System and method for carbon capture after combustion of coal-fired power plant

Abstract

The invention relates to the technical field of coal-fired power generation, and discloses a system and a method for carbon capture after combustion of a coal-fired power plant. The system comprises a boiler, a decarburization reactor, a calcium carbonate storage device, a solar auxiliary regeneration reactor, a calcium oxide storage device, a steam turbine, a condenser and a condensed water heater, flue gas from the boiler enters the decarburization reactor for decarburization; the decarburization reactor, the calcium carbonate storage device, the solar auxiliary regeneration reactor and the calcium oxide storage device are sequentially connected end to end; steam exhausted by the steam turbine after expansion acting enters the condenser to be condensed into water, part of condensed water exchanges heat with decarburized flue gas from the decarburization reactor in the condensed water heater, and the heated condensed water enters the high-temperature heating surface to be heated into steam for expansion acting on the steam turbine. According to the system, efficient utilization of solar energy and CaO chemical energy can be achieved, fossil energy consumption is reduced, and the system is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, and in particular to a system and method for post-combustion carbon capture in a coal-fired power plant. Background Art

[0002] Large amounts of CO2 emissions are the main cause of the greenhouse effect. As a major carbon emitter, it is particularly important to reduce carbon emissions from coal-fired power generation. At present, carbon capture and storage technology is one of the important ways to achieve carbon emission reduction in large-scale coal-fired power plants. There are three main methods of carbon capture: pre-combustion capture, oxygen-enriched combustion, and post-combustion capture. Among them, post-combustion capture is currently the most feasible method of carbon capture because it has been commercialized in industry and the degree of modification of power plants is relatively low when it is integrated with coal-fired power plants. Generally, chemical absorption is one of the important methods of post-combustion capture. Since CO2 desorption requires a large amount of low-pressure extraction steam to provide heat, the energy consumption of decarbonization is high, which seriously limits its large-scale application.

[0003] Calcium circulation technology uses the carbonation / calcination reaction of CaO to capture CO2. It has the advantages of low cost, simple process and high efficiency, and is considered to be one of the promising large-scale decarbonization technologies. The calcination reaction of CaO is a strong endothermic reaction. The calcination furnace generally uses oxygen-enriched combustion of fuel to provide the energy required for the decomposition of CaCO3. However, this method not only increases the consumption of fossil fuels, but also requires the deployment of air separation oxygen production equipment, which increases the complexity of the system and investment costs.

[0004] Using solar energy to provide the energy required for CaCO3 decomposition can reduce dependence on fossil energy and reduce system complexity. However, how to use fluctuating solar resources to achieve stable CO2 capture is a difficult problem in current research. In addition, during the process of CaO adsorbing CO2, CaO converts its chemical energy into thermal energy of flue gas. This process is a highly exothermic process. How to effectively recover and utilize this part of heat is also a difficulty in current research. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems in the prior art that the calcium circulation technology cannot fully utilize solar energy resources and the heat released during the adsorption of CO2 by CaO cannot be effectively recovered and utilized, and to provide a system and method for post-combustion carbon capture in a coal-fired power plant. The system can achieve efficient utilization of solar energy and CaO chemical energy, reduce fossil energy consumption, and the system is relatively simple.

[0006] In order to achieve the above-mentioned object, the present invention provides a system for post-combustion carbon capture in a coal-fired power plant, the system comprising a boiler, a decarbonization reactor, a calcium carbonate storage device, a solar-assisted regeneration reactor, a calcium oxide storage device, a steam turbine, a condenser and a condensate heater;

[0007] A high-temperature heating surface and a low-temperature heating surface are sequentially arranged in the boiler along the direction of flue gas flow;

[0008] The flue gas from the boiler enters the decarbonization reactor for decarbonization;

[0009] The decarbonization reactor, the calcium carbonate storage device, the solar-assisted regeneration reactor and the calcium oxide storage device are connected end to end in sequence, the solar-assisted regeneration reactor is used for the decomposition reaction of calcium carbonate, and the heat of the reaction comes from solar energy;

[0010] The exhaust steam of the steam turbine after expansion and work of the steam turbine enters the condenser and condenses into water. Part of the condensed water from the condenser and the decarbonized flue gas from the decarbonization reactor undergo heat exchange in the condensate heater. The heated condensed water enters the high-temperature heating surface for heating, and the formed steam is used to expand the steam turbine and do work.

[0011] Preferably, the system further comprises a solar concentrating and heat collecting system for collecting solar energy and providing heat for decomposing calcium carbonate into calcium oxide in the solar-assisted regeneration reactor.

[0012] Preferably, the system further comprises a first heater, a deaerator and a second heater connected in sequence;

[0013] Another part of the condensate from the condenser enters the first heater, the deaerator and the second heater in sequence for heating, and then enters the low-temperature heating surface for heating, and then merges with the condensate heated in the condensate heater and enters the high-temperature heating surface to be heated into steam for expansion work on the steam turbine.

