Industrial waste salt treatment system and process

Abstract

The application provides an industrial waste salt treatment system and process, and the treatment system comprises a pyrolysis module, an intermediate treatment module and a melting module, the pyrolysis module comprises a rotary kiln, and the industrial waste salt is preliminarily pyrolyzed; the intermediate treatment module comprises a separation device, the preliminary product is separated into coarse salt and fine salt by the separation device, and the coarse salt is crushed and then sent to the rotary kiln; the melting module comprises a melting furnace, and the separation device sends the fine salt into the melting furnace; the melting furnace is provided with a burner, a plurality of secondary air nozzles and a salt outlet, flue gas in the melting furnace moves tangentially along the axial direction of the melting furnace around the furnace wall, and the salt outlet is arranged at the bottom of the melting furnace. The above-mentioned industrial waste salt treatment system and process make the industrial waste salt be treated through the processes of pyrolysis, separation and melting, the TOC is preliminarily reduced, then the industrial waste salt enters the melting furnace, and the mass transfer effect is fully generated in the melting furnace, so that the TOC is deeply removed, the TOC of the industrial waste salt is reduced to below 5ppm, and the product quality is greatly improved, which is convenient for further collection and treatment.

Description

Technical Field

[0001] This invention relates to an industrial waste salt treatment system and process. Background Technology

[0002] Industrial production generates a large amount of waste salt every year, which is one of the main sources of industrial solid waste or hazardous waste. Its disposal and utilization have always been a key concern in the industrial sector. Most industrial waste salt is classified as hazardous waste due to its varying impurity content and high degree of harm, and it is currently not being properly disposed of, resulting in significant environmental pressure.

[0003] Current technologies for treating hazardous industrial waste salts are similar to those for traditional hazardous waste, primarily involving incineration and landfill. Landfilling is often temporary, occupying large amounts of land and causing long-term environmental pollution, failing to fundamentally solve the problem of industrial waste salt utilization. However, incineration can cause inorganic salts to melt, leading to severe corrosion of high-temperature refractory materials. Furthermore, the flue gas may carry molten inorganic salts, which can cool and crystallize in subsequent treatment equipment, causing blockages in equipment and pipelines. Therefore, most incineration facilities are unwilling to accept hazardous industrial waste salts for disposal.

[0004] Given the above situation, more advanced solutions are needed for the resource recovery and harmless utilization of industrial waste salt. Current technical solutions mainly consist of two steps: organic and inorganic impurity removal. While the inorganic impurity removal step has mature industrial processes such as ion-exchange membrane brine refining that can be referenced and learned from, the organic impurity removal step is currently the key and challenging aspect of industrial waste salt resource recovery and harmless utilization. Existing organic impurity removal methods include different types such as disc heating volatilization, wet oxidation, rotary kiln anaerobic pyrolysis, and high-temperature melting. The total organic carbon (TOC) in the treated industrial waste salt ranges from approximately tens to hundreds of ppm.

[0005] Among the existing technical solutions, the product obtained by high-temperature melting treatment of industrial waste salt has the lowest TOC content. However, the high hardness and difficulty in crushing of the product obtained by high-temperature melting treatment of industrial waste salt make it difficult to further dissolve and utilize downstream. The salt content in the molten salt flue gas is also inconvenient to treat. In addition, the existing high-temperature melting treatment system has extremely high energy consumption, low thermal efficiency, and limited applicable types of industrial waste salt, leaving considerable room for improvement. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the existing industrial waste salt treatment system, such as the excessively high TOC content of the treated products, and to provide an industrial waste salt treatment system and process.

[0007] The present invention solves the above-mentioned technical problems through the following technical solution:

[0008] This invention provides an industrial waste salt treatment system, characterized in that the treatment system includes a pyrolysis module, an intermediate treatment module, and a melting module;

[0009] The pyrolysis module includes a rotary kiln for pyrolyzing the industrial waste salt into preliminary products and pyrolysis gas.

[0010] The intermediate processing module includes a separation device connected to the rotary kiln, used to separate the preliminary product into crude salt and fine salt, and to crush the crude salt and send it back into the rotary kiln.

[0011] The melting module includes a melting furnace, and the separation device is connected to the melting furnace for conveying the fine salt into the melting furnace;

[0012] The melting furnace is equipped with a burner, several secondary air nozzles, and a salt outlet. The burner is located at the top of the melting furnace, and the secondary air nozzles are located on the middle section of the furnace wall and are arranged tangentially along the furnace wall to make the flue gas in the melting furnace move tangentially around the furnace wall along the axial direction of the melting furnace. The salt outlet is located at the bottom of the melting furnace.

