System and method for removing dioxins from fly ash

Abstract

This application discloses a system and method for removing dioxins from fly ash. [Solution] The system includes an intake pipe for drawing in high-temperature flue gas, a gas-powder mixer, a gas-powder separation assembly, a secondary air duct, a first temperature sensor installed in the intake pipe, a fan installed in the second air duct, a second temperature sensor and particulate matter detector, and a controller. The system can desorb dioxins from fly ash using the high-temperature flue gas of an incinerator in a conventional waste incineration process, and then return the desorbed dioxin-mixed air to the furnace for high-temperature oxidation. This cleverly utilizes the conventional waste incineration process and fully utilizes online production conditions, eliminating the need for large secondary energy inputs and effectively reducing costs.

Description

Technical Field

[0001] This application relates to the technical field of fly ash treatment, and particularly to a system and method for removing dioxins in fly ash.

Background Art

[0002] Fly ash is generally a substance with various contaminating components collected by a bag-type dust collector after a series of processes following a high-temperature incineration process. Industries of the source include waste incineration, hazardous waste incineration, etc. For example, in the waste incineration industry, as the incineration treatment of urban domestic waste becomes widespread, the generation amount of fly ash from waste incineration in China is also constantly increasing. Fly ash has complex components, with high-concentration organic and inorganic contaminants adsorbed from flue gas. In particular, it contains dioxins and heavy metals with strong carcinogenicity, teratogenicity, and mutagenicity. If not properly treated, they may be transported everywhere via the atmosphere, rainwater, etc. from the emission source, pollute the atmosphere and water sources, enter the food chain, and pose risks to humans. Therefore, the realization of harmless treatment and resource utilization of fly ash has become one of the urgent environmental protection issues to be solved currently.

[0003] Currently, the treatment technologies for dioxins in fly ash mainly include hardened landfill, biodegradation, chemical removal, low-temperature pyrolysis, and high-temperature treatment, etc. Among them, hardened landfill may pose a potential pollution source of dioxins for landfill sites. Biodegradation and low-temperature pyrolysis have the advantages of being environmentally friendly and having low costs, but the biodegradation efficiency of dioxins is low. Chemical removal has the advantages of low energy consumption and high efficiency, but there is a problem of secondary pollution. Co-processing of fly ash by a cement kiln is the mainstream technology in the previous high-temperature treatment. However, in order to strictly control the chlorine content, the doping amount of fly ash is very low, so the cement kiln can only achieve limited resource utilization of fly ash.

[0004] Furthermore, while washing is also a common method, it removes only a small amount of dioxins. Research has shown that the toxic equivalent in the ash washing wastewater reaches a maximum of 2,3,7,8-TCDD, accounting for 33.93% of the total toxic equivalent in the ash washing wastewater, and the mobility from raw ash to the ash washing wastewater is only 0.26%. This clearly indicates that this method cannot effectively remove dioxins.

[0005] Conventional dioxin removal processes always rely on equipment to perform high-temperature desorption and re-oxidation, or require the use of inert gases as the gases for high-temperature desorption. In either case, it is necessary to introduce third-party equipment and processes, resulting in complex processes, difficult operation, and increased costs for dioxin removal and processing.

[0006] For example, Patent Document 1, "Apparatus and Method for Oxidizing and Destroying Dioxin-Based Compounds by Combining Medium-Temperature Desorption and High-Temperature Plasma," describes a process in which desorption is performed at a temperature between 450 and 850°C, the desorbed gas is then placed in a high-temperature plasma oxidation chamber at at least 1200°C, and the dioxin-containing compounds in the gaseous flow are oxidized and destroyed at high temperature using a plasma torch, i.e., a plasma torch process is performed. After that, the gas is discharged by connecting it to devices such as a quenching tower, lime reaction tower, activated carbon injection device, and filter bag dust collector. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Taiwan Patent Application Publication No. 200736549 [Overview of the project] [Problems that the invention aims to solve]

[0008] This application aims to overcome the problems of the prior art, such as low removal efficiency, complicated processes, and high costs in the process of removing dioxins from fly ash, and to provide a system and method for removing dioxins from fly ash. [Means for solving the problem]

[0009] In the first embodiment, a system for removing dioxins from fly ash is provided, which includes an intake pipe having a temperature control assembly, one end of the intake pipe used for connection to an incineration system, the other end of the intake pipe connected to a gas-powder mixer, an ash inlet pre-provided at the end of the intake pipe closer to the gas-powder mixer, a gas-powder separation assembly connected to the output end of the gas-powder mixer, the gas output end of the gas-powder separation assembly connected to a secondary air duct of an incinerator via a second air duct, a first temperature sensor attached to the intake pipe, a fan, a second temperature sensor and a particulate matter detector attached to the second air duct, and the first temperature sensor, fan, second temperature sensor and particulate matter detector are all electrically connected to a controller.

