A thermal plasma apparatus and method for continuous treatment of hazardous waste

Abstract

The application discloses a kind of continuous processing hazardous waste thermal plasma device and method, including plasma smelting gasification furnace, gas mixing stirring device, reforming two combustion chamber, heat exchanger, washing tower, bag-type dust collector, gas purification collection device.The application utilizes thermal plasma to melt inorganic matter in hazardous waste into molten liquid, then as raw material in molten mould, so that harmful substances are fixed therein and meet the national leaching standard, flue gas is reformed into high-quality synthesis gas by reforming two combustion chamber;An environment-friendly, safe and reliable treatment process, wide treatment range, high, medium and low calorific value hazardous waste can be treated, and the discharged solid waste and flue gas achieve the purpose of reduction, harmlessness and resource utilization.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste treatment technology, and in particular to a thermal plasma device and method for continuous treatment of hazardous waste. Background Technology

[0002] The most common methods for disposing of hazardous waste are solidification and landfill, and incineration. Solidification and landfill occupy a large amount of land and severely pollute the soil, groundwater, and atmosphere. The incineration process produces secondary pollutants such as heavy metals and dioxins, which remain in large quantities in the slag and are still classified as hazardous waste, thus becoming a new source of pollution.

[0003] Furthermore, thermal plasma technology is an ideal method for treating hazardous waste, overcoming the shortcomings of traditional solidification, landfill, and incineration. However, most existing plasma waste treatment equipment has a large furnace volume, resulting in long heating times and significant heat loss. When continuously processing hazardous waste, it only treats a single type of hazardous waste, without considering whether the material is fed evenly or how to adjust the feeding speed. It also lacks effective treatment and reasonable utilization of the exhaust gases and molten liquid. Furthermore, using reducing or oxidizing atmospheres can lead to complex exhaust gas treatment in the later stages. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a thermal plasma device and method for continuous treatment of hazardous waste, so as to achieve the reduction, harmless treatment and resource utilization of hazardous waste.

[0005] The objective of this invention is achieved as follows:

[0006] A continuous thermal plasma device for processing hazardous waste includes a plasma melting and gasification furnace. The furnace comprises a plasma melting and gasification chamber and a melting pool. The plasma melting and gasification chamber is fixedly located above the melting pool, and its lower end is connected to the upper end of the melting pool. A refractory insulation layer is formed between the furnace wall and the plasma melting and gasification chamber. The upper part of the furnace body has three side openings: two reserved gas inlets and a flue gas exhaust pipe. Multiple thermocouples, thermometers, and pressure gauges are installed around the furnace body to monitor the temperature and pressure distribution within the furnace chamber. The furnace wall has three glass observation holes corresponding to the plasma melting and gasification chamber, the constricted structure, and the melting pool, respectively. The plasma melting and gasification chamber includes a preheating chamber and a spiral... The preheating chamber is equipped with a feeding device and a material pushing device, which correspond to the feeding ends of a pair of screw feeders. The feeding ends of the screw feeders are connected to the preheating chamber. The discharge port (downstream end of the discharge pipe) is located directly above the crucible. The crucible is located between the plasma melting and vaporization chamber and the melting pool. It is equipped with a liquid level detection sensor and a temperature sensor. The bottom of the crucible is equipped with a hydraulic valve connected to the central discharge through hole, which is connected to the melting pool. A plasma generator is installed on the upper side of the crucible to generate a thermal plasma arc to heat the crucible. The residual heat can also be transmitted through the crucible to heat the melting pool and prevent solidification. A high-frequency induction heating coil is installed on the wall of the melting pool. A liquid level detection gauge is installed in the melting pool. An inclined discharge channel connected to a discharge valve is located on the lower left side of the melting pool and is connected to an external melting mold container.

[0007] The plasma generator is a non-transfer arc DC plasma torch, which uses nitrogen as the plasma working medium and is connected to a nitrogen generator.

