Circulating fluidized bed fly ash heating furnace coupling fly ash melting device and method

Abstract

The invention discloses a circulating fluidized bed fly ash heating furnace coupled fly ash melting device and method, and belongs to the field of harmless and resourceful treatment of waste incineration fly ash. A smoke outlet of the circulating fluidized bed combustion chamber is communicated with a first efficient cyclone separator, a discharging port of the first efficient cyclone separator is communicated with a material return valve, an outlet in one side of the material return valve is communicated with the combustion chamber, and an outlet in the other side of the material return valve is communicated with the high-temperature melting furnace. A flue gas outlet of the efficient cyclone separator I is communicated with the secondary combustion chamber and the waste heat boiler I; a flue gas outlet of the high-temperature melting furnace is communicated with a waste heat boiler II; a flue gas outlet of the waste heat boiler II is communicated with an efficient cyclone separator II; smoke outlets of the first waste heat boiler and the second efficient cyclone separator are communicated with a quench tower, and a smoke outlet of the quench tower is communicated with a bag-type dust collector, the smoke cooling side of a smoke-smoke heater, a wet washing tower, the smoke heating side of the smoke-smoke heater, a steam-smoke heater, an SCR denitration device and a smoke inlet of an economizer. The device is used for high-temperature melting treatment of the fly ash.

Description

Technical Field

[0001] The invention belongs to the field of harmless and resourceful treatment of fly ash from garbage incineration, and particularly relates to a circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device and method. Background Art

[0002] According to statistics, the number of domestic waste incineration plants in China has exceeded 900 in 2023, with a waste incineration capacity of 861,800 tons per day, and 220 million tons of waste actually incinerated throughout the year. It is estimated that the amount of waste incineration will reach 240 million tons in 2024, and the output of fly ash from incineration accounts for 3-5% of the total amount of waste. At 4%, 9.6 million tons are generated each year. Incineration fly ash is the ash captured by the flue gas purification system of the waste incineration plant, including heavy metal elements (Pb, Zn, Cr, Ni, Cu, Cd, Hg, etc.), soluble salt substances (mainly chlorides of Ca, Na and K, accounting for 20-30% of the weight of fly ash) and dioxins (0.8-6.7ngTEQ / g) and other organic pollutants, which are hazardous wastes. At present, the main treatment method for fly ash is chelation pretreatment followed by landfill, but landfill occupies a large amount of land resources, has high construction investment, is difficult to operate and maintain, and still has great environmental risks. With the shortage of landfill land and increasing environmental protection requirements, the reduction, harmlessness and resource utilization of fly ash will become the hot spots and difficulties in the development of the industry.

[0003] At present, the fly ash disposal industry is promoting multiple fly ash disposal methods: including low-temperature thermal decomposition, high-temperature sintering and high-temperature melting. The first two methods are currently in the pilot stage and have the problem of incomplete treatment; high-temperature melting mostly uses electric melting (graphite electrode and plasma) methods. These methods have problems such as short life of refractory materials and plasma guns and high operating costs. The fly ash needs to be washed with water to remove chloride salts, dried and then electrothermally melted. According to reports, the operating cost is as high as 4,000 yuan per ton of fly ash. Therefore, it is necessary to adopt innovative fly ash high-temperature melting technology to solve the problem of refractory life and significantly reduce operating costs. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of short refractory life and high operating cost in the current high-temperature melting method for fly ash disposal, and to propose a circulating fluidized bed fly ash heating furnace coupled fly ash melting device and method.

