Thermal desorption treatment device for high-concentration mercury polluted soil

Abstract

The utility model relates to a thermal desorption treatment device for high-concentration mercury polluted soil, 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 conveyer, and the output end of the spiral conveyer 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] This utility model relates to the field of soil treatment technology, and in particular to a thermal desorption treatment device for high-concentration mercury-contaminated soil. Background Technology

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

[0003] Mercury possesses unique physical and chemical properties, making it widely used in chemical and petrochemical industries, pharmaceuticals, pulp and paper manufacturing, and electrical and electronic instrumentation. However, with industrialization and urbanization, the relocation of former industrial plants may leave behind sites with mercury contamination, posing potential hazards to the environment and human health.

[0004] For mercury-contaminated soil, commonly used remediation technologies include solidification / stabilization, leaching, and thermal desorption. Thermal desorption, in particular, evaporates mercury and its chemicals from the soil into a gaseous phase, thoroughly cleaning the soil and making it the preferred remediation technology for mercury-contaminated soil. However, its high energy consumption leads to high remediation costs, limiting its widespread use. Furthermore, after mercury and its compounds volatilize into a gaseous phase, a wet scrubbing + condensation + activated carbon adsorption technique is used for gaseous phase treatment. Once the gaseous phase meets standards, it is released into the atmosphere. During this gaseous phase treatment process, mercury and its compounds in the soil transfer to the liquid phase. Because mercury is easily evaporated, and atmospheric and wastewater emission restrictions on mercury are very strict, subsequent treatment becomes complex and costly. Utility Model Content

[0005] The purpose of this invention is to overcome the defects in the existing technology and provide a thermal desorption treatment device for high-concentration mercury-contaminated soil.

[0006] To achieve the above objectives, the technical solution of this utility model is to design a thermal desorption treatment device for high-concentration mercury-contaminated soil, characterized in that it includes a feeding device, the feeding device including a feeding hopper, the bottom of the feeding hopper being connected to the input end of a conveyor belt, the output end of the conveyor belt being provided with a screw conveyor, and the output end of the screw conveyor being provided with an indirect thermal desorption device.

[0007] The indirect thermal desorption device includes a material chamber, a combustion chamber below the material chamber, and a burner below the combustion chamber;

[0008] The tail end of the material chamber is equipped with a gas phase treatment device, which 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 primary condenser through a pipe. The primary condenser is connected to the upper end of the secondary condenser through a pipe. The secondary condenser is connected to the upper end of the freezer through a pipe. The freezer is connected to the demister through a pipe. The demister is connected to the upper end of the primary adsorption tank through a pipe. The primary adsorption tank is connected to the upper end of the secondary adsorption tank through a pipe.

[0009] A further preferred technical solution is that the gas phase treatment device is connected to the wastewater treatment device via a pipeline, the wastewater treatment device includes an evaporator, the evaporator is connected to a three-stage condenser via a pipeline, and the three-stage condenser is connected to a first-stage freezer and a second-stage freezer in sequence via pipelines.

[0010] A further preferred technical solution is that the lower ends of the primary condenser, secondary condenser, freezer, and demister are all provided with pipes that connect to the evaporator in the wastewater treatment device.

[0011] A further preferred technical solution includes a high-temperature flue gas treatment unit, which includes a heat exchanger connected to the combustion chamber via a pipe and connected to the chimney via a pipe.

[0012] A further preferred technical solution includes a discharge device, which includes a screw conveyor and a humidifier.

[0013] 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-cooled tower via pipelines, with water as the cooling medium.

[0014] A method for thermal desorption treatment of soil contaminated with high concentrations of mercury.

[0015] Mercury-contaminated soil is heated to produce a high-temperature gas phase containing mercury at a temperature above 450°C. This high-temperature gas phase is then treated by a dust collector to remove solid particles and clean the gas phase. After condensation, the gas phase temperature is reduced to 20-30°C. After freezing, the mercury liquid is formed at a temperature below 4°C. The mercury liquid is then concentrated in an evaporator and recovered.

[0016] A further preferred technical solution is that, before heating, the mercury-contaminated soil is screened into particles of equal size using a vibrating screen, then quantitatively transported by a metering belt, and after iron is removed from the soil by an iron remover, it is transported to an indirect thermal desorption device for heating to generate a high-temperature gas phase.

