Thermal desorption treatment device and method for high-concentration mercury polluted soil

Abstract

The invention relates to a high-concentration mercury polluted soil thermal desorption treatment device which comprises a feeding device, the feeding device comprises a feeding hopper, the bottom of the feeding hopper is connected with the input end of a conveying belt, the output end of the conveying belt is provided with a spiral conveyor, and the output end of the spiral conveyor is provided with an indirect thermal desorption device; the indirect thermal desorption device comprises a material cavity, a combustion cavity is arranged below the material cavity, and a combustor is arranged below the combustion cavity; the tail part of the material cavity is provided with a gas phase treatment device, the gas phase treatment device comprises a high-temperature ceramic dust remover, the upper end of the high-temperature ceramic dust remover is communicated with the upper end of a first-stage condenser through a pipeline, the first-stage condenser is communicated with the upper end of a second-stage condenser through a pipeline, and the second-stage condenser is communicated with the tail part of the material cavity through a pipeline. The second-stage condenser is connected with the upper end of the freezer through a pipeline, the freezer is connected with the demister through a pipeline, and the demister is communicated with the upper ends of the first-stage adsorption tank and the second-stage adsorption tank through pipelines.

Description

Technical Field

[0001] The present invention relates to the technical field of soil treatment, and in particular to a device and method for thermal desorption treatment of soil contaminated with high concentration mercury. Background Art

[0002] Mercury is a silvery-white liquid metal that evaporates at room temperature. At 0°C, the saturated concentration of mercury is 2.174 mg / m3, which is more than 200 times the national standard (0.01 mg / m3).

[0003] Due to its special physical and chemical properties, mercury is widely used in chemical and petrochemical industries, pharmaceuticals, pulp and paper, electrical and electronic instruments, etc. With the development of industrialization and urbanization, the original industrial production plants may be relocated, and the original sites may be contaminated with mercury, which poses a potential hazard to the environment and human health.

[0004] Commonly used remediation technologies for mercury-contaminated soil include solidification / stabilization, leaching technology, and thermal desorption technology. In particular, thermal desorption technology can evaporate mercury and its chemicals from the soil and turn them into gas phase, thoroughly cleaning the soil. It is the preferred remediation technology for mercury-contaminated soil. However, due to the high energy consumption of thermal desorption technology, the cost of remediation is high, which limits its widespread use. After mercury and its compounds evaporate to form a gas phase, wet spraying + condensation + activated carbon adsorption technology is used for gas phase disposal. After the gas phase meets the standards, it is discharged into the atmosphere. During the gas phase disposal process, mercury and its compounds in the soil are transferred to the liquid phase. Since mercury is easy to evaporate and the emission limits of mercury in the atmosphere and wastewater are very high, subsequent disposal is complicated and costly. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and provide a device and method for thermal desorption treatment of soil contaminated with high concentration of mercury.

[0006] To achieve the above-mentioned purpose, the technical solution of the present invention is to design a thermal desorption treatment device for soil contaminated with high concentration mercury, characterized in that it comprises a feeding device, the feeding device comprises a feeding hopper, the bottom of the feeding hopper is connected to the input end of the conveyor belt, the output end of the conveyor belt is provided with a screw conveyor, and the output end of the screw conveyor is provided with an indirect thermal desorption device; The indirect thermal desorption device comprises a material cavity, a combustion cavity is provided below the material cavity, and a burner is provided below the combustion cavity; A gas phase treatment device is provided at the tail of the material cavity, and the gas phase treatment device includes a high-temperature ceramic dust collector, the upper end of the high-temperature ceramic dust collector is connected to the upper end of the first-level condenser through a pipeline, the first-level condenser is connected to the upper end of the second-level condenser through a pipeline, the second-level condenser is connected to the upper end of the freezer through a pipeline, the freezer is connected to the demister through a pipeline, the demister is connected to the upper end of the first-level adsorption tank through a pipeline, and the first-level adsorption tank is connected to the upper end of the second-level adsorption tank through a pipeline.

[0007] A further preferred technical solution is that the gas phase disposal device is connected to the wastewater treatment device through a pipeline, the wastewater treatment device includes an evaporator, the evaporator is connected to the secondary freezer through a pipeline, and the secondary condenser is connected to the primary freezer and the secondary freezer in sequence through a pipeline.

[0008] A further preferred technical solution is that the lower ends of the primary condenser, the secondary condenser, the freezer and the demister are all provided with pipelines connected to the access pipeline of the evaporator in the wastewater treatment device.

