Heavy metal contaminated soil smoldering tail end closed cycle treatment equipment and method

Abstract

The invention relates to heavy metal contaminated soil smoldering tail end closed cycle treatment equipment and method, and belongs to the field of soil treatment. The equipment comprises a smoldering chamber (11), a passivation chamber (2), a flue gas purification chamber (3) and an ash bucket (8), the passivation chamber (2) is arranged at the upper end of the smoldering chamber (11) in a communicating mode, the flue gas purification chamber (3) is arranged on the outer side in a sleeving mode, and the ash bucket (8) is arranged at the lower end in a communicating mode. The method comprises the steps that S1, agriculture and forestry solid waste and heavy metal contaminated soil are dried, crushed, screened and mixed, and the mixture is placed in a passivation chamber (2); s2, adding water into another heavy metal contaminated soil, and then putting the soil into a flue gas purification chamber (3); s3, after the open fire is ignited, the open fire is extinguished; s4, intermittently inducing air; and S5, ash and slag are fully mixed. The agriculture and forestry solid waste and the heavy metal soil are mixed for smoldering, generated gas and heat act on the heavy metal soil, and the treatment cost is reduced. The problems that agriculture and forestry solid waste is difficult to treat, and heavy metal contaminated soil is high in treatment difficulty and high in cost are solved.

Description

Technical Field

[0001] The invention relates to a device and a method for treating smoldering end closed cycle of heavy metal polluted soil, belonging to the field of soil treatment. Background Art

[0002] In today's environment, the problem of heavy metal contamination of soil is becoming increasingly serious. Heavy metals in soil mainly come from industrial emissions, mining, agricultural fertilizer and pesticide application, and traffic exhaust emissions. Long-term human activities have caused heavy metals in the soil to accumulate continuously, exceeding the natural background value. These heavy metals include cadmium, mercury, lead, chromium, arsenic, etc. They are difficult to degrade in the soil, and are persistent and bioaccumulative. Once the soil is contaminated by heavy metals, it will not only affect the fertility and ecological function of the soil, but also be transmitted through the food chain, posing a potential threat to human health and the ecological environment.

[0003] At present, the research and application of heavy metal contaminated soil treatment has made certain progress. In terms of research, many scientific research institutions and scholars are committed to exploring efficient and environmentally friendly treatment technologies, such as chemical leaching, phytoremediation, and microbial remediation. The chemical leaching method washes heavy metals out of the soil by injecting specific leaching agents into the soil; the phytoremediation method uses specific hyperaccumulators to absorb heavy metals in the soil; the microbial remediation method relies on microorganisms with heavy metal resistance to change the form of heavy metals or reduce their toxicity. In terms of application status, some regions have begun to try to use these technologies for soil remediation, but due to limitations such as cost and technical maturity, large-scale application still faces challenges. However, with the continuous advancement and innovation of technology, the prospects for heavy metal contaminated soil treatment are worth looking forward to.

[0004] So far, there are no reports on the use of smoldering agricultural and forestry solid waste to treat heavy metal contaminated soil. However, how to combine the treatment of agricultural and forestry solid waste with heavy metal contaminated soil to achieve in situ, low-cost and high-efficiency treatment of heavy metal contaminated soil has become a key issue in the fields of environmental protection and agriculture, and is also a new challenge faced by researchers. Summary of the invention

[0005] The technical problems to be solved by the present invention are the difficulty in high value-added resource treatment of agricultural and forestry solid wastes and the difficulty, high cost and poor effect of treating heavy metal contaminated soil.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a heavy metal contaminated soil smoldering end closed-loop treatment equipment, including a smoldering chamber, a passivation chamber, a flue gas purification chamber and an ash hopper, the passivation chamber is connected and arranged at the upper end of the smoldering chamber, and a grille is arranged at the connection point, the flue gas purification chamber is sleeved on the outside of the smoldering chamber and the passivation chamber, and the ash hopper is connected and arranged at the lower end of the flue gas purification chamber, and a plurality of grate bars are arranged at intervals at the connection point, and a plurality of resistance wires are arranged at intervals at the lower end of the smoldering chamber.

