A smoldering disposal method of chlorine-containing sludge

Abstract

The application belongs to the field of solid waste treatment, and specifically discloses a smoldering disposal method for chlorine-containing sludge, which comprises the following steps: mixing chlorine-containing sludge, calcium-containing combustion-supporting agent and heat storage medium to obtain a mixture; then, performing smoldering treatment on the mixture, and recycling part of the generated flue gas and directly injecting the flue gas into a main combustion zone or a temperature-reducing intermediate zone in the furnace to remove chlorine in the flue gas, while locally supplying oxygen to the main combustion zone to strengthen combustion, wherein the main combustion zone is a region with a temperature of 800-900 DEG C in the furnace, and the temperature-reducing intermediate zone is a region with a temperature of 400-600 DEG C in the furnace. The application takes into account the problems of chlorine escaping and insufficient decomposition of organic chlorine during the smoldering treatment of chlorine-containing sludge, and proposes flue gas recycling injection combined with local oxygen injection, so as to promote the sufficient decomposition of organic chlorine and reduce the generation of dioxins, and meanwhile, the application optimizes the injection position of the flue gas recycling, which can effectively avoid the catalytic formation of dioxins and their precursors from chlorine-containing pollutants.

Description

Technical Field

[0001] This application belongs to the field of solid waste treatment, and more specifically, relates to a method for smoldering disposal of chlorine-containing sludge. Background Technology

[0002] Municipal solid waste disposal, whether through landfill or incineration, generates large amounts of leachate. Leachate sludge, a byproduct of leachate treatment, typically contains significant amounts of toxic, harmful, or environmentally detrimental substances. Currently, landfill is the primary method for disposing of leachate sludge, but this requires large quantities of solidifying agents and carries the risk of secondary pollution after solidification. Thermal treatment is a highly efficient, thorough, and volume-reducing method for solid waste disposal. However, leachate sludge has a high water content, making direct incineration difficult due to heat transfer issues. Furthermore, it requires substantial heat for pre-drying and co-firing, resulting in high energy consumption and costs, and the high temperatures during treatment can generate harmful gases. In particular, excessively high chlorine content can easily generate HCl and dioxins and their precursors during thermal treatment, severely impacting the environment and posing health risks. Therefore, the development of new disposal technologies must balance efficient thermal treatment of leachate sludge with the control of chlorine-containing pollutant emissions.

[0003] Smoldering, as a low-energy and low-cost method for treating high-moisture solid waste, also has unique advantages in treating leachate sludge. For example, CN120868447A proposes a system and method for treating municipal solid waste based on smoldering technology. This system is applicable to the harmless treatment of mixed municipal solid waste and significantly reduces energy consumption compared to traditional incineration. By mixing in a portion of biomass as a combustion aid, self-sustaining smoldering of high-moisture leachate sludge can be achieved. Compared to other treatment methods, smoldering has lower energy consumption and economic costs, generates fewer pollutants, and has a better harmless treatment effect. However, this patent uses spraying alkaline solution to remove chlorine-containing pollutants from flue gas, which mainly suffers from complex equipment and a large footprint. Moreover, harmful substances in the flue gas are easily absorbed by water, increasing treatment costs. Meanwhile, existing technologies are mainly used for chlorine removal in traditional combustion processes. However, the temperature in the core area of ​​smoldering combustion is lower than that of traditional combustion, and there are preheating zones (where pyrolysis mainly occurs) and main combustion zones (where oxidation mainly occurs) at medium and low temperatures. Compared with traditional combustion processes, the following problems exist: (1) When pyrolysis occurs in the preheating zone, volatile chlorine will escape prematurely; (2) The main combustion zone cannot fully decompose organic chlorine into inorganic chlorine, which leads to the catalysis of organic chlorine into dioxins. Consequently, the existing chlorine removal technology and chlorine solidification technology are not ideal when used in smoldering processes. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a smoldering disposal method for chlorine-containing sludge, aiming to solve the problems of chlorine escape and insufficient decomposition of organic chlorine during the smoldering process.

[0005] This application provides a smoldering disposal method for chlorinated sludge, specifically comprising: mixing chlorinated sludge, calcium-containing combustion aid, and heat storage medium to obtain a mixture; then subjecting the mixture to smoldering treatment, and partially circulating and directly injecting the generated flue gas into the main combustion zone or intermediate cooling zone of the furnace to remove chlorine from the flue gas, while simultaneously supplying oxygen locally to the main combustion zone to enhance combustion, wherein the main combustion zone is a region with a furnace temperature of 800℃~900℃, and the intermediate cooling zone is a region with a furnace temperature of 400℃~600℃.