[0008] The thermal plasma torches are symmetrically arranged around the crucible in the plasma melting and vaporization chamber, with the central axis of the middle glass observation window as the line of symmetry. There are two, four, or six DC plasma torches, each connected to an external power source.

[0009] The feeding device connected above the preheating chamber includes a primary silo, a secondary silo, a nitrogen purging device, and corresponding control valves.

[0010] The flue gas reforming and purification system includes an induced draft fan, a gas mixing and stirring device, a reforming secondary combustion chamber, a heat exchanger, a scrubbing tower, a bag filter, and a gas purification and collection device connected in sequence.

[0011] A treatment method based on a thermal plasma device for continuous treatment of hazardous waste, and a thermal plasma device for continuous treatment of multiple types of hazardous waste: comprising a plasma melting and gasification furnace, a gas mixing and stirring device, a reforming secondary combustion chamber, a heat exchanger, a scrubbing tower, a bag filter, and a gas purification and collection device; the plasma melting and gasification furnace is connected by a conduit to the gas mixing and stirring device 34, the reforming secondary combustion chamber, the heat exchanger, the scrubbing tower, the bag filter, and the gas collection device in sequence, including the following steps:

[0012] (1) Start the nitrogen generator and steam generator, open the secondary silo valve and slurry discharge valve, start the nitrogen purging device to purge the gas in the entire system with nitrogen, and then exhaust the gas through the slurry discharge channel to keep the plasma melting gasification furnace in an inert state. Then, open all valves, introduce the plasma working gas nitrogen into the plasma generator and start the plasma discharge power supply to generate a hot plasma jet. The furnace is heated to 1400-1700℃ by the high temperature generated by the hot plasma jet.

[0013] (2) Hazardous waste is poured into the primary silo. The valve of the primary silo is opened. After the hazardous waste enters the secondary silo, the valve is closed. The secondary silo is connected to a nitrogen purging device to purge the air in the silo and make the air pressure in the chamber higher (higher than the plasma melting and gasification chamber and the preheating chamber). The valve of the secondary silo is opened. After the hazardous waste enters the preheating chamber, the valve is closed. The waste is preheated by high-temperature gas in the furnace (the high-temperature gas continuously generated in the furnace will rise spirally along the spiral gas pipe). After a period of time, the screw feeder is opened. The screw feeder pushes the hazardous waste into the plasma melting and gasification chamber. The feeding rate of the screw feeder is controlled according to the temperature of the molten liquid in the crucible. The liquid level detection sensor automatically or manually controls the hydraulic valve to ensure that the waste has sufficient temperature and melting and gasification time in the furnace to be thoroughly processed.

[0014] (3) After plasma incineration, hazardous waste forms a molten liquid that flows from the crucible into the molten pool. The slurry outlet valve is opened, and the molten liquid flows out from the outlet, providing molten liquid for various investment casting molds. The exhaust gas after incineration is mixed with water vapor by an induced draft fan and a gas flow controller into a gas stirring and mixing device for uniform mixing in proportion. It then enters the reforming secondary combustion chamber, where the mixed gas is further converted into high-quality syngas under the action of the plasma torch. The reforming secondary combustion chamber is equipped with baffles and vents to prolong the residence time of the gas in the secondary combustion chamber. After reforming, the high-quality syngas obtained is separated, purified, and collected after being treated by a heat exchanger, a scrubbing tower, and a bag filter.

[0015] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0016] This invention utilizes thermal plasma to melt inorganic substances in hazardous waste into a molten liquid, which is then used as raw material in a melting mold, fixing harmful substances within it to meet national leaching standards. The flue gas is then reformed into high-quality syngas through a reforming secondary combustion chamber. This invention provides an environmentally friendly, safe, and reliable treatment process with a wide range of applications, capable of treating hazardous waste with high, medium, and low calorific values. The emitted solid waste and flue gas achieve the goals of harmlessness and resource utilization.

