CFB ash-desulfurized gypsum composite particle preparation method and coal-fired flue gas CO2 mineralization method and system

Abstract

The invention belongs to the technical field of CO2 trapping, and particularly relates to a CFB ash-desulfurized gypsum composite particle preparation method and a coal-fired flue gas CO2 mineralization method and system. The system comprises a CFB ash-desulfurized gypsum composite particle preparation unit, a pressurized fixed bed adsorption unit and a flue gas circulation unit. The circulating fluidized bed ash desulfurization gypsum is adopted to prepare the composite particles, based on the characteristic of high CaO content of the ash, flue gas waste heat and H2O in flue gas are utilized, coal-fired flue gas CO2 is adsorbed through pressurization and mineralization, the particle strength is improved, pollution is treated with waste, the cost is low, the process is simple, cooperative treatment of the coal-fired solid waste and the flue gas CO2 is achieved, and the comprehensive utilization rate of the coal-fired solid waste and the flue gas CO2 is increased. Meanwhile, the generated composite particles can replace part of mineral raw materials such as quartz, clay and gravel, and certain economic benefits are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of CO2 capture, and in particular relates to a method and system for preparing CFB ash-desulfurized gypsum composite particles and mineralizing CO2 from coal-fired flue gas. Background Art

[0002] Among numerous low-carbon technologies, carbon capture, utilization, and storage (CCUS) is currently considered the only option for achieving low-carbon utilization of fossil energy. Within CCUS, CO2 capture is the most expensive, accounting for 60% to 80% of the total technology cost. Circulating fluidized bed (CFB) ash (including fly ash and bottom ash) and desulfurization gypsum are solid wastes produced by circulating fluidized bed (CFB) boilers burning low-calorific value coals such as gangue, middlings, and coal slime. With the widespread application of circulating fluidized bed (CFB) technology, large quantities of CFB ash and desulfurization gypsum are generated.

[0003] CFB ash has pozzolanic reactivity, and the CaSO₄ in desulfurized gypsum can act as an activator to stimulate the activity of CFB ash. Using CFB ash and desulfurized gypsum, composite particles with a certain strength can be produced, replacing mineral raw materials such as quartz, clay, and sand and gravel, offering significant economic benefits. Furthermore, ash contains high levels of alkali metal and alkaline earth metal oxides, such as CaO. Using CFB ash-desulfurized gypsum composite particles for mineralized CO₂ adsorption can significantly reduce CO₂ capture costs. Summary of the Invention

[0004] In view of the problems and shortcomings in the prior art, the object of the present invention is to provide a method and system for preparing CFB ash-desulfurization gypsum composite particles and mineralizing CO2 from coal-fired flue gas.

[0005] Based on the above purpose, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a system for preparing CFB ash-desulfurized gypsum composite particles and mineralizing CO2 from coal-fired flue gas, comprising a CFB ash-desulfurized gypsum composite particle preparation unit, a pressurized fixed bed adsorption unit, and a flue gas circulation unit;

[0007] The CFB ash-desulfurized gypsum composite particle preparation unit includes a circulating fluidized bed boiler, a dust collector, and a desulfurization tower connected in parallel. The solid discharge ports of the three are connected to the inlet of the ball mill, and the outlet of the ball mill is connected to a mixer and a granulator in sequence; the granulator discharge port is connected to a pressurized fixed bed adsorption unit; the flue gas outlet of the desulfurization tower is connected to a flue gas circulation unit;

[0008] The pressurized fixed bed adsorption unit includes a fixed bed reactor, the discharge port of the granulator is connected to the feed port at the top of the fixed bed reactor, the flue gas outlet at the top of the fixed bed reactor is connected to the dust collector inlet, and the flue gas inlet at the top of the fixed bed reactor is connected to the flue gas circulation unit;

[0009] The flue gas circulation unit includes two parallel flue gas passages, one of which is directly connected from the flue gas outlet of the desulfurization tower to the flue gas inlet of the fixed bed reactor through an induced draft fan, and the other flue gas passage includes a flue gas cooler, a flue gas filter, a flue gas compressor and a gas storage tank connected in sequence along the flue gas flow direction. The inlet of the flue gas cooler is connected to the flue gas outlet of the desulfurization tower, and the outlet of the gas storage tank is connected to the flue gas inlet at the top of the fixed bed reactor.