[0009] A further preferred technical solution also includes a high-temperature flue gas treatment unit, wherein the high-temperature flue gas treatment unit includes a heat exchanger, wherein the heat exchanger is connected to the combustion chamber through a pipeline, and the heat exchanger is connected to the chimney through a pipeline.

[0010] A further preferred technical solution also includes a discharging device, wherein the discharging device includes a screw conveyor, and the screw conveyor is provided with a humidifier.

[0011] A further preferred technical solution is that the primary condenser and the secondary condenser are shell-and-tube indirect heat exchangers, and are connected to an external air cooling tower through pipelines, with water being the cooling medium.

[0012] A thermal desorption treatment method for soil contaminated with high concentration of mercury. Mercury-contaminated soil is heated to produce a high-temperature gas phase containing mercury above 450°C. The high-temperature gas phase is treated with a dust collector to remove solid particles in the gas phase and clean the gas phase. It is then condensed to form a gas phase temperature of 20-30°C, and then frozen to form mercury liquid below 4°C. The mercury liquid is concentrated by an evaporator and then recovered.

[0013] A further preferred technical solution is that before heating, the mercury-contaminated soil is screened into particles of equal size through a vibrating screen, and then quantitatively transported through a quantitative metering belt, and the iron in the soil is removed by an iron remover before being transported to an indirect thermal desorption device for heating to produce a high-temperature gas phase.

[0014] A further preferred technical solution is that the high-temperature gas phase passes through a primary condenser and a secondary condenser to form a gas phase temperature of 20-30°C.

[0015] A further preferred technical solution is that the high-temperature gas phase is discharged after being frozen and adsorbed by activated carbon, and the adsorption value is ≥80kg / m3.

[0016] The advantages and beneficial effects of the present invention are as follows: (1) For soil contaminated with high concentrations of mercury, the device utilizes the physical and chemical properties of mercury to heat the contaminated soil, volatilize the mercury and its compounds, clean the soil, and then process the gaseous mercury and its compounds to achieve concentration and recycling, while ensuring that the gases and liquids generated in the process meet the emission standards.

[0017] (2) Compared with the conventional indirect thermal desorption gas phase treatment method, the dry high-temperature ceramic dust removal of this device can not only remove solid particles in the gas phase and clean the gas phase, but also meet the requirements of condensation and concentration of the gas phase in the subsequent process, reduce the use of a large amount of spray water, reduce the generation of wastewater (reduced to 5-10%) and the treatment of mercury wastewater.

[0018] (3) This device uses condensation freezing + adsorption to treat the gas phase, which can recover high-concentration mercury, reduce the cost of indirect thermal desorption treatment of mercury-contaminated soil, and also recover heavy metal mercury to generate income. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the present invention; In the figure: 10. Feeding device; 11. Feeding hopper; 12. Vibrating screen; 13. Quantitative metering belt; 14. Conveying belt; 15. Iron remover; 16. Screw conveyor; 20. Indirect thermal desorption device; 21. Material cavity; 22. Combustion cavity; 23. Burner; 30. Discharging device; 31. Screw conveying device; 32. Humidifier; 40. High-temperature flue gas treatment device; 41. Heat exchanger; 42. Chimney; 50. Gas phase treatment device; 51. High-temperature ceramic dust collector; 52. Primary condenser; 53. Secondary condenser; 54. Freezer; 55. Demister; 56. Primary adsorption tank; 57. Secondary adsorption tank; 60. Wastewater treatment device; 61. Evaporator; 62. Third-stage condenser; 63. First-stage freezer; 64. Secondary freezer. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0021] Reference Figure 1As shown, a thermal desorption treatment device for high-concentration mercury contaminated soil includes a feeding device 10, wherein the feeding device 10 includes a feeding hopper 11, a vibrating screen 12 is provided at the bottom of the feeding hopper 11, a quantitative metering belt 13 is provided below the vibrating screen 12, an output end of the quantitative metering belt 13 is connected to an input end of a conveying belt 14, an output end of the conveying belt 14 is connected to one end of an iron remover 15, a screw conveyor 16 is provided at the other end of the iron remover 15, an indirect thermal desorption device 20 is provided at the output end of the screw conveyor 16, and the feeding device 10 screens high-concentration mercury contaminated soil of different sizes through the vibrating screen 12, screens the high-concentration mercury contaminated soil into particles of the same size, and then quantitatively transports it through the quantitative metering belt 13, which helps the indirect thermal desorption device 20 to fully heat the contaminated soil.