[0017] This system can simultaneously process hazardous waste with high, medium, and low calorific values. To prevent excess oxygen from being introduced into the plasma melting and gasification chamber from the feed inlet, gas purging is performed before the solid enters the preheating chamber, and the pressure in the secondary silo is increased to be higher than that in the preheating chamber to facilitate feeding. Simultaneously, before startup, the entire system is purged with nitrogen, and the plasma generator uses nitrogen as its working gas, ensuring that the system operates in a nitrogen environment throughout the entire process. This suppresses oxidation reactions within the furnace, minimizing the formation of dioxins and NOx, thus meeting environmental protection requirements.

[0018] In this system, the furnace chamber is relatively compact, resulting in rapid heating and minimal heat loss. High-temperature gas inside the furnace, passing through a spiral gas channel, can preheat hazardous waste in the preheating chamber before plasma treatment, thus reducing energy consumption.

[0019] In this system, the feed rate of the screw feeder is adjusted according to the temperature of the molten liquid in the crucible to ensure uniform feeding of hazardous waste. The liquid level gauge automatically or manually controls the opening and closing of the hydraulic valve to discharge the molten liquid, so as to ensure that the waste maintains the required melting and gasification time in the furnace.

[0020] The system has two glass observation windows, which allow for easy observation of the furnace interior and also serve as windows for replacing parts and performing maintenance.

[0021] In this system, a gas inlet is provided on the plasma furnace to introduce various gases to change the proportion of each component in the waste gas generated in the furnace. A gas mixing device is provided between the plasma furnace and the reforming secondary combustion chamber, which can precisely adjust the ratio of water vapor and exhaust gas and mix them evenly, thereby improving the conversion rate of exhaust gas and obtaining more high-quality syngas.

[0022] In this system, a large-capacity molten pool can provide molten liquid for a wider variety of investment casting molds, and a high-frequency induction heating coil is installed on the outside of the molten pool wall to ensure that the molten liquid does not solidify into slag or adhere to the molten pool. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention;

[0024] Figure 2 yes Figure 1 The plasma melting gasification furnace in the middle;

[0025] Figure 3 yes Figure 2 Main view of the plasma melting gasification furnace in the image;

[0026] Figure 4a This is a top cross-sectional view of two plasma torches (plasma generators) arranged in the plasma melting and gasification furnace of the present invention;

[0027] Figure 4b This is a top cross-sectional view of the plasma melting and gasification furnace of the present invention, in which four plasma torches (plasma generators) are arranged.

[0028] Figure 5 This is a schematic diagram of the external structure of the preheating chamber.

[0029] Figure Labels

[0030] In the attached diagram: 1. Primary silo; 2. Primary silo valve switch; 3. Secondary silo; 4. Nitrogen purging device; 5. Secondary silo valve switch; 6. Material pushing device; 7. Furnace wall; 8. Thermal insulation layer; 9. Reserved gas inlet; 10. Preheating chamber; 11. Screw feeder; 12. Plasma generator; 13. Crucible; 14. Thermocouple; 15. Liquid level gauge; 16. Melting pool; 17. Slurry discharge valve; 18. Slurry discharge port; 19. High-frequency induction heating coil; 20. Hydraulic valve; 21. Feed pipe; 22. Motor; 23. Reducer; 24. L-shaped pusher; 25. Pressure gauge; 26. Temperature gauge. Table 27. Flue gas emission duct, 28. Gas sampling port, 29. Spiral gas channel, 30. Hydraulic press, 31. Exhaust fan, 32. Gas flow controller, 33. Gas duct, 34. Gas mixing device, 35. Gas mixing device outlet, 36. Secondary combustion chamber inlet, 37. Secondary combustion chamber plasma torch, 38. Secondary combustion chamber heat insulation layer, 39. Reforming secondary combustion chamber, 40. Baffle, 41. Vent, 42. Heat exchanger, 43. Scrubber, 44. Bag filter, 45. Gas purification and collection device, 46. Nitrogen generator, 47. Steam generator, 48. Glass observation window. Detailed Implementation