[0013] In this technical solution, industrial waste salt first enters a rotary kiln for preliminary pyrolysis to remove water and some organic matter, thus initially reducing TOC. After pyrolysis, the industrial waste salt enters a separation device, and the separated coarse salt is returned to the rotary kiln for re-pyrolysis. The separated fine salt enters the melting furnace through a burner, and the flue gas is tangentially moved by air intake through a secondary air nozzle. This allows the fine salt to undergo sufficient mass transfer with the flue gas as it flows downwards in the furnace, achieving deep removal of TOC from the industrial waste salt and reducing the TOC of the industrial waste salt to below 5 ppm. The treated industrial waste salt naturally exits the melting furnace through the salt outlet under gravity, facilitating collection and further processing.

[0014] Preferably, the pyrolysis module further includes a first silo and a feeding device connected sequentially along the direction of movement of industrial waste salt. The feeding device is connected to the rotary kiln and is frequency-controlled to control the feed rate of the rotary kiln. A pyrolysis gas pipeline is provided between the rotary kiln and the melting furnace to send the pyrolysis gas in the rotary kiln to the melting furnace for combustion.

[0015] In this technical solution, the amount of industrial waste salt entering the rotary kiln is controllable, ensuring that the industrial waste salt is always treated uniformly and effectively. The organic matter in the industrial waste salt is decomposed into combustible small molecule gas and elemental carbon black by heating in the rotary kiln. Together with the impurities water in the waste salt that are converted into water vapor, they form pyrolysis gas. Sending the pyrolysis gas to the melting furnace for combustion can make full use of the organic matter in it and reduce the overall energy consumption of the treatment system.

[0016] Preferably, the burner is a swirl burner, and the secondary air nozzles are symmetrically distributed around the axial direction of the melting furnace, with the number of secondary air nozzles being 4 or 8.

[0017] In this technical solution, industrial waste salt enters the furnace through a cyclone burner. The secondary air blown out by the tangentially symmetrically arranged secondary air nozzles forms a tangential motion. During the downward flow in the melting furnace, it fully undergoes mass transfer with the flue gas, thereby deeply removing TOC.

[0018] Preferably, the processing system further includes an exhaust gas treatment module connected to the melting furnace; the exhaust gas treatment module includes a spray cylinder, which is cylindrical, with a water curtain inside and nozzles on the top inner surface. When the nozzles are working, they spray coolant into the internal space and inner wall of the spray cylinder; the bottom of the spray cylinder has a coolant outlet, and the outer wall of the spray cylinder is surrounded by a water-cooling jacket.

[0019] In this technical solution, the high-temperature flue gas in the melting furnace enters the tail gas treatment module. The water curtain in the spray tube rapidly cools the flue gas. The coolant sprayed by the nozzles onto the inner wall of the spray tube washes away the condensed industrial waste salt adhering to the inner wall, ensuring unobstructed flow inside the spray tube. The coolant leaves the spray tube through the coolant outlet at the bottom of the spray tube and can be used for subsequent treatment of the industrial waste salt. The water-cooled jacket maintains a uniform temperature on the outer shell of the spray tube, ensuring that the industrial waste salt is cooled evenly.

[0020] Preferably, the spray cylinder is provided with a flue gas outlet, and a first flue gas pipe is provided between the flue gas outlet and the rotary kiln for sending part of the flue gas generated by the melting furnace back to the rotary kiln; a salt powder dust collector is provided between the flue gas outlet and the first flue gas pipe; the melting furnace is provided with an air inlet, and a second flue gas pipe is provided between the air inlet and the rotary kiln; the heat exchange method of the rotary kiln is indirect wall heat exchange;

[0021] The melting module also includes a primary air fan connected to the air inlet; a heat exchanger is provided between the primary air fan and the air inlet, and the second flue gas duct is connected to the heat exchanger to send the flue gas that has completed heat exchange in the rotary kiln into the heat exchanger for non-contact heat exchange with the air.