[0010] In several possible realizations, the incineration system includes an incinerator, a primary heat recovery unit, and a secondary heat recovery unit, the intake pipe includes a first air duct, one end of the first air duct is connected to a gas-powder mixer, and the other end of the first air duct is connected to a first branch air duct for connection to piping between the incinerator and the primary heat recovery unit, and to a second branch air duct for connection to piping between the primary heat recovery unit and the secondary heat recovery unit, and the temperature control assembly includes a first damper attached to the first branch air duct and a second damper attached to the second branch air duct.

[0011] In several possible realizations, both the first damper and the second damper are electrically controlled valves and are electrically connected to a controller.

[0012] In several possible implementations, the ash inlet is connected to the output terminal of a star-shaped feeder, the input terminal of the star-shaped feeder is used to connect to an ash source, and the star-shaped feeder is electrically connected to a controller.

[0013] In several possible realizations, the gas powder separation assembly includes a first gas powder separator and a second gas powder separator, the input terminal of the first gas powder separator being connected to the output terminal of a gas powder mixer, the input terminal of the second gas powder separator being connected to the gas output terminal of the first gas powder separator, and the gas output terminal of the second gas powder separator being connected to a mixed air chamber via a second air duct.

[0014] In several possible realizations, the end of the second air duct away from the gas powder separation assembly is connected to one input end of a mixed air chamber, the other input end of the mixed air chamber is used to connect to a slag chamber, and the output end of the mixed air chamber is connected to an incinerator.

[0015] In the second embodiment, The process involves starting the fan, adjusting the opening of the first and second dampers based on the data detected by the first temperature sensor, and adjusting the temperature of the mixture sent to the gas powder mixer to 650°C to 750°C. The process involves activating a star-shaped feeder, adjusting the parameters of the gas powder separation assembly based on the detection data from the particulate matter detector, and having a predetermined amount of fly ash carried by the gas output from the gas powder separation assembly. A step of adjusting the opening of the first and second valves based on the detection data of the second temperature sensor to adjust the temperature of the mixture in the second air duct to 550°C or higher, The present invention provides a method for removing dioxins from fly ash, applicable to the system described in the first embodiment, including the following:

[0016] In several possible implementations, the amount of fly ash carried to the gas output from the gas powder separation assembly is 5% to 10% of the original amount of fly ash.

[0017] In several possible realizations, the airflow rate in the first air duct is 1000 m³ 3 / h~2000m 3 The ash feeding speed of the star-shaped feeder is 1.2 t / h to 1.6 t / h, and the ash feeding speed of the star-shaped feeder is 1.2 t / h to 1.6 t / h.

[0018] In some possible embodiments, the mixture of hot air and fly ash in the first air duct has a residence time of 10 s to 30 s in the gas powder mixer.

Advantages of the Invention

[0019] This application has the following beneficial effects. [[ID=I0]]

[0020] The system according to this application can be organically combined with a conventional garbage incineration system. By utilizing the high-temperature flue gas of the incinerator in the conventional garbage incineration process to desorb dioxin in fly ash, and then returning the desorbed dioxin mixed air to the furnace for high-temperature oxidation. By skillfully utilizing the conventional garbage incineration process and making full use of the on-line production conditions, there is no need for a large secondary input of energy, and the cost can be effectively reduced.

[0021] The method according to this application can automatically control the opening degree of the corresponding valve and the ash feeding speed of the star feeder based on the detection data of the first temperature sensor, the second temperature sensor and the particulate matter detector. Thereby, the automatic control of the system for removing dioxin in fly ash is realized, the control process is greatly simplified, and by setting the desorption temperature of fly ash within the range of 650 °C to 750 °C, the desorption rate of dioxin in fly ash is effectively guaranteed, and the removal efficiency of dioxin in fly ash is improved. In addition, most of the dioxin that has not been completely desorbed can be sent back to the incinerator through the second air duct with an internal temperature of 550 °C or higher, thereby effectively avoiding the regeneration of dioxin and eliminating secondary pollution.

Brief Description of the Drawings

[0022] The drawings forming a part of this application are shown for a better understanding of this application. The schematic embodiments and their descriptions are for interpreting this application and are not intended to inappropriately limit this application.

[0023] To more clearly explain the technical solutions in the embodiments of this application, the drawings used in describing the embodiments will be briefly described below. However, naturally, the drawings described below represent only a part of the embodiments of this application, and those skilled in the art can conceive of other drawings based on these drawings without requiring any creative effort.

[0024] [Figure 1] This is a structural block diagram of the system for removing dioxins from fly ash according to Example 1 of the present invention. [Figure 2] This is a structural block diagram of a conventional waste incineration system. [Figure 3] This is a circuit block diagram of the system for removing dioxins from fly ash according to Example 1 of the present invention. [Figure 4] This is a model diagram of the type I adsorption isotherm of dioxins in fly ash. [Figure 5] This is a model diagram of the type I adsorption isobars for dioxins in fly ash. [Figure 6] This is a flowchart of the method for removing dioxins from fly ash according to Example 2 of the present invention. [Modes for carrying out the invention]

[0025] The technical solutions in embodiments of the present invention will be described clearly and completely below with reference to the drawings of the embodiments; however, the embodiments described are only a part of the embodiments of the present invention, not all of them. All other embodiments that a person skilled in the art could obtain based on the embodiments of the present invention without requiring any creative effort are all within the scope of the protection of the present invention.

