Fly ash dioxin removal system and method

Abstract

The invention discloses a fly ash dioxin removal system and method, relates to the technical field of fly ash treatment, and solves the problems that in the process of removing dioxin in fly ash, the removal efficiency is low, the process is tedious and the cost is high. The system comprises an induced air pipe, a gas-powder mixer, a gas-powder separation assembly, a secondary air pipe, a first temperature sensor installed in the induced air pipe, a fan, a second temperature sensor, a particulate matter detector and a controller, and the fan, the second temperature sensor and the particulate matter detector are installed in the second air pipe. And then the dioxin mixed air obtained after desorption is returned to the furnace for high-temperature oxidation, an existing waste incineration technology is ingeniously applied, online production conditions are fully utilized, no secondary large energy investment exists, and therefore the cost is effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of fly ash treatment, and in particular to a fly ash dioxin removal system and method. Background Art

[0002] Fly ash is generally a substance with various polluting components collected by bag filters after a high-temperature incineration process and a series of treatments. The source industries include garbage incineration, hazardous waste incineration, etc. For example, in the garbage incineration industry: high concentrations of organic and inorganic pollutants are adsorbed from the flue gas, especially fly ash contains strong carcinogenic, teratogenic, mutagenic dioxins and heavy metals. If they are not properly treated, they will be transmitted from the emission source through the atmosphere, rainwater, etc. to various places, polluting the atmosphere and water sources, entering the food chain, and causing harm to people. Therefore, achieving harmless disposal and resource utilization of fly ash is one of the environmental protection issues that need to be solved urgently.

[0003] At present, the disposal technologies of dioxins in fly ash mainly include solidification landfill, biodegradation, chemical removal, low-temperature pyrolysis and high-temperature disposal. Among them, solidification landfill may become a potential source of dioxin pollution in landfills; biodegradation and low-temperature pyrolysis have the advantages of environmental friendliness and low cost, but the degradation efficiency of dioxins is not high; chemical removal has the advantages of low energy consumption and high efficiency, but there is a problem of secondary pollution. The coordinated disposal of fly ash by cement kilns is the current mainstream technology for high-temperature disposal. In order to strictly control the chlorine content, the doping amount of fly ash is very low, so cement kilns can only achieve resource utilization of limited fly ash.

[0004] In addition, water washing treatment is also common, but the removal of dioxins in this process is relatively low. Studies have found that the toxic equivalent of 2,3,7,8-TCDD in ash washing wastewater is the highest, accounting for 33.93% of the total toxic equivalent of ash washing wastewater. The migration rate from raw ash to ash washing wastewater is only 0.26%, and dioxins cannot be effectively removed by this method.

[0005] Existing dioxin removal processes often require the use of equipment for high-temperature desorption and re-oxidation, or the use of inert gas for high-temperature desorption, both of which require the introduction of third-party equipment and processes. The process is cumbersome and difficult to operate, increasing the cost of dioxin removal and treatment.

[0006] For example, the patent "Medium-temperature desorption combined with high-temperature plasma oxidation to destroy dioxin compounds" with publication number TW200736549A uses a temperature between 450-850℃ for desorption, and then the desorbed gas enters a high-temperature plasma oxidation chamber at least 1200℃ to use a plasma torch to oxidize and destroy dioxin compounds in the gas flow, i.e., a plasma torch process. Then, it is discharged after being connected to a quenching tower, a lime reaction tower, an activated carbon injection device, and a filter bag dust collector. Summary of the invention

[0007] The purpose of the present application is to overcome the problems of low removal efficiency, complicated process and high cost in the process of removing dioxins from fly ash in the prior art, and to provide a fly ash dioxin removal system and method.

[0008] In a first aspect, a fly ash dioxin removal system is provided, comprising an induced draft duct with a temperature regulating component, wherein one end of the induced draft duct is used to connect to an incineration system, the other end of the induced draft duct is connected to a gas-powder mixer, an ash inlet is preset at one end of the induced draft duct close to the gas-powder mixer, an output end of the gas-powder mixer is connected to a gas-powder separation component, a gas output end of the gas-powder separation component is connected to a secondary air duct of an incinerator through a second air duct, a first temperature sensor is installed in the induced draft duct, a fan, a second temperature sensor and a particle detector are installed in the second air duct, and the first temperature sensor, the fan, the second temperature sensor and the particle detector are all electrically connected to a controller.

