System and method for capturing sulfur and carbon in flue gas by using desulfurized fly ash

Abstract

The invention relates to a system and a method for capturing sulfur and carbon in flue gas by using desulfurized fly ash, the desulfurized fly ash of a semi-dry desulfurization system is used as a raw material of a sulfur and carbon capturing absorbent, and the whole system and the whole method realize multiple purposes of desulfurized fly ash solid waste utilization, sulfur dioxide capturing, carbon dioxide capturing, decarburized flue gas high-temperature waste heat utilization and the like. The calcium-based absorbent is produced from the desulfurized fly ash rich in calcium solid waste, so that the raw material cost of the absorbent can be remarkably reduced, and the problem of environmental pollution caused by accumulation of the waste can be effectively solved. In addition, since the source of the desulfurized fly ash is close to the CO2 emission source, great convenience is provided for industrial production and resource recycling. By integrating and optimizing process links such as production and reception of the desulfurized fly ash and recycling of the carbon-containing flue gas, external extraction of a calcium-based material can be reduced to the greatest extent, and the overall cost for capturing sulfur dioxide and carbon dioxide is fundamentally reduced.

Description

Technical Field

[0001] The present application relates to the technical field of sulfur dioxide and carbon dioxide capture, and more specifically, to a system and method for capturing sulfur and carbon in flue gas using desulfurization ash. Background Art

[0002] Calcium-based CO2 capture technology is mainly based on the chemical reaction between CaO and acidic gas CO2. At high temperature, CaO reacts with CO2 to form calcium carbonate CaCO3, thereby fixing CO2 in a solid product. Subsequently, by calcining calcium carbonate, CO2 can be released and CaO can be regenerated so that it can be used again to capture CO2. This cycle can be carried out many times to achieve continuous capture of CO2. As the number of cycles increases, the performance of calcium-based absorbents (especially absorbents prepared from natural mineral raw materials such as natural limestone) in capturing carbon dioxide (CO2) will show a significant decline. Specifically, after about 10 cycles of capture, the absorption efficiency of such absorbents may drop sharply from the initial 80% to about 20%. In order to maintain an efficient CO2 removal rate, a large amount of fresh absorbent must be continuously replenished. In a high-temperature cyclic CO2 capture system based on CaO, the overall cost depends largely on the raw material cost of the absorbent, as well as its absorption capacity and stability during cyclic use.

[0003] The thermal power industry has achieved ultra-low SO2 emissions. Among the many flue gas desulfurization technologies, semi-dry desulfurization has been increasingly widely used in the power industry due to its advantages of low energy consumption, less wastewater and simple process. However, the desulfurization ash produced by this process has brought new problems: its composition is complex and changeable, its properties are not stable enough, and most of them are currently simply piled up, which not only occupies a large amount of precious land resources, but also may cause secondary pollution to the environment. Data show that the desulfurization by-products produced in the sintering flue gas desulfurization process in my country have exceeded 3 million tons each year. Therefore, research on the resource utilization of desulfurization ash is particularly urgent.

[0004] Desulfurization ash, a pale yellow solid dry powder composed of semi-dry desulfurization reaction residues, incompletely reacted sulfur dioxide absorbent and flue fly ash, has a fine particle size (average particle size is about 17.51 ​​microns) and a low water content (average about 3%). Its chemical composition is complex, containing a variety of compounds such as calcium sulfite, calcium sulfate, calcium hydroxide, and calcium oxide. It is a typical high-calcium and high-sulfur desulfurization product. It is particularly noteworthy that the main sulfur-containing substance in desulfurization ash is unstable CaSO3, whose content fluctuates between 70% and 80%, while the relatively stable CaSO4 accounts for a relatively low proportion. In addition, incompletely reacted calcium-based desulfurizers usually exist in the form of CaO and Ca(OH)2. Summary of the invention

[0005] The purpose of this application is to provide a system and method for capturing sulfur and carbon in flue gas using desulfurization ash. By utilizing desulfurization ash rich in calcium solid waste to produce calcium-based absorbents, not only can the raw material costs of the absorbents be significantly reduced, but the environmental pollution problems caused by the accumulation of desulfurization ash waste can also be effectively solved, thereby minimizing the overall cost of calcium-based materials for capturing sulfur dioxide and carbon dioxide.

[0006] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a system for capturing sulfur and carbon in flue gas using desulfurization ash, including a coal-fired boiler system, a semi-dry desulfurization system, an SO2 capture system, a carbonation system, and a CO2 capture system;

[0007] The SO2 capture system is connected to the semi-dry desulfurization system through a pipeline, and is used to receive the desulfurization ash from the semi-dry desulfurization system, and collect and store CaO and capture and store SO2 after calcining the desulfurization ash;

[0008] The carbonation system is connected to the SO2 capture system and the coal-fired boiler system through pipelines, respectively, and is used to receive CaO produced by calcining desulfurized ash and CO2-containing flue gas after desulfurization of the coal-fired boiler, and to perform calcium carbonate generation reaction, and to return the decarbonized flue gas to the coal-fired boiler system;

[0009] The CO2 capture system is connected to the carbonation system through a pipeline, and is used to receive carbonated calcium carbonate, and to recover and discharge CaO after calcining and decomposing the calcium carbonate, as well as to capture and store CO2;

[0010] The SO2 capture system, the carbonation system and the CO2 capture system respectively include a desulfurization ash calcining reactor, a carbonation reactor and a limestone calcining reactor, and the reactors of different systems all include an electromagnetic heating rotary kiln.

[0011] In an optional embodiment, the coal-fired boiler system includes a coal-fired boiler, a unit dust collector, a unit induced draft fan and a chimney, and the semi-dry desulfurization system is arranged between the unit dust collector and the unit induced draft fan;

[0012] The semi-dry desulfurization system comprises a semi-dry desulfurization ash bin, and the semi-dry desulfurization ash bin is connected to the desulfurization ash calcining reactor through a pipeline.

[0013] In an optional embodiment, the desulfurization ash calcining reactor is connected to a steam inlet pipe for exhausting the oxygen inside the desulfurization ash by introducing steam into the desulfurization ash calcining reactor before the desulfurization ash is calcined, and a steam control valve is provided on the steam inlet pipe.