[0017] 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.

[0018] A further preferred technical solution is that the high-temperature gas phase, after being frozen, is then emitted after being adsorbed by activated carbon, with an adsorption value ≥80kg / m3.

[0019] The advantages and beneficial effects of this utility model are as follows: (1) For soil contaminated with high concentration of mercury, this device uses the physical and chemical properties of mercury to heat the contaminated soil, so that the mercury and its compounds volatilize, thus cleaning the soil. Then, the gaseous mercury and its compounds are treated to achieve concentration, recycling and utilization, while ensuring that the gas and liquid generated in the process meet the emission standards.

[0020] (2) In contrast to conventional indirect thermal desorption gas phase treatment methods, this device uses dry high-temperature ceramic dust removal, which can remove solid particles from the gas phase, clean the gas phase, meet the requirements of subsequent processes for condensing and concentrating the gas phase, reduce the use of a large amount of spray water, reduce the amount of wastewater generated (reduced to 5-10%), and treat mercury wastewater.

[0021] (3) This device uses condensation and freezing + adsorption to treat the gas phase, which can recover high concentrations of mercury, reduce the cost of indirect thermal desorption treatment of mercury-contaminated soil, and also recover heavy metal mercury, generating revenue. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the present invention;

[0023] In the diagram: 10. Feeding device; 11. Feed hopper; 12. Vibrating screen; 13. Metering belt; 14. Conveyor belt; 15. Magnetic separator; 16. Screw conveyor; 20. Indirect thermal desorption device; 21. Material chamber; 22. Combustion chamber; 23. Burner; 30. Discharge device; 31. Screw conveyor; 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. Refrigerator; 55. Demister; 56. Primary adsorption tank; 57. Secondary adsorption tank; 60. Wastewater treatment device; 61. Evaporator; 62. Tertiary condenser; 63. Primary refrigerator; 64. Secondary refrigerator. Detailed Implementation

[0024] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of this utility model and should not be construed as limiting the scope of protection of this utility model.

[0025] Reference Figure 1 As shown, a thermal desorption treatment device for high-concentration mercury-contaminated soil includes a feeding device 10, which includes a feeding hopper 11. A vibrating screen 12 is located at the bottom of the feeding hopper 11, and a metering belt 13 is located below the vibrating screen 12. The output end of the metering belt 13 is connected to the input end of a conveyor belt 14, and the output end of the conveyor belt 14 is connected to one end of a magnetic separator 15. A screw conveyor 16 is located at the other end of the magnetic separator 15, and an indirect thermal desorption device 20 is located at the output end of the screw conveyor 16. The feeding device 10 screens high-concentration mercury-contaminated soil of different sizes through the vibrating screen 12, separating the soil into particles of uniform size. The soil is then metered and conveyed through the metering belt 13, which helps the indirect thermal desorption device 20 to fully heat the contaminated soil.

[0026] The indirect thermal desorption device 20 includes a material chamber 21, a combustion chamber 22 is provided below the material chamber 21, and a burner 23 is provided below the combustion chamber 22. High-temperature flue gas is generated in the combustion chamber 22 through the burner 23, which heats the material chamber 21, thereby heating the polluted soil to a certain temperature, causing mercury and its compounds to volatilize and form high-temperature gaseous substances.

[0027] The high-temperature gaseous material enters the gas phase treatment device 50 from the tail end of the material chamber 21. The gas phase treatment device 50 includes a high-temperature ceramic dust collector 51, which is connected to the upper end of the tail end of the material chamber 21 through a pipe. 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 being dusted by the high-temperature ceramic dust collector 51, it can also meet the requirements for subsequent condensation and freezing of the gas phase.

[0028] The high-temperature ceramic dust collector 51 has a discharge port at its lower end, through which the waste generated after dust removal by the high-temperature ceramic dust collector 51 is transferred. 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 pipe. The first-stage condenser 52 is connected to the upper end of the second-stage condenser 53 through a pipe. 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-cooled tower through pipes. Water is used as the cooling medium. The high-temperature gaseous substances above 450°C reach a temperature of 60-80°C after passing through the first-stage condenser 52; and after passing through the second-stage condenser 53, the gaseous temperature reaches 20-30°C.

