Zero-carbon emission system for coal-fired power generation

Abstract

The utility model discloses a zero carbon emission system for coal-fired power generation, which belongs to the technical field of coal-fired power generation and comprises a pyrolysis reactor, an inlet of the pyrolysis reactor is connected with a pulverized coal source, an outlet of the pyrolysis reactor is connected with a gas-solid separation device, and the gas-solid separation device is provided with a solid outlet and a gas outlet. The solid outlet is connected with the pure oxygen combustion device; the pure oxygen combustion device is connected with the flue gas purification device; an outlet of the flue gas purification device is respectively connected with the methanol preparation device and the synthesis gas preparation device; the device further comprises a water electrolysis device, an oxygen outlet of the water electrolysis device is connected with an oxygen storage device, and an air outlet of the oxygen storage device is connected with the pure oxygen combustion device. Pulverized coal is pyrolyzed through the pyrolysis reactor to generate tar, coke breeze with the small nitrogen content and coal gas, the coke breeze, part of clean coal gas and pure oxygen are arranged in the pure oxygen combustion device to be combusted together, high-CO2-content flue gas is generated, the amount of nitric oxide in the flue gas is small, CO2 can be conveniently collected by the flue gas purification device, the system can be simplified, and the investment and operation cost is lower.

Description

TECHNICAL FIELD

[0001] The utility model belongs to coal-fired power generation technical field, concretely relates to a coal-fired power generation zero carbon emission system. BACKGROUND

[0002] The statements in this section merely provide background information related to the utility model and do not necessarily constitute prior art.

[0003] A large amount of flue gas is released in the coal combustion process, which contains polluting substances such as sulfur dioxide, nitrogen oxides, VOCs and heavy metals. In order to meet the increasingly stringent environmental emission requirements, large-scale implementation of coal-fired flue gas ultra-low emission technology. The conventional CO2 capture method for coal-fired flue gas is absorption, adsorption, membrane separation and low-temperature distillation method, among which the chemical absorption technology is the most mature and widely used, but the high investment, high energy consumption and complex process flow also make the CO2 capture cost very high.

[0004] Patents CN115624854A and CN114712989B respectively utilize the system and method of wet capture CO2 and desorption, which reduces the CO2 capture cost to a certain extent, but the process flow is still relatively complex; Patent CN114618259B discloses a method for separating gaseous CO2 from nitrogen by changing gaseous CO2 into liquid CO2 under low-temperature conditions, which greatly shortens the process flow, but it requires a large amount of energy to prepare a cold source to change gaseous CO2 into liquid or solid CO2, increasing the cost.

[0005] At present, the CO2 concentration of flue gas in coal-fired power plants is low, and contains a large amount of nitrogen, so the above-mentioned post-combustion carbon capture technology has the disadvantages of large system, high investment and operation cost; there is no zero carbon emission system based on the overall process technology of coal-fired power plants and coupled with energy storage-based operation optimization of coal-fired power plants. UTILITY MODEL CONTENTS

[0006] In view of the above problems, the utility model provides a coal-fired power generation zero carbon emission system, which sets up a pyrolysis reactor to pyrolyze coal powder, generate tar and powder coke with less nitrogen content, coal gas, and burns the powder coke together with part of the clean coal gas and pure oxygen in a pure oxygen combustion device, which can obtain flue gas with less nitrogen oxides and high CO2 content, facilitate the collection of CO2 by the flue gas purification device, simplify the system and reduce the investment and operation cost; the other part of the clean coal gas exchanges heat with the high-temperature flue gas of the pure oxygen combustion device, enters the pyrolysis reactor to pyrolyze coal powder, which can realize waste heat utilization of high-temperature flue gas and save external heating medium, without introducing too many gas impurities, thereby effectively ensuring the quality of the coal gas; and pure oxygen generated by electrolysis of water by low-valley electricity is supplied for powder coke combustion, and pure hydrogen and high-content CO2 collected by the flue gas purification device are used to make methanol, thereby realizing zero carbon emission.

[0007] To achieve the above object, the utility model takes the following technical scheme:

[0008] A coal-fired power generation zero carbon emission system, the import of pyrolysis reactor is connected with coal powder source, the outlet of pyrolysis reactor is connected with gas-solid separation device, and gas-solid separation device has solid outlet and gas outlet;

[0009] Solid outlet is connected with pure oxygen combustion device, pure oxygen combustion device is connected with flue gas purification device, and the outlet of flue gas purification device is connected with methanol preparation device and synthesis gas preparation device respectively.

