CN110252051B - Method for dedusting, desulfurizing and denitrating boiler flue gas and removing dioxin - Google Patents

Abstract

The invention discloses a method for dust removal, desulfurization, denitrification and dioxin removal from boiler flue gas. Hydrogen salt, reaction; after adding a reducing agent to the reacted flue gas, it enters the denitration composite dust removal device for denitration, dioxin removal and dust removal; the denitration composite dust removal device includes a shell, a partition plate and a number of basalt rocks The fiber filter cartridge, the partition plate is arranged on the cross section of the casing, and the casing is divided into a first chamber and a second chamber, the side wall of the casing of the first chamber is provided with a smoke inlet, and the second chamber is A flue gas outlet is arranged on the side wall of the housing of the chamber; each basalt fiber filter cartridge is a hollow tube body, and the basalt fiber wool is bonded with a catalyst; In one chamber, the opening of each basalt fiber filter cartridge communicates with the second chamber.

Description

Method for dust removal, desulfurization, denitrification and dioxin removal from boiler flue gas

technical field

The invention belongs to the technical field of dust removal, desulfurization and denitrification of flue gas, and particularly relates to a method for dust removal, desulfurization and denitrification of boiler flue gas and removal of dioxins.

Background technique

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

my country is a big agricultural country with abundant biomass raw materials, which can be used in large quantities in the power generation industry; the emission of nitrogen and sulfur oxides in flue gas is large, but the treatment is not enough, causing serious ecological problems. Therefore, how to deal with nitrogen and sulfur oxides in flue gas and reduce their harm to the environment is imminent.

The traditional desulfurization, denitrification and dust removal methods are mostly wet flue gas process/dry flue gas process and bag dust removal process. The product of the wet process is liquid or sludge, which is difficult to handle, the equipment is seriously corrosive, the flue gas needs to be reheated after washing, the energy consumption is high, the floor space is large, and the investment and operating costs are high. Calcium sulfite and calcium sulfate generated after absorbing sulfur dioxide with calcium-based desulfurizer are easy to form scaling and blockage in the desulfurization tower and pipeline due to their low solubility. The dry process desulfurization efficiency is low, the utilization rate of absorbent is low, the phenomenon of wear and scaling is serious, the equipment maintenance is more difficult, the stability and reliability of equipment operation are not high, and the service life is short, which limits this problem. application of a method.

There are three main types of flue gas simultaneous desulfurization and denitrification technologies. The first type is the combined technology of flue gas desulfurization and flue gas denitrification; the second type is to use adsorbents to simultaneously remove SO _X and NO _X ; The gas desulfurization system is modified (such as adding denitrification agent to the desulfurization liquid, etc.) to increase the denitration function.

Wet addition of metal catalysts: Wet desulfurization can remove more than 90% of SO ₂ , but due to the low solubility of NO in water, it has almost no removal effect on NO. Some metal catalysts, such as Fe(11)-EDTA, can react rapidly with dissolved NOx and have the effect of promoting NOx absorption. A company in the United States used 6% magnesia-enhanced lime as the desulfurizer, and added Fe(II)-EDTA to the desulfurization solution to conduct a pilot-scale study on simultaneous desulfurization and denitrification, and achieved a denitrification rate of more than 60% and a desulfurization rate of about 99%. Rate. The disadvantage of the wet FGD plus metal catalyst process is that the catalyst is lost during the reaction, and its recycling is difficult, resulting in high operating costs.

The bag filter is a dry dust filter device. It is suitable for capturing fine, dry, non-fibrous dust. The filter bag is made of woven filter cloth or non-woven felt, and uses the filtering effect of fiber fabric to filter the dust-laden gas. The action settles down and falls into the ash hopper. When the gas containing finer dust passes through the filter material, the dust is blocked and the gas is purified. However, the inventor found that the bag filter has many shortcomings, such as: (1) During the daily operation of the bag filter, due to certain changes in operating conditions or certain failures, the normal operation and work of the equipment will be affected. poor performance and operating stability; ② can not adapt to the high temperature, acid and alkali corrosion environment of biomass power plants; ③ bag filter is prone to combustion, explosion and fire accidents.