[0022] The indirect thermal desorption device 20 includes a material cavity 21, a combustion cavity 22 is provided below the material cavity 21, and a burner 23 is provided below the combustion cavity 22. The burner 23 generates high-temperature flue gas in the combustion cavity 22 to heat the material cavity 21, thereby heating the contaminated soil to a certain temperature, so that mercury and its compounds are volatilized to form high-temperature gas phase substances.

[0023] The high-temperature gaseous material enters the gas phase treatment device 50 from the tail of the material cavity 21. The gas phase treatment device 50 includes a high-temperature ceramic dust collector 51. The high-temperature ceramic dust collector 51 is connected to the upper end of the tail of the material cavity 21 through a pipeline. The high-temperature gaseous material is filtered by the high-temperature ceramic dust collector 51 to remove particulate impurities. Moreover, since the temperature of the generated high-temperature gaseous material is above 450°C, after dust removal by the high-temperature ceramic dust collector 51, it can also meet the subsequent condensation and freezing requirements of the gas phase.

[0024] The high-temperature ceramic dust collector 51 has a discharge port at the lower end, and the waste generated after dust removal by the high-temperature ceramic dust collector 51 is transported through the discharge port. The upper end of the high-temperature ceramic dust collector 51 is connected to the upper end of the first-stage condenser 52 through a pipeline, and the first-stage condenser 52 is connected to the upper end of the second-stage condenser 53 through a pipeline. The first-stage condenser 52 and the second-stage condenser 53 are shell-and-tube indirect heat exchangers, and are connected to an external air-cooling tower through a pipeline. Water is used as a cooling medium. The first-stage condenser 52 and the second-stage condenser 53 are connected to the air-cooling tower through a pipeline. The high-temperature gas phase material above 450°C reaches a temperature of 60-80°C after passing through the first-stage condenser 52; and the gas phase temperature reaches 20-30°C after passing through the second-stage condenser 53.

[0025] The high-temperature gas phase material passes through the primary condenser 52 and the secondary condenser 53 to generate mercury-containing wastewater, which is discharged from the lower ends of the primary condenser 52 and the secondary condenser 53 .

[0026] The secondary condenser 53 is connected to the upper end of the freezer 54 through a pipeline. The freezer 54 is for indirect heat exchange. The refrigerant is a mixture of water and organic matter. The organic matter can be ethylene glycol. Water and ethylene glycol are mixed in a certain proportion to form a refrigerant. The high-temperature gas phase substance passes through the above-mentioned freezer 54, and the temperature is reduced to below 4°C. The high-temperature gas phase substance passes through the freezer 54 to form mercury-containing wastewater, which is discharged from the lower end of the freezer 54.

[0027] The freezer 54 is connected to the demister 55 through a pipeline, and the demister 55 removes moisture from the high-temperature gas phase material. The high-temperature gas phase material passes through the demister 55 to generate mercury-containing wastewater, which is discharged from the lower end of the demister 55.

[0028] The demister 55 is connected to the upper end of the primary adsorption tank 56 through a pipeline, and the primary adsorption tank 56 is connected to the upper end of the secondary adsorption tank 57 through a pipeline. The primary adsorption tank 56 and the secondary adsorption tank 57 are filled with activated carbon modified to adsorb mercury, which has a strong mercury adsorption capacity and an adsorption value of ≥80kg / m3. The activated carbon after mercury adsorption is handed over to the mercury recovery and refining unit for further disposal and recycling.

[0029] The gas phase treatment device 50 is connected to the wastewater treatment device 60 through a pipeline. The wastewater treatment device 60 includes an evaporator 61. The mercury-containing wastewater generated by the gas phase treatment device 50 is evaporated by the evaporator 61 to further concentrate the mercury-containing wastewater. The evaporator 61 is connected to the three-stage condenser 62 through a pipeline, and the high-temperature mercury-containing waste gas is subjected to the three-stage condenser 62. After being treated by the three-stage condenser 62, the high-temperature mercury-containing waste gas is condensed to form concentrated mercury-containing wastewater. The three-stage condenser 62 is connected to the first-stage freezer 63 and the second-stage freezer 64 in sequence through a pipeline to concentrate the mercury-containing waste liquid, which is recycled by a mercury recycling unit. An outlet is provided at the lower end of the evaporator 61. The sludge generated after the mercury-containing wastewater is evaporated is entrusted to a qualified unit for disposal.

