Organic waste salt plasma melting-fractionated condensation resource disposal method and device

Abstract

The application discloses a kind of organic waste salt plasma melting-grade condensation resource disposal method and device, it is related to hazardous waste resource technology field.The method includes: organic waste salt is dried and mixed with coal powder, is sent into plasma melting furnace by micro-negative pressure closed feed, realizes complete cracking of organic matter and chlorate gasification separation under 1300~1400 ℃ weak reducing atmosphere, high-temperature flue gas is cooled after dust removal and is recovered by two-stage gradient condensation purification industrial chlorate, tail gas is discharged after multistage purification, and the melt slag is vitrified and solidified and is disposed as general solid waste.The organic matter cracking rate is greater than or equal to 99.99%, the industrial salt recovery rate is greater than or equal to 80%, the product salt TOC is less than 30mg / kg, the problems of low salt recovery rate, serious high-chlorine corrosion and easy production of dioxin in prior art are solved, closed-loop resource disposal of organic waste salt can be realized, and it is suitable for in-situ or large-scale centralized disposal of HW49, HW12 type industrial organic waste salt.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste harmless and resource-based disposal technology, specifically to a method and apparatus for the plasma high-temperature melting pyrolysis and graded condensation recovery disposal of industrial organic waste salt. Background Technology

[0002] Industrial organic waste salts mainly originate from the evaporation process of high-salt wastewater in industries such as fine chemicals, pharmaceutical intermediates, and electronic chemicals. The main components are chloride salts such as sodium chloride and potassium chloride, with a dry basis percentage of over 80%. They also contain phenols, organic solvents, and other recalcitrant organic matter, as well as small amounts of inert impurities such as silicon, aluminum, and calcium, and trace amounts of heavy metals. Most of them are classified as HW49 or HW12 hazardous wastes in the National Hazardous Waste List.

[0003] Currently, the mainstream disposal method for organic waste salt in China is rigid landfill across provinces, which has three major problems: First, the disposal cost is high, with comprehensive transportation and landfill costs generally exceeding 3,000 yuan / ton, and prices continue to rise, placing a heavy burden on enterprise operations; Second, the compliance risk is high, with long approval cycles for inter-provincial transfer manifests, high environmental risks during transportation, and fluctuations in transfer directly affecting the continuity of enterprise production under the normalization of environmental supervision; Third, there is serious resource waste, with a large amount of recyclable chloride salt in the waste salt being directly landfilled, completely losing its resource value, which does not meet the requirements for the construction of "zero-waste cities".

[0004] Among the existing resource utilization technologies, the water washing oxidation process has the drawbacks of large secondary wastewater volume and incomplete removal of organic matter; the traditional high-temperature incineration process is prone to salt melting and coking, severe equipment corrosion, salt recovery rate is generally less than 50%, and it is easy to generate dioxin-like pollutants; low-temperature plasma technology can only decompose surface organic matter and cannot achieve deep separation of salt and impurities, making it difficult for the product salt quality to meet industrial reuse standards.

[0005] In summary, the industry currently lacks a technology for the resource-based treatment of organic waste salt that can completely decompose organic matter, achieve high salt recovery rates, have corrosion-resistant equipment, produce no secondary pollution, and can be operated stably on a large scale. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for the resource-based treatment of organic waste salt by plasma melting and graded condensation. The method achieves complete pyrolysis of organic matter and separation of chloride salts by high-temperature plasma, and combines two-stage gradient condensation to purify and recover industrial salt. At the same time, it achieves vitrification and solidification of molten slag. The entire process is carried out under closed negative pressure, which solves the problems of incomplete removal of organic matter, low salt recovery rate, severe high chlorine corrosion, and secondary pollution in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for the resource-based treatment of organic waste salts by plasma melting and staged condensation includes the following steps: Pretreatment: Dry the organic waste salt to a moisture content of ≤2%, and mix it evenly with 2%~4% of anthracite powder by dry weight to obtain a dry-based mixture; Closed feeding: The dry-based mixture is continuously fed into the plasma melting furnace under a micro negative pressure of -50~-100Pa through a multi-stage airlock sealing structure; Plasma melting and pyrolysis: In a high-temperature plasma field of 1300~1400℃, a weak reducing atmosphere of CO volume concentration of 0.5%~3% is maintained to completely degrade recalcitrant organic matter, completely vaporize chloride salts into the gas phase, and form glassy slag with inert impurities and heavy metals. High-temperature dust removal and rapid cooling: After the high-temperature flue gas passes through a high-temperature cyclone separator to remove molten slag droplets, it is rapidly cooled to below 200°C within 1 second; Two-stage gradient condensation recovery: flue gas sequentially enters a medium-temperature condensation section of 500~700℃ and a low-temperature condensation section of 200~400℃, where impurity enrichment and purified industrial chloride salts are collected respectively; Exhaust gas deep purification: The flue gas is discharged in compliance with standards after being adsorbed by activated carbon, filtered by bag filter, and washed by two-stage acid and alkali. Harmless discharge of molten slag: The glassy molten slag is discharged after water quenching and is treated as general industrial solid waste.