[0005] Experimental studies have found that fly ash can reduce its weight by 20-25% when it is thermally decomposed at 900-1000°C, including some crystal water and volatile chloride salts (NaCl, KCl, PbCl2, ZnCl2, Fe2Cl3, etc.), and the fly ash aggregates into small particles after heating, with a particle size of 50-200μm. Therefore, it is proposed to first subject the fly ash to high-temperature heat treatment (relative to water washing dechlorination, this method is referred to as thermal dechlorination) to remove most of the chloride salts, and then enter the high-temperature melting furnace for treatment, which can greatly increase the life of the refractory material, thereby reducing the operating cost of fly ash disposal. To this end, a circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device and method is proposed. Laboratory verification has found that the life of the refractory material can be greatly increased. At the same time, the circulating fluidized bed and the melting furnace use biomass as auxiliary fuel, which greatly reduces the operating cost.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device, the melting device comprising a circulating fluidized bed, a return valve, a primary fan, a secondary combustion chamber, a high-temperature melting furnace, a quenching tower, a bag filter, a fly ash washing device, a flue gas-flue gas heater, a wet scrubber, a steam-flue gas heater, an SCR denitration device, an economizer, two high-efficiency cyclone separators and two waste heat boilers; the two high-efficiency cyclone separators are respectively a high-efficiency cyclone separator 1 and a high-efficiency cyclone separator 2, and the two waste heat boilers are respectively a waste heat boiler 1 and a waste heat boiler 2;

[0008] The side wall of the circulating fluidized bed is provided with a fly ash port, a biomass port, a conditioning agent port and a secondary air port, and the fly ash port, the biomass port, the conditioning agent port and the secondary air port are all corresponding to the circulating fluidized bed combustion chamber, and the primary fan outlet is connected to the wind chamber at the bottom of the circulating fluidized bed combustion chamber; the flue gas outlet at the top of the circulating fluidized bed combustion chamber is connected to the flue gas inlet of the high-efficiency cyclone separator one, and the discharge port at the lower end of the high-efficiency cyclone separator is connected to the return valve, and one side outlet of the return valve is connected to the return port of the circulating fluidized bed combustion chamber, and the other side outlet of the return valve is connected to the inlet of the high-temperature melting furnace through the high-temperature fly ash inlet pipe of the melting furnace; the flue gas outlet at the top of the high-efficiency cyclone separator one is connected to the secondary combustion chamber in sequence, and the secondary combustion chamber is connected to the high-efficiency cyclone separator one. The flue gas outlet of the high-temperature melting furnace is connected with the flue gas inlet of the waste heat boiler No. 2, and the flue gas outlet of the waste heat boiler No. 2 is connected with the high-efficiency cyclone separator No. 2; the flue gas outlet of the waste heat boiler No. 1 and the flue gas outlet of the high-efficiency cyclone separator No. 2 are both connected with the flue gas inlet of the quenching tower, and the flue gas outlet of the quenching tower is connected with the bag filter, the flue gas cooling side of the flue gas-flue gas heater, the wet scrubber, the flue gas heating side of the flue gas-flue gas heater, the steam-flue gas heater, the SCR denitrification device and the flue gas inlet of the economizer in sequence; the ash discharge port at the bottom of the quenching tower and the ash discharge port at the bottom of the bag filter are both connected with the ash inlet of the fly ash water washing device.

[0009] Furthermore, a regulating valve is installed at the outlet on the other side of the return valve.

[0010] Furthermore, the fly ash port on the side wall of the circulating fluidized bed combustion chamber is connected to the outlet of the fly ash bin through a screw feeder 1; the biomass port on the side wall of the circulating fluidized bed combustion chamber is connected to the outlet of the biomass bin through a screw feeder 2; the conditioning agent port on the side wall of the circulating fluidized bed combustion chamber is connected to the outlet of the conditioning agent bin through a screw feeder 3.

[0011] Furthermore, the high-temperature fly ash inlet pipe of the melting furnace is connected to the outlet of the biomass powder bin through a screw feeder 4.

[0012] Furthermore, the secondary air inlet on the side wall of the circulating fluidized bed combustion chamber is connected to the outlet of the secondary air fan.

[0013] Furthermore, the bottom end of the secondary air outlet is 3-5m away from the air distribution plate of the circulating fluidized bed.