[0009] In some possible implementations, the incineration system includes an incinerator, a primary waste heat recovery device and a secondary waste heat recovery device, the induced draft duct includes a first air duct, one end of the first air duct is connected to the gas-powder mixer, the other end of the first air duct is connected to a first branch air duct and a second branch air duct, the first branch air duct is used to connect the pipeline between the incinerator and the primary waste heat recovery device, the second branch air duct is used to connect the pipeline between the primary waste heat recovery device and the secondary waste heat recovery device, the temperature control component includes a first air valve and a second air valve, the first air valve is installed on the first branch air duct, and the second air valve is installed on the second branch air duct.

[0010] In some possible implementations, the first air valve and the second air valve are both electrically controlled valves, and the first air valve and the second air valve are both electrically connected to a controller.

[0011] In some possible implementations, the ash inlet is connected to an output end of a star-shaped feeder, an input end of the star-shaped feeder is used to connect to an ash source, and the star-shaped feeder is electrically connected to a controller.

[0012] In some possible implementations, the gas-powder separation assembly includes a first gas-powder separator and a second gas-powder separator, the input end of the first gas-powder separator is connected to the output end of the gas-powder mixer, the input end of the second gas-powder separator is connected to the gas output end of the first gas-powder separator, and the gas output end of the second gas-powder separator is connected to the air mixing chamber through a second air duct.

[0013] In some possible implementations, one end of the second air duct away from the gas-powder separation component is connected to one of the input ends of the air mixing chamber, the other input end of the air mixing chamber is used to connect to the slag storage, and the output end of the air mixing chamber is connected to the incinerator.

[0014] In a second aspect, a method for removing dioxins from fly ash is provided, which is applied to the system described in the first aspect, and the method comprises:

[0015] Start the fan, adjust the opening of the first air valve and the second air valve according to the detection data of the first temperature sensor, and adjust the temperature of the mixture sent to the air-powder mixer to 650°C-750°C;

[0016] Start the star feeder and adjust the parameters of the gas-powder separation component according to the detection data of the particle detector so that the gas output by the gas-powder separation component carries a preset amount of fly ash;

[0017] The openings of the first valve and the second valve are adjusted according to the detection data of the second temperature sensor, so that the temperature of the mixture in the second air duct is adjusted to not less than 550°C.

[0018] In some possible implementations, the amount of fly ash carried in the gas output by the gas-powder separation component is 5%-10% of the original fly ash amount.

[0019] In some possible implementations, the air volume in the first air duct is 1000m 3 / h-2000m 3 / h, the ash delivery rate of the star feeder is 1.2t / h-1.6t / h.

[0020] In some possible implementations, the residence time of the mixture of hot air and fly ash in the first air duct in the air-powder mixer is 10s-30s.

[0021] This application has the following beneficial effects:

[0022] 1. The system of the present application can be organically combined with the existing waste incineration system, and the high-temperature flue gas of the incinerator in the existing waste incineration process is used to desorb dioxins in the fly ash, and then the desorbed dioxins are mixed with air and returned to the furnace for high-temperature oxidation. The existing waste incineration process is cleverly used, and the online production conditions are fully utilized. There is no secondary large energy input, thereby effectively reducing the cost;

[0023] 2. The method of the present application can automatically control the corresponding valve opening and the ash delivery rate of the star feeder according to the detection data of the first temperature sensor, the second temperature sensor and the particle detector, thereby realizing the automatic control of the fly ash dioxin removal system, greatly simplifying the control process, and at the same time controlling the desorption temperature of the fly ash within the range of 650°C-750°C to effectively ensure the desorption rate of dioxins in the fly ash, thereby improving the removal efficiency of dioxins in the fly ash, and being able to transport most of the dioxins that are not completely desorbed back to the incinerator through the second air duct with an internal temperature of not less than 550°C, effectively avoiding the regeneration of dioxins and eliminating secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 is a structural block diagram of a fly ash dioxin removal system according to Example 1 of the present application;

[0027] Figure 2 It is the structural diagram of the existing waste incineration system;

[0028] Figure 3 is a circuit block diagram of the fly ash dioxin removal system of Example 1 of the present application;

[0029] Figure 4 It is a model diagram of type I adsorption isotherm of dioxins in fly ash;

[0030] Figure 5 It is the type I adsorption isobar model diagram of dioxins in fly ash;

[0031] Figure 6 This is a flow chart of the fly ash dioxin removal method of Example 2 of the present application.

