CN114260297A

CN114260297A - Device and method suitable for fly ash melting and flue gas purification treatment

Info

Publication number: CN114260297A
Application number: CN202210195167.2A
Authority: CN
Inventors: 陈德喜; 李兴杰; 高术杰; 姚建明; 胡立琼; 刘补元; 仇云飞
Original assignee: China ENFI Engineering Corp
Current assignee: China ENFI Engineering Corp
Priority date: 2022-03-02
Filing date: 2022-03-02
Publication date: 2022-04-01
Anticipated expiration: 2042-03-02
Also published as: CN114260297B

Abstract

The invention provides a device and a method suitable for fly ash melting and flue gas purification treatment. The device comprises a double-chamber melting furnace and a flue gas purification device; the inner cavity of the double-chamber melting furnace is divided into a main reaction chamber and an auxiliary reaction chamber which are horizontally communicated in sequence, the top of the main reaction chamber is provided with a main feed inlet near a partition wall, the top of the main reaction chamber is also provided with a first flue gas outlet, and the side part of the main reaction chamber is provided with a salt fishing port; an auxiliary charging opening is formed in the top of the auxiliary reaction chamber, close to the partition wall, and a second flue gas outlet and an electrode opening are formed in the top of the auxiliary reaction chamber; the flue gas purification device comprises a water seal box, an alkali liquor pool, a flue gas cooling unit and a multistage flue gas spraying and washing unit. The device provided by the invention is used for melting the fly ash and purifying the flue gas, so that two products, namely glass slag and molten salt, can be obtained to the maximum extent, and the problems of easy corrosion of a furnace body, unstable operation in the melting process and environment pollution caused by easy volatilization of chlorine salt, which are caused by chlorine salt, are effectively solved.

Description

Device and method suitable for fly ash melting and flue gas purification treatment

Technical Field

The invention relates to the technical field of fly ash treatment, in particular to a device and a method suitable for fly ash melting and flue gas purification treatment.

Background

The fly ash refers to domestic garbage (mineral phase main component comprises Ca (OH)₂、CaClOH、CaSO₄KCl, NaCl, organic C and a certain amount of H₂O, etc.) and other waste such as medical waste, etc. collected by the incinerated flue gas system. The fly ash integrates all pollutants of waste incineration into a whole, and the treatment of the fly ash is the last kilometer of the waste incineration technology for thoroughly solving the pollution problem. The fly ash accounts for about 2.5-3% of the total amount of the household garbage, and the content of toxic substances including heavy metals, dioxin, furan, chlorides and salts of different types and the like is very high, and the fly ash is also defined as dangerous solid waste. Due to the low density and large volume of the fly ash, the landfill treatment using traditional chelating agents plus cement takes up a large amount of land, and dioxin is present in the mixture, and the landfill product still has potential risks. With the continuous expansion of the incineration scale of municipal solid waste, the annual production amount of fly ash generated by incinerating the municipal solid waste is increased from 400 ten thousand tons in 2015 to 800 ten thousand tons in 2020, however, due to the huge gap of the disposal capacity of the fly ash, the harmless treatment of the fly ash is urgent and the healthy development of the incineration power generation industry of the municipal solid waste is also severely restricted.

At present, fly ash treatment mainly comprises fly ash pretreatment, electric furnace melting and flue gas purification, wherein a fly ash pretreatment system adopts dry-method pair roller granulation equipment to mix fly ash and quartz powder and send the mixture into an electric furnace for melting treatment; melting the mixed materials by using electrode arc heat and material resistance heat to respectively obtain glass slagAnd a molten salt product, so that the solidification of the heavy metals which are difficult to volatilize and the complete decomposition of dioxin organic matters are realized; aiming at complex high-temperature flue gas, volatile heavy metals (mainly existing in a secondary fly ash form) are enriched, and the sodium-alkali method is used for absorbing acid gas to realize clean emission of the flue gas. The primary equipment for treating fly ash is usually a plasma furnace or other form of electric melting furnace. Under the condition of high-temperature melting at 1300-1500 ℃, the organic matters in the fly ash are subjected to thermal decomposition, combustion and gasification, and SiO in the inorganic matters₂After the melting treatment, a Si-O network structure is formed, and heavy metals in the fly ash are encapsulated in the network structure to form a rigid amorphous substance. After the melting treatment, the organics such as dioxin in the fly ash are thoroughly decomposed and destroyed, the heavy metal salts with lower boiling point are transferred to the flue gas and captured in the form of secondary fly ash, and the residual heavy metal is transferred to the vitreous slag, so that the leaching rate of the heavy metal is greatly reduced. The results of toxic leaching characteristic experiments (TCLP) show that the leaching rates of heavy metals are very low, which indicates that part of Ca in the heavy metal-substituted silicate minerals²⁺、Al³⁺But is encapsulated in the network lattice of the silicate. After the fly ash is melted and solidified, the density is greatly increased, the volume reduction of the fly ash can reach more than 2/3, and the obtained slag can be used as a primary product (filling materials, roadbed materials, concrete, aggregate and the like), a secondary product (a concrete color flat plate, a permeable brick, a concrete pipe and the like) and a product with high added value (microcrystalline glass, a sintered brick, a water retention ceramic brick, glass fiber and the like).

However, in the plasma furnace and other melting electric furnaces, although the treatment effect on heavy metals, dioxin and the like in the fly ash is significant, the large-scale application of the furnace is still difficult to popularize, because the following reasons are as follows:

the fly ash has high salt content such as sodium chloride, potassium chloride, calcium chloride, etc., especially high chlorine content up to 20% in high chlorine fly ash, and chloride (NaCl, KCl, CaCl)₂) The content is often 35% or more. On one hand, the high chlorine fly ash is easy to cause the erosion of furnace body refractory materials in the melting treatment process, the service life of the furnace body is shortened, the system is bonded, and the electrode short circuit is easy to cause by overhigh salt content, thereby leading the fly ash to be melted stablyConstant operation presents difficulties. On the other hand, the chlorine salt can volatilize into the smoke in the melting process, and great pollution is brought to the environment. Therefore, the removal of chloride from fly ash is an important factor that restricts the melting treatment of fly ash.

In the prior art, a process of desalting and remelting fly ash by water washing pretreatment is adopted, namely, the fly ash is washed by water, and then melting treatment is carried out after chlorine salt in the fly ash is removed. However, the total fly ash washing cost is too high, and some heavy metal pollutants which should be melted and solidified are inevitably introduced into the sewage system, so that the sewage treatment cost is increased. Therefore, this method is not feasible.

Based on the above reasons, further research on the treatment mode of the fly ash is necessary to better solve the problems of easy corrosion of the furnace body, unstable operation of the melting process and environmental pollution caused by the volatile chlorine salt in the fly ash melting treatment process.

Disclosure of Invention

The invention mainly aims to provide a device and a method suitable for fly ash melting and flue gas purification treatment, so as to solve the problems of easy corrosion of a furnace body, unstable operation in a melting process and environment pollution caused by volatile chlorine salt in fly ash in a fly ash melting treatment process in the prior art.

In order to achieve the above object, according to one aspect of the present invention, there is provided an apparatus for fly ash melting and flue gas cleaning, comprising:

the double-chamber melting furnace is characterized in that the inner cavity of the double-chamber melting furnace is divided into a main reaction chamber and an auxiliary reaction chamber which are horizontally communicated in sequence, a partition wall is arranged between the main reaction chamber and the auxiliary reaction chamber, and a communication channel for communicating the main reaction chamber and the auxiliary reaction chamber is arranged at the bottom of the partition wall; a main feeding port is arranged at the top of the main reaction chamber close to the partition wall, a first flue gas outlet is also arranged at the top of the main reaction chamber, and a salt fishing port is arranged at the side part of the main reaction chamber; an auxiliary charging opening is formed in the top of the auxiliary reaction chamber, close to the partition wall, a second flue gas outlet and an electrode opening are further formed in the top of the auxiliary reaction chamber, the double-chamber melting furnace further comprises a heating electrode, and the heating electrode penetrates through the electrode opening and extends into the auxiliary reaction chamber;

the flue gas purification device comprises a water seal tank, an alkaline solution pool, a flue gas cooling unit and a multi-stage flue gas spraying and washing unit, wherein the flue gas cooling unit and the flue gas spraying and washing unit are arranged at the top of the water seal tank; the lateral part of the water seal tank is provided with an overflow port, and the bottom of the water seal tank is provided with a sludge discharge port; the flue gas cooling unit is provided with a flue gas cooling cavity, the top of the flue gas cooling cavity is provided with a cooling spraying unit, the flue gas cooling cavity is also provided with a flue gas inlet and a cooling flue gas outlet, the flue gas inlet is communicated with the first flue gas outlet and the second flue gas outlet, the top of the water seal box is provided with a cooling water inlet, and the cooling water inlet is communicated with the bottom of the flue gas cooling cavity; according to the flow direction of the flue gas, the flue gas spraying and washing units at all levels are sequentially communicated and arranged at the downstream of the cooling flue gas outlet, each flue gas spraying and washing unit is provided with a flue gas spraying and washing cavity, the top of the flue gas spraying and washing cavity is provided with a washing and spraying unit, the top of the water seal box is also provided with a washing water inlet, and the washing water inlet is communicated with the bottom of the flue gas spraying and washing cavity; the alkali liquor pool is connected with both the cooling spraying unit and the washing spraying unit and is used for supplying alkali liquor.

Furthermore, the position of the side wall of the main reaction chamber, which is lower than the salt fishing port, is also provided with a heat supplementing port, and the device also comprises a heat supplementing unit which supplements heat to the main reaction chamber through the heat supplementing port.

Further, the heat supplementing unit is a heat supplementing electrode or a fuel spray gun.

Furthermore, in the double-chamber melting furnace, the volume ratio of the main reaction chamber to the secondary reaction chamber is 1.

Further, the salt fishing port is positioned on the side wall of the main reaction chamber at a position higher than the bottom of the partition wall; the partition wall and the bottom wall inside the double-chamber melting furnace are provided with a space to form a communication channel.

