Hazardous waste harmless treatment system and method based on high-temperature plasma

Abstract

The invention discloses a hazardous waste harmless treatment system and method based on high-temperature plasma, and belongs to the technical field of hazardous waste treatment. The system comprises a pretreatment and feeding unit, a plasma melting furnace, a quench tower, a waste heat recovery and purification unit and a slag treatment unit. The method comprises the following steps: pre-treating the hazardous waste, feeding the hazardous waste into a plasma melting furnace, thoroughly cracking organic matters into synthesis gas at the high temperature of 1200-1600 DEG C, and melting inorganic matters to form vitreous slag; the synthesis gas is instantaneously cooled by a quench tower to prevent resynthesis of dioxin, and is discharged after reaching the standard after being subjected to waste heat recovery and deep purification; and the slag is subjected to water quenching to form stable and harmless glass body particles for resource utilization. According to the method, thorough harmlessness, reduction and recycling of the hazardous waste are achieved, the risk of secondary pollution is low, and the energy utilization efficiency is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hazardous waste treatment, in particular to a hazardous waste harmless treatment system and method based on high-temperature plasma. BACKGROUND

[0002] With the rapid development of industry, the output of hazardous waste is increasing, which poses a great potential threat to the environment and human health. Traditional hazardous waste treatment technologies, such as incineration, safe landfill, and chemical stabilization, have the following obvious shortcomings:

[0003] Incineration technology: For hazardous waste with complex composition, traditional incineration temperature (usually 850℃-1150℃) is difficult to completely decompose persistent organic pollutants such as dioxins and furans, and secondary pollution such as acid gas and fly ash is easy to produce.

[0004] Safe landfill: not only occupies a large amount of land resources, but also has the risk of long-term leakage polluting soil and groundwater, and is not truly "harmless".

[0005] Chemical stabilization: incomplete treatment, and the stabilized product may release toxic substances again under environmental conditions.

[0006] High-temperature plasma technology can completely crack organic pollutants in hazardous waste into small molecular gases (such as CO, H2, etc.) and solidify heavy metals and other inorganic components in glass body slag due to its extremely high temperature (up to 5000℃ or more), high energy density, and strong ultraviolet radiation, achieving complete detoxification and stabilization. However, the existing plasma treatment system has problems such as low energy utilization efficiency, uneven feeding leading to system operating condition fluctuation, and imperfect tail gas treatment. SUMMARY

[0007] The purpose of the present application is to provide a hazardous waste harmless treatment system and method based on high-temperature plasma with high energy utilization rate, complete treatment, stable operation, and low risk of secondary pollution, to solve the problems raised in the background art.

[0008] The technical solution adopted by the present application is as follows:

[0009] The hazardous waste harmless treatment system based on high-temperature plasma comprises:

[0010] A pretreatment and feeding unit 1 for preparing and conveying the material;

[0011] A plasma melting furnace 2 connected with the pretreatment and feeding unit 1 for cracking, gasification, and melting of hazardous waste under high-temperature plasma environment;

[0012] A quench tower 3 is connected with a syngas outlet of the plasma melting furnace 2, and used for rapidly cooling high-temperature syngas;

[0013] A waste heat recovery and purification unit 4 is connected with the quench tower 3, and used for recovering waste heat and deeply purifying the cooled syngas.

[0014] A slag treatment unit 5 is connected with a slag discharge port of the plasma melting furnace 2, and used for water quenching and resourceful treatment of generated slag.

[0015] The pretreatment and feeding unit 1 comprises a storage subsystem, a pretreatment subsystem and a feeding subsystem. The storage subsystem comprises a receiving and temporary storage bin and a hazardous waste characteristic analysis and compounding area. The pretreatment subsystem comprises a coarse crushing and fine crushing module and a homogenization and adjustment module. The feeding subsystem comprises a water-cooled jacketed double-screw feeder and a metering and control system. The bin body of the receiving and temporary storage bin is of a closed structure, and the inner wall is made of corrosion-resistant and wear-resistant material. A closed feeding port with an interlocking device and a bag-type dust collector are arranged on the top of the bin, so as to prevent dust from escaping during unloading. The bottom of the bin is designed to be conical, and is supplemented by a high-frequency bin wall vibrator or an air cannon, so as to prevent bridging and arching of materials.

[0016] The plasma melting furnace 2 comprises a plasma torch system, and the plasma torch system comprises at least two plasma torches. The two plasma torches are symmetrically installed on the upper side wall of the furnace body at an angle of 15°-30° with respect to the vertical line.