[0014] Preferably, extraction steam from the steam turbine enters the first heater, the deaerator and the second heater respectively through an extraction steam pipeline to provide a heat source.

[0015] Preferably, a water feed pump is provided between the deaerator and the second heater for inputting the condensed water treated by the deaerator into the second heater.

[0016] Preferably, a dust collector and a desulfurization tower are sequentially arranged between the boiler and the decarbonization reactor along the flue gas flow direction;

[0017] The flue gas from the boiler enters the dust collector and the desulfurization tower in sequence for treatment and then enters the decarbonization reactor for decarbonization.

[0018] A second aspect of the present invention provides a method for post-combustion carbon capture in a coal-fired power plant. The method is implemented in the system described above and comprises the following steps:

[0019] S1. Pass the flue gas in the boiler into the decarbonization reactor, input the calcium oxide in the calcium oxide storage device into the decarbonization reactor, and react the flue gas with the calcium oxide to obtain decarbonized flue gas and calcium carbonate, and the calcium carbonate is stored in the calcium carbonate storage device;

[0020] S2. When solar energy is sufficient, the calcium carbonate in the calcium carbonate storage device is input into the solar-assisted regeneration reactor for reaction, and the obtained calcium oxide is stored in the calcium oxide storage device and input into the decarbonization reactor for recycling;

[0021] S3, passing the decarbonized flue gas into a condensate heater to heat part of the condensate formed by the exhaust steam of the turbine in the condenser, and then passing the heated condensate into the high-temperature heating surface for heating, and the obtained steam returns to the turbine to expand and do work.

[0022] Preferably, the reaction temperature of the decarbonization reactor is 700-900°C.

[0023] Preferably, the reaction temperature of the solar-assisted regeneration reactor is 800-1000°C.

[0024] Preferably, the method also includes: inputting another part of condensate formed by the exhaust steam of the turbine in the condenser into the first heater, the deaerator and the second heater in sequence for heating, and then inputting it into the low-temperature heating surface for heating, and then merging it with the condensate heated in the condensate heater and inputting it into the high-temperature heating surface to be heated into steam for expanding the turbine.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) Using solar energy instead of coal-fired oxygen-enriched combustion to provide the heat required for CaCO3 decomposition reduces the system's fossil energy consumption and carbon emissions;

[0027] (2) When solar energy resources are abundant, the CaCO3 stored in the calcium carbonate storage device is sent to the solar-assisted regeneration reactor for decomposition reaction. When CaCO3 decomposes, it absorbs solar energy to obtain CaO. The excess solar energy can be stored in the form of CaO chemical energy. Because solid storage is simple and the thermochemical energy storage density is high, it can be achieved by only arranging a CaO storage device, which greatly simplifies the layout of the solar thermal storage system.

[0028] (3) By arranging a condensate heater, a large amount of medium and low temperature flue gas waste heat generated in the decarbonization reactor can be transferred to the condensate of the heat recovery system to replace the heat recovery extraction steam to heat the condensate, and more steam enters the turbine to expand and do work, which can greatly improve the energy efficiency of the power plant. According to calculations, taking a 1000MW coal-fired unit as an example, when the carbon capture rate is 90%, the heat for CaCO3 decomposition is provided only by the concentrating solar collector system, and the power generation efficiency of the coal-fired unit drops from 45.5% to 32.9%, a decrease of up to 12.6 percentage points. When the efficient waste heat recovery scheme proposed by the present invention is adopted, the power generation efficiency of the coal-fired unit when the carbon capture rate is 90% is reduced from 45.5% to 42.8%, which is much higher than the existing coal-fired power plant carbon capture process, and the solar thermal power conversion efficiency is as high as 36.0%, which shows that the technical scheme proposed by the present invention can significantly improve the energy efficiency of the decarbonization unit and realize the efficient utilization of solar thermal energy and CaO chemical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a system for post-combustion carbon capture in a coal-fired power plant according to the present invention.

