A method for detoxification of waste salt by oxidation melting and short-process purification of flue gas

Abstract

The application discloses a method for waste salt oxidation melting detoxification and flue gas short process purification, which is characterized by the following steps: mixing medical waste salt and combustion-supporting agent, placing the mixture in a high-temperature melting oxidation furnace, and introducing combustion-supporting gas; pollutants in the waste salt are oxidized and decomposed under the condition of high temperature and oxygen; flue gas generated in the melting oxidation process is collected and circulated into the melting waste salt in the high-temperature melting oxidation furnace, so that volatile components in the waste salt are oxidized and decomposed under the condition of high temperature and oxygen, and the melting detoxification of multiple pollutants in the waste salt is realized; active free radicals are generated by corona discharge of the subsequent flue gas, dust in the flue gas is removed by electric filtration and catalytic oxidation, residual VOCs and dioxin organic pollutants are further degraded, and part of the acidic gas is oxidized; the flue gas containing NOx, SOx and part of the acidic gas is sprayed with lye, a crystal-promoting agent is added into the spraying liquid, and directional crystallization of sulfate and nitrate is realized; the application realizes source-head blockage-process control-sulfur and nitrogen resource utilization of gaseous pollutants in the high-temperature melting oxidation process of the waste salt, and promotes clean treatment of the waste salt.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of flue gas purification, and particularly relates to a method for waste salt oxidation melting detoxification and flue gas short process purification. BACKGROUND

[0002] The treatment and disposal of waste salt mainly includes salt washing method, extraction method, landfill method, sea filling method and high temperature treatment method. The high temperature melting treatment method is a feasible and efficient waste salt treatment technology, which has remarkable effect on the removal of organic matter and strong universality. However, complex, high-toxicity and difficult-to-treat flue gas is generated in the process of melting oxidation.

[0003] At present, there are many application cases of flue gas treatment process engineering, but there are still limitations for short process purification of various organic and inorganic gaseous pollutants, and for the difficulties brought by the current multi-scale gaseous pollutant purification to industrial development, the research focus of the existing efficient control technology of multi-scale gaseous pollutants should be placed not only on the purification of complex flue gas, but also on the research of pollutant source blocking and the research of multi-pollutant micro-interface multi-effect control mechanism, and the sulfur and nitrogen resources in the characteristic flue gas pollutants should be made into mixed salt with certain value. SUMMARY

[0004] The application provides a method for waste salt oxidation melting detoxification and flue gas short process purification, which comprises the following steps: mixing medical waste salt and combustion-supporting agent, and placing the mixture in a high-temperature melting oxidation furnace; introducing combustion-supporting gas; oxidizing and decomposing the pollutants in the waste salt under the condition of high temperature and oxygen; collecting the flue gas generated in the melting oxidation process, and circulating the flue gas into the molten waste salt in the high-temperature melting oxidation furnace for secondary combustion, so that the volatile organic components in the waste salt are oxidized and decomposed under the condition of high temperature and oxygen, and the multi-pollutant melting detoxification of the waste salt is realized; generating high-activity free radicals by corona discharge on the subsequent flue gas, removing the dust in the flue gas by electric filtration, and removing the remaining VOCs and dioxin organic pollutants, oxidizing part of the acid gas by catalytic oxidation; spraying alkali liquor on the flue gas containing NOx, SOx and part of the acid gas, adding a crystal-promoting agent in the spraying liquid, and realizing directional crystallization of sulfate and nitrate; and the method can realize the source blocking-process control-sulfur and nitrogen resource utilization of gaseous pollutants in the high-temperature melting oxidation process of waste salt.

[0005] The high-temperature melting oxidation furnace comprises a shell, a feeding port and a gas outlet I are arranged at the top of the shell, a molten salt outlet I and a molten salt outlet II are opened at the bottom of the shell, the shell is divided into three chambers by two flue gas collecting covers, the chamber between the two flue gas collecting covers is communicated with the bottom of the shell through a pipeline and a Venturi tube, a combustion-supporting gas inlet and a gas pump are arranged on the pipeline, the third chamber from top to bottom is communicated with the bottom of the shell through a pipeline and a Venturi tube, and the flue gas collecting cover is in a hollow inverted circular table shape.