[0017] The plasma melting furnace 2 further comprises a furnace shell and a refractory lining, a feeding port, a molten pool and a slag outlet, and a syngas outlet. The furnace shell is of a double-layer steel plate structure, and the inner layer is made of heat-resistant steel plate, the outer layer is made of ordinary carbon steel, and the interlayer is filled with thermal insulation material. The refractory lining is of a composite lining structure, and comprises, from the inside to the outside, a hot face layer, a backing layer and a thermal insulation layer. The feeding port is located at the upper part of the furnace body, and is sealingly connected with the water-cooled jacketed double-screw feeder of the pretreatment and feeding unit 1 through a flange. The slag outlet is located at the lowest point of the furnace bottom, and is of a water-cooled copper jacket structure. The syngas outlet is located at the top of the furnace body.

[0018] A plurality of high-temperature thermocouples are arranged in the furnace body of the plasma melting furnace 2, so as to monitor the temperature in real time. A high-temperature camera observation hole is arranged on the furnace body, so as to facilitate direct observation of the flame and molten pool state in the furnace. A pressure sensor is installed on the top of the furnace chamber.

[0019] The quench tower 3 is provided with an atomizing spray system, and can cool the high-temperature syngas at ≥800℃ to below 200℃ within 1 second.

[0020] The waste heat recovery and purification unit 4 includes, in sequence, a waste heat boiler, a bag filter, an acid gas scrubbing tower, and a flue gas reheating and emission system. The top of the acid gas scrubbing tower is equipped with a high-efficiency demister, and the flue gas reheating and emission system includes a reheater, an induced draft fan, and a chimney.

[0021] The slag processing unit 5 includes a water quenching tank for rapidly cooling molten slag to form glassy particles. A high-pressure water jet nozzle is installed above the slag impact point in the water quenching tank; a gas collection hood is installed above the water quenching tank.

[0022] A method for harmlessly treating hazardous waste using the system described above includes the following steps:

[0023] S1: Hazardous waste is pretreated and continuously fed into the plasma melting furnace through the feeding unit;

[0024] S2: In a plasma melting furnace, the high temperature generated by the plasma torch causes hazardous waste to undergo cracking, gasification and melting reactions, generating syngas and glass slag.

[0025] S3: The high-temperature synthesis gas generated in step S2 is introduced into a quench tower for rapid cooling.

[0026] S4: Perform waste heat recovery, dust removal, and acid gas removal on the cooled syngas;

[0027] S5: The molten slag produced in step S2 is water-quenched to form stable glassy particles.

[0028] In step S2, the reaction temperature in the plasma melting furnace is controlled at 1200℃-1600℃; in step S3, the rapid cooling process cools the synthesis gas from ≥800℃ to below 200℃ within 1 second.

[0029] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] 1. Thorough treatment and high degree of harmlessness: The ultra-high temperature in the plasma core area can completely destroy all organic pollutants, including the most difficult-to-degrade dioxins; inorganic heavy metals are permanently solidified in the glass slag, with extremely low leaching toxicity.

[0031] 2. High energy utilization rate: By recovering the waste heat of syngas through a waste heat boiler, the generated steam can be used for power generation or heating, reducing the energy consumption of the system operation.

[0032] 3. Extremely low risk of secondary pollution: The core technology of "quench tower" effectively curbs the resynthesis of dioxins; the complete exhaust gas purification system ensures that the final emissions meet the standards.

[0033] 4. High degree of resource utilization: The generated syngas can be reused as energy, and the glass slag can be used as building materials, realizing the resource recycling of waste.

[0034] 5. Stable system operation: The water-cooled feeding system and optimized furnace structure design ensure long-term, stable and safe operation of the system. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the system of the present invention;

[0036] Figure 2 This is a schematic diagram of the plasma melting furnace structure of the present invention;

[0037] The diagram shows: 1. Pretreatment and feeding unit; 2. Plasma melting furnace; 3. Quenching tower; 4. Waste heat recovery and purification unit; 5. Slag treatment unit. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0039] Example

[0040] like Figure 1 As shown, this embodiment specifically provides a hazardous waste harmless treatment system based on high-temperature plasma, including:

[0041] Pre-processing and feeding unit 1 is used for material preparation and conveying;

[0042] The plasma melting furnace 2, connected to the pretreatment and feeding unit 1, is used to pyrolyze, gasify and melt hazardous waste in a high-temperature plasma environment.

[0043] The quench tower 3 is connected to the syngas outlet of the plasma melting furnace 2 and is used to rapidly cool the high-temperature syngas.

[0044] Waste heat recovery and purification unit 4 (which includes a waste heat boiler, a bag filter, an acid gas scrubbing tower, and a flue gas reheating and emission system) is connected to the quench tower 3 and is used to recover waste heat and deeply purify pollutants from the cooled syngas.

[0045] The slag treatment unit 5 is connected to the slag discharge port of the plasma melting furnace 2 and is used to perform water quenching and resource recovery treatment on the generated slag.

