A fly ash dioxin removal system and method

Abstract

The present application discloses a fly ash dioxin removal system and method, which relates to the technical field of fly ash treatment, and solves the problems of low removal efficiency, cumbersome process and high cost existing in the process of removing dioxin from fly ash. The system includes an air inlet pipe for introducing high-temperature flue gas, an air-powder mixer, an air-powder separation component and a secondary air pipe, as well as a first temperature sensor installed in the air inlet pipe, a fan, a second temperature sensor and a particulate matter detector installed in the second air pipe, and a controller. The system can desorb dioxin in fly ash by using the high-temperature flue gas of the incinerator in the existing waste incineration process, and then return the desorbed dioxin mixed air to the furnace for high-temperature oxidation. It ingeniously uses the existing waste incineration process and makes full use of the on-line production conditions, without a large secondary energy input, thus effectively reducing the cost.

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 a bag filter after a series of treatments following a high-temperature incineration process. The source industries include waste incineration, hazardous waste incineration, etc. For example, in the waste incineration industry: it adsorbs high concentrations of organic and inorganic pollutants from the flue gas. In particular, fly ash contains highly carcinogenic, teratogenic, and mutagenic dioxins and heavy metals, etc. If not properly treated, they will be transported everywhere from the emission sources through the atmosphere, rainwater, etc., polluting the atmosphere and water sources, entering the food chain, and causing harm to people. Therefore, realizing the harmless treatment and resource utilization of fly ash is one of the current urgent environmental protection problems to be solved.

[0003] Currently, the disposal technologies for dioxins in fly ash mainly include solidification and landfill, biodegradation, chemical removal, low-temperature pyrolysis, and high-temperature treatment, etc. Among them, solidification and landfill may become potential sources of dioxin pollution in landfills; the biodegradation method and low-temperature pyrolysis have the advantages of environmental friendliness and low cost, but the degradation efficiency of dioxins is not high; the chemical removal method has the advantages of low energy consumption and high efficiency, but there is a problem of secondary pollution. Co-disposal of fly ash in cement kilns is the current mainstream technology for high-temperature treatment. To strictly control the chlorine content, the doping amount of fly ash is very low. Therefore, cement kilns can only achieve the resource utilization of a limited amount of fly ash.

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

[0005] Existing dioxin removal processes often need to use equipment for high-temperature desorption and re-oxidation, or use inert gas for the gas in high-temperature desorption. In both cases, third-party equipment and processes need to be introduced, the process is cumbersome, the operation is difficult, and the cost of dioxin removal and treatment is increased.

[0006] For example, in the patent "Treatment Equipment and Method for Medium-Temperature Desorption Combined with High-Temperature Plasma Oxidation to Destroy Dioxin Compounds" with the publication number TW200736549A, a temperature between 450 - 850 °C is selected for desorption. After that, the desorbed gas enters a high-temperature plasma oxidation chamber at least above 1200 °C to destroy the dioxin-containing compounds in the gas stream by high-temperature oxidation with a plasma torch, that is, the plasma torch process. Then, it is discharged after passing through equipment such as a quench tower, a lime reaction tower, an activated carbon injection device, and a filter bag dust collector. Summary of the Invention

[0007] The purpose of this application is to overcome the problems of low removal efficiency, cumbersome process and high cost existing 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, which includes an induced air pipe with a temperature adjustment component. One end of the induced air pipe is used to connect to an incineration system, and the other end of the induced air pipe is connected to an air-powder mixer. An ash inlet is preset at one end of the induced air pipe close to the air-powder mixer. The output end of the air-powder mixer is connected to an air-powder separation component. The gas output end of the air-powder separation component is connected to the secondary air pipe of the incinerator through a second air pipe. A first temperature sensor is installed on the induced air pipe, and a fan, a second temperature sensor and a particulate matter detector are installed on the second air pipe. The first temperature sensor, the fan, the second temperature sensor and the particulate matter detector are all electrically connected to a controller.