[0006] The temperature inside the high-temperature melting oxidation furnace is 200℃~1300℃, and the water content of the waste salt is 30%~90%; the combustion aid is one or more of potassium chlorate, potassium nitrate, manganese dioxide, magnesium oxide, aluminum oxide, iron tetroxide, iron oxide, and ferric chloride.

[0007] The device for subsequent flue gas treatment is an electrostatic filtration and plasma catalytic oxidation unit, which includes a shell, a cylindrical filter cloth at the center of the shell, a cylindrical catalyst packing element fitted on the outside of the filter cloth, two or more corona electrodes on the outside of the catalyst packing element, and a corona electrode at the center of the cylindrical filter cloth. The outlet I of the high-temperature melting oxidation furnace is connected to the inlet I at the top of the shell through a pipe, and the outlet II is provided at the bottom of the shell.

[0008] The filter cloth is either an electrofiltration cloth or a metal filter cloth, and the filter cloth material is one of aluminum alloy, glass fiber, polytetrafluoroethylene, carbon fiber, silicon carbide, molybdenum metal, carbon fiber, stainless steel, nickel-chromium alloy, iron-chromium-aluminum alloy, zirconium oxide, and molybdenum disilicide; the catalyst in the catalyst packing is a conventional catalyst loaded with one or more transition metals (Co, Fe, Rh, Pd, Ni, Au) for electrochemical catalytic oxidation.

[0009] The electrode material is one of the following: electroplated IrO3, graphite, stainless steel, Ti / IrO3, Ti, Fe / Mn / Pd stainless steel, and BBD; the power supply connected to the electrode is a DC high-voltage power supply with a discharge voltage range of 5 kV to 25 kV.

[0010] Alkali spraying is carried out in the flue gas spraying crystallization unit, which includes a shell, a stirrer is installed inside the shell, the outlet II of the electrofiltration dust removal and plasma catalytic oxidation unit is connected to the inlet II at the top of the shell through a pipe, an electric heating device is installed at the bottom of the shell, the spraying device is installed at the top inside the shell, the liquid outlet is installed at the bottom of the shell, the bottom outlet is connected to the filter device, and the filter device is connected to the evaporation crystallization device.

[0011] The spraying agent is a Ca(OH)2 or NaOH solution with a concentration of 8% to 25%; the crystallizing agent is one or more of dimethyl sulfoxide, anhydrous methanol, and anhydrous ethanol; and the crystallization temperature is set to 20℃ to 90℃.

[0012] When the above-mentioned device is used, a mixture of waste salt and combustion aid is added during the heating process of the high-temperature melting oxidation furnace. The flue gas generated in the melting furnace is collected by a flue gas collection hood and then returned to the molten waste salt at the bottom of the high-temperature melting oxidation furnace through a venturi tube for complete combustion and decomposition. After that, it moves upward through the hole in the middle of the flue gas collection hood. During this process, some of it is captured by the downward transported waste salt material, thereby achieving source blockage and control of pollutants. The O2 in the flue gas discharged from the melting furnace generates active free radicals after corona discharge, which promotes the catalytic degradation of pollutants such as VOCs and dioxins in the flue gas. The fully oxidized sulfur and nitrate in the flue gas are captured and directionally crystallized into Na2SO4 / NaNO3 and CaSO4 / Ca(NO3)2.

[0013] The crystallizer heating device and stirring equipment are commercially available devices.