[0032] Reference numerals:

[0033] 1. Temperature control component; 101. First air valve; 102. Second air valve; 2. Air duct; 201. First branch air duct; 202. Second branch air duct; 203. First air duct; 3. Incineration system; 301. Incinerator; 302. Secondary air duct; 303. Primary waste heat recovery equipment; 304. Secondary waste heat recovery equipment; 305. Slag storage; 306. Garbage pit; 307. Primary air duct; 308. Exhaust pre-treatment equipment; 309. Cloth Bag filter; 310, transfer ash bin; 311, exhaust gas post-treatment equipment; 312, exhaust chimney; 313, ash bin; 4, air-powder mixer; 5, ash inlet; 6, air-powder separation component; 601, first air-powder separator; 602, second air-powder separator; 7, second air duct; 8, first temperature sensor; 9, fan; 10, second temperature sensor; 11, particle detector; 12, star feeder; 13, air mixing chamber; 14, controller. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 2 As shown, the incineration system 3 includes an incinerator 301, a secondary air duct 302, a primary waste heat recovery device 303, a secondary waste heat recovery device 304, a slag storage 305, a garbage pit 306, a primary air duct 307, an exhaust gas pre-treatment device 308, a bag filter 309, an exhaust gas post-treatment device 311 and an exhaust pipe 312. The existing garbage incineration process is generally as follows: the garbage to be incinerated is usually stored in the garbage pit 306, the garbage is transported to the incinerator 301 for incineration, the primary waste heat recovery device 303 is used to recover the heat in the flue gas, and the secondary waste heat recovery device 304 is used to recover the heat in the flue gas. Secondary recovery is carried out, the slag is transported to the slag bin 305 for storage, the flue gas is treated by the exhaust gas pre-treatment equipment 308 and then enters the bag filter 309 to filter out the solid particles in the flue gas. These solid particles are called fly ash, and the gas is discharged into the atmosphere through the exhaust pipe 312 after the exhaust gas post-treatment equipment 311. In order to prevent the waste gas in the garbage pit 306 and the slag bin 305 from polluting the environment, the waste needs to be introduced into the incinerator 301 through the primary air duct 307 and the secondary air duct 302 respectively. On the one hand, it provides the incinerator 301 with the oxygen required for combustion, and on the other hand, it avoids the waste from polluting the surrounding environment.

[0037] It should be noted that the oxygen content of the flue gas after the incinerator 301 is low, about 6%, creating a relatively inert environment, which is conducive to the desorption of dioxins in fly ash. The adsorption of dioxins in fly ash meets the following conditions: Figure 4 The type I adsorption isotherm model shown in Figure 2 is converted to the adsorption isobaric line. Figure 5 As shown, the higher the temperature, the lower the adsorption amount of dioxins in fly ash. Therefore, the desorption of dioxins in fly ash can be achieved by increasing the ambient temperature of fly ash and reducing the oxygen content in the environment to reduce the adsorption amount of dioxins in fly ash.