[0046] The pretreatment and feeding unit 1 includes a storage subsystem, a pretreatment subsystem, and a feeding subsystem. The storage subsystem includes a receiving and temporary storage bin and a hazardous waste characteristic analysis and compatibility area. The pretreatment subsystem includes coarse crushing and fine crushing modules and a homogenization and blending module. The feeding subsystem includes a water-cooled jacketed twin-screw feeder and a metering and control system. The receiving and temporary storage bin has a sealed structure with corrosion-resistant and wear-resistant materials on the inner wall. The top of the bin is equipped with a sealed feed inlet with an interlocking device and a bag filter to prevent dust from escaping during unloading. The bottom of the bin is designed as a cone shape and is supplemented with a high-frequency bin wall vibrator or air cannon to prevent material bridging and sloshing.

[0047] The pretreatment and feeding unit 1 receives hazardous waste from different sources and in various forms. Through a series of physical processes, it transforms the waste into homogeneous and stable materials that meet the feeding requirements of the plasma melting furnace 2, and achieves continuous, stable, measurable, and sealed transport to the high-temperature, negative-pressure reaction environment. This unit is mainly composed of three organically linked parts: a storage subsystem, a pretreatment subsystem, and a feeding subsystem.

[0048] The storage subsystem includes receiving and temporary storage bins: used to receive incoming materials. The bin body is a sealed structure, with the inner wall made of corrosion-resistant and wear-resistant materials (such as 316L stainless steel or lined with wear-resistant ceramic). The top of the bin is equipped with a sealed feed inlet with an interlocking device and a bag filter to prevent dust from escaping during unloading. The bottom of the bin is designed as a cone shape, supplemented by a high-frequency bin wall vibrator or air cannon to prevent material bridging and sloshing.

[0049] The storage subsystem also includes a hazardous waste characteristic analysis and compatibility area: this area comprises a set of management processes and technical solutions. Before waste enters the main treatment line, it needs to undergo rapid testing and analysis (such as calorific value, moisture content, heavy metal content, halogen content, etc.). Based on the analysis results, an intelligent compatibility software system calculates the mixing ratio of different wastes, aiming to achieve stable calorific value, controllable composition, and balanced proportions of elements such as chlorine and sulfur in the furnace feed material, thereby avoiding drastic changes in furnace conditions and impacts on tail gas treatment load caused by material fluctuations from the source.

[0050] The pretreatment subsystem includes coarse crushing and fine crushing modules. Specifically, it includes coarse crushing equipment: for large blocks, drums, or packaged materials, a twin-shaft shear crusher is used for coarse crushing. Its blades are made of special alloy steel, possessing high hardness and toughness, easily shearing metal drums, plastic drums, and fibrous fabrics. It also includes fine crushing equipment: the material after coarse crushing is transferred to the fine crushing stage via a belt conveyor, where a high-speed rotary crusher or hammer crusher is used to crush the material into uniform particles with a diameter of less than 50mm, increasing the specific surface area and ensuring subsequent homogenization and melting reaction rate.

[0051] The pretreatment subsystem also includes a homogenization and blending module, specifically a homogenization mixer: either a twin-shaft mixer or a drum mixer. This equipment can thoroughly mix crushed waste of different forms (solid, semi-solid) and from different sources, ensuring that the physicochemical properties of each batch of feed are relatively uniform. The mixer is also a closed structure, equipped with a liquid spraying device, which can quantitatively add liquid waste (such as waste solvents, waste oil) or moisture regulators according to the formulation plan to achieve solid-liquid mixing.

[0052] The pretreatment subsystem also includes a buffer hopper: located below the mixer, it is used to temporarily store homogenized materials and serves as a buffer hopper for the feeding subsystem to ensure continuous feeding.

[0053] The feeding subsystem includes a water-cooled jacketed twin-screw feeder, which, compared to a single-screw feeder, offers greater pushing force and more stable conveying, effectively preventing bridging and material accumulation at the feed inlet. The spiral blades and shell are made of wear-resistant and high-temperature-resistant alloy materials. A fully enclosed water-cooled jacket, circulated with cooling water, is installed outside the feeder shell. The water-cooled jacket effectively isolates the high temperature inside the plasma melting furnace from conduction to the feeder, protecting the equipment body and internal components, and preventing premature decomposition, coking, or even combustion of materials within the feeder due to heat. This ensures that the material conveyed to the furnace maintains its pre-treated original state, avoiding property changes caused by preheating.

[0054] The feeder and the plasma melting furnace inlet are connected by a flange and equipped with a nitrogen purging sealing device. By continuously introducing low-pressure nitrogen at this interface, a "gas curtain" is formed, which effectively prevents the syngas from leaking out of the furnace, avoids air entering the furnace and disrupting the reducing atmosphere, and also cools the interface components.

[0055] The water-cooled jacketed twin-screw feeder integrates a weighing module (weighing sensor) and a speed sensor to monitor and calculate the instantaneous and cumulative feed rates in real time. This weighing module and speed sensor, along with the feeder drive motor and the power controller of the plasma torch, form a closed-loop control system. When fluctuations in the feed rate are detected, the system automatically adjusts the feeder speed or fine-tunes the plasma torch power to ensure a "material-energy" balance—that is, the material input and energy input are always matched—maintaining a stable furnace temperature and achieving optimal processing results and energy efficiency.