Further, the distance between the bottom of the partition wall and the bottom wall of the interior of the double-chamber melting furnace is denoted as h₁The total height of the partition being denoted h₂Then 1/3 < h₁/ h₂＜1。

Further, the partition wall is a water-cooling partition wall or an air-cooling partition wall.

Further, the lower end of the heating electrode is located at a position lower than the bottom of the partition wall.

Furthermore, the device also comprises a vertical combustion chamber, wherein the vertical combustion chamber is respectively communicated with the first smoke outlet, the second smoke outlet and the smoke inlet, and the vertical combustion chamber is used for carrying out combustion treatment on the smoke discharged from the first smoke outlet and the second smoke outlet.

Further, the vertical combustion chamber is arranged above the second flue gas outlet and is vertically connected with the second flue gas outlet; and the top of the vertical combustion chamber is also provided with an ash removal unit which is used for carrying out ash removal treatment on the inner wall of the vertical combustion chamber.

Further, the device still includes batching unit, and batching unit is used for batching fly ash and flux, and batching unit links to each other with main charge door through first feeder hopper, and batching unit passes through the second feeder hopper and links to each other with vice charge door.

Furthermore, the device also comprises a salt fishing device which carries out salt fishing through the salt fishing port.

Furthermore, the flue gas cooling unit also comprises a cooling flue gas discharge pipeline, one end of the cooling flue gas discharge pipeline is connected with the cooling flue gas outlet, and the other end of the cooling flue gas discharge pipeline is connected with the top of the water seal tank; wherein, the cooling flue gas discharge pipeline is a Venturi tube; or a first induced draft device is arranged on the cooling flue gas discharge pipeline.

Furthermore, the cooling flue gas discharge pipelines are a plurality of pipelines which are arranged in parallel.

Furthermore, in the multi-stage flue gas spraying and washing units which are sequentially communicated, the flue gas spraying and washing units except the final stage also comprise a spraying flue gas discharge pipeline, one end of the spraying flue gas discharge pipeline is connected with the flue gas spraying and washing cavity, and the other end of the spraying flue gas discharge pipeline is connected with the top of the water seal tank; wherein, the spraying flue gas discharge pipeline is a Venturi tube; or a second induced draft device is arranged on the spraying smoke discharge pipeline.

Furthermore, the spraying flue gas discharge pipelines in each flue gas spraying and washing unit are a plurality of pipelines which are arranged in parallel.

Furthermore, the last stage flue gas sprays the washing unit and still includes the exhaust of purification flue gas pipeline, and the exhaust of purification flue gas pipeline sprays the washing chamber with the flue gas that the last stage flue gas sprayed the washing unit and links to each other.

Further, the overflow mouth sets up the position that is close to inside roof of water seal tank lateral part.

Furthermore, a sludge collecting unit is arranged at the bottom in the water seal tank and used for collecting sludge deposited in the water seal tank and discharging the sludge through a sludge discharging port.

Furthermore, the mud collecting unit is an inclined scraper which inclines downwards from a direction far away from the mud discharging port to a direction close to the mud discharging port; or the mud collecting unit is a screw conveyor.

Furthermore, the device also comprises a dewatering device which is communicated with the sludge discharge port.

Furthermore, the dehydration equipment is provided with a liquid phase outlet and a solid phase outlet, and the liquid phase outlet is communicated with the alkali liquor pool.

Furthermore, a slag discharge port is also arranged on one side of the secondary reaction chamber, which is far away from the main reaction chamber; the slag discharge port comprises a bottom slag port positioned at the lower part of the side wall of the secondary reaction chamber and an upper slag port positioned above the bottom slag port.

According to another aspect of the present invention, there is also provided a method for melting and flue gas cleaning fly ash, which uses the above apparatus to perform melting and flue gas cleaning treatment on fly ash, the method comprising the following steps: step S1, mixing the fly ash and optional flux to form fly ash to be treated; firstly, feeding materials into the double-chamber melting furnace through a main feed inlet and/or an auxiliary feed inlet, and starting a heating electrode to melt fly ash to be treated and form a molten pool; step S2, after the molten pool is formed, continuously feeding the fly ash to be treated into the molten pool of the main reaction chamber through the main feed inlet so as to melt the fly ash; in the process of melting treatment, a molten pool in the secondary reaction chamber is heated through a heating electrode, the temperature of the molten pool in the secondary reaction chamber is controlled to be 1200-1400 ℃, and the temperature of a hearth above the molten pool in the secondary reaction chamber is controlled to be 700-1200 ℃; carrying out heat conduction heating on a molten pool in the main reaction chamber through a molten pool in the auxiliary reaction chamber, and controlling the temperature of the molten pool in the main reaction chamber to be 900-1200 ℃ and the temperature of a hearth above the molten pool in the main reaction chamber to be 200-500 ℃; along with the progress of the melting treatment, a molten salt layer is formed on the surface of a molten pool of the main reaction chamber, slag is formed at the bottom of the double-chamber melting furnace, the flue gas generated in the main reaction chamber is discharged from a first flue gas outlet, and the flue gas generated in the secondary reaction chamber is discharged from a second flue gas outlet; fishing out the molten salt in the molten salt layer through a salt fishing port; step S3, the flue gas discharged from the first flue gas outlet and the second flue gas outlet is used as the flue gas to be purified and is sent into a flue gas purification device through a flue gas inlet for flue gas purification treatment; firstly, introducing flue gas to be purified into a flue gas cooling cavity, and supplying alkali liquor to a cooling spraying unit by using an alkali liquor pool so as to cool the flue gas to be purified to form cooled flue gas and first spraying liquor; cooling flue gas sequentially passes through flue gas spraying washing cavities of the multi-stage flue gas spraying washing units, and alkali liquor is supplied to each washing spraying unit by using an alkali liquor pool, so that the cooling flue gas is sequentially subjected to multi-stage spraying washing to form purified flue gas and second spraying liquor; enabling the first spraying liquid and the second spraying liquid to enter a water seal tank for sludge precipitation to obtain overflow liquid and sludge; the overflow liquid is discharged through the overflow port, and the sludge is discharged through the sludge discharge port.

Further, during the melting treatment in step S2, when the temperature of the molten pool in the main reaction chamber is lowered, the fly ash to be treated is replenished from the replenishing port through the replenishing unit and/or the molten pool in the auxiliary reaction chamber through the auxiliary charging port.

Further, the process of performing heat compensation by the heat compensation unit includes: supplementing heat to the main reaction chamber molten pool through a heat supplementing electrode, or injecting fuel into the main reaction chamber molten pool for supplementing heat; preferably, the fuel is natural gas and/or fuel oil.

Further, in the melting process of step S2, the furnace pressure above the main reaction chamber molten pool is controlled to be-100 Pa to 0Pa, and the furnace pressure above the auxiliary reaction chamber molten pool is controlled to be-100 Pa to 0 Pa.

Further, before the step of sending the flue gas to be purified into the flue gas purification device for flue gas purification treatment, step S3 further includes: and (4) carrying out combustion treatment on the flue gas to be purified through a vertical combustion chamber.

Further, the vertical combustion chamber is arranged above the second flue gas outlet and is vertically connected with the second flue gas outlet; the method further comprises the following steps: and the ash removal unit at the top of the vertical combustion chamber is used for carrying out ash removal treatment on the inner wall of the vertical combustion chamber.

Further, in step S3, after the flue gas to be purified is introduced into the flue gas cooling chamber for cooling treatment, the cooled flue gas is sent to the top of the water-sealed tank by using the cooled flue gas discharge pipeline, and then enters the flue gas spray washing unit; when the cooling flue gas discharge pipeline is a Venturi tube, the cooling flue gas enters the flue gas spraying and washing unit through the top of the water seal box by self-suction force; when the cooling flue gas discharge pipeline is provided with the first air inducing device, the cooling flue gas passes through the top of the water seal box and enters the flue gas spraying and washing unit under the air inducing effect of the first air inducing device.

Further, in step S3, in the process of performing multi-stage spraying washing by passing the cooling flue gas through the flue gas spraying washing cavities of the multi-stage flue gas spraying washing units in sequence, the spraying flue gas formed by spraying the flue gas in the previous stage into the washing cavity is sent to the top of the water seal box by using the spraying flue gas exhaust pipeline, and then enters the flue gas spraying washing cavity in the next stage; when the spraying flue gas discharge pipeline is a Venturi tube, spraying flue gas formed by the front stage flue gas spraying washing cavity passes through the top of the water seal box by self-suction force and enters the rear stage flue gas spraying washing cavity; when the second induced draft device is arranged on the spraying flue gas discharge pipeline, the spraying flue gas formed by spraying the washing cavity by the flue gas of the previous stage passes through the top of the water seal box and enters the flue gas spraying washing cavity of the next stage under the induced draft action of the second induced draft device.

Further, the method further comprises: dehydrating the sludge by dehydration equipment to form a liquid phase and a solid phase; returning the solid phase to step S1 for compounding; the liquid phase is returned to the caustic bath.

The device provided by the invention is used for melting the fly ash and purifying the flue gas, most of salt in the fly ash can be separated out through a salt fishing port of the main reaction chamber in the process of melting the fly ash by a double-chamber melting furnace technology, the corrosion of the fly ash after the salt is extracted to refractory materials is delayed in the melting process, the service life of the refractory materials of the electric furnace is prolonged, the system is prevented from being bonded, and the stable operation in the operation process is ensured. Heavy metal pollutants in the fly ash are solidified in the molten slag during the melting process to form harmless products. Meanwhile, a small part of residual salt can be used as an important conductive medium to play a conductive role in the electrode heating process, so that the electrode heating efficiency is improved. The small amount of salt can be volatilized and enter a subsequent flue gas purification device to be quenched along with the flue gas, and then is removed through multi-stage spraying, washing and separating.