[0014] In an optional embodiment, the downstream of the desulfurization ash calcining reactor is connected to a SO2 cooling heat exchanger via a pipeline, a flue gas analyzer for detecting oxygen content is installed on the pipeline, and the downstream of the SO2 cooling heat exchanger is connected in sequence via pipelines to a SO2 dust collector, a SO2 vacuum pump, a SO2 condenser and a SO2 collection and storage device.

[0015] In an optional embodiment, the desulfurization ash calcining reactor is connected to the desulfurization calcium oxide recovery bucket via a pipeline, or the desulfurization ash calcining reactor is connected to the semi-dry desulfurization system and the desulfurization calcium oxide recovery bucket via pipelines respectively;

[0016] The desulfurization calcium oxide recovery bucket is connected to the carbonation reactor through a pipeline;

[0017] A decarbonization fan is connected between the unit induced draft fan and the chimney through a pipeline, and the decarbonization fan is connected to the carbonation reactor through a carbon-containing flue gas pipeline to transport the desulfurized carbon-containing flue gas to the carbonation reactor for calcination reaction of calcium carbonate.

[0018] In an optional embodiment, the carbonation reactor is connected to a decarbonization flue gas pipeline, and the decarbonization flue gas pipeline is connected between the carbonation reactor and the coal-fired boiler. Temperature sensors are respectively provided on the carbon-containing flue gas pipeline and the decarbonization flue gas pipeline.

[0019] In an optional embodiment, the carbonation reactor is connected to a calcium carbonate recovery hopper via a pipeline, the calcium carbonate recovery hopper is connected to the limestone calcining reactor via a pipeline, and the downstream of the limestone calcining reactor is sequentially connected to a CO2 cooling heat exchanger, a CO2 dust collector, a CO2 vacuum pump, a CO2 condenser and a CO2 collection and storage device via pipelines.

[0020] In an optional embodiment, the limestone calcining reactor is connected to a decarbonization calcium oxide recovery bucket via a pipeline, the decarbonization calcium oxide recovery bucket is connected to the desulfurization calcium oxide recovery bucket via a pipeline, or the decarbonization calcium oxide recovery bucket is connected to the semi-dry desulfurization system via a pipeline.

[0021] In an optional embodiment, the electromagnetic heating rotary kiln includes a rotary kiln body, an electromagnetic heating coil, an electromagnetic heating controller, a thermocouple, and a solid particle recovery bucket;

[0022] The electromagnetic heating coil comprises at least two stages of electromagnetic heating coils and is wound around the outer wall of the rotary kiln body.

[0023] In a second aspect, the present invention provides a method for capturing sulfur and carbon from flue gas using desulfurization ash, which is performed according to the system for capturing sulfur and carbon from flue gas using desulfurization ash described in the above embodiment, and comprises the following steps:

[0024] The desulfurization ash of the semi-dry desulfurization system is transported to the desulfurization ash calcination reactor in the SO2 capture system for calcination and decomposition. Steam is introduced before heating and calcination, and the oxygen in the desulfurization ash calcination reactor is emptied and then heated. Under anaerobic conditions, CaSO3 is decomposed to generate CaO and SO2. The SO2 gas is stored after cooling, dust removal and condensation;

[0025] The CaO generated in the desulfurization ash calcining reactor is transferred through the desulfurization calcium oxide recovery bucket and then enters the carbonation reactor in the carbonation system for carbonation treatment to produce calcium carbonate. The volume of CaO filled in the carbonation reactor is 1 / 4 to 1 / 3 of the effective volume of the desulfurization ash calcining reactor.

[0026] The carbon-containing flue gas after desulfurization of the coal-fired boiler system is introduced into the carbonation reactor, and the carbonation reactor is opened to calcine and synthesize calcium carbonate. The introduced carbon-containing flue gas can reduce the temperature of CaO and increase the temperature of the carbon-containing flue gas itself to perform an exothermic synthesis reaction of calcium carbonate. The high-temperature decarbonized flue gas after decarbonization is returned to the boiler economizer of the coal-fired boiler for recycling;

[0027] The calcium carbonate generated in the carbonation reactor is transferred to the calcium carbonate recovery bucket and then transported to the limestone calcination reactor for calcination and decomposition to generate CaO and CO2. The CO2 gas is stored after cooling, dust removal and condensation.

[0028] The CaO generated in the limestone calcining reactor is transferred through the decarbonization calcium oxide recovery bucket and then selectively transported to the decarbonization calcium oxide recovery bucket or the semi-dry desulfurization system.

[0029] The system and method for capturing sulfur and carbon in flue gas using desulfurization ash of the present invention uses desulfurization ash of a semi-dry desulfurization system as the raw material of the sulfur and carbon capture absorbent, and the carbon-containing flue gas is the flue gas at the outlet of the desulfurization device of a coal-fired unit.

[0030] The main component of desulfurized ash, calcium sulfite, is calcined and decomposed into calcium oxide and sulfur dioxide in the desulfurized ash calcination reactor. The sulfur dioxide produced by the decomposition is collected. The generated calcium oxide absorbs carbon dioxide in the flue gas in the carbonation reactor to generate calcium carbonate. The decarbonized flue gas plays a role in cooling and participating in the reaction in the reactor. The calcium carbonate produced by the reaction is calcined and decomposed into calcium oxide and carbon dioxide in the limestone calcination reactor. The carbon dioxide produced by the decomposition is collected. The heat required for the calcination and decomposition reaction is heated by electromagnetic heating.

[0031] The overall system and method achieve multiple purposes such as utilization of desulfurization ash solid waste, capture of sulfur dioxide, capture of carbon dioxide, and utilization of high-temperature waste heat of decarbonized flue gas.

[0032] By utilizing desulfurization ash from calcium-rich solid waste to produce calcium-based absorbents, not only can the raw material costs of the absorbents be significantly reduced, but the environmental pollution problems caused by the accumulation of these wastes can also be effectively solved.