[0038] like Figure 1As shown, a fly ash dioxin removal system involved in Example 1 of the present application includes an induced draft duct 2 with a temperature regulating component 1, wherein the induced draft duct 2 includes a first air duct 203, one end of the first air duct 203 is connected to the gas-powder mixer 4, and the other end of the first air duct 203 is connected to a first branch air duct 201 and a second branch air duct 202, the first branch air duct 201 is used to connect the pipeline between the incinerator 301 and the first-level waste heat recovery equipment 303, and the second branch air duct 202 is used to connect the pipeline between the first-level waste heat recovery equipment 303 and the second-level waste heat recovery equipment 304, and the temperature regulating component 1 includes a first branch air duct 201 and a second branch air duct 202. There is a first air valve 101 and a second air valve 102, wherein the first air valve 101 is installed on the first branch air duct 201, and the second air valve 102 is installed on the second branch air duct 202. The high-temperature flue gas is drawn out from the incinerator 301 through the first branch air duct 201. Generally, the temperature in the incinerator 301 is about 900°C-1050°C. The medium-temperature flue gas is drawn out from the primary waste heat recovery device 303 through the second branch air duct 202. Generally, the temperature of the flue gas treated by the primary waste heat recovery device 303 is about 200°C-700°C. By adjusting the opening of the first valve and the second valve, the high-temperature flue gas and the medium-temperature flue gas can be adjusted. The temperature of the introduced flue gas is regulated by the ratio of the high temperature flue gas to the low temperature flue gas. The other end of the induced draft duct 2 is connected to a gas-powder mixer 4. An ash inlet 5 is preset at one end of the induced draft duct 2 close to the gas-powder mixer 4, wherein the ash inlet 5 is used to introduce fly ash, so that the fly ash is premixed with the flue gas introduced from the incineration system 3 in the first air pipe, and the premixed flue gas and fly ash are fully mixed in the gas-powder mixer 4, and the high temperature of the flue gas is used to realize the desorption of dioxins in the fly ash. The output end of the gas-powder mixer 4 is connected to a gas-powder separation component 6, and the dioxins in the fly ash are separated from the particulate fly ash in the gas-powder separation component 6 after desorption. The gas output end of the powder separation component 6 is connected to the secondary air duct 302 of the incinerator 301 through the second air duct 7. The desorbed dioxins flow back to the incinerator 301 from the second air duct 7 along with the gas, and are oxidized again at high temperature in the incinerator 301 to achieve the effect of removing dioxins. At the same time, when the gas-powder separation component 6 performs gas-powder separation, a small amount of fly ash cannot be completely separated, so that a small amount of fly ash is mixed with dioxins and gas and flows back to the incinerator 301 along the second air duct. The induced draft duct 2 is equipped with a first temperature sensor 8, and the second air duct 7 is equipped with a fan 9, a second temperature sensor 10 and a particle detector 11. Figure 3As shown, the first gas-powder separator 601, the second gas-powder separator 602, the first temperature sensor 8, the fan 9, the second temperature sensor 10 and the particle detector 11 are all electrically connected to the controller 14, wherein the first temperature sensor 8 is installed in the first air pipe, and is used to detect the temperature of the flue gas introduced from the incineration system 3, so as to control the temperature when the fly ash desorbs dioxins; the second temperature sensor 10 is installed in the second air pipe, and is used to detect the temperature of the mixture of gas, dioxins and a small amount of fly ash that flows back into the incinerator 301, so as to control the temperature of the mixture, so as to prevent the regeneration of dioxins during the reflow process caused by too low temperature; and the operation and output power of the fan 9 can be controlled by the controller 14.

[0039] In order to realize the control of the first air valve 101 and the second air valve 102 by the controller 14, the first air valve 101 and the second air valve 102 are both electrically controlled valves, and the first air valve 101 and the second air valve 102 are both electrically connected to the controller 14. The controller 14 can control the switch and the opening size of the first air valve 101 and the second air valve 102, thereby facilitating the purpose of automatically adjusting the temperature of the flue gas introduced from the incineration system 3.

[0040] In the incineration system 3, a bag filter 309 is used to collect fly ash in the flue gas. The collected fly ash is sent to the intermediate ash bin 310 for storage through a funnel and a fly ash conveyor belt. The intermediate ash bin 310 is used as an ash source for the star feeder 12 to provide fly ash for the star feeder 12. The ash inlet 5 is connected to the output end of the star feeder 12. The input end of the star feeder 12 is used to connect to the intermediate ash bin 310. The star feeder 12 is connected to the controller 1. 4 is electrically connected, so that the fly ash in the intermediate ash storage 310 is transported from the ash inlet 5 to the first air duct 203 by the star feeder 12 for premixing with the flue gas introduced from the combustion system. The star feeder 12 is characterized in that it can evenly and continuously provide fly ash to the second air duct 7, which can ensure that the gas and solid are relatively stable, so that the pneumatic conveying can work normally. At the same time, the upper and lower air pressures of the star feeder 12 can be isolated to play a gas locking role. The star feeder 12 operates continuously, and the fly ash processing amount per hour is 1.2-1.6t. The output of the star feeder 12 can be adjusted in linkage according to the detection data of the particle detector 11 at the rear.

[0041] In order to achieve the desorption of dioxins, the mixture of flue gas and fly ash in the first air pipe is sent to the air-powder mixer 4, and the air and powder are quickly and dynamically mixed. The residence time of the mixture of flue gas and fly ash in the air-powder mixer 4 is about 10-30s, so that the flue gas is used to provide a high-temperature and low-oxygen environment for the fly ash in the air-powder mixer 4 to achieve the desorption of dioxins.

