Method and system device for purifying flue gas by powder adsorbent

Abstract

The application discloses a method and system device for purifying flue gas by powder adsorbent, which comprises the following steps: (1) recovering and reserving part of fly ash generated by fluidized bed boiler combustion; (2) mixing the fly ash reserved in step (1) with adsorbent to obtain mixed material; (3) extracting part of tail flue gas of the fluidized bed boiler, and further fluidizing and feeding the mixed material uniformly by using the tail flue gas; (4) conveying the mixed material after fluidization and feeding in step (3) to the furnace by using the tail flue gas as conveying medium to carry out harmful substance removal reaction, and the cycle is repeated. The application can effectively reduce the adhesion of the adsorbent, improve the conveying stability of the adsorbent, effectively improve the utilization rate of the adsorbent in the furnace, and further improve the flue gas purification efficiency of the fluidized bed boiler.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluidized bed combustion and flue gas purification, and particularly relates to a method and system device for purifying flue gas by feeding powder adsorbent into a furnace. BACKGROUND

[0002] With the continuous improvement of global environmental governance system requirements, the emission value requirements of harmful substances such as acid gases and heavy metals in flue gas discharged into the atmosphere are also becoming higher and higher. Therefore, reducing industrial boiler pollutant emissions is a crucial link in environmental protection work.

[0003] At present, the wet flue gas purification process system is complex, the engineering investment and operation cost are high, and there is a problem of subsequent wastewater reprocessing. The dry flue gas purification system has obvious improvement on the above-mentioned disadvantages of the wet flue gas purification system. In the dry flue gas purification process, limestone and other solid materials are usually used as adsorbents for adsorption and removal of harmful substances in flue gas. However, the solid adsorbent such as limestone is easy to stick and aggregate in the pipeline during transportation, causing pipeline blockage and affecting the efficiency of powder adsorbent in purifying flue gas. It is still necessary to seek a method and system device to solve such problems.

[0004] In the invention patent CN109731472 A, an energy-saving boiler flue gas purification system and method are disclosed. The purification system reasonably allocates process steps to sequentially carry out desulfurization, dust removal and denitrification of flue gas. The flue gas purification system disclosed in the invention cools the flue gas through a first heat exchanger, and then heats the flue gas through a second heat exchanger and an air heater, so that the following flue gas denitrification process can be carried out quickly and smoothly. The heat of the flue gas in the system and the heat of the heating device are fully utilized in the whole process. At the same time, the heat in the hot gas discharged from the SCR reactor and the air preheater is also reused, greatly reducing the heat loss of the system and saving purification energy. The invention also transfers the high heat of some working areas to the areas where biological treatment is needed, so that the desulfurization process, denitrification process and dust removal process can be carried out in the appropriate temperature range, improving the effect of flue gas purification. However, the system given by the invention is relatively complex, the engineering investment and operation cost are high, and equipment corrosion is easy to occur.

[0005] An energy-saving biomass boiler flue gas purification system is disclosed in Utility Model CN210251828U, which comprises a cyclone dust collector, a deacidification tower connected with the outlet pipeline of the cyclone dust collector, an SCR reactor connected with the outlet pipeline of the deacidification tower, and a chimney connected with the outlet pipeline of the SCR reactor; the top of the deacidification tower is connected with a baking soda powder bin through a pipeline; a bag-type dust collector is arranged between the deacidification tower and the SCR reactor. The utility model sets up a cyclone dust removal + bag-type dust removal two-stage dust removal device, and sets up a deacidification tower between the two dust removal devices, and sets up an SCR reactor after the second dust removal, which can effectively guarantee the efficient, stable and safe operation of the purification system, and sets up a smoke cooler in front of the chimney, which effectively improves the system heat energy utilization rate. However, this system does not consider the problem that baking soda is easy to stick in the pipeline conveying process.