[0031] See also Figure 1 , 23, 4a, 4b, 5, A continuous thermal plasma device for processing hazardous waste includes a plasma melting and gasification furnace. The plasma melting and gasification furnace includes a feeding section, a plasma melting and gasification chamber, and a melting pool 16. The feeding section consists of a primary silo 1 and a secondary silo 3, which are individually controlled by a primary silo valve switch 2 and a secondary silo valve switch 5. The secondary silo 3 is equipped with a nitrogen purging device 4 and connected to a nitrogen reactor 46. The plasma melting and gasification chamber consists of a preheating chamber 10 and a crucible 13. The preheating chamber 10 is equipped with a material pushing device 6, an L-shaped pusher 24, and a screw feeder 11. The L-shaped pusher 24 is controlled by a hydraulic press 30 to push the material. The screw feeder 11 is connected to a motor and a reducer outside the furnace body. The preheating chamber 10 is provided with a spiral gas channel 29. The upper part is equipped with two reserved gas inlets 9; plasma generators 12 are symmetrically arranged diagonally above the crucible 13 and connected to a nitrogen reactor 46, and connected to a hydraulic valve 20 below. Thermocouples 14 and liquid level gauges 15 are arranged around the crucible, and the outside is connected to a glass observation window 48; the melting pool 16 is equipped with thermocouples 14, liquid level gauges 15, high-frequency heating induction coils 19, slurry discharge valves 17 and slurry discharge ports 18; the waste gas treatment generated in the plasma melting gasification furnace includes a flue gas emission channel 27, which, under the action of a steam generator 47 and an induced draft fan 31, sequentially introduces steam and waste gas through a gas duct 33 into a gas mixing and stirring device 34, a reforming secondary combustion chamber 39, a heat exchanger 42, a scrubbing tower 43, a bag filter 44, and a gas purification and collection device 45. This system is completely sealed during operation. The upper part of the furnace body is equipped with a gas replenishment system, which is connected to the end of a spiral gas channel to change the proportion of various components in the waste gas. In this embodiment, the gas replenishment system has two reserved gas inlets 9 for introducing gases of different compositions.

[0032] The method for treating hazardous waste using the above-mentioned apparatus includes the following steps:

[0033] (1) Start the nitrogen generator 46 and the steam generator 47, open the secondary silo valve 5 and the slurry discharge valve 17, start the nitrogen purging device to purge the gas in the entire system with nitrogen, and then exhaust the gas through the slurry discharge channel to keep the plasma melting gasification furnace in an inert state. Then, open all valves, introduce the plasma working gas nitrogen into the plasma generator 46 and start the plasma discharge power supply to generate a hot plasma jet. The high temperature generated by the hot plasma jet heats the furnace chamber 7 to 1400-1700℃.

[0034] (2) Hazardous waste is poured into the primary silo 1. The primary silo valve 2 is opened. After the hazardous waste enters the secondary silo 3, valve 2 is closed. The secondary silo 3 is connected to the nitrogen purging device 4, which purges the air in the silo and makes the air pressure in the chamber higher (higher than the plasma melting and gasification chamber and the preheating chamber). The secondary silo valve 5 is opened. After the hazardous waste enters the preheating chamber 10, valve 5 is closed. The waste is preheated by the high-temperature gas in the furnace (the high-temperature gas continuously generated in the furnace will spiral upward along the spiral gas pipe 29). After a period of time, the spiral feeder 11 is opened. The spiral feeder 11 pushes the hazardous waste into the plasma melting and gasification chamber. The feeding rate of the spiral feeder is controlled according to the temperature of the molten liquid in the crucible 13. The liquid level detection sensor automatically or manually controls the hydraulic valve switch to ensure that the waste has sufficient temperature and melting and gasification time in the furnace to be thoroughly processed.