In a word, the device provided by the invention can be used for melting the fly ash and purifying the flue gas, so that two products, namely glass slag and molten salt, can be obtained to the maximum extent, and the two products account for more than 90% of solid products. Through the separation of the fused salt in the melting process, the invention effectively solves the problems of easy corrosion of the furnace body, unstable operation in the melting process and easy volatilization of the chlorine salt to pollute the environment caused by the chlorine salt by using a simple fly ash melting and flue gas purification treatment device, does not need to wash the whole fly ash to cause a great amount of waste of water resources, equipment resources and the like, reduces the system investment for treating the fly ash, has low cost and stable operation, and is very suitable for industrial large-scale application.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 shows a schematic structural diagram of an apparatus suitable for fly ash melting and flue gas cleaning treatment according to an embodiment of the present invention.

Wherein the figures include the following reference numerals:

10. a dual chamber melting furnace; 11. a main reaction chamber; 12. a secondary reaction chamber; 13. a partition wall; 14. heating the electrode; 15. a vertical combustion chamber; 16. an ash removal unit; 17. a first feed hopper; 18. a second feed hopper; 101. a main feed inlet; 102. a first flue gas outlet; 103. fishing out a salt mouth; 104. an auxiliary feed inlet; 105. a second flue gas outlet; 106. an electrode port; 107. a heat supplementing port; 108. a bottom slag hole; 109. a slag feeding port;

20. a flue gas purification device; 21. water sealing the tank; 22. an alkaline solution pool; 23. a flue gas cooling unit; 24. a flue gas spraying and washing unit; 25. a dewatering device; 201. an overflow port; 202. a sludge discharge port; 203. a flue gas inlet; 204. a cooling flue gas outlet; 211. a mud collecting unit; 231. a flue gas cooling chamber; 232. a cooling flue gas discharge line; 241. flue gas spraying washing cavity; 242. spraying a flue gas discharge pipeline; 243. a purified flue gas discharge pipeline.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As described in the background art, in the process of melting fly ash in the prior art, the content of chlorine salt in fly ash is high, which easily causes the problems that the refractory material in the furnace body is easy to corrode, the furnace body is unstable to operate in the melting process, and the chlorine salt is easy to volatilize and pollutes the environment. In order to solve the above problems, the present invention provides an apparatus suitable for fly ash melting and flue gas purification treatment, as shown in fig. 1, the apparatus comprises a double-chamber melting furnace 10 and a flue gas purification apparatus 20; wherein,

the inner cavity of the double-chamber melting furnace 10 is divided into a main reaction chamber 11 and an auxiliary reaction chamber 12 which are horizontally communicated in sequence, a partition wall 13 is arranged between the main reaction chamber 11 and the auxiliary reaction chamber 12, and the bottom of the partition wall 13 is provided with a communication channel for communicating the main reaction chamber 11 and the auxiliary reaction chamber 12; a main feeding port 101 is arranged at the top of the main reaction chamber 11 close to the partition wall 13, a first flue gas outlet 102 is also arranged at the top of the main reaction chamber 11, and a salt fishing port 103 is arranged at the side part; an auxiliary feeding port 104 is arranged at the top of the auxiliary reaction chamber 12 close to the partition wall 13, a second flue gas outlet 105 and an electrode port 106 are also arranged at the top of the auxiliary reaction chamber 12, the double-chamber melting furnace 10 further comprises a heating electrode 14, and the heating electrode 14 penetrates through the electrode port 106 and extends into the auxiliary reaction chamber 12;

the flue gas purification device 20 comprises a water seal tank 21, an alkali liquor pool 22, a flue gas cooling unit 23 and a multi-stage flue gas spraying and washing unit 24, wherein the flue gas cooling unit 23 and the flue gas spraying and washing unit 24 are both arranged at the top of the water seal tank 21; the lateral part of the water seal tank 21 is provided with an overflow port 201, and the bottom part is provided with a sludge discharge port 202; the flue gas cooling unit 23 is provided with a flue gas cooling cavity 231, the top of the flue gas cooling cavity 231 is provided with a cooling spraying unit, the flue gas cooling cavity 231 is also provided with a flue gas inlet 203 and a cooling flue gas outlet 204, the flue gas inlet 203 is communicated with the first flue gas outlet 102 and the second flue gas outlet 105, the top of the water seal box 21 is provided with a cooling water inlet, and the cooling water inlet is communicated with the bottom of the flue gas cooling cavity 231; according to the flow direction of the flue gas, the flue gas spraying and washing units 24 at all levels are sequentially communicated and arranged at the downstream of the cooling flue gas outlet 204, each flue gas spraying and washing unit 24 is provided with a flue gas spraying and washing cavity 241, the top of the flue gas spraying and washing cavity 241 is provided with a washing spraying unit, the top of the water seal box 21 is also provided with a washing water inlet, and the washing water inlet is communicated with the bottom of the flue gas spraying and washing cavity 241; the lye pool 22 is connected with both the cooling spray unit and the washing spray unit for supplying lye.

During the actual treatment of the fly ash, the fly ash is fed into the double-chamber melting furnace 10 through the main feed port 101 and/or the auxiliary feed port 104, and the heating electrode 14 is turned on to melt the fly ash to be treated and form a molten pool. This process corresponds to a start-up phase, in which a molten pool is formed in advance in the double-chamber melter 10, after which the fly ash can be subjected to a continuous melting process. Unlike a conventional electric melting furnace, the double-chamber melting furnace 10 of the present invention is divided horizontally into a main reaction chamber 11 and a secondary reaction chamber 12, and has top feed ports both near a partition wall 13 and heating electrodes 14 disposed in the secondary reaction chamber 12. After the molten pool is formed, the fly ash to be treated can be continuously fed into the molten pool of the main reaction chamber 11 through the main feed inlet 101 so as to be subjected to melting treatment; during the melting process, the molten pool in the side reaction chamber 12 may be heated by the heating electrode 14. In this way, since the heating electrode 14 only heats in the secondary reaction chamber 12, the furnace chamber above the molten pool of the main reaction chamber 11 and the secondary reaction chamber 12 is separated by the partition wall 13, so that the temperature of the molten pool in the main reaction chamber 11 is heated by the heat conduction action of the molten pool in the secondary reaction chamber 12, thereby forming a molten pool with a lower temperature in the main reaction chamber 11 than in the secondary reaction chamber 12, and the furnace chamber above the molten pool in the main reaction chamber 11 is in a cold-top state. Such a temperature distribution has the following effects: the temperature of the melting pool of the secondary reaction chamber 12 is higher, so that the fly ash is ensured to be fully melted, heavy metal components can be fully solidified in silicate to form a complete glass state, the purposes of harmlessness and reclamation of heavy metals are achieved, and the salt in the fly ash is also melted; the temperature of the molten pool of the main reaction chamber 11 is slightly low, so that salt in the fused fly ash can be fully separated out, and the fused salt can be enriched on the surface layer of the molten pool due to lower density (compared with the silicate solidified by heavy metal, the fused salt is lighter and is not mutually soluble); more importantly, because the hearth above the molten pool of the main reaction chamber 11 is in a cold top state and the air temperature is lower, the volatilization of the molten salt is effectively inhibited, and a molten salt layer in a semi-molten state can be formed on the surface of the molten pool of the main reaction chamber 11. And because the main feed inlet 101 and the auxiliary feed inlet 104 are both arranged close to the partition wall, and the fly ash raw material can be mainly fed from the main feed inlet 101 in the actual feeding process, so that the fly ash is mainly melted in the molten pool near the lower part of the partition wall, on one hand, the molten salt layer on the surface of the molten pool of the main reaction chamber 11 cannot be damaged by feeding against the partition wall, and on the other hand, most of the molten salt in the fly ash can be melted, layered and enriched on the surface of the molten pool of the main reaction chamber 11. Along with the continuous progress of the melting reaction, the fused salt can be fished out through the salt fishing opening 103 periodically, and then the separation of most of the chlorine salt in the fly ash can be realized. Meanwhile, a small amount of fly ash raw material can be supplemented into the secondary reaction chamber 12 through the secondary feed inlet 104 to ensure that the molten pool contains a small amount of salt, and the small amount of salt is beneficial to improving the conductivity of the molten pool, is beneficial to heating the heating electrode 14 and can improve the heating efficiency of the heating electrode 14.

The flue gas generated by the main reaction chamber 11 and the secondary reaction chamber 12 can be used as the flue gas to be purified and sent into the flue gas purification device 20 through the flue gas inlet 203 for flue gas purification treatment, and in the specific treatment process, the flue gas to be purified (the main components are HCl and SO)₂、CO₂Air leakage) can be introduced into the flue gas cooling chamber 231 first, and the alkali liquor pool 22 is used to supply alkali liquor to the cooling spray unit so as to cool the flue gas to be purified (here, in addition to the cooling effect, the alkali liquor can also remove a part of smoke dust and acidic substances carried in the flue gas), thereby forming cooled flue gas. The cooled flue gas can then pass through the multi-stage flue gas spraying and washing unit 24 in sequence, and the multi-stage spraying and washing of alkali liquor is carried out in the flue gas spraying and washing cavities 241 at all stages, so as to form purified flue gas. The smoke dust and the acidity in the smoke are treated by the quenching process and the multi-stage spraying and washing processSubstances, chlorides, etc. are sufficiently removed (a small portion of the volatile salts generated during melting of the fly ash are sufficiently removed in the process). In addition, because the flue gas cooling unit 23 and the flue gas spraying and washing unit 24 in the flue gas purification device are both positioned above and connected with the water seal tank 21, the spraying liquid formed in the spraying, washing and cooling processes carries the collected flue gas to enter the water seal tank 21 below for separation, the bottom sludge can be discharged from the sludge discharge port 202, and the overflow liquid can be discharged from the overflow port 201.