[0033] In addition, since the source of desulfurization ash is close to the source of CO2 emissions, it provides great convenience for industrial production and resource recycling. By integrating and optimizing the production and reception of desulfurization ash and the recycling of carbon-containing flue gas, the external procurement of calcium-based materials can be minimized, fundamentally reducing the overall cost of capturing sulfur dioxide and carbon dioxide.

[0034] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 The schematic diagram of the system for capturing sulfur and carbon in flue gas using desulfurized ash;

[0037] Figure 2 This is a system structure diagram for capturing sulfur and carbon in flue gas using desulfurized ash under large circulation conditions;

[0038] Figure 3 This is a system structure diagram for capturing sulfur and carbon in flue gas using desulfurization ash under a small circulation state;

[0039] Figure 4 This is a schematic diagram of the structure of an electromagnetic heating rotary kiln.

[0040] icon:

[0041] D1-coal-fired boiler; D2-dust collector of the unit; D3-induced draft fan of the unit; D4-chimney;

[0042] D5-calcium oxide storage room; D6-digestion device; D7-slaked lime storage room; D8-process water tank; D9-semi-dry desulfurization tower; D10-bag dust collector; D11-semi-dry desulfurization ash silo;

[0043] C1-desulfurization ash calcining reactor; C2-carbonation reactor; C3-limestone calcining reactor; C4-desulfurization calcium oxide recovery bucket; C5-calcium carbonate recovery bucket; C6-decarbonization calcium oxide recovery bucket; C7-decarbonization fan; C8-SO2 cooling heat exchanger; C9-SO2 dust collector; C10-SO2 vacuum pump; C11-SO2 condenser; C12-SO2 collection and storage device; C13-CO2 cooling heat exchanger; C14-CO2 dust collector; C15-CO2 vacuum pump; C16-CO2 condenser; C17-CO2 collection and storage device; C18-steam control valve;

[0044] B1-rotary kiln body; B2-primary electromagnetic heating coil; B3-secondary electromagnetic heating coil; B4-electromagnetic heating controller; B5-thermocouple; B6-solid particle recovery bucket. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0046] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0047] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0048] The system and method for capturing sulfur and carbon in flue gas using desulfurization ash in the present application mainly relate to the technical field of sulfur dioxide and carbon dioxide capture, and in particular to a system and method for capturing sulfur and carbon in flue gas by utilizing desulfurization ash produced by semi-dry desulfurization of flue gas in coal-fired boilers.

[0049] Specifically, by setting up different system units, sulfur dioxide and carbon dioxide are captured separately, and the carbon-containing flue gas after desulfurization is recycled and converted. At the same time, the heat in the carbonation process is comprehensively utilized to achieve a green production effect of energy saving and emission reduction.

[0050] The purpose of this application is to combine the existing flue gas conditions, material conditions and energy conditions of coal-fired power plants, and use low-cost calcium-based absorbents to capture sulfur dioxide and carbon dioxide in the flue gas. The sulfur and carbon capture effects are good, the captured products are of high purity, and no gaseous solid waste is generated, effectively achieving energy conservation and emission reduction, reducing the emission of carbon dioxide in the atmosphere, and promoting carbon neutrality.

[0051] See also Figure 2-Figure 3 , and combined with Figure 1 The system for capturing sulfur and carbon in flue gas using desulfurization ash in the present invention mainly comprises a coal-fired boiler system, a semi-dry desulfurization system, a SO2 capture system, a carbonation system and a CO2 capture system;

[0052] The SO2 capture system is connected to the semi-dry desulfurization system through a pipeline, and is used to receive the desulfurization ash from the semi-dry desulfurization system, and collect and store CaO and capture and store SO2 after calcining the desulfurization ash;

[0053] The carbonation system is connected to the SO2 capture system and the coal-fired boiler system through pipelines, respectively, and is used to receive the CaO produced by the calcination of desulfurized ash and the CO2-containing flue gas after desulfurization of the coal-fired boiler D1, and to perform calcium carbonate generation reaction, and to return the decarbonized flue gas to the coal-fired boiler system;

[0054] The CO2 capture system is connected to the carbonation system through a pipeline, and is used to receive carbonated calcium carbonate, and to recover and discharge CaO after calcining and decomposing the calcium carbonate, as well as to capture and store CO2;

[0055] The SO2 capture system, the carbonation system and the CO2 capture system respectively include a desulfurization ash calcining reactor C1, a carbonation reactor C2 and a limestone calcining reactor C3, and the reactors of different systems all include an electromagnetic heating rotary kiln.

[0056] The system for capturing sulfur and carbon in flue gas using desulfurization ash in the present invention constitutes the component basis for capturing sulfur and carbon in flue gas, and can facilitate the effective and continuous reception of desulfurization ash, calcination and decomposition of desulfurization ash, processing and collection of sulfur dioxide, carbonation of CaO, calcination and decomposition of calcium carbonate, processing and collection of sulfur dioxide, and internal circulation of CaO. By transforming the material form of the calcium-based absorbent, that is, by the cyclic transformation of CaO after calcination and decomposition of desulfurization ash to CaO after calcination and decomposition of calcium carbonate, the capture of sulfur dioxide and carbon dioxide can be effectively achieved, and by electromagnetic heating, the mixing of impure flue gas can be avoided to ensure the purity and quality of the captured sulfur dioxide and carbon dioxide.

[0057] In one specific embodiment, the coal-fired boiler system includes a coal-fired boiler D1, a unit dust collector D2, a unit induced draft fan D3 and a chimney D4, and the semi-dry desulfurization system is arranged between the unit dust collector D2 and the unit induced draft fan D3.

[0058] As an indispensable part of flue gas desulfurization, the semi-dry desulfurization system is mainly used to treat the flue gas of coal-fired boiler D1 on the one hand, and to provide raw material desulfurization ash for the flue gas sulfur-carbon capture system in this application on the other hand.

[0059] The semi-dry desulfurization system includes a calcium oxide storage chamber D5, a digestion device D6, a slaked lime storage chamber D7, a process water tank D8, a semi-dry desulfurization tower D9, a bag filter D10 and a semi-dry desulfurization ash bin D11. Figure 1 The CaSO3 generation reaction in reaction step 150.