[0030] Description of Reference Numerals

[0031] 1 boiler; 2 decarbonization reactor; 3 calcium carbonate storage device; 4 solar-assisted regeneration reactor; 5 calcium oxide storage device; 6 steam turbine; 7 condenser; 8 condensate heater; 9 high-temperature heating surface; 10 low-temperature heating surface; 11 solar concentrating collector system; 12 first heater; 13 deaerator; 14 second heater; 15 feed water pump; 16 dust collector; 17 desulfurization tower; steam extraction pipeline. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0033] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0034] The system for post-combustion carbon capture in a coal-fired power plant provided by the present invention is as follows: Figure 1As shown, it includes a boiler 1, a decarbonization reactor 2, a calcium carbonate storage device 3, a solar-assisted regeneration reactor 4, a calcium oxide storage device 5, a steam turbine 6, a condenser 7 and a condensate heater 8. In the system, a high-temperature heating surface 9 and a low-temperature heating surface 10 are sequentially arranged in the boiler 1 along the flue gas flow direction; the flue gas from the boiler 1 enters the decarbonization reactor 2 for decarbonization; the decarbonization reactor 2, the calcium carbonate storage device 3, the solar-assisted regeneration reactor 4 and the calcium oxide storage device 5 are sequentially connected end to end, the solar-assisted regeneration reactor 4 is used for the decomposition reaction of calcium carbonate, and the heat for the reaction comes from solar energy; the steam turbine exhaust steam after the steam turbine 6 expands and does work enters the condenser 7 to condense into water, and part of the condensate from the condenser 7 is heat-exchanged with the decarbonized flue gas from the decarbonization reactor 2 in the condensate heater 8, and the heated condensate enters the high-temperature heating surface 9 for heating, and the formed steam is used to expand the steam turbine 6 to do work.

[0035] In the present invention, the high-temperature heating surface 9 and the low-temperature heating surface 10 are heat exchangers arranged in the boiler 1. High-temperature heating surface and low-temperature heating surface are common terms in this field. The high-temperature heating surface uses high-temperature flue gas to heat steam to produce steam with higher parameters, and the low-temperature heating surface uses low-temperature flue gas to heat water to produce steam. The difference between the two is that there is a difference in the absorption / release temperature of the cold and hot working fluids.

[0036] In one embodiment, the flue gas outlet of the condensate heater 8 is connected to the atmosphere, and the decarbonized flue gas of the decarbonization reactor 2 can be directly discharged into the atmosphere after heating the condensate in the condensate heater 8.

[0037] In the system described in the present invention, the flue gas generated by the combustion of the boiler 1 enters the decarbonization reactor 2 from the flue gas outlet of the boiler 1, and the calcium oxide stored in the calcium oxide storage device 5 is also sent to the decarbonization reactor 2. The carbon dioxide in the flue gas reacts with the calcium oxide, and the generated calcium carbonate is stored in the calcium carbonate storage device 3. When the solar energy is sufficient, the solar energy-assisted regeneration reactor 4 starts to work, and the CaCO3 in the calcium carbonate storage device 3 enters the solar energy-assisted regeneration reactor 4 and absorbs solar heat to decompose CaCO3. The CaO generated by the decomposition enters the calcium oxide storage device 5 for storage. In this process, CaCO3 absorbs solar energy to obtain CaO when it decomposes, and the excess solar energy can be stored in the form of CaO chemical energy. Because solid storage is simple and the thermochemical energy storage density is high, it can be achieved by only arranging a CaO storage device. , which greatly simplifies the layout of the solar thermal storage system. When it is necessary to adsorb carbon dioxide in the flue gas, the calcium oxide in the calcium oxide storage device 5 is introduced into the decarbonization reactor 2. In this way, the efficient utilization of solar energy and CaO chemical energy is achieved, and the carbon dioxide obtained after the decomposition of calcium carbonate in the solar-assisted regeneration reactor 4 can be captured in a conventional manner or collected for utilization; at the same time, after the carbon dioxide in the flue gas in the decarbonization reactor 2 is absorbed and reacted by CaO, the decarbonized flue gas obtained is a medium-low temperature flue gas of about 600°C. The medium-low temperature flue gas is introduced into the condensate heater 8 to heat part of the condensate from the condenser 7, thereby effectively utilizing the waste heat of the medium-low temperature flue gas. The condensate heated by the medium-low temperature flue gas enters the high-temperature heating surface 9 and is heated into steam, which is used to expand the steam turbine 6 to do work.

[0038] In a preferred embodiment, the system also includes a solar concentrating and collecting system 11, which is used to collect solar energy and provide heat for decomposing calcium carbonate in the solar-assisted regeneration reactor 4 into calcium oxide. That is, the solar energy used to provide heat for the reaction of the solar-assisted regeneration reactor 4 passes through the solar concentrating and collecting system 11, thereby reducing the system's fossil energy consumption and carbon emissions.

[0039] In another preferred embodiment, after the condensate is divided into two streams and before entering the condensate heater 8, the flow rate of the condensate entering the condensate heater 8 is regulated by controlling the opening of the regulating valve so as to heat the condensate to a temperature close to the saturation temperature.

[0040] In one embodiment, a dust collector 16 and a desulfurization tower 17 are sequentially arranged between the boiler 1 and the decarbonization reactor 2 along the flow direction of the flue gas; the flue gas from the boiler 1 enters the dust collector 16 and the desulfurization tower 17 in sequence for dust removal and desulfurization, and then enters the decarbonization reactor 2 for decarbonization treatment.