[0007] Wherein, in the above device, air supply pipes are arranged at intervals on the side walls of the flue gas purification chamber, and an air suction pump is arranged at the end of the air supply pipe away from the flue gas purification chamber.

[0008] Wherein, the resistance wires at the lower end of the smoldering chamber in the above device are distributed in parallel, and the spacing between adjacent resistance wires is 1 to 3 cm.

[0009] The holes of the grid at the connection between the smoldering chamber and the passivation chamber in the above device are evenly distributed, and the hole diameter is 0.4 to 1 cm. 2 .

[0010] Among them, the passivation chamber in the above device is provided with a soil inlet pipe on the top, the flue gas purification chamber is provided with a soil inlet pipe B on the top, and the smoldering chamber is provided with a feed pipe on the top, and the feed pipe passes through the flue gas purification chamber away from the smoldering chamber end.

[0011] Among them, in the above device, at least one of the soil inlet pipe A, soil inlet pipe B and feed pipe is provided with a one-way plate.

[0012] A method for treating heavy metal contaminated soil smoldering in a closed cycle, comprising any of the above-mentioned treatment equipment, and the steps are as follows:

[0013] S1. Dry and crush the agricultural and forestry solid waste and a portion of heavy metal contaminated soil respectively, and select the particles with a size less than 50 mesh and mix them in a ratio of 1 to 5:1; place the mixture in a passivation chamber; and place the agricultural and forestry solid waste with a size greater than 50 mesh in a smoldering chamber;

[0014] S2. Add water to another part of the heavy metal contaminated soil to make its moisture content 30% to 45%, and place the moist heavy metal contaminated soil in the flue gas purification chamber;

[0015] S3. Use open flame to ignite the agricultural and forestry solid waste in the smoldering chamber. The ignition time is 1 to 5 minutes, and then extinguish the open flame;

[0016] S4. Intermittent ventilation is carried out in the flue gas purification room. The ventilation interval is 15-30 minutes / time, 0.5-2 minutes per time, and the air volume is 0.01-0.1m 3 / s;

[0017] S5. Fully mix the ash produced in the ash hopper.

[0018] Wherein, the agricultural and forestry solid waste in the above method is at least one of corn stalks, bean stalks, rice straw, potato stalks, tobacco stalks, dead grass and dead branches and leaves.

[0019] Wherein, the heavy metal contaminated soil in the above method is one of As contaminated soil, Cr contaminated soil, Cd contaminated soil, Mn contaminated soil, Pb contaminated soil and Zn contaminated soil, and the heavy metal content is 0.1 mg / Kg to 1.5 mg / Kg.

[0020] Wherein, in the above method, the moisture content of the agricultural and forestry solid waste after drying in step S1 is less than 10%, and the moisture content of the heavy metal contaminated soil is 5% to 10%.

[0021] The beneficial effects of the present invention are as follows: the present invention uses agricultural and forestry solid waste generated in agricultural production activities as the main raw material for the treatment of heavy metal contaminated soil. A large amount of heat and smoke will be generated during the smoldering process of agricultural and forestry solid waste. Smoldering is incomplete combustion. The smoke will contain fine carbon particles, CO, VOCs, CH4, etc. The heat generated acts on the heavy metal contaminated soil, which will activate the heavy metals in the soil and mineralize them. The reducing gas in the smoke will reduce the heavy metal ions and adsorb the carbon particles. The organic gas will complex with the reduced heavy metals and carbon particles to form a stable mineral structure. After the metal ions are reduced, they are in a state that is difficult for crops to utilize, thus avoiding the absorption and enrichment of crops and ensuring the food safety of crops.

[0022] From an environmental protection perspective, this method uses agricultural and forestry solid waste as the only raw material and is an in-situ treatment, which realizes the large-scale resource processing of agricultural and forestry solid waste and reduces the pollution risk of agricultural and forestry solid waste to the ecological environment. The use of smoldering treatment technology can greatly reduce cost investment; the flue gas generated by smoldering is filtered through heavy metal contaminated soil, which realizes the reuse of valuable components in the flue gas and reduces the pollution risk of smoldering flue gas. The entire process achieves clean production.