[0022] In this technical solution, the high-temperature flue gas, after entering the spray tube for desalination and dust removal and undergoing preliminary cooling, is sent to the rotary kiln for heat exchange. After exiting the rotary kiln, the air sent to the melting furnace by the primary air fan is further preheated, reducing the relative humidity of the air and preventing water vapor in the primary air from precipitating out upon contact with the pyrolyzed industrial waste salt, thus preventing the industrial waste salt from becoming damp. At the same time, the waste heat of the high-temperature flue gas is effectively utilized, improving the overall thermal efficiency of the treatment system. Meanwhile, the indirect heat exchanger isolates the flue gas from the rotary kiln, avoiding any impact on the industrial waste salt inside the rotary kiln. The residual salt in the flue gas exiting the flue gas outlet is adsorbed and collected by the salt powder dust collector, ensuring that only flue gas enters the first flue gas duct, thereby improving the overall productivity of the treatment system.

[0023] Preferably, the intermediate processing module further includes a cooling device, a conveying device, and an intermediate storage tank connected in sequence along the direction of movement of industrial waste salt, and the outlet of the intermediate storage tank is connected to the separation device.

[0024] In this technical solution, the industrial waste salt that has undergone preliminary pyrolysis treatment is sent to a cooling device for cooling, and then conveyed to an intermediate storage tank by a conveying device. It is then separated into coarse salt and fine salt by a separation device for subsequent collection and processing.

[0025] Preferably, the intermediate storage tank includes a first intermediate storage tank and a second intermediate storage tank arranged in parallel, and the bottom of the first intermediate storage tank and the second intermediate storage tank are provided with discharge ports, and the conveying equipment is connected to the first intermediate storage tank or the second intermediate storage tank.

[0026] The separation device further includes a second silo, and the separation device is provided with a coarse salt outlet and a fine salt outlet; the fine salt outlet is connected in sequence to the second silo and the melting furnace; the second silo is provided with a heating device to make the air temperature in the second silo higher than the ambient temperature; the coarse salt outlet is connected in sequence to the rotary kiln through a crusher and a coarse salt pipeline, for crushing the coarse salt separated by the separation device and sending it to the rotary kiln for reprocessing; the cooling equipment, the conveying equipment, the first intermediate storage tank and the second intermediate storage tank are all provided with water-cooled jackets on their outer sides.

[0027] In this technical solution, the conveying equipment can adjust its operating direction. Once one intermediate storage tank is full, the direction can be adjusted to convey the pyrolyzed industrial waste salt to another intermediate storage tank, and the discharge port at the bottom of the full intermediate storage tank can be opened to discharge the waste salt. The separation device separates the pyrolyzed industrial waste salt into coarse salt and fine salt. The coarse salt is sent back to the rotary kiln for processing, thereby ensuring the quality of the industrial waste salt entering the melting furnace. At the same time, it isolates the intermediate processing module from the outside world, improving the sealing of the processing system. The second silo is equipped with a heating device to maintain the relative humidity of the air in the second silo at a low level, thereby effectively inhibiting the precipitation of moisture in the air and ensuring the dryness of the industrial waste salt in the second silo. The cooling equipment, conveying equipment, first intermediate storage tank and second intermediate storage tank are equipped with water-cooled jackets, so that the industrial waste salt therein is effectively and uniformly cooled.

[0028] Preferably, the melting module further includes a discharge conveying device, and the bottom of the melting furnace is connected to the discharge conveying device through the salt outlet.

[0029] In this technical solution, industrial waste salt is processed in the melting furnace and then enters the discharge conveying device through the salt outlet. It is then sent out of the melting furnace and collected for subsequent processing and utilization.

[0030] Preferably, the discharge conveying device includes a condensing device and a discharge conveying device. The condensing device is equipped with a scraper inside for scraping off the solidified product on the inner surface of the condensing device and letting it fall onto the discharge conveying device. The condensing device is equipped with a heat transfer oil cooling structure inside and a heat transfer oil cooler outside the condensing device. The heat transfer oil cooler and the heat transfer oil cooling structure form a heat transfer oil circulation loop.

[0031] In this technical solution, the condensation equipment dissipates heat through heat transfer oil circulation, so that the industrial waste salt falling into the condensation equipment is effectively and uniformly cooled. After it solidifies, it is scraped off and falls onto the discharge conveyor equipment for transportation and collection.