[0006] In summary, it is still necessary to develop a method and system for avoiding the easy sticking of the adsorbent for injection in the fluidized bed boiler during the conveying process, to improve the conveying stability of the adsorbent, improve the utilization rate of the adsorbent in the fluidized bed boiler, and thus achieve the purpose of improving the flue gas purification efficiency of the industrial boiler. SUMMARY

[0007] The present application solves the technical problem that the powder adsorbent for injection in the existing fluidized bed boiler system is easy to stick during the conveying process, which leads to low flue gas purification efficiency of the fluidized bed boiler; a method and system device for purifying flue gas by powder adsorbent injection are proposed, which can effectively reduce the stickiness of the adsorbent, improve the conveying stability of the adsorbent, improve the utilization rate of the adsorbent in the fluidized bed boiler, and thus improve the flue gas purification efficiency of the fluidized bed boiler.

[0008] To achieve the above purpose, the following technical scheme is adopted in the present application:

[0009] A method for purifying flue gas by powder adsorbent injection, comprising the following steps:

[0010] (1) recovering and storing part of the fly ash generated by the combustion of the fluidized bed boiler;

[0011] (2) mixing the fly ash stored in step (1) with the adsorbent to obtain a mixture;

[0012] (3) extracting part of the high-temperature tail flue gas of the fluidized bed boiler, and using the tail flue gas to further fluidize and discharge the mixture in step (2);

[0013] (4) using the tail flue gas as the conveying medium to convey the fluidized and discharged mixture in step (3) to the fluidized bed boiler for harmful substance removal reaction, and so on.

[0014] The application can effectively reduce the adhesion of the absorbent, thereby facilitating the transportation of the absorbent in the pipeline, and can improve the utilization rate of the absorbent in the fluidized bed boiler, thereby achieving the technical effect of improving the flue gas purification efficiency of the fluidized bed boiler.

[0015] The fly ash used in the application is separated from the flue gas generated after combustion of the fluidized bed boiler, is a high-temperature and dry powder material, and therefore mixing the fly ash with the absorbent can greatly reduce the adhesion of the absorbent, thereby effectively avoiding the problem of adhesion and agglomeration of the absorbent during pipeline transportation, improving the utilization rate of the absorbent in the fluidized bed boiler, and further improving the purification effect of the flue gas in the fluidized bed boiler. At the same time, since the fly ash separated from the flue gas of the fluidized bed boiler contains some unreacted absorbent, the unreacted absorbent remaining in the fly ash can be mixed with new absorbent and then recycled into the fluidized bed boiler for secondary reaction, thereby further improving the utilization rate of the absorbent remaining in the fly ash.

[0016] The application uses the tail flue gas generated by the fluidized bed boiler to fluidize and feed the fly ash and the absorbent. Since the tail flue gas generated by the fluidized bed boiler is a high-temperature gas, the adhesion of the absorbent can be further reduced. In addition, the high-temperature tail flue gas can further avoid the phenomenon of blockage caused by excessive adhesion of the absorbent in the pipeline during the process of transporting the fly ash and the absorbent into the fluidized bed boiler.

[0017] On the basis of the above technical solution, the application can be further improved as follows.

[0018] As a preferred technical solution of the application, in step (1), part of the fly ash generated by the combustion of the fluidized bed boiler is discharged from the system, and the other part is recycled and stored. The recycled and stored fly ash is all used for mixing with the absorbent and transporting into the fluidized bed boiler.

[0019] As a preferred technical solution of the application, in step (2), the mass flow rate ratio of the fly ash to the absorbent is 3: (5-10).

[0020] As a preferred technical solution of the application, in steps (3) and (4), the tail flue gas is in the form of flue gas fluidization air and flue gas transportation supplementary air, respectively, for fluidizing and feeding the mixed material and transporting the mixed material.

[0021] As a preferred technical solution of the application, the calculation formula of the flue gas fluidization air volume is:

[0022] ;

[0023] wherein, the Q f is the flue gas fluidization air volume, the u mf is the minimum fluidization velocity of the mixture in step (3), the A 1 is the horizontal cross-sectional area of the tank at the discharge port of the fluidized feed tank;

[0024] The calculation formula of the flue gas conveying make-up air volume is:

[0025] ;

[0026] wherein, Q s is the flue gas conveying make-up air volume, u c is the flue gas conveying air speed of the mixture in step (4), A 2 represents the cross-sectional area of the mixture conveying pipeline;

[0027] The u c is 8-20 times of the suspension velocity of the mixture u l .

