A resource-based clean emission system and method for coal-fired power plants

Abstract

The present invention discloses a resource-based clean emission system and method for a coal-fired power plant. O2, N2, and Ar are obtained through the air separation process. O2 is used as an oxidant to gasify coal to produce H2. H2 and N2 are synthesized into NH3. The flue gas is purified through the flue gas treatment process, and SO2 and CO2 in the flue gas are recovered. The obtained NH3, SO2, and CO2 can be further converted into fertilizer products. Steam is generated by a steam boiler for power generation. The water treatment process is used to solve the recycling of water. The flue gas, sludge generated from water treatment, and waste catalysts and other harmful waste residues generated from other processes are processed into glass bodies that can be used to make high-grade environmental protection building materials in the solid waste treatment module, and heavy metals are recovered. All raw materials in the present invention are only coal and air. The products that can be output include N2, Ar, H2, NH3, SO2, CO2, NH4HCO3, (NH4)2SO4, metals, high-grade environmental protection building materials, and electricity. There is almost no waste emission, achieving energy-saving and environmental protection treatment effects.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, and more particularly to a resource-based clean emission system and method for a coal-fired power plant. Background Art

[0002] Since the beginning of the Industrial Revolution, coal has been the world's major energy source for hundreds of years. Even after oil replaced coal as the world's major energy source, coal remains one of the world's most important basic energy sources.

[0003] In the current situation of our country, the proportion of coal consumption is still higher than 62%, but there are still many problems in the energy conservation and emission reduction development of coal-fired power plants.

[0004] In terms of desulfurization: First, due to the increase in the actual sulfur content of coal and the small design margin of the desulfurization device; second, the operating performance of the existing desulfurization device has declined, and the desulfurization efficiency cannot meet the national standard requirements; third, the currently widely used wet FGD desulfurization, due to the low efficiency of the demister, after canceling the GGH, has exacerbated the formation of "gypsum rain".

[0005] In terms of denitrification: First, the NO X emission concentration generated by the boiler is relatively high, resulting in an increase in the investment and operating costs of tail SCR denitrification; second, after the denitrification transformation of some boilers, the content of fly ash combustibles and CO in the boiler flue gas has increased, resulting in a decrease in the boiler thermal efficiency.

[0006] In terms of soot: First, due to the actual coal combustion and site limitations, most of the existing dust collectors are difficult to meet the emission standards; second, the operation and maintenance costs of electric-bag dust collectors are high, and it is difficult to dispose of waste filter bags.

[0007] In terms of flue gas emission temperature: Since the flue gas temperature is relatively low after desulfurization and denitrification, a lot of PM2.5 is carried by the saturated water vapor in it, resulting in a serious decline in air quality.

[0008] Therefore, optimizing the overall emission control technologies for various pollutants to achieve resource-based, integrated, and collaborative control is the direction and practical significance of energy conservation and emission reduction in future coal-fired power plants in our country.

[0009] Therefore, providing a resource-based clean emission system and method for a coal-fired power plant is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0010] In view of this, the present invention provides a resource-based clean emission system and method for a coal-fired power plant with high power generation efficiency, low energy consumption, and low pollutant emissions.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A resource-based clean emission system for a coal-fired power plant, comprising:

[0013] An air separation module for filtering dust and impurities in the air and separating out O2, N2, and Ar;

[0014] A gasification module connected to the air separation module for generating syngas and coal slag through a gasification reaction of water, coal, and O2 separated by the air separation module at high temperature;

[0015] A dehydrogenation module connected to the gasification module for separating and purifying the syngas to obtain H2;

[0016] A steam power generation module connected to the air separation module and the gasification module respectively for adding solid slag, coal, and the syngas after separating H2, O2 separated by the air separation module, or recycled flue gas plus oxygen to burn and generate ultra-supercritical or high, medium, and low-pressure steam to drive a steam generator to generate electricity;

[0017] An ammonia synthesis module connected to the air separation module and the dehydrogenation module respectively for generating NH3 from the purified H2 and separated N2 under high temperature, high pressure, and the action of a catalyst;

[0018] A flue gas washing module for preliminarily treating the flue gas after fuel combustion in the steam power generation module, removing dust and heavy metals in the flue gas, and recovering the moisture and heat therein;

[0019] A gas recovery module for obtaining pure liquid SO2 and CO2 by solvent absorption, desorption, and compression liquefaction of the washed flue gas;

[0020] A water treatment module for treating the sewage generated by flue gas washing, the drainage of the steam power generation module, and the sewage generated in other processes into system circulating water or reclaimed water meeting the discharge standard.