[0014] A circulating fluidized bed fly ash heating furnace coupled fly ash melting method, the method comprising the following steps:

[0015] Step 1: primary air is introduced into the wind chamber at the bottom of the circulating fluidized bed combustion chamber. At the same time, fly ash, biomass and conditioning agent are respectively sent into the circulating fluidized bed combustion chamber for combustion. Secondary air is sent into the circulating fluidized bed from the secondary air port. The circulating fluidized bed is an insulated furnace. The temperature in the furnace reaches 900-1000°C. The high-temperature flue gas discharged through the flue gas outlet at the upper end of the circulating fluidized bed combustion chamber enters the high-efficiency cyclone separator 1. Urea or ammonia water is sprayed into the high-temperature flue gas before entering the high-efficiency cyclone separator 1 for SNCR denitrification; the high-efficiency cyclone separator 1 separates the fly ash carried in the high-temperature flue gas, and sends it into the circulating fluidized bed from the outlet on one side of the return valve at the bottom of the high-efficiency cyclone separator 1 to form a fly ash circulation. The outlet on the other side of the return valve sends part of the fly ash into the high-temperature melting furnace through a regulating valve. The burner 2 of the high-temperature melting furnace heats the fly ash entering the high-temperature melting furnace to 1300-1400°C to achieve fly ash melting;

[0016] Step 2: The high-temperature flue gas of 900-1000°C discharged from the flue gas outlet at the top of the high-efficiency cyclone separator 1 enters the secondary combustion chamber, and the flue gas temperature is heated to 1100°C under the combustion assistance of the burner 1 in the secondary combustion chamber, and the residence time is greater than 2s, and then enters the waste heat boiler 1, and the flue gas temperature drops to 500-550°C before entering the quenching tower;

[0017] Step 3: The flue gas discharged from the flue gas outlet of the high-temperature melting furnace enters the waste heat boiler 2, and urea or ammonia water is sprayed into the 1000-1050℃ area of ​​the waste heat boiler 2 for SNCR denitrification. After the flue gas is cooled to 500-550℃ in the waste heat boiler 2, it enters the high-efficiency cyclone separator 2, and the separated fly ash is sent back to the fly ash bin in front of the furnace. The clean flue gas enters the quenching tower from the upper outlet of the high-efficiency cyclone separator 2;

[0018] Step 4: The two flue gases converge in the quenching tower and are cooled to 200°C. They then enter the bag filter. Activated carbon is sprayed into the flue connecting the bag filter and the quenching tower to adsorb heavy metals and dioxins in the flue gas. The flue gas then enters the flue gas-flue gas heater, where the flue gas temperature drops to 105°C. The flue gas then enters the wet scrubber, where NaOH is used to neutralize HCl, SO2 and HF in the flue gas. The concentrated brine discharged from the bottom of the wet scrubber is used as cooling water for the quenching tower. The ash discharged from the lower part of the quenching tower merges with the ash captured by the bag filter and enters the fly ash washing device together to separate the impurities and fly ash. The fly ash is dried and then sent to the fly ash bin in front of the furnace. The 62°C clean flue gas discharged from the wet scrubber is heated to 157°C by the flue gas-flue gas heater, and then heated to 170-210°C by the steam-flue gas heater to enter the SCR denitrification device, and then cooled to 130-150°C by the economizer and discharged into the atmosphere.

[0019] Furthermore, in step 1, the mass ratio of the fly ash, biomass and conditioning agent is 100:20-30:20-30.

[0020] Furthermore, in step one, the burner two uses biomass powder as fuel, requiring the biomass powder to have a particle size less than 0.5 mm, a moisture content less than 10%, and a calorific value greater than 3500 Kcal / kg, and heats the fly ash entering the high-temperature melting furnace to 1300-1400°C to achieve fly ash melting.

[0021] The beneficial effects of the present invention relative to the prior art are:

[0022] The present invention adopts a circulating fluidized bed to heat fly ash to 900-1000°C, and uses biomass as auxiliary fuel, which significantly reduces the operating cost; due to the "hot washing" process, most of the volatile chloride salts in the fly ash enter the flue gas of the circulating fluidized bed, so that the chloride salt content in the fly ash entering the melting furnace is significantly reduced, thereby greatly slowing down the corrosion rate of the high-temperature melting furnace refractory material and significantly increasing the service life; the fly ash collected by the tail bag filter only accounts for about 30% of the original fly ash, and only this part of the fly ash needs to be washed with water (the obtained impurities are recovered, and the fly ash is then sent to the fly ash bin in front of the furnace), which greatly reduces the operating cost compared with the existing process (first washing all the fly ash with water); wet washing, bag dust removal and SNCR+SCR denitrification process are adopted to achieve ultra-low tail gas emissions (the SCR denitrification device reduces the NOx concentration in the flue gas to less than 50mg / Nm 3, O2 = 11%; with the previous bag dust removal and wet scrubbing, the NOx in the exhaust gas is ≤ 50mg / Nm 3 、SO2≤35mg / Nm 3 , Dust ≤10mg / Nm 3 , corresponding to O2=11%). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device according to the present invention.