[0010] Furthermore, two flue gas inlets are provided on the upper portion of the fixed bed reactor, which are respectively connected to two flue gas passages.

[0011] Furthermore, rappers are provided in the middle and lower parts of the fixed bed reactor.

[0012] Furthermore, a thermal insulation layer is provided on the side wall of the fixed bed reactor.

[0013] Furthermore, a loading machine is provided between the feed port of the fixed bed reactor and the discharge port of the granulator.

[0014] Furthermore, the flue gas outlet of the circulating fluidized bed boiler merges with the flue gas outlet of the fixed bed reactor and then flows into the dust collector.

[0015] Furthermore, it also includes a composite particle curing unit; the composite particle curing unit includes a particle conveyor and a curing chamber; the discharge port of the fixed bed reactor is connected to the inlet of the particle conveyor, and further connected to the inlet of the curing chamber.

[0016] Furthermore, the temperature of the pressurized fixed bed adsorption unit is determined by the flue gas waste heat and the temperature rise of the compressor, and the heat dissipation loss is reduced by the insulation layer. The pressure of the pressurized fixed bed adsorption system is controlled by the flue gas compressor.

[0017] The second aspect of the present invention provides a method for preparing CFB ash-desulfurized gypsum composite particles and mineralizing CO2 from coal-fired flue gas using the system described in the first aspect, comprising the following steps:

[0018] (1) Preparation of CFB ash-desulfurized gypsum composite particles: The bottom ash, fly ash and desulfurized gypsum of the circulating fluidized bed boiler are mixed by a material conveyor, ball milled, stirred and granulated to obtain CFB ash-desulfurized gypsum composite particles; the amount of the bottom ash is 30% to 60%, the amount of the fly ash is 30% to 60%, and the amount of the desulfurized gypsum is 5% to 20% by weight;

[0019] (2) Reactor feeding: feeding the CFB ash-desulfurized gypsum composite particles into the fixed bed reactor and closing the fixed bed reactor feed port. At this time, the fixed bed reactor is in a closed state;

[0020] (3) Flue gas CO2 mineralization: First, desulfurized flue gas is introduced into the fixed bed reactor. When the pressure in the fixed bed reactor reaches 0.5-1.5 kPa, compressed flue gas is continuously introduced, so that the CFB ash-desulfurized gypsum composite particles and flue gas CO2 react under a pressure of 0.5-2.0 MPa, using H2O in the flue gas and the waste heat of the flue gas for 0.5-2 hours to achieve flue gas CO2 mineralization;

[0021] (4) After the reaction is completed, the flue gas after the reaction is dedusted and desulfurized before being discharged, and the CFB ash-desulfurized gypsum composite particles after the reaction are discharged from the fixed bed reactor.

[0022] Furthermore, the fly ash is fly ash obtained after the flue gas of a circulating fluidized bed boiler and / or a fixed bed reactor is treated by a dust collector.

[0023] Furthermore, the method further includes curing of the composite particles: the CFB ash-desulfurization gypsum composite particles discharged in step (4) are transported to a curing room through a particle conveyor for natural curing.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention utilizes the volcanic ash reaction activity of coal-fired solid waste circulating fluidized bed ash and the stimulating effect of desulfurization gypsum to prepare composite particles to replace mineral raw materials such as quartz, clay, sand and gravel, thereby realizing on-site disposal of coal-fired solid waste circulating fluidized bed ash and desulfurization gypsum, with significant economic benefits, and is conducive to the large-scale resource utilization of circulating fluidized bed ash and desulfurization gypsum.

[0026] (2) The present invention utilizes CaO and other alkali metal and alkaline earth metal oxides in the coal-fired solid waste circulating fluidized bed ash to mineralize and adsorb CO2 from coal-fired flue gas, thereby treating pollution with waste, having low cost and simple process.

[0027] (3) The composite particles proposed in the present invention adsorb CO2 and can utilize the voids in the particles to accelerate the diffusion of flue gas into the interior of the particle bed. The carbonation reaction is accelerated by pressurization, flue gas waste heat, and H2O in the flue gas, resulting in a high CO2 capture efficiency.