[0028] As a preferred technical solution of the present application, in step (4), the conveying flow rate of the mixture is monitored on-line during the conveying of the mixture to the fluidized bed boiler, and the tail flue gas flow rate is adjusted according to the conveying flow rate of the mixture to ensure the stability of the conveying flow rate of the mixture.

[0029] A system device for purifying flue gas by feeding powder adsorbent into a furnace, comprising an adsorbent storage bin, a fly ash storage bin, a drum mixer, a fluidized feed tank, a fluidized bed boiler, a cyclone separator and a flue gas circulation system;

[0030] The adsorbent storage bin and the fly ash storage bin are respectively connected to the drum mixer through pipelines;

[0031] The drum mixer, the fluidized feed tank, the fluidized bed boiler and the cyclone separator are sequentially connected through pipelines;

[0032] The fly ash discharge port of the cyclone separator is connected to the fly ash storage bin through a pipeline, and the flue gas outlet of the cyclone separator is connected to the fluidized feed tank through the flue gas circulation system.

[0033] The application can effectively solve the technical problem that the adsorbent is easy to be bonded in the fluidized bed boiler system, effectively reduce the bonding property of the adsorbent, improve the stability of the adsorbent transportation, improve the utilization rate of the adsorbent in the fluidized bed boiler, and improve the technical effect of the flue gas purification efficiency of the fluidized bed boiler.

[0034] On the basis of the above technical solution, the application can be further improved as follows.

[0035] As a preferred technical solution of the application, the first mass flow meter is arranged on the pipeline between the adsorbent storage bin and the drum mixer and on the pipeline between the fly ash storage bin and the drum mixer.

[0036] As a preferred technical solution of the application, the flue gas circulation system comprises a fan and a gas distribution tank, the air inlet of the fan is connected with the flue gas outlet of the cyclone separator through a pipeline, the air outlet of the fan is connected with the air inlet of the gas distribution tank through a pipeline, the gas distribution tank is provided with a flue gas fluidization air pipe and a flue gas transportation supplementary air pipe, the bottom end of the fluidization and feeding tank is provided with a flue gas fluidization air inlet, the flue gas fluidization air pipe is connected with the flue gas fluidization air inlet, the sidewall of the fluidization and feeding tank is provided with a discharge port, and the flue gas transportation supplementary air pipe is connected with the discharge port.

[0037] As a preferred technical solution of the application, the flue gas fluidization air pipe and the flue gas transportation supplementary air pipe are both provided with a gas flow meter.

[0038] As a preferred technical scheme of the present application, the fluidized bed boiler flue gas purification system further comprises a feedback system, the feedback system comprises a valve, a controller, a computer and a second mass flow meter, the valve is arranged on a pipeline between an air outlet of the fan and an air inlet of the gas distribution tank, the controller is in electrical signal connection with the valve, the computer is in electrical connection with the controller and the second mass flow meter respectively, and the second mass flow meter is arranged on a pipeline between the fluidized material feeding tank and the fluidized bed boiler.

[0039] The present application has the following beneficial effects:

[0040] (1) The present application can effectively reduce the adhesion of the adsorbent, improve the stability of the adsorbent conveying, improve the utilization rate of the adsorbent in the fluidized bed boiler, and thus improve the efficiency of the fluidized bed boiler flue gas purification by mixing part of the high-temperature and dry fly ash generated after combustion of the fluidized bed boiler with the adsorbent.

[0041] (2) The present application can further reduce the adhesion of the adsorbent, improve the stability of the adsorbent conveying, improve the utilization rate of the adsorbent in the fluidized bed boiler, and thus improve the efficiency of the fluidized bed boiler flue gas purification by fluidizing the mixture of fly ash and adsorbent driven by high-temperature tail flue gas generated by the fluidized bed boiler and then conveying it into the fluidized bed boiler for reaction.

[0042] (3) The present application can effectively reduce the waste of adsorbent caused by incomplete reaction in the fluidized bed boiler, and effectively reduce the energy consumption in the process of conveying the adsorbent.