[0009] In some possible implementation manners, the incineration system includes an incinerator, a primary waste heat recovery device and a secondary waste heat recovery device. The induced air pipe includes a first air pipe. One end of the first air pipe is connected to the air-powder mixer, and the other end of the first air pipe is connected to a first branch air pipe and a second branch air pipe. The first branch air pipe is used to connect the pipeline between the incinerator and the primary waste heat recovery device, and the second branch air pipe is used to connect the pipeline between the primary waste heat recovery device and the secondary waste heat recovery device. The temperature adjustment component includes a first air valve and a second air valve. The first air valve is installed on the first branch air pipe, and the second air valve is installed on the second branch air pipe.

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

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

[0012] In some possible implementation manners, the air-powder separation component includes a first air-powder separator and a second air-powder separator. The input end of the first air-powder separator is connected to the output end of the air-powder mixer. The input end of the second air-powder separator is connected to the gas output end of the first air-powder separator. The gas output end of the second air-powder separator is connected to a mixing air chamber through a second air pipe.

[0013] In some possible implementation manners, one end of the second air pipe far from the air-powder separation component is connected to one input end of the mixing air chamber. The other input end of the mixing air chamber is used to connect to a slag bin, and the output end of the mixing air 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. The method includes:

[0015] Start the fan, adjust the opening degrees 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 fed into the air-powder mixer to 650°C - 750°C;

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

[0017] Adjust the opening degrees of the first valve and the second valve according to the detection data of the second temperature sensor, and adjust the temperature of the mixture in the second air duct to not less than 550°C.

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

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

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

[0021] The present application has the following beneficial effects:

[0022] 1. The system of the present application can be organically combined with the existing waste incineration system. The high-temperature flue gas of the incinerator in the existing waste incineration process is used for the desorption of 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 skillfully utilized, and the on-line production conditions are fully utilized. There is no large secondary energy input, thus effectively reducing the cost;

[0023] 2. The method of this application can automatically control the opening degree of the corresponding valves and the ash feeding rate of the star feeder according to the detection data of the first temperature sensor, the second temperature sensor and the particulate matter detector, realizing the automatic control of the fly ash dioxin removal system, greatly simplifying the control process. At the same time, the temperature of fly ash desorption is controlled within the range of 650°C - 750°C, effectively ensuring the desorption rate of dioxin in fly ash, thereby improving the removal efficiency of dioxin in fly ash. And most of the incompletely desorbed dioxin can be conveyed back to the incinerator through the second air duct with an internal temperature not lower than 550°C, effectively avoiding the regeneration of dioxin and there is no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 is the structural block diagram of the fly ash dioxin removal system in Embodiment 1 of this application;

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

[0028] Figure 3 is the circuit block diagram of the fly ash dioxin removal system in Embodiment 1 of this application;

[0029] Figure 4 is the type I adsorption isotherm model diagram of dioxin in fly ash;

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

[0031] Figure 6 is the flowchart of the fly ash dioxin removal method in Embodiment 2 of this application.

[0032] Reference Signs:

[0033] 1. Temperature adjustment component; 101. First air valve; 102. Second air valve; 2. Induction 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 bin; 306. Garbage pit; 307. Primary air duct; 308. Tail gas pre-treatment equipment; 309. Bag filter; 310. Transfer ash bin; 311. Tail gas post-treatment equipment; 312. Exhaust stack; 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. Particulate matter detector; 12. Star feeder; 13. Air mixing chamber; 14. Controller. Detailed implementation mode