[0060] The semi-dry desulfurization ash bin D11 is connected to the desulfurization ash calcining reactor C1 through a pipeline, and the semi-dry desulfurization ash bin D11 can be transported to the desulfurization ash calcining reactor C1 for calcination and decomposition to obtain an intermediate conversion product CaO.

[0061] The desulfurized ash calcining reactor C1 is connected to a steam inlet pipeline for exhausting the oxygen inside the desulfurized ash calcining reactor C1 by introducing steam into the desulfurized ash calcining reactor C1 before the desulfurized ash is calcined. A steam control valve C18 is provided on the steam inlet pipeline.

[0062] By pushing out and exhausting the oxygen in the desulfurization ash calcination reactor C1 by introducing steam before calcining the desulfurization ash, it is beneficial to construct an anaerobic environment in the desulfurization ash calcination reactor C1 and avoid side reactions and the generation of by-products.

[0063] The downstream of the desulfurization ash calcining reactor C1 is connected to the SO2 cooling heat exchanger C8 through a pipeline. A flue gas analyzer for detecting oxygen content is installed on the pipeline. When steam is introduced, the flue gas analyzer can detect the composition of the exhaust gas from the desulfurization ash calcining reactor C1, thereby providing a basis for controlling whether steam is introduced.

[0064] The downstream of the SO2 cooling heat exchanger C8 is connected in sequence via pipelines to a SO2 dust collector C9, a SO2 vacuum pump C10, a SO2 condenser C11 and a SO2 collecting and storing device C12, which are mainly used to process, collect and store the SO2 after calcination and decomposition of the desulfurization ash.

[0065] From the perspective of CaO solid material after decomposition of desulfurization ash calcined, the desulfurization ash calcining reactor C1 is connected to the desulfurization calcium oxide recovery bucket C4 through a pipeline, or the desulfurization ash calcining reactor C1 is connected to the semi-dry desulfurization system and the desulfurization calcium oxide recovery bucket C4 through pipelines.

[0066] The above two different discharging methods are mainly related to Figure 2 or Figure 3 It is determined by the large or small cycle of the intermediate conversion product CaO in the system, and is also matched with the material flow of CaO after the subsequent calcination and decomposition of calcium carbonate.

[0067] See also Figure 2 In the system of large circulation of intermediate conversion product CaO, the desulfurization ash calcining reactor C1 is directly connected to the desulfurization calcium oxide recovery bucket C4 through a pipeline. The CaO solid material after the desulfurization ash calcination and decomposition is not returned to the semi-dry desulfurization system, but all passes into the desulfurization calcium oxide recovery bucket C4. The CaO material obtained after the downstream calcium carbonate calcination and decomposition is all returned to the semi-dry desulfurization system, realizing the full circulation of the intermediate conversion product CaO in the overall system.

[0068] See also Figure 3 In the system of small circulation of intermediate conversion product CaO, the desulfurization ash calcining reactor C1 is connected to the semi-dry desulfurization system and the desulfurization calcium oxide recovery bucket C4 through pipelines. Part of the CaO solid material after the desulfurization ash calcination and decomposition is passed into the desulfurization calcium oxide recovery bucket C4, and the other part is returned to the semi-dry desulfurization system. The CaO material obtained after the downstream calcium carbonate calcination and decomposition is all returned to the desulfurization calcium oxide recovery bucket C4, realizing the partial circulation of the intermediate conversion product CaO in the overall system.

[0069] Regardless of the form, it does not affect the essential role of the intermediate conversion product CaO in the flue gas sulfur and carbon capture system and the process, and can be set according to the actual processing volume.

[0070] The desulfurization calcium oxide recovery hopper C4 is connected to the carbonation reactor C2 through a pipeline, and is mainly used to pass the CaO obtained by calcining and decomposing the desulfurization ash into the carbonation reactor C2.

[0071] A decarbonization fan C7 is connected between the unit's induced draft fan D3 and the chimney D4 via a pipeline. The decarbonization fan C7 is connected to the carbonation reactor C2 via a carbon-containing flue gas pipeline to transport the desulfurized carbon-containing flue gas to the carbonation reactor C2 for calcination of calcium carbonate, so that the CaO obtained by calcining and decomposing the desulfurization ash can react with the carbon dioxide in the flue gas to generate calcium carbonate.

[0072] The carbonation reactor C2 is connected to a decarbonization flue gas pipeline, which is connected between the carbonation reactor C2 and the coal-fired boiler D1. It mainly discharges the decarbonized flue gas back to the coal-fired boiler D1. At the same time, it can help the decarbonized flue gas absorb the heat released by the calcium carbonate formation reaction, increase the temperature of the discharged decarbonized flue gas, and comprehensively benefit this part of heat. The decarbonized flue gas can be returned to the boiler economizer inlet to recycle the flue gas.

[0073] The carbonation reactor C2 is connected to a calcium carbonate recovery hopper C5 via a pipeline, and the calcium carbonate recovery hopper C5 is connected to the limestone calcining reactor C3 via a pipeline, and is mainly used to transport the generated calcium carbonate to the limestone calcining reactor C3 for calcination and decomposition.

[0074] The downstream of the limestone calcining reactor C3 is connected in sequence through pipelines to a CO2 cooling heat exchanger C13, a CO2 dust collector C14, a CO2 vacuum pump C15, a CO2 condenser C16 and a CO2 collecting and storing device C17, which are mainly used to process, collect and store the CO2 produced after the calcination and decomposition of calcium carbonate.

[0075] The limestone calcining reactor C3 is connected to a decarbonization calcium oxide recovery bucket C6 through a pipeline, which is mainly used to receive and transfer CaO after calcination and decomposition of calcium carbonate. The decarbonization calcium oxide recovery bucket C6 is connected to the desulfurization calcium oxide recovery bucket C4 through a pipeline, or the decarbonization calcium oxide recovery bucket C6 is connected to the semi-dry desulfurization system through a pipeline, which is also matched with the circulation form of the intermediate conversion product CaO mentioned above.