[0023] From the perspective of sustainable development, this method has important strategic significance. On the one hand, this method can realize the resource utilization of agricultural and forestry solid waste, reduce pollution to the environment, and meet the strategic requirements of national sustainable development. On the other hand, this method can provide an efficient treatment path for heavy metal contaminated soil, reduce treatment costs, and promote the sustainable development of agriculture. In addition, this method can also drive the development of related industries, such as solid waste treatment industry and agriculture, and create more employment opportunities and economic benefits.

[0024] The heavy metal contaminated soil smoldering end closed cycle treatment technology and equipment process of the present invention are simple, and the raw material cost is low, and the high added value resource utilization of agricultural and forestry solid waste can be realized. The heavy metal solidification stabilization efficiency in the heavy metal contaminated soil is greater than 95%, the carbon content of the treated soil is greater than 25%, the water retention rate is greater than 78%, the soil density is 2.1-3.6g / cm3, the N content is 0.3%-0.9%, the P content is 1.4%-2.3%, and the K content is 4.1%-5.6%. The present invention can not only solve the problem of agricultural and forestry solid waste treatment, but also provide a feasible and low-cost application path for the restoration and treatment of heavy metal contaminated soil, realize the recycling of resources, and has broad development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the device structure of the present invention;

[0026] Figure 2 The effect of As and Cr contaminated soil smoldering end closed cycle treatment;

[0027] Figure 3 The end-stage closed-loop treatment effect of smoldering of Cd and Mn contaminated soil;

[0028] Figure 4 The end-stage closed-loop treatment effect of smoldering soil contaminated by Pb and Zn.

[0029] Markings in the figure are: 1 is soil inlet pipe A, 2 is passivation chamber, 3 is flue gas purification chamber, 4 is resistance wire, 5 is suction pump, 6 is grate bar, 7 is tripod, 8 is ash hopper, 9 is power supply, 10 is air supply pipe, 11 is smoldering chamber, 12 is feed pipe, 13 is grille, 14 is soil inlet pipe B, and 15 is one-way plate. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings.

[0031] like Figures 1 to 4As shown, a heavy metal contaminated soil smoldering end closed cycle treatment equipment of the present invention comprises a smoldering chamber 11, a passivation chamber 2, a flue gas purification chamber 3 and an ash hopper 8, wherein the passivation chamber 2 is connected to the upper end of the smoldering chamber 11, and a grille 13 is provided at the connection, the flue gas purification chamber 3 is sleeved outside the smoldering chamber 11 and the passivation chamber 2, and the ash hopper 8 is connected to the lower end of the flue gas purification chamber 3, and a plurality of furnace bars 6 are arranged at intervals at the connection, and a plurality of resistance wires 4 are arranged at intervals at the lower end of the smoldering chamber 11. It can be understood by those skilled in the art that the present device places the smoldering chamber 11 below the passivation chamber 2, separated by a porous grille 13; and the ash hopper 8 is located below the smoldering chamber 11, which is conducive to collecting the ash produced by the smoldering. The flue gas purification chamber 3 is sleeved outside the smoldering chamber 11 and the passivation chamber 2, and is located above the ash hopper 8, and a plurality of furnace bars 6 are arranged at intervals at the connection. A plurality of resistance wires 4 are arranged at intervals at the lower end of the smoldering chamber 11, and the resistance wires 4 are electrically connected to the power supply 9 to achieve the purpose of igniting agricultural and forestry solid waste. Preferably, the processing materials used in the smoldering chamber 11, the passivation chamber 2, the flue gas purification chamber 3 and the ash hopper 8 are nickel-based alloys, ceramic materials, and brown corundum high-temperature resistant materials. Since the ash hopper 8 is a hollow truncated cone structure, in order to maintain the overall stability of the ash hopper 8, the device is connected to a tripod 7 on the side wall of the ash hopper 8.