[0021] Preferably, the resource-based clean emission system uses coal and its gasification products as fuel, uses pure oxygen, or pure oxygen mixed with a certain proportion of recycled flue gas as the combustion-supporting agent, with less flue gas emission and no nitrogen oxides. Optionally, the fuel can be various coals or other solid fuels, liquid fuels such as heavy oil, and other gaseous fuels.

[0022] Preferably, the steam generator is any one of supercritical, fully condensing, extraction condensing, and back pressure types.

[0023] Preferably, the dehydrogenation module includes:

[0024] A membrane separator, through which only H2 in the syngas passes through the ceramic membrane of the membrane separator, and other components in the syngas are sent to the steam boiler of the steam power generation module for combustion;

[0025] A compressor, which is connected to the membrane separator and is used to compress the separated H2 to 30 - 35 MPa for output storage.

[0026] Preferably, the ammonia synthesis module includes:

[0027] An ammonia synthesis reaction tower. The N2 and H2 are introduced into the ammonia synthesis reaction tower in a ratio of 1:2.8 - 2.9, and the pressure in the reaction tower is controlled at 30 - 35 Mpa and the temperature is 450 - 550 °C to synthesize NH3;

[0028] A refrigerator, which cools the NH3 discharged from the outlet of the reaction tower to 20 - 35 °C and then stores it under the condition of a pressure of 1.6 - 1.8 Mpa.

[0029] Preferably, the flue gas washing module includes: a spray tower and a purification and washing device located in the spray tower. The spray tower transfers the soot, heavy metals, and heat in the flue gas to the washing water, and the purification and washing device discharges the washed and purified flue gas from the top of the tower, controls the flue gas temperature at 38 - 42 °C, and the washed sewage is sent to the water treatment module from the bottom of the tower.

[0030] Preferably, the water circulation treatment module includes:

[0031] An ultrasonic electrocoagulator, which flocculates most of the suspended substances and ions in the sewage;

[0032] A solid-liquid separator, which separates the flocculated matter in the sewage to form sludge;

[0033] A heat pump, which uses the sewage discharged from the steam boiler and a small amount of steam to extract most of the heat of the low-temperature water and heat a part of the low-temperature water to 95 - 99 °C;

[0034] An MVC device, which processes the 95 - 99 °C hot water by a mechanical evaporation and condensation process into distilled water as the make-up water for the steam boiler, and the concentrated water is used as the water for the gasification module, and the low-temperature water from which the heat is extracted is used as low-temperature water such as spray water.

[0035] Preferably, it further includes a solid residue treatment module, which is respectively connected to the flue gas washing module and the steam power generation module, and is used to recover heavy metals from the sludge separated from the sewage and the solid particles in the soot and coal ash at high temperature, and process the others into glass bodies.

[0036] A resource-based clean emission method for a coal-fired power plant includes the following steps:

[0037] S1: Separating air through an air separation module to obtain N2, O2, and Ar;

[0038] S2: Use the separated O2, coal, and water to undergo a gasification reaction under high-temperature conditions in the gasification module to obtain syngas and coal slag;

[0039] S3: The syngas is separated and purified through the dehydrogenation module to obtain pure H2, and other gases in the syngas except H2 are directly sent to the steam boiler for combustion;

[0040] S4: Synthesize NH3 from the purified H2 and N2 separated from air in the ammonia synthesis module;

[0041] S5: Burn coal, coal slag, and syngas in the steam boiler, heat water to generate steam to drive the steam turbine for power generation;

[0042] S6: Wash and treat the flue gas discharged after the combustion of the steam boiler through the flue gas washing module to remove dust, and recover water and heat in the flue gas;

[0043] S7: Recover SO2 and CO2 in the flue gas through the gas recovery module;

[0044] S8: Treat the sewage generated by flue gas washing, the drainage of the steam boiler, and the sewage generated in other processes through the water treatment module into system circulating water or reclaimed water meeting the discharge standard;

[0045] S9: The solid residue treatment module treats soot, coal ash, and sludge, recovers heavy metals, and forms vitreous bodies for the rest.

[0046] Preferably, in S8, it includes: cutting or crushing the soot, coal ash, and sludge in the sewage into particles of 1-5 mm and feeding them into the plasma furnace.