[0014] This invention achieves waste salt melting oxidation detoxification, efficient flue gas purification, and sulfur and nitrate resource utilization through source blockage, process control, and sulfur and nitrate resource utilization. It can eliminate the flue gas pollution problem in the traditional waste salt melting process, and also achieve efficient purification of melting flue gas through a short process, providing a solution to the technical problems existing in the high-temperature melting detoxification and cleaning treatment of waste salt. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the device used in the method of the present invention;

[0016] In the diagram: 1. High-temperature melting oxidation furnace; 1-1. Feeding port; 1-2. Combustion gas inlet; 1-3. Air pump; 1-4. Venturi tube; 1-5. Molten salt outlet I; 1-6. Molten salt outlet II; 1-7. Gas outlet I; 1-8. Flue gas collection hood; 2. Electrofiltration dust removal and plasma catalytic oxidation unit; 2-1. Corona electrode; 2-2. Filter cloth; 2-3. Catalyst packing; 2-4. Gas inlet I; 2-5. Gas outlet II; 3. Flue gas spray crystallization unit; 3-1. Stirrer; 3-2. Gas inlet II; 3-3. Electric heating device; 3-4. Spray device; 3-5. Gas outlet III; 3-6. Liquid outlet; 3-7. Filter device; 4. Evaporation crystallization device. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the content described. Example 1

[0018] like Figure 1As shown, the apparatus used in this embodiment includes a high-temperature melting oxidation furnace 1, an electrofiltration dust removal and plasma catalytic oxidation device 2, a flue gas spray crystallization device 3, and an evaporation crystallization device 4. The high-temperature melting oxidation furnace 1 includes a shell with a feeding port 1-1 and an outlet I 1-7 at the top, and molten salt outlet I 1-5 and molten salt outlet II 1-6 at the bottom. The shell is divided into three chambers by two flue gas collection hoods. The flue gas collection hoods are hollow inverted frustum shapes with openings at the top and bottom. The chamber between the two flue gas collection hoods is connected to the bottom of the shell via pipes and Venturi tubes 1-4. A combustion-supporting gas inlet 1-2 and a gas pump 1-3 are installed on the pipes. The third chamber from the top is connected to the bottom of the shell via pipes and Venturi tubes. The electrofiltration dust removal and plasma catalytic oxidation unit 2 includes a shell with a cylindrical filter cloth 2-2 at the center. A catalyst packing element 2-3 is fitted onto the outside of the filter cloth. Three corona electrodes 2-1 are set on the outside of the catalyst packing element 2-3. A corona electrode is set at the center of the cylindrical filter cloth 2-2. The outlet I1-7 of the high-temperature melting oxidation furnace is connected to the inlet I2-4 at the top of the shell through a pipe. An outlet II2-5 is set at the bottom of the shell. The alkaline solution spraying in the flue gas spraying crystallization unit 3 includes a shell. A stirrer 3-1 is set inside the shell. The outlet II2-5 of the electrofiltration dust removal and plasma catalytic oxidation unit is connected to the inlet II3-2 at the top of the shell through a pipe. An electric heating device 3-3 is set at the bottom of the shell. A spraying device 3-5 is set at the top inside the shell. A liquid outlet 3-6 is set at the bottom of the shell. The bottom outlet is connected to the filter device 3-7. The filter device 3-7 is connected to the evaporation crystallization device 4. The corona electrode is connected to the power supply.

[0019] The waste salt is a mixture of salts containing chlorine, nitrate, sulfur and volatile organic components, with a water content of 30%; the combustion aid is potassium chlorate, the filter cloth is carbon fiber filter cloth, the catalyst in the catalyst packing is a zeolite catalyst supported on Co and Fe, the corona electrode is a stainless steel electrode; the spraying agent is a 12% Ca(OH)2 solution; and the crystallizing agent is dimethyl sulfoxide.