[0035] (3) After plasma incineration, the hazardous waste forms a molten liquid that flows from crucible 13 into melting pool 16. The slurry discharge valve 17 is opened, and the molten liquid flows out from discharge port 18, providing molten liquid for various investment casting molds. The exhaust gas after incineration is mixed with water vapor by induced draft fan 31 and gas flow controller 32 into gas stirring and mixing device 34, where it is mixed evenly in proportion. It then enters reforming secondary combustion chamber 39, where the mixed gas is further converted into high-quality syngas under the action of plasma torch 37. The reforming secondary combustion chamber is equipped with baffles 40 and vents 41 to prolong the residence time of the gas in the secondary combustion chamber. After reforming, the high-quality syngas is first processed by heat exchanger 42, scrubbing tower 43, and bag filter 44 before being separated, purified, and collected.

[0036] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A thermal plasma device for continuous processing of hazardous waste, characterized in that: The system includes a plasma melting and gasification furnace. Inside the furnace, from top to bottom, are arranged a preheating chamber, a plasma melting and gasification chamber, and a melting pool. A constricting structure connects the plasma melting and gasification chamber and the melting pool. Within this constricting structure are a plasma generator and a crucible. The plasma generator is located above the crucible and generates a thermal plasma arc to heat the crucible. The bottom of the crucible is conical, and a hydraulic valve is installed at the bottom. The lower end of the hydraulic valve is connected to a central discharge port. When the hydraulic valve is open to discharge material, the central discharge port connects to the plasma melting and gasification chamber and the melting pool. A spiral gas channel surrounds the outside of the preheating chamber. The lower end of the spiral gas channel is connected to the plasma melting and gasification chamber and is used to input high-temperature gas. A flue gas exhaust pipe is connected at the uppermost corner of the spiral gas channel. The flue gas exhaust pipe extends out of the plasma melting and gasification furnace and is connected to a flue gas reforming system. The purification system includes a feeding device connected above the preheating chamber. A pair of screw feeders are symmetrically arranged laterally below the preheating chamber, with their feed ends connected to the preheating chamber. The preheating chamber contains a feeding device and a material pushing device. The feeding device includes a core seat with a stepped shape (smaller at the top, larger at the bottom). L-shaped pusher plates are symmetrically arranged on both sides of each step of the core seat. A hydraulic cylinder is located in the center of the core seat corresponding to each L-shaped pusher plate. The vertical plate of each L-shaped pusher plate is connected to the corresponding hydraulic cylinder. The lower L-shaped pusher... The flat plate of the sheet blocks the material between the vertical plate of the adjacent upper L-shaped pusher sheet. The hydraulic cylinder is used to push the material out of the corresponding step of the core seat. The material pushing device is corresponding to the outer edge of the feeding device and the feeding end of the screw feeder. The material pushing device is used to push the material into the screw feeder. The discharge end of the screw feeder is connected to the discharge pipe. The discharge port of the discharge pipe extends downward toward the crucible. The screw feeder is used to transport the material in the preheating chamber into the crucible. The melting pool is equipped with a discharge valve and a discharge channel. The plasma melting and gasification furnace is equipped with thermocouples, temperature gauges, and pressure gauges on its furnace body; the crucible is equipped with thermocouples and liquid level gauges at its upper end. The outer wall of the molten pool is equipped with a high-frequency induction heating coil, which is used to prevent the molten liquid from solidifying. A liquid level detection gauge is installed in the molten pool. The bottom surface of the molten pool is inclined. The bottom of the molten pool is equipped with the discharge valve and discharge channel, which are connected to the external molten mold container. The feeding device includes a primary silo and a secondary silo arranged sequentially from top to bottom. A primary silo valve switch is provided between the primary silo and the secondary silo, and a secondary silo valve switch is provided between the secondary silo and the preheating chamber. The secondary silo is connected to a nitrogen purging device. It also includes a nitrogen generator, which is connected to a plasma generator and a nitrogen purging device. The plasma generator is a non-transfer arc DC plasma torch that uses nitrogen as the plasma working medium.