[0042] In a further embodiment, the gas-powder separation component 6 includes a first gas-powder separator 601 and a second gas-powder separator 602, the input end of the first gas-powder separator 601 is connected to the output end of the gas-powder mixer 4, the input end of the second gas-powder separator 602 is connected to the gas output end of the first gas-powder separator 601, the gas output end of the second gas-powder separator 602 is connected to the air mixing chamber 13 through the second air duct 7, and the powder output ends of the first gas-powder separator 601 and the second gas-powder separator 602 are connected to the ash storage 313, so that the desorbed fly ash and gas are sent to the first gas-powder separator 601 for the first gas-powder separation, separating about 50% of the fly ash, and then passing through the second gas-powder separator 602 for secondary separation, and the remaining fly ash is separated again, so as to achieve the purpose of finally realizing that 5-10% of the fly ash of the first fly ash is sent back to the incinerator 301. Since the activated carbon added before the bag filter 309 in the incineration system 3 adsorbs a large amount of Cl-containing components and metal oxides such as Fe and Cu, these metal oxides on the surface of the activated carbon catalyze the regeneration of dioxins, promote the secondary generation of dioxins and adsorb on such adsorbents, therefore, fly ash with small particle size contains more dioxins.

[0043] Therefore, in order to prevent the dioxins in the small-size fly ash from being not completely desorbed and to prevent the separated secondary fly ash from regenerating dioxins, in this embodiment, the fly ash and dioxin mixed gas of 5-10% of the primary fly ash is returned to the incinerator 301 through the second air duct 7 for dioxin decomposition. In order to prevent the dioxins from being regenerated and re-adsorbed in the fly ash, the temperature in the second air duct 7 should not be lower than 550° C. In addition, most of the fly ash returned to the furnace is activated carbon and other substances, which can be oxidized to generate carbon dioxide in the incinerator 301 and will no longer be collected in the form of fly ash. Therefore, this embodiment can also achieve the effect of reducing the amount of primary fly ash.

[0044] It should be noted that the boiling point of dioxin is 421.2℃~446.5℃, and the thermal decomposition temperature is above 700℃. Experiments have shown that when the riverbed mud containing dioxin is pyrolyzed for 30 minutes at 800℃ in a nitrogen atmosphere, the concentration of PCDFs in the solid phase product drops from 0.63ng-TEQ / g to 0.001ng-TEQ / g. After 60 minutes or more, the concentration in the solid phase is 0. It can be seen that thermal desorption requires a long time and a high temperature. Therefore, in a short period of time, dioxin cannot be completely desorbed into gaseous state, and some dioxin remains in the fly ash.

[0045] In the reaction of synthesizing dioxins, carbon source and chlorine source are needed. The main carbon source often comes from the unburned carbon residue in the fly ash and the activated carbon sprayed during flue gas treatment. The main chlorine source tends to be deposited on the surface of fly ash particles with a particle size of 10μm or less. In addition, a study found through flotation that fine particles with a particle size of less than 2.0μm in fly ash contribute 80% of the toxic equivalent, which is similar to the results of previous studies, that is, the dioxin content in particles with a small particle size is higher. According to tests, the part with a particle size of less than 2.5μm accounts for about 11% of the total fly ash. Therefore, this system is designed to recycle 5-10% of the fly ash to reduce the impact caused by the failure of some dioxins to be desorbed.

[0046] In addition, the temperature of the fly ash treated by this system is maintained at no less than 550°C, and there is a cooling process when entering the ash bin 313. In order to avoid the regeneration of dioxins in the fly ash within this temperature drop range, 5-10% of the small particle fly ash is designed to be returned to the furnace, taking away the carbon source for the generation of dioxins, cutting off the main condition for the regeneration of dioxins, and avoiding the regeneration of dioxins when the fly ash enters the ash bin 313.

[0047] In this embodiment, in order to achieve the purpose of returning 5-10% of the fly ash to the furnace, the first gas-powder separator 601 and the second gas-powder separator 602 are connected in series, and the gas-powder separation efficiency of the first gas-powder separator 601 is about 50%. The separation efficiency of the first gas-powder separator 601 can be adjusted according to the detection data of the particle detector 11 in the second air duct 7.