[0030] The gas phase disposal device 50 is connected to the wastewater treatment device 60 through a pipeline. Specifically, the lower ends of the primary condenser 52, the secondary condenser 53, the freezer 54, and the demister 55 are all provided with pipelines connected to the evaporator 61 in the wastewater treatment device 60, and the mercury-containing wastewater enters the evaporator 61 through the pipeline for wastewater treatment.

[0031] It also includes a high-temperature flue gas treatment device 40, which includes a heat exchanger 41. The heat exchanger 41 is connected to the combustion chamber 22 through a pipeline. The high-temperature flue gas generated by the combustion chamber 22 enters the high-temperature flue gas treatment device 40 and passes through the heat exchanger 41 to reduce heat energy loss and lower the flue gas temperature. The heat exchanger 41 is connected to the chimney 42 through a pipeline, and the cooled flue gas is discharged into the atmosphere through the chimney 42.

[0032] It also includes a discharging device 30, which includes a spiral conveying device 31. The spiral conveying device 31 is provided with a humidifier 32. Soil enters the discharging unit from the material cavity, and is sprayed in the spiral conveying device 31 by the humidifier 32 to reduce the temperature of the soil to 60°C. The soil is then output by the spiral conveying device 31 and transported to a designated location by a transport vehicle.

[0033] Working principle: After pretreatment, the high-concentration mercury-contaminated soil enters the feeding device 10 through the feeder, and enters the material cavity 21 of the indirect thermal desorption device 20 through the screw conveyor 16. The burner 23 generates high-temperature flue gas in the combustion cavity 22 to heat the material cavity 21, thereby heating the contaminated soil in the material cavity 21 to a certain temperature, so that mercury and its compounds are volatilized to form high-temperature gas phase substances.

[0034] The high-temperature gaseous material passes through the induced draft fan and enters the gas phase treatment device 50. After dust removal, primary condensation, secondary condensation and freezing in the high-temperature ceramic device 51, it passes through the demister 55 to remove moisture, and then passes through the first adsorption tank 56 and the second adsorption tank 57 for two-stage modified activated carbon adsorption, and is discharged into the atmosphere after meeting the standards.

[0035] The high-temperature flue gas generated by the combustion chamber 22 enters the high-temperature flue gas treatment device 40, passes through the heat exchanger 41 to reduce heat energy loss, lowers the flue gas temperature, and is then discharged into the atmosphere through the chimney 42.

[0036] The soil enters the discharging device 30 from the material cavity 21, and is sprayed in the spiral conveying device 31 by the humidifier 32 to reduce the temperature of the soil to 60°C. The soil is then output from the spiral conveying device 31 and transported to a designated location by a transport vehicle.

[0037] In the gas phase treatment device 50 , mercury-containing wastewater is produced during the gas phase treatment process of primary condensation, secondary condensation, freezing and demister 55 , and the wastewater enters the wastewater treatment device 60 .

[0038] In the wastewater treatment device 60, after evaporation in the evaporator 61, condensation in the condenser, and freezing in the freezer, the mercury-containing waste liquid is concentrated and transferred to the mercury recovery and reuse unit for recycling.

[0039] In the gas phase treatment device 50, the high temperature gas phase generated is above 450°C, and after dust removal by the dry high temperature ceramic dust collector 51, it meets the subsequent condensation and freezing requirements of the gas phase; In the gas phase treatment device 50, the primary condenser 52 and the secondary condenser 53 are shell-and-tube indirect heat exchangers, an air cooling tower is provided, and water is used as the refrigerant; The gas phase above 450°C reaches a temperature of 60-80°C after passing through the first condenser 52; and reaches a temperature of 20-30°C after passing through the second condenser 53; In the gas phase treatment device 50, the refrigeration unit is an indirect heat exchanger; the refrigerant is a mixture of water and organic matter; The above-mentioned refrigerant, the organic substance is ethylene glycol; The above refrigerant, water and ethylene glycol are mixed in a certain proportion to form a refrigerant The gas phase passes through the above-mentioned refrigerator 54 and its temperature is reduced to below 4°C.

[0040] In the gas phase treatment device 50, the modified activated carbon adsorption tank is filled with activated carbon modified to adsorb mercury, which has a strong mercury adsorption capacity and an adsorption value of ≥80kg / m3.

[0041] The activated carbon after adsorbing mercury is handed over to the mercury recovery and refining unit for further treatment and recycling.

[0042] A thermal desorption treatment method for high-concentration mercury contaminated soil: Mercury-contaminated soil is heated to produce a high-temperature gas phase containing mercury above 450°C. The high-temperature gas phase is treated with a dust collector to remove solid particles in the gas phase and clean the gas phase. It is then condensed to form a gas phase temperature of 20-30°C, and then frozen to form mercury liquid below 4°C. The mercury liquid is concentrated by an evaporator and then recovered.