[0024] Figure 1 The names and reference numerals of the components are as follows:

[0025] Circulating fluidized bed 1, high-efficiency cyclone separator 1 2, regulating valve 3, return valve 4, primary fan 5, secondary fan 6, fly ash bin 7-1, screw feeder 1 7-2, biomass bin 8-1, screw feeder 2 8-2, conditioning agent bin 9-1, screw feeder 3 9-2, SNCR port 1 10, burner 1 11, second combustion chamber 12, waste heat boiler 1 13, burner 2 14, high-temperature melting furnace 15, water quenching slag Machine 16, SNCR port 2 17, waste heat boiler 2 18, high-efficiency cyclone separator 2 19, quenching tower 20, bag filter 21, fly ash washing device 22, flue gas-flue gas heater 23, wet scrubber 24, steam-flue gas heater 25, SCR denitrification device 26, economizer 27, induced draft fan 28, melting furnace high-temperature fly ash inlet pipe 29, biomass powder bin 29-1, screw feeder 4 29-2. DETAILED DESCRIPTION

[0026] Specific implementation method 1: Figure 1 As shown, this embodiment discloses a circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device, wherein the melting device comprises a circulating fluidized bed 1, a return valve 4, a primary fan 5, a secondary combustion chamber 12, a high-temperature melting furnace 15, a quenching tower 20, a bag filter 21, a fly ash washing device 22, a flue gas-flue gas heater 23, a wet scrubber 24, a steam-flue gas heater 25, an SCR denitrification device 26, an economizer 27, two high-efficiency cyclone separators and two waste heat boilers; the two high-efficiency cyclone separators are respectively a high-efficiency cyclone separator 1 2 and a high-efficiency cyclone separator 2 19, and the two waste heat boilers are respectively a waste heat boiler 1 13 and a waste heat boiler 2 18;

[0027] The side wall of the circulating fluidized bed 1 is provided with a fly ash port, a biomass port, a conditioning agent port and a secondary air port, and the fly ash port, the biomass port, the conditioning agent port and the secondary air port are all corresponding to the combustion chamber of the circulating fluidized bed 1, and the outlet of the primary fan 5 is connected to the wind chamber at the bottom of the combustion chamber of the circulating fluidized bed 1; the flue gas outlet at the top of the combustion chamber of the circulating fluidized bed 1 is connected to the flue gas inlet of the high-efficiency cyclone separator 2, and the discharge port at the lower end of the high-efficiency cyclone separator 2 is connected to the return valve 4, and the outlet on one side of the return valve 4 is connected to the return port of the combustion chamber of the circulating fluidized bed 1, and the outlet on the other side of the return valve 4 is connected to the inlet of the high-temperature melting furnace 15 through the high-temperature fly ash inlet pipe 29 of the melting furnace; the flue gas outlet at the top of the high-efficiency cyclone separator 2 is connected to the inlet of the secondary combustion chamber 12 and the waste heat boiler 13 in turn. The flue gas outlet of the high-temperature melting furnace 15 is connected with the flue gas inlet of the waste heat boiler 18, and the flue gas outlet of the waste heat boiler 18 is connected with the high-efficiency cyclone separator 19; the flue gas outlet of the waste heat boiler 13 and the flue gas outlet of the high-efficiency cyclone separator 19 are both connected with the flue gas inlet of the quenching tower 20, and the flue gas outlet of the quenching tower 20 is connected with the bag filter 21, the flue gas cooling side of the flue gas-flue gas heater 23, the wet scrubber 24, the flue gas heating side of the flue gas-flue gas heater 23, the steam-flue gas heater (SGH) 25, the SCR denitrification device 26 and the flue gas inlet of the economizer 27 in sequence; the ash discharge port at the lower part of the quenching tower 20 and the ash discharge port at the lower part of the bag filter 21 are both connected with the ash inlet of the fly ash washing device 22.