[0029] The high-temperature gaseous substance passes through the primary condenser 52 and the secondary condenser 53 to form mercury-containing wastewater, which is discharged from the lower end of the primary condenser 52 and the secondary condenser 53.

[0030] The secondary condenser 53 is connected to the upper end of the freezer 54 via a pipe. The freezer 54 is an indirect heat exchanger. 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 gaseous substance passes through the freezer 54 and its temperature drops to below 4°C. The high-temperature gaseous substance passes through the freezer 54 and generates mercury-containing wastewater, which is discharged from the lower end of the freezer 54.

[0031] The freezer 54 is connected to the demister 55 through a pipe. The demister 55 removes moisture from the high-temperature gaseous substance. The high-temperature gaseous substance forms mercury-containing wastewater through the demister 55 and is discharged from the lower end of the demister 55.

[0032] The demister 55 is connected to the upper end of the primary adsorption tank 56 via a pipe. The primary adsorption tank 56 is connected to the upper end of the secondary adsorption tank 57 via a pipe. The primary adsorption tank 56 and the secondary adsorption tank 57 are filled with modified activated carbon for adsorbing mercury. The activated carbon has a strong mercury adsorption capacity with an adsorption value ≥80kg / m3. The activated carbon after adsorbing mercury is handed over to a mercury recovery and refining unit for further processing and recycling.

[0033] The gas phase treatment device 50 is connected to the wastewater treatment device 60 via 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, further concentrating the mercury-containing wastewater. The evaporator 61 is connected to the three-stage condenser 62 via a pipeline, allowing the high-temperature mercury-containing waste gas to pass through the three-stage condenser 62. After treatment 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 via pipelines in sequence, concentrating the mercury-containing wastewater to form mercury-containing waste liquid. After recovery, it is recycled by a mercury recovery and reuse unit. The evaporator 61 has an outlet at its lower end. The bottom sludge generated after the mercury-containing wastewater is evaporated is entrusted to a qualified unit for disposal.

[0034] The gas phase treatment device 50 is connected to the wastewater treatment device 60 through a pipeline. Specifically, the lower ends of the primary condenser 52, secondary condenser 53, freezer 54, and demister 55 are all provided with pipelines that are connected to the evaporator 61 in the wastewater treatment device 60. Mercury-containing wastewater enters the evaporator 61 through the pipeline for wastewater treatment.

[0035] 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 pipe. 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 loss and lower the flue gas temperature. The heat exchanger 41 is connected to the chimney 42 through a pipe, and the cooled flue gas is discharged into the atmosphere through the chimney 42.

[0036] It also includes a discharge device 30, which includes a screw conveyor 31. The screw conveyor 31 is equipped with a humidifier 32. Soil enters the discharge unit from the material chamber. The soil is sprayed in the screw conveyor 31 by the humidifier 32 to reduce the soil temperature to 60°C. Then the soil is output by the screw conveyor 31 and transported to the designated location by a transport vehicle.

[0037] Working principle: After pretreatment, the high-concentration mercury-contaminated soil enters the feeding device 10 through the feeding machine and enters the material chamber 21 of the indirect thermal desorption device 20 through the screw conveyor 16. The high-temperature flue gas generated in the combustion chamber 22 by the burner 23 heats the material chamber 21, thereby heating the contaminated soil in the material chamber 21 to a certain temperature, causing the mercury and its compounds to volatilize and form high-temperature gaseous substances.

[0038] High-temperature gaseous substances are drawn into the gas phase treatment device 50 by an induced draft fan. After dust removal, primary condensation, secondary condensation, and freezing by a high-temperature ceramic device 51, they pass through a demister 55 to remove moisture. Then, they undergo two stages of modified activated carbon adsorption in a primary adsorption tank 56 and a secondary adsorption tank 57 before being discharged into the atmosphere after meeting the standards.

[0039] The high-temperature flue gas generated in the combustion chamber 22 enters the high-temperature flue gas treatment device 40, passes through the heat exchanger 41 to reduce heat loss and lower the flue gas temperature, and is then discharged into the atmosphere through the chimney 42.