Therefore, the device provided by the invention is used for melting the fly ash and purifying the flue gas, most of salt in the fly ash can be separated out through the salt fishing port of the main reaction chamber in the process of melting the fly ash by using the double-chamber melting furnace technology, the corrosion of the fly ash after the salt is extracted to refractory materials is delayed in the melting process, the service life of the refractory materials of the electric furnace is prolonged, the system is prevented from being bonded, and the stable operation in the operation process is ensured. Heavy metal pollutants in the fly ash are solidified in the molten slag during the melting process to form harmless products. Meanwhile, a small part of residual salt can be used as an important conductive medium to play a conductive role in the electrode heating process, so that the electrode heating efficiency is improved. The small amount of salt can be volatilized to enter a subsequent flue gas purification device integrating quenching, deacidifying alkali, high-efficiency dedusting and chlorine washing, is quenched along with flue gas, is removed by multi-stage spraying, washing and separating, is finally dissolved in alkali liquor to form high-salt wastewater, overflows and is discharged, and can be sent to a salt extraction device. The flue gas purification device has the advantages of complete system functions, short flow, low investment, contribution to low-cost standard emission of flue gas and thorough fault-free operation.

In a word, the device provided by the invention is used for melting and purifying the flue gas to obtain two products of glass slag and molten salt to the maximum extent, wherein the two products account for more than 90% of solid products, the toxic leaching characteristics of the two products are lower than the national limit value through detection, the two products can be used as non-dangerous waste for disposal, and the salt and sludge (insoluble substances) collected by the overflow liquid as high-salt wastewater are lower than 10%. Through the separation of the molten salt in the melting process, the salt content of a molten pool in the fly ash melting process is reduced, the service lives of a refractory material and a furnace body are prolonged, the system blockage and frequent cleaning are reduced, and the safety of a heating electrode is also ensured. The invention effectively solves the problems of easy corrosion of the furnace body, unstable operation in the melting process and easy volatilization of chlorine salt to pollute the environment caused by the chlorine salt by using a simple fly ash melting and flue gas purifying treatment device, does not need to wash the whole fly ash to cause a great deal of waste of water resources, equipment resources and the like, reduces the system investment for treating the fly ash, has low cost and stable operation, and is very suitable for industrialized large-scale application.

It should be noted here that the device of the present invention is applicable to melting of fly ash with high chloride content and flue gas purification treatment, and is also applicable to ordinary fly ash,

in order to better maintain the bath temperature of the main reaction chamber 11 during the actual operation process, because the bath temperature of the main reaction chamber 11 is lower than the bath temperature of the secondary reaction chamber 12, in a preferred embodiment, as shown in fig. 1, a heat supplementing port 107 is further provided on the side wall of the main reaction chamber 11 at a position lower than the salt scooping port 103, and the apparatus further includes a heat supplementing unit for supplementing heat to the main reaction chamber 11 through the heat supplementing port 107. The heat supplementing operation is mainly performed when the temperature of the molten pool of the main reaction chamber 11 is insufficient, so as to ensure the temperature of the molten pool to be stable and promote the fly ash to be more fully melted.

The particular reheat unit may be of the type commonly used in the metallurgical arts, including but not limited to, a reheat electrode or a fuel lance. The heat compensating electrode and the heating electrode 14 are preferably graphite electrodes or self-baking electrodes, and the electrode pressing and releasing can be realized by adopting compressed air, hydraulic pressure, jacks and the like. The specific feed opening quantity can be adjusted, preferably, main feed opening 101 can be 2~6, vice feed opening 104 can be 1~ 3.

Preferably, one or more heating electrodes 14 are provided, and more preferably, 3 to 6 electrode openings 106 are provided, and the heating electrodes 14 are disposed in the electrode openings 106 in a one-to-one correspondence manner and extend to the inside of the side reaction chamber 12.

In order to form a more stable temperature distribution state in the process of melting and processing the fly ash, the temperature of a molten pool of the secondary reaction chamber 12 is kept higher, the temperature of a molten pool of the main reaction chamber 11 is kept relatively lower, and a cold roof environment is kept above the molten pool of the main reaction chamber 11, so that heavy metals in the fly ash are melted to form a glass state, salt is fully precipitated, and a semi-molten salt layer is formed on the surface of the molten pool of the main reaction chamber 11, so that the molten salt and the heavy metals are more fully separated, in a preferred embodiment, the volume ratio of the main reaction chamber 11 to the secondary reaction chamber 12 in the double-chamber melting furnace 10 is 1-1.5: 1.

In a preferred embodiment, the salt scoop 103 is located on the side wall of the main reaction chamber 11 above the bottom of the partition wall 13; a space is arranged between the partition wall and the bottom wall inside the double-chamber melting furnace 10 to form a communication channel; and the distance between the bottom of the partition wall and the inner bottom wall of the double-chamber melting furnace 10 is denoted as h₁The total height of the partition being denoted h₂Then 1/3 < h₁/ h₂Is less than 1. So set up, in continuous processing flying dust process, the molten bath height is more suitable, is favorable to improving production efficiency on the one hand, more can further improve the stability of each regional temperature on the one hand, exerts each regional function, realizes the better separation of fused salt and heavy metal. Preferably, during the actual production process, the bottom of the partition wall 13 is flush with the highest level of the bath, so as to facilitate the definitive separation of the two zones of the furnace.

Preferably, the partition wall 13 is a water-cooled partition wall or an air-cooled partition wall. The water-cooling partition wall or the air-cooling partition wall can better isolate the temperature transfer in the hearth above the double-chamber molten pool, so that the temperature of the hearth of the main reaction chamber 11 is more stable, the volatilization of the molten salt is further reduced, and the molten salt is enriched in a semi-molten state molten salt layer and is fished out from the surface of the molten pool.

In an actual production process, in consideration of the thermal efficiency of the heating electrode 14, in a preferred embodiment, the lower end of the heating electrode 14 is located lower than the bottom of the partition wall 13. By the arrangement, the heating electrode 14 can keep high heating efficiency, and meanwhile, the phenomenon that a large amount of molten salt volatilizes due to overhigh temperature of the molten pool is avoided.

In order to make the substances burn more fully, in a preferred embodiment, as shown in fig. 1, the device further comprises a vertical combustion chamber 15, wherein the vertical combustion chamber 15 is respectively communicated with the first flue gas outlet 102, the second flue gas outlet 105 and the flue gas inlet 203, and the vertical combustion chamber 15 is used for burning the flue gas discharged from the first flue gas outlet 102 and the second flue gas outlet 105. Specifically, a natural gas lance or a combustion nozzle may be provided in the vertical combustor 15.

More preferably, the vertical combustion chamber 15 is arranged above the second fume outlet 105 and is vertically connected to the second fume outlet 105; and the top of the vertical combustion chamber 15 is also provided with an ash removal unit 16, and the ash removal unit 16 is used for performing ash removal treatment on the inner wall of the vertical combustion chamber 15. The inner wall of the vertical combustion chamber 15 can be regularly cleaned by the ash cleaning unit 16, so that blockage is reduced. Meanwhile, because the vertical combustion chamber 15 is vertically connected with the second flue gas outlet 105, the dust cleaned in the ash cleaning process can directly fall into the melting bath of the secondary reaction chamber 12 for secondary treatment. The ash removal unit 16 may be an automatic cleaner for rotary telescopic cleaning.

The fly ash raw materials only need adopt the type commonly used in the fly ash field of handling can, for the convenience feeding, in an preferred embodiment, above-mentioned device still includes batching unit, and batching unit is used for batching fly ash and flux, and batching unit links to each other with main charge door 101 through first feeder hopper 17, and batching unit links to each other with vice charge door 104 through second feeder hopper 18. During operation, the fly ash material may be fed into the first hopper 17 and the second hopper 18 by means of a telescopic injection feed or a screw extrusion feed.

In a preferred embodiment, the device further comprises a salt fishing device, and the salt fishing device carries out salt fishing through the salt fishing port 103. The salt scooping device can be an automatic salt raking device to regularly rake out the molten salt on the surface of the molten pool from the salt scooping port 103.

As described above, the flue gas to be purified firstly enters the flue gas cooling unit 23 to be cooled under the action of the spraying alkali liquor, and the cooled flue gas sequentially enters the multi-stage flue gas spraying washing unit 24 to be washed by the multi-stage spraying alkali liquor, so that the flue gas can be fully purified. In the process, in order to make the flue gas pass through more stably, in a preferred embodiment, the flue gas cooling unit 23 further includes a cooling flue gas discharge pipeline 232, one end of the cooling flue gas discharge pipeline 232 is connected to the cooling flue gas outlet 204, and the other end is connected to the top of the water seal tank 21; wherein the cooling flue gas exhaust line 232 is a venturi tube; alternatively, the cooling flue gas discharge pipe 232 is provided with a first air inducing device. In the same way, preferably, in the multi-stage flue gas spraying and washing units 24 sequentially communicated, the flue gas spraying and washing units 24 except for the last stage further include a spraying flue gas discharge pipeline 242, one end of the spraying flue gas discharge pipeline 242 is connected with the flue gas spraying and washing cavity 241, and the other end is connected with the top of the water seal tank 21; wherein, the spraying flue gas discharging pipeline 242 is a venturi tube; or, a second air inducing device is arranged on the spraying flue gas discharging pipeline 242.

In the continuous treatment process, the collected spray liquid is arranged below the overflow port 201 in the water seal tank 21, and a pore is formed between the overflow port 201 and the inner top wall of the water seal tank 21. When the cooling flue gas exhaust pipeline 232 is a venturi tube and the spraying flue gas exhaust pipeline 242 is a venturi tube, under the action of the venturi effect, self-suction force can be formed on the basis of no external power equipment, and the flue gas to be purified moves according to the routes of the flue gas cooling cavity 231, the cooling flue gas exhaust pipeline 232, the upper part of the water seal box 21, the first-stage flue gas spraying and washing cavity 241, the first-stage spraying flue gas exhaust pipeline 242, the upper part of the water seal box 21, the next-stage flue gas spraying and washing cavity 241, the next-stage spraying flue gas exhaust pipeline 242 under the action of the self-suction force, so that cooling and multistage spraying and washing are completed. Certainly, under the action of the first air inducing device and the second air inducing device, the flue gas can also be cooled and washed in a multi-stage spraying mode under the action of air induction according to the route. The venturi tube is more preferably used for the purpose of saving energy consumption and equipment cost.