[0028] Furthermore, a regulating valve 3 is installed at the outlet on the other side of the return valve 4 to adjust the amount of fly ash entering the high-temperature melting furnace 15 .

[0029] Furthermore, the fly ash port on the side wall of the combustion chamber of the circulating fluidized bed 1 is connected to the outlet of the fly ash bin 7-1 through a screw feeder 7-2; the biomass port on the side wall of the combustion chamber of the circulating fluidized bed 1 is connected to the outlet of the biomass bin 8-1 through a screw feeder 8-2; the tempering agent port on the side wall of the combustion chamber of the circulating fluidized bed 1 is connected to the outlet of the tempering agent bin 9-1 through a screw feeder 9-2.

[0030] Furthermore, the high-temperature fly ash inlet pipe 29 of the melting furnace is connected to the outlet of the biomass powder bin 29-1 through the screw feeder 29-2 (the biomass powder is sent into the high-temperature fly ash inlet pipe 29 of the melting furnace, and the biomass powder is violently pyrolyzed under the heating of the high-temperature fly ash to produce a large amount of combustible gas, which enters the burner 2 14 of the high-temperature melting furnace 15).

[0031] Furthermore, the secondary air inlet on the side wall of the combustion chamber of the circulating fluidized bed 1 is connected to the outlet of the secondary air fan 6 .

[0032] Furthermore, the bottom end of the secondary air outlet is 3-5 m away from the air distribution plate of the circulating fluidized bed 1 .

[0033] Specific implementation method 2: Figure 1 As shown, this embodiment discloses a method for coupling fly ash melting with a circulating fluidized bed fly ash heating furnace, which is implemented by using the circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device described in the first embodiment; the method comprises the following steps:

[0034] Step 1: primary air (accounting for 50-70% of the total air volume) is introduced into the wind chamber at the bottom of the combustion chamber of the circulating fluidized bed 1. At the same time, fly ash, biomass and conditioning agent (rich in silicon and aluminum minerals) are respectively (through screw feeder 1 7-2, screw feeder 2 8-2 and screw feeder 3 9-2) sent into the combustion chamber of the circulating fluidized bed 1 for combustion, and secondary air (accounting for 30-50% of the total air volume) is sent into the circulating fluidized bed 1 from the secondary air port. The circulating fluidized bed 1 is an insulated furnace, and the temperature in the furnace reaches 900-1000°C. The high-temperature flue gas discharged from the flue gas outlet at the upper end of the combustion chamber of the circulating fluidized bed 1 enters the high-efficiency cyclone separator 2. Before entering the high-efficiency cyclone separator 2, urea or ammonia water is sprayed into the high-temperature flue gas for SNCR denitrification (the flue gas outlet at the upper end of the combustion chamber An SNCR port 10 is provided on the side wall of the port, and urea or ammonia water is sprayed into the high-temperature flue gas through the SNCR port 10 for SNCR denitrification, which can remove 70-80% of NOx); the high-efficiency cyclone separator 2 separates the fly ash carried in the high-temperature flue gas, and sends it to the circulating fluidized bed 1 from the outlet on one side of the return valve 4 at the bottom of the high-efficiency cyclone separator 2 to form a fly ash circulation, and the outlet on the other side of the return valve 4 sends part of the fly ash to the high-temperature melting furnace 15 through the regulating valve 3, and the burner 2 14 of the high-temperature melting furnace 15 (using biomass powder as fuel, requiring the biomass powder particle size to be less than 0.5mm, the moisture content to be less than 10%, and the calorific value to be greater than 3500Kcal / kg) heats the fly ash entering the high-temperature melting furnace 15 to 1300-1400°C to achieve fly ash melting;

[0035] The purpose of using the circulating fluidized bed 1 is to make the fly ash stay in the furnace for 3-5 minutes, so that most of the chloride salts in the fly ash can be volatilized; while the bubbling fluidized bed has a residence time of only 3-5 seconds, which cannot achieve this goal;

[0036] Step 2: The high-temperature flue gas of 900-1000°C discharged from the flue gas outlet at the top of the high-efficiency cyclone separator 2 enters the secondary combustion chamber 12, and the flue gas temperature is heated to 1100°C under the combustion assistance of the burner 11 (using light oil or natural gas as fuel) of the secondary combustion chamber 12, and the residence time is greater than 2s (to eliminate dioxins that may exist in the flue gas), and then enters the waste heat boiler 13, and the flue gas temperature drops to 500-550°C before entering the quenching tower 20;