[0026] Example 1 As shown in Figure 2, 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 chamber 305, a waste pit 306, a primary air duct 307, an exhaust gas pretreatment device 308, a cloth bag type dust collector 309, an exhaust gas posttreatment device 311, and an exhaust stack 312. The conventional waste incineration process is generally as follows: Waste to be incinerated is usually stored in the waste pit 306, and the waste is transported to the incinerator 301 for incineration. Heat from the flue gas is recovered primarily by the primary waste heat recovery device 303, and further heat from the flue gas is recovered secondary by the secondary waste heat recovery device 304. Slag is transported to the slag chamber 305 for storage. After being treated by the exhaust gas pretreatment device 308, the flue gas enters the cloth bag type dust collector 309 to filter out solid particles from the flue gas. These solid particles are called fly ash. The gas passes through the exhaust gas aftertreatment device 311 and is discharged into the atmosphere from the exhaust stack 312. Here, the waste gases in the waste pit 306 and slag chamber 305 need to pass through the primary air duct 307 and secondary air duct 302, respectively, to be introduced into the incinerator 301 so as not to pollute the environment. This provides the incinerator 301 with the oxygen necessary for combustion, while simultaneously preventing pollution of the surrounding environment by the waste gases.

[0027] It should be explained that the oxygen content in the flue gas after incinerator 301 is low, at approximately 6%, creating a relatively inert environment that facilitates the desorption of dioxins in the fly ash. The adsorption of dioxins in the fly ash conforms to the Type I adsorption isotherm model shown in Figure 4, and when converted to adsorption isobars, it is as shown in Figure 5. That is, the higher the temperature, the lower the amount of dioxin adsorbed in the fly ash. Therefore, by raising the ambient temperature of the fly ash and reducing the oxygen content in the environment, the amount of dioxin adsorbed in the fly ash can be reduced, and the desorption of dioxins in the fly ash can be achieved.

[0028] As shown in Figure 1, the system for removing dioxins from fly ash according to Embodiment 1 of the present invention includes an intake pipe 2 having a temperature-controlled assembly 1. Here, the intake pipe 2 includes a first air duct 203, one end of which is connected to a gas-powder mixer 4, and the other end of the first air duct 203 is connected to a first branch air duct 201 for connection to piping between the incinerator 301 and a primary heat recovery device 303, and to a second branch air duct 202 for connection to piping between the primary heat recovery device 303 and a secondary heat recovery device 304. The temperature-controlled assembly 1 includes a first damper 101 attached to the first branch air duct 201 and a second damper 102 attached to the second branch air duct 202. High-temperature flue gas is drawn out of the incinerator 301 by the first branch air duct 201. Generally, the temperature inside the incinerator 301 is about 900°C to 1050°C. The second branch air duct 202 draws out medium-temperature flue gas from the primary waste heat recovery device 303. Generally, the temperature of the flue gas after processing by the primary waste heat recovery device 303 is approximately 200°C to 700°C. By adjusting the opening of the first and second valves, the ratio of high-temperature flue gas to medium-temperature flue gas can be adjusted, thereby controlling the temperature of the drawn-in flue gas. A gas-powder mixer 4 is connected to the other end of the intake pipe 2. An ash inlet 5 is pre-installed at the end of the intake pipe 2 closest to the gas-powder mixer 4. Here, the ash inlet 5 is used to draw in fly ash and pre-mix it with the flue gas drawn in from the incineration system 3 in the first gas pipe. After pre-mixing, the flue gas and fly ash are thoroughly mixed in the gas-powder mixer 4, and the high temperature of the flue gas causes the desorption of dioxins in the fly ash. A gas-powder separation assembly 6 is connected to the output end of the gas-powder mixer 4. After desorption, the dioxins in the fly ash are separated from the particulate matter in the fly ash within the gas-powder separation assembly 6. The gas output terminal of the gas-powder separation assembly 6 is connected to the secondary air duct 302 of the incinerator 301 via the second air duct 7. To achieve its role in removing dioxins, the desorbed dioxins are returned to the incinerator 301 via the second air duct 7 along with the gas, and undergo high-temperature oxidation again due to the high temperature in the incinerator 301.Furthermore, when gas powder separation is performed by the gas powder separation assembly 6, a small amount of fly ash cannot be completely separated, so the small amount of fly ash mixes with the dioxin and gas and flows back to the incinerator 301 along the second gas pipe. The first temperature sensor 8 is attached to the intake pipe 2, and the fan 9, second temperature sensor 10, and particulate matter detector 11 are attached to the second air duct 7. As shown in Figure 3, 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 particulate matter detector 11 are all electrically connected to the controller 14. Here, the first temperature sensor 8 is installed inside the first gas pipe and is used to detect the temperature of the exhaust gas drawn from the incineration system 3. This makes it easy to control the temperature at which dioxin desorbs from the fly ash. The second temperature sensor 10 is installed in the second gas pipe and is used to detect the temperature of the mixture of gas, dioxin, and a small amount of fly ash that has flowed back to the incinerator 301. This allows for easy control of the mixture temperature and prevents the regeneration of dioxins during reflux due to excessively low temperatures. The operating power and output power of fan 9 can be controlled by controller 14.