More preferably, the cooling flue gas exhaust line 232 is a plurality arranged in parallel. The spray flue gas discharge pipes 242 in each flue gas spray washing unit 24 are provided in parallel. So set up, be favorable to further improving flue gas treatment effeciency and handling capacity, equipment throughput and treatment effeciency are higher. The plurality here is at least two, such as three, four, etc.

More preferably, as shown in fig. 1, the last stage flue gas spray washing unit 24 further comprises a purified flue gas discharge pipeline 243, and the purified flue gas discharge pipeline 243 is connected with the flue gas spray washing cavity 241 of the last stage flue gas spray washing unit 24. Thus, the purified flue gas can be stably discharged. In the actual operation process, an induced draft device can be arranged, so that the smoke can be discharged more stably and efficiently. The pipelines can be selectively provided with a gate and the like to control the processing progress and the emission of the flue gas.

In order to maximize the spray settling capacity of the watertight box 21, in a preferred embodiment, the overflow port 201 is provided at a side of the watertight box 21 near the top wall of the interior. More preferably, the distance between the overflow port 201 and the top wall inside the water seal tank 21 is controlled to 1/20-1/10 of the total height of the water seal tank 21, so that on one hand, the settling separation of the collected spray liquid is not affected, on the other hand, a flow channel is provided for the flue gas discharged by each cooling flue gas discharge pipeline 232 and each spray flue gas discharge pipeline 242, so that the flue gas can move more stably according to the route, and the cooling and the multi-stage spray washing are completed.

In a preferred embodiment, a sludge collecting unit 211 is arranged at the bottom inside the water sealed box 21, and the sludge collecting unit 211 is used for collecting sludge deposited inside the water sealed box 21 and discharging the sludge through the sludge discharging port 202. The collected smoke dust and the like carried in the spray liquid can be settled at the bottom of the water seal tank 21, and the sludge can be conveniently conveyed out through the sludge collecting unit 211. More preferably, the mud collecting unit 211 is an inclined scraper, and the inclined scraper inclines downwards from a direction far away from the mud discharging port 202 to a direction close to the mud discharging port 202; alternatively, the mud collecting unit 211 is a screw conveyor.

In order to make more efficient use of resources, in a preferred embodiment the apparatus further comprises a dewatering device 25, the dewatering device 25 being in communication with the sludge discharge 202. After the sludge is dewatered by the dewatering equipment 25, a liquid phase and a solid phase can be formed. The dewatering device 25 preferably uses a filter press and the solid phase is bottom sludge, which is preferably returned and dosed with fly ash. More preferably, the dewatering device 25 has a liquid phase outlet and a solid phase outlet, the liquid phase outlet being in communication with the lye tank 22. The liquid phase returns to the lye pool 22 to be recycled, and the prepared lye is sprayed again. After the alkali liquor is sprayed and washed for several times, the alkali liquor can be fed into high-salt water for treatment according to the change of its components.

In a preferred embodiment, a slag discharge port is further arranged on one side of the secondary reaction chamber 12 far away from the main reaction chamber 11; the slag discharge port comprises a bottom slag port 108 positioned at the lower part of the side wall of the secondary reaction chamber 12 and an upper slag port 109 positioned above the bottom slag port 108. In the actual operation process, the bottom slag hole 108 is usually discharged once for a long time, or a special/emergency situation occurs, and the furnace needs to be stopped to empty the slag in the furnace; the discharging frequency of the upper slag hole 109 is 1-2 times in 1 day, and the glassy state heavy metal collected from the upper part of the melting pool of the secondary reaction chamber 12 is discharged, so that the vitrification disposal of dangerous waste is realized.

In addition, the furnace body of the double-chamber melting furnace 10 of the invention can be a horizontal furnace body such as a round furnace body, a rectangular furnace body or an oval furnace body, the material of the furnace body is preferably a steel plate, the lining is a refractory material, the specific refractory material is made of a common refractory material in the field of metallurgy, preferably an aluminum-chromium-zirconium high-strength wear-resistant corrosion-resistant special refractory material is adopted, and a water jacket is embedded as required, namely the water jacket is coated outside the refractory material. Specifically, the water jacket can be coated near the slag line (where the liquid level of the molten pool floats up and down most frequently), wherein the corrosion of the refractory is the most serious, and the water jacket can be coated outside the refractory of the slag line to reduce the corrosion of the refractory and prolong the service life of the furnace. Preferably, the roof structure of the dual chamber melting furnace 10 employs a heat resistant high strength ramming charge roof, such as a chromium containing refractory.

The dual chamber melter 10 is preferably also equipped with other auxiliary test systems (including temperature measurement, pressure measurement, etc.) to monitor the temperature and pressure conditions of the various functional zones in real time.

According to another aspect of the present invention, there is also provided a method for melting and flue gas cleaning fly ash, which uses the above apparatus to perform melting and flue gas cleaning treatment on fly ash, the method comprising the following steps: step S1, mixing the fly ash and optional flux to form fly ash to be treated; firstly, feeding materials into the double-chamber melting furnace 10 through a main feed inlet 101 and/or an auxiliary feed inlet 104, and starting a heating electrode 14 to melt the fly ash to be treated and form a molten pool; step S2, after the molten pool is formed, continuously feeding the fly ash to be treated into the molten pool of the main reaction chamber 11 through the main feed port 101 so as to melt the fly ash; in the process of melting treatment, a molten pool in the secondary reaction chamber 12 is heated through the heating electrode 14, the temperature of the molten pool in the secondary reaction chamber 12 is controlled to be 1200-1400 ℃, and the temperature of a hearth above the molten pool in the secondary reaction chamber 12 is controlled to be 700-1200 ℃; carrying out heat conduction heating on a molten pool in the main reaction chamber 11 through a molten pool in the auxiliary reaction chamber 12, controlling the temperature of the molten pool in the main reaction chamber 11 to be 900-1200 ℃, and controlling the temperature of a hearth above the molten pool in the main reaction chamber 11 to be 200-500 ℃; along with the progress of the melting treatment, a molten salt layer is formed on the surface of a molten pool of the main reaction chamber 11, slag is formed at the bottom of the double-chamber melting furnace 10, the flue gas generated in the main reaction chamber 11 is discharged from the first flue gas outlet 102, and the flue gas generated in the secondary reaction chamber 12 is discharged from the second flue gas outlet 105; fishing out the molten salt in the molten salt layer through a salt fishing port 103; step S3, sending the flue gas discharged from the first flue gas outlet 102 and the second flue gas outlet 105 as the flue gas to be purified into the flue gas purification device 20 through the flue gas inlet 203 for flue gas purification treatment; firstly, introducing flue gas to be purified into a flue gas cooling cavity 231, and supplying alkali liquor to a cooling spraying unit by using an alkali liquor pool 22 so as to cool the flue gas to be purified to form cooled flue gas and first spraying liquor; the cooled flue gas passes through the flue gas spraying washing cavity 241 of the multi-stage flue gas spraying washing unit 24 in sequence, and alkali liquor is supplied to each washing spraying unit by using the alkali liquor pool 22, so that the cooled flue gas is subjected to multi-stage spraying washing in sequence to form purified flue gas and second spraying liquor; the first spraying liquid and the second spraying liquid enter a water seal tank 21 for sludge precipitation to obtain overflow liquid and sludge; the overflow liquid is discharged through the overflow port 201, and the sludge is discharged through the sludge discharge port 202.

As mentioned above, the above device can heat the molten pool temperature in the main reaction chamber 11 by the heat conduction of the molten pool in the secondary reaction chamber 12 during the fly ash melting process, so that the molten pool temperature in the main reaction chamber 11 is lower than that in the secondary reaction chamber 12, and the furnace hearth above the molten pool in the main reaction chamber 11 is in a cold top state. Such a temperature distribution has the following effects: the temperature of a molten pool of the secondary reaction chamber 12 is higher, so that the fly ash is fully melted, heavy metal components can form a complete glass state, and salt is also melted; the temperature of a molten pool of the main reaction chamber 11 is slightly low, so that salt in the molten fly ash can be fully separated out, and the molten salt can be enriched on the surface layer of the molten pool due to low density; more importantly, because the hearth above the molten pool of the main reaction chamber 11 is in a cold top state and the air temperature is lower, the volatilization of the molten salt is effectively inhibited, and a molten salt layer in a semi-molten state can be formed on the surface of the molten pool of the main reaction chamber 11. And because the main feed inlet 101 and the auxiliary feed inlet 104 are both arranged close to the partition wall, and the fly ash raw material can be mainly fed from the main feed inlet 101 in the actual feeding process, so that the fly ash is mainly melted in the molten pool near the lower part of the partition wall, on one hand, the molten salt layer on the surface of the molten pool of the main reaction chamber 11 cannot be damaged by feeding against the partition wall, and on the other hand, most of the molten salt in the fly ash can be melted, layered and enriched on the surface of the molten pool of the main reaction chamber 11. Particularly, in the method, the temperature of a molten pool in the secondary reaction chamber 12 is controlled to be 1200-1400 ℃, the temperature of a hearth above the molten pool in the secondary reaction chamber 12 is controlled to be 700-1200 ℃, the temperature of the molten pool in the main reaction chamber 11 is controlled to be 900-1200 ℃, and the temperature of the hearth above the molten pool in the main reaction chamber 11 is controlled to be 200-500 ℃, so that the effects of all regions can be exerted, and the molten salt and the glassy state heavy metal can be separated more fully. Along with the continuous progress of the melting reaction, the fused salt can be fished out through the salt fishing opening 103 periodically, and then the separation of most of the chlorine salt in the fly ash can be realized. Meanwhile, a small amount of fly ash raw material can be supplemented into the secondary reaction chamber 12 through the secondary feed inlet 104 to ensure that the molten pool contains a small amount of salt, and the small amount of salt is beneficial to improving the conductivity of the molten pool, is beneficial to heating the heating electrode 14 and can improve the heating efficiency of the heating electrode 14.