[0006] Compared with the prior art, the technical solution conceived in this application proposes a smoldering treatment for chlorine-containing sludge. Combustion can be enhanced by flue gas circulation combined with local oxygen injection, thereby promoting the decomposition of organic chlorine in the main combustion zone.

[0007] As a further preferred embodiment, when the chlorine content in the dry basis of the chlorine-containing sludge is less than 1%, the injection position of the circulating flue gas is located within 3 cm above and below the stable smoldering front; when the chlorine content in the dry basis of the chlorine-containing sludge is greater than 1%, the injection position of the circulating flue gas is located in the area 6 cm to 8 cm below the stable smoldering front.

[0008] As a further preferred option, chlorine-containing sludge, calcium-containing combustion aid, and heat storage medium are mixed in a mass ratio of (1-2): (1-3): (5-8) to obtain a mixture.

[0009] As a further preferred embodiment, the calcium-containing combustion aid includes one or more of soybean straw, corn straw, sweet potato, and cabbage stems and leaves.

[0010] As a further preferred embodiment, when the chlorine content in the dry basis of the chlorine-containing sludge is above 1%, the mixture further includes a calcium-based solidifying agent, which includes one or more of red mud, carbide slag, animal bones, and eggshells, and the mixture contains 50wt% to 65wt% of the calcium-based solidifying agent.

[0011] As a further preferred embodiment, the system calorific value of the mixture is in the range of 1.2 MJ / kg to 2.5 MJ / kg.

[0012] As a further preferred option, the ignition temperature for smoldering treatment is 250℃~350℃, and the Darcy velocity of the intake air is 2cm / s~5cm / s.

[0013] As a further preferred option, the oxygen injection point is located within 3 cm above and below the stable smoldering front, and the oxygen injection flow rate is 20% to 40% of the circulating flue gas flow rate.

[0014] As a further preferred option, 30% to 60% of the flue gas is returned to the furnace for recirculation.

[0015] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: 1. Considering the problems of chlorine escape and insufficient decomposition of organic chlorine during the smoldering treatment of chlorine-containing sludge, this application proposes flue gas recirculation injection combined with local oxygen injection, which can promote the full decomposition of organic chlorine and reduce the formation of dioxins. At the same time, by optimizing the injection position of flue gas recirculation, this application can effectively prevent chlorine-containing pollutants from being catalyzed to form dioxins and their precursors. 2. In particular, this application optimizes the injection location of circulating flue gas based on the different chlorine content in the dry basis of chlorine-containing sludge, which can avoid the formation of dioxins and their precursors, and increase the solidification ratio of inorganic chlorine in the flue gas, further avoiding the release of chlorine. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of the smoldering disposal method for chlorine-containing sludge provided in the embodiments of this application; Figure 2 This is a schematic diagram of the smoldering treatment device for chlorine-containing sludge provided in the embodiments of this application.

[0017] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Feeding assembly, 2-Smoldering reactor, 21-Feed inlet, 22-Flue gas outlet, 23-Flue gas inlet, 24-Oxygen inlet, 25-Discharge outlet, 26-Air inlet, 3-Oxygen supply assembly, 4-Air inlet assembly, 5-Heating element, 6-Flue gas circulation assembly, 7-Flue gas purification assembly. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] like Figure 1 As shown, this application provides a smoldering disposal method for chlorinated sludge, specifically: mixing chlorinated sludge, calcium-containing combustion aid, and heat storage medium to obtain a mixture; then subjecting the mixture to smoldering treatment, and partially circulating and directly injecting the generated flue gas into the main combustion zone or intermediate cooling zone of the furnace to remove chlorine from the flue gas, while simultaneously supplying oxygen to the main combustion zone to enhance combustion, wherein the main combustion zone is the area with a furnace temperature of 800℃~900℃, and the intermediate cooling zone is the area with a furnace temperature of 400℃~600℃.