[0043] (4) The feedback system provided in the present application ensures that the flue gas circulation system can provide sufficient tail flue gas for the fluidized material feeding tank in real time, so that the entire powder adsorbent flue gas purification system device can continuously and efficiently operate. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a structural connection schematic diagram of the powder adsorbent flue gas purification system device of the present application;

[0045] Explanation of symbols in the figure:

[0046] adsorbent storage bin 1, fly ash storage bin 2, drum mixer 3, fluidized material feeding tank 4, fluidized bed boiler 5, cyclone separator 6, flue gas circulation system 7, fan 7-1, gas distribution tank 7-2, flue gas fluidization air pipe 7-3, flue gas conveying and supplementary air pipe 7-4, gas flow meter 7-5, first mass flow meter 8, feedback system 9, valve 9-1, controller 9-2, computer 9-3, second mass flow meter 9-4. DETAILED DESCRIPTION

[0047] The embodiment of the present application provides a method and system device for purifying flue gas by powder adsorbent into a furnace, so as to solve the technical problem of low flue gas purification efficiency of the fluidized bed boiler caused by the adhesion of the adsorbent in the pipeline conveying process in the prior art, and effectively reduce the adhesion of the adsorbent in the pipeline conveying process, so as to improve the flue gas purification efficiency of the fluidized bed boiler.

[0048] The general idea adopted by the present application is as follows:

[0049] The present application can effectively reduce the adhesion of the adsorbent in the conveying and reaction process, improve the conveying stability of the adsorbent, improve the utilization rate of the adsorbent in the fluidized bed boiler, and thus improve the flue gas purification efficiency of the fluidized bed boiler.

[0050] 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 is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0051] A method for purifying flue gas by powder adsorbent into a furnace, comprising the following steps:

[0052] (1) recovering and reserving part of the fly ash generated by the combustion of the fluidized bed boiler;

[0053] (2) mixing the fly ash reserved in step (1) with the adsorbent to obtain a mixture;

[0054] (3) extracting part of the tail flue gas of the fluidized bed boiler, and further fluidizing and feeding the mixture in step (2) by using the tail flue gas;

[0055] (4) transporting the mixture fluidized and fed in step (3) into the fluidized bed boiler by using the tail flue gas as the transport medium to carry out the harmful substance removal reaction, and the cycle is repeated.

[0056] In the present embodiment, part of the fly ash generated by the combustion of the fluidized bed boiler is discharged from the system, and the other part is recovered and reserved. The recovered and reserved fly ash is all used for mixing with the adsorbent and transported into the furnace.

[0057] To avoid the low efficiency of flue gas purification in the fluidized bed boiler caused by too much fly ash and too little adsorbent, and to avoid the problem that the adhesion of the adsorbent cannot be effectively reduced caused by too little fly ash, the mass flow ratio of the fly ash to the adsorbent in the step (2) is 1:3. It is worth noting that in the actual application process, the mass flow ratio of the fly ash to the adsorbent is not limited to the above-mentioned 1:3, and the person skilled in the art can determine the mass flow ratio of the fly ash to the adsorbent according to the actual needs, for example, it can also be 3:(5-10).

[0058] To further improve the mixing uniformity between the fly ash and the adsorbent and maximize the adhesion of the adsorbent, the tail flue gas in the steps (3) and (4) is in the form of flue gas fluidization wind and flue gas conveying supplementary wind to fluidize and discharge the mixture, respectively. The flue gas fluidization wind enters the fluidized discharge tank from the bottom end of the tank to make the internal material of the tank have fluid characteristics, prevent the material from adhering, and easily flow and convey, while the flue gas conveying supplementary wind enters the pipeline between the fluidized discharge tank and the fluidized bed boiler from the discharge port of the tank to supplement the conveying air volume in the pipeline.

[0059] In use, to enable the mixture to have better fluidization effect, the calculation formula of the flue gas fluidization wind volume is:

[0060] ;

[0061] Wherein, the Q f is the flue gas fluidization wind volume, the u mf is the minimum fluidization velocity of the mixture in the step (3), and the A 1 is the horizontal cross-sectional area of the tank at the discharge port of the fluidized discharge tank;

[0062] The calculation formula of the flue gas conveying supplementary wind volume is:

[0063] ;

[0064] Wherein, Q s is the flue gas conveying supplementary wind volume, u c is the flue gas conveying wind speed of the mixture in the step (4), A 2 is the cross-sectional area of the conveying pipeline of the mixture; and the u c is the suspension velocity of the mixture u l 8-20 times.