[0008] Furthermore, the plasma melting adopts a DC arc plasma torch with a single unit power of 300~400kW, and the furnace lining of the melting furnace adopts a silicon carbide-chromium oxide composite corrosion-resistant and refractory material.

[0009] Furthermore, the dry basis recovery rate of the recovered industrial chloride salt is ≥80%, and the TOC content of the product salt is <30mg / kg, which meets the secondary standard of industrial dry salt and can be reused in production or sold externally.

[0010] Furthermore, the exhaust emissions comply with the "Standard for Pollution Control of Hazardous Waste Incineration", with a dioxin emission concentration of <0.1ngTEQ / m³.

[0011] The present invention also provides a treatment device for implementing the above method, which includes, in sequence along the material and flue gas flow direction, a pretreatment unit, a closed feeding unit, a plasma melting unit, a dust removal and rapid cooling unit, a staged condensation unit, an exhaust gas purification unit, and a central control and online monitoring unit.

[0012] Furthermore, the inner wall of the staged condenser unit is made of Hastelloy or enamel corrosion-resistant material, and is equipped with an anti-scaling pulse purging structure.

[0013] Furthermore, the plasma melting unit maintains a slight negative pressure throughout the process, and is equipped with an over-temperature and over-pressure interlock protection and emergency shutdown system.

[0014] The present invention has the following beneficial effects: High degree of resource utilization: Chloride salt recovery rate ≥80%, product salt quality meets industrial reuse standards, realizing the transformation of hazardous waste into resource products, with significant economic and environmental benefits; Thoroughly harmless: The organic matter decomposition rate is ≥99.99% at a high temperature of 1300~1400℃, heavy metals are solidified in glassy slag, and the dioxin emission in the tail gas is far below the national standard; Strong corrosion resistance: Targeted use of composite refractory and anti-corrosion materials, suitable for high chlorine flue gas conditions, resulting in long service life and stable operation of the equipment; No secondary pollution: The entire process is under closed negative pressure, with no dust leakage. Washing wastewater can be connected to the company's existing sewage treatment plant, with no new wastewater discharge. It is applicable to a variety of scenarios: it can be used to build large-scale centralized treatment lines or to adopt the "plant-in-plant" model to support enterprises to carry out on-site treatment without the need for cross-provincial transfer, and it has strong compliance. Attached Figure Description

[0015] Figure 1 is a flowchart of the overall process flow of the treatment method of the present invention; Figure 2 is a schematic diagram of the plasma melting unit structure of the treatment device of the present invention.

[0016] Explanation of markings in the diagram: 1 - Pretreatment unit, 2 - Sealed feeding unit, 3 - Plasma melting unit, 4 - Dust removal and quenching unit, 5 - Medium-temperature condensation section, 6 - Low-temperature condensation section, 7 - Tail gas purification unit, 8 - Slag water quenching unit; 31 - Vertical melting furnace body, 32 - DC arc plasma torch, 33 - Water cooling jacket, 34 - Feed inlet, 35 - Flue gas outlet, 36 - Water quenching slag discharge port. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments.