[0032] Preferably, in the above device, air supply pipes 10 are arranged at intervals on the side walls of the flue gas purification chamber 3, and an air suction pump 5 is arranged at the end of the air supply pipe 10 away from the flue gas purification chamber 3. It can be understood by those skilled in the art that in order to ensure that the agricultural and forestry solid waste continues to smolder without extinguishing, the device preferably introduces air or oxygen into the flue gas purification chamber 3 at regular intervals. In order to facilitate the operation of the device, air supply pipes 10 are preferably arranged at intervals on the side walls of the flue gas purification chamber 3, and an air suction pump 5 is arranged at the other end of the air supply pipe 10, and the purpose of intermittent air induction is achieved by controlling the start and stop of the air suction pump 5.

[0033] Preferably, the resistance wires 4 at the lower end of the smoldering chamber 11 in the above device are distributed in parallel, and the spacing between adjacent resistance wires 4 is 1 to 3 cm. It can be understood by those skilled in the art that in order to prevent the agricultural and forestry solid waste in the smoldering chamber 11 from continuing to smolder and not all falling into the ash hopper 8 after burning, the present device actually preferably controls the spacing of the resistance wires 4, specifically, the resistance wires 4 at the lower end of the smoldering chamber 11 are distributed in parallel, and the spacing between adjacent resistance wires 4 is 1 to 3 cm.

[0034] Preferably, the holes of the grid 13 at the connection between the smoldering chamber 11 and the passivation chamber 2 in the above device are evenly distributed, and the hole diameter is 0.4 to 1 cm. 2 Those skilled in the art will understand that, in order to facilitate ventilation and prevent all the moist heavy metal contaminated soil from falling into the ash hopper 8, the present device actually prefers a structure of the grille 13, specifically, preferably the holes of the grille 13 at the connection between the smoldering chamber 11 and the passivation chamber 2 are evenly distributed, and the hole diameter is 0.4 to 1 cm.2 .

[0035] Preferably, in the above device, a soil inlet pipe A1 is provided at the upper part of the passivation chamber 2, a soil inlet pipe B14 is provided at the upper part of the flue gas purification chamber 3, a feed pipe 12 is provided at the upper part of the smoldering chamber 11, and the feed pipe 12 passes through the flue gas purification chamber 3 away from the end of the smoldering chamber 11. It can be understood by those skilled in the art that, in order to facilitate the addition of heavy metal contaminated soil into the passivation chamber 2 and the flue gas purification chamber 3, respectively, the present device is preferably provided with a soil inlet pipe A1 and a soil inlet pipe B14, and the soil inlet pipe A1 and the soil inlet pipe B14 are respectively arranged at the upper part of the passivation chamber 2 and the upper part of the flue gas purification chamber 3, preferably arranged at an angle. At the same time, in order to facilitate the addition of agricultural and forestry solid waste to the smoldering chamber 11, it is actually preferably provided with a feed pipe 12 at the upper part of the smoldering chamber 11, and the feed pipe 12 passes through the flue gas purification chamber 3 away from the end of the smoldering chamber 11.

[0036] Preferably, in the above device, at least one of the soil inlet pipe A1, soil inlet pipe B14 and feed pipe 12 is provided with a one-way plate 15. It can be understood by those skilled in the art that, in order to prevent the smoke from flowing back along the soil inlet pipe A1, soil inlet pipe B14 and feed pipe 12, the device preferably has a one-way plate 15 in at least one of the soil inlet pipe A1, soil inlet pipe B14 and feed pipe 12.

[0037] A method for treating heavy metal contaminated soil smoldering in a closed cycle, comprising any of the above-mentioned treatment equipment, and the steps are as follows:

[0038] S1, drying and crushing agricultural and forestry solid waste and a portion of heavy metal contaminated soil respectively, and screening out particles with a size less than 50 mesh and mixing them in a ratio of 1 to 5:1; placing the mixture in a passivation chamber 2; placing agricultural and forestry solid waste with a size greater than 50 mesh in a smoldering chamber 11;

[0039] S2, adding water to another part of the heavy metal contaminated soil to make its moisture content 30% to 45%, and placing the wet heavy metal contaminated soil in the flue gas purification chamber 3;

[0040] S3, using an open flame to ignite the agricultural and forestry solid waste in the smoldering chamber 11, the ignition time is 1 to 5 minutes, and then extinguishing the open flame;