In addition, for some flue gas containing a large amount of dioxins, such as waste boiler flue gas, the removal method of dioxins is generally to use activated carbon adsorption and bag filter, but activated carbon adsorption has the following disadvantages: 1) Activated carbon It needs to be equipped with an expensive injection device, and the removal efficiency is affected by the fluctuation of the feeding work; 2) The activated carbon adsorbs dioxins, but the total amount is not reduced by transferring it to the fly ash; 3) The adsorption efficiency of activated carbon is related to the specific surface area of activated carbon and smoke It is closely related to factors such as the degree of gas mixing, and it is difficult to stabilize and completely control the process; 4) The fly ash contains dioxins and needs to be sent to a hazardous waste treatment plant for reprocessing to prevent dioxins from escaping again; 5) Due to carbon 6) Activated carbon plays a role of adsorption, not decomposition, and the staff is in a dangerous environment.

SUMMARY OF THE INVENTION

In view of the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a method for dust removal, desulfurization, denitrification and dioxin removal of boiler flue gas. The method can effectively remove dust particles, sulfides, nitrogen oxides, dioxins, dioxins and other pollutants in the flue gas, and can be widely used in biomass boilers, garbage boilers, coking furnaces, hazardous waste incinerators, etc.

In order to solve the above technical problems, the technical scheme of the present invention is:

A method for dust removal, desulfurization, denitrification and dioxin removal from boiler flue gas, comprising the following steps:

The flue gas with a temperature of 250-350 ℃ is drawn from the boiler, and 600-700 mesh bicarbonate is sprayed into the flue gas to react;

After adding a reducing agent to the reacted flue gas, it enters the denitration composite dust removal device for denitration, dioxin removal and dust removal;

The denitration composite dust removal device includes a shell, a partition plate and several basalt fiber filter cartridges. The partition plate is arranged on the cross section of the shell to separate the shell into a first chamber and a second chamber. A fume inlet is provided on the side wall of the housing of the chamber, and a fume outlet is provided on the side wall of the housing of the second chamber;

Each basalt fiber filter cartridge is a hollow tube body, and the tube body wall is a filter cartridge structure bonded by basalt fiber wool. The basalt fiber wool is bonded with a catalyst, one end of which is sealed and the other end is open;

Each basalt fiber filter cartridge is installed on the partition plate, and is located in the first chamber as a whole, and the opening of each basalt fiber filter cartridge is communicated with the second chamber;

The flue gas after adding the reducing agent enters from the flue gas inlet, flows into the second chamber after filtering and catalytic reaction, and flows out through the flue gas outlet.

The particle size of 600-700 mesh is about 20-30μm. The ultra-fine powder baking soda particles have a huge specific surface area. At a reasonable flue gas temperature, they are rapidly decomposed into fresh sodium carbonate when heated, and the newly decomposed sodium carbonate, The surface activity is very high, and it has a strong ability to react with acidic substances, and it quickly reacts with acidic substances in flue gas such as SO ₂ , SO ₃ , HF, HCl, etc. For example, it reacts with SOx in the flue gas to generate sodium sulfite and sodium sulfate. The control system controls the emission value of flue gas desulfurization by adjusting the amount of desulfurizer (sodium bicarbonate) added. The reaction process of desulfurization occurs in two steps, one is the contact process between the desulfurizer and the flue gas in the desulfurization reactor, and the other is the incompletely reacted desulfurizer attached to the outside of the basalt fiber filter cartridge of the subsequent denitration composite dust removal device. Continue to contact and react with the flue gas, reduce the concentration of sulfur dioxide in the flue gas, and reduce the production of ABS (ammonium hydrogen sulfate).

After adding reducing agent to the flue gas after desulfurization, it enters the denitration composite dust removal device. During the process of flowing from the first chamber through the basalt fiber filter to the second chamber, the dust in the flue gas is filtered by the basalt fiber filter. The filtered flue gas enters the inside of the basalt fiber filter cartridge, contacts with the catalyst on the wall of the basalt fiber filter cartridge, and undergoes a catalytic reaction to denitrify and remove dioxins. The dust forms a certain thickness of dust layer on the outer wall of the basalt fiber filter cartridge, which can poison the heavy metal metals arsenic (As), selenium (Se), mercury (Hg) and the alkali metals Na ₂ O and K ₂ O in the flue gas. , thereby reducing the toxic effect of these substances on the catalyst, prolonging the service life of the catalyst, and enabling the catalyst to maintain high-efficiency activity for a long time.