[0048] In order to avoid the direct collision of the high-temperature gas in the second air pipe and the medium-temperature gas (the slag air temperature is about 200°C) in the secondary air pipe 302 to affect the secondary air pipe 302, a mixing chamber 13 is set up for premixing the two gases. The two input ends of the mixing chamber 13 are respectively connected to the second air pipe 7 and the slag storage 305, and the output end of the mixing chamber 13 is connected to the incinerator 301. In this way, the high-temperature gas and the medium-temperature gas are evenly mixed in the mixing chamber 13 and then enter the incinerator 301 through the secondary air pipe 302, thereby avoiding the following adverse effects on the secondary air pipe 302 caused by the direct collision of the high-temperature gas and the medium-temperature gas: 1. The high-temperature air and the medium-temperature gas are mixed. 1. When encountering 2. high-temperature air, thermal stress will be generated on the pipe wall due to the temperature difference, and this thermal stress may cause plastic deformation or fatigue damage to the pipe material; 2. High-temperature air may cause local overheating of the pipe, thereby causing safety hazards, especially when the performance of the pipe material degrades at high temperatures, safety problems are more likely to occur; 3. The encounter between high-temperature air and medium-temperature gas may cause pressure fluctuations in the pipe, and in extreme cases may cause explosions and other dangerous situations; 4. Since temperature changes may cause pipe deformation or damage, the maintenance cost of the pipe may increase; 5. Long-term temperature changes may accelerate the aging of pipe materials, thereby shortening the service life of the pipe.

[0049] In this embodiment, negative pressure is adopted, that is, the suction force of the fan 9 is used to drive the fly ash and flue gas, which can avoid secondary pollution caused by flue gas overflow. A high-temperature and wear-resistant duct fan 9 is set at the second air duct 7 to drive the desorbed dioxin mixed air back to the furnace.

[0050] To prevent the high-temperature air from cooling down, insulation measures are taken for the first air duct 203, the second air duct 7, the gas-powder mixer 4, the first gas-powder separator 601, the second gas-powder separator 602 and other pipelines, for example, using lightweight low-insulation ceramic fiber modules and other materials for insulation.

[0051] In this embodiment, the fly ash dioxin removal system can be organically combined with the existing waste incineration system 3, and the high-temperature flue gas of the incinerator 301 in the existing waste incineration process is used to desorb dioxins in the fly ash, and then the desorbed dioxin mixed air is returned to the furnace for high-temperature oxidation. The existing waste incineration process is cleverly used, and the online production conditions are fully utilized to achieve the reuse of flue gas waste heat. There is no need for secondary large energy investment, thereby effectively reducing costs. In addition, because fly ash contains a large amount of CaO and other substances, 5-10% of the fly ash can reduce the generation of sulfur oxides after returning to the furnace, reducing the difficulty of subsequent exhaust gas treatment.

[0052] Example 2

[0053] like Figure 6 As shown, a fly ash dioxin removal method involved in Example 2 of the present application is applied to the fly ash dioxin removal system as described in Example 1, and the fly ash dioxin removal method includes:

[0054] S100, start the fan 9, adjust the opening of the first air valve 101 and the second air valve 102 according to the detection data of the first temperature sensor 8 (i.e., the first air temperature), and adjust the temperature of the mixture sent to the air-powder mixer 4 to 650°C-750°C;

[0055] Specifically, due to the original intake air temperature or operating conditions in the incinerator 301, the temperature of the high-temperature air drawn out is unstable, and an air intake is set between the incinerator 301 and the first-level waste heat recovery equipment 303 and between the first-level waste heat recovery equipment 303 and the second-level waste heat recovery equipment 304, respectively connecting the first branch air duct 201 and the second branch air duct 202, and respectively setting the first air valve 101 and the second air valve 102, and adjusting the opening of the first air valve 101 and the second air valve 102 according to the temperature detected by the first temperature sensor 8 to achieve the purpose of temperature regulation. If the measured temperature is lower than the initial set wind temperature of 650°C or the set value, the air intake after the incinerator 301 is increased, that is, the opening of the first air valve 101 is increased, and the air intake between the primary waste heat recovery device 303 and the secondary waste heat recovery device 304 is reduced, that is, the opening of the second air valve 102 is reduced; if the detected temperature is higher than the initial set wind temperature of 750°C or the set value, the air intake between the primary waste heat recovery device 303 and the secondary waste heat recovery device 304 is increased, that is, the opening of the second air valve 102 is increased, and the air intake after the incinerator 301 is reduced, that is, the opening of the first air valve 101 is reduced. The whole process runs automatically, keeping the total air volume in the first air duct 203 unchanged.