[0018] Example 1 This example is a 3-ton / day plant-within-a-plant organic waste salt treatment line. The treatment object is the evaporation residue waste salt generated by the alkylphenol production line of a fine chemical enterprise. The dry basis composition is: sodium chloride 82%, organic matter TOC 6%, inert impurities 9%, trace heavy metals, which belongs to HW12 hazardous waste.

[0019] The specific handling steps are as follows: Pretreatment: Waste salt is dried with hot air to a moisture content of 1.8%, and after being weighed by a loss-in-weight scale, it is mixed evenly with 200-mesh anthracite powder accounting for 3% of the dry weight in a premixer to obtain a dry-based mixture. Closed feeding: The mixture is continuously fed into the vertical melting furnace through a three-stage airlock sealed feeder under a slight negative pressure of -80Pa, with no smoke or salt dust leakage throughout the process; Plasma melting and pyrolysis: A single 350kW DC arc plasma torch is used for heating, the molten pool temperature is controlled at 1350℃, and a weak reducing atmosphere with a CO volume concentration of 1.5% is maintained in the furnace; phenols and other recalcitrant organic compounds in the waste salt are completely pyrolyzed into small molecule gases, with a pyrolysis rate of 99.995%; sodium chloride is completely vaporized and enters the gas phase; inert impurities and heavy metals melt to form glassy slag; High-temperature dust removal and rapid cooling: The outlet flue gas passes through a silicon carbide-lined high-temperature cyclone separator to remove molten slag droplets, and then enters the rapid cooling section, where it is rapidly cooled to 180°C within 0.8 seconds to avoid the temperature range of dioxin resynthesis. Two-stage gradient condensation: flue gas enters the medium-temperature condensation section (controlled temperature 600℃) and the low-temperature condensation section (controlled temperature 300℃) in sequence; the medium-temperature section collects high-boiling-point impurities and enriches them, while the low-temperature section collects and purifies industrial salt. Exhaust gas purification: The flue gas passes through activated carbon injection adsorption, pulse bag dust removal, and two-stage acid and alkali washing in sequence, and is finally discharged through a 15-meter exhaust stack; Slag discharge: The glassy slag is continuously discharged into a water quenching tank for cooling, and periodically discharged for external transportation and disposal in building materials.

[0020] The test results of this embodiment are as follows: the dry basis recovery rate of industrial salt is 83%, the TOC content of the product salt is 22mg / kg, which meets the secondary standard of industrial dry salt; the heavy metal leaching concentration of the slag meets the standard and is not classified as hazardous waste; the dioxin emission concentration of the tail gas is 0.03ng TEQ / m³, which is far below the national standard.

[0021] Example 2 This example is a centralized treatment line with a scale of 20 tons / day. The treatment object is mixed organic waste salt generated by multiple fine chemical and pharmaceutical companies in the park. The total chloride content on a dry basis is 80%~85%, the TOC content is 5%~8%, and it belongs to HW49 hazardous waste.

[0022] The device is equipped with four 350kW DC arc plasma torches, three in use and one on standby, and adopts a DCS automated control system. The remaining process principles are the same as in Example 1.

[0023] Operating parameters: melting temperature 1320~1380℃, weak reducing atmosphere CO concentration 0.8%~2.5%, medium temperature condensation section 550~650℃, low temperature condensation section 250~350℃.