[0076] See also Figure 4 The electromagnetic heating rotary kiln includes a rotary kiln body B1, an electromagnetic heating coil, an electromagnetic heating controller B4, a thermocouple B5 and a solid particle recovery bucket B6;

[0077] The electromagnetic heating coil includes at least two-stage electromagnetic heating coils and is wound around the outer wall of the rotary kiln body B1.

[0078] During the production process, the use of electromagnetic heating can avoid adding impurity flue gas compared to traditional combustion heating, ensure the recovery purity of sulfur dioxide and carbon dioxide, and facilitate recycling in the downstream process; at the same time, it can provide a relatively uniform heating temperature field in the rotary kiln, thereby overcoming defects such as overburning of the absorbent due to local high temperature and undercooking due to local low temperature, and improve the decomposition rate of CaSO3 and CaCO3. Furthermore, the use of electromagnetic heating has a high electric heat conversion rate, saves energy, makes temperature control more precise, and makes the equipment more intelligent, which is convenient for optimizing the control and adjustment of the entire system.

[0079] The present invention also provides a method for capturing sulfur and carbon in flue gas using desulfurization ash, which is carried out according to the system for capturing sulfur and carbon in flue gas using desulfurization ash as described above, and comprises the following steps:

[0080] The desulfurized ash of the semi-dry desulfurization system is transported to the desulfurized ash calcining reactor C1 in the SO2 capture system for calcination and decomposition. Steam is introduced before heating and calcination, and the oxygen in the desulfurized ash calcining reactor C1 is emptied and then heated. Under anaerobic conditions, CaSO3 is decomposed to generate CaO and SO2. The SO2 gas is stored after cooling, dust removal and condensation;

[0081] The CaO generated in the desulfurization ash calcining reactor C1 is transferred through the desulfurization calcium oxide recovery hopper C4 and then enters the carbonation reactor C2 in the carbonation system for carbonation treatment to produce calcium carbonate. The volume of CaO filled in the carbonation reactor C2 is 1 / 4 to 1 / 3 of the effective volume of the desulfurization ash calcining reactor C1.

[0082] The carbon-containing flue gas after desulfurization of the coal-fired boiler system is introduced into the carbonation reactor C2, and the carbonation reactor C2 is opened to calcine and synthesize calcium carbonate. The introduced carbon-containing flue gas can reduce the temperature of CaO and increase the temperature of the carbon-containing flue gas itself to perform an exothermic synthesis reaction of calcium carbonate. The high-temperature decarbonized flue gas after decarbonization is returned to the boiler economizer of the coal-fired boiler D1 for recycling;

[0083] The calcium carbonate generated in the carbonation reactor C2 is transferred to the calcium carbonate recovery hopper C5 and then transported to the limestone calcination reactor C3 for calcination and decomposition to generate CaO and CO2. The CO2 gas is stored after cooling, dust removal and condensation.

[0084] The CaO generated in the limestone calcining reactor C3 is transferred through the decarbonization calcium oxide recovery bucket C6 and then selectively transported to the decarbonization calcium oxide recovery bucket C6 or the semi-dry desulfurization system.

[0085] The following is an overall description of the system and method for capturing sulfur and carbon in flue gas using desulfurization ash.

[0086] Desulfurization ash transportation: The desulfurization ash in the semi-dry desulfurization ash bin D11 in the existing semi-dry desulfurization system is used as the raw material of the carbon dioxide capture absorbent, and the desulfurization ash is transported to the desulfurization ash calcining reactor C1. The transportation method can be pneumatic powder conveying or bucket lifting.

[0087] Furthermore, the desulfurization ash conveying step uses the desulfurization ash in the existing semi-dry desulfurization system as the raw material of the sulfur and carbon capture absorbent, and the quality requirements of the desulfurization ash meet the normal operation specifications of the desulfurization system. The average particle size of the desulfurization ash powder is 7.252μm, the median particle size (D50) is 4.521μm, 80% of the particle size is between 1.039 and 16.162μm, and the specific surface area of ​​the desulfurization ash is 2.25m 2 / g, indicating that it has a relatively large specific surface area. The shape of desulfurized ash particles is mostly irregular small spheres with many pores on the surface, and the pore diameter is 0.1-0.2μm.

[0088] Oxygen exhaust from desulfurization ash calcining reactor C1: Open the steam control valve C18. Before starting the desulfurization ash calcining reactor C1, introduce low-pressure saturated steam with a pressure of 0.3Mpa to exhaust the oxygen in the original desulfurization ash calcining reactor C1. Monitor the exhaust gas from the desulfurization ash calcining reactor C1. When the flue gas analyzer shows that the oxygen content is close to "0", stop introducing low-pressure steam and close valve C18.

[0089] Calcination and decomposition of desulfurized ash: The desulfurized ash calcination reactor C1 adopts an electromagnetic heating rotary kiln, which uses electromagnetic heating technology to provide a heat source to ensure that the reactor reaches a reaction window temperature of 700-950°C, and provides the heat required for the decomposition reaction for calcination and decomposition. Under anaerobic conditions, CaSO3 is decomposed to produce CaO and SO2.

[0090] Further: The principle of this reaction is: CaSO3→CaO+SO2( Figure 1 The purpose of exhausting oxygen from the desulfurized ash calcining reactor C1 is to exhaust the oxygen in the original desulfurized ash calcining reactor C1, in order to avoid the side reaction: CaSO3+O2→CaSO4. CaSO3 reacts to generate CaSO4 in a high temperature oxygen environment. The temperature required for the decomposition of CaSO4 is 1400°C, which is difficult to achieve and is not easy to decompose.

[0091] Furthermore, the desulfurized ash in the desulfurized ash calcining reactor C1 contains a small amount of Ca(OH)2. The desulfurized ash is heated and calcined in the desulfurized ash calcining reactor C1 to decompose Ca(OH)2 into CaO and H2O ( Figure 1 Reaction step 110).

[0092] Furthermore, the desulfurized ash calcining reactor C1 includes a rotary kiln body B1, a primary electromagnetic heating coil B2, a secondary electromagnetic heating coil B3, an electromagnetic heating controller B4, a thermocouple B5 and a solid particle recovery bucket B6.