[0047] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a resource-based clean emission system and method for a coal-fired power plant, which obtains O2, N2, and Ar through the air separation process; burns with O2 and produces H2 through coal gasification; synthesizes NH3 by combining H2 and N2 in the ammonia synthesis process; purifies the flue gas through the flue gas treatment process, and recovers SO2 and CO2 in the flue gas through the SO2 recovery process and the CO2 recovery process respectively. The obtained NH3, SO2, and CO2 can be further converted into fertilizer products. Steam is generated by a steam boiler for power generation, and the water treatment process is used to solve the recycling of water. The sludge generated by water treatment and the waste catalyst and other harmful waste residues generated by other processes are melted at high temperature in a plasma furnace in the solid waste treatment module to be processed into glass bodies that can be used to make high-grade environmental protection building materials, and heavy metals are recovered. All the raw materials in the present invention are only coal and air, and the products that can be output include N2, Ar, H2, NH3, SO2, CO2, NH4HCO3, (NH4)2SO4, metals, high-grade environmental protection building materials, and electricity. Except for normal water and nitrogen losses, almost no waste is discharged. Therefore, the technical problems of energy conservation and environmental protection in the resource-based clean emission of waste from coal-fired power plants are solved, and the effects of high efficiency and low cost are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0049] Figure 1 It is a flowchart of a resource-based clean emission method for a coal-fired power plant of the present invention.

[0050] Figure 2 It is a structural diagram of a resource-based clean emission system for a coal-fired power plant of the present invention.

[0051] Specifically:

[0052] 1 - Compressed air cryogenic machine, 2 - Air separation equipment, 3 - Coal gasifier, 4 - Steam boiler, 5 - Flue gas circulation fan, 6 - Steam generator, 7 - Dust collector, 8 - Spray tower, 9 - Water treatment, 10 - Plasma heavy metal recovery device, 11 - SO2 absorption tower, 12 - CO2 absorption tower, 13 - First fertilizer plant, 14 - Second fertilizer plant, 15 - Hydrogen purification, 16 - Devices such as ammonia synthesis, 17 - Ultrasonic electrocoagulator, 18 - Heat pump, 19 - Steam condenser, 20 - SO2 stripping tower, 21 - First heat exchanger, 22 - First reboiler, 23 - SO2 compressor, 24 - SO2 refining tower, 25 - CO2 stripping tower, 26 - Second heat exchanger, 27 - Second reboiler, 28 - CO2 compressor, 29 - CO2 refining tower. Detailed implementation manners

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] The embodiment of the present invention discloses a resource-based clean emission system for a coal-fired power plant. Since the composition of coal is complex, in order to thoroughly and optimally cleanly utilize coal, the system of this embodiment includes:

[0055] An air separation module for filtering dust and impurities in the air and separating out O2, N2, and Ar;

[0056] A gasification module, connected to the air separation module, for generating syngas and coal slag through a gasification reaction at high temperature with water, coal, and O2 separated by the air separation module;

[0057] A dehydrogenation module, connected to the gasification module, for separating and purifying syngas to obtain H2;

[0058] A steam power generation module, respectively connected to the air separation module and the gasification module, for adding solid slag, coal, and syngas after separating H2, O2 separated by the air separation module, or recycled flue gas plus oxygen, burning to generate ultra-critical or high, medium, and low-pressure steam, and driving a steam generator to generate electricity;

[0059] An ammonia synthesis module, respectively connected to the air separation module and the dehydrogenation module, for generating NH3 from the purified H2 and separated N2 under high temperature, high pressure, and the action of a catalyst;

[0060] A flue gas washing module, which is used for the preliminary treatment of the flue gas after the fuel combustion of the steam power generation module, removing dust and heavy metals in the flue gas, and recovering the moisture and heat therein;

[0061] A gas recovery module, which is used to obtain pure liquid SO2 and CO2 after the washed flue gas is absorbed, desorbed and compressed and liquefied by a solvent;

[0062] A water treatment module, which treats the sewage generated by flue gas washing, the drainage of the steam power generation module and the sewage generated by other processes into system recycled water or reclaimed water meeting the discharge standards.

[0063] Advantageously, it further includes a solid residue treatment module, which is respectively connected with the flue gas washing module and the steam power generation module, and is used for recovering heavy metals from the sludge separated from the sewage, soot and solid particles in coal ash at high temperature, and processing the others into glass bodies.

[0064] This system uses coal and its gasification products as fuel, uses pure oxygen, or pure oxygen mixed with a certain proportion of recycled flue gas as the combustion aid, with less flue gas emissions and no nitrogen oxides. Optionally, the fuel can be various coals or other solid fuels, liquid fuels such as heavy oil, and other gas fuels.