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Embodiment 1

[0036] As Figure 2 shown, the incineration system 3 includes an incinerator 301, a secondary air duct 302, a primary waste heat recovery equipment 303, a secondary waste heat recovery equipment 304, a slag bin 305, a garbage pit 306, a primary air duct 307, a tail gas pre-treatment equipment 308, a bag filter 309, a tail gas post-treatment equipment 311 and an exhaust stack 312. The existing waste incineration process is generally as follows: the waste to be incinerated is usually stored in the garbage pit 306, and the waste is transported to the incinerator 301 for incineration. The primary waste heat recovery equipment 303 is used to recover the heat in the flue gas once, and then the secondary waste heat recovery equipment 304 is used to recover the heat in the flue gas twice. The slag is transported to the slag bin 305 for storage. The flue gas is treated by the tail 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 stack 312 after being treated by the tail gas post-treatment equipment 311. Among them, in order to avoid the waste gas in the garbage pit 306 and the slag bin 305 from polluting the environment, the waste gas 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 oxygen required for combustion for the incinerator 301, and on the other hand, it avoids the waste gas from polluting the surrounding environment.

[0037] It should be noted that the oxygen content in 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 conforms to the type I adsorption isotherm model as shown in Figure 4 . When converted to the adsorption isobar, it is as shown in Figure 5 , that is, 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 environmental temperature of fly ash and reducing the oxygen content in the environment to reduce the adsorption amount of dioxins in fly ash.

[0038] As shown in Figure 1As shown in the figure, a fly ash dioxin removal system according to Embodiment 1 of the present application includes an air duct 2 with a temperature adjustment component 1. Among them, the air duct 2 includes a first air duct 203. One end of the first air duct 203 is connected to an air-powder mixer 4, and the other end of the first air duct 203 is connected with 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 primary waste heat recovery device 303, and the second branch air duct 202 is used to connect the pipeline between the primary waste heat recovery device 303 and the secondary waste heat recovery device 304. The temperature adjustment component 1 includes a first air valve 101 and a second air valve 102. 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. High-temperature flue gas is led 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. Medium-temperature flue gas is led out from the primary waste heat recovery device 303 through the second branch air duct 202. Generally, the temperature of the flue gas after being treated by the primary waste heat recovery device 303 is about 200°C - 700°C. By adjusting the opening degrees of the first valve and the second valve, the temperature of the introduced flue gas can be adjusted by adjusting the ratio of the high-temperature flue gas and the medium-temperature flue gas. The other end of the air duct 2 is connected to an air-powder mixer 4. An ash inlet 5 is preset at one end of the air duct 2 close to the air-powder mixer 4. Among them, the ash inlet 5 is used to introduce fly ash, so that the fly ash is pre-mixed with the flue gas introduced from the incineration system 3 in the first air pipe. The pre-mixed flue gas and fly ash are fully mixed in the air-powder mixer 4, and the high temperature of the flue gas is used to desorb the dioxin in the fly ash. The output end of the air-powder mixer 4 is connected to an air-powder separation component 6. After the dioxin in the fly ash is desorbed, it is separated from the particulate fly ash in the air-powder separation component 6. The gas output end of the air-powder separation component 6 is connected to the secondary air duct 302 of the incinerator 301 through a second air duct 7. The desorbed dioxin returns to the incinerator 301 with the gas through the second air duct 7 and is oxidized at high temperature again in the incinerator 301 to achieve the effect of removing dioxin. At the same time, when the air-powder separation is carried out in the air-powder separation component 6, a small amount of fly ash cannot be completely separated, so that a small amount of fly ash is mixed in the dioxin and the gas and also returns to the incinerator 301 along the second air pipe. The air 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 particulate matter detector 11, as 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-solid separation assembly 6 includes a first gas-solid separator 601 and a second gas-solid separator 602. The input end of the first gas-solid separator 601 is connected to the output end of the gas-solid mixer 4. The input end of the second gas-solid separator 602 is connected to the gas output end of the first gas-solid separator 601. The gas output end of the second gas-solid separator 602 is connected to the air mixing chamber 13 through the second air duct 7. The powder output ends of the first gas-solid separator 601 and the second gas-solid separator 602 are connected to the ash silo 313, so as to send the desorbed fly ash and gas into the first gas-solid separator 601 for the first gas-solid separation, separating about 50% of the fly ash, and then passing through the second gas-solid separator 602 for secondary separation to separate the remaining fly ash again, so as to finally achieve the purpose that 5-10% of the fly ash with the primary fly ash amount is sent back to the incinerator 301. Since activated carbon and the like added before the bag filter 309 in the incineration system 3 adsorb a large amount of Cl components and metal oxides such as Fe and Cu, and these metal oxides are on the surface of the activated carbon, which play a catalytic role in the regeneration of dioxins, promoting the secondary generation of dioxins and adsorbing on such adsorbents. Therefore, the fly ash with a small particle size contains more dioxins.