[0010] It further includes electrolytic water device, and the oxygen outlet of electrolytic water device is connected with oxygen storage device, and the gas outlet of oxygen storage device is connected with pure oxygen combustion device.

[0011] Preferably, the gas-solid separation device includes cyclone separator, electrostatic precipitator and ceramic filter connected with each other, and the cyclone separator is connected with the outlet of the pyrolysis reactor.

[0012] Preferably, the gas outlet of the gas-solid separation device is connected with tar trapping device and coal gas purification device respectively.

[0013] Preferably, the outlet of the coal gas purification device is connected with the pyrolysis reactor and the pure oxygen combustion device respectively.

[0014] Preferably, the second heat exchanger is arranged between the coal gas purification device and the pyrolysis reactor, and the hydrogen purification device is arranged between the coal gas purification device and the pure oxygen combustion device.

[0015] Preferably, the coal gas purification device is connected with the cold medium channel of the second heat exchanger, one end of the hot medium channel of the second heat exchanger is connected with the first heat exchanger, and the other end is connected with the flue gas purification device.

[0016] Preferably, the first heat exchanger is arranged between the pure oxygen combustion device and the flue gas purification device.

[0017] Preferably, the hydrogen outlet of the electrolytic water device and the outlet of the hydrogen purification device are connected with the methanol preparation device.

[0018] Preferably, the electrolytic water device and the synthesis gas preparation device are powered by off-peak electricity.

[0019] Compared with the prior art, the utility model has the advantages and positive effects that:

[0020] The utility model discloses a pyrolysis reactor is set up to coal powder pyrolysis, and the tar and the nitrogen content less powder coke, coal gas are generated, and the powder coke is set in pure oxygen combustion device with part clean coal gas, pure oxygen and burns together, and the high content CO2 flue gas is generated, and the nitrogen oxides content in flue gas is little, and the CO2 of flue gas purification device is collected, can simplify the system and the investment and operation cost are lower, make another part clean coal gas and the high temperature flue gas heat exchange of pure oxygen combustion device, enter pyrolysis reactor and pyrolysis coal powder, can realize the waste heat utilization of high temperature flue gas, and can save the heating medium of outside import, will not introduce too many gas impurities, and then effectively guarantee the quality of coal gas, and, the utility model discloses pure oxygen is generated by low valley electricity electrolysis water and is supplied to powder coke combustion, and pure hydrogen and high content CO2 of flue gas purification device collection are made methanol, can realize zero carbon emission. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings accompanying the specification of this utility model form a part of the disclosure, serve to provide further understanding of the utility model, and together with the specification explain the utility model. The use of the same reference numerals in different drawings indicates similar or identical components.

[0022] Figure 1 It is the whole structure schematic diagram of the coal-fired power generation zero carbon emission system of the utility model embodiment;

[0023] In the drawings:

[0024] 1, pyrolysis reactor, 2, pure oxygen combustion device, 3, first heat exchanger, 4, flue gas purification device, 5, coal gas purification device, 6, tar trapping device, 7, second heat exchanger, 8, oxygen storage device, 9, hydrogen purification device, 10, electrolysis water device, 11, methanol preparation device, 12, synthesis gas preparation device, 13, gas-solid separation device. DETAILED DESCRIPTION

[0025] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the utility model. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as understood by one of ordinary skill in the art to which the utility model belongs.