[0065] Specifically, the function of the steam generation process of the steam boiler is to generate superheated steam, including supercritical, high-pressure, medium-pressure, and low-pressure superheated steam. The steam is mainly used for power generation, and can also be used in other processes when using heat and driving; the main fuel of the boiler is coal, and various solid fuels such as coal, liquid fuels such as heavy oil, and other gas fuels can be used; air is not used as the oxidant, but pure oxygen or a mixture of pure oxygen and recycled flue gas is used, and the mixing ratio range is: oxygen content 21-100%, which not only meets the requirement of replacing air with 21% oxygen content, but also can appropriately increase the oxygen content until the all-oxygen combustion mode is adopted. Therefore, there is no thermal NO in the boiler X , and through the control of the combustion process, the nitrogen-containing substances in the fuel burn to generate N2, so there is almost no NO in the flue gas X , which is 72%-75% less than the conventional flue gas volume, and the main components are CO2, H2O, a small amount of O2, and SO2, etc.

[0066] Add a small amount of catalyst to the coal, crush it into a water coal slurry and feed it into the gasifier. Using pure oxygen as the oxidant, the highest H2 yield of the gasification reaction is controlled under high pressure. At this time, the CO and CH4 yields are also very high. When the pressure reaches 23.4 Mpa and the temperature is 650 °C, the H2 yield can reach 199% of the H content in the raw material. The synthesis gas recovers heat through a waste heat boiler, generates steam and enters the patented steam system for unified distribution and use, and then goes to H2 purification; the solid residue after gasification is directly transported to the steam boiler for further combustion, and the coal slag is uniformly processed into high-grade environmental protection building materials.

[0067] Advantageously, the resource-based clean emission system of the coal-fired power plant further includes equipment such as a plunger pump, a compressor, a Roots blower, a product storage tank, etc., and a computer control system, which is electrically connected to each module to coordinately control the whole process.

[0068] As Figure 1 shown, a resource-based clean emission method for a coal-fired power plant is as follows:

[0069] The air separation process includes: filtering dust, mechanical impurities, etc. in the air through a filter; compressing the air using an air compressor; removing moisture in the air with a dehydrator; lowering the temperature of the air to liquefy it with a refrigerator; separating the liquefied air into O2, Ar, and N2 in a separation tower; compressing N2 with an N2 compressor; and lowering the temperature of N2 to liquefy it with an N2 refrigerator.

[0070] The steam power generation process includes: a feeder connected to a steam boiler for feeding fuels such as coal into the boiler; a burner for burning other liquid or gaseous fuels; supercritical, high-pressure, medium-pressure, and low-pressure evaporators for heating water into superheated steam at different pressures; an economizer for recovering the waste heat of the flue gas and lowering the flue gas discharge temperature; and a plunger pump for boosting the water supply pressure of the boiler; an induced draft fan 5 for drawing out part of the flue gas and mixing it with O2 in a certain proportion as an oxidant to form a flue gas cycle; a slag discharger for discharging the coal slag after combustion and recovering heat or directly discharging it to the solid slag treatment module; a combustion control system for controlling the oxygen usage according to the steam temperature of the boiler, the oxygen content in the flue gas, etc.; a steam generator for generating electricity using steam, which can be any one of supercritical, condensing, extraction condensing, back pressure type, etc., and the exhausted steam after power generation is condensed using circulating cooling water, and the circulating cooling water transfers the recovered latent heat of the steam to a heat pump; the steam generated by the steam boiler can be supercritical, high-pressure, medium-pressure, or low-pressure steam, improving the power generation efficiency.

[0071] The coal gasification process is as follows: A mixture made of 65%-70% coal with different particle size distributions, about 29-34% water, and about 1% chemical additive is introduced into the separated oxygen to react in a gasifier to generate high-temperature synthesis gas and coal slag. The reaction conditions can be atmospheric gasification with a pressure of 0-0.35 Mpa, medium-pressure gasification with a pressure of 0.7-3.5 Mpa, high-pressure gasification with a pressure of 7 Mpa, or even supercritical gasification with a pressure of 23.4 Mpa. Then, the heat of the synthesis gas is recovered by a waste heat boiler, reducing the temperature of the synthesis gas to about 130°C. The gasified coal slag is discharged from the gasifier using a slag discharger and sent to the steam boiler for continued combustion (when gasification is incomplete), or directly discharged to the solid slag treatment module (when gasification is complete).

[0072] The hydrogen purification process includes: separating H2 through a membrane separator to obtain pure H2, and sending the remaining gas to a steam boiler for combustion. Conventional purification can also be used, where heat is recovered first and then CO is purified, followed by the purification of H2. The purified H2 is compressed by a compressor to 30 - 35 Mpa for storage.