[0056] Dust-generating hoods are installed at various dust-generating points and material transfer points in the storage and pre-treatment areas. The collected dust- and odor-containing gases are directed to a pre-treatment exhaust gas treatment system (including a scrubbing tower, activated carbon adsorption device, etc.) for purification before being discharged, thus protecting the workshop environment.

[0057] Throughout the unit, especially in the storage and crushing areas, an automatic fire suppression system (heptafluoropropane gas fire suppression system or ultrafine dry powder fire suppression system) is installed, along with temperature and smoke sensors, to ensure fire safety.

[0058] like Figure 2 As shown, the plasma melting furnace 2 includes a plasma torch system, which includes at least two plasma torches. The two plasma torches are symmetrically installed on the upper side wall of the furnace body at an angle of 15°-30° to the vertical line.

[0059] The plasma melting furnace 2 also includes a furnace shell and refractory lining, a feed inlet, a molten pool and slag outlet, and a syngas outlet. The furnace shell adopts a double-layer steel plate structure, with an inner layer of heat-resistant steel plate and an outer layer of ordinary carbon steel, and the interlayer is filled with insulation material. The refractory lining adopts a composite lining structure, including a hot surface layer, a backing layer, and an insulation layer from the inside out. The feed inlet is located at the top of the furnace body and is connected to the water-cooled jacketed double spiral feeder of the pretreatment and feeding unit 1 through a flange seal. The feed inlet itself is protected by a water-cooled jacket structure. A low-speed rotating water-cooled material distribution plate with guide vanes is set below the feed inlet. Its function is to evenly distribute the falling material to the high-temperature area of ​​the furnace, avoiding material accumulation in the center of the furnace or local overcooling, and ensuring that the material is in full contact with the plasma jet. The slag outlet is located at the lowest point of the furnace bottom and adopts a water-cooled copper sleeve structure.

[0060] The plasma melting furnace 2 is equipped with multiple high-temperature thermocouples inside the furnace body to monitor the temperature in real time; at the same time, the furnace body is equipped with a high-temperature camera observation hole to facilitate direct observation of the flame and molten pool status inside the furnace; a pressure sensor is installed on the top of the furnace chamber.

[0061] The plasma melting furnace 2 provides a reaction environment with ultra-high temperature, strong reducing / neutral atmosphere, and sufficient turbulence for hazardous waste, so as to achieve complete pyrolysis of organic matter and glass stabilization of inorganic matter. The furnace body adopts a vertical cylindrical structure, which can be roughly divided into a gas phase zone, a melting reaction zone, and a molten pool zone from top to bottom.

[0062] The furnace shell of plasma melting furnace 2 adopts a double-layer steel plate structure, with an inner layer of heat-resistant steel plate and an outer layer of ordinary carbon steel. The interlayer is filled with insulation material (ceramic fiber blanket), which reduces heat loss and ensures that the shell temperature is within a safe range.

[0063] The refractory lining of plasma melting furnace 2 adopts a composite lining structure, which includes, from the inside out:

[0064] Hot surface layer: in direct contact with high-temperature molten metal, using high-purity, high-refractory (≥1790℃), and high-slag-erosion-resistant materials such as chrome corundum bricks or fused magnesia bricks.

[0065] Backing layer: Located after the hot surface layer, it mainly serves as insulation. It is made of alumina hollow spherical bricks or lightweight refractory castables to effectively reduce heat loss from the furnace wall and improve thermal efficiency.

[0066] Insulation layer: The outermost layer uses ceramic fiber modules to further enhance the insulation effect.

[0067] The plasma torch system of the plasma melting furnace 2 adopts a multi-torch symmetrical, inclined arrangement. In this embodiment, two plasma torches are installed symmetrically on the upper side wall of the furnace body at an angle of 15°-30° to the vertical. This arrangement has three advantages: first, it can form a high-temperature convergence zone in the center of the furnace, concentrating energy and ensuring uniform temperature; second, it can generate a strong rotating airflow, enhancing the mixing of materials, gases, and plasma jets, and prolonging the residence time of materials in the high-temperature zone; and third, it can provide redundancy backup, allowing the system to operate under reduced load when a single torch requires maintenance.

[0068] This embodiment employs a non-transfer arc plasma torch, which offers stable operation and minimizes electrode wear. The plasma working gas can be selected based on the material characteristics; nitrogen, air, or argon are commonly used. Nitrogen is chosen for chlorine-containing waste to prevent dioxin formation.

[0069] The lower part of the plasma melting furnace 2 is a conical molten pool: used to collect and temporarily store molten inorganic materials (slag). The depth of the molten pool is determined by calculation to ensure that the slag has sufficient residence time, allowing heavy metals and other components to be fully separated and solidified in the glass phase.