[0020] This application considers that during the smoldering treatment of chlorine-containing sludge, the preheating zone can lead to premature release of volatile chlorine, and the low combustion temperature in the main combustion zone can prevent the complete decomposition of organic chlorine into inorganic chlorine. Therefore, it proposes flue gas recirculation combined with localized oxygen injection during the smoldering treatment of chlorine-containing sludge. On the one hand, flue gas recirculation effectively prevents chlorine release, increases the decomposition rate of organic chlorine to reduce dioxin formation, and facilitates better absorption and solidification of chlorine. On the other hand, localized oxygen injection enhances combustion and improves combustion stability. This application proposes flue gas recirculation combined with localized oxygen injection for the special application scenario of smoldering. Conventional heat treatment methods with localized oxygen supply can lead to localized overheating, because traditional combustion already takes place under high temperature and strong oxidation conditions. If localized oxygen injection is used in this situation, the local oxygen concentration will rise sharply, resulting in excessively intense combustion.

[0021] Figure 2 The smoldering apparatus used in this application includes a feeding assembly 1, a smoldering reactor 2, a flue gas purification assembly 7, an air supply assembly 4, a flue gas recirculation assembly 6, and an oxygen supply assembly 3, wherein: Feeding assembly 1 is used to mix chlorine-containing sludge, calcium-containing combustion aid and heat storage medium to obtain a mixture; The smoldering reactor 2 has an inlet 21 at the top and is connected to the feeding assembly 1 to feed the mixture into the smoldering reactor 2 for smoldering treatment. At the same time, the smoldering reactor 2 has a flue gas outlet 22 at the top and is connected to the flue gas purification assembly 7 to purify the discharged flue gas. The smoldering reactor 2 has a flue gas inlet 23 and an oxygen inlet 24 in the middle to realize flue gas circulation and local oxygen injection. The smoldering reactor 2 has an outlet 25 and an air inlet 26 at the bottom. The outlet 25 is used to discharge the ash after combustion, and the air inlet 26 is used to introduce air. The bottom of the smoldering reactor 2 is also equipped with a heating element 5 to heat the mixture at the bottom to reach the ignition temperature. The air supply assembly 4 is connected to the air inlet 26 of the smoldering reactor 2 and is used to introduce air when the lower layer mixture reaches the ignition temperature in order to maintain the smoldering reaction. One end of the flue gas recirculation assembly 6 is connected to the flue gas outlet 22 of the smoldering reactor 1, and the other end is connected to the flue gas inlet 23 of the smoldering reactor 2, for sending part of the flue gas generated by smoldering back into the furnace. The oxygen supply assembly 3 is connected to the oxygen inlet 24 of the smoldering reactor 2 for local oxygen supply to enhance combustion.

[0022] The smoldering reactor 2 can be divided into four zones from top to bottom: a pyrolysis zone, a main combustion zone, an initial cooling zone, a mid-cooling zone, and a final cooling zone. The main combustion zone is the area where the smoldering reaction mainly occurs, specifically the area with a furnace temperature of 800℃ to 900℃. The pyrolysis zone is the area above the main combustion zone where the material is heated by the temperature of the main combustion zone below and undergoes a pyrolysis reaction. The initial cooling zone is the area below the main combustion zone where the material has just begun to cool, specifically the area with a furnace temperature of 600℃ to 800℃. In the mid-cooling zone, the material continues to cool, specifically the area with a furnace temperature of 400℃ to 600℃. In the final cooling zone, the material continues to cool, specifically the area with a furnace temperature below 400℃.

[0023] Traditional combustion processes primarily utilize flue gas recirculation to suppress thermal NO. x The generation of chlorine-containing pollutants mainly involves directly mixing the circulating flue gas into the primary or secondary air, which then enters the furnace from the bottom along with the supplied air. However, during smoldering combustion, if the circulating flue gas is mixed with air from the bottom, chlorine-containing pollutants are easily catalyzed to form dioxins and their precursors at the temperature at the end of the cooling period, thus affecting the treatment effect of the main combustion zone. Therefore, this application proposes to directly inject the flue gas into the main combustion zone or the mid-cooling zone of the furnace. At the temperature in this zone, the calcium-based curing agent has the best effect in absorbing and curing inorganic chlorine, and chlorine-containing organic matter will not be further catalyzed and oxidized to form dioxins at this temperature.