The flue gas of main reaction chamber 11 and the output of secondary reaction chamber 12 can be regarded as waiting to purify the flue gas and send into flue gas purification device 20 through flue gas inlet 203 and carry out the gas cleaning and handle, and in the concrete processing procedure, wait to purify the flue gas and can let in flue gas cooling chamber 231 earlier to utilize lye pond 22 to spray the unit supply alkali lye to cooling, with treating to purify the flue gas and carry out cooling treatment (here except cooling effect, alkali lye also can get rid of a part of smoke and dust, the acidic material that carries in the flue gas), form the cooling flue gas, and the temperature can be below 200 ℃ usually. The cooled flue gas can then pass through the multi-stage flue gas spraying and washing unit 24 in sequence, and the multi-stage spraying and washing of alkali liquor is carried out in the flue gas spraying and washing cavities 241 at all stages, so as to form purified flue gas. Through the quenching process and the multi-stage spraying and washing process, the smoke dust, acidic substances, chlorides and the like in the flue gas are fully removed (a small part of volatile salt generated in the fly ash melting process is fully removed in the process). In addition, because the flue gas cooling unit 23 and the flue gas spraying and washing unit 24 in the flue gas purification device are both positioned above and connected with the water seal tank 21, the spraying liquid formed in the spraying, washing and cooling processes carries the collected flue gas to enter the water seal tank 21 below for separation, the bottom sludge can be discharged from the sludge discharge port 202, and the overflow liquid can be discharged from the overflow port 201.

Therefore, the device provided by the invention is used for melting the fly ash and purifying the flue gas, most of salt in the fly ash can be separated out through the salt fishing port of the main reaction chamber in the process of melting the fly ash by using the double-chamber melting furnace technology, the corrosion of the fly ash after the salt is extracted to refractory materials is delayed in the melting process, the service life of the refractory materials of the electric furnace is prolonged, the system is prevented from being bonded, and the stable operation in the operation process is ensured. Heavy metal pollutants in the fly ash are solidified in the molten slag during the melting process to form harmless products. Meanwhile, a small part of residual salt can be used as an important conductive medium to play a conductive role in the electrode heating process, so that the electrode heating efficiency is improved. The small amount of salt can be volatilized and enter a subsequent flue gas purification device to be quenched along with the flue gas, and then is removed through multi-stage spraying, washing and separating.

In a word, the method of the invention carries out melting and flue gas purification treatment on the fly ash, can maximally obtain two products of glass slag and molten salt, which account for more than 90% of solid products, and through detection, the toxicity leaching characteristics of the two products are both lower than the national limit value, and the two products can be used as non-dangerous waste for disposal, and the overflow liquid is used as high-salt wastewater, and the collected salt and sludge (insoluble substances) are lower than 10%. Through the separation of the molten salt in the melting process, the salt content of a molten pool in the fly ash melting process is reduced, the service lives of a refractory material and a furnace body are prolonged, the system blockage and frequent cleaning are reduced, and the safety of a heating electrode is also ensured. The method effectively solves the problems of easy corrosion of the furnace body, unstable operation in the melting process and easy volatilization of the chlorine salt to pollute the environment caused by the chlorine salt, does not need to wash the whole fly ash to cause a great deal of waste of water resources, equipment resources and the like, has low cost, and is very suitable for industrial large-scale application.

The specific type of the flux can be the type commonly used in the field of fly ash treatment, for example, iron tailings, nonferrous metallurgical slag, hazardous waste incineration bottom slag, quartz sand and other siliceous materials can be used, and the specific addition amount can be selected according to the slag type, which is the conventional technology in the field and is not described herein again.

In order to better maintain the bath temperature of the main reaction chamber 11 during the actual operation because the bath temperature of the main reaction chamber 11 is lower than the bath temperature of the auxiliary reaction chamber 12, in a preferred embodiment, during the melting process of step S2, when the bath temperature in the main reaction chamber 11 is lowered, the fly ash to be treated is supplemented from the heat supplementing port 107 through the heat supplementing unit and/or the fly ash to be treated is supplemented to the bath of the auxiliary reaction chamber 12 through the auxiliary feed port 104. The fly ash to be treated is added into the molten pool of the secondary reaction chamber 12 through the secondary feed inlet 104, so that the molten pool is ensured to contain a small amount of salt, and the molten pool has certain conductivity, thereby improving the heating efficiency of the heating electrode 14. Of course, the skilled in the art can also monitor the supplemented fly ash to be treated by detecting the chlorine salt content in the molten pool, and it is only more convenient to monitor the temperature change, and when the temperature is insufficient, the temperature can be directly or indirectly raised by the two methods.

The specific heat-supplementing unit can adopt the common type in the metallurgical field, including but not limited to supplementing heat to the molten pool of the main reaction chamber 11 by the heat-supplementing electrode, or injecting fuel into the molten pool of the main reaction chamber 11 for supplementing heat; preferably, the fuel is natural gas and/or fuel oil. Specific fuel oils include, but are not limited to, gasoline, diesel or biomass oil.

In order to further reduce the volatilization of the molten salt, in a preferred embodiment, during the melting treatment in step S2, the furnace pressure above the molten pool of the main reaction chamber 11 is controlled to be-100 Pa to 0Pa, and the furnace pressure above the molten pool of the secondary reaction chamber 12 is controlled to be-100 Pa to 0 Pa. The electric furnace is beneficial to reducing the escape of harmful gas generated by the electric furnace to the environment under the micro negative pressure state.

In order to make the substances more fully combusted, step S3 is also included in the flue gas discharged from the dual chamber, which carries some unreacted sulfur, carbon monoxide and so on, and some other combustible substances, before the step of feeding the flue gas to be purified into the flue gas purification device 20 for flue gas purification treatment, in a preferred embodiment: the flue gas to be purified is subjected to combustion treatment by the vertical combustion chamber 15.

More preferably, the vertical combustion chamber 15 is arranged above the second fume outlet 105 and is vertically connected to the second fume outlet 105; the method further comprises the following steps: the inner wall of the vertical combustion chamber 15 is subjected to ash removal by an ash removal unit 16 at the top of the vertical combustion chamber 15. The inner wall of the vertical combustion chamber 15 can be regularly cleaned by the ash cleaning unit 16, so that blockage is reduced. Meanwhile, because the vertical combustion chamber 15 is vertically connected with the second flue gas outlet 105, the dust cleaned in the ash cleaning process can directly fall into the melting bath of the secondary reaction chamber 12 for secondary treatment.

In a preferred embodiment, in step S3, after the flue gas to be purified is introduced into the flue gas cooling chamber 231 for cooling treatment, the cooled flue gas is sent to the top of the water-sealed box 21 by the cooled flue gas discharge pipeline 232, and then enters the flue gas spray washing unit 24; when the cooling flue gas discharge pipeline 232 is a venturi tube, the cooling flue gas enters the flue gas spraying and washing unit 24 through the top of the water seal tank 21 by suction force; when the cooling flue gas discharge pipeline 232 is provided with the first air inducing device, the cooling flue gas passes through the top of the water seal box 21 to enter the flue gas spraying and washing unit 24 under the air inducing effect of the first air inducing device.

In a preferred embodiment, in step S3, in the process of performing multi-stage spraying washing by passing the cooling flue gas through the flue gas spraying washing chamber 241 of the multi-stage flue gas spraying washing unit 24 in sequence, the spraying flue gas exhaust pipe 242 is used to send the spraying flue gas formed by the flue gas spraying washing chamber 241 of the previous stage into the top of the water seal box 21, and then the spraying flue gas enters the flue gas spraying washing chamber 241 of the next stage; when the spraying flue gas discharge pipeline 242 is a venturi tube, the spraying flue gas formed by the front stage flue gas spraying washing cavity 241 passes through the top of the water seal box 21 by self-suction force and enters the rear stage flue gas spraying washing cavity 241; when the second induced air device is arranged on the spraying flue gas discharge pipeline 242, the spraying flue gas formed by spraying the front stage flue gas into the washing cavity 241 passes through the top of the water seal box 21 and enters the rear stage flue gas into the washing cavity 241 through the induced air action of the second induced air device.

More preferably, the above method further comprises: the sludge is dehydrated by a dehydration device 25 to form a liquid phase and a solid phase; returning the solid phase to step S1 for compounding; the liquid phase is returned to the caustic bath 22.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.

Example 1

The main chemical components of fly ash are As follows (except the following components, a small amount of other components such As As₂O₃、HgO）：

The device shown in fig. 1 is adopted to carry out fly ash melting and flue gas purification treatment, wherein the number of the main charging openings is 3, and the number of the auxiliary charging openings is 2. The number of the electrode openings is 3, and the heating electrodes are correspondingly arranged in the electrode openings one by one and extend to the interior of the side reaction chamber. The volume ratio of the main reaction chamber to the secondary reaction chamber was 1.2: 1. The salt fishing port is positioned on the side wall of the main reaction chamber and higher than the bottom of the partition wall; a space is arranged between the partition wall and the bottom wall inside the double-chamber melting furnace to form a communication channel; and the distance between the bottom of the partition wall and the bottom wall of the interior of the double-chamber melting furnace is recorded as h₁The total height of the partition being denoted h₂Then h is₁/ h₂= 1/2. The side wall of the main reaction chamber is also provided with a heat supplementing port which is provided with a heat supplementing electrode and is lower than the salt fishing port. The heat-supplementing electrode and the heating electrode both adopt graphite electrodes. The vertical combustion chamber is arranged at the second flue gas outletA rotary telescopic automatic cleaning machine is arranged above the combustion nozzle. The flue gas spraying unit comprises a group of flue gas cooling units and two stages of flue gas spraying and washing units, and the flue gas spraying units are both provided with Venturi tubes for self-suction flue gas spraying and washing. Each group of flue gas spraying and washing units is provided with three Venturi tubes. The distance between the overflow of the water seal box and the top wall of the water seal box is controlled at 1/10 of the total height of the water seal box. And the alkali liquor pool supplies a sodium hydroxide aqueous solution to the flue gas cooling unit and the flue gas spraying and washing unit.