[0070] The slag outlet of plasma melting furnace 2 is located at the lowest point of the furnace bottom and adopts a water-cooled copper sleeve structure to withstand the extremely high temperature and the scouring of highly corrosive molten slag. Slag discharge is controlled in conjunction with the furnace operating conditions via a programmable logic controller (PLC).

[0071] The syngas outlet of the plasma melting furnace 2 is located at the top of the furnace body. A Venturi structure or cyclone guide plate is provided at the outlet. By utilizing the change in airflow velocity, the tiny molten droplets entrained in the syngas are captured by centrifugal force and fall back into the molten pool, reducing the dust load of the subsequent system.

[0072] Multiple high-temperature thermocouples or infrared thermometers are installed at key locations on the plasma melting furnace 2 (gas phase zone, above the molten pool) to monitor the temperature in real time. A high-temperature camera observation port is also provided for direct observation of the flame and molten pool status inside the furnace.

[0073] A pressure sensor is installed at the top of the plasma melting furnace 2 to monitor the furnace pressure in real time. A slight negative pressure (-50 to -100 Pa) is maintained inside the furnace by adjusting the frequency of the induced draft fan to ensure that syngas does not leak. An explosion-proof device is provided to address the risk of a sudden increase in furnace pressure under abnormal operating conditions.

[0074] Physicochemical processes inside the plasma melting furnace 2: After the material enters the furnace from the top, it will undergo the following processes:

[0075] Rapid heating and drying: The material is instantly exposed to the high-temperature plasma jet, and the moisture evaporates rapidly.

[0076] Pyrolysis and gasification: Organic matter undergoes decomposition under high temperature and oxygen-deficient / reducing atmosphere to generate syngas (also known as pyrolysis gas), mainly composed of CO, H2, CH4, etc.

[0077] Melting and vitrification: Inorganic materials (metal oxides, silicates, calcium salts, etc.) absorb heat and melt to form a liquid slag, which is then homogenized in the molten pool. Under high temperature and specific composition (by adding fluxes such as quartz sand to adjust the basicity), heavy metal ions are encapsulated in the SiO2 network structure, forming a stable glass.

[0078] Metal reduction and collection: Some high-valence metal oxides (such as Fe2O3) may be reduced to elemental or low-valence oxides. Denser elemental metals (such as Fe and Cu) will settle to the bottom of the molten pool to form an alloy phase, which can be discharged in layers with the slag, thus realizing the recovery of valuable metals.

[0079] The operation of the melting reaction zone in plasma melting furnace 2 adopts multi-parameter collaborative intelligent control:

[0080] Temperature control: The temperature of the melting reaction zone (target: 1400℃-1600℃) is the main controlled variable, which is achieved by adjusting the power of the plasma torch and the feed rate (from feedback from the pretreatment and feeding unit 1).

[0081] Atmosphere control: By controlling the plasma working gas flow rate and furnace pressure, a stable reducing atmosphere is maintained in the furnace, ensuring that heavy metals exist in a stable form in the slag and inhibiting the formation of dioxins.

[0082] Slag fluidity control: By monitoring the properties of slag online or predicting the composition of materials, fluxing agents (such as limestone and quartz sand) are intelligently added to adjust the viscosity and melting point of the slag, ensuring its fluidity and facilitating smooth slag discharge.

[0083] The quench tower 3 is equipped with an atomizing spray system, which can cool high-temperature synthesis gas at ≥800℃ to below 200℃ within 1 second.

[0084] The waste heat recovery and purification unit 4 includes, in sequence, a waste heat boiler, a bag filter, an acid gas scrubbing tower, and a flue gas reheating and emission system. The top of the acid gas scrubbing tower is equipped with a high-efficiency demister, and the flue gas reheating and emission system includes a reheater, an induced draft fan, and a chimney.

[0085] Waste heat recovery and purification unit 4 safely and efficiently recovers the sensible heat from the medium-temperature syngas from quench tower 3 and performs deep purification to ensure that the gas finally emitted into the atmosphere fully complies with stringent environmental standards. This unit follows the process logic of "recovering energy first, then deep purification". The waste heat boiler is the energy recovery core of waste heat recovery and purification unit 4. Its primary task is to convert the large amount of medium-temperature sensible heat (approximately 200℃-500℃) still carried in the quenched syngas into usable steam or hot water, significantly improving the energy utilization efficiency of the entire system and reducing operating costs. At the same time, the cooling effect of the boiler also creates the necessary conditions for the safe and efficient operation of the subsequent bag filter (the temperature drops below the filter bag's tolerance range).

[0086] Considering the potential dust and corrosive components in syngas, a flue-type (fire-tube) boiler is selected in this embodiment. Syngas flows through the boiler tubes, while softened water is heated and evaporated outside the tubes. This structure offers strong impact resistance, convenient ash removal, and effectively addresses the abrasion and adhesion of dust in the syngas.