The basalt fiber filter cartridge can also intercept the bicarbonate desulfurizer and continue to react with the sulfur dioxide in the flue gas to improve the removal efficiency of sulfur dioxide.

The denitrification principle is:

4NO+4NH ₃ +O ₂ →4N ₂ +6H ₂ O; or

4NO+2( _NH2 ) _2CO + _O2 → _4N2 +4H2O _{+ 2CO2} .

The principle of dioxin removal is:

_{C12HnCl8 -} nO2+(9+0.5n) _O2 →(n-4) _{H2O +} 12CO2 ₊ (8-n)HCl.

In some embodiments, the bicarbonate salt is sodium bicarbonate or slaked lime.

In some embodiments, the mass of bicarbonate added to the flue gas per cubic meter is adjusted with different components of the flue gas, so as to ensure the complete removal of sulfur dioxide in the flue gas as much as possible.

In some embodiments, the reducing agent is ammonia or urea, and the catalyst in the catalyst layer is a vanadium-titanium-tungsten-based catalyst or a vanadium-titanium-based catalyst.

Further, the quality of the reducing agent added in each cubic meter of flue gas is adjusted according to the different components of the flue gas.

In some embodiments, the outer diameter of the basalt fiber filter cartridge is 150mm-152mm, the inner diameter is 104mm-110mm, the outer diameter of the flange surface is 190mm-196mm, the height of the flange surface is 30mm±2mm, the length is 2.95m-3m, and the weight is 12.5±12.5mm. 1Kg; filtration area ≥1.4m ² , density 0.4g/dm ³ ; basalt fiber diameter 2-3mm.

In some embodiments, the preparation method of the basalt fiber filter cartridge is:

The basalt fiber is chopped and ball milled until the length-diameter ratio of the fiber is 30-100;

Mix the basalt fiber with the inorganic binder to prepare a uniform slurry;

The material will be injected into the mold for suction filtration molding, after drying, and after loading the catalyst, the basalt fiber filter cartridge is obtained.

Further, the inorganic binder is silica sol or aluminum dihydrogen phosphate. These two inorganic binders do not cause catalyst poisoning.

In some embodiments, each basalt fiber filter cartridge is provided with a backflushing nozzle, and the backflushing nozzle is connected to a source of compressed air.

The compressed air source provides compressed air for the blowback nozzle, and the compressed air is used to blow back the basalt fiber filter cartridge deposited with a dust layer, and the filtered dust can be blown off to improve the filtering effect of the flue gas and ensure the smoothness of the flue gas. circulation.

Further, the backflushing nozzles are arranged along the axial direction of the basalt fiber filter cartridge, and several groups of nozzles are arranged along the axial direction of the backflushing nozzles.

Multiple groups of nozzles are set up to backflush and clean various positions of the basalt fiber filter cartridge, and the dust layer deposited on the basalt fiber filter cartridge can be backflushed clean.

Further, the pressure of the backflushing air is 0.5-0.7MPa, and the backflushing air is pulsated and injected.

In some embodiments, the bottom of the casing is an inverted conical structure, and an ash discharge port is disposed at the bottom.

The dust blown off by the back blow falls into the inverted cone structure and is discharged smoothly through the ash discharge port.

In some embodiments, a baffle is provided at the rear of the boiler, and the economizer and the air preheater are disposed downstream of the baffle.

Further, the clean flue gas discharged from the second chamber of the casing is re-transported to the downstream of the partition plate, and discharged from the chimney after passing through the economizer and the air preheater.

Since the temperature of the flue gas after desulfurization and denitrification is still high, waste heat recovery through the economizer and air preheater can effectively prevent heat waste. The clean flue gas is sent back to the economizer, and the waste heat at the tail is recovered without ash accumulation and corrosion on the heating surface, which completely improves the working conditions of the heating surface and improves the heat exchange effect. The increase in the power consumption of the induced draft fan caused by the increase of the ash blocking resistance is greatly reduced, and the number of times the boiler is shut down to clear the ash is greatly reduced.

The beneficial effects of the present invention are:

1. The biomass boiler flue gas is combined with dry desulfurization and high temperature through the catalyst basalt fiber filter cartridge, the NO _X reduction rate reaches more than 95%, and the desulfurization efficiency is improved; emission parameters: dust ≤ 10mg/m ³ , the minimum can reach 5mg/m ³ ; NOx≤50mg/m ³ ; SO ₂ <35mg/m ³ , dust removal, desulfurization, denitrification, and dioxin removal, to achieve ultra-clean emission of flue gas.