[0041] S4: Intermittent ventilation is carried out in the flue gas purification chamber 3. The ventilation interval is 15 to 30 minutes per time, 0.5 to 2 minutes per time, and the air volume is 0.01 to 0.1 m 3 / s;

[0042] S5. Fully mix the ash residue produced in the ash hopper 8. It can be understood by those skilled in the art that this method mainly uses agricultural and forestry solid waste as the main raw material for the treatment of heavy metal contaminated soil. A large amount of heat and flue gas will be generated during the smoldering of agricultural and forestry solid waste. Smoldering is incomplete combustion. The flue gas will contain fine carbon particles, CO, VOCs, CH4, etc. The heat generated acts on the heavy metal contaminated soil, which will activate the heavy metals in the soil and mineralize them. The reducing gas in the flue gas will reduce the heavy metal ions and adsorb the carbon particles. The organic gas will complex with the reduced heavy metals and carbon particles to form a stable mineral structure. After the metal ions are reduced, they are in a state that is difficult for crops to use, which avoids the absorption and enrichment of crops and ensures the food safety of crops. And this method is based on a heavy metal contaminated soil smoldering end closed cycle treatment equipment, specifically, after the larger agricultural and forestry solid waste is ignited in the smoldering chamber 11, the smaller agricultural and forestry solid waste and the heavy metal contaminated soil are mixed and smoldered in the passivation chamber 2, the gas and heat generated by the smoldering act on the heavy metal soil in the passivation chamber 2 and the flue gas purification chamber 3, and the ash generated by the smoldering is mixed with the heavy metal soil in the passivation chamber 2 and the flue gas purification chamber 3, so as to achieve the harmless treatment of the heavy metal contaminated soil. The method mainly starts the smoldering process by high-temperature ignition of agricultural and forestry solid waste and heavy metal contaminated soil with a mass ratio of 1 to 5:1, avoids the generation of open flames, and acts the temperature and gas components generated by the smoldering on the heavy metal contaminated soil, ensures the continuity of the smoldering through intermittent oxygen supply, and the gas generated by the smoldering is isolated and purified through the heavy metal contaminated soil, so as to achieve the end closed cycle treatment. In step S1, agricultural and forestry solid waste and a portion of heavy metal contaminated soil are preferably mixed in a ratio of 1 to 5:1 to ensure that the smoldering effect acts on the soil itself, and the existing agricultural and forestry solid waste will be carbonized at high temperature. If the ratio is too high, the soil treatment effect cannot be achieved, and if it is too low, carbonization cannot be achieved. In step S2, the water content of the heavy metal contaminated soil placed in the flue gas purification chamber 3 is preferably 30% to 45%. In fact, water can be appropriately added according to the moisture content of the original heavy metal contaminated soil to make its moisture content 30% to 45%. Only soil containing a certain amount of water, that is, a moisture content of 30% to 45%, can form soil colloidal properties and can adsorb particulate matter and NO in the flue gas. x 、SO 2Etc. The open flame ignition in step S3 mainly relies on the electrical connection between the resistance wire 4 and the power supply 9. The purpose of igniting agricultural and forestry solid waste with open flame is achieved by heating the resistance wire 4. The open flame can be extinguished by turning off the resistance wire 4. At the same time, the ignition time is limited, which is mainly used to distinguish between ignition and smoldering. If the ignition time is too long, it will turn into combustion, and increase the energy cost. In the heavy metal contaminated soil smoldering terminal closed-loop treatment technology in step S4, smoldering is a behavior between combustion and pyrolysis. Interval ventilation is to avoid extinguishing. The number of ventilation cannot be too many. Too much will cause combustion, and too little will cause extinguishing. Therefore, the actual preferred ventilation interval is 15-30min / time, 0.5-2min each time, and the air volume is 0.01-0.1m 3 / sThe smoldering mainly adopts intermittent oxygen supply to ensure the continuity of smoldering.