[0087] In areas with low-temperature corrosion risk (such as economizers), use sulfuric acid dew point corrosion resistant steels such as ND steel (09CrCuSb).

[0088] Temperature control: By precisely controlling the boiler feedwater temperature and flue gas temperature, the boiler heating surface wall temperature is ensured to always be higher than the acid dew point of the flue gas, fundamentally preventing corrosion caused by the condensation of sulfuric acid, nitric acid, etc.

[0089] Ash removal mechanism: The boiler heating surface is equipped with shock wave soot blowers and / or sonic soot blowers, which work automatically at regular intervals to effectively remove accumulated ash, maintain the cleanliness of the heating surface, and ensure heat transfer efficiency.

[0090] The steam generated by the waste heat boiler (pressure designed according to demand, such as 0.8MPa-1.6MPa) can be used to drive steam turbines to generate electricity, or as a heat source for heating in the plant area and production processes, realizing the cascade utilization of energy.

[0091] The waste heat recovery and purification unit is a dry acid removal and dust removal system that integrates a reactor and a bag filter.

[0092] Syngas (temperature approximately 180℃-220℃) from the waste heat boiler first enters the reactor. Here, alkaline powders such as slaked lime (Ca(OH)2) or baking soda (NaHCO3) are evenly sprayed into the flue gas duct through a high-efficiency dry powder injection device. The alkaline powder reacts chemically with acidic gases (such as SO2, HCl, HF) in the flue gas to produce solid salts. The gas flow carrying the reaction products, unreacted reagents, and most of the dust then enters the low-pressure pulse bag filter.

[0093] Filter bag selection for baghouse dust collectors: PTFE membrane filter media (P84+PTFE membrane) is selected. This filter media has extremely high filtration accuracy (emission concentration <5mg / Nm³), excellent temperature resistance, and chemical corrosion resistance. The PTFE microporous membrane on the surface achieves "surface filtration," making it difficult for dust to enter the interior of the filter media, resulting in excellent dust removal and low operating resistance. When the system starts up or treats low-dust flue gas, a pre-coating device is installed to pre-form an alkaline dust layer on the surface of the filter bag, protecting it from direct damage by high temperatures or sticky, corrosive substances. Unreacted alkaline powder is captured on the surface of the filter bag, forming a "filter cake." When the flue gas passes through the filter bag, it can continue to react with the acidic gases within, achieving secondary acid removal, improving acid removal efficiency, and reducing reagent consumption.

[0094] As a "fine treatment" unit for flue gas purification, the acid gas scrubbing tower is responsible for the deep removal of acid gases remaining after dry treatment, as well as the efficient removal of water-soluble heavy metals (such as mercury vapor) and any potentially present extremely fine particulate matter (PM2.5).

[0095] In this embodiment, the acid gas scrubbing tower is a packed tower to provide a large gas-liquid contact area. The tower is configured with two or three stages of scrubbing in series:

[0096] First stage (rapid cooling / circulating alkaline washing): NaOH or Ca(OH)2 solution is used as the washing liquid, which is sprayed through a circulating pump and comes into countercurrent contact with the flue gas to completely remove most of the acidic gases such as HCl and SO2.

[0097] Second stage (deep purification): As needed, complexing agents such as sodium thiosulfate are added, specifically for the removal of zero-valent mercury (Hg). 0 This converts it into divalent mercury, which is then absorbed by the washing liquid.

[0098] A high-efficiency demister (baffle plate type or wire mesh type) is installed at the top of the acid gas scrubbing tower to capture mist droplets entrained in the flue gas, ensuring that the moisture content of the flue gas meets the standard and avoiding "white smoke" phenomenon and corrosion of the subsequent chimney.

[0099] A reheater is installed in the flue gas reheating and emission system: After wet scrubbing, the temperature of the flue gas has dropped to its saturation temperature (approximately 50℃-60℃). Direct emission would result in dense "white smoke" (water vapor condensation) at the chimney outlet and would hinder flue gas elevation and diffusion. Therefore, a flue gas reheater (steam heating, gas heating, or heat pipe heat exchange type) is installed to raise the flue gas temperature to above 80℃ before emission through the chimney. This eliminates "white smoke," increases the flue gas elevation, and further reduces the concentration of pollutants at ground level.

[0100] The flue gas reheating and emission system includes an induced draft fan and a chimney: the variable frequency induced draft fan is located at the end of the entire purification system, providing power for the airflow and maintaining a slight negative pressure state throughout the process from the plasma melting furnace to this unit. An online continuous emission monitoring system (CEMS) is installed on the chimney to monitor the concentrations of pollutants such as dust, SO2, NOx, and HCl in real time, ensuring compliance with emission standards. The data is directly transmitted to the environmental protection department.