[0026] The utility model discloses a pyrolysis reactor is set up to coal powder pyrolysis, and the tar and the nitrogen content less powder coke, coal gas are generated, and the powder coke is set in pure oxygen combustion device with part clean coal gas, pure oxygen and burns together, and the high content CO2 flue gas is generated, and the nitrogen oxides content in flue gas is little, and the CO2 of flue gas purification device is collected, can simplify the system and the investment and operation cost are lower, make another part clean coal gas and the high temperature flue gas heat exchange of pure oxygen combustion device, enter pyrolysis reactor and pyrolysis coal powder, can realize the waste heat utilization of high temperature flue gas, and can save the heating medium of outside import, will not introduce too many gas impurities, and then effectively guarantee the quality of coal gas, and, the utility model discloses pure oxygen is generated by low valley electricity electrolysis water and is supplied to powder coke combustion, and pure hydrogen and high content CO2 of flue gas purification device collection are made methanol, can realize zero carbon emission. Figure 1As shown, the system comprises a pyrolysis reactor 1, the inlet of the pyrolysis reactor 1 is connected with a coal powder source, the outlet of the pyrolysis reactor 1 is connected with a gas-solid separation device 13, the gas-solid separation device 13 has a solid outlet and a gas outlet. In the pyrolysis reactor 1, the coal powder is pyrolyzed to generate powder coke, coal gas and tar, and the gaseous coal gas, tar steam and the solid powder coke are separated by the gas-solid separation device. It can be understood that the gas-solid separation device 13 comprises a cyclone separator, an electrostatic precipitator and a ceramic filter which are connected with each other, wherein the cyclone separator is connected with the outlet of the pyrolysis reactor.

[0027] The flow of the pyrolysis of the coal powder: the raw coal is dried and separated by the existing power generation pulverizing system, and then enters the pyrolysis reactor 1, the coal powder is pyrolyzed, the pyrolysis temperature range is 400-600℃, and the pyrolysis reaction equation is: coal = CO2+ CO+ CH4+ H2+ C n H m + powder coke + tar + ΔH.

[0028] The gas-solid mixture in the pyrolysis reactor is separated by the gas-solid separation device, first, most of the powder coke is separated and removed by using the cyclone separator, then the finer particles are removed by using the electrostatic precipitator, and finally, the small amount of ultra-fine powder coke remaining in the crude coal gas is separated by using the special ultra-fine pore ceramic filter, so as to effectively improve the effect of the gas-solid separation and ensure the quality of the tar.

[0029] As shown in Figure 1 , the solid outlet of the gas-solid separation device is connected with a pure oxygen combustion device 2, and the separated powder coke is sent into the pure oxygen combustion device 2, and the powder coke is combusted in the pure oxygen combustion device to provide energy for power generation; the gas outlet of the gas-solid separation device is connected with a tar trapping device 6 and a coal gas purification device 5, respectively, the tar trapping device 6 is used to trap the tar, and the coal gas purification device 5 is used to purify the crude coal gas, so as to obtain clean coal gas and tar which have high utilization value.

[0030] It can be understood that the tar trapping device and the coal gas purification device are both prior art. The coal gas purification device mainly purifies the gaseous pollutants such as H2S, HCl, NH3 and HCN in the crude coal gas, and generally uses active coke or modified active coke to cooperatively remove various pollutants, and the main components of the clean coal gas after purification are CO, H2 and CH4. The clean coal gas can be combusted as fuel to generate power, or the hydrogen in the coal gas can be separated and stored for use; the tar has a high price and can be sold as a product, which can greatly reduce the cost of coal-fired power generation.

[0031] As shown in Figure 1As shown, the outlet of the coal gas purification device 5 is connected to the pyrolysis reactor 1 and the pure oxygen combustion device 2 respectively, wherein the second heat exchanger 7 is connected between the coal gas purification device 5 and the pyrolysis reactor 1, and the hydrogen purification device 9 is arranged between the coal gas purification device 5 and the pure oxygen combustion device 2.

[0032] As can be seen, a part of the clean coal gas purified by the coal gas purification device 5 will enter the pyrolysis reactor 1 again after heat exchange by the second heat exchanger 7, and participate in the pyrolysis process of the pulverized coal as a circulating heat source gas. The pulverized coke is pyrolyzed by the circulating coal gas, so that the heat in the coal gas can be fully utilized, and the external heating medium can be saved. This mode ensures that excessive gas impurities will not be introduced in the pyrolysis process, thereby effectively ensuring the quality of the coal gas. Another part of the clean coal gas is purified by the hydrogen purification device 9, and then enters the pure oxygen combustion device together with the high-temperature pulverized coke to generate power by combustion. The hydrogen purification device 9 can use the pressure swing adsorption method or the gas membrane separation technology to purify the hydrogen in the clean coal gas.