[0037] Step 3: The flue gas discharged from the flue gas outlet of the high-temperature melting furnace 15 enters the waste heat boiler 18, and urea or ammonia water is sprayed into the 1000-1050°C region of the waste heat boiler 18 for SNCR denitrification (the side wall of the waste heat boiler 18 is provided with an SNCR port 17, and urea or ammonia water is sprayed into the 1000-1050°C region of the waste heat boiler 18 through the SNCR port 17, which can remove 40-50% of NOx). After the flue gas is cooled to 500-550°C in the waste heat boiler 18, it enters the high-efficiency cyclone separator 19, and the separated fly ash is sent back to the fly ash bin 7-1 in front of the furnace, and the clean flue gas enters the quenching tower 20 from the upper outlet of the high-efficiency cyclone separator 19;

[0038] The high-temperature molten slag discharged from the high-temperature melting furnace 15 is discharged after being cooled by water quenching by a water quenching slag discharger 16 .

[0039] Step 4: The two flue gases merge in the quench tower 20 and cool down to 200°C (the flue gas temperature drops to 200°C after spraying water for quenching, and the dioxins are controlled to be resynthesized between 200-500°C), and then enter the bag filter 21, and activated carbon is sprayed into the flue connecting the bag filter 21 and the quench tower 20 to adsorb heavy metals and dioxins in the flue gas, and then enter the flue gas-flue gas heater 23, and the flue gas temperature drops to 105°C, and then the flue gas enters the wet scrubber 24, and NaOH is used to neutralize HCl, SO2 and HF in the flue gas, and the concentrated brine (i.e., the salt-containing concentrated waste) discharged from the bottom of the wet scrubber 24 is used to remove the HCl, SO2 and HF in the flue gas. Water) is used as cooling water for the quenching tower 20. The ash discharged from the lower part of the quenching tower 20 is combined with the ash captured by the bag filter 21, and enters the fly ash washing device 22 (mature technology) together to separate the impurities and fly ash. The fly ash is dried and then sent to the fly ash bin 7-1 in front of the furnace; the clean flue gas (62°C) discharged from the wet scrubbing tower 24 is heated to 157°C by the flue gas-flue gas heater 23, and then heated to 170-210°C by the steam-flue gas heater 25, and enters the SCR denitrification device 26 (existing mature technology), and then is cooled to 130-150°C by the economizer 27 (via the induced draft fan 28) and discharged into the atmosphere.

[0040] Furthermore, in step 1, the mass ratio of the fly ash, biomass and conditioning agent is 100:20-30:20-30.

[0041] Biomass mainly refers to biomass molded fuel (calorific value greater than or equal to 3500Kcal / kg), and the conditioning agent is existing products such as SiO2, Al2O3, kaolin, bauxite, fly ash and a combination of these materials.

[0042] Furthermore, in step one, the burner 2 14 uses biomass powder as fuel, and requires that the biomass powder has a particle size less than 0.5 mm, a moisture content less than 10%, and a calorific value greater than 3500 Kcal / kg, and heats the fly ash entering the high-temperature melting furnace 15 to 1300-1400° C. to achieve fly ash melting.

[0043] The present invention uses biomass as auxiliary fuel, heats fly ash to 900-1000°C in a circulating fluidized bed 1, removes 20-25% of crystal water and volatile chloride salts, and then sends the "hot-washed" fly ash to a high-temperature melting furnace 15 through a high-efficiency cyclone separator 2 and heats it to 1300-1400°C with biomass powder as auxiliary fuel to achieve fly ash melting. Since most of the chloride salts have been "hot-washed", the refractory corrosion of the high-temperature melting furnace 15 is greatly reduced, and the service life can reach more than 2 years, which is much higher than the current life of the electric melting furnace (6 months).

[0044] In the present invention, in addition to using biomass as auxiliary fuel, light oil, natural gas, coal or lignite etc. can also be selected as auxiliary fuel according to local environmental protection requirements.

[0045] The equipment used in the present invention is all existing equipment.