2. Solve the problem of poisoning failure of flue gas SCR denitration catalyst, which is inert to almost all chemicals and can prevent chemical poisoning; it makes it possible that the flue gas of biomass boilers, garbage boilers, and other industrial kilns cannot achieve SCR conventional denitration. .

3. The catalyst is evenly distributed on the filter cartridge. The catalyst and denitrification agent (ammonia or urea solution) have a large contact reaction area and a long reaction time with the flue gas, so that the ammonia escapes less and the denitration efficiency is greatly improved.

4. The basalt fiber filter cartridge has the advantages of high temperature resistance, corrosion resistance, long service life, low resistance loss, and high dust removal efficiency; based on the mechanism of surface filtration, it can handle dust-containing gas with strong adhesion and is not easy to cause blockage.

5. Basalt fiber filter cartridge is combined with dry desulfurization (sodium bicarbonate or calcium hydroxide), since the desulfurization agent can form a filter cake layer on the surface of the filter cartridge, which improves the desulfurization efficiency;

6. After the flue gas at 250-350°C is dedusted, desulfurized and denitrified, the waste heat recovery at the rear of the heating surface does not accumulate dust or corrosion, which completely improves the working conditions of the heating surface and improves the heat exchange effect.

7. The boiler increases the low-temperature heating surface, the exhaust gas temperature can be reduced by 50-70 degrees, and the thermal efficiency of the boiler is increased by 3-5%.

8. The heating surface of the boiler tail after the high temperature composite filter cartridge is free of ash and corrosion, which greatly reduces the increase in the power consumption of the induced draft fan caused by the increase of the ash blocking resistance, and the number of times the boiler is shut down to clear the ash is greatly reduced.

9. Basalt fiber filter cartridge can also remove dioxin in flue gas.

10. Basalt fiber filter cartridge is combined with dry desulfurization (sodium bicarbonate or calcium hydroxide), and no water participates in the reaction, which avoids the plume produced by wet desulfurization.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

1 is a schematic structural diagram of a denitration composite dust removal device according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a basalt fiber filter cartridge for filtering exhaust gas according to an embodiment of the present invention.

In the figure: 1- flue gas outlet, 2- shell, 3- main pipe, 4- partition plate, 5- pipe body wall, 6- backflushing nozzle, 7- flue gas inlet.

Detailed ways

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

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

Example 1

This embodiment is implemented in a biomass power generation boiler, the main raw material is biomass, and the exhaust gas mainly contains soot, sulfur oxides, nitrogen oxides, and the like. According to the biomass test report, it can be known that the biomass used in this example has a sulfur content of 0.32% and an ash content of 7.11%. According to the calculation: the amount of SO ₂ produced is 458.88t/a (129.6kg/h), and the production concentration is 466.4mg/m ³ ; in order to meet the standard limit requirements of the "Boiler Air Pollutant Emission Standard", the alkali consumption for desulfurization is 287t/a, The amount of lime is 202t/a. According to the biomass test report, the nitrogen content of the biomass used in this project is 0.22%. According to the calculation, the amount of NO _X produced was 281.06 t/a (79.4 kg/h), and the produced concentration was 285.7 mg/m ³ . In order to meet the standard limit requirements of the "Boiler Air Pollutant Emission Standard", the present embodiment needs to reduce the amount of nitrogen oxides in the flue gas by more than 90%, and control NOx≤50mg/Nm ³ .

Directly transform the boiler economizer to lead out the heated flue gas from the economizer, and the flue gas temperature is 350℃.

The schematic diagram of the structure of the denitration composite dust removal device is shown in Figure 1, including a shell 2, a partition plate 4 and a number of basalt fiber filter cartridges. A chamber and a second chamber, the side wall of the housing 2 of the first chamber is provided with a smoke inlet 7, and the side wall of the housing of the second chamber is provided with a smoke outlet 1;

Each basalt fiber filter cartridge is a hollow tube body, and the tube body wall is a filter cartridge structure bonded by basalt fiber wool. The basalt fiber wool is bonded with a catalyst, one end of which is sealed and the other end is open;

Each basalt fiber filter cartridge is installed on the partition plate 4, and is located in the first chamber as a whole, and the opening of each basalt fiber filter cartridge is communicated with the second chamber;

The outer diameter of the basalt fiber filter cartridge is 150mm-152mm, the inner diameter is 104mm-110mm, the outer diameter of the flange surface is 190mm-196mm, the height of the flange surface is 30mm±2mm, the length is 2.95m-3m, and the weight is 12.5±1Kg; the filter area is ≥1.4 m ² , density 0.4g/dm ³ ; basalt fiber diameter 2-3mm.