[0033] As shown in Figure 1 , the system further comprises an electrolytic water device 10, which is powered by off-peak electricity; the oxygen outlet of the electrolytic water device is connected to the oxygen storage device 8, and the gas outlet of the oxygen storage device 8 is connected to the pure oxygen combustion device 2. In the pure oxygen combustion device, the pulverized coke is relatively pure carbon, and the clean coal gas after purification and purification contains carbon monoxide, a small amount of hydrogen and methane. When mixed and combusted, the combustion chemical reaction equation is: CO + O2 = CO2; C + O2 = CO2; H2 + O2 = H2O; CH4 + O2 = CO2 + H2O. The combustion process can release a large amount of heat and produce high-content CO2 flue gas; since the impurities in the pulverized coke are few, most of the flue gas is CO2, and the contents of nitrogen oxides and sulfur dioxide are very small, and a small amount of ash may be contained.

[0034] As shown in Figure 1 , the pure oxygen combustion device 2 is connected to the flue gas purification device 4 through the first heat exchanger 3, the high-temperature flue gas is cooled by the first heat exchanger 3 to obtain low-temperature flue gas, and the low-temperature flue gas enters the flue gas purification device 4 for purification and purification to obtain high-concentration CO2.

[0035] In the embodiment, the flue gas purification device 4 uses the pollutant integrated purification technology to remove the fly ash, trace SOx, trace NOx and other pollutants in the flue gas, and obtain high-concentration CO2 flue gas. Specifically, because the flue gas contains low-content SO2, NOx and other acid gases, and particulates such as fly ash, the particulates in the flue gas are first removed by using an electrostatic precipitator, and then the acid gases are removed by using the calcium carbonate / calcium oxide semi-dry method. Because the pollutant content in the low-temperature flue gas is low, the disposal cost is much lower than that in the existing desulfurization and denitrification technology, and there is no secondary pollution of desulfurization wastewater. Therefore, the flue gas formed by the composition is easier to treat, and the flue gas treatment cost can be greatly reduced; and because the CO2 concentration is high, high-purity CO2 can also be obtained by using the existing compression liquefaction-low-temperature rectification technology.

[0036] As shown in Figure 1 In the embodiment, the coal gas purification device 5 is connected with the cold medium channel of the second heat exchanger 7, and the hot medium channel of the second heat exchanger 7 can use the low-temperature flue gas waste heat of the first heat exchanger 3 to heat the clean coal gas passing through the second heat exchanger 7. Because the flue gas generated in the combustion process of pure oxygen and pulverized coke has a very high temperature, the temperature range is 1000-1500°C, and the clean coal gas cannot be directly heated, but the low-temperature flue gas after being cooled by the first heat exchanger 3 has a temperature range of 400-700°C, and can be directly heated with the purified coal gas. The heated coal gas is introduced into the pyrolysis reactor to pyrolyze the coal powder, and the waste heat of the flue gas can be utilized.

[0037] It can be understood that one end of the hot medium channel of the second heat exchanger 7 can be connected with the first heat exchanger 3, and the other end can be connected with the flue gas purification device 4, and the clean coal gas can be heated by using the low-temperature flue gas after being partially cooled. Because the flue gas of the pure oxygen combustion device 2 has a very high temperature, which is much higher than the temperature requirement in the pyrolysis reactor, the flue gas cannot be directly used to heat the clean coal gas. The low-temperature flue gas after being cooled by the first heat exchanger 3 can heat the clean coal gas. The low-temperature flue gas after being partially cooled first enters the hot medium channel of the second heat exchanger 7, is heated by the second heat exchanger 7, and then enters the flue gas purification device 4 to be cooled. The main purpose is to maintain the temperature of the regenerated circulating coal gas to meet the heat demand of the pyrolysis reactor 1, and maintain the pyrolysis reaction temperature in the range of 400-600°C.

[0038] As shown in Figure 1 The hydrogen outlet of the water electrolysis device 10, the outlet of the flue gas purification device 4 and the outlet of the hydrogen purification device 9 are all connected with the methanol production device 11. The methanol production device uses the existing technology. In the methanol production device, the electrolytic hydrogen and the hydrogen purified from the clean coal gas react with high-purity CO2 to generate methanol, and the resource utilization of CO2 can be realized.

[0039] The outlet of the flue gas purification device 4 is connected not only to the methanol production unit 11, but also to the syngas preparation unit 12, which is powered by off-peak electricity. It is understood that the syngas preparation unit 12 uses existing technology. There are two main existing technologies for preparing syngas from carbon dioxide: one is the electrocatalytic reduction of carbon dioxide using an aqueous solution, and the other is CH4-CO2 dry reforming technology.