[0065] In this embodiment, the horizontal cross-sectional area of ​​the fluidized bed feeder at the outlet is... A 1 It is 0.12m 2 The minimum fluidization rate of the mixture of 800-mesh kaolin and fly ash used. u mf The flow rate is 0.05 m / s. During implementation, the mixture is stably fluidized and fed in a fluidized feeding tank at three times its minimum fluidization velocity to obtain the extracted flue gas flow rate. Q f It is 64.8m 3 / h. The diameter d of the mixed material conveying pipeline is 0.065m, and the cross-sectional area is... A 2 3.32×10 -3 m 2 The suspension velocity of the mixture is 0.8 m / s. Taking the flue gas conveying wind speed as 15 times the suspension velocity of the mixture, the flue gas conveying wind speed is obtained. u c The speed is 12 m / s, and the extracted flue gas transport volume is 143.42 m³ / s. 3 / h Wherein, the flue gas conveying air volume is provided by the flue gas aerosolization air volume and the flue gas conveying supplementary air volume, therefore, the flue gas conveying supplementary air volume extracted in this embodiment Q s It is 78.62m 3 / h.

[0066] To ensure the stability of the mixed material conveying flow rate, in step (4), during the process of conveying the mixed material to the fluidized bed boiler, the conveying flow rate of the mixed material is monitored online. The conveying flow rate of the mixed material varies with the amount of fuel in the fluidized bed boiler. When the amount of fuel conveyed in the fluidized bed boiler increases, the conveying amount of the mixed material needs to be increased; when the amount of fuel conveyed in the fluidized bed boiler decreases, the conveying amount of the mixed material needs to be reduced. At the same time, the tail flue gas flow rate is adjusted according to the conveying flow rate of the mixed material to ensure that the conveying flow rate of the mixed material is always kept within a predetermined range.

[0067] To achieve the above-mentioned flue gas purification method, this embodiment also provides a system device for purifying flue gas using a powdered adsorbent, such as... Figure 1 As shown, it includes an adsorbent storage silo 1, a fly ash storage silo 2, a drum mixer 3, a fluidized feeding tank 4, a fluidized bed boiler 5, a cyclone separator 6, and a flue gas recirculation system 7;

[0068] The adsorbent storage bin 1 and the fly ash storage bin 2 are connected with the drum mixer 3 through pipes respectively, and in use, the materials in the adsorbent storage bin 1 and the fly ash storage bin 2 are delivered to the drum mixer 3 according to the set proportion for mixing;

[0069] The drum mixer 3, the fluidized material tank 4, the fluidized bed boiler 5 and the cyclone 6 are connected in sequence through pipes, and in use, the mixed materials in the drum mixer 3 are delivered to the fluidized material tank through pipes for fluidized material; the materials in the fluidized material tank 4 after fluidized material are delivered to the fluidized bed boiler 5 through pipes for harmful substance removal reaction; the flue gas generated after combustion in the fluidized bed boiler 5 is delivered to the cyclone 6 through pipes for tail flue gas and fly ash separation;

[0070] The fly ash outlet of the cyclone 6 is connected with the fly ash storage bin 2 through pipes for delivering part of the separated fly ash to the fly ash storage bin 2 for storage and standby use, and it is worth noting that the fly ash outlet of the cyclone 6 is also provided with a fly ash discharge channel for discharging excess fly ash; the flue gas outlet of the cyclone 6 is connected with the fluidized material tank 4 through the flue gas circulation system 7, and in use, the flue gas circulation system 7 delivers the tail flue gas separated from the cyclone 6 to the fluidized material tank 4 for fluidized material of the materials inside, and at the same time, delivers the materials after fluidized material to the fluidized bed boiler 5.

[0071] In order to ensure that the mass flow ratio between the fly ash and the adsorbent is kept within the set range, the pipes between the adsorbent storage bin 1 and the drum mixer 3 and the pipes between the fly ash storage bin 2 and the drum mixer 3 are both provided with first mass flow meters 8.