[0101] The slag treatment unit 5 includes a water quenching tank, which directly receives the high-temperature molten slag discharged from the bottom of the plasma melting furnace 2, and is used to rapidly cool the molten slag to form glassy particles with stable chemical properties, high glass content, and extremely low leaching toxicity of heavy metals.

[0102] The water quenching tank is a high-temperature, impact-resistant, and corrosion-resistant reinforced concrete structure, lined with anti-corrosion and wear-resistant materials (granite cast stone slabs or high-performance polymer lining). The tank volume must ensure sufficient water to guarantee that the molten slag can be instantly cooled while keeping the water temperature within a controllable range. High-temperature molten slag (approximately 1400-1600℃) falls into the water quenching tank filled with cooling water through the slag outlet at the bottom of the plasma melting furnace 2 in a continuous or intermittent thin stream. The high-temperature molten slag comes into intense contact with the room-temperature cooling water, resulting in a quenching effect. The enormous thermal stress causes the molten slag to instantly shatter into fine particles. The extremely rapid cooling rate inhibits crystal formation and growth, forcing the melt structure to become disordered, thus forming an amorphous structure dominated by glass. This glassy network structure can effectively encapsulate, dissolve, and adsorb heavy metal ions (such as Pb, Cd, Cr, Zn, etc.) within it, as if "imprisoned" in glass, making it difficult for them to leach out under natural conditions, achieving highly efficient chemical stabilization.

[0103] The water quenching tank is equipped with high-pressure water jet nozzles near the molten slag impact point. The impact force of the water flow further breaks up and disperses the molten slag stream, promoting its granulation and forming uniform particles. The tank is equipped with a level gauge and a temperature sensor, which are linked with the automatic water replenishment system and the cooling system to ensure stable water level and temperature (usually controlled at <60℃), guaranteeing rapid cooling effect and system safety.

[0104] The glassy particles formed after water quenching settle at the bottom of the quenching tank. They are then removed from the water using a chain-plate slag remover. This equipment naturally drains most of the water during the conveying process.

[0105] The initially dehydrated granules are conveyed to a vibrating dewatering screen for further dewatering. Through mechanical vibration or rotation, surface moisture is further removed from the granules, reducing the product's moisture content to below 15%, facilitating subsequent transportation, storage, and utilization. The dehydrated and dried granules are then transferred to the product stockpile or storage silo via belt conveyor. All conveying processes are enclosed to prevent dust escape and material spillage.

[0106] The cooling water overflowing from the water quenching tank and the wastewater generated during the dehydration process are collected in a circulating water pool through ditches.

[0107] The circulating water tank is equipped with an inclined tube sedimentation tank to remove fine suspended particles carried in the water.

[0108] The circulating water tank is equipped with a pH adjustment device: Since the slag may be alkaline, acid (such as dilute sulfuric acid) needs to be added to adjust the pH value of the circulating water to the neutral (6-9) range to prevent equipment corrosion and scaling.

[0109] A cooling tower is installed after the circulating water pool: it reduces the temperature of the circulating water to the design value and reuses it in the water quenching tank, realizing a closed-loop circulation of water resources.

[0110] The large amount of steam generated during water quenching may carry trace amounts of volatile substances. A gas collection hood is installed above the water quenching tank to guide the steam to the condenser. The condensed non-condensable gases are then fed into the purification unit of the main process flow for treatment, ensuring that fugitive emissions are effectively controlled.

[0111] The present invention employs the following method for the harmless treatment of hazardous waste using the aforementioned system: Hazardous waste (such as pharmaceutical waste, waste organic solvents, etc.) is crushed and homogenized in pretreatment unit 1, and then continuously and stably fed into plasma melting furnace 2 by a water-cooled screw feeder. Two plasma torches are symmetrically arranged on the upper part of the furnace body, generating a high-temperature plasma arc. The plasma torches are activated, generating a high-temperature plasma jet to maintain the temperature of the reaction zone inside the furnace at 1200℃-1600℃. At high temperatures, the hazardous waste undergoes cracking, gasification, and melting reactions. Organic matter is converted into syngas, mainly composed of CO and H2, while inorganic matter forms a glassy slag. The syngas rises and exits from the top outlet, entering quench tower 3. Inside quench tower 3, the syngas is cooled to 180℃ within 0.5 seconds by atomized cooling water. The cooled gas enters a waste heat boiler to generate saturated steam at 0.8MPa, and then undergoes deep purification through a bag filter and an acidic gas scrubbing tower sprayed with alkaline solution before being discharged in compliance with standards. The slag at the bottom of the melting furnace is periodically discharged from the discharge port and enters the water quenching tank. After water quenching and cooling, it forms dense glassy particles with stable chemical properties and heavy metal leaching toxicity far below the standard. These particles are then safely landfilled or used as building material additives for resource utilization. Tests show that the leaching concentrations of heavy metals Pb, Cd, and Cr are far below the limits of the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification".