[0046] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device, characterized in that: The melting device comprises a circulating fluidized bed (1), a return valve (4), a primary fan (5), a secondary combustion chamber (12), a high-temperature melting furnace (15), a quenching tower (20), a bag filter (21), a fly ash washing device (22), a flue gas-flue gas heater (23), a wet scrubber (24), a steam-flue gas heater (25), an SCR denitration device (26), an economizer (27), two high-efficiency cyclone separators and two waste heat boilers; the two high-efficiency cyclone separators are respectively a high-efficiency cyclone separator 1 (2) and a high-efficiency cyclone separator 2 (19), and the two waste heat boilers are respectively a waste heat boiler 1 (13) and a waste heat boiler 2 (18); The side wall of the circulating fluidized bed (1) is provided with a fly ash port, a biomass port, a conditioning agent port and a secondary air port, and the fly ash port, the biomass port, the conditioning agent port and the secondary air port all correspond to the combustion chamber of the circulating fluidized bed (1), and the outlet of the primary fan (5) is connected to the wind chamber at the bottom of the combustion chamber of the circulating fluidized bed (1); the flue gas outlet at the top of the combustion chamber of the circulating fluidized bed (1) is connected to the flue gas inlet of the high-efficiency cyclone separator (2), and the discharge port at the lower end of the high-efficiency cyclone separator (2) is connected to the return valve (4), and one side outlet of the return valve (4) is connected to the return port of the combustion chamber of the circulating fluidized bed (1), and the other side outlet of the return valve (4) is connected to the inlet of the high-temperature melting furnace (15) through the high-temperature fly ash inlet pipe (29) of the melting furnace; the flue gas outlet at the top of the high-efficiency cyclone separator (2) is connected to the inlet of the secondary combustion chamber (12) and the waste heat boiler (13) in sequence. The flue gas outlet of the high-temperature melting furnace (15) is connected to the flue gas inlet of the second waste heat boiler (18), and the flue gas outlet of the second waste heat boiler (18) is connected to the second high-efficiency cyclone separator (19); the flue gas outlet of the first waste heat boiler (13) and the flue gas outlet of the second high-efficiency cyclone separator (19) are both connected to the flue gas inlet of the quenching tower (20), and the flue gas outlet of the quenching tower (20) is sequentially connected to the bag filter (21), the flue gas cooling side of the flue gas-flue gas heater (23), the wet scrubbing tower (24), the flue gas heating side of the flue gas-flue gas heater (23), the steam-flue gas heater (25), the SCR denitrification device (26) and the flue gas inlet of the economizer (27); the ash discharge port at the bottom of the quenching tower (20) and the ash discharge port at the bottom of the bag filter (21) are both connected to the ash inlet of the fly ash washing device (22).

2. A circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device according to claim 1, characterized in that: A regulating valve (3) is installed at the outlet on the other side of the return valve (4).

3. A circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device according to claim 2, characterized in that: The fly ash port on the side wall of the combustion chamber of the circulating fluidized bed (1) is connected to the outlet of the fly ash bin (7-1) through a first screw feeder (7-2); the biomass port on the side wall of the combustion chamber of the circulating fluidized bed (1) is connected to the outlet of the biomass bin (8-1) through a second screw feeder (8-2); and the conditioning agent port on the side wall of the combustion chamber of the circulating fluidized bed (1) is connected to the outlet of the conditioning agent bin (9-1) through a third screw feeder (9-2).

4. The circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device according to claim 2, characterized in that: The high-temperature fly ash inlet pipe (29) of the melting furnace is connected to the outlet of the biomass powder bin (29-1) through a screw feeder four (29-2).

5. The circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device according to claim 3, characterized in that: The secondary air port on the side wall of the combustion chamber of the circulating fluidized bed (1) is connected to the outlet of the secondary air fan (6).

6. The circulating fluidized bed fly ash heating furnace coupled with a fly ash melting device according to claim 5, characterized in that: The bottom end of the secondary air outlet is 3-5 m away from the air distribution plate of the circulating fluidized bed (1).