[0024] Furthermore, chlorinated sludge, calcium-containing combustion aid, and heat storage medium are mixed in a mass ratio of (1-2): (1-3): (5-8) to obtain a mixture. When the proportion of chlorinated sludge is too high, the total calorific value of the mixture will decrease, affecting the stability of the smoldering process. When the amount of chlorinated sludge is too low, the treatment capacity decreases while the economic cost increases. Controlling the calcium-containing combustion aid within a certain range is to maintain the temperature of the main combustion zone of the smoldering process at a predetermined value. Controlling the proportion of the heat storage medium is to ensure that the mixture has a suitable porosity. Among them, the calcium-containing combustion aid includes one or more of legumes, corn stalks, sweet potatoes, and cabbage stems and leaves, and the heat storage medium includes quartz sand, ceramic balls, etc.

[0025] Furthermore, when the chlorine content in the dry basis of the chlorine-containing sludge is above 1%, the mixture also includes a calcium-based solidifying agent. By adding the calcium-based solidifying agent, inorganic chlorine can be absorbed and solidified. The calcium-based solidifying agent includes one or more of red mud, carbide slag, animal bones, and eggshells. The mixture contains 50wt% to 65wt% of the calcium-based solidifying agent, thus achieving both economic efficiency and effective solidification of chlorine-containing pollutants.

[0026] Furthermore, when the chlorine content in the dry basis of the chlorine-containing sludge is less than 1%, considering that no calcium-based solidifying agent has been added, the injection point of the circulating flue gas is located within 3 cm above and below the stable smoldering front. This area is the main combustion zone of smoldering (800℃~900℃). Directly injecting the circulating flue gas into this area can make full use of the high temperature and high oxygen environment generated by the self-sustaining smoldering process, so that organic chlorine can be converted into inorganic chlorine that is easier to absorb and treat.

[0027] When the chlorine content in the dry basis of chlorine-containing sludge is above 1%, the injection point of the circulating flue gas is located in the region 6cm to 8cm below the stable smoldering front. This region is the mid-cooling zone of smoldering (500℃ to 600℃). At this temperature, the calcium-based solidifier has the best effect in absorbing and solidifying inorganic chlorine. However, the absorption efficiency of the calcium-based solidifier is not high when the initial cooling temperature is too high. Therefore, injecting the circulating flue gas directly into this region can solidify a large amount of inorganic chlorine in this region, reducing the chlorine-containing pollutants in the flue gas. Furthermore, the solidified smoldering ash is directly discharged without passing through the high-temperature region, thus avoiding the secondary release of chlorine-containing products after solidification. Then, the circulating flue gas rises into the high-temperature main combustion zone, making full use of the high-temperature and high-oxygen environment generated by the self-sustaining smoldering process, so that organic chlorine is converted into inorganic chlorine that is easier to absorb and treat.

[0028] Furthermore, the system calorific value of the mixture is in the range of 1.2 MJ / kg to 2.5 MJ / kg to ensure the stable progress of the flameless combustion process and to control the temperature of the smoldering main combustion zone to be stable at 800~900℃.

[0029] Furthermore, the ignition temperature for the smoldering treatment is 250℃~350℃. Once the ignition temperature is reached, heating is immediately stopped and air is introduced. The Darcy flow rate of the air intake is 2cm / s~5cm / s, thereby maintaining the temperature of the reaction zone between 800℃~900℃ to ensure optimal smoldering reaction conditions.

[0030] Furthermore, the oxygen injection point is located within 3 cm above and below the stable smoldering front, and the oxygen injection flow rate is 20% to 40% of the circulating flue gas flow rate, thereby enabling the pollutants in the flue gas to be fully combusted secondary while maintaining a low economic cost.

[0031] Furthermore, 30% to 60% of the flue gas is returned to the furnace for recirculation, thereby allowing harmful substances in the flue gas to be burned back into the furnace.

[0032] The technical solutions provided in this application will be further described below with reference to specific embodiments.