Claims

1. A high-temperature plasma-based hazardous waste detoxification system, characterized by, The application relates to a hazardous waste treatment system, which comprises the following parts: a pretreatment and feeding unit (1) for preparing and feeding materials; a plasma melting furnace (2) connected with the pretreatment and feeding unit (1) and used for cracking, gasifying and melting hazardous waste under a high-temperature plasma environment; a quenching tower (3) connected with a synthesis gas outlet of the plasma melting furnace (2) and used for rapidly cooling high-temperature synthesis gas; a waste heat recovery and purification unit (4) connected with the quenching tower (3) and used for recovering waste heat and deeply purifying pollutants of the cooled synthesis gas; a molten slag treatment unit (5) connected with a molten slag discharge port of the plasma melting furnace (2) and used for water quenching and resource treatment of generated molten slag.

2. The high temperature plasma based hazardous waste detoxification system as claimed in claim 1, wherein: The pretreatment and feeding unit (1) comprises a storage subsystem, a pretreatment subsystem and a feeding subsystem, the storage subsystem comprises a receiving and temporary storage warehouse and a hazardous waste characteristic analysis and matching area, the pretreatment subsystem comprises a coarse crushing and fine crushing module and a homogenization and matching module, and the feeding subsystem comprises a water-cooled jacketed double-screw feeder and a metering and control system.

3. The high temperature plasma based hazardous waste detoxification system as claimed in claim 1 wherein: The plasma melting furnace (2) comprises a plasma torch system, the plasma torch system comprises at least two plasma torches, and the two plasma torches are symmetrically arranged on the upper sidewall of a furnace body at an angle of 15-30 degrees with respect to a vertical line.

4. The high temperature plasma based hazardous waste detoxification system as claimed in claim 3, wherein: The plasma melting furnace (2) further comprises a furnace shell and a refractory lining, a feeding port, a molten pool and a slag discharge port and a synthesis gas outlet, the furnace shell adopts a double-layer steel plate structure, the inner layer is a heat-resistant steel plate, the outer layer is a common carbon steel, and a heat preservation material is filled in the interlayer, the refractory lining adopts a composite lining structure and comprises, from inside to outside, a hot face layer, a backing layer and a heat preservation layer, the feeding port is located at the upper portion of the furnace body and is sealingly connected with the water-cooled jacketed double-screw feeder of the pretreatment and feeding unit (1) through a flange, the slag discharge port is located at the lowest point of the furnace bottom and adopts a water-cooled copper sleeve structure, and the synthesis gas outlet is located at the top of the furnace body.

5. A high temperature plasma based hazardous waste detoxification system as claimed in claim 4, wherein: A plurality of high-temperature thermocouples are arranged in the furnace body of the plasma melting furnace (2) to monitor the temperature in real time, a high-temperature camera observation hole is arranged on the furnace body to facilitate direct observation of the flame and molten pool state in the furnace, and a pressure sensor is arranged on the top of the furnace chamber.

6. A high temperature plasma based hazardous waste detoxification system as claimed in claim 1, wherein: The quenching tower (3) is provided with a atomizing spraying system and can cool the high-temperature synthesis gas with a temperature higher than or equal to 800 DEG C to below 200 DEG C within 1 second.

7. A high temperature plasma based hazardous waste detoxification system as claimed in claim 1, wherein: The waste heat recovery and purification unit (4) comprises, in sequence, a waste heat boiler, a bag-type dust collector, an acid gas washing tower and a flue gas reheating and discharging system, the acid gas washing tower is provided with a high-efficiency demister at the top, and the flue gas reheating and discharging system comprises a reheater, an induced draft fan and a chimney.

8. The high temperature plasma based hazardous waste detoxification system of claim 1, wherein: The molten slag treatment unit (5) comprises a water quenching tank for rapidly cooling molten slag into glassy particles, the water quenching tank is provided with a high-pressure water flow nozzle above a molten slag falling point, and a gas collecting hood is arranged above the water quenching tank.

9. A method for treating hazardous waste by using the system according to any one of claims 1 to 8, wherein The application further discloses a hazardous waste treatment method, which comprises the following steps: S1: pretreating hazardous waste and continuously feeding the hazardous waste into a plasma melting furnace through a feeding unit; S2: in the plasma melting furnace, the high temperature generated by the plasma torch makes the hazardous waste to have cracking, gasification and melting reaction, and generates synthesis gas and glassy slag; S3: the high temperature synthesis gas generated in step S2 is introduced into the quench tower for rapid cooling; S4: the cooled synthesis gas is subjected to waste heat recovery, dust removal and acid gas removal; S5: the molten slag generated in step S2 is water quenched to form stable glassy particles.

10. The hazardous waste detoxification method according to claim 9, characterized by, In step S2, the reaction temperature in the plasma melting furnace is controlled at 1200-1600℃; in step S3, the process of rapid cooling cools the synthesis gas from ≥800℃ to below 200℃ within 1 second.

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