[0043] Therefore, in order to avoid incomplete desorption of dioxins in the fly ash with a small particle size and to avoid the re-generation of dioxins in the separated secondary fly ash, in this embodiment, 5-10% of the fly ash with the primary fly ash amount and the dioxin mixture gas are returned to the incinerator 301 through the second air duct 7 for dioxin decomposition. In order to avoid the re-generation of dioxins and re-adsorption 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 substances such as activated carbon, which can be oxidized to generate carbon dioxide in the incinerator 301 and will not be collected in the form of fly ash again. 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 dioxins is 421.2 °C to 446.5 °C, and the thermal decomposition temperature is above 700 °C. Experiments have shown that in a nitrogen atmosphere at 800 °C, the concentration of PCDFs in the solid-phase product of the river bottom sediment containing dioxins decreased from 0.63 ng-TEQ / g to 0.001 ng-TEQ / g after pyrolysis for 30 min, and the concentration in the solid phase was 0 after 60 min and above. It can be seen that thermal desorption requires a long time and a high temperature. Therefore, in a short time, dioxins cannot be completely desorbed into a gaseous state, and there is still some dioxin remaining in the fly ash.

[0045] In the reaction of synthesizing dioxins, a carbon source and a chlorine source are required. The main carbon source often comes from the unburned residual carbon in fly ash and the activated carbon ejected during flue gas treatment. The main chlorine source tends to deposit on the surface of fly ash particles with a particle size near and below 10 μm. In addition, through flotation, it is found that fine particles with a particle size less than 2.0 μm in fly ash contribute 80% of the toxic equivalent, which is similar to the previous research results, that is, the content of dioxins in smaller particles is higher. After detection, the part with a particle size less than 2.5 μm accounts for about 11% of the total fly ash. Therefore, 5-10% of the fly ash is designed to be recycled to the furnace to reduce the impact caused by the non-desorption of some dioxins.

[0046] In addition, the temperature of the fly ash treated by this system is maintained at not less than 550 °C, and there is a cooling process during the process of entering the ash bin 313. To avoid the re-generation of dioxins in the fly ash during this temperature reduction interval, 5-10% of the small particle fly ash is designed to be recycled to the furnace, which takes away the carbon source for dioxin generation and cuts off the main conditions for dioxin re-generation, thus avoiding the re-generation of dioxins during the process of fly ash entering the ash bin 313.

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

[0048] To avoid the direct collision of the high-temperature gas in the second air pipe with the medium-temperature gas in the secondary air duct 302 (the furnace slag air temperature is about 200 °C) from affecting the secondary air duct 302, a mixing chamber 13 is set up for pre-mixing of the two gases. The two input ends of the mixing chamber 13 are respectively connected to the second air duct 7 and the furnace slag bin 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 mixed evenly in the mixing chamber 13 and then enter the incinerator 301 through the secondary air duct 302, so as to avoid the following adverse effects on the secondary air duct 302 caused by the direct collision of the high-temperature gas and the medium-temperature gas: 1. When the high-temperature air meets the medium-temperature gas, due to the temperature difference, thermal stress will be generated on the pipe wall, and this thermal stress may cause plastic deformation or fatigue damage to the pipe material; 2. The high-temperature air may cause local overheating of the pipe, thus leading to potential safety hazards, especially when the performance of the pipe material deteriorates at high temperatures, it is more likely to have safety problems; 3. The encounter of the high-temperature air and the medium-temperature gas may cause pressure fluctuations in the pipe, and in extreme cases, dangerous situations such as explosion may occur; 4. Due to temperature changes, the pipe may be deformed or damaged, so the maintenance cost of the pipe may increase; 5. Long-term temperature changes may cause the pipe material to age faster, thus shortening the service life of the pipe.