Each basalt fiber filter cartridge is provided with a blowback nozzle 6 , and the blowback nozzle 6 is connected to the compressed air source through the main pipe 3 .

The preparation process of the basalt fiber filter cartridge is as follows:

(1) Basalt fiber cotton treatment: firstly chop the basalt fiber, then ball mill it in a ball mill for a certain time, and control the length-diameter ratio of the fiber to be between 30 and 100 by time. In order to better improve the connection between fibers and binders and catalysts, a certain amount of surface modifier is generally added.

(2) Selection of inorganic binder: Considering that the sodium ions in water glass may poison the catalyst and reduce the effect of the catalyst, use an alkali-free inorganic binder such as silica sol or aluminum dihydrogen phosphate for bonding. According to relevant theoretical research and practical experiments, the content of binders such as silica sol is generally not higher than 1%.

(3) Mix the ground basalt short fibers and the inorganic binder under high-speed stirring to prepare a uniform slurry. After the slurry is uniformly dispersed, inject it into the mold for rapid suction filtration to remove water, and then filter to form The wet blank is demolded and dried, and treated at low temperature to obtain a basalt short fiber composite filter cartridge.

(4) Compounding of vanadium-titanium catalyst: The process of basalt fiber tube containing vanadium-titanium catalyst is basically the same as that of ordinary basalt fiber tube, except that in the wet process, after evenly adding vanadium-titanium catalyst, high-speed stirring is sufficient, and the The content is related to the process.

The inlet and outlet of the flue gas system are equipped with an online continuous detection system for flue gas, and the inlet and outlet are respectively monitored: SO ₂ , O ₂ , temperature, pressure, flow, and dust. The desulfurization reactor is designed with a high-efficiency sodium-based dry powder injection and uniform distribution device. The flue gas discharged from the boiler is tempered by the hot flue gas with a flue gas temperature of 320 °C and a flue gas flow of 413,000 m ³ /h. Add dry sodium bicarbonate (NaHCO ₃ , baking soda) ultrafine particles (grind to 20-30μm, 600-700 mesh) powder, the ultrafine powder baking soda particles have a huge specific surface area, in a reasonable flue gas temperature , which is rapidly decomposed into fresh sodium carbonate when heated. The newly decomposed sodium carbonate has high surface activity and strong ability to react with acidic substances. It quickly reacts with acidic substances in flue gas such as SO ₂ and SO ₃ . , HF, HCl and other reactions. For example, it reacts with SOx in the flue gas to generate sodium sulfite and sodium sulfate. The control system controls the emission value of flue gas desulfurization by adjusting the amount of desulfurizer (sodium bicarbonate) added.

As shown in Figure 2, after adding ammonia gas to the flue gas after desulfurization, the flue gas flows into the denitration composite dust removal device, flows in from the flue gas inlet, passes through the catalyst layer 6 after being filtered through the pipe wall 5, and is in the catalyst layer 6 is catalytically reacted to remove nitrogen oxides and dioxins in the flue gas. It then flows into the second chamber and flows out through the flue gas outlet 1 .

After running for a period of time, the compressed air source provides pulsed backflushing air flow to backflush the basalt fiber filter cartridge, and the pressure of the compressed air is 0.7MPa.

The flue gas after desulfurization and denitrification meets the standard.

Example 2

The inlet and outlet of the flue gas system are equipped with an online continuous detection system for flue gas, and the inlet and outlet are respectively monitored: SO ₂ , O ₂ , temperature, pressure, flow, and dust. The desulfurization reactor is designed with a high-efficiency sodium-based dry powder injection and uniform distribution device. The flue gas discharged from the boiler is tempered by the hot flue gas, and the flue gas temperature is ₃₀₀ ° C. Soda) ultrafine particles (600-650 mesh) powder, the ultrafine powder of baking soda particles has a huge specific surface area, at a reasonable flue gas temperature, it is quickly decomposed into fresh sodium carbonate when heated, and the newly decomposed sodium carbonate , the surface activity is very high, and it has a strong ability to react with acidic substances, and it quickly reacts with acidic substances in flue gas such as SO ₂ , SO ₃ , HF, HCl, etc. For example, it reacts with SOx in the flue gas to generate sodium sulfite and sodium sulfate. The control system controls the emission value of flue gas desulfurization by adjusting the amount of desulfurizer (sodium bicarbonate) added.