[0073] The ammonia synthesis process includes: introducing the N2 and H2 into an ammonia synthesis reaction tower in a ratio of 1:2.8 - 2.9, with an operating pressure of around 30 - 35 Mpa and a temperature of 450 - 550 °C. An ammonia separation refrigerator cools the NH3 discharged from the outlet of the reaction tower to 20 - 35 °C and stores it under a pressure of 1.6 - 1.8 Mpa.

[0074] Advantageously, the ammonia synthesis process is also equipped with a recycle gas compressor that compresses the gas after separating NH3 and recycles it to the inlet of the reaction tower to further produce NH3 and make full use of the raw materials.

[0075] The flue gas washing process includes: removing most of the soot using a dust collector, and then using a spray tower to transfer the soot, heavy metals, and heat in the flue gas to the washing water; the purification washing device includes a demister that can discharge the washed and purified flue gas from the top of the tower at a temperature of about 40 °C; a spray water pump that sends the washing water to the top of the tower and sprays it evenly in multiple layers inside the tower; a washing water pump that sends the washed water from the bottom of the tower to the water treatment module.

[0076] The water treatment process includes: an electro - ultrasonic flocculator that flocculates most of the suspended solids, ions, etc. in the sewage; a solid - liquid separator that separates the flocs in the sewage to form sludge and sends it to the solid waste treatment module; a heat pump that uses the boiler blowdown water and a small amount of steam to extract the heat of most of the low - temperature water and heat a part of the low - temperature water to 95 - 99 °C to facilitate the next step of treating it into pure water; an MVC device that uses the mechanical evaporation and condensation process to treat the 95 - 99 °C hot water into distilled water with a yield of 40 - 90%, which is used as boiler make - up water, and the concentrated water is used as water for the coal gasification process, etc. The low - temperature water from which the heat has been extracted is used as low - temperature water such as spray water; in addition, there is also a water storage tank that stores sewage, distilled water, concentrated water, spray water, reclaimed water, etc.

[0077] The solid waste treatment process includes: a feeding device that cuts or crushes the sludge, soot, coal ash, etc. into solid particles of 1 - 5 mm and sends them into a plasma furnace. A plasma torch is used to generate high temperature to instantly melt or even gasify the raw materials entering the furnace. The organic components are thermally cracked and reformed by the steam generated at high temperature into small - molecule CO, H2, CH4, CO2, etc. The liquid inorganic components are discharged from the plasma furnace through a slag discharger, and after recovering the metal, they become vitreous bodies. In addition, the vitreous bodies can be further used to produce high - grade environmental protection building materials together with the furnace slag generated by the boiler.

[0078] Such as Figure 2As shown, after the air is liquefied by the compressed air cryogenic refrigerator 1, the air separation equipment 2 separates the liquid air to produce oxygen. Usually, cryogenic oxygen production is used because of the large oxygen demand, and nitrogen and argon are obtained at the same time. Optionally, when the oxygen demand is not too large, or when the economy allows, it can be a VPSA oxygen production device or a membrane separation device for oxygen production. When Ar or other inert gases are carried in the oxygen, the increased flue gas volume and its impact on the subsequent process should be considered. After the SO2 is recovered, the CO2 concentration in the flue gas decreases, so a CO2 absorption and desorption device is needed for concentration.

[0079] The O2 obtained from the air separation process enters the coal gasification furnace 3 and the steam boiler 4 respectively. Using O2 as an oxidant, the coal gasification furnace 3 heats coal and water to 600 - 1100 °C under a pressure of 0.3 - 23.4 Mpa to carry out a chemical reaction to generate syngas. When the pressure is 4 Mpa and the temperature is 630 - 670 °C, the maximum H2 component is obtained under the condition of appropriate operating costs; the fuel of the steam boiler 4 can be other solid, liquid, or gas fuels in addition to coal. Through a suitable burner and a supporting combustion control system, full-oxygen diffusion combustion or oxygen-enriched combustion with flue gas recirculation can be adopted to prevent N2 from entering the combustion. Compared with conventional combustion, the flue gas volume is reduced by 72% - 75%. It has been proved by experiments that using pure oxygen diffusion combustion reduces the fuel by about 6.28% and the flue gas volume by about 75% compared with conventional combustion. The present invention uses fuels such as coal, syngas after separating H2, and coal cinder, and uses a fan 5 to draw the flue gas for circulation. The furnace temperature in the steam boiler 4 is basically the same as that of a conventional steam boiler, but more uniform; the steam generator 6 uses a condensing extraction steam generator, and steam can be extracted from a suitable pressure section for other steam demands, and steam from other sources can also be injected into the steam system at an appropriate position; the exhausted steam after power generation recovers heat using circulating water in the condenser 19.