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

[0050] To prevent the temperature of the high-temperature air from decreasing, heat insulation measures are taken for the first air duct 203, the second air duct 7, the air-powder mixer 4, the first air-powder separator 601, the second air-powder separator 602, and other pipelines. For example, materials such as lightweight low-heat-insulating ceramic fiber modules are used for heat insulation.

[0051] In this embodiment, the fly ash dioxin removal system can be organically combined with the existing waste incineration system 3. The high-temperature flue gas of the incinerator 301 in the existing waste incineration process is used for the desorption of dioxin 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 skillfully utilized, and the on-line production conditions are fully utilized to realize the reuse of the waste heat of the flue gas, without the need for a large secondary energy input, thereby effectively reducing the cost. In addition, since the fly ash contains a large amount of substances such as CaO, the generation of sulfur oxides can be reduced after 5-10% of the fly ash is returned to the furnace, and the difficulty of subsequent tail gas treatment is reduced.

[0052] Embodiment 2

[0053] As Figure 6 shown, a fly ash dioxin removal method according to Embodiment 2 of the present application is applied to the fly ash dioxin removal system as described in Embodiment 1. The fly ash dioxin removal method includes:

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

[0055] Specifically, due to the unstable temperature of the high-temperature air drawn out in the incinerator 301 caused by the original intake air temperature or operating conditions, an air intake is provided between the incinerator 301 and the primary waste heat recovery device 303 and between the primary waste heat recovery device 303 and the secondary waste heat recovery device 304, which are respectively connected to the first branch air duct 201 and the second branch air duct 202, and the first air valve 101 and the second air valve 102 are respectively provided. The opening degrees of the first air valve 101 and the second air valve 102 are adjusted 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 air temperature of 650 °C or the set value, the air intake after the incinerator 301 is increased, that is, the opening degree 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 degree of the second air valve 102 is reduced; if the detected temperature is higher than the initial set air 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 degree of the second air valve 102 is increased, and the air intake after the incinerator 301 is reduced, that is, the opening degree of the first air valve 101 is reduced. The whole process runs automatically to keep the total air volume in the first air duct 203 unchanged.

[0056] S200. Start the star feeder 12 and adjust the parameters of the air-powder separation component 6 according to the detection data of the particulate matter detector 11 so that the gas output by the air-powder separation component 6 carries a preset amount of fly ash.

[0057] Specifically, the star feeder 12 gives a fixed amount of fly ash, which is pre-mixed with the flue gas drawn out 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. To ensure sufficient mixing and desorption rate, the residence time of the hot air and fly ash mixture in the first air duct 203 in the air-powder mixer 4 is 10 s - 30 s, and the high-temperature environment of 650 °C - 750 °C is used for the desorption of dioxins in the fly ash. Among them, the air volume in the first air duct 203 is 1000 m 3 / h - 2000 m 3 / h, and the ash feeding rate of the star feeder 12 is 1.2 t / h - 1.6 t / 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 passing through the first air-powder separator, about 50% of the fly ash is separated; then through the second air-powder separator, the remaining fly ash is separated to achieve the purpose of finally realizing the fly ash recirculation into the furnace with a fly ash amount of 5-10% (i.e., 5-10% of the original fly ash amount). The amount of fly ash is measured by the particulate matter detector 11 on the second air duct 7. If the fly ash recirculation amount is less than 5% of the original fly ash amount, the working efficiency of the second air-powder separator is reduced through the controller 14 to increase the fly ash recirculation amount; if the fly ash recirculation amount is greater than 10% of the original fly ash amount, the working efficiency of the second air-powder separator is increased through the controller 14 to reduce the fly ash recirculation amount. The secondary fly ash separated by the first air-powder separator and the second air-powder separator enters the ash bin 313.