[0041] In the present invention, the calcium carbonate storage device 3 may be a calcium carbonate storage tank, and the calcium oxide storage device 5 may be a calcium oxide storage tank.

[0042] In one embodiment, Figure 1 As shown, the system of the present invention further includes a first heater 12, a deaerator 13 and a second heater 14 connected in sequence; another part of the condensate from the condenser 7 enters the first heater 12, the deaerator 13 and the second heater 14 in sequence for heating, then enters the low-temperature heating surface 10 for heating, and then merges with the condensate heated in the condensate heater 8 and enters the high-temperature heating surface 9 for heating into steam for expansion work on the steam turbine 6. The deaerator 13 can not only deoxygenate the condensate, but also heat the deaerator 13.

[0043] In a more specific embodiment, Figure 1 As shown, the extraction steam from the steam turbine 6 enters the first heater 12, the deaerator 13 and the second heater 14 through the extraction steam pipe 18 to provide a heat source, and enters the first heater 12, the deaerator 13 and the second heater 14 to heat the condensate and the feed water.

[0044] In the system described in the present invention, a condensate pump is provided downstream of the condenser 7. The condensate is divided into two streams after passing through the condensate pump. One stream is heat exchanged with the decarbonized flue gas from the decarbonization reactor 2 in the condensate heater 8 according to the aforementioned logistics. The heated condensate enters the high-temperature heating surface 9 to be heated into steam for expansion work of the steam turbine 6. The other stream enters the first heater 12, the deaerator 13 and the second heater 14 in sequence according to the aforementioned logistics, and then enters the low-temperature heating surface 10 for heating, and then merges with the condensate heated in the condensate heater 8 and enters the high-temperature heating surface 9 to be heated into steam for expansion work of the steam turbine 6.

[0045] In a preferred embodiment, a water supply pump 15 is provided between the deaerator 13 and the second heater 14 for increasing the pressure of the condensed water treated by the deaerator 13 and then feeding it into the second heater 14 .

[0046] In the present invention, the first heater 12 is a low-pressure heater, and the second heater 14 is a high-pressure heater. The high pressure and low pressure in the high-pressure heater and the low-pressure heater refer to the water pressure respectively, and the feed water pressure is greater than the condensate pressure. The heater used to heat the water from the condensate pump before entering the deaerator 16 is a low-pressure heater (first heater 12), and the water at the outlet of the feed water pump 15 enters the low-temperature heating surface after being heated by several stages of heaters. These several stages of heaters are high-pressure heaters (second heaters). The outlet pressures of the condensate pump and the feed water pump vary with the random group parameters.

[0047] In a more specific embodiment, Figure 1 As shown, the system includes a boiler 1, a decarbonization reactor 2, a calcium carbonate storage device 3, a solar-assisted regeneration reactor 4, a calcium oxide storage device 5, a steam turbine 6, a condenser 7, a condensate heater 8, a solar energy concentrating and collecting system 11, a first heater 12, a deaerator 13, a second heater 14, a feed water pump 15, a dust collector 16 and a desulfurization tower 17. A high-temperature heating surface 9 and a low-temperature heating surface 10 are sequentially arranged in the boiler 1 along the flow direction of flue gas. The solar energy concentrating and collecting system 11 is used to collect solar energy and provide heat for decomposing the calcium carbonate in the solar-assisted regeneration reactor 4 into calcium oxide. The feed water pump 15 is arranged between the deaerator 13 and the second heater 14. The dust collector 16 and the desulfurization tower 17 are sequentially arranged between the boiler 1 and the decarbonization reactor 2 along the flow direction of flue gas.

