:
sending the pressurized nitrogen prepared by the dedicated pressurized oxygen preparation device into the dust collector of the cement kiln to serve as dust removal air; sending the pressurized oxygen prepared by the dedicated pressurized oxygen preparation device into the pressurized oxygen buffer tank, sending a part of the pressurized oxygen introduced from the pressurized oxygen buffer tank into the first dedicated efficient oxygen/recirculating flue gas mixer, and sending the other part of the pressurized oxygen into the second dedicated efficient oxygen/recirculating flue gas mixer;
sending the atmospheric-pressure oxygen prepared by the atmospheric-pressure oxygen preparation device into the atmospheric-pressure oxygen buffer tank, and sending the atmospheric-pressure oxygen introduced from the atmospheric-pressure oxygen buffer tank into the third dedicated efficient oxygen/recirculating flue gas mixer;
after the recirculating flue gas from the preheater of the cement kiln is subjected to heat recovery, dust removal and desulfurization through the recirculating flue gas recovery device, enabling a part of the recirculating flue gas to be pressurized by the recirculating flue gas fan and respectively introduced into the first dedicated efficient oxygen/recirculating flue gas mixer and the second dedicated efficient oxygen/recirculating flue gas mixer, and introducing the other part of the recirculating flue gas into the third dedicated efficient oxygen/recirculating flue gas mixer;
mixing the pressurized oxygen and the recirculating flue gas in the first dedicated efficient oxygen/recirculating flue gas mixer, and throttling the mixture to provide the medium-pressure carbon-based oxygen-enriched product which serves as the coal supply air of the rotary kiln and the precalciner, wherein the medium-pressure carbon-based oxygen-enriched product contains 25-50% of O2 and has a pressure of 50-70 Kpa;
mixing the pressurized oxygen and the recirculating flue gas in the second dedicated efficient oxygen/recirculating flue gas mixer, and throttling the mixture to different degrees to respectively provide the low-pressure carbon-based oxygen-enriched product and the high-pressure carbon-based oxygen-enriched product, the low-pressure carbon-based oxygen-enriched product serving as the swirling air of the burner of the rotary kiln, and the high-pressure carbon-based oxygen-enriched product respectively serving as the external axial flow air and the internal axial flow air of the burner of the rotary kiln, wherein the low-pressure carbon-based oxygen-enriched product contains 25-50% of O2 and has a pressure of 20-40 Kpa; and the high-pressure carbon-based oxygen-enriched product contains 25-50% of O2 and has a pressure of 80-100 Kpa; and
mixing the atmospheric-pressure oxygen and the recirculating flue gas in the third dedicated efficient oxygen/recirculating flue gas mixer, pressurizing the mixture by the carbon-based air fan to provide a carbon-based air product, sending the carbon-based air product into the grate cooler to cool clinker, and then sending the carbon-based air product respectively into the rotary kiln and the precalciner, wherein the carbon-based air product has an oxygen content similar to that of air and a pressure of 3-10 Kpa.
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