The specific process steps are as follows:

the fly ash is granulated by a dry method and mixed with quartz sand (or other siliceous solid wastes) to form fly ash to be treated, and then the fly ash is conveyed into a first feed hopper and a second feed hopper by screws, wherein the mass fraction of the fly ash is 60-80%, and the mass fraction of the quartz sand is 20-40%.

Starting a heating electrode, feeding a first batch of raw materials into a double-chamber melting furnace to be melted to form a molten pool, controlling the temperature of the molten pool in a secondary reaction chamber to be 1200-1400 ℃, controlling the temperature of a hearth to be 700-1200 ℃, controlling the easy temperature of a main reaction chamber to be 900-1200 ℃ and controlling the temperature of the hearth to be 200-500 ℃; after the temperature is controlled within the above range, the fly ash to be treated is continuously fed into the molten pool of the main reaction chamber, and the temperature of each zone is maintained within the above range by adjusting the heating electrode and the heat-compensating electrode. Meanwhile, if the temperature of the main reaction chamber is monitored to be continuously reduced, a part of fly ash to be treated is added into the auxiliary reaction chamber through the auxiliary charging port, and the conductivity of a molten pool is improved by using chloride ions and the like in the fly ash to be treated, so that the temperature is improved by using a heating electrode. Through the treatment process, a molten salt layer is formed on the surface of a molten pool of the main reaction chamber, the molten salt is raked out from a salt fishing port by a salt raking device at intervals, and the generated molten salt is subjected to CaCl₂NaCl and KCl are taken as main components, and the mass fraction is more than or equal to 90 percent. In order to prevent the flue gas from escaping, the air pressure of the main reaction chamber and the secondary reaction chamber is controlled to be in a micro negative pressure state of-50 Pa. Along with the proceeding of the melting treatment, 1-2 times a day discharges the glass state heavy metal enriched on the surface of the main reaction chamber melting pool through a slag feeding port, the glass treatment is carried out, and the finally obtained glass slag is lower than the technical requirement of the product of the glass treatment of solid wasteWhen the vitrified product specified in the above statement is used as a building material or a blasting material, the content limit of the leachable harmful substance (the water leaching limit of Cu is 1.0mg/L, the acid leaching limit is 1.0mg/L, the water leaching limit of Zn is 1.0mg/L, the acid leaching limit is 1.0mg/L, the water leaching limit of Cd is 0.005mg/L, the acid leaching limit is 0.03mg/L, the water leaching limit of Pb is 0.01mg/L, the acid leaching limit is 0.3mg/L, the water leaching limit of Hg is 0.001mg/L, the water leaching limit of Ni is 0.02mg/L, the acid leaching limit is 0.2mg/L, the water leaching limit of Mn is 0.1mg/L, and the acid leaching limit is 1.0 mg/L) can be obtained. The output of the molten salt and the glass slag accounts for more than 90 percent of the total amount of the solid product.

The main reaction chamber and the auxiliary reaction chamber continuously discharge flue gas generated by melting, and the main component of the flue gas is SO₂、HCl、H₂O、CO₂CO and dust, and the amount of flue gas is about 20-100 Nm³/h·t_{Ash of}. And the flue gas is introduced into the vertical combustion chamber for secondary combustion, then enters the flue gas cooling cavity for cooling under the spraying action of the sodium hydroxide aqueous solution, and is further subjected to continuous two-stage sodium hydroxide aqueous solution spraying and washing in the two-stage flue gas spraying and washing cavity after the cooled flue gas is formed. In the washing process, the flue gas flows in a self-suction manner under the action of each stage of Venturi tube, and an air inducing device is not needed. The flue gas after the final stage of spray washing is discharged through a chimney, and the discharge index of the flue gas is lower than the pollutant limit value (the smoke dust discharge limit value is 30 mg/Nm) in the flue gas discharged by the hazardous waste incineration facility specified in the hazardous waste incineration pollution control Standard³，SO₂Emission limit of 200mg/Nm³HF emission limit of 2.0mg/Nm³HCl emission limit of 50mg/Nm³The nitrogen oxide emission limit is 400mg/Nm³The emission limit of dioxins is 0.1ngTEQ/Nm³). The absorption liquid which falls down in the flue gas cooling cavity and the spraying and washing cavity and carries the smoke dust falls into the water seal box, sludge precipitation is carried out under the action of the inclined scraper, overflow liquid is discharged from the overflow port, and sludge is discharged from the sludge discharge port. The sludge is dehydrated, the solid phase returns to the fly ash ingredient, and the liquid phase returns to the lye pool to prepare lye for recycling.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An apparatus suitable for fly ash melting and flue gas cleaning processes, the apparatus comprising:

the double-chamber melting furnace (10) is characterized in that the inner cavity of the double-chamber melting furnace is divided into a main reaction chamber (11) and a secondary reaction chamber (12) which are horizontally communicated in sequence, a partition wall (13) is arranged between the main reaction chamber (11) and the secondary reaction chamber (12), and a communication channel for communicating the main reaction chamber (11) and the secondary reaction chamber (12) is arranged at the bottom of the partition wall (13); a main feeding port (101) is arranged at the top of the main reaction chamber (11) close to the partition wall (13), a first flue gas outlet (102) is also arranged at the top of the main reaction chamber (11), and a salt fishing port (103) is arranged at the side of the main reaction chamber; an auxiliary feeding port (104) is formed in the position, close to the partition wall (13), of the top of the auxiliary reaction chamber (12), a second flue gas outlet (105) and an electrode port (106) are further formed in the top of the auxiliary reaction chamber (12), the double-chamber melting furnace (10) further comprises a heating electrode (14), and the heating electrode (14) penetrates through the electrode port (106) and extends into the auxiliary reaction chamber (12);

the flue gas purification device (20) comprises a water seal tank (21), an alkali liquor pool (22), a flue gas cooling unit (23) and a multi-stage flue gas spraying and washing unit (24), wherein the flue gas cooling unit (23) and the flue gas spraying and washing unit (24) are both arranged at the top of the water seal tank (21); an overflow port (201) is arranged at the side part of the water seal tank (21), and a sludge discharge port (202) is arranged at the bottom part of the water seal tank; the flue gas cooling unit (23) is provided with a flue gas cooling cavity (231), the top of the flue gas cooling cavity (231) is provided with a cooling spraying unit, the flue gas cooling cavity (231) is further provided with a flue gas inlet (203) and a cooling flue gas outlet (204), the flue gas inlet (203) is communicated with the first flue gas outlet (102) and the second flue gas outlet (105), the top of the water seal box (21) is provided with a cooling water inlet, and the cooling water inlet is communicated with the bottom of the flue gas cooling cavity (231); according to the flowing direction of the flue gas, the flue gas spraying and washing units (24) at all levels are sequentially communicated and arranged at the downstream of the cooling flue gas outlet (204), each flue gas spraying and washing unit (24) is provided with a flue gas spraying and washing cavity (241), the top of each flue gas spraying and washing cavity (241) is provided with a washing and spraying unit, the top of the water seal box (21) is also provided with a washing water inlet, and the washing water inlet is communicated with the bottom of each flue gas spraying and washing cavity (241); the alkali liquor pool (22) is connected with both the cooling spraying unit and the washing spraying unit and is used for supplying alkali liquor.

2. The device for melting fly ash and purifying flue gas according to claim 1, wherein a heat supplementing port (107) is further provided on the side wall of the main reaction chamber (11) at a position lower than the salt scooping port (103), and the device further comprises a heat supplementing unit for supplementing heat to the main reaction chamber (11) through the heat supplementing port (107).

3. The apparatus for melting fly ash and purifying flue gas according to claim 2, wherein the heat-supplying unit is a heat-supplying electrode or a fuel spray gun.

4. The device for fly ash melting and flue gas cleaning treatment according to any of claims 1 to 3, wherein the ratio of the volumes of the main reaction chamber (11) and the secondary reaction chamber (12) in the dual-chamber melting furnace (10) is (1-2): 1.

5. The device for melting and flue gas cleaning treatment of fly ash according to claim 4, wherein the salt scooping port (103) is located on the side wall of the main reaction chamber (11) at a position higher than the bottom of the partition wall (13); the partition wall and the inner bottom wall of the double-chamber melting furnace (10) are provided with a space therebetween to form the communication channel.

6. An apparatus for melting and flue gas cleaning process of fly ash according to claim 5, wherein the distance between the bottom of the partition wall and the bottom wall inside the double chamber melting furnace (10) is denoted as h₁The total height of the partition wall is denoted by h₂Then 1/3 < h₁/ h₂＜1。

7. An apparatus for melting fly ash and purifying flue gas according to claim 5, wherein the partition wall (13) is a water-cooled partition wall or an air-cooled partition wall.

8. An apparatus for melting and flue gas cleaning process of fly ash according to claim 5, characterized in that the lower end of the heating electrode (14) is located lower than the bottom of the partition wall (13).

9. The device for melting and flue gas cleaning treatment of fly ash according to any of claims 1 to 3, wherein the device further comprises a vertical combustion chamber (15), the vertical combustion chamber (15) is respectively communicated with the first flue gas outlet (102), the second flue gas outlet (105) and the flue gas inlet (203), and the vertical combustion chamber (15) is used for performing combustion treatment on the flue gas discharged from the first flue gas outlet (102) and the second flue gas outlet (105).

10. The plant for the melting and flue gas purification treatment of fly ash according to claim 9, wherein the vertical combustion chamber (15) is arranged above the second flue gas outlet (105) and is vertically connected with the second flue gas outlet (105); and the top of the vertical combustion chamber (15) is also provided with an ash removal unit (16), and the ash removal unit (16) is used for performing ash removal treatment on the inner wall of the vertical combustion chamber (15).

11. The apparatus for melting and flue gas cleaning of fly ash according to any of claims 1 to 3, wherein the apparatus further comprises a dosing unit for dosing fly ash and flux, and the dosing unit is connected to the primary feed opening (101) via a first feed hopper (17) and to the secondary feed opening (104) via a second feed hopper (18).