[0024] Operating results: average salt recovery rate 81%, product salt TOC < 30 mg / kg, organic matter decomposition rate ≥ 99.99%, system continuous stable operation time exceeds 8000 hours / year, and all environmental protection indicators meet the standards.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the resource-based treatment of organic waste salts using plasma melting and staged condensation, characterized in that, Includes the following steps: Pretreatment: The organic waste salt is dried to a moisture content of ≤2%, and then uniformly mixed with anthracite powder accounting for 2%~4% of the dry basis mass to obtain a dry basis mixture; the organic waste salt is HW49 or HW12 type hazardous waste, with a total chloride salt content of ≥80% and a total organic matter (TOC) content of 5%~8% in the dry basis. Sealed feeding: The dry-based mixture is continuously fed into the plasma melting furnace under a micro negative pressure of -50~-100Pa through a multi-stage airlock sealing structure, with no dust or flue gas leakage throughout the process; Plasma melting and pyrolysis: In a high-temperature plasma field of 1300~1400℃, a weak reducing atmosphere with a CO volume concentration of 0.5%~3% is maintained to completely pyrolyze the recalcitrant organic matter in the waste salt, with a pyrolysis rate of ≥99.99%; chloride salts are completely vaporized by heating and enter the gas phase; inert impurities and heavy metals melt to form glassy slag, and heavy metals are solidified by the crystal lattice. High-temperature dust removal and rapid cooling: The high-temperature flue gas at the outlet of the melting furnace first passes through a high-temperature cyclone separator to remove entrained molten slag droplets, and then is rapidly cooled to below 200°C within 1 second to inhibit the resynthesis of dioxin-like substances; Two-stage gradient condensation recovery: The flue gas after rapid cooling enters the medium-temperature condensation section and the low-temperature condensation section in sequence; the temperature of the medium-temperature condensation section is controlled at 500~700℃ to collect high-boiling-point impurities; the temperature of the low-temperature condensation section is controlled at 200~400℃ to condense, collect and purify industrial chloride salts. Deep purification of exhaust gas: After condensation, the flue gas is successively treated by activated carbon adsorption, bag filter dust removal and two-stage acid and alkali washing, and then discharged through the exhaust stack in compliance with standards. Harmless discharge of molten slag: The glassy molten slag is discharged after water quenching and cooling. The heavy metal leaching concentration meets the requirements of GB 5085.3-2007 standard and is disposed of as general industrial solid waste.

2. The method for resource recovery and disposal of organic waste salts via plasma melting-stage condensation according to claim 1, characterized in that, In step 3), a DC electric arc plasma torch is used to provide the heat source, with a single unit power of 300~400kW; the furnace lining of the melting furnace is made of silicon carbide-chromium oxide composite corrosion-resistant and refractory material, which is suitable for high chlorine flue gas corrosion conditions.

3. The method for resource recovery and disposal of organic waste salts via plasma melting-stage condensation according to claim 1, characterized in that, In step 5), the dry basis recovery rate of industrial chloride salt is ≥80%, and the TOC content of the recovered product salt is <30mg / kg, which meets the secondary standard of GB / T 5462-2015 for industrial dry salt.

4. The method for resource recovery and disposal of organic waste salts via plasma melting-stage condensation according to claim 1, characterized in that, In step 6), the exhaust emissions comply with GB 18484-2020 "Standard for Pollution Control of Hazardous Waste Incineration", and the dioxin emission concentration is <0.1ng TEQ / m³.

5. An organic waste salt plasma melting-stage condensation resource recovery treatment device for implementing the method of any one of claims 1 to 4, characterized in that, Along the material and flue gas flow direction, the system includes: a pretreatment unit, comprising a hot air dryer, a loss-in-weight weighing scale, and a carbon powder premixer, used for drying waste salt and mixing materials; a closed feeding unit, comprising a multi-stage airtight feeder and a micro-negative pressure control system, used for continuous closed feeding; a plasma melting unit, comprising a vertical melting furnace, a DC arc plasma torch, a closed water cooling system, and a water quenching slag discharge device; a dust removal and quenching unit, comprising a high-temperature cyclone separator and a flue gas quencher; a staged condensation unit, comprising a medium-temperature condenser, a low-temperature condenser, and an industrial salt collection silo; a tail gas purification unit, comprising an activated carbon injection device, a pulse bag filter, a two-stage acid-base scrubbing tower, an induced draft fan, and an exhaust stack; and a central control and online monitoring unit, comprising a PLC control system, an online monitoring module for non-methane total hydrocarbons, an online monitoring module for hydrogen chloride, and an online monitoring module for heavy metals.

6. The organic waste salt plasma melting-stage condensation resource recovery treatment device according to claim 5, characterized in that, The inner wall of the staged condensation unit is made of Hastelloy or enamel corrosion-resistant material, and is equipped with an anti-scaling pulse purging structure.

7. The organic waste salt plasma melting-stage condensation resource recovery treatment device according to claim 5, characterized in that, The plasma melting unit maintains a slight negative pressure throughout the process and is equipped with an over-temperature and over-pressure interlock protection and emergency shutdown system.

Images