[0072] In order to further improve the mixing uniformity between fly ash and adsorbent, and minimize the adhesion of adsorbent, the flue gas circulation system 7 respectively in the form of flue gas fluidization wind and flue gas conveying supplementary wind to the fluidized feeding tank 4 to transport tail flue gas, in order to achieve the above effect, the specific structure of the flue gas circulation system 7 is that the flue gas circulation system 7 includes a fan 7-1 and a gas distribution tank 7-2, the air inlet of the fan 7-1 is connected with the cyclone separator 6 through a pipeline, the air outlet of the fan 7-1 is connected with the gas inlet of the gas distribution tank 7-2 through a pipeline, in use, the fan 7-1 transports the tail flue gas separated from the cyclone separator 6 into the gas distribution tank 7-2; at the same time, it is worth noting that in the actual manufacturing process, the air outlet of the fan 7-1 is also provided with an air outlet channel for directly discharging excess tail flue gas; the gas distribution tank 7-2 is provided with a flue gas fluidization wind pipe 7-3 and a flue gas conveying supplementary wind pipe 7-4, the bottom end of the fluidized feeding tank 4 is provided with a flue gas fluidization wind inlet (not marked in the figure), the flue gas fluidization wind pipe 7-3 is connected with the flue gas fluidization wind inlet, so as to transport the flue gas fluidization wind from the bottom end of the fluidized feeding tank 4 into the fluidized feeding tank 4; the sidewall of the fluidized feeding tank 4 is provided with a discharge port, the flue gas conveying supplementary wind pipe 7-4 is connected with the discharge port.

[0073] In order to monitor the flow of flue gas fluidization wind and flue gas conveying supplementary wind in real time, the flue gas fluidization wind pipe 7-3 and the flue gas conveying supplementary wind pipe 7-4 are both provided with a gas flow meter 7-5.

[0074] In order to ensure that the flue gas circulation system 7 can provide sufficient tail flue gas for the fluidized feeding tank 4 in real time, so as to continuously and efficiently operate the whole fluidized bed boiler flue gas purification system, the fluidized bed boiler flue gas purification system further includes a feedback system 9, the feedback system includes a valve 9-1, a controller 9-2, a computer 9-3 and a second mass flow meter 9-4, the valve 9-1 is arranged on the pipeline between the air outlet of the fan 7-1 and the gas inlet of the gas distribution tank 7-2, the controller 9-2 is electrically connected with the valve 9-1, the computer 9-3 is electrically connected with the controller 9-2 and the second mass flow meter 9-4 respectively, and the second mass flow meter 9-4 is arranged on the pipeline between the fluidized feeding tank 4 and the fluidized bed boiler 5; in use, the second mass flow meter 9-4 is used for online monitoring the mass flow of the material transported into the fluidized bed boiler 5, and the detection result is transmitted to the computer 9-3 in real time, when the mass flow of the transported material changes with the change of the fuel in the fluidized bed boiler, the computer 9-3 transmits a control signal to the controller 9-2, and the opening of the valve 9-1 is controlled by the controller 9-2, so as to adjust the mass flow of the material transported from the fluidized feeding tank 4 to keep within a predetermined range.

[0075] It should be noted that the above-mentioned embodiments are merely used for explaining the present application, but not for limiting the present application. Moreover, based on the above-mentioned embodiments, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary or possible to enumerate all the embodiments. The obvious changes or variations derived from the above-mentioned embodiments are still within the protection scope of the present application.