12. The device suitable for fly ash melting and flue gas cleaning process according to any of claims 1 to 3, further comprising a salt fishing device, wherein the salt fishing device carries out salt fishing through the salt fishing port (103).

13. The device for fly ash melting and flue gas cleaning process according to any of claims 1 to 3, wherein the flue gas cooling unit (23) further comprises a cooling flue gas discharge pipe (232), one end of the cooling flue gas discharge pipe (232) is connected with the cooling flue gas outlet (204), and the other end is connected with the top of the water seal tank (21); wherein,

the cooling flue gas discharge pipeline (232) is a Venturi tube; or,

and a first induced draft device is arranged on the cooling flue gas discharge pipeline (232).

14. The apparatus for melting and flue gas cleaning process of fly ash according to claim 13, wherein the cooling flue gas discharge pipe (232) is a plurality of pipes arranged in parallel.

15. The device for melting and flue gas cleaning treatment of fly ash according to claim 13, wherein, in the multiple stages of flue gas spray washing units (24) arranged in series, the flue gas spray washing units (24) except the last stage further comprise a spray flue gas discharge pipeline (242), one end of the spray flue gas discharge pipeline (242) is connected with the flue gas spray washing chamber (241), and the other end is connected with the top of the water seal tank (21); wherein,

the spraying flue gas discharge pipeline (242) is a Venturi tube; or,

and a second air inducing device is arranged on the spraying smoke discharge pipeline (242).

16. The device for melting and flue gas cleaning treatment of fly ash according to claim 15, wherein the spraying flue gas discharging pipes (242) in each flue gas spraying washing unit (24) are arranged in parallel.

17. An apparatus for fly ash melting and flue gas cleaning process according to claim 15, wherein the last stage of the flue gas spray washing unit (24) further comprises a cleaned flue gas discharge pipe (243), and the cleaned flue gas discharge pipe (243) is connected with the flue gas spray washing chamber (241) of the last stage of the flue gas spray washing unit (24).

18. The device for melting and flue gas cleaning treatment of fly ash according to any of claims 1 to 3, characterized in that the overflow (201) is arranged at the side of the water seal tank (21) near the inner top wall.

19. The device for melting fly ash and purifying flue gas according to any of claims 1 to 3, wherein a sludge collecting unit (211) is disposed at the bottom inside the water sealed box (21), and the sludge collecting unit (211) is used for collecting the sludge deposited inside the water sealed box (21) and discharging the sludge through the sludge discharging port (202).

20. The apparatus for melting fly ash and purifying flue gas according to claim 19,

the mud collecting unit (211) is an inclined scraper, and the inclined scraper inclines downwards from a position far away from the mud discharging port (202) to a position close to the mud discharging port (202); or,

the mud collecting unit (211) is a screw conveyor.

21. The apparatus for melting and flue gas cleaning treatment of fly ash according to claim 19, further comprising a dewatering device (25), wherein said dewatering device (25) is in communication with said sludge discharge port (202).

22. An apparatus for melting fly ash and flue gas cleaning process according to claim 21, wherein the dewatering device (25) has a liquid phase outlet and a solid phase outlet, the liquid phase outlet being in communication with the lye pool (22).

23. The device for melting and flue gas cleaning treatment of fly ash according to any of claims 1 to 3, characterized in that the side of the secondary reaction chamber (12) away from the primary reaction chamber (11) is further provided with a slag discharge port; the slag discharge port comprises a bottom slag port (108) positioned at the lower part of the side wall of the secondary reaction chamber (12) and an upper slag port (109) positioned above the bottom slag port (108).

24. A method for melting and flue gas cleaning fly ash, which comprises the steps of using the device of any one of claims 1 to 23 to melt and flue gas cleaning fly ash, wherein:

step S1, mixing the fly ash and optional flux to form fly ash to be treated; firstly, feeding materials into a double-chamber melting furnace (10) through a main feed inlet (101) and/or an auxiliary feed inlet (104), and starting a heating electrode (14) to melt the fly ash to be treated and form a molten pool;

step S2, after a molten pool is formed, continuously feeding the fly ash to be treated into the molten pool of the main reaction chamber (11) through the main feed inlet (101) so as to melt the fly ash; in the melting treatment process, a molten pool in the secondary reaction chamber (12) is heated through the heating electrode (14), the temperature of the molten pool in the secondary reaction chamber (12) is controlled to be 1200-1400 ℃, and the temperature of a hearth above the molten pool in the secondary reaction chamber (12) is 700-1200 ℃; carrying out heat conduction heating on a molten pool in the main reaction chamber (11) through the molten pool in the auxiliary reaction chamber (12), and controlling the temperature of the molten pool in the main reaction chamber (11) to be 900-1200 ℃ and the temperature of a hearth above the molten pool in the main reaction chamber (11) to be 200-500 ℃; as the melting process progresses, forming a molten salt layer on the surface of a molten pool of the main reaction chamber (11), forming slag at the bottom of the double-chamber melting furnace (10), discharging flue gas generated in the main reaction chamber (11) from a first flue gas outlet (102), and discharging flue gas generated in the secondary reaction chamber (12) from a second flue gas outlet (105); fishing out the molten salt in the molten salt layer through a salt fishing port (103);

step S3, sending the flue gas discharged from the first flue gas outlet (102) and the second flue gas outlet (105) as the flue gas to be purified into a flue gas purification device (20) through a flue gas inlet (203) for flue gas purification treatment; firstly, introducing the flue gas to be purified into a flue gas cooling cavity (231), and supplying alkali liquor to a cooling spraying unit by using an alkali liquor pool (22) so as to cool the flue gas to be purified to form cooled flue gas and first spraying liquid; the cooled flue gas sequentially passes through a flue gas spraying and washing cavity (241) of a multi-stage flue gas spraying and washing unit (24), and the alkali liquor is supplied to each washing and spraying unit by using the alkali liquor pool (22) so as to sequentially carry out multi-stage spraying and washing on the cooled flue gas and form purified flue gas and second spraying liquor; enabling the first spraying liquid and the second spraying liquid to enter a water seal tank (21) for sludge precipitation to obtain overflow liquid and sludge; the overflow liquid is discharged through an overflow port (201), and the sludge is discharged through a sludge discharge port (202).

25. The method for melting and flue gas cleaning treatment of fly ash according to claim 24, wherein during the melting treatment of step S2, when the temperature of the molten bath in the main reaction chamber (11) decreases, the fly ash to be treated is supplemented by a heat supplementing unit from a heat supplementing port (107) and/or supplemented to the molten bath in the secondary reaction chamber (12) through the secondary feed port (104).

26. The method for melting fly ash and purifying flue gas as claimed in claim 25, wherein the process of performing heat compensation by the heat compensation unit comprises: supplementing heat to the molten pool of the main reaction chamber (11) through a heat supplementing electrode, or injecting fuel into the molten pool of the main reaction chamber (11) for supplementing heat; preferably, the fuel is natural gas and/or fuel oil.

27. The method for melting and flue gas cleaning treatment of fly ash according to any of claims 24 to 26, wherein during the melting treatment in step S2, the furnace pressure above the molten pool of the main reaction chamber (11) is controlled to be-100 Pa-0 Pa, and the furnace pressure above the molten pool of the secondary reaction chamber (12) is controlled to be-100 Pa-0 Pa.

28. The method for melting fly ash and flue gas cleaning process according to any of claims 24 to 26, wherein the step S3 further comprises, before the step of feeding the flue gas to be cleaned into the flue gas cleaning device (20) for the flue gas cleaning process: and (3) carrying out combustion treatment on the flue gas to be purified through a vertical combustion chamber (15).

29. The method for melting and flue gas cleaning treatment of fly ash according to claim 28, wherein the vertical combustion chamber (15) is arranged above the second flue gas outlet (105) and vertically connected to the second flue gas outlet (105); the method further comprises the following steps: and the inner wall of the vertical combustion chamber (15) is subjected to ash removal treatment by an ash removal unit (16) at the top of the vertical combustion chamber (15).

30. The method for melting and flue gas cleaning process of fly ash according to any of claims 24 to 26, wherein in step S3, after the flue gas to be cleaned is introduced into the flue gas cooling chamber (231) for cooling process, the cooled flue gas is sent to the top of the water-sealed tank (21) by using the cooled flue gas discharge pipe (232) and then enters the flue gas spray washing unit (24); when the cooling flue gas discharge pipeline (232) is a Venturi tube, the cooling flue gas enters the flue gas spraying and washing unit (24) through the top of the water seal box (21) by suction force; when the cooling flue gas discharging pipeline (232) is provided with a first induced air device, the cooling flue gas passes through the top of the water seal box (21) to enter the flue gas spraying and washing unit (24) through the induced air effect of the first induced air device.

31. The method for melting and flue gas cleaning treatment of fly ash according to claim 30, wherein in the step S3, during the cooling flue gas passes through the flue gas spraying washing chambers (241) of the multi-stage flue gas spraying washing unit (24) in sequence to perform the multi-stage spraying washing, the spraying flue gas formed by the flue gas spraying washing chamber (241) of the previous stage is sent to the top of the water seal tank (21) by using the spraying flue gas discharging pipeline (242), and then enters the flue gas spraying washing chamber (241) of the next stage; when the spray flue gas discharge pipeline (242) is a venturi tube, the spray flue gas formed by the flue gas spray washing cavity (241) of the previous stage passes through the top of the water seal box (21) by suction force and enters the flue gas spray washing cavity (241) of the next stage; when a second induced air device is arranged on the spraying smoke discharge pipeline (242), the spraying smoke which is formed by the smoke spraying washing cavity (241) of the previous stage passes through the top of the water seal box (21) and enters the next stage of the smoke spraying washing cavity (241) under the induced air action of the second induced air device.

32. The method for fly ash melting and flue gas cleaning process according to any of claims 24 to 26, further comprising: dehydrating the sludge by a dehydration device (25) to form a liquid phase and a solid phase; returning the solid phase to the step S1 for compounding; returning the liquid phase to the caustic bath (22).