[0093] Furthermore: the desulfurized ash calcining reactor C1 adopts an electromagnetic heating rotary kiln, and the electromagnetic heating rotary kiln adopts a two-stage or multi-stage electromagnetic heating coil. The electromagnetic heating coil wrapped around the outer wall of the rotary kiln can be divided into a preheating section and a reaction section. The preheating section can heat CaSO3 from room temperature to 600-750°C. The preheating section avoids direct contact between CaSO3 and the ultra-high temperature heat source, causing CaSO3 to be hot outside and cold inside, and sintering. The reaction section promotes the decomposition of CaSO3 into CaO and SO2, and the temperature of the reaction section is maintained at 800-950°C.

[0094] In the desulfurized ash calcination and decomposition step, the desulfurized ash calcination reactor C1 adopts an electromagnetic heating rotary kiln, and the electromagnetic heating controller B4 is used to control the temperature of the electromagnetic heating coil according to the current and voltage to heat the rotary kiln body B1. The thermocouple B5 can monitor the temperature in the rotary kiln in real time, and the detection result can be fed back to the electromagnetic heating controller B4, thereby realizing the online monitoring and control of the temperature of the electromagnetic heating rotary kiln.

[0095] In the desulfurization ash calcination and decomposition step, the angle between the rotary kiln body B1 and the horizontal plane is 0-8°, the rotary kiln body B1 is provided with flow guide stirring blades, the rotary kiln body B1 rotates at a speed of 1-2 r / min, and the desulfurization ash stays in the rotary kiln for 15-20 min. The time the desulfurization ash stays in the rotary kiln can be controlled by controlling the rotation speed and the angle between the rotary kiln and the horizontal plane according to the particle size of the desulfurization ash.

[0096] The desulfurization ash calcination reactor C1 generates SO2 and CaO, and most of the CaO will enter the desulfurization calcium oxide recovery bucket C4 by gravity. The SO2 gas passes through the SO2 cooling heat exchanger C8, the SO2 dust collector C9, the SO2 vacuum pump C10, and the SO2 condenser C11 to remove H2O and dust, and finally obtains low-temperature pure SO2 and stores it in the sulfur dioxide storage tank of the SO2 collection and storage device C12.

[0097] The CaO generated in the desulfurization ash calcination reactor C1 enters the desulfurization calcium oxide recovery hopper C4, and then enters the carbonation reactor C2. The volume of CaO filled into the carbonation reactor C2 is 1 / 4 to 1 / 3 of the effective volume of the desulfurization ash calcination reactor C1.

[0098] The decarbonization fan C7 is used to draw out flue gas containing carbon dioxide from the inlet of the chimney D4 of the coal-fired unit. The flue gas containing carbon dioxide enters the carbonation reactor C2, and the carbonation reactor C2 is started.

[0099] The reaction principle in the carbonation reactor C2 is: CaO+CO2→CaCO3 reaction occurs under the window temperature condition of 600-650℃ ( Figure 1 Reaction step 120).

[0100] The carbonation reactor C2 is an electromagnetically heated rotary kiln, and its structure and function are similar to those of the desulfurization ash calcination reactor C1.

[0101] The carbon-containing flue gas is selected from the flue gas at the outlet of the desulfurization device of the coal-fired unit. The flue gas temperature at the outlet of the typical semi-dry desulfurization device of a coal-fired power plant is 70-80°C, and the flue gas components are carbon dioxide, water, oxygen, and nitrogen, accounting for 20.6%, 9.0%, 6.9%, and 70.5% respectively. The content of pollutants sulfur dioxide and dust in the carbon-containing flue gas reaches the ultra-low emission level, which is extremely low and can be ignored.

[0102] When the decarbonized flue gas enters the carbonation reactor C2, the CaO temperature can be reduced from 950°C to 600-650°C, and at the same time, the preheated primary air can be heated from 80°C to 600-650°C. Thus, the primary air and CaO can reach a carbonation reaction window temperature of 600-650°C.

[0103] During the carbonation reaction of CaO, the reaction window temperature inside the carbonation reactor C2 is 600-650℃. The reaction of CaO+CO2→CaCO3 is an exothermic reaction, which can provide heat for the carbonation reactor C2. At the same time, the electromagnetic heating system can provide heat for the carbonation reactor C2. The low-temperature flue gas of 70-80℃ can reduce the reactor temperature. By adjusting the inlet flow of the low-temperature flue gas and the heat supply of the electromagnetic heating system, the temperature inside the carbonation reactor C2 can be stably maintained at 600-650℃, ensuring the efficient reaction of CaO+CO2→CaCO3.

[0104] The decarbonization fan C7 is preferably a centrifugal fan with adjustable blades, with a total pressure of 1500-2500Pa, and the fan flow rate is calculated based on the carbon-calcium ratio, the scale of carbon dioxide capture, and the carbon-containing flue gas parameters.

[0105] The carbonation reactor C2 rotary kiln is provided with flow guide stirring blades, and the rotation speed of the rotary kiln is controlled at 4-6r / min to enhance the mass transfer and heat transfer inside the reactor.

[0106] The flue gas temperature after decarbonization in the carbonation reactor C2 is about 600-700°C. The decarbonized flue gas can be returned to the boiler economizer inlet for recycling.

[0107] The calcium carbonate powder in the calcium carbonate recovery hopper C5 is transported to the limestone calcining reactor C3. The limestone calcining reactor C3 adopts an electromagnetic heating rotary kiln. The electromagnetic heating technology is used to provide a heat source to ensure that the reactor reaches a reaction window temperature of 900-950°C and provides the heat required for the decomposition reaction for calcination and decomposition, so that CaCO3 is decomposed into CaO and CO2.

[0108] The principle of the above reaction is: CaCO3→CaO+CO2 reaction occurs under the 900-950℃ window temperature condition in the limestone calcining reactor C3 ( Figure 1 130 in reaction step 130).