[0020] A mixture of waste salt and combustion aid (5% of the waste salt) is added to the high-temperature melting oxidation furnace 1, while combustion aid (a mixture of nitrogen-loaded H2 and O2, with contents of 25% and 20% respectively) is introduced. During the heating process to 800℃, pollutants in the waste salt are oxidized and decomposed under high temperature and oxygen conditions. The generated flue gas is collected through flue gas collection hoods 1-8 and returned to the molten waste salt at the bottom of the high-temperature melting oxidation furnace through venturi tubes 1-4 for complete combustion and decomposition. Then, it moves upward through the holes on the flue gas collection hood. During this process, some of it is captured by the downward-transporting waste salt material, achieving source control of pollutants. The high-temperature melting oxidation furnace then enters the electrofiltration dust removal and plasma catalytic oxidation unit 2, powered by a DC high-voltage power supply. The discharge voltage is 10kV. After the O2 in the flue gas is corona discharged, it generates active free radicals. The small amount of VOCs and dioxins that escape from the flue gas react with the free radicals generated by the corona electrode. After filtration through the filter cloth, they are fully adsorbed and catalytically oxidized into stable gaseous products through the catalyst packing. At the same time, the electrofiltration and catalytic oxidation remove dust from the flue gas and oxidize some acidic gases. After treatment, the flue gas enters the flue gas spray crystallization unit 3. A 12% Ca(OH)2 solution is sprayed on the flue gas containing NOx, SOx and some acidic gases to capture the fully oxidized sulfur and nitrate in the flue gas. The spray liquid is heated to 25°C by an electric heating device 3-3, and Ca(SO)4 crystals are generated under the action of dimethyl sulfoxide.

[0021] The purification efficiency of VOCs (total) in the generated flue gas was 98.4%, the purification efficiency of dioxins was 97.3%, the purification efficiency of acidic gases was 99.4%, the purification efficiency of NOx was 99.5%, and the purification efficiency of SOx was 99.2%. The purity of the waste salt collected after melting was 98.58%; the purity of CaSO4 was 97.25%, the content of α-type crystals was greater than 83.5%, and the crystals were uniform and obvious.

[0022] Example 2: The structure of the device in this example is the same as that in Example 1, except that the water content of the waste salt is 40%, the combustion aid in the waste salt is potassium nitrate with a content of 10%, the combustion aid is a nitrogen-containing H2 and O2 mixture with contents of 30% and 23% respectively, the filter cloth is a nickel-chromium alloy filter cloth, the catalyst in the catalyst packing is a zeolite catalyst supported on Fe and Cu, the corona electrode is an electroplated IrO3 electrode, the power supply is a DC high voltage power supply with a discharge voltage of 15kV, the collection liquid is a 16% NaOH solution, which is used to collect the fully oxidized sulfur and nitrate in the flue gas, and the spray liquid is heated to 45°C by an electric heating device 3-3, and Na2SO4 crystals are generated under the action of anhydrous ethanol.

[0023] This embodiment involves the melt oxidation of sulfur salts containing organic pollutants. The furnace temperature is set to 850°C, the power supply is a DC high-voltage power supply, and the discharge voltage is 15kV. The crystallization temperature is 45°C. The purification efficiency of VOCs (total) in the generated flue gas is 99.0%, dioxin purification efficiency is 98.6%, acid gas purification efficiency is 99.8%, NOx purification efficiency is 99.9%, and SOx purification efficiency is 99.9%. The purity of the waste salt collected after melting is 98.58%; the purity of Na2SO4 is 96.25%, and the crystals are uniform and obvious.

[0024] Example 3: The structure of the device in this example is the same as that in Example 1, except that the water content of the waste salt is 40%, the combustion aid in the waste salt is manganese dioxide with a content of 15%, the combustion aid is a mixture of nitrogen-loaded H2 and O2 with contents of 35% and 30% respectively, the filter cloth is a zirconium oxide filter cloth, the catalyst in the catalyst packing is a zeolite catalyst loaded with Fe and Cu, the corona electrode is a Ti / IrO3 plated electrode, and the collection liquid is a 16% Ca(OH)2 solution to collect fully oxidized sulfur and nitrate in the flue gas. The spray liquid is heated to 55°C by an electric heating device 3-3, and Ca(NO3)2 crystals are generated under the action of anhydrous methanol.

[0025] This embodiment involves the melt oxidation of waste salt containing nitrates and organic pollutants. The melting furnace temperature is set to 950℃, the power supply is a DC high-voltage power supply, and the discharge voltage is 15kV. The crystallization temperature is 55℃. The purification efficiency of VOCs (total) in the generated flue gas is 99.2%, the purification efficiency of dioxins is 98.5%, the purification efficiency of acidic gases is 99.6%, the purification efficiency of NOx is 99.5%, and the purification efficiency of SOx is 99.2%. The purity of the waste salt collected after melting is 98.58%; the purity of Ca(NO3)2 is 99.65%, and the crystals are uniform and obvious.