[0048] The flue gas from the boiler 1 enters the dust collector 16 and the desulfurization tower 17 in turn for treatment and then enters the decarbonization reactor 2. The calcium oxide stored in the calcium oxide storage device 5 is also sent to the decarbonization reactor 2. The carbon dioxide in the flue gas reacts with the calcium oxide. The reaction temperature of the decarbonization reactor 2 is 800°C. The generated calcium carbonate is stored in the calcium carbonate storage device 3. When the solar energy is sufficient, the solar-assisted regeneration reactor 4 starts to work. The CaCO3 in the calcium carbonate storage device 3 enters the solar-assisted regeneration reactor 4 and absorbs solar heat to decompose CaCO3. The reaction temperature of the solar-assisted regeneration reactor 4 is 900°C. The CaO generated by the decomposition enters the calcium oxide storage device 5 for storage. When it is necessary to adsorb the carbon dioxide in the flue gas, the calcium oxide in the calcium oxide storage device 5 is passed into the decarbonization reactor 2, and the cycle is repeated. The exhaust steam of the steam turbine 6 after expansion and work enters the condenser 7 to condense into water. A condensate pump is provided downstream of the condenser 7. The condensate is divided into two streams after passing through the condensate pump. After the carbon dioxide in the flue gas in the decarbonization reactor 2 is absorbed by CaO, the obtained decarbonized flue gas is a medium-low temperature flue gas of about 600°C. The medium-low temperature flue gas is passed into the condensate heater 8 to heat part of the condensate from the condenser 7. Before the condensate enters the condensate heater 8, the opening of the regulating valve is controlled to adjust the flow rate of the condensate entering the condensate heater 8 so that its temperature is heated to a temperature close to the saturation temperature. The condensate heated by the medium-low temperature flue gas enters the high-temperature heating surface 9 and is heated into steam. Another part of the condensate from the condenser 7 enters the first heater 12, the deaerator 13, the feed water pump 15 and the second heater 14 in sequence for heating, and then enters the low-temperature heating surface 10 for heating, and then merges with the condensate heated in the condensate heater 8 and enters the high-temperature heating surface 9 to be heated into steam for expansion work on the steam turbine 6. The extraction steam from the steam turbine 6 passes through the extraction pipe 18 and enters the first heater 12, the deaerator 13 and the second heater 14 respectively to provide a heat source.

[0049] In the system described in the present invention, by providing the calcium oxide storage device 5 and the calcium carbonate storage device 3, when solar energy is sufficient, the CaCO3 in the calcium carbonate storage device 3 can be introduced into the solar energy assisted regeneration reactor 4 to absorb solar heat to realize the decomposition of CaCO3, and the CaO produced by the decomposition enters the calcium oxide storage device 5 for storage. In this process, CaCO3 absorbs solar energy to obtain CaO when it decomposes. Not only can solar energy be used to replace oxygen-enriched combustion of coal to provide the heat required for the decomposition of CaCO3, thereby reducing the fossil energy consumption and carbon emissions of the system, but also sufficient solar energy can be stored in the form of CaO chemical energy. Since solid storage is simple and the thermochemical energy storage density is high, it can be achieved by only arranging a CaO storage device, which greatly simplifies the layout of the solar thermal storage system, thereby realizing the efficient utilization of solar energy and CaO chemical energy.

[0050] The prior art provides a first heater 12, a deaerator 13 and a second heater 14 connected in sequence; the extraction steam from the steam turbine 6 enters the first heater 12, the deaerator 13 and the second heater 14 through the extraction steam pipeline 18 to provide a heat source, and enters the first heater 12, the deaerator 13 and the second heater 14 to heat the condensate and the feed water respectively; the condensate heated by the first heater 12, the deaerator 13 and the second heater 14 enters the low-temperature heating surface 10 for heating, and then enters the high-temperature heating surface 9 is heated to steam for expansion and work on the steam turbine 6; the present invention adds a condensate heater 8, which divides the condensate from the condenser 7 into two parts, one part is passed into the condensate heater 8, and heat exchange is performed through the decarbonized flue gas from the decarbonization reactor 2. The heated condensate enters the high-temperature heating surface 9 and is heated to steam for expansion and work on the steam turbine 6. A large amount of medium and low temperature flue gas waste heat generated in the decarbonization reactor can be transferred to this part of the condensate to replace the heat recovery extraction steam to heat the condensate, and more steam enters the steam turbine to expand and do work, which can greatly improve the energy efficiency of the power plant.

[0051] The method for post-combustion carbon capture in a coal-fired power plant provided by the present invention is implemented in the system described above, and the method comprises the following steps:

[0052] S1, passing the flue gas in the boiler 1 into the decarbonization reactor 2, inputting the calcium oxide in the calcium oxide storage device 5 into the decarbonization reactor 2, allowing the flue gas to react with the calcium oxide to obtain decarbonized flue gas and calcium carbonate, and the calcium carbonate is stored in the calcium carbonate storage device 3;

[0053] S2. When solar energy is sufficient, the calcium carbonate in the calcium carbonate storage device 3 is input into the solar-assisted regeneration reactor 4 for reaction, and the obtained calcium oxide is stored in the calcium oxide storage device 5 and input into the decarbonization reactor 2 for recycling;

[0054] S3. Pass the decarbonized flue gas into the condensate heater 8 to heat part of the condensate formed by the turbine exhaust steam in the condenser 7, and then pass the heated condensate into the high-temperature heating surface 9 for heating, and the obtained steam returns to the turbine 6 to expand and do work.