[0029] To enable the controller 14 to control the first damper 101 and the second damper 102, both the first damper 101 and the second damper 102 are electrically controlled valves and are both electrically connected to the controller 14. The controller 14 can control the opening and closing and the degree of opening of the first damper 101 and the second damper 102, thereby making it easier to achieve the objective of automatically adjusting the temperature at which exhaust gas is drawn in from the incineration system 3.

[0030] In the incineration system 3, fly ash in the exhaust gas is collected by a cloth bag type dust collector 309. The collected fly ash is sent to the intermediate ash chamber 310 via a funnel and a fly ash conveyor belt for storage. The intermediate ash chamber 310 provides fly ash to the star-shaped feeder 12 as an ash source for the star-shaped feeder 12. The ash inlet 5 is connected to the output terminal of the star-shaped feeder 12, the input terminal of the star-shaped feeder 12 is used to connect to the intermediate ash chamber 310, and the star-shaped feeder 12 is electrically connected to the controller 14. As a result, the fly ash in the intermediate ash chamber 310 is conveyed by the star-shaped feeder 12 from the ash inlet 5 to the first air duct 203, where it is pre-mixed with the exhaust gas drawn from the combustion system. Here, the star-shaped feeder 12 is characterized by being able to uniformly and continuously supply fly ash to the second air duct 7. This ensures that the gas and solids are stable and that the gas can be transported normally. Furthermore, the star-shaped feeder 12 can also shut off the air pressure above and below it to achieve gas closure. The star-shaped feeder 12 operates continuously, processing 1.2 to 1.6 tons of fly ash per hour. The output of the star-shaped feeder 12 can be adjusted in conjunction with the detection data from the subsequent particulate matter detector 11.

[0031] To achieve dioxin desorption, a mixture of flue gas from the first gas pipe and fly ash is sent to the gas-powder mixer 4, where the air and powder are rapidly and dynamically mixed. The residence time of the flue gas-fly ash mixture in the gas-powder mixer 4 is approximately 10 to 30 seconds. This provides the fly ash with a high-temperature, low-oxygen environment in the gas-powder mixer 4 through the flue gas, thereby achieving dioxin desorption.

[0032] In a further embodiment, the gas-powder separation assembly 6 includes a first gas-powder separator 601 and a second gas-powder separator 602. The input terminal of the first gas-powder separator 601 is connected to the output terminal of the gas-powder mixer 4. The input terminal of the second gas-powder separator 602 is connected to the gas output terminal of the first gas-powder separator 601. The gas output terminal of the second gas-powder separator 602 is connected to the mixed air chamber 13 via a second air duct 7. The powder output terminals of the first gas-powder separator 601 and the second gas-powder separator 602 are connected to the ash chamber 313, so that the detached fly ash and gas are sent to the first gas-powder separator 601 for the first gas-powder separation, separating approximately 50% of the fly ash. Subsequently, the fly ash passes through the second gas-powder separator 602 for a second separation, separating the remaining fly ash again. This ultimately achieves the objective of returning 5-10% of the primary fly ash to the incinerator 301. The activated carbon and other materials introduced before the cloth bag-type dust collector 309 in the incineration system 3 adsorb a large amount of Cl-containing components and metal oxides including Fe, Cu, etc. These metal oxides are present on the surface of the activated carbon and act as a catalyst for the regeneration of dioxins, promoting the secondary generation of dioxins and their adsorption to such adsorbents. Therefore, fly ash with small particle sizes contains more dioxins.

[0033] Therefore, in order to avoid the complete desorption of dioxins in small-particle fly ash and to prevent the regeneration of dioxins in the separated secondary fly ash, in this embodiment, 5-10% of the primary fly ash amount, consisting of a fly ash and dioxin mixture gas, is returned to the incinerator 301 via the second air duct 7 to decompose the dioxins. To prevent the regeneration of dioxins and their re-adsorption to the fly ash, the temperature in the second air duct 7 should be 550°C or higher. Furthermore, the majority of the fly ash returned to the furnace consists of substances such as activated carbon, which are oxidized in the incinerator 301 to produce carbon dioxide and are therefore not collected as fly ash. Thus, this embodiment can further achieve a reduction in the amount of primary fly ash.

[0034] It should be explained that the boiling point of dioxins is 421.2°C to 446.5°C, and their thermal decomposition temperature is above 700°C. Experiments have shown that when riverbed sediment containing dioxins is thermally decomposed for 30 minutes under a nitrogen atmosphere at 800°C, the concentration of PCDFs in the solid phase product decreases from 0.63 ng-TEQ / g to 0.001 ng-TEQ / g, and when thermal decomposition continues for 60 minutes or more, the concentration of PCDFs in the solid phase product becomes 0. Therefore, it is shown that thermal decomposition requires a long time and high temperature. Consequently, dioxins cannot be completely decomposed into a gaseous state in a short time, and some dioxins remain in the fly ash.