Claims

1. A method for the oxidation, melting, detoxification, and short-process purification of waste salt and flue gas, characterized in that: Pharmaceutical waste salt and combustion aid are mixed and placed in a high-temperature melting oxidation furnace. Combustion aid is introduced, and pollutants in the waste salt are oxidized and decomposed under high temperature and oxygen conditions. The flue gas generated during the melting oxidation process is collected and recycled back into the molten waste salt in the high-temperature melting oxidation furnace, so that the volatile organic components in the waste salt are oxidized and decomposed under high temperature and oxygen conditions, achieving melting and detoxification of multiple pollutants in the waste salt. Corona discharge is applied to the subsequent flue gas to generate active free radicals, which, combined with electrofiltration and catalytic oxidation, remove dust from the flue gas, further degrading the remaining VOCs and dioxin organic pollutants, and oxidizing some acidic gases. Alkaline solution is used to spray the flue gas containing NOx, SOx and some acidic gases. A crystallizing agent is added to the spray solution to achieve directional crystallization of sulfates and nitrates. The high-temperature melting oxidation furnace (1) includes a shell, with a feeding port (1-1) and an air outlet I (1-7) at the top of the shell, and molten salt outlet I (1-5) and molten salt outlet II (1-6) at the bottom. The shell is divided into three chambers by two flue gas collection hoods. The chamber between the two flue gas collection hoods is connected to the bottom of the shell through a pipe and a venturi tube (1-4). The pipe is equipped with a combustion gas inlet (1-2) and an air pump (1-3). The third chamber from the top is connected to the bottom of the shell through a pipe and a venturi tube. The flue gas collection hood is a hollow, inverted frustum shape; The device for subsequent flue gas treatment is an electrostatic filtration and plasma catalytic oxidation unit (2), which includes a shell, a cylindrical filter cloth (2-2) is provided in the center of the shell, a cylindrical catalyst packing (2-3) is fitted on the outside of the filter cloth, two or more corona electrodes (2-1) are provided on the outside of the catalyst packing (2-3), a corona electrode is provided in the center of the cylindrical filter cloth (2-2), the outlet I (1-7) of the high-temperature melting oxidation furnace is connected to the inlet I (2-4) at the top of the shell through a pipe, and the outlet II (2-5) is provided at the bottom of the shell. Alkali spraying is carried out in the flue gas spraying crystallization unit (3), which includes a shell, a stirrer (3-1) is installed inside the shell, the outlet II (2-5) of the electrofiltration dust removal and plasma catalytic oxidation unit is connected to the inlet II (3-2) at the top of the shell through a pipe, an electric heating device (3-3) is installed at the bottom of the shell, a spraying device (3-5) is installed at the top inside the shell, a liquid outlet (3-6) is installed at the bottom of the shell, and the bottom outlet is connected to the filter device (3-7). The filter device (3-7) is connected to the evaporation crystallization device (4). The combustion-supporting gas is nitrogen-loaded H2 and O2, with each H2 and O2 content ranging from 10% to 50%.

2. The method for waste salt oxidation, melting, detoxification, and short-process flue gas purification according to claim 1, characterized in that: The waste salt has a moisture content of 30% to 90%; the combustion aid is one or more of potassium chlorate, potassium nitrate, manganese dioxide, magnesium oxide, aluminum oxide, iron tetroxide, iron oxide, and ferric chloride; the spraying agent is a Ca(OH)2 or NaOH solution with a concentration of 8% to 25%; and the crystallizing agent is one or more of dimethyl sulfoxide, anhydrous methanol, and anhydrous ethanol.

3. The method for waste salt oxidation, melting, detoxification, and short-process flue gas purification according to claim 1, characterized in that: The temperature inside the high-temperature melting oxidation furnace is 200℃~1300℃.

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