[0055] In the method described in the present invention, the flue gas generated by the combustion of the boiler 1 is introduced into the decarbonization reactor 2 from the flue gas outlet of the boiler 1, and the calcium oxide stored in the calcium oxide storage device 5 is also sent to the decarbonization reactor 2. The carbon dioxide in the flue gas reacts with the calcium oxide, and the generated calcium carbonate is stored in the calcium carbonate storage device 3. When the solar energy is sufficient, the CaCO3 in the acid calcium storage device 3 is introduced into the solar energy assisted regeneration reactor 4 and absorbs solar heat to decompose CaCO3. The CaO generated by the decomposition enters the calcium oxide storage device 5 for storage. In this process, CaCO3 absorbs solar energy to obtain CaO when it decomposes, and the excess solar energy can be stored in the form of CaO chemical energy. Because solid storage is simple and the thermochemical energy storage density is high, it can be achieved by arranging a CaO storage device, which greatly simplifies The solar thermal storage system is arranged so that when it is necessary to absorb carbon dioxide in the flue gas, the calcium oxide in the calcium oxide storage device 5 is introduced into the decarbonization reactor 2, and the cycle is repeated to achieve efficient utilization of solar energy and CaO chemical energy, and the carbon dioxide obtained after the decomposition of calcium carbonate in the solar-assisted regeneration reactor 4 can be captured in a conventional manner or collected for utilization; at the same time, after the carbon dioxide in the flue gas in the decarbonization reactor 2 is absorbed and reacted by CaO, the decarbonized flue gas obtained is a medium-low temperature flue gas of about 600°C, and the medium-low temperature flue gas is introduced into the condensate heater 8 to heat part of the condensate from the condenser 7, thereby effectively utilizing the waste heat of the medium-low temperature flue gas, and the condensate after being heated by the medium-low temperature flue gas enters the high-temperature heating surface 9 and is heated into steam, and the steam is used to expand the steam turbine 6 to do work.

[0056] In a preferred embodiment, in order to improve the utilization rate of CaO chemical energy and obtain medium-low temperature decarbonized flue gas of suitable temperature, the reaction temperature of the decarbonization reactor 2 is 700-900°C, more preferably 800°C.

[0057] In another preferred embodiment, in order to improve the utilization rate of solar energy, the reaction temperature of the solar-assisted regeneration reactor 4 is 800-1000°C, more preferably 900°C.

[0058] In one embodiment, the method further includes: inputting another part of condensate formed by the exhaust steam of the steam turbine in the condenser 7 into the first heater 12, the deaerator 13 and the second heater 14 in sequence for heating, and then inputting it into the low-temperature heating surface 10 for heating, and then merging it with the condensate heated in the condensate heater 8 and inputting it into the high-temperature heating surface 9 to be heated into steam for expansion work on the steam turbine 6.

[0059] The following examples further illustrate the system and method for post-combustion carbon capture in coal-fired power plants of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0060] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0061] The following examples and comparative examples were implemented in a 1000MW coal-fired unit.

[0062] Example

[0063] The embodiments of the present invention are as follows Figure 1 The system shown in the figure comprises a boiler 1, a decarbonization reactor 2, a calcium carbonate storage device 3, a solar-assisted regeneration reactor 4, a calcium oxide storage device 5, a steam turbine 6, a condenser 7, a condensate heater 8, a solar energy concentrating and collecting system 11, a first heater 12, a deaerator 13, a second heater 14, a feed water pump 15, a dust collector 16 and a desulfurization tower 17. A high-temperature heating surface 9 and a low-temperature heating surface 10 are sequentially arranged in the boiler 1 along the flue gas flow direction. The solar energy concentrating and collecting system 11 is used to collect solar energy and provide heat for decomposing the calcium carbonate in the solar-assisted regeneration reactor 4 into calcium oxide. The feed water pump 15 is arranged between the deaerator 13 and the second heater 14. The dust collector 16 and the desulfurization tower 17 are sequentially arranged between the boiler 1 and the decarbonization reactor 2 along the flue gas flow direction.