2. The thermal plasma device for continuous treatment of hazardous waste according to claim 1, characterized in that: The plasma melting gasification furnace is equipped with a rectangular partition wall, which isolates the upper space inside the plasma melting gasification furnace into a preheating chamber. Each hydraulic cylinder is controlled by a hydraulic press outside the furnace body. The furnace body of the plasma melting and gasification furnace includes a furnace wall and a heat insulation layer installed inside the furnace wall. The furnace wall is provided with two glass observation holes, which correspond to the constriction structure and the melting pool, respectively. There are multiple plasma generators, which are symmetrically arranged around the crucible above the central axis of the corresponding glass observation window.

3. The thermal plasma device for continuous treatment of hazardous waste according to claim 1, characterized in that: The flat plate of the L-shaped pusher is clearance-fitted with the core seat, and the flat plate of the lower L-shaped pusher is slidingly fitted with the vertical plate of the adjacent upper L-shaped pusher. Alternatively, there is a gap between the flat plate of the lower L-shaped pusher and the vertical plate of the adjacent upper L-shaped pusher, and this gap is smaller than the particle size of the material.

4. The thermal plasma device for continuous treatment of hazardous waste according to claim 1, characterized in that: The flue gas reforming and purification system includes an induced draft fan, a gas flow controller, a gas mixing and stirring device, a reforming secondary combustion chamber, a heat exchanger, a scrubbing tower, a bag filter, and a gas purification and collection device, which are connected in sequence by ducts. The gas mixing and stirring device is connected to a steam generator, and the heat exchanger is used to output heat energy through heat exchange.

5. The thermal plasma device for continuous treatment of hazardous waste according to claim 1, characterized in that: The upper part of the furnace body is equipped with a gas replenishment system, which is connected to the end of the spiral gas channel to change the proportion of each component in the exhaust gas.

6. A method for operating a thermal plasma device for continuous treatment of hazardous waste as described in claim 1, characterized in that, It includes the following steps: (1) Start the nitrogen generator and steam generator, close the primary silo valve switch, open the secondary silo valve switch, turn on the nitrogen purging device to introduce nitrogen to keep the plasma melting gasification furnace in an inert state, then close the secondary silo valve switch, introduce the nitrogen generated by the nitrogen generator into the plasma generator, turn on the plasma generator and generate a hot plasma jet, and heat the furnace of the plasma melting gasification furnace to 1400-1700℃ through the high temperature generated by the hot plasma jet; (2) Pour the hazardous waste into the primary silo, open the valve of the primary silo and close the valve after the hazardous waste enters the secondary silo. Use a nitrogen purging device to purge the air in the secondary silo and make the air pressure in the chamber higher than that in the preheating chamber. Open the valve of the secondary silo and close the valve after the hazardous waste enters the preheating chamber. Use the high-temperature gas in the furnace to preheat through the spiral gas channel. Then start the feeding device, open the material pushing device and the screw feeder. The material pushing device pushes the material into the screw feeder. The screw feeder pushes the hazardous waste into the crucible. The hazardous waste is heated and burned by the isothermal plasma arc to form a molten liquid. The feeding rate of the screw feeder is controlled according to the temperature of the molten liquid in the crucible to ensure that the hazardous waste is kept in the crucible for the required melting and gasification time. The hydraulic valve is automatically or manually controlled by the liquid level detection gauge at the crucible to discharge the molten liquid into the melting pool. (3) The molten liquid flows from the crucible into the molten pool, the slurry valve is opened, the molten liquid flows out of the discharge port, and provides molten liquid to the investment casting mold.

7. The processing method according to claim 6, characterized in that: The exhaust gas after incineration passes through a flue gas emission pipe, an induced draft fan, and a gas flow controller. After being mixed with water vapor, it enters a gas mixing device for uniform mixing in a specific ratio. The mixed gas then enters the reforming secondary combustion chamber, where it is further converted into high-quality syngas under the action of a plasma torch. The reforming secondary combustion chamber is equipped with baffles and vents to prolong the residence time of the gas in the chamber. After reforming, the gas first passes through a heat exchanger, a scrubbing tower, and a bag filter before being separated, purified, and collected.

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