7. A circulating fluidized bed fly ash heating furnace coupled fly ash melting method, characterized in that: The method is implemented by using the circulating fluidized bed fly ash heating furnace coupled with the fly ash melting device as described in any one of claims 3 to 6; the method comprises the following steps: Step 1: primary air is introduced into the wind chamber at the bottom of the combustion chamber of the circulating fluidized bed (1). At the same time, fly ash, biomass and conditioning agent are respectively introduced into the combustion chamber of the circulating fluidized bed (1) for combustion. Secondary air is introduced into the circulating fluidized bed (1) from the secondary air port. The circulating fluidized bed (1) is an insulated furnace. The temperature in the furnace reaches 900-1000°C. The high-temperature flue gas discharged from the flue gas outlet at the upper end of the combustion chamber of the circulating fluidized bed (1) enters the high-efficiency cyclone separator (2). Urine is sprayed into the high-temperature flue gas before entering the high-efficiency cyclone separator (2). SNCR denitrification is performed by using a high-efficiency cyclone separator (1) to separate the fly ash carried in the high-temperature flue gas and to feed the fly ash to a circulating fluidized bed (1) from an outlet on one side of a return valve (4) at the bottom of the high-efficiency cyclone separator (1) to form a fly ash circulation. A portion of the fly ash is fed to a high-temperature melting furnace (15) through an adjusting valve (3) from an outlet on the other side of the return valve (4). A burner (14) of the high-temperature melting furnace (15) heats the fly ash entering the high-temperature melting furnace (15) to 1300-1400°C to achieve fly ash melting. Step 2: The high-temperature flue gas of 900-1000° C. discharged from the flue gas outlet at the top of the high-efficiency cyclone separator 1 (2) enters the secondary combustion chamber (12), and the flue gas temperature is heated to 1100° C. under the combustion assistance of the burner 1 (11) of the secondary combustion chamber (12), and the residence time is greater than 2 seconds, and then enters the waste heat boiler 1 (13), and the flue gas temperature drops to 500-550° C. and then enters the quenching tower (20); Step 3: The flue gas discharged from the flue gas outlet of the high-temperature melting furnace (15) enters the waste heat boiler (18), and urea or ammonia water is sprayed into the 1000-1050°C region of the waste heat boiler (18) to perform SNCR denitration. After the flue gas is cooled to 500-550°C in the waste heat boiler (18), it enters the high-efficiency cyclone separator (19), and the separated fly ash is sent back to the fly ash bin (7-1) in front of the furnace. The clean flue gas enters the quenching tower (20) from the upper outlet of the high-efficiency cyclone separator (19); Step 4: The two flue gases converge in the quench tower (20) and are cooled to 200°C. The flue gases then enter the bag filter (21). Activated carbon is sprayed into the flue gas duct connecting the bag filter (21) and the quench tower (20) to adsorb heavy metals and dioxins in the flue gas. The flue gas then enters the flue gas heater (23). The flue gas temperature drops to 105°C. The flue gas then enters the wet scrubber (24). NaOH is used to neutralize HCl, SO2 and HF in the flue gas. The concentrated brine discharged from the bottom of the wet scrubber (24) is used as the quench tower (20). The ash discharged from the lower part of the quench tower (20) is combined with the ash collected by the bag filter (21) and enters the fly ash washing device (22) to separate the impurities and fly ash. The fly ash is dried and then sent to the fly ash bin (7-1) in front of the furnace; the clean flue gas discharged from the wet scrubber (24) is heated to 157°C by the flue gas-flue gas heater (23), and then heated to 170-210°C by the steam-flue gas heater (25) and enters the SCR denitrification device (26), and then is cooled to 130-150°C by the economizer (27) and discharged into the atmosphere.

8. The method for coupling fly ash melting with a circulating fluidized bed fly ash heating furnace according to claim 7, characterized in that: In step 1, the mass ratio of the fly ash, biomass and conditioning agent is 100:20-30:20-30.

9. The method for coupling fly ash melting with a circulating fluidized bed fly ash heating furnace according to claim 7, characterized in that: In step one, the burner 2 (14) uses biomass powder as fuel, and the biomass powder particle size is required to be less than 0.5mm, the moisture content is less than 10%, and the calorific value is greater than 3500Kcal / kg, and the fly ash entering the high-temperature melting furnace (15) is heated to 1300-1400°C to achieve fly ash melting.

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