[0056] S200, starting the star feeder 12, and adjusting the parameters of the gas-powder separation component 6 according to the detection data of the particle detector 11, so that the gas output by the gas-powder separation component 6 carries a preset amount of fly ash;

[0057] Specifically, the star feeder 12 provides a fixed amount of fly ash, which is pre-mixed with the flue gas drawn from the incineration system 3 and then enters the air-powder mixer. The fly ash and the high-temperature flue gas are fully mixed in the air-powder mixer 4. In order to ensure sufficient mixing and desorption rate, the mixture of hot air and fly ash in the first air duct 203 stays in the air-powder mixer 4 for 10s-30s, and the dioxins in the fly ash are desorbed in a high temperature environment of 650℃-750℃. The air volume in the first air duct 203 is 1000m 3 / h-2000m 3 / h, the ash delivery rate of the star feeder 12 is 1.2t / h-1.6t / h, which not only ensures the desorption rate of dioxins in the fly ash, but also ensures the treatment efficiency of the fly ash.

[0058] After that, about 50% of the fly ash is separated by the first air-powder separator; and the remaining fly ash is separated by the second air-powder separator, so as to achieve the purpose of finally returning 5-10% of the primary fly ash (i.e., 5-10% of the original fly ash) to the furnace. The amount of fly ash is measured by the particle detector 11 on the second air duct 7. If the amount of fly ash returned to the furnace is less than 5% of the original fly ash, the controller 14 is used to reduce the working efficiency of the second air-powder separator and increase the amount of fly ash returned to the furnace; if the amount of fly ash returned to the furnace is greater than 10% of the original fly ash, the controller 14 is used to increase the working efficiency of the second air-powder separator and reduce the amount of fly ash returned to the furnace. The secondary fly ash separated by the first air-powder separator and the second air-powder separator enters the ash bin 313.

[0059] S300, adjusting the openings of the first valve and the second valve according to the detection data of the second temperature sensor 10 (i.e., the second wind temperature), and adjusting the temperature of the mixture in the second air duct 7 to not less than 550°C. For example, if the temperature detected by the second temperature sensor 10 is 500°C (lower than 550°C), the proportion of high-temperature flue gas drawn out from the incinerator 301 can be increased by increasing the opening of the first valve and reducing the opening of the second valve, thereby increasing the temperature of the flue gas in the first air duct 203. If the temperature of the mixture in the second air duct 7 has been adjusted to not less than 550°C, but the temperature detected by the first temperature sensor 8 is lower than 650°C, the opening of the first valve should be increased and the opening of the second valve should be reduced to increase the proportion of high-temperature flue gas drawn out from the incinerator 301, thereby increasing the temperature in the first air duct 203; if the temperature of the mixture in the second air duct 7 has been adjusted to not less than 550°C, but the temperature detected by the first temperature sensor 8 is higher than or equal to 650°C, there is no need to adjust the openings of the first valve and the second valve.

[0060] The above fly ash dioxin removal method was used to conduct a test in a waste incineration plant. The equipment was connected and fly ash from the transfer ash bin 310 and the ash bin 313 was taken for dioxin detection. The specific process conditions and test results are shown in Table 1 below:

[0061] Table 1: Process conditions and test results

[0062]

[0063] It can be seen from Table 1 above that the air volume in the first air duct 203 is 1000m 3 / h-2000m 3 / h, the ash delivery rate of the star feeder 12 is 1.2t / h-1.6t / h, the temperature of the mixture fed into the gas-powder mixer 4 is 650℃-696℃, the temperature of the return air in the second air duct 7 is 550℃-570℃, which can reduce the dioxin concentration in the fly ash from 0.481-0.593ng-TEQ / g to 0.037-0.048ng-TEQ / g. It can be seen that a very high removal rate of dioxins in fly ash has been achieved under the above process conditions.

[0064] In order to avoid the regeneration of dioxins, it is necessary to ensure that the temperature of the fly ash after passing through the gas-powder mixer 4, the first gas-powder separator 601 and the second gas-powder separator 602 is still higher than 550°C, and the temperature is measured by the second temperature sensor 10 on the second air duct 7. Corresponding control is performed according to the temperature measured by the second temperature sensor 10. If the temperature measured by the second temperature sensor 10 is less than 550°C, the temperature in the first air duct 203 is increased by the controller 14, that is, the set value of the first temperature sensor 8 is increased, and the opening of the first air valve 101 and the second air valve 102 is controlled according to the control logic in step S100 to increase the temperature in the second air duct 7. Afterwards, the dioxin mixed air returns to the incinerator 301 through the second air duct 7 for combustion, and the dioxins are removed in the incinerator 301 through secondary oxidation.