[0043] Preferably, the agricultural and forestry solid waste described in the above method is at least one of corn stalks, bean stalks, straw, potato stalks, tobacco stalks, dead grass and dead branches and leaves. It can be understood by those skilled in the art that in order to realize the large-scale resource processing of agricultural and forestry solid waste, reduce the pollution risk of agricultural and forestry solid waste to the ecological environment and reduce costs. This method uses local materials, so the actual preferred agricultural and forestry solid waste is at least one of corn stalks, bean stalks, straw, potato stalks, tobacco stalks, dead grass and dead branches and leaves. At the same time, a large amount of heat and flue gas will be generated during the smoldering of agricultural and forestry solid waste. Smoldering is not sufficient combustion. The flue gas will contain fine carbon particles, CO, VOCs, CH4, etc. The heat generated acts on the heavy metal contaminated soil, which will make the heavy metals in the soil active and mineralized, and the reducing gas in the flue gas will reduce the heavy metal ions, adsorb the carbon particles, and the organic gas will be complexed with the reduced heavy metals and carbon particles to form a stable mineral structure. After the metal ions are reduced, they are in a state that is difficult to use by crops, avoiding the absorption and enrichment of crops, and ensuring the food safety of crops.

[0044] Preferably, the heavy metal contaminated soil in the above method is one of As contaminated soil, Cr contaminated soil, Cd contaminated soil, Mn contaminated soil, Pb contaminated soil and Zn contaminated soil, and the heavy metal content is 0.1mg / Kg to 1.5mg / Kg. It can be understood by those skilled in the art that in order to ensure that the heavy metal contaminated soil reacts with the smoke generated by the smoldering of agricultural and forestry solid waste to form a stable mineral structure, the method preferably uses the heavy metal contaminated soil mainly as one of As contaminated soil, Cr contaminated soil, Cd contaminated soil, Mn contaminated soil, Pb contaminated soil and Zn contaminated soil, and the heavy metal content is 0.1mg / Kg to 1.5mg / Kg.

[0045] Preferably, in the above method, the moisture content of the agricultural and forestry solid waste after drying in step S1 is less than 10%, and the moisture content of the heavy metal contaminated soil is 5% to 10%. It can be understood by those skilled in the art that since too much moisture will cause smoldering and cannot burn, a large amount of water evaporation requires heat absorption. In order to ensure the treatment effect, the method preferably has a moisture content of less than 10% for the agricultural and forestry solid waste after drying, and a moisture content of 5% to 10% for the heavy metal contaminated soil after drying.

[0046] Example

[0047] 1. Smoldering end-of-line closed-loop treatment of heavy metal contaminated soil

[0048] 1. Manufacturing equipment: According to the attached drawings of the specification, the heavy metal contaminated soil smoldering terminal closed cycle treatment equipment is manufactured and

[0049] The corresponding parameters of the equipment are shown in Table 1.

[0050] Example 1 Example 2 Example 3 Grate type resistance wire spacing 1cm 2cm 3cm Perforated grille aperture <![CDATA[0.4cm 2 ]]> <![CDATA[0.7cm 2 ]]> <![CDATA[1cm 2 ]]> Equipment materials Nickel-based alloys Ceramic Materials Brown corundum

[0051] Table 1 Equipment processing parameters

[0052] 2. Pretreatment of heavy metal contaminated soil and solid waste. The heavy metal leaching concentrations of agricultural and forestry solid waste and heavy metal contaminated soil are: As: 3.5mg / Kg, Cr: 1.9mg / Kg, Cd: 2.9mg / Kg, Mn: 5.6mg / Kg, Pb: 7.1mg / Kg, Zn: 15.9mg / Kg, and they are dried separately to reduce the moisture content of agricultural and forestry solid waste to less than 10%, and the moisture content of heavy metal contaminated soil to 5% to 10%. The dried agricultural and forestry solid waste and heavy metal contaminated soil are crushed separately, and the particles with a size of less than 50 mesh are screened out and compounded according to 1 to 5:1; the specific process is shown in Table 2.