[0040] Methanol can be prepared by using hydrogen obtained from the electrolysis of water with high-purity CO2 and off-peak electricity and the hydrogen separated from coal gas, or by using high-purity CO2 to prepare syngas in the syngas preparation unit 12. This can achieve zero carbon emissions, effectively improve the utilization rate of CO2 in flue gas, realize the resource utilization of CO2, effectively alleviate the greenhouse effect, and utilize off-peak electricity, thereby improving the operational flexibility of coal-fired power plants.

[0041] The process flow of a zero-emission coal-fired power generation system includes the following steps:

[0042] Powdered coal is rapidly pyrolyzed in a pyrolysis reactor at a temperature of 400-600℃ for 3-10 seconds. The pyrolysis products are then subjected to gas-solid separation and tar capture to obtain coal gas, tar, and pulverized coke.

[0043] After purification, part of the coal gas is purified into hydrogen and then sent to a pure oxygen combustion device along with the pulverized coke for combustion with pure oxygen; the other part is heated by exchanging heat with the flue gas and then enters a pyrolysis reactor to pyrolyze the pulverized coal.

[0044] Oxygen and hydrogen are produced by electrolyzing water using off-peak electricity. The electrolyzed oxygen is used to generate electricity by burning pulverized coke; the electrolyzed hydrogen, along with hydrogen extracted from coal gas, is transported to methanol production unit 11.

[0045] The flue gas from the combustion of coke, coal gas, and pure oxygen for power generation is purified by heat exchange to obtain high-concentration CO2 gas. The high-concentration CO2 gas is then transported to the methanol production unit 11 to produce methanol with hydrogen, or to the syngas production unit 12 to produce syngas.

[0046] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. A zero-carbon emission system for coal-fired power generation, characterized by, The pyrolysis reactor is connected with a coal powder source at an inlet thereof, and is connected with a gas-solid separation device at an outlet thereof, the gas-solid separation device having a solid outlet and a gas outlet; The solid outlet is connected with a pure oxygen combustion device, and in the pure oxygen combustion device, pulverized coke is mixed with cleaned coal gas after purification and combustion, a large amount of heat is released during the combustion process, and high-content CO2 flue gas is generated; the pure oxygen combustion device is connected with a flue gas purification device, and the outlet of the flue gas purification device is connected with a methanol production device and a synthesis gas preparation device respectively; The water electrolysis device is also provided, and the oxygen outlet of the water electrolysis device is connected with an oxygen storage device, the gas outlet of the oxygen storage device is connected with the pure oxygen combustion device, the hydrogen outlet of the water electrolysis device and the outlet of a hydrogen purification device are connected with the methanol production device, and the water electrolysis device and the synthesis gas preparation device are powered by off-peak electricity.

2. A zero-carbon emission system for coal-fired power generation as claimed in claim 1 wherein, The gas-solid separation device comprises a cyclone separator, an electrostatic precipitator and a ceramic filter connected with each other, and the cyclone separator is connected with the outlet of the pyrolysis reactor.

3. A zero-carbon emission system for coal-fired power generation as claimed in claim 1 wherein, The gas outlet of the gas-solid separation device is connected with a tar trapping device and a coal gas purification device respectively.

4. A zero-carbon emission system for coal-fired power generation as claimed in claim 3 wherein, The outlet of the coal gas purification device is connected with the pyrolysis reactor and the pure oxygen combustion device respectively.

5. A zero-carbon emission system for coal-fired power generation as claimed in claim 3 wherein, A second heat exchanger is arranged between the coal gas purification device and the pyrolysis reactor, and a hydrogen purification device is arranged between the coal gas purification device and the pure oxygen combustion device.

6. A zero-carbon emission system for coal-fired power generation as claimed in claim 5 wherein, The coal gas purification device is connected with the cold medium channel of the second heat exchanger, one end of the hot medium channel of the second heat exchanger is connected with a first heat exchanger, and the other end is connected with a flue gas purification device.

7. A zero-carbon emission system for coal-fired power generation as claimed in claim 6 wherein, The first heat exchanger is arranged between the pure oxygen combustion device and the flue gas purification device.

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