[0035] Dioxin synthesis requires both a carbon source and a chlorine source. The main carbon source often originates from unburned residue in fly ash and activated carbon discharged during flue gas treatment. The main chlorine source tends to accumulate on the surface of fly ash particles with a particle size of approximately 10 μm and smaller. Furthermore, studies have shown, through flotation, that fine particles with a particle size of less than 2.0 μm in the fly ash contribute 80% of the toxic equivalent, which is consistent with previous research findings. In other words, the dioxin content is higher in smaller particle sizes, and detection indicates that the portion with a particle size of less than 2.5 μm accounts for approximately 11% of the total fly ash. Therefore, this system is designed to return 5-10% of the fly ash to the furnace to mitigate the effects of some of the dioxin not being desorbed.

[0036] Furthermore, the temperature of the fly ash after processing in this system is maintained at 550°C or higher, and a cooling process is carried out as it enters the ash chamber 313. To avoid the regeneration of dioxins in the fly ash during this cooling phase, the system is designed to return 5-10% of the small-particle fly ash to the furnace, thereby removing the carbon source generated by the dioxins, interrupting the main conditions for dioxin regeneration, and preventing the regeneration of dioxins as the fly ash enters the ash chamber 313.

[0037] In this embodiment, in order to achieve the objective 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. The gas-powder separation efficiency of the first gas-powder separator 601 is approximately 50%, and can be adjusted based on the detection data of the particulate matter detector 11 in the second air duct 7.

[0038] To avoid the impact on the secondary air duct 302 caused by the direct collision of the high-temperature gas in the second gas pipe and the medium-temperature gas (slag wind temperature is approximately 200°C) in the secondary air duct 302, a mixed air chamber 13 is provided for pre-mixing the two gases. The two input ends of the mixed air chamber 13 are connected to the second air duct 7 and the slag chamber 305, respectively, and the output end of the mixed air chamber 13 is connected to the incinerator 301. In this way, the high-temperature gas and medium-temperature gas are uniformly mixed in the mixed air chamber 13 before entering the incinerator 301 via the secondary air duct 302. This avoids the following adverse effects on the secondary air duct 302 caused by the direct collision of the high-temperature gas and medium-temperature gas: 1. When high-temperature air and medium-temperature gas meet, the temperature difference generates thermal stress on the pipe wall, and such thermal stress can cause plastic deformation or fatigue damage to the pipe material. 2. High-temperature air can cause localized overheating of piping, potentially leading to hidden safety hazards, especially since piping materials perform worse at high temperatures. 3. When high-temperature air meets medium-temperature gases, it can cause pressure fluctuations within the piping, potentially leading to dangerous situations such as explosions under extreme conditions. 4. Temperature changes can cause deformation or damage to piping, potentially increasing maintenance costs. 5. Prolonged temperature fluctuations can accelerate the aging of piping materials, potentially shortening the service life of the piping.

[0039] In this embodiment, a negative pressure system is employed, meaning that fly ash and flue gas are discharged by the suction force of the fan 9, thus avoiding secondary contamination due to flue gas overflow. A high-temperature, wear-resistant piping fan 9 is provided in the second air duct 7 to return the dioxin-mixed air after detachment to the furnace.

[0040] To prevent a drop in the temperature of the high-temperature air, 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 piping are all insulated, using materials such as lightweight, low-insulation ceramic fiber modules.

[0041] In this embodiment, the system for removing dioxins from fly ash can be organically combined with the conventional waste incineration system 3. The system utilizes the high-temperature flue gas from the incinerator 301 in the conventional waste incineration process to desorb dioxins from the fly ash. The desorbed dioxin-mixed air is then returned to the furnace for high-temperature oxidation. By cleverly utilizing the conventional waste incineration process and making full use of online production conditions, the reuse of flue gas waste heat is achieved, eliminating the need for significant secondary energy input and effectively reducing costs. Furthermore, since fly ash contains a large amount of substances such as CaO, returning 5-10% of the fly ash to the furnace reduces the generation of sulfur oxides, thereby lowering the difficulty of subsequent exhaust gas treatment.

[0042] Example 2 As shown in Figure 6, the method for removing dioxins from fly ash according to Example 2 of the present application is applicable to the system for removing dioxins from fly ash described in Example 1. The method for removing dioxins from fly ash includes the following steps S100 to S300.

[0043] In S100, the fan 9 is activated, and the openings of the first damper 101 and the second damper 102 are adjusted based on the detection data (i.e., the first air temperature) from the first temperature sensor 8, thereby adjusting the temperature of the mixture sent to the gas powder mixer 4 to 650°C to 750°C.