[0053] Example 1 Example 2 Example 3 Soil Type As and Cr contaminated soil Cd and Mn contaminated soil Pb and Zn contaminated soil Moisture content 5％ 10％ 8％ Particle size 50 mesh 100 mesh 150 mesh Agricultural and forestry solid waste Corn stalks straw Cigarette rod Moisture content 10％ 8％ 5％ Particle size 150 mesh 100 mesh 50 mesh Ratio 1：1 1：5 1：3

[0054] Table 2 Pretreatment process

[0055] 3. Ignition: Place agricultural and forestry solid waste larger than 50 mesh in the smoldering chamber 11 and wait for ignition; place the mixture of crushed agricultural and forestry solid waste and heavy metal contaminated soil in the passivation chamber 2 and wait for smoldering passivation; add water to the heavy metal contaminated soil to make its moisture content within the range of 30% to 45%, and place the moist heavy metal contaminated soil in the flue gas purification chamber 3; use an open flame at 300 to 500°C to ignite the agricultural and forestry solid waste in the smoldering chamber 11 for 1 to 5 minutes, and then extinguish the open flame; the specific process is shown in Table 3.

[0056] Ignition temperature Ignition time Flue gas purification soil moisture content Flue gas purification soil usage Example 1 300℃ 1min 30％ <![CDATA[5Kg / m 3 ]]> Example 2 500℃ 5min 45％ <![CDATA[20Kg / m 3 ]]> Example 3 400℃ 3min 40％ <![CDATA[10Kg / m 3 ]]>

[0057] Table 3 Mixed powder components / %

[0058] 4. Smoldering: Start the suction pump 5 to intermittently induce air through the air supply pipe 10, the ventilation interval is 15 to 30 minutes / time, 0.5 to 2 minutes each time, and the air volume is 0.01 to 0.1 m3 / s; the ash produced in the ash hopper 8 is fully mixed to achieve the passivation treatment of the heavy metal contaminated soil; the specific process is shown in Table 4.

[0059] Example 1 Example 2 Example 3 Air intake interval 15min / time 30min / time 20min / time time 0.5min 2min 1min Air volume <![CDATA[0.01m 3 / s]]> <![CDATA[0.1m 3 / s]]> <![CDATA[0.05m 3 / s]]>

[0060] Table 4 Smoldering process

[0061] 2. Performance test of treated soil

[0062] The performance test results of the soil contaminated by As and Cr after treatment are shown in the attached figure. Figure 2 As shown in the figure, the heavy metal solidification and stabilization efficiency in heavy metal contaminated soil is greater than 95%, the carbon content of the treated soil is 30%, the water retention rate is 80%, and the soil density is 3.6g / cm 3 , N content was 0.9%, P content was 2.3%, K content was 5.6%, and the germination rate of Chinese cabbage seeds reached 99%, indicating that this method has a significant effect on the treatment of As and Cr.

[0063] Example 2 The performance test results of Cd and Mn contaminated soil after treatment are shown in the attached figure. Figure 3 As shown in the figure, the solidification and stabilization efficiency of heavy metals in heavy metal contaminated soil is greater than 96%, the carbon content of the treated soil is 41%, the water retention rate is 89%, and the soil density is 2.1g / cm 3 , N content was 0.3%, P content was 1.4%, K content was 4.1%, and the germination rate of Chinese cabbage seeds was 85%, indicating that this method has a significant solidification and stabilization effect on Cd and Mn contaminated soil, and at the same time improves the activity of the soil.

[0064] Example 3 Performance test results of Pb and Zn contaminated soil after treatment are shown in the attached Figure 4 As shown in the figure, the heavy metal solidification and stabilization efficiency in heavy metal contaminated soil is greater than 89%, the carbon content of the treated soil is 39%, the water retention rate is 85%, and the soil density is 3.0g / cm 3 , N content was 0.6%, P content was 1.9%, K content was 5.0%, and the germination rate of Chinese cabbage seeds was 95%, which showed that this method had a significant solidification and stabilization effect on Pb and Zn soils, and could also improve various soil indicators and improve soil structure.