[0080] The flue gas of the steam boiler 4 is reduced to 110 °C after passing through the low-temperature economizer, enters the spray tower 8 after removing most of the dust through the dust collector 7, the spray water washes down the dust, water vapor, heavy metals, etc. in the flue gas, and reduces the flue gas temperature to 40 °C, and is discharged to the SO2 absorption tower 11 after passing through the demister. The washing water is sent to the ultrasonic electrocoagulation device 17 for treatment. The spray water comes from the heat pump 18, and the drainage of the steam boiler 4 is sent to the ultrasonic electrocoagulation device 17 for treatment after recovering heat through the heat pump 18.

[0081] The ultrasonic electrocoagulation device 17 collects the sewage generated in each process such as the washing water and the drainage of the steam boiler 4 after recovering heat. After flocculation and solid-liquid separation, part of the separated water is used as spray water after recovering heat through the heat pump 18, and part of it is heated to 95 - 99 °C through the heat pump 18 and then treated by the MVC9 to be boiler make-up water. The concentrated water generated by the treatment is used as gasification module water; all the generated sludge goes to the solid slag treatment module 10.

[0082] The solid slag treatment module 10 uses a plasma furnace to instantly heat the feed to 1200℃-2000℃. The organic components are thermally cracked and then reformed into small molecules of CO, H2, CH4, CO2, etc. by the steam generated by the high temperature; other inorganic substances are melted, and the liquid inorganic components are discharged from the plasma furnace. After the metal is recovered, it becomes a glass body, which can be used as a product or a raw material for advanced environmentally friendly building materials.

[0083] The SO2 absorption tower 11 brings the flue gas and the SO2 absorption liquid into reverse contact in the absorption tower, SO2 is absorbed, and the remaining CO2 is discharged from the top of the tower to the CO2 absorption tower. The absorption liquid rich in SO2 is heated by heat exchange with the absorption liquid containing very little SO2 after regeneration in the first heat exchanger 21 and then goes to the SO2 desorption tower 20 to desorb SO2. The SO2 on the top of the tower is compressed and liquefied by the SO2 compressor 23 and stored in liquid form. The regenerated absorption liquid is cooled from the bottom of the tower by the first heat exchanger 21 and then goes to the top of the SO2 absorption tower 11 for recycling.

[0084] The CO2 absorption tower 12 brings the flue gas at the top of the SO2 absorption tower 11 into reverse contact with the CO2 absorption liquid in the absorption tower, CO2 is absorbed, and the remaining flue gas is discharged from the top of the tower to the chimney. The CO2-rich absorption liquid is heated by heat exchange with the absorption liquid containing very little CO2 after regeneration in the second heat exchanger 26 and then goes to the CO2 desorption tower 25 to desorb CO2. The CO2 at the top of the tower is liquefied by the CO2 compressor 28 and stored in liquid form. The regenerated absorption liquid is cooled from the bottom of the tower by the second heat exchanger 26 and then recycled to the top of the CO2 absorption tower 12.

[0085] The CO2 compressor 28 compresses the CO2 to above 5.8Mpa, cools it to below 20°C and turns it into liquid, and then removes impurities in the CO2 refining tower 29 before storage.

[0086] Advantageously, if the top gas of the SO2 absorption tower 11 contains more components besides CO2, it needs to enter the CO2 absorption tower 12, the CO2 analysis tower 25, the second heat exchanger 26 and the second reboiler 27 in sequence to recover and concentrate the CO2. If the CO2 concentration is very high, it can be directly sent to the CO2 compressor 28 for liquefaction, and then the non-condensable gas is discharged through the CO2 refining tower 29 to obtain pure liquid CO2.

[0087] The main process of the present invention includes the following:

[0088] 1. The air separation process will produce N2, O2, and Ar. O2 is mainly used to participate in the combustion and gasification of coal. N2 is used as a raw material for synthetic ammonia. The excess can be sold as a product. The content of N2 in the air accounts for 79%. Since N2 does not enter the furnace to participate in combustion, there is no NO X The flue gas emission is reduced by 75% compared with traditional combustion, which makes the subsequent flue gas treatment more convenient and improves the thermal efficiency;