[0044] Specifically, the temperature of the hot air drawn out inside the incinerator 301 is unstable depending on the original intake air temperature or operating conditions. Air intakes are 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, respectively, and are connected to the first branch air duct 201 and the second branch air duct 202, respectively, and are equipped with the first damper 101 and the second damper 102, respectively. The purpose of temperature control is achieved by adjusting the opening of the first damper 101 and the second damper 102 based on the temperature measured by the first temperature sensor 8. If the detected temperature is below the initially set air temperature of 650°C or the set value, the amount of air taken in after the incinerator 301 is increased, and the amount of air taken in between the primary waste heat recovery device 303 and the secondary waste heat recovery device 304 is decreased. Specifically, the opening of the first damper 101 is increased, and the opening of the second damper 102 is decreased. If the detected temperature is greater than the initially set air temperature of 750°C or a set value, the amount of air taken in between the primary waste heat recovery device 303 and the secondary waste heat recovery device 304 is increased, and the amount of air taken in after the incinerator 301 is decreased. Specifically, the opening of the second damper 102 is increased, and the opening of the first damper 101 is decreased. The entire process operates automatically, maintaining a constant total airflow in the first air duct 203.

[0045] In S200, the star-shaped feeder 12 is activated, and the parameters of the gas powder separation assembly 6 are adjusted based on the detection data from the particulate matter detector 11, causing a predetermined amount of fly ash to be carried by the gas output from the gas powder separation assembly 6.

[0046] Specifically, a fixed amount of fly ash supplied from the star-shaped feeder 12 is pre-mixed with flue gas drawn from the incineration system 3 before entering the gas-powder mixer 4. The fly ash and high-temperature flue gas are thoroughly mixed in the gas-powder mixer 4. To ensure sufficient mixing and desorption rate, the mixture of hot air in the first air duct 203 and fly ash is allowed to reside in the gas-powder mixer 4 for 10 to 30 seconds, and dioxins in the fly ash are desorbed in a high-temperature environment of 650°C to 750°C. Here, the airflow rate in the first air duct 203 is 1000 m³. 3 / h~2000m 3 By setting the ash feeding speed of the star-shaped feeder 12 to 1.2 t / h to 1.6 t / h, not only is the deoxin removal rate from the fly ash guaranteed, but the efficiency of fly ash processing is also guaranteed.

[0047] Subsequently, approximately 50% of the fly ash is separated via the first gas-powder mixer, and the excess fly ash is further separated via the second gas-powder mixer. This ultimately achieves the objective of returning 5-10% of the primary fly ash amount (i.e., 5-10% of the original fly ash amount) to the furnace. The amount of fly ash is measured by the particulate matter 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 amount, the controller 14 reduces the operating efficiency of the second gas-powder mixer and increases 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 amount, the controller 14 improves the operating efficiency of the second gas-powder mixer and reduces the amount of fly ash returned to the furnace. The secondary fly ash separated by the first and second gas-powder mixers enters the ash chamber 313.

[0048] In S300, the openings of the first and second valves are adjusted based on the detection data (i.e., the second air temperature) from the second temperature sensor 10 to adjust the temperature of the mixture in the second air duct 7 to 550°C or higher. For example, if the temperature measured by the second temperature sensor 10 is 500°C (less than 550°C), the opening of the first valve is increased and the opening of the second valve is decreased to increase the proportion of high-temperature exhaust gas drawn from the incinerator 301. This raises the temperature of the exhaust gas in the first air duct 203. Here, if the temperature of the mixture in the second air duct 7 has already been adjusted to 550°C or higher, but the temperature measured by the first temperature sensor 8 is less than 650°C, it is necessary to increase the opening of the first valve and decrease the opening of the second valve to increase the proportion of high-temperature exhaust gas drawn from the incinerator 301 and raise the temperature in the first air duct 203. If the temperature of the mixture in the second air duct 7 has already been adjusted to 550°C or higher, but the temperature measured by the first temperature sensor 8 is 650°C or higher, there is no need to adjust the opening of the first and second valves.

[0049] Using the above method for removing dioxins from fly ash, a test was conducted at a waste incineration plant. Each device was connected, and fly ash samples were taken from the intermediate ash chamber 310 and the ash chamber 313, respectively, for dioxin detection. The specific process conditions and detection results are shown in Table 1 below.

[0050] [Table 1]

[0051] As can be seen from Table 1 above, the airflow in the first air duct 203 is 1000 m³. 3 / h~2000m 3When the ash feeding speed of the star-shaped feeder 12 is 1.2 t / h to 1.6 t / h, the temperature of the mixture sent to the gas powder mixer 4 is 650°C to 696°C, and the temperature of the air returned to the furnace in the second air duct 7 is 550°C to 570°C, the concentration of dioxins in the fly ash can be reduced from 0.481 to 0.593 ng-TEQ / g to within the range of 0.037 to 0.048 ng-TEQ / g. From the above, it can be seen that a very high removal rate of dioxins from fly ash can be obtained under the above process conditions.