[0043] Furthermore, before heating, the mercury-contaminated soil is screened into particles of equal size by a vibrating screen 12 and then quantitatively transported to an indirect thermal desorption device by a quantitative metering belt 13 for heating to generate a high-temperature gas phase.

[0044] Furthermore, the high-temperature gas phase passes through the primary condenser 52 and the secondary condenser 53 to form a gas phase temperature of 20-30°C.

[0045] Furthermore, the high-temperature gas phase is discharged after being frozen and adsorbed by activated carbon, and the adsorption value is ≥80kg / m3.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A thermal desorption treatment device for high-concentration mercury contaminated soil, characterized in that: The feeding device comprises a feeding hopper, the bottom of the feeding hopper is connected to the input end of the conveying belt, the output end of the conveying belt is provided with a screw conveyor, and the output end of the screw conveyor is provided with an indirect thermal desorption device; The indirect thermal desorption device comprises a material cavity, a combustion cavity is provided below the material cavity, and a burner is provided below the combustion cavity; A gas phase treatment device is provided at the tail of the material cavity, and the gas phase treatment device includes a high-temperature ceramic dust collector, the upper end of the high-temperature ceramic dust collector is connected to the upper end of the first-level condenser through a pipeline, the first-level condenser is connected to the upper end of the second-level condenser through a pipeline, the second-level condenser is connected to the upper end of the freezer through a pipeline, the freezer is connected to the demister through a pipeline, the demister is connected to the upper end of the first-level adsorption tank through a pipeline, and the first-level adsorption tank is connected to the upper end of the second-level adsorption tank through a pipeline.

2. The thermal desorption treatment device for high-concentration mercury contaminated soil according to claim 1 is characterized in that: The gas phase disposal device is connected to the wastewater treatment device through a pipeline. The wastewater treatment device includes an evaporator. The evaporator is connected to the secondary freezer through a pipeline. The secondary condenser is connected to the primary freezer and the secondary freezer in sequence through pipelines.

3. The thermal desorption treatment device for high-concentration mercury contaminated soil according to claim 1 is characterized in that: The lower ends of the primary condenser, the secondary condenser, the freezer and the demister are all provided with pipelines connected to the access pipeline of the evaporator in the wastewater treatment device.

4. A thermal desorption treatment device for high-concentration mercury contaminated soil according to any one of claims 1 to 3, characterized in that: It also includes a high-temperature flue gas treatment unit, which includes a heat exchanger. The heat exchanger is connected to the combustion chamber through a pipeline, and the heat exchanger is connected to the chimney through a pipeline.

5. A thermal desorption treatment device for high-concentration mercury contaminated soil according to any one of claims 1 to 3, characterized in that: It also includes a discharging device, which includes a screw conveyor, and the screw conveyor is provided with a humidifier.

6. A thermal desorption treatment device for high-concentration mercury contaminated soil according to any one of claims 1 to 3, characterized in that: The primary condenser and the secondary condenser are shell-and-tube indirect heat exchangers, and are connected to an external air cooling tower through pipelines, with water as the cooling medium.

7. A method for thermal desorption of soil contaminated with high concentrations of mercury, characterized in that: Mercury-contaminated soil is heated to produce a high-temperature gas phase containing mercury above 450°C. The high-temperature gas phase is treated with a dust collector to remove solid particles in the gas phase and clean the gas phase. It is then condensed to form a gas phase temperature of 20-30°C, and then frozen to form mercury liquid below 4°C. The mercury liquid is concentrated by an evaporator and then recovered.

8. The method for thermal desorption of soil contaminated with high concentration mercury according to claim 7, characterized in that: Before heating, the mercury-contaminated soil is screened into particles of equal size through a vibrating screen, and then quantitatively transported through a quantitative metering belt. After the iron in the soil is removed by an iron remover, it is transported to an indirect thermal desorption device for heating to produce a high-temperature gas phase.

9. The method for thermal desorption of soil contaminated with high concentration mercury according to claim 7, characterized in that: The high temperature gas phase passes through the primary condenser and the secondary condenser to form a gas phase temperature of 20-30°C.

10. The method for thermal desorption of soil contaminated with high concentration mercury according to claim 7, characterized in that: The high-temperature gas phase is discharged after being frozen and adsorbed by activated carbon, and the adsorption value is ≥80kg / m3.

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