Claims

1. A heavy metal contaminated soil smoldering end closed cycle treatment equipment, characterized by: The invention comprises a smoldering chamber (11), a passivation chamber (2), a flue gas purification chamber (3) and an ash hopper (8); the passivation chamber (2) is connected to the upper end of the smoldering chamber (11), and a grille (13) is arranged at the connection point; the flue gas purification chamber (3) is sleeved outside the smoldering chamber (11) and the passivation chamber (2), and the ash hopper (8) is connected to the lower end of the flue gas purification chamber (3), and a plurality of grate bars (6) are arranged at intervals at the connection point; and a plurality of resistance wires (4) are arranged at intervals at the lower end of the smoldering chamber (11).

2. The heavy metal contaminated soil smoldering terminal closed cycle treatment equipment according to claim 1 is characterized by: An air supply pipe (10) is arranged at intervals on the side wall of the flue gas purification chamber (3), and an air suction pump (5) is arranged at the end of the air supply pipe (10) away from the flue gas purification chamber (3).

3. The heavy metal contaminated soil smoldering terminal closed cycle treatment equipment according to claim 1 is characterized by: The resistance wires (4) at the lower end of the smoldering chamber (11) are distributed in parallel, and the spacing between adjacent resistance wires (4) is 1 to 3 cm.

4. The heavy metal contaminated soil smoldering terminal closed cycle treatment equipment according to claim 1 is characterized by: The holes of the grid (13) at the connection point between the smoldering chamber (11) and the passivation chamber (2) are evenly distributed, and the hole diameter is 0.4 to 1 cm. 2 .

5. The heavy metal contaminated soil smoldering terminal closed cycle treatment equipment according to claim 1 is characterized in that: A soil inlet pipe A (1) is arranged at the top of the passivation chamber (2), a soil inlet pipe B (14) is arranged at the top of the flue gas purification chamber (3), a feed pipe (12) is arranged at the top of the smoldering chamber (11), and the feed pipe (12) passes through the flue gas purification chamber (3) at the end away from the smoldering chamber (11).

6. The heavy metal contaminated soil smoldering terminal closed cycle treatment equipment according to claim 5 is characterized by: A one-way plate (15) is arranged in at least one of the soil inlet pipe A (1), the soil inlet pipe B (14) and the feed pipe (12).

7. A method for treating heavy metal contaminated soil smoldering end closed cycle, characterized in that: The processing device comprising any one of claims 1 to 6, wherein the steps are as follows: S1, drying and crushing agricultural and forestry solid waste and a portion of heavy metal contaminated soil respectively, and selecting particles with a size less than 50 mesh and mixing them in a ratio of 1 to 5:1; placing the mixture in a passivation chamber (2); and placing agricultural and forestry solid waste with a size greater than 50 mesh in a smoldering chamber (11); S2, adding water to another portion of the heavy metal contaminated soil to make its moisture content 30% to 45%, and placing the moist heavy metal contaminated soil in a flue gas purification chamber (3); S3, using an open flame to ignite the agricultural and forestry solid waste in the smoldering chamber (11), the ignition time is 1 to 5 minutes, and then extinguishing the open flame; S4. Intermittent ventilation is introduced into the flue gas purification chamber (3). The ventilation interval is 15 to 30 minutes per time, 0.5 to 2 minutes per time, and the air volume is 0.01 to 0.1 m 3 / s; S5. Fully mix the ash produced in the ash hopper (8).

8. The method for treating heavy metal contaminated soil smoldering in a closed cycle according to claim 7, characterized in that: The agricultural and forestry solid waste is at least one of corn stalks, bean stalks, rice straw, potato stalks, tobacco stalks, dead grass and dead branches and leaves.

9. The method for treating heavy metal contaminated soil smoldering in a closed cycle according to claim 7, characterized in that: The heavy metal contaminated soil is one of As contaminated soil, Cr contaminated soil, Cd contaminated soil, Mn contaminated soil, Pb contaminated soil and Zn contaminated soil, and the heavy metal content is 0.1 mg / Kg to 1.5 mg / Kg.

10. The method for treating heavy metal contaminated soil smoldering in a closed cycle according to claim 7, characterized in that: The moisture content of the agricultural and forestry solid waste after drying in step S1 is less than 10%, and the moisture content of the heavy metal contaminated soil is 5% to 10%.

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