[0052] 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 remains above 550°C, and the temperature is measured in the second air duct 7 by the second temperature sensor 10. Based on the temperature measured by the second temperature sensor 10, corresponding control is performed. If the temperature measured by the second temperature sensor 10 is <550°C, the controller 14 increases the temperature in the first air duct 203, i.e., increases the set value of the first temperature sensor 8, and controls the opening of the first damper 101 and the second damper 102 based on the control logic in step S100, thereby increasing the temperature in the second air duct 7. Subsequently, the dioxin-mixed air is returned to the incinerator 301 via the second air duct 7 for combustion, and the dioxins are removed by secondary oxidation in the incinerator 301.

[0053] In this embodiment, the opening of the corresponding valve and the ash feeding speed of the star-shaped feeder 12 can be automatically controlled based on the detection data of the first temperature sensor 8, the second temperature sensor 10, and the particulate matter detector 11. This enables automated control of the system for removing dioxins from fly ash, significantly simplifying the control process. Furthermore, by keeping the desorption temperature of the fly ash within the range of 650°C to 750°C, the desorption rate of dioxins in the fly ash is effectively guaranteed, improving the efficiency of dioxin removal from the fly ash. In addition, most of the dioxins that have not been completely desorbed can be sent back to the incinerator 301 via the second air duct 7, which has an internal temperature of 550°C or higher. This effectively avoids the regeneration of dioxins and prevents secondary contamination.

[0054] The foregoing are merely preferred specific embodiments of the present application, and the scope of protection of the present application is not limited thereto. Any equivalent substitution or modification made by a person skilled in the art based on the technical solutions and improved concepts of the present application within the scope of the art disclosed herein shall be included within the scope of protection of the present application.

[0055] (Note) (Note 1) Includes an intake pipe having a temperature control assembly, one end of the intake pipe is used to connect to an incineration system, The incineration system includes an incinerator, a primary waste heat recovery device, and a secondary waste heat recovery device. The intake pipe includes a first air duct, one end of which is connected to a gas powder mixer, and a first branch air duct for connecting piping between the incinerator and the primary heat recovery unit, and a second branch air duct for connecting piping between the primary heat recovery unit and the secondary heat recovery unit are connected to the other end of the first air duct. The temperature control assembly includes a first damper attached to a first branch air duct and a second damper attached to a second branch air duct. A gas powder mixer is connected to the other end of the intake pipe, and an ash inlet is provided in advance at the end of the intake pipe closest to the gas powder mixer. A gas powder separation assembly is connected to the output terminal of the gas powder mixer. The gas output terminal of the aforementioned gas powder separation assembly is connected to the secondary air duct of the incinerator via a second air duct. A first temperature sensor is attached to the intake pipe. A fan, a second temperature sensor, and a particulate matter detector are attached to the second air duct. The first temperature sensor, fan, second temperature sensor, and particulate matter detector are all electrically connected to the controller. A system for removing dioxins from fly ash, characterized by the following features.

[0056] (Note 2) The first damper and the second damper are both electrically controlled valves and are both electrically connected to a controller. A system for removing dioxins from fly ash as described in Appendix 1, characterized by the features described above.

[0057] (Note 3) The ash inlet is connected to the output terminal of the star-shaped feeder, the input terminal of the star-shaped feeder is used to connect to the ash source, and the star-shaped feeder is electrically connected to the controller. A system for removing dioxins from fly ash as described in Appendix 2, characterized by the features described above.

[0058] (Note 4) The aforementioned gas powder separation assembly includes a first gas powder separator and a second gas powder separator. The input terminal of the first gas powder separator is connected to the output terminal of the gas powder mixer. The input terminal of the second gas powder separator is connected to the gas output terminal of the first gas powder separator. The gas output terminal of the second gas powder separator is connected to the mixed air chamber via the second air duct. A system for removing dioxins from fly ash as described in Appendix 2, characterized by the features described above.

[0059] (Note 5) The end of the second air duct away from the gas powder separation assembly is connected to one input end of the mixed air chamber, the other input end of the mixed air chamber is used to connect to the slag chamber, and the output end of the mixed air chamber is connected to the incinerator. A system for removing dioxins from fly ash as described in Appendix 2, characterized by the features described above.

[0060] (Note 6) A method for removing dioxins from fly ash, applicable to any one of the systems described in Appendix 3 to 5, The process involves starting the fan, adjusting the opening of the first and second dampers based on the data detected by the first temperature sensor, and adjusting the temperature of the mixture sent to the gas powder mixer to 650°C to 750°C. The process involves activating a star-shaped feeder, adjusting the parameters of the gas powder separation assembly based on the detection data from the particulate matter detector, and having a predetermined amount of fly ash carried by the gas output from the gas powder separation assembly. The process includes adjusting the opening of the first and second valves based on the detection data of the second temperature sensor to adjust the temperature of the mixture in the second air duct to 550°C or higher. A method for removing dioxins from fly ash, characterized by the following features.

[0061] (Note 7) The amount of fly ash carried in the gas output from the aforementioned gas powder separation assembly is 5% to 10% of the original amount of fly ash. A method for removing dioxins from fly ash as described in Appendix 6, characterized by the features described herein.