[0028] (4) During the CO2 adsorption process of the circulating fluidized bed ash desulfurization gypsum composite particles of the present invention, the particles remain stationary in the reactor, with less wear between the particles and the reactor, resulting in a long service life of the system. In addition, the composite particles are not easy to agglomerate and clog, and can be discharged by gravity without the need for a material conveying system, which is highly efficient and low-cost.

[0029] (5) The present invention transports the bottom ash of the circulating fluidized bed boiler, the fly ash of the circulating fluidized bed boiler dust collector, and the desulfurized gypsum of the circulating fluidized bed boiler desulfurization tower to a ball mill for ball milling. On the one hand, during the ball milling process, the CaSO4 in the desulfurized gypsum cooperates with the ball milling to destroy the Si-O bonds and Al-O bonds in the fly ash and bottom ash, which can promote the depolymerization of the aluminosilicate glass network, release active SiO2 and active Al2O3, and improve the volcanic ash activity of the ash. On the other hand, ball milling can reduce the particle size of the ash and desulfurized gypsum, which is convenient for subsequent granulation and molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process flow chart of the system in Example 1 of the present invention;

[0031] Figure 2 This is a process flow chart of the system of Example 2 of the present invention.

[0032] In the figure: material conveyor 1; ball mill 2; mixer 3; granulator 4; fixed bed reactor 5; insulation layer 6; rapper 7; flue gas inlet 8; flue gas outlet 9; fixed bed reactor feed port 10; fixed bed reactor discharge port 11; circulating fluidized bed boiler 12; dust collector 13; desulfurization tower 14; desulfurization tower outlet flue 15; flue gas induced draft fan inlet duct 16; flue gas induced draft fan 17; flue gas induced draft fan outlet duct 18; flue gas cooler inlet duct 19; flue gas cooler 20; flue gas cooler outlet duct 21; flue gas filter 22; flue gas filter outlet duct 23; flue gas compressor 24; flue gas compressor outlet duct 25; gas storage tank 26; gas storage tank outlet duct 27; exhaust duct 28; dust collector inlet flue 29; loader 30; particle conveyor 31; curing room 32. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1:

[0035] A CFB ash-desulfurized gypsum composite particle preparation and coal-fired flue gas CO2 mineralization system, the process flow chart of the system is as follows Figure 1 As shown, it includes a CFB ash-desulfurization gypsum composite particle preparation unit, a pressurized fixed bed adsorption unit, and a flue gas circulation unit;

[0036] The CFB ash-desulfurized gypsum composite particle preparation unit includes a circulating fluidized bed boiler 12, a dust collector 13, and a desulfurization tower 14 connected in parallel. The solid discharge ports of the three are connected to the inlet of the ball mill 2 through a material conveyor 1. The outlet of the ball mill 2 is connected to a mixer 3 and a granulator 4 in sequence; the discharge port of the granulator 4 is connected to a pressurized fixed bed adsorption unit; the flue gas outlet of the desulfurization tower 14 is connected to a flue gas circulation unit;

[0037] The pressurized fixed bed adsorption unit includes a fixed bed reactor 5, the discharge port of the granulator 4 is connected to the feed port at the top of the fixed bed reactor 5, the flue gas outlet 9 at the top of the fixed bed reactor is connected to the inlet of the dust collector 13, and the flue gas inlet 8 at the top of the fixed bed reactor 5 is connected to the flue gas circulation unit; two flue gas inlets 8 are provided at the top of the fixed bed reactor 5, which are respectively connected to two flue gas passages; a rapper 7 is provided at the middle and lower parts of the fixed bed reactor 5; an insulation layer 6 is provided on the side wall of the fixed bed reactor 5; a loader 30 is also provided between the feed port 10 of the fixed bed reactor and the discharge port of the granulator 4; the flue gas outlet of the circulating fluidized bed boiler 12 merges with the flue gas outlet 9 of the fixed bed reactor 5 and then passes into the dust collector 13.

[0038] The flue gas circulation unit includes two parallel flue gas passages, one of which is directly connected from the flue gas outlet of the desulfurization tower 14 to the flue gas inlet 8 of the fixed bed reactor 5 through the flue gas induced draft fan 17, and the other flue gas passage includes a flue gas cooler 20, a flue gas filter 22, a flue gas compressor 24 and an air storage tank 26 connected in sequence along the flue gas flow direction. The inlet of the flue gas cooler 20 is connected to the flue gas outlet of the desulfurization tower 14, and the outlet of the air storage tank 26 is connected to the flue gas inlet 8 at the top of the fixed bed reactor 5.