[0040] Soil enters the discharge device 30 from the material chamber 21, is sprayed by the humidifier 32 in the screw conveyor 31 to lower the soil temperature to 60°C, and is then discharged by the screw conveyor 31 and transported to the designated location by a transport vehicle.

[0041] In the gas phase treatment device 50, mercury-containing wastewater is generated during the process of gas phase treatment through primary condensation, secondary condensation, freezing and demister 55. This wastewater enters the wastewater treatment device 60.

[0042] In the wastewater treatment device 60, after evaporation by the evaporator 61, condensation by the condenser, and freezing by the freezer, the wastewater is concentrated to form mercury-containing waste liquid, which is then handed over to a mercury recycling unit for recycling.

[0043] In the gas phase treatment device 50, the generated high-temperature gas phase is above 450°C. After being removed by the dry high-temperature ceramic dust collector 51, it meets the requirements for subsequent condensation and freezing of the gas phase.

[0044] In the gas phase treatment device 50, the primary condenser 52 and the secondary condenser 53 are shell and tube indirect heat exchangers, equipped with air-cooled towers, and water is used as the refrigerant.

[0045] The gas phase with a temperature above 450℃ reaches 60-80℃ after passing through the first-stage condenser 52; after passing through the second-stage condenser 53, the gas phase temperature reaches 20-30℃.

[0046] 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.

[0047] The organic component of the aforementioned refrigerant is ethylene glycol;

[0048] The above-mentioned refrigerant, water and ethylene glycol are mixed in a certain proportion to form a refrigerant.

[0049] The gas phase passes through the aforementioned freezer 54, and the temperature drops to below 4°C.

[0050] In the gas phase treatment device 50, the modified activated carbon adsorption tank is filled with modified activated carbon for adsorbing mercury. It has a strong mercury adsorption capacity and an adsorption value ≥80kg / m3.

[0051] The activated carbon that has adsorbed mercury is then handed over to a mercury recovery and refining unit for further processing and recycling.

[0052] A method for thermal desorption treatment of soil contaminated with high concentrations of mercury:

[0053] Mercury-contaminated soil is heated to produce a high-temperature gas phase containing mercury at a temperature above 450°C. This high-temperature gas phase is then treated by a dust collector to remove solid particles and clean the gas phase. After condensation, the gas phase temperature is reduced to 20-30°C. After freezing, the mercury liquid is formed at a temperature below 4°C. The mercury liquid is then concentrated in an evaporator and recovered.

[0054] 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 metering belt 13 for heating to generate a high-temperature gas phase.

[0055] 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.

[0056] Furthermore, the high-temperature gas phase, after being frozen, is then adsorbed by activated carbon before being discharged, with an adsorption value ≥80kg / m3.

[0057] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A thermal desorption treatment device for high-concentration mercury-contaminated soil, characterized in that, It includes a feeding device, which includes 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 equipped with a screw conveyor, and the output end of the screw conveyor is equipped with an indirect heat desorption device. The indirect thermal desorption device includes a material chamber, a combustion chamber below the material chamber, and a burner below the combustion chamber; The tail end of the material chamber is equipped with a gas phase treatment device, which 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 primary condenser through a pipe. The primary condenser is connected to the upper end of the secondary condenser through a pipe. The secondary condenser is connected to the upper end of the freezer through a pipe. The freezer is connected to the demister through a pipe. The demister is connected to the upper end of the primary adsorption tank through a pipe. The primary adsorption tank is connected to the upper end of the secondary adsorption tank through a pipe.

2. The thermal desorption treatment device for high-concentration mercury-contaminated soil according to claim 1, characterized in that, The gas phase treatment device is connected to the wastewater treatment device via a pipeline. The wastewater treatment device includes an evaporator, which is connected to a three-stage condenser via a pipeline. The three-stage condenser is connected to a first-stage freezer and a second-stage freezer in sequence via pipelines.

3. The thermal desorption treatment device for high-concentration mercury-contaminated soil according to claim 2, characterized in that, The lower ends of the primary condenser, secondary condenser, freezer, and demister are all provided with pipes that connect to 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 1-3, characterized in that, It also includes a high-temperature flue gas treatment unit, which includes a heat exchanger connected to the combustion chamber via a pipe and connected to the chimney via a pipe.

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

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

Images