[0064] The flue gas from the boiler 1 enters the dust collector 16 and the desulfurization tower 17 in turn for treatment and then enters the decarbonization reactor 2. The calcium oxide stored in the calcium oxide storage device 5 is also sent to the decarbonization reactor 2. The carbon dioxide in the flue gas reacts with the calcium oxide, and the generated calcium carbonate is stored in the calcium carbonate storage device 3. When the solar energy is sufficient, the solar-assisted regeneration reactor 4 starts to work, and the CaCO3 in the calcium carbonate storage device 3 enters the solar-assisted regeneration reactor 4 and absorbs solar heat to decompose CaCO3. The CaO generated by the decomposition enters the calcium oxide storage device 5 for storage. When it is necessary to adsorb the carbon dioxide in the flue gas, the calcium oxide in the calcium oxide storage device 5 is passed into the decarbonization reactor 2, and the cycle is repeated in this way. The exhaust steam of the steam turbine 6 after expansion and work enters the condenser 7 and condenses into water. A condensate pump is provided downstream of the condenser 7. The condensate is divided into two streams after passing through the condensate pump. The carbon dioxide in the flue gas in the decarbonization reactor 2 is absorbed by CaO. After the reaction, the decarbonized flue gas obtained is medium-low temperature flue gas of about 600°C. The medium-low temperature flue gas is passed into the condensate heater 8 to heat part of the condensate from the condenser 7. Before the condensate enters the condensate heater 8, the opening of the regulating valve is controlled to adjust the flow rate of the condensate entering the condensate heater 8 so that its temperature is heated to a temperature close to the saturation temperature. The condensate heated by the medium-low temperature flue gas enters the high-temperature heating surface 9 and is heated into steam. Another part of the condensate from the condenser 7 enters the first heater 12, the deaerator 13, the feed water pump 15 and the second heater 14 in turn for heating and then enters the low-temperature heating surface 10 for heating, and then merges with the condensate heated in the condensate heater 8 and enters the high-temperature heating surface 9 to be heated into steam for expansion work on the steam turbine 6. The extraction steam from the steam turbine 6 enters the first heater 12, the deaerator 13 and the second heater 14 through the extraction pipe 18 to provide a heat source.

[0065] Methods for post-combustion carbon capture in coal-fired power plants include:

[0066] S1, the flue gas in the boiler 1 is passed through the dust collector 16 and the desulfurization tower 17 in sequence and then introduced into the decarbonization reactor 2, the calcium oxide in the calcium oxide storage device 5 is input into the decarbonization reactor 2, the flue gas reacts with the calcium oxide to obtain decarbonized flue gas and calcium carbonate, the calcium carbonate is stored in the calcium carbonate storage device 3, wherein the reaction temperature of the decarbonization reactor 2 is 800°C;

[0067] S2. When solar energy is sufficient, the calcium carbonate in the calcium carbonate storage device 3 is input into the solar-assisted regeneration reactor 4 for reaction, and the obtained calcium oxide is stored in the calcium oxide storage device 5 and input into the decarbonization reactor 2 for recycling, wherein the reaction temperature of the solar-assisted regeneration reactor 4 is 900° C.;

[0068] S3, passing the decarbonized flue gas into the condensate heater 8 to heat part of the condensate formed by the exhaust steam of the steam turbine in the condenser 7, and then passing the heated condensate into the high-temperature heating surface 9 to heat it, and the obtained steam returns to the steam turbine 6 to expand and do work;

[0069] S4. Another part of the condensate formed by the exhaust steam of the steam turbine in the condenser 7 is sequentially input into the first heater 12, the deaerator 13, the feed water pump 15 and the second heater 14 for heating, and then input into the low-temperature heating surface 10 for heating, and then merged with the condensate heated in the condensate heater 8 and input into the high-temperature heating surface 9 to be heated into steam for expansion work on the steam turbine 6.

[0070] Comparative Example

[0071] This comparative example is implemented in the system shown in Example 1, except that the condensate heater 8 and the regulating valve are not provided.

[0072] Methods for post-combustion carbon capture in coal-fired power plants include:

[0073] (1) The flue gas in the boiler 1 is passed through the dust collector 16 and the desulfurization tower 17 in sequence and then introduced into the decarbonization reactor 2, and the calcium oxide in the calcium oxide storage device 5 is input into the decarbonization reactor 2, so that the flue gas reacts with the calcium oxide to obtain decarbonized flue gas and calcium carbonate, and the calcium carbonate is stored in the calcium carbonate storage device 3, wherein the reaction temperature of the decarbonization reactor 2 is 800° C.;

[0074] (2) When solar energy is sufficient, the calcium carbonate in the calcium carbonate storage device 3 is input into the solar-assisted regeneration reactor 4 for reaction, and the obtained calcium oxide is stored in the calcium oxide storage device 5 and input into the decarbonization reactor 2 for recycling, wherein the reaction temperature of the solar-assisted regeneration reactor 4 is 900° C.;

[0075] (3) The condensate formed by the exhaust steam of the steam turbine in the condenser 7 is sequentially input into the first heater 12, the deaerator 13, the feed water pump 15 and the second heater 14 for heating, and then input into the low-temperature heating surface 10 for heating, and then input into the high-temperature heating surface 9 for heating into steam for expansion work on the steam turbine 6.

[0076] It has been calculated that in a 1000MW coal-fired unit, when the carbon capture rate is 90%, the power generation efficiency of the coal-fired unit is reduced from 45.5% to 32.9% by adopting the technical solution of the comparative example, and the reduction is as high as 12.6 percentage points. When the technical solution of the embodiment of the present invention is adopted, the power generation efficiency of the coal-fired unit when the carbon capture rate is 90% is reduced from 45.5% to 42.8%, which is much higher than the existing carbon capture process of coal-fired power plants, and the solar thermal power conversion efficiency is as high as 36.0%. This shows that the technical solution proposed in the present invention can significantly improve the energy efficiency of the decarbonization unit and realize the efficient utilization of solar thermal energy and CaO chemical energy.