[0039] Among them, one end of the flue gas induced draft fan inlet pipe 16 is connected to the desulfurization tower outlet flue 15, and the other end is connected to the inlet of the flue gas induced draft fan 17; one end of the flue gas induced draft fan outlet pipe 18 is connected to the outlet of the flue gas induced draft fan 17, and the other end is connected to the flue gas inlet 8; one end of the flue gas cooler inlet pipe 19 is connected to the desulfurization tower outlet flue 15, and the other end is connected to the inlet of the flue gas cooler 20; one end of the flue gas cooler outlet pipe 21 is connected to the outlet of the flue gas cooler 20, and the other end is connected to the inlet of the flue gas filter 22; one end of the flue gas filter outlet pipe 23 is connected to the outlet of the flue gas filter 22, and the other end is connected to the inlet of the flue gas compressor 24; one end of the flue gas compressor outlet pipe 25 is connected to the outlet of the flue gas compressor 24, and the other end is connected to the inlet of the gas storage tank 26; one end of the gas storage tank outlet pipe 27 is connected to the outlet of the gas storage tank 26, and the other end is connected to the flue gas inlet 8; one end of the smoke exhaust pipe 28 is connected to the flue gas outlet 9, and the other end is connected to the dust collector inlet flue 29.

[0040] Example 2:

[0041] A CFB ash-desulfurized gypsum composite particle preparation and coal-fired flue gas CO2 mineralization system, the process flow chart of the system is as follows Figure 2 As shown, the content is basically the same as that of Example 1, except that: a composite particle curing unit is added to the system of Example 1; the composite particle curing unit includes a particle conveyor 31 and a curing chamber 32; the fixed bed reactor discharge port 11 is connected to the inlet of the particle conveyor 31; the outlet of the particle conveyor 31 is connected to the inlet of the curing chamber 32.

[0042] Example 3:

[0043] A method for preparing CFB ash-desulfurized gypsum composite particles and mineralizing CO2 from coal-fired flue gas using the system of Example 1 or Example 2, comprising the following specific steps:

[0044] (1) Preparation of CFB ash-desulfurized gypsum composite particles: The material conveyor 1 conveys the bottom ash of the circulating fluidized bed boiler 12, the fly ash of the dust collector 13, and the desulfurized gypsum of the desulfurization tower 14 to the ball mill 2 for ball milling (in terms of mass percentage, the amount of bottom ash is 45%, the amount of fly ash is 45%, and the amount of desulfurized gypsum is 10%). The ball-milled materials are conveyed by the material conveyor 1 to the mixer 3 for uniform mixing, and then conveyed to the granulator 4 for adding water (water-solid ratio is about 0.3) for granulation, thereby completing the preparation of CFB ash-desulfurized gypsum composite particles;

[0045] (2) Reactor feeding: The CFB ash-desulfurized gypsum composite particles prepared in step (2) are fed into the fixed bed reactor 5 through the fixed bed reactor feed port 10 by the feeder 30, and the fixed bed reactor feed port 10, the fixed bed reactor discharge port 11, the flue gas inlet 8 and the flue gas outlet 9 are closed;

[0046] (3) Flue gas CO2 mineralization: Open the flue gas inlet 8 of the fixed bed reactor induced draft fan, and send the desulfurized flue gas into the fixed bed reactor 5 through the flue gas induced draft fan 17. After the pressure of the fixed bed reactor 5 reaches 1kPa, close the flue gas inlet 8 of this route and stop the flue gas induced draft fan 17. This part of the flue gas can provide waste heat and H2O for the ash to adsorb CO2; open the flue gas inlet 8 of the fixed bed reactor flue gas compressor, and since the inlet flue gas temperature of the flue gas compressor cannot be too high, the flue gas at the outlet of the desulfurization tower 14 is first cooled by the flue gas cooler 20. The flue gas is cooled to below 30°C, filtered through the flue gas filter 22, and then enters the flue gas compressor 24 to send the compressed flue gas into the fixed bed reactor 5. After the pressure of the fixed bed reactor 5 reaches 1.5 MPa, the flue gas inlet 8 of this route is closed and the flue gas compressor 24 is stopped. At this time, the fixed bed reactor 5 is in a closed state. Under the pressure of 1.5 MPa, the alkali metal and alkaline earth metal oxides such as CaO in the CFB ash-desulfurization gypsum composite particles react with the CO2 and H2O in the coal-fired flue gas by utilizing the flue gas waste heat and the temperature rise of the compressor:

[0047] CaO+H2O→Ca(OH)2

[0048] Ca(OH)2+CO2→CaCO3+H2O

[0049] CaO+CO2→CaCO3

[0050] The reaction was stopped after about 1 hour, and CaO adsorbed CO2 to form dense CaCO3, which helped to improve the strength of the CFB ash-desulfurization gypsum composite particles.

[0051] (4) After the reaction is completed, the flue gas outlet 9 is opened, and the flue gas after the reaction returns to the dust collector inlet flue 29 through the exhaust pipe 28 and enters the dust collector 13 for dust removal, and then enters the desulfurization tower 14 for desulfurization and then is discharged; the CFB ash-desulfurization gypsum composite particles after the reaction are discharged from the fixed bed reactor discharge port 11, and the vibrator 7 is started during the discharge process to ensure that the composite particles are discharged quickly and smoothly.

[0052] Example 4:

[0053] Example 4 The CFB ash-desulfurization gypsum composite particles discharged in Example 3 are conveyed to the curing chamber 32 through the particle conveyor 31 for natural curing.

[0054] During the natural curing process, the unreacted CaO in the CFB ash-desulfurized gypsum composite particles hydrates to form Ca(OH)2. Under the combined excitation of Ca(OH)2 and CaSO4 in the desulfurized gypsum, the SiO2 and Al2O3 in the ash are excited and react with Ca(OH)2 to form CSH (calcium silicate hydrate) and CAH (calcium aluminate hydrate), which have gelling properties. At the same time, the CaSO4·2H2O in the desulfurized gypsum can react with Ca(OH)2 and Al2O3 or calcium aluminate to form ettringite (AFt), which improves the strength of the composite particles. In addition, Ca(OH)2 can also react with CO2 in the air to form CaCO3. At the same time, the CSH gel generated during the hydration process reacts with CO2 to form CaCO3, which further improves the strength of the composite particles. The main chemical equations involved in the natural curing process of CFB ash-desulfurized gypsum composite particles are as follows:

[0055] CaO+H2O→Ca(OH)2

[0056] xCa(OH)2+SiO2+yH2O→xCaO·SiO2·yH2O(CSH)

[0057] xCa(OH)2+Al2O3+yH2O→xCaO·Al2O3·yH2O(CAH)

[0058] Ca(OH)2+Al2O3+CaSO4·2H2O+H2O→Aft

[0059] 3CaO·Al2O3+CaSO4·2H2O+H2O→Aft

[0060] Ca(OH)2+CO2→CaCO3+H2O

[0061] xCaO·SiO2·yH2O+xCO2→xCaCO3+y(SiO2·tH2O)+(z-yt)H2O

[0062] The CFB ash-desulfurized gypsum composite particles produced by the present invention can replace part of the mineral raw materials such as quartz, clay, sand and gravel, etc., have certain economic benefits, and are conducive to the large-scale and resource utilization of circulating fluidized bed solid waste ash and desulfurized gypsum.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Those skilled in the art can modify or replace the technical solutions of the present invention according to the concept of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A CFB ash-desulfurized gypsum composite particle preparation and coal-fired flue gas CO2 mineralization system, characterized in that: It includes CFB ash-desulfurization gypsum composite particle preparation unit, pressurized fixed bed adsorption unit, and flue gas circulation unit; The CFB ash-desulfurized gypsum composite particle preparation unit includes a circulating fluidized bed boiler, a dust collector, and a desulfurization tower connected in parallel. The solid discharge ports of the three are connected to the inlet of the ball mill, and the outlet of the ball mill is connected to a mixer and a granulator in sequence; the granulator discharge port is connected to a pressurized fixed bed adsorption unit; the flue gas outlet of the desulfurization tower is connected to a flue gas circulation unit; The pressurized fixed bed adsorption unit includes a fixed bed reactor, the discharge port of the granulator is connected to the feed port at the top of the fixed bed reactor, the flue gas outlet at the top of the fixed bed reactor is connected to the dust collector inlet, and the flue gas inlet at the top of the fixed bed reactor is connected to the flue gas circulation unit; The flue gas circulation unit includes two parallel flue gas passages, one of which is directly connected from the flue gas outlet of the desulfurization tower to the flue gas inlet of the fixed bed reactor through an induced draft fan, and the other flue gas passage includes a flue gas cooler, a flue gas filter, a flue gas compressor and a gas storage tank connected in sequence along the flue gas flow direction. The inlet of the flue gas cooler is connected to the flue gas outlet of the desulfurization tower, and the outlet of the gas storage tank is connected to the flue gas inlet at the top of the fixed bed reactor.