After adding urea to the flue gas after desulfurization, the flue gas flows into the denitration composite dust removal device, flows from the flue gas inlet, passes through the catalyst layer 6 after being filtered by the pipe wall 5, and is catalyzed and reacted in the catalyst layer 6 to remove the smoke. Nitrogen oxides and dioxins in the air. It then flows into the second chamber and flows out through the flue gas outlet 1 .

After running for a period of time, the compressed air source provides pulsed backflushing air flow to backflush the basalt fiber filter cartridge, and the pressure of the compressed air is 0.7MPa. The treated flue gas meets the standard.

The treated flue gas returns to the tail of the boiler, and flows through the economizer and air preheater for waste heat recovery and then discharged through the chimney.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (6)

1. a method for dedusting, desulfurizing, denitrifying and removing dioxin from boiler flue gas, it is characterized in that: comprise the steps: The flue gas with a temperature of 250-350 ℃ is drawn from the boiler, and 600-700 mesh bicarbonate is sprayed into the flue gas to react; After adding a reducing agent to the reacted flue gas, it enters the denitration composite dust removal device for denitration, dioxin removal and dust removal; The denitration composite dust removal device includes a shell, a partition plate and several basalt fiber filter cartridges. The partition plate is arranged on the cross section of the shell to separate the shell into a first chamber and a second chamber. A fume inlet is provided on the side wall of the housing of the chamber, and a fume outlet is provided on the side wall of the housing of the second chamber; Each basalt fiber filter cartridge is a hollow tube body, and the tube body wall is a filter cartridge structure bonded by basalt fiber wool. The basalt fiber wool is bonded with a catalyst, one end of which is sealed and the other end is open; Each basalt fiber filter cartridge is installed on the partition plate, and is located in the first chamber as a whole, and the opening of each basalt fiber filter cartridge is communicated with the second chamber; The flue gas after adding the reducing agent enters from the flue gas inlet, flows into the second chamber after filtering and catalytic reaction, and flows out through the flue gas outlet; Described bicarbonate is sodium bicarbonate; The reducing agent is ammonia or urea, and the catalyst is a vanadium-titanium-tungsten-based catalyst or a vanadium-titanium-based catalyst; A baffle is arranged at the tail of the boiler, and the economizer and air preheater are arranged downstream of the baffle, and the clean flue gas discharged from the second chamber of the shell is re-transported to the downstream of the baffle, and flows through the baffle. The economizer and air preheater are discharged from the chimney. 2 . The method according to claim 1 , wherein the outer diameter of the basalt fiber filter cartridge is 150mm-152mm, the inner diameter is 104mm-110mm, the filter area is ≥1.4m ² , and the diameter of the basalt fiber is 2-3mm. 3 . 3. method according to claim 1, is characterized in that: the preparation method of described basalt fiber filter cartridge is: The basalt fiber is chopped and ball milled until the length-diameter ratio of the fiber is 30-100; Mix basalt fiber with inorganic binder to prepare uniform slurry; The slurry is injected into the mold for suction filtration molding, and after drying, the catalyst is loaded to obtain a basalt fiber filter cartridge. 4. The method according to claim 3, wherein the inorganic binder is silica sol or aluminum dihydrogen phosphate. 5. The method according to claim 1, characterized in that: each basalt fiber filter cartridge is provided with a backflushing nozzle, and the backflushing nozzle is connected with a compressed air source; Further, the backflushing nozzle is arranged along the axial direction of the basalt fiber filter cartridge, and several groups of nozzles are arranged along the axial direction of the backflushing nozzle; The pressure of the backflushing air is 0.5-0.7MPa, and the backflushing air is pulsating and spraying. 6 . The method according to claim 5 , wherein the bottom of the casing is an inverted conical structure, and an ash discharge port is arranged at the bottom. 7 .

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