[0077] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A system for post-combustion carbon capture in a coal-fired power plant, characterized in that: The system comprises a boiler (1), a decarbonization reactor (2), a calcium carbonate storage device (3), a solar-assisted regeneration reactor (4), a calcium oxide storage device (5), a steam turbine (6), a condenser (7) and a condensate heater (8); A high-temperature heating surface (9) and a low-temperature heating surface (10) are sequentially arranged in the boiler (1) along the direction of flue gas flow; The flue gas from the boiler (1) enters the decarbonization reactor (2) for decarbonization; The decarbonization reactor (2), the calcium carbonate storage device (3), the solar-assisted regeneration reactor (4) and the calcium oxide storage device (5) are connected end to end in sequence, and the solar-assisted regeneration reactor (4) is used to generate a calcium carbonate decomposition reaction, and the heat of the reaction comes from solar energy; The exhaust steam of the steam turbine (6) after expansion and work enters the condenser (7) and condenses into water. Part of the condensed water from the condenser (7) and the decarbonized flue gas from the decarbonization reactor (2) undergo heat exchange in the condensate heater (8). The heated condensed water enters the high-temperature heating surface (9) for heating, and the formed steam is used to expand the steam turbine (6) and do work.

2. The system according to claim 1, characterized in that The system also includes a solar energy concentrating and heat collecting system (11) for collecting solar energy and providing heat for decomposing calcium carbonate into calcium oxide in the solar energy assisted regeneration reactor (4).

3. The system according to claim 1 or 2, characterized in that: The system further comprises a first heater (12), a deaerator (13) and a second heater (14) connected in sequence; Another part of the condensate from the condenser (7) enters the first heater (12), the deaerator (13) and the second heater (14) in sequence for heating and then enters the low-temperature heating surface (10) for heating, and then merges with the condensate heated in the condensate heater (8) and enters the high-temperature heating surface (9) to be heated into steam for expansion work on the steam turbine (6).

4. The system according to claim 3, characterized in that The extraction steam from the steam turbine (6) passes through an extraction steam pipeline (18) and enters the first heater (12), the deaerator (13) and the second heater (14) respectively to provide a heat source.

5. The system according to claim 3, characterized in that A water feed pump (15) is provided between the deaerator (13) and the second heater (14) for feeding condensed water treated by the deaerator (13) into the second heater (14).

6. The system according to any one of claims 1 to 5, characterized in that: A dust collector (16) and a desulfurization tower (17) are sequentially arranged between the boiler (1) and the decarbonization reactor (2) along the direction of flue gas flow; The flue gas from the boiler (1) enters the dust collector (16) and the desulfurization tower (17) in sequence for treatment and then enters the decarbonization reactor (2) for decarbonization.

7. A method for capturing carbon after combustion in a coal-fired power plant, the method being implemented in a system as claimed in any one of claims 1 to 6, characterized in that: The method comprises the following steps: S1, passing the flue gas in the boiler (1) into the decarbonization reactor (2), inputting the calcium oxide in the calcium oxide storage device (5) into the decarbonization reactor (2), allowing the flue gas to react with the calcium oxide to obtain decarbonized flue gas and calcium carbonate, and the calcium carbonate is stored in the calcium carbonate storage device (3); S2. When solar energy is sufficient, the calcium carbonate in the calcium carbonate storage device (3) is input into the solar-assisted regeneration reactor (4) for reaction, and the obtained calcium oxide is stored in the calcium oxide storage device (5) and input into the decarbonization reactor (2) for recycling; S3. Passing the decarbonized flue gas into a condensate heater (8) to heat part of the condensate formed by the turbine exhaust steam in the condenser (7), and then passing the heated condensate into the high-temperature heating surface (9) for heating, and the obtained steam is returned to the turbine (6) to expand and perform work.

8. The method according to claim 7, characterized in that The reaction temperature of the decarbonization reactor (2) is 700-900°C.

9. The method according to claim 7 or 8, characterized in that: The reaction temperature of the solar-assisted regeneration reactor (4) is 800-1000°C.

10. The method according to any one of claims 7 to 9, characterized in that: The method also includes: inputting another part of condensate formed by the exhaust steam of the steam turbine in the condenser (7) into the first heater (12), the deaerator (13) and the second heater (14) in sequence for heating, then inputting it into the low-temperature heating surface (10) for heating, and then merging it with the condensate heated in the condensate heater (8) and inputting it into the high-temperature heating surface (9) to heat it into steam for expansion work on the steam turbine (6).

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