[0065] In this embodiment, the corresponding valve opening and the ash delivery rate of the star feeder 12 can be automatically controlled according to the detection data of the first temperature sensor 8, the second temperature sensor 10 and the particle detector 11, thereby realizing the automatic control of the fly ash dioxin removal system, greatly simplifying the control process, and at the same time controlling the desorption temperature of the fly ash within the range of 650°C-750°C to effectively ensure the desorption rate of dioxins in the fly ash, thereby improving the removal efficiency of dioxins in the fly ash, and being able to transport most of the dioxins that are not completely desorbed back to the incinerator 301 through the second air duct 7 with an internal temperature of not less than 550°C, effectively avoiding the regeneration of dioxins and eliminating secondary pollution.

[0066] The above are only preferred specific implementations of the present application; however, the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and its improved ideas of the present application within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A fly ash dioxin removal system, characterized in that: It includes an induced draft duct with a temperature control component, one end of the induced draft duct is used to connect to the incineration system, the other end of the induced draft duct is connected to a gas-powder mixer, an end of the induced draft duct close to the gas-powder mixer is preset with an ash inlet, the output end of the gas-powder mixer is connected to a gas-powder separation component, the gas output end of the gas-powder separation component is connected to the secondary air duct of the incinerator through a second air duct, the induced draft duct is equipped with a first temperature sensor, the second air duct is equipped with a fan, a second temperature sensor and a particle detector, and the first temperature sensor, the fan, the second temperature sensor and the particle detector are all electrically connected to a controller.

2. The fly ash dioxin removal system according to claim 1, characterized in that: The incineration system includes an incinerator, a primary waste heat recovery device and a secondary waste heat recovery device. The induced draft duct includes a first air duct, one end of which is connected to a gas-powder mixer, and the other end of the first air duct is connected to a first branch air duct and a second branch air duct. The first branch air duct is used to connect the pipeline between the incinerator and the primary waste heat recovery device, and the second branch air duct is used to connect the pipeline between the primary waste heat recovery device and the secondary waste heat recovery device. The temperature control component includes a first air valve and a second air valve. The first air valve is installed on the first branch air duct, and the second air valve is installed on the second branch air duct.

3. The fly ash dioxin removal system according to claim 2, characterized in that: The first air valve and the second air valve are both electrically controlled valves, and the first air valve and the second air valve are both electrically connected to the controller.

4. The fly ash dioxin removal system according to claim 3, characterized in that: The ash inlet is connected to the output end of the star-shaped feeder, the input end of the star-shaped feeder is used to connect to the ash source, and the star-shaped feeder is electrically connected to the controller.

5. The fly ash dioxin removal system according to claim 3, characterized in that: The gas-powder separation assembly includes a first gas-powder separator and a second gas-powder separator, wherein the input end of the first gas-powder separator is connected to the output end of the gas-powder mixer, the input end of the second gas-powder separator is connected to the gas output end of the first gas-powder separator, and the gas output end of the second gas-powder separator is connected to the air mixing chamber through a second air duct.

6. The fly ash dioxin removal system according to claim 3, characterized in that: One end of the second air duct away from the gas-powder separation component is connected to one of the input ends of the air mixing chamber, the other input end of the air mixing chamber is used to connect to the slag storage, and the output end of the air mixing chamber is connected to the incinerator.

7. A method for removing dioxins from fly ash, characterized in that: Applied to the system according to any one of claims 4 to 6, the method comprises: Start the fan, adjust the opening of the first air valve and the second air valve according to the detection data of the first temperature sensor, and adjust the temperature of the mixture sent to the air-powder mixer to 650°C-750°C; Start the star feeder and adjust the parameters of the gas-powder separation component according to the detection data of the particle detector so that the gas output by the gas-powder separation component carries a preset amount of fly ash; The openings of the first valve and the second valve are adjusted according to the detection data of the second temperature sensor, so that the temperature of the mixture in the second air duct is adjusted to not less than 550°C.

8. The method for removing dioxins from fly ash according to claim 7, characterized in that: The amount of fly ash carried in the gas output by the gas-powder separation component is 5%-10% of the original fly ash amount.

9. The method for removing dioxins from fly ash according to claim 7, characterized in that: The air volume in the first air duct is 1000m 3 / h-2000m 3 / h, the ash delivery rate of the star feeder is 1.2t / h-1.6t / h.

10. The method for removing dioxins from fly ash according to claim 7, characterized in that: The residence time of the mixture of hot air and fly ash in the first air duct in the air-powder mixer is 10s-30s.

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