2. The preparation of CFB ash-desulfurized gypsum composite particles and the system for CO2 mineralization of coal-fired flue gas according to claim 1 is characterized in that: The upper portion of the fixed bed reactor is provided with two flue gas inlets, which are respectively connected to two flue gas passages.

3. The preparation of CFB ash-desulfurized gypsum composite particles and the system for CO2 mineralization of coal-fired flue gas according to claim 1, characterized in that: The middle and lower parts of the fixed bed reactor are provided with rappers.

4. The preparation of CFB ash-desulfurized gypsum composite particles and the system for CO2 mineralization of coal-fired flue gas according to claim 1, characterized in that: The side wall of the fixed bed reactor is provided with a heat-insulating layer.

5. The preparation of CFB ash-desulfurized gypsum composite particles and the system for CO2 mineralization of coal-fired flue gas according to claim 1, characterized in that: A loading machine is also provided between the feed port of the fixed bed reactor and the discharge port of the granulator.

6. The preparation of CFB ash-desulfurized gypsum composite particles and the system for CO2 mineralization of coal-fired flue gas according to claim 1, characterized in that: The flue gas outlet of the circulating fluidized bed boiler is merged with the flue gas outlet of the fixed bed reactor and then flows into the dust collector.

7. The preparation of CFB ash-desulfurized gypsum composite particles and the system for CO2 mineralization of coal-fired flue gas according to claim 1, characterized in that: It also includes a composite particle curing unit; the composite particle curing unit includes a particle conveyor and a curing chamber; the discharge port of the fixed bed reactor is connected to the inlet of the particle conveyor, and further connected to the inlet of the curing chamber.

8. A method for preparing CFB ash-desulfurized gypsum composite particles and mineralizing CO2 from coal-fired flue gas using the system according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Preparation of CFB ash-desulfurized gypsum composite particles: The bottom ash, fly ash and desulfurized gypsum of the circulating fluidized bed boiler are mixed by a material conveyor, ball milled, stirred and granulated to obtain CFB ash-desulfurized gypsum composite particles; the amount of the bottom ash is 30% to 60%, the amount of the fly ash is 30% to 60%, and the amount of the desulfurized gypsum is 5% to 20% by weight; (2) Reactor feeding: The CFB ash-desulfurized gypsum composite particles are fed into the fixed bed reactor, and the feed port of the fixed bed reactor is closed. At this time, the fixed bed reactor is in a closed state; (3) Flue gas CO2 mineralization: First, desulfurized flue gas is introduced into the fixed bed reactor. When the pressure in the fixed bed reactor reaches 0.5-1.5 kPa, compressed flue gas is continuously introduced, so that the CFB ash-desulfurized gypsum composite particles and flue gas CO2 react under a pressure of 0.5-2.0 MPa, using H2O in the flue gas and the waste heat of the flue gas for 0.5-2 hours to achieve flue gas CO2 mineralization; (4) After the reaction is completed, the flue gas after the reaction is dedusted and desulfurized before being discharged, and the CFB ash-desulfurization gypsum composite particles after the reaction are discharged from the fixed bed reactor.

9. The method according to claim 4, characterized in that The fly ash is fly ash obtained after the flue gas of the circulating fluidized bed boiler and / or the fixed bed reactor is treated by a dust collector.

10. The method according to claim 4, characterized in that The method also includes curing of the composite particles: the CFB ash-desulfurization gypsum composite particles discharged in step (4) are transported to a curing room through a particle conveyor for natural curing.

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