[0089] 2. The process of direct coal combustion and combined combustion after partial coal gasification: Most of the coal enters the boiler for combustion, and the remaining part of the coal is gasified in the gasifier. The syngas (H2 + CO) produced by gasification is purified to obtain H2 (the excess hydrogen can be sold as a clean fuel for hydrogen fuel cells), and N2 separated from the air enters the ammonia synthesis unit to produce NH3. The remaining un-gasified coal and the syngas after dehydrogenation enter the boiler to participate in combustion;

[0090] 3. The process of sulfur dioxide recovery: The flue gas discharged from the boiler combustion is first dusted, then cooled in the water scrubbing tower. The cooled flue gas enters the SO2 absorption tower. The absorbent liquid and the flue gas are in countercurrent contact in the SO2 absorption tower. All the SO2 in the flue gas is absorbed. The flue gas without SO2 comes out from the top of the tower and is sent to the next process for treatment. The rich liquid containing SO2 comes out from the bottom of the tower and is pumped to the desorption tower to desorb SO2. The SO2 is further purified by compression and liquefaction. The lean absorbent liquid without SO2 returns to the absorption tower for recycling;

[0091] 4. The process of carbon dioxide recovery: The main component of the flue gas after SO2 removal is CO2. After compression, cooling and liquefaction, CO2 is purified and recovered; When the CO2 content in the flue gas is low, it first enters the CO2 absorption tower. The absorbent liquid and the flue gas are in countercurrent contact in the CO2 absorption tower. All the CO2 in the flue gas is absorbed. The flue gas without CO2 comes out from the top of the tower and is discharged from the chimney. The rich liquid containing CO2 comes out from the bottom of the tower and is pumped to the desorption tower to desorb CO2, and then compressed and liquefied;

[0092] 5. The process of chemical fertilizer production: NH3 produced by the ammonia synthesis unit and CO2 recovered by the carbon dioxide recovery unit enter the chemical fertilizer unit to produce NH4HCO3. NH3 produced by the ammonia synthesis unit and SO2 recovered by the sulfur dioxide recovery unit enter the chemical fertilizer unit to produce (NH4)2SO4; NH3, CO2, and SO2 are all in liquid state and can also be directly sold as products according to the market situation.

[0093] 6. The process of boiler steam power generation: The steam produced by the boiler drives the steam turbine to generate electricity. The exhausted steam after power generation is cooled and then recycled in the boiler;

[0094] 7. The process of water cycle utilization: The flue gas discharged from the boiler first enters the dust collector and then the washing tower. The flue gas is further dusted and the water and latent heat in it are recovered. The washing water is flocculated and separated by solid-liquid separation to remove suspended solids. The clarified water is recycled as spray water after the heat is recovered by the heat pump; The cooling water that has absorbed the latent heat of the exhausted steam after power generation is recycled after the heat is recovered by the heat pump; The heat pump uses the boiler blowdown water and steam to drive and produce 95°C hot water; The MVC device produces distilled water from the 95°C hot water as boiler feed water; The excess water is treated to meet the standards for other uses.

[0095] 8. During the solid slag treatment process, fly ash and sludge are fed into a plasma furnace to recover heavy metals at high temperatures, and the rest forms a vitreous body. The vitreous body and the slag generated by the boiler can be used to produce building materials for sale.

[0096] All products of the present invention can be utilized. Except for normal water and nitrogen losses, almost no waste is discharged. Therefore, the technical problems of energy conservation and environmental protection such as resource-based clean emission of waste in coal-fired power plants are solved, and the effects of high efficiency and low cost are achieved. The resource-based clean emission system of this embodiment can recombine each module as needed to be applicable to coal-fired power plants, oil-fired power plants, gas-fired power plants, and waste treatment power plants.