[0033] Example 1 S1 chlorinated sludge is landfill leachate sludge with a moisture content of 80%. The chlorine content of the sludge on a dry basis is approximately 0.5%. The calcium-containing combustion aid is soybean straw, and the heat storage medium is quartz sand with a particle size of 16-26 mesh. The landfill leachate sludge, soybean straw, and quartz sand are thoroughly mixed in a mass ratio of 1:1:8 to obtain a mixture. S2 fills the smoldering reactor with the mixture. The reactor has a diameter of 15 cm and a height of 50 cm. The smoldering front is stabilized at 32 cm ± 1 cm from the bottom of the reactor by discharging the bottom material every 5 minutes. The injection position of the circulating flue gas is the main smoldering combustion zone. The injection position of oxygen is consistent with the injection height of the flue gas circulation, located in the main smoldering combustion zone. S3 preheats the mixture at the bottom to 350 °C, then shuts off the heating element 5 and immediately starts the air supply assembly 4, oxygen supply assembly 3, and flue gas recirculation assembly 6 to initiate the self-sustaining smoldering process. The Darcy flow rate of the intake air is 5 cm / s, the flue gas recirculation rate is 30%, and the oxygen injection rate is 3 L / min, so that the peak temperature of smoldering is maintained at 826 °C.

[0034] Under these conditions, the organic chloride content in the flue gas was 23 ppm, the inorganic chloride content was 217 ppm, and the chlorine retention rate in the smoldering ash was 23%. When the flue gas recirculation was not activated, the organic chloride content in the flue gas was 72 ppm, the inorganic chloride content was 168 ppm, and the chlorine retention rate in the smoldering ash was 21%.

[0035] Example 2 S1 chlorinated sludge is landfill leachate sludge with a moisture content of 80%. The chlorine content of the sludge on a dry basis is approximately 1%. The calcium-containing combustion aid is soybean straw, and the heat storage medium is quartz sand with a particle size of 16-26 mesh. The landfill leachate sludge, soybean straw, and quartz sand are thoroughly mixed in a mass ratio of 2:3:5 to obtain a mixture. S2 fills the smoldering reactor with the mixture. The reactor has a diameter of 15 cm and a height of 50 cm. The smoldering front is stabilized at 32 cm ± 1 cm from the bottom of the reactor by discharging the bottom material every 5 minutes. The injection position of the circulating flue gas is the main smoldering combustion zone. The injection position of oxygen is consistent with the injection height of the flue gas circulation, located in the main smoldering combustion zone. S3 preheats the mixture at the bottom to 350 °C, then shuts off the heating element 5 and immediately starts the air supply assembly 4, oxygen supply assembly 3, and flue gas recirculation assembly 6 to initiate the self-sustaining smoldering process. The Darcy flow rate of the intake air is 5 cm / s, the flue gas recirculation rate is 30%, and the oxygen injection rate is 3 L / min, so that the peak temperature of smoldering is maintained at 887 °C.

[0036] Under these conditions, the organic chloride content in the flue gas was 6 ppm, and the inorganic chloride content was... The concentration of chlorine in the flue gas was 375 ppm, with a chlorine retention rate of 37% in the smoldering ash residue. When flue gas recirculation was not activated, the organic chloride content in the flue gas was 162 ppm, the inorganic chloride content was 198 ppm, and the chlorine retention rate in the smoldering ash residue was 29%.

[0037] Example 3 S1 chlorinated sludge is landfill leachate sludge with a moisture content of 80%, and the chlorine content on a dry basis is approximately 2%. The calcium-containing combustion aid is soybean straw, and the heat storage medium is quartz sand with a particle size of 16-26 mesh. The landfill leachate sludge, soybean straw, quartz sand, and calcium-based solidifying agent are thoroughly mixed in a mass ratio of 5:5:16:4 to obtain a mixture. S2 fills the smoldering reactor with the mixture. The reactor has a diameter of 15 cm and a height of 50 cm. The smoldering front is stabilized at 32 cm ± 1 cm from the bottom of the reactor by discharging the bottom material every 5 minutes. The circulating flue gas is injected in the middle of the cooling process, and the oxygen is injected in the main combustion zone of the smoldering. S3 preheats the mixture at the bottom to 350 °C, then shuts off the heating element 5 and immediately starts the air supply assembly 4, oxygen supply assembly 3, and flue gas recirculation assembly 6 to initiate the self-sustaining smoldering process. The Darcy flow rate of the intake air is 5 cm / s, the flue gas recirculation rate is 30%, and the oxygen injection rate is 3 L / min, so that the peak temperature of smoldering is maintained at 858 °C.

[0038] Under these conditions, the organic chloride content in the flue gas was 13 ppm, the inorganic chloride content was 36 ppm, and the chlorine retention rate in the smoldering ash was 78%. When the flue gas recirculation was not activated, the organic chloride content in the flue gas was 193 ppm, the inorganic chloride content was 376 ppm, and the chlorine retention rate in the smoldering ash was 26%.