Claims

1. A method for purifying flue gas by powder adsorbent injection, characterized by: It comprises the following steps: (1) recovering and reserving part of the fly ash produced by fluidized bed boiler combustion; (2) mixing the fly ash reserved in step (1) with the adsorbent to obtain a mixture; the mass flow ratio of the fly ash to the adsorbent is 3:5-3:10; (3) extracting part of the high-temperature tail flue gas of the fluidized bed boiler, and further fluidizing the mixture in step (2) with the tail flue gas; (4) using the tail flue gas as the conveying medium to convey the mixture fluidized in step (3) into the fluidized bed boiler for harmful substance removal reaction, and so on; Wherein, the tail flue gas in step (3) and step (4) respectively takes the form of flue gas fluidization air and flue gas conveying make-up air to fluidize and discharge the material; The calculation formula of the flue gas fluidization air volume is: ； Wherein, the Q f is the flue gas fluidization air volume, the u mf is the minimum fluidization velocity of the mixture in step (3), the A 1 is the horizontal cross-sectional area of the tank at the discharge port of the fluidized feed tank; The calculation formula of the flue gas conveying make-up air volume is: ； wherein, Q s the air volume for the flue gas conveying air supplement, u c the air velocity for the flue gas conveying air for mixing the materials in step (4), A 2 represents the cross-sectional area of the material mixing conveying pipeline. The u c For the suspension velocity of the mixture u l 8-20 times.

2. The method according to claim 1, wherein the powder adsorbent is a powder adsorbent according to any one of claims 1 to 3. In step (1), part of the fly ash produced by fluidized bed boiler combustion is discharged from the system, and the other part is recovered and reserved, and all the recovered and reserved fly ash is used for mixing with the adsorbent and conveying into the fluidized bed boiler.

3. A method of purifying flue gas by injecting a powder adsorbent according to claim 1, characterized in that: In step (4), the conveying flow of the mixture is monitored online during the conveying of the mixture into the fluidized bed boiler, and the tail flue gas flow is adjusted according to the conveying flow of the mixture to ensure the stability of the conveying flow of the mixture.

4. A system device for purifying flue gas using powdered adsorbents, characterized in that: It comprises an adsorbent storage bin (1), a fly ash storage bin (2), a drum mixer (3), a fluidized discharge tank (4), a fluidized bed boiler (5), a cyclone separator (6) and a flue gas circulation system (7); The adsorbent storage bin (1) and the fly ash storage bin (2) are connected with the drum mixer (3) through pipelines respectively; The drum mixer (3), the fluidized discharge tank (4), the fluidized bed boiler (5) and the cyclone separator (6) are connected through pipelines in sequence; The fly ash discharge port of the cyclone separator (6) is connected with the fly ash storage bin (2) through a pipeline, and the flue gas outlet of the cyclone separator (6) is connected with the fluidized discharge tank (4) through the flue gas circulation system (7); The flue gas circulation system (7) comprises a fan (7-1) and a gas distribution tank (7-2), the air inlet of the fan (7-1) is connected with the flue gas outlet of the cyclone separator (6) through a pipeline, the air outlet of the fan (7-1) is connected with the gas inlet of the gas distribution tank (7-2) through a pipeline, the gas distribution tank (7-2) is provided with a flue gas fluidization air pipe (7-3) and a flue gas conveying make-up air pipe (7-4), the bottom end of the fluidized discharge tank (4) is provided with a flue gas fluidization air inlet, the flue gas fluidization air pipe (7-3) is connected with the flue gas fluidization air inlet, the sidewall of the fluidized discharge tank (4) is provided with a discharge port, and the flue gas conveying make-up air pipe (7-4) is connected with the discharge port.

5. A system for purifying flue gas by injecting a powder adsorbent according to claim 4, characterized in that: First mass flow meters (8) are arranged on the pipelines between the adsorbent storage bin (1) and the drum mixer (3) and between the fly ash storage bin (2) and the drum mixer (3).

6. A system for cleaning flue gas by injecting a powder sorbent according to claim 4, wherein: Gas flow meters (7-5) are arranged on the flue gas fluidization air pipe (7-3) and the flue gas conveying make-up air pipe (7-4).

7. A system for flue gas cleaning by powder sorbent injection according to claim 4, characterized in that: Further comprising a feedback system (9), the feedback system (9) comprising a valve (9-1), a controller (9-2), a computer (9-3) and a second mass flow meter (9-4), the valve (9-1) being arranged on a pipeline between an air outlet of the fan (7-1) and an air inlet of the gas distribution tank (7-2), the controller (9-2) being in electrical signal connection with the valve (9-1), the computer (9-3) being in electrical signal connection with the controller (9-2) and the second mass flow meter (9-4) respectively, and the second mass flow meter (9-4) being arranged on a pipeline between the fluidized feeding tank (4) and the fluidized bed boiler (5).

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