[0097] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0098] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A resource-based clean emission system for a coal-fired power plant, characterized in that, Including: An air separation module for filtering dust and impurities in the air and separating out O2, N2, and Ar; A gasification module connected to the air separation module for subjecting water, coal, and the O2 separated by the air separation module to a gasification reaction at high temperature to produce syngas and coal slag; A dehydrogenation module connected to the gasification module for separating and purifying the syngas to obtain H2; A steam power generation module connected to the air separation module and the gasification module respectively for adding the coal slag, coal, and the syngas after separating H2, the O2 separated by the air separation module, or the recycled flue gas plus oxygen to burn and generate ultra-supercritical or high, medium, and low-pressure steam to drive a steam generator to generate electricity; An ammonia synthesis module connected to the air separation module and the dehydrogenation module respectively for generating NH3 from the purified H2 and the separated N2 under high temperature, high pressure, and the action of a catalyst; A flue gas washing module for preliminarily treating the flue gas after fuel combustion in the steam power generation module, removing dust and heavy metals in the flue gas, and recovering the moisture and heat therein; A gas recovery module for obtaining pure liquid SO2 and CO2 from the washed flue gas by solvent absorption, desorption, and compression liquefaction; A water treatment module for treating the sewage generated by flue gas washing, the drainage of the steam power generation module, and the sewage generated in other processes in the system into system circulating water or reclaimed water meeting the discharge standard; The flue gas washing module includes: a spray tower and a purification and washing device located in the spray tower. The spray tower transfers the soot, heavy metals, and heat in the flue gas to the washing water, and the purification and washing device discharges the washed and purified flue gas from the top of the tower, controlling the flue gas temperature at 38 - 42°C, and the washed sewage is sent to the water treatment module from the bottom of the tower; The water treatment module includes: an ultrasonic electrocoagulation device for flocculating most of the suspended substances and ions in the sewage; a solid-liquid separator for separating the flocculates in the sewage to form sludge; a heat pump for extracting most of the low-temperature water heat from the blowdown water and a small amount of steam of the steam boiler and heating a part of the low-temperature water to 95 - 99°C; an MVC device for treating the 95 - 99°C hot water by a mechanical evaporation and condensation process into distilled water as boiler make-up water, the concentrated water as water slurry water, and the low-temperature water from which heat is extracted as low-temperature water for spray; A solid residue treatment module communicating with the flue gas washing module and the steam power generation module respectively for recovering heavy metals from the sludge separated from the sewage and the solid particles in the soot and coal ash at high temperature, and processing the remaining into glass bodies.

2. The resource-based clean emission system for a coal-fired power plant according to claim 1, characterized in that, Using coal and its gasification products as fuel, using pure oxygen, or pure oxygen mixed with a certain proportion of recycled flue gas as a combustion aid, with less flue gas emissions and no nitrogen oxides.

3. The resource-based clean emission system for a coal-fired power plant according to claim 1, characterized in that, The steam generator is any one of supercritical, fully condensing, extraction condensing, and back pressure types.

4. The resource-based clean emission system for a coal-fired power plant according to claim 1, characterized in that, The dehydrogenation module includes: a membrane separator, only H2 in the syngas passes through the ceramic membrane of the membrane separator, and other components in the syngas are sent to the steam boiler of the steam power generation module for combustion; a compressor, the compressor is connected to the membrane separator and is used to compress the separated H2 to 30 - 35 MPa for output storage.

5. The resource-based clean emission system for a coal-fired power plant according to claim 1, characterized in that, The ammonia synthesis module includes: an ammonia synthesis reaction tower, the N2 and H2 are introduced into the ammonia synthesis reaction tower in a ratio of 1:2.8 - 2.9, the pressure in the reaction tower is controlled at 30 - 35 Mpa, and the temperature is 450 - 550 °C to synthesize NH3; a refrigerator, cools the NH3 discharged from the outlet of the reaction tower to 20 - 35 °C, and then stores it under the condition of a pressure of 1.6 - 1.8 Mpa.

6. A resource-based clean emission method for a coal-fired power plant, characterized in that, Using the resource-based clean emission system of a coal-fired power plant according to any one of claims 1 - 5, comprising the following steps: S1: Separating air through an air separation module to obtain N2, O2, and Ar; S2: Utilizing the separated O2, coal, and water to undergo a gasification reaction under high-temperature conditions in the gasification module to obtain syngas and coal slag; S3: The syngas is separated and purified through the dehydrogenation module to obtain pure H2, and other remaining gases in the syngas except H2 are directly sent to the steam boiler for combustion; S4: Synthesizing NH3 from the purified H2 and N2 separated from air in the ammonia synthesis module; S5: Burning coal, coal slag, and syngas in the steam boiler, heating water to generate steam to drive a steam turbine for power generation; S6: Washing and treating the flue gas discharged after combustion in the steam boiler through a flue gas washing module to remove dust, and recovering water and heat in the flue gas; S7: Recovering SO2 and CO2 in the cooled flue gas through a gas recovery module; S8: Treating the sewage generated by flue gas washing, the drainage of the steam boiler, and the sewage generated in other processes in the system through a water treatment module into system circulating water or reclaimed water meeting the discharge standard; S9: The solid residue treatment module treats coal ash, waste residue, and sludge, recovers heavy metals, and the remaining forms a vitreous body.

7. The resource-based clean emission method for a coal-fired power plant according to claim 6, characterized in that, In S8, it includes: cutting or pulverizing the sludge in soot, coal ash, and sewage into particles of 1 - 5 mm and feeding them into a plasma furnace.

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