[0039] Example 4 S1 chlorinated sludge is landfill leachate sludge with a moisture content of 80%. The chlorine content of the sludge on a dry basis is approximately 5%. The calcium-containing combustion aid is soybean straw, and the heat storage medium is quartz sand with a particle size of 16-26 mesh. The landfill leachate sludge, soybean straw, and quartz sand are thoroughly mixed in a mass ratio of 2:3:6:4 to obtain a mixture. S2 fills the smoldering reactor with the mixture. The reactor has a diameter of 15 cm and a height of 50 cm. The smoldering front is stabilized at 32 cm ± 1 cm from the bottom of the reactor by discharging the bottom material every 5 minutes. The circulating flue gas is injected in the middle of the cooling process, and the oxygen is injected in the main combustion zone of the smoldering. S3 preheats the mixture at the bottom to 350 °C, then shuts off the heating element 5 and immediately starts the air supply assembly 4, oxygen supply assembly 3, and flue gas recirculation assembly 6 to initiate the self-sustaining smoldering process. The Darcy flow rate of the intake air is 5 cm / s, the flue gas recirculation rate is 30%, and the oxygen injection rate is 3 L / min, so that the peak temperature of smoldering is maintained at 886 °C.

[0040] Under these conditions, the organic chloride content in the flue gas was 16 ppm, the inorganic chloride content was 27 ppm, and the chlorine retention rate in the smoldering ash was 83%. When the flue gas recirculation was not activated, the organic chloride content in the flue gas was 272 ppm, the inorganic chloride content was 686 ppm, and the chlorine retention rate in the smoldering ash was 28%.

[0041] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0042] Furthermore, throughout this specification, references to "an embodiment"; "an embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, and similar language, may, but not necessarily, refer to the same embodiment.

[0043] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for smoldering disposal of chlorine-containing sludge, characterized in that, The smoldering treatment method specifically involves: mixing chlorine-containing sludge, calcium-containing combustion aid, and heat storage medium to obtain a mixture; then subjecting the mixture to smoldering treatment, and partially circulating and directly injecting the generated flue gas into the main combustion zone or intermediate cooling zone of the furnace to remove chlorine from the flue gas; simultaneously supplying oxygen locally to the main combustion zone to enhance combustion, wherein the main combustion zone is the area with a furnace temperature of 800℃~900℃, and the intermediate cooling zone is the area with a furnace temperature of 400℃~600℃.

2. The smoldering disposal method as described in claim 1, characterized in that, When the chlorine content in the dry basis of the chlorine-containing sludge is less than 1%, the injection point of the circulating flue gas is located within 3 cm above and below the stable smoldering front. When the chlorine content in the dry basis of the chlorine-containing sludge is greater than 1%, the injection point of the circulating flue gas is located 6 cm to 8 cm below the stable smoldering front.

3. The smoldering disposal method as described in claim 1, characterized in that, Chlorine-containing sludge, calcium-containing combustion aid and heat storage medium are mixed in a mass ratio of (1-2): (1-3): (5-8) to obtain a mixture.

4. The smoldering disposal method as described in claim 1, characterized in that, The calcium-containing combustion aid includes one or more of legumes, corn stalks, sweet potatoes, and cabbage stems and leaves.

5. The smoldering disposal method as described in claim 1, characterized in that, When the chlorine content in the dry basis of the chlorine-containing sludge is above 1%, the mixture also includes a calcium-based solidifying agent, which includes one or more of red mud, carbide slag, animal bones, and eggshells, and the mixture contains 50wt% to 65wt% of the calcium-based solidifying agent.

6. The smoldering disposal method as described in claim 1, characterized in that, The system calorific value of the mixture is in the range of 1.2 MJ / kg to 2.5 MJ / kg.

7. The smoldering disposal method as described in claim 1, characterized in that, The ignition temperature for smoldering treatment is 250℃~350℃, and the Darcy velocity of the intake air is 2cm / s~5cm / s.

8. The smoldering disposal method as described in claim 1, characterized in that, The oxygen injection point is located within 3 cm above and below the stable smoldering front, and the oxygen injection flow rate is 20% to 40% of the circulating flue gas flow rate.

9. The smoldering treatment method according to any one of claims 1 to 8, characterized in that, 30% to 60% of the flue gas is returned to the furnace for recirculation.

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