[0062] (Note 8) The airflow rate in the first air duct is 1000 m³ 3 / h~2000m 3 The ash feeding speed of the star-shaped feeder is 1.2 t / h to 1.6 t / h. A method for removing dioxins from fly ash as described in Appendix 6, characterized by the features described herein.

[0063] (Note 9) The mixture of hot air and fly ash in the first air duct has a residence time of 10s to 30s in the gas powder mixer. A method for removing dioxins from fly ash as described in Appendix 6, characterized by the features described herein. [Explanation of Symbols]

[0064] 1. Temperature control assembly 101 First Dump 102 Second Damper 2. Intake pipe 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 system 304 Secondary heat recovery system 305 Slag Room 306 Garbage Pit 307 Primary air duct 308 Exhaust gas pretreatment device 309 Cloth bag type dust collector 310 Relay Ash Room 311 Exhaust gas aftertreatment device 312 Exhaust stack 313 Ash room 4. Gas powder mixer 5 Ash entrance 6. Gas Powder Separation Assembly 601 First Gas Powder Separator 602 Second Gas Powder Separator 7. Second air duct 8. First temperature sensor 9 Fans 10. Second temperature sensor 11. Particulate matter detector 12 star-shaped feeders 13. Mixed air chamber 14 Controllers

Claims

1. Includes an intake pipe having a temperature control assembly, The intake pipe includes a first air duct, a first branch air duct, and a second branch air duct. One end of the intake pipe is connected to the incineration system via the first branch air duct and the second branch air duct, and the other end of the intake pipe is connected to the gas powder mixer via the first air duct. The ash inlet is provided in the first air duct. The first branch air duct is used to connect to the piping between the incinerator and the primary waste heat recovery device, and the second branch air duct is used to connect to the piping between the primary waste heat recovery device and the secondary waste heat recovery device. The incineration system includes the incinerator, the primary waste heat recovery device, and the secondary waste heat recovery device. The temperature control assembly includes a first damper attached to the first branch air duct and a second damper attached to the second branch air duct. A gas powder separation assembly is connected to the output terminal of the gas powder mixer. The gas output terminal of the gas powder separation assembly is connected to the secondary air duct of the incinerator via a second air duct. A first temperature sensor is attached to the intake pipe. A fan, a second temperature sensor, and a particulate matter detector are attached to the second air duct. The first temperature sensor, the fan, the second temperature sensor, and the particulate matter detector are all electrically connected to the controller. A mixture of hot air from the first air duct and fly ash from the ash inlet is sent to the gas powder mixer to desorb dioxins from the fly ash. The dioxin-mixed gas discharged from the gas powder separation assembly is returned to the incinerator via the second air duct to decompose the dioxins. A system for removing dioxins from fly ash, characterized by the following features.

2. The first damper and the second damper are both electrically controlled valves and are both electrically connected to a controller. A system for removing dioxins from fly ash as described in feature 1.

3. The ash inlet is connected to the output terminal of the star-shaped feeder, the input terminal of the star-shaped feeder is used to connect to the ash source, and the star-shaped feeder is electrically connected to the controller. A system for removing dioxins from fly ash as described in feature 2.

4. The gas powder separation assembly includes a first gas powder separator and a second gas powder separator. The input terminal of the first gas powder separator is connected to the output terminal of the gas powder mixer. The input terminal of the second gas powder separator is connected to the gas output terminal of the first gas powder separator. The gas output terminal of the second gas powder separator is connected to the mixed air chamber via the second air duct. A system for removing dioxins from fly ash as described in feature 2.

5. The end of the second air duct away from the gas powder separation assembly is connected to one input end of the mixed air chamber, the other input end of the mixed air chamber is used to connect to the slag chamber, and the output end of the mixed air chamber is connected to the incinerator. A system for removing dioxins from fly ash as described in feature 2.

6. A method for removing dioxins from fly ash, applicable to the system described in claim 3, The process involves starting the fan, adjusting the opening of the first and second dampers based on the data detected by the first temperature sensor, and adjusting the temperature of the mixture sent to the gas powder mixer to 650°C to 750°C. The process involves activating a star-shaped feeder, adjusting the parameters of the gas powder separation assembly based on the detection data from the particulate matter detector, and having a predetermined amount of fly ash carried by the gas output from the gas powder separation assembly. The process includes adjusting the opening of the first and second valves based on the detection data from the second temperature sensor to adjust the temperature of the mixture in the second air duct to 550°C or higher. A method for removing dioxins from fly ash, characterized by the following features.

7. The amount of fly ash carried in the gas output from the aforementioned gas powder separation assembly is 5% to 10% of the original amount of fly ash. The method for removing dioxins from fly ash as described in claim 6.

8. The airflow rate in the first air duct is 1000 m³ ３ / h ~ 2000m ３ The ash feeding speed of the star-shaped feeder is 1.2 t / h to 1.6 t / h. The method for removing dioxins from fly ash as described in claim 6.

9. The mixture of hot air and fly ash in the first air duct is sent to the gas powder mixer, and the residence time of the mixture in the gas powder mixer is 10 s to 30 s. The method for removing dioxins from fly ash as described in claim 6.

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