[0109] The limestone calcining reactor C3 generates CO2 and CaO, and most of the calcium oxide will enter the decarbonized calcium oxide recovery bucket C6 by gravity. The CO2 gas passes through the CO2 cooling heat exchanger C13, CO2 dust collector C14, CO2 vacuum pump C15, and CO2 condenser C16 to remove H2O and dust, and finally obtains low-temperature pure CO2 and stores it in the carbon dioxide storage tank in the CO2 collection and storage device C17.

[0110] The limestone calcining reactor C3 is an electromagnetically heated rotary kiln, and its structure and function are similar to those of the desulfurized ash calcining reactor C1.

[0111] The CaO in the limestone calcining reactor C3 can be selected to be returned to the semi-dry desulfurization system, such as Figure 2 As shown, a large cycle of desulfurization and decarbonization is achieved. The CaO in the limestone calcining reactor C3 can also be returned to the desulfurization calcium oxide recovery bucket C4, such as Figure 3 As shown, a small decarbonization cycle is achieved.

[0112] The present invention uses the solid waste desulfurization ash produced by the semi-dry desulfurization device of the coal-fired power plant as the sulfur and carbon adsorbent material. The advantages are: due to the unstable CaO, Ca(OH)2 and CaSO3 in the desulfurization ash, during the long-term stacking process, CaO will slowly absorb water vapor in the air and continuously generate Ca(OH)2 (see Figure 1 In the reaction step 140), the generated Ca(OH)2 and the original Ca(OH)2 continue to absorb CO2 in the air to form CaCO3, causing the desulfurized ash to agglomerate; the CaSO3 with a high content is physically and chemically stable under dry and room temperature conditions and is not prone to oxidation or decomposition reactions. However, the physical and chemical properties of CaSO3 in a wet state are very unstable and it is extremely easy to oxidize in the air to generate stable and dense CaSO4, resulting in the stability of the desulfurized ash being destroyed as the main component of the oxidation product layer.

[0113] Due to the above problems, it is difficult to reasonably utilize desulfurization ash. At present, these technologies still have certain limitations. The treatment of semi-dry sintering flue gas desulfurization ash is still mainly for stockpiling, which occupies a large amount of scarce and non-renewable land resources, and the complex components in the desulfurization ash may cause secondary pollution to the environment. At the same time, enterprises need to bear high management and treatment costs. The method of comprehensive utilization of semi-dry flue gas desulfurization ash proposed in this application will become one of the ideas for enterprises to solve the problem of desulfurization ash disposal.

[0114] In addition, the treatment price of solid waste desulfurization ash produced by the semi-dry desulfurization device of coal-fired power plants is 150-200 yuan / t, while the calcium-based adsorbent introduced in relevant literature has a complex pretreatment process, high energy consumption, and is difficult to achieve industrialization. The price is estimated to be 3,000-10,000 yuan / ton. The solid waste desulfurization ash produced by the semi-dry desulfurization device of coal-fired power plants is used as raw material, which is easy to obtain and has a huge price advantage. The specific surface area of ​​desulfurization ash is 2.25m 2 / g, indicating that it has a relatively large specific surface area. The desulfurization ash particles are mostly irregular small spherical shapes with many pores on the surface. The pore diameter is 0.1-0.2μm. The desulfurization ash has a large specific surface area, which is very beneficial for the subsequent capture of carbon dioxide by calcium oxide. The adsorbent that has failed due to sintering and other reasons can be directly sent back to the coal-fired power plant furnace to be mixed with coal as a flue gas desulfurization absorbent in the furnace without generating any solid waste.

[0115] The flue gas at the outlet of the semi-dry desulfurization device meets the ultra-low emission standards of pollutants in coal-fired power plants, with extremely low concentrations of sulfur dioxide and dust, which greatly reduces the risk of absorbent sulfidation and blockage. At the same time, the flue gas at the outlet of the semi-dry desulfurization device contains about 9.0% water, which is equivalent to the molar mass of calcium oxide in the system. Water can react with calcium oxide to increase the molar volume of calcium oxide, thereby enhancing the effect of calcium oxide in adsorbing carbon dioxide.

[0116] For electromagnetic coil heating, the heat source used by existing calcination reaction equipment is fossil fuel oxygen-enriched combustion heat. First, the oxygen-enriched combustion and fuel supply system are complex and the operating cost is high. Secondly, a large amount of nitrogen oxides, water vapor, dust, sulfur dioxide and other impurities are generated during the combustion process, which reduces the volume fraction of captured CO2. The purity of carbon dioxide in the reactor is low and carbon dioxide products cannot be produced.

[0117] The advantages of the electromagnetically heated rotary kiln in the present application are: (1) no complex oxygen-enriched combustion system is required; (2) the decomposition reaction of CaSO3 and CaCO3 will not add new impurity flue gas, and the system can capture high-purity SO2 and CO2, which is beneficial for downstream utilization; (3) compared with the use of a burner to provide heat for the calcination reaction, the use of electromagnetic heating makes the temperature field in the kiln more uniform, overcoming the defects of overburning of the absorbent due to local high temperature and undercooking due to local low temperature, thereby improving the decomposition rate of CaSO3 and CaCO3; (4) the use of electromagnetic heating has a high electric heat conversion rate, saves energy, makes temperature control more precise, and makes the equipment more intelligent, which facilitates the optimization, control and adjustment of the entire system.

[0118] The present invention captures SO2 and CO2 from desulfurized flue gas at the same time, thereby greatly increasing the economic benefits of the system, and can be coupled with systems such as thermal power plants, steel plants, and cement plants without affecting the operation of the original system equipment.

[0119] It should be noted that, in the absence of conflict, the features in the embodiments of this application may be combined with each other.

[0120] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A system for capturing sulfur and carbon in flue gas using desulfurization ash, characterized in that: Including coal-fired boiler system, semi-dry desulfurization system, SO2 capture system, carbonation system and CO2 capture system; The SO2 capture system is connected to the semi-dry desulfurization system through a pipeline, and is used to receive the desulfurization ash from the semi-dry desulfurization system, and collect and store CaO and capture and store SO2 after calcining the desulfurization ash; The carbonation system is connected to the SO2 capture system and the coal-fired boiler system through pipelines, respectively, and is used to receive CaO produced by calcining desulfurized ash and CO2-containing flue gas after desulfurization of the coal-fired boiler, and to perform calcium carbonate generation reaction, and to return the decarbonized flue gas to the coal-fired boiler system; The CO2 capture system is connected to the carbonation system through a pipeline, and is used to receive carbonated calcium carbonate, and to recover and discharge CaO after calcining and decomposing the calcium carbonate, as well as to capture and store CO2; The SO2 capture system, the carbonation system and the CO2 capture system respectively include a desulfurization ash calcining reactor, a carbonation reactor and a limestone calcining reactor, and the reactors of different systems all include an electromagnetic heating rotary kiln.