[0059] S300. Adjust the opening degrees of the first valve and the second valve according to the detection data of the second temperature sensor 10 (i.e., the second air temperature) to adjust 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 the high-temperature flue gas drawn from the incinerator 301 can be increased by increasing the opening degree of the first valve and simultaneously reducing the opening degree of the second valve, thereby increasing the temperature of the flue gas in the first air duct 203. Among them, 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 degree of the first valve should be increased and the opening degree of the second valve should be reduced to increase the proportion of the high-temperature flue gas drawn 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 opening degrees of the first valve and the second valve.

[0060] Using the above fly ash dioxin removal method, tests were carried out in a certain waste incineration plant. Connect each device, and take the fly ash from the transfer ash bin 310 and the ash bin 313 respectively for dioxin detection. The specific process conditions and detection results are shown in Table 1 below:

[0061] Table 1: Process Conditions and Detection Results

[0062]

[0063] As can be seen from Table 1 above, the air volume in the first air duct 203 is 1000 m 3 / h - 2000 m 3 / h, the ash feeding rate of the star feeder 12 is 1.2 t / h - 1.6 t / h, the temperature of the mixture fed into the air-powder mixer 4 is 650°C - 696°C, and the temperature of the recirculating air in the second air duct 7 is 550°C - 570°C. The concentration of dioxins in the fly ash can be reduced from 0.481 - 0.593 ng-TEQ / g to within the range of 0.037 - 0.048 ng-TEQ / g. Thus, it can be seen that a very high removal rate of dioxins in the fly ash has been achieved under the above process conditions.

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

[0065] In this embodiment, the opening degrees of the corresponding valves and the ash feeding 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 particulate matter detector 11, realizing the automatic control of the fly ash dioxin removal system, greatly simplifying the control process. At the same time, the temperature of fly ash desorption is controlled within the range of 650°C - 750°C, effectively ensuring the desorption rate of dioxins in the fly ash, thereby improving the removal efficiency of dioxins in the fly ash. And most of the dioxins that have not been completely desorbed can be transported back to the incinerator 301 through the second air duct 7 with an internal temperature not lower than 550°C, effectively avoiding the re-generation of dioxins and there is no secondary pollution.

[0066] The above is only the preferred specific implementation manner of the present application; however, the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application, according to the technical solution of the present application and its improved concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present application.

Claims

1. A fly ash dioxin removal system, characterized in that: The invention comprises an induced draft duct with a temperature regulating component, one end of the induced draft duct is used to connect to an incineration system, wherein the incineration system comprises an incinerator, a primary waste heat recovery device and a secondary waste heat recovery device, the induced draft duct comprises a first air duct, one end of the first air duct is connected to a 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 a pipeline between the incinerator and the primary waste heat recovery device, the second branch air duct is used to connect a pipeline between the primary waste heat recovery device and the secondary waste heat recovery device, the temperature regulating component comprises a first air valve and a second air valve, The first air valve is installed on the first branch air duct, the second air valve is installed on the second branch air duct, the other end of the induced draft duct is connected to the gas-powder mixer, the 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 the 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 the second air duct, the induced draft duct is installed with a first temperature sensor, the second air duct is installed with a fan, a second temperature sensor and a particle detector, the first temperature sensor, the fan, the second temperature sensor and the particle detector are all electrically connected to the controller.

2. The fly ash dioxin removal system according to claim 1, 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.

3. The fly ash dioxin removal system according to claim 2, 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.

4. The fly ash dioxin removal system according to claim 2, 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.

5. The fly ash dioxin removal system according to claim 2, 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.

6. A method for removing dioxins from fly ash, characterized in that: Applied to the system according to any one of claims 3 to 5, 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.

7. The method for removing dioxins from fly ash according to claim 6, 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.

8. The method for removing dioxins from fly ash according to claim 6, 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.

9. The method for removing dioxins from fly ash according to claim 6, 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.

Images