2. The system for capturing sulfur and carbon in flue gas using desulfurization ash according to claim 1 is characterized in that: The coal-fired boiler system comprises a coal-fired boiler, a unit dust collector, a unit induced draft fan and a chimney, and the semi-dry desulfurization system is arranged between the unit dust collector and the unit induced draft fan; The semi-dry desulfurization system comprises a semi-dry desulfurization ash bin, and the semi-dry desulfurization ash bin is connected to the desulfurization ash calcining reactor through a pipeline.

3. The system for capturing sulfur and carbon in flue gas using desulfurized ash according to claim 2 is characterized in that: The desulfurized ash calcining reactor is connected to a steam inlet pipe for exhausting the oxygen inside the reactor by introducing steam into the desulfurized ash calcining reactor before the desulfurized ash is calcined. A steam control valve is provided on the steam inlet pipe.

4. The system for capturing sulfur and carbon in flue gas using desulfurization ash according to claim 3 is characterized in that: The downstream of the desulfurized ash calcining reactor is connected to a SO2 cooling heat exchanger through a pipeline, and a flue gas analyzer for detecting oxygen content is installed on the pipeline. The downstream of the SO2 cooling heat exchanger is connected to a SO2 dust collector, a SO2 vacuum pump, a SO2 condenser and a SO2 collecting and storing device in sequence through pipelines.

5. The system for capturing sulfur and carbon in flue gas using desulfurized ash according to claim 2, characterized in that: The desulfurization ash calcining reactor is connected to a desulfurization calcium oxide recovery bucket via a pipeline, or the desulfurization ash calcining reactor is connected to the semi-dry desulfurization system and the desulfurization calcium oxide recovery bucket via pipelines respectively; The desulfurization calcium oxide recovery bucket is connected to the carbonation reactor through a pipeline; A decarbonization fan is connected between the unit induced draft fan and the chimney through a pipeline, and the decarbonization fan is connected to the carbonation reactor through a carbon-containing flue gas pipeline to transport the desulfurized carbon-containing flue gas to the carbonation reactor for calcination reaction of calcium carbonate.

6. The system for capturing sulfur and carbon in flue gas using desulfurized ash according to claim 2 is characterized in that: The carbonation reactor is connected to a decarbonization flue gas pipeline, and the decarbonization flue gas pipeline is connected between the carbonation reactor and the coal-fired boiler.

7. The system for capturing sulfur and carbon in flue gas using desulfurization ash according to claim 2, characterized in that: The carbonation reactor is connected to a calcium carbonate recovery bucket via a pipeline, and the calcium carbonate recovery bucket is connected to the limestone calcining reactor via a pipeline. The downstream of the limestone calcining reactor is sequentially connected to a CO2 cooling heat exchanger, a CO2 dust collector, a CO2 vacuum pump, a CO2 condenser and a CO2 collection and storage device via pipelines.

8. The system for capturing sulfur and carbon in flue gas using desulfurization ash according to claim 5, characterized in that: The limestone calcining reactor is connected to a decarbonization calcium oxide recovery bucket via a pipeline, and the decarbonization calcium oxide recovery bucket is connected to the desulfurization calcium oxide recovery bucket via a pipeline, or the decarbonization calcium oxide recovery bucket is connected to the semi-dry desulfurization system via a pipeline.

9. The system for capturing sulfur and carbon in flue gas using desulfurization ash according to claim 1, characterized in that: The electromagnetic heating rotary kiln comprises a rotary kiln body, an electromagnetic heating coil, an electromagnetic heating controller, a thermocouple and a solid particle recovery bucket; The electromagnetic heating coil comprises at least two stages of electromagnetic heating coils and is wound around the outer wall of the rotary kiln body.

10. A method for capturing sulfur and carbon in flue gas using desulfurization ash, The system for capturing sulfur and carbon from flue gas using desulfurization ash according to claim 1 is characterized in that: The following steps are involved: The desulfurization ash of the semi-dry desulfurization system is transported to the desulfurization ash calcination reactor in the SO2 capture system for calcination and decomposition. Steam is introduced before heating and calcination, and the oxygen in the desulfurization ash calcination reactor is emptied and then heated. Under anaerobic conditions, CaSO3 is decomposed to generate CaO and SO2. The SO2 gas is stored after cooling, dust removal and condensation; The CaO generated in the desulfurization ash calcining reactor is transferred through the desulfurization calcium oxide recovery bucket and then enters the carbonation reactor in the carbonation system for carbonation treatment to produce calcium carbonate. The volume of CaO filled in the carbonation reactor is 1 / 4 to 1 / 3 of the effective volume of the desulfurization ash calcining reactor. The carbon-containing flue gas after desulfurization of the coal-fired boiler system is introduced into the carbonation reactor, and the carbonation reactor is opened to calcine and synthesize calcium carbonate. The introduced carbon-containing flue gas can reduce the temperature of CaO and increase the temperature of the carbon-containing flue gas itself to perform an exothermic synthesis reaction of calcium carbonate. The high-temperature decarbonized flue gas after decarbonization is returned to the boiler economizer of the coal-fired boiler for recycling; The calcium carbonate generated in the carbonation reactor is transferred to the calcium carbonate recovery hopper and then transported to the limestone calcination reactor for calcination and decomposition to generate CaO and CO2. The CO2 gas is stored after cooling, dust removal and condensation. The CaO generated in the limestone calcining reactor is transferred through the decarbonization calcium oxide recovery bucket and then selectively transported to the decarbonization calcium oxide recovery bucket or the semi-dry desulfurization system.

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