[0032] The present invention also provides a process for treating industrial waste salt, wherein the process uses the treatment system described above, and the process includes the following steps:

[0033] The TOC of the industrial waste salt entering the treatment system is 200ppm to 20000ppm. The industrial waste salt enters the pyrolysis module and is fed into the rotary kiln for pyrolysis, where it is separated into pyrolysis gas and preliminary products. The preliminary products enter the intermediate treatment module. The temperature inside the rotary kiln is maintained at 350℃ to 550℃, the pressure inside the rotary kiln is 0 to 2kPa, and the residence time of the industrial waste salt in the rotary kiln is 0.5 to 3 hours.

[0034] The initial product enters the separation device, where it is separated into crude salt and fine salt. The crude salt is returned to the rotary kiln for reprocessing, while the fine salt enters the melting furnace. The temperature inside the melting furnace is maintained at 850–1200°C, and the pressure inside the melting furnace is -5–3 kPa. The residence time of the industrial waste salt in the melting furnace is 0.5–3 minutes. The particle size of the crude salt is greater than 0.3 mm. The fine salt enters the melting furnace from the top and is burned and melted by the burner and the secondary air nozzle, generating flue gas and solid products. The TOC of the solid products is preferably less than 5 ppm. More preferably, the operating temperature of the melting furnace is maintained above 950°C, the residence time of the industrial waste salt in the melting furnace is less than 1.5 minutes, the pressure inside the melting furnace is -1–1 kPa, and the TOC of the solid products is less than 2 ppm. In this technical solution, the industrial waste salt undergoes a series of processes including pyrolysis, separation, and melting. Through the industrial waste salt treatment system, the TOC of the final product is reduced to below 5 ppm, greatly improving product quality and facilitating subsequent utilization and processing.

[0035] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0036] The positive and progressive effects of this invention are as follows:

[0037] The aforementioned industrial waste salt treatment system and process allow industrial waste salt to undergo a series of processes including pyrolysis, separation, and melting. First, water and some organic matter are removed, initially reducing the total organic matter (TOC) before the waste salt enters the melting furnace. Within the furnace, sufficient mass transfer occurs, achieving deep TOC removal and reducing the TOC to below 5 ppm, significantly improving product quality. Furthermore, the system can handle different types of industrial waste salt, including both single and mixed salts, enhancing its versatility. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the industrial waste salt treatment system of the present invention.

[0039] Explanation of reference numerals in the attached figures

[0040] Raw material salt bucket elevator 1;

[0041] First silo 2;

[0042] Raw salt feeding auger 3;

[0043] Rotary kiln feed auger 4;

[0044] Rotary kiln 5, flue gas tail treatment device 51, pyrolysis gas pipeline 52;

[0045] Cooling equipment 6;

[0046] Conveying equipment 7;

[0047] Intermediate storage tank 8, first intermediate storage tank 81, second intermediate storage tank 82;

[0048] Separation device 9;

[0049] The middle dragon 10;

[0050] 11. Pyrolytic salt bucket elevator;

[0051] Second silo 12;

[0052] Second material storage silo bottom dragon 13;

[0053] Dust collector 14;

[0054] 15mm discharge ash hopper;

[0055] 16 pyrolysis gas blowers;

[0056] Primary air fan 17;

[0057] Heat exchanger 18;

[0058] Secondary air fan 19;

[0059] Melting furnace 20, burner 201, condensing equipment 202, secondary air nozzle 203, natural gas transmission station 204;

[0060] Heat transfer oil cooler 21;

[0061] Discharge conveyor 22;

[0062] Discharge hopper 23;

[0063] Sprayer cylinder 24, spray head 241;

[0064] Salt dust collector 25, first flue gas duct 251, second flue gas duct 252;

[0065] Coolant circulation device 26;

[0066] Coolant circulation pump 27;

[0067] Cooling water supply 101, cooling water return 102, air flow path 103, nitrogen flow path 104, coarse salt flow path 105, salt dissolving system flow path 106;

[0068] Solid flow path S1~S7;

[0069] Gas flow paths G1~G12;

[0070] Coolant flow paths DW1~DW4, atomizing coolant flow path DW5, water curtain coolant flow path DW6;

[0071] Cooling oil flow path OIL1~OIL2. Detailed Implementation

[0072] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0073] Example 1

[0074] like Figure 1 The diagram shows an embodiment of the industrial waste salt treatment system of the present invention. This industrial waste salt treatment system includes a pyrolysis module, an intermediate treatment module, and a melting module. The pyrolysis module includes a rotary kiln 5, used to pyrolyze industrial waste salt into preliminary products and pyrolysis gas. The intermediate treatment module includes a separation device 9, connected to the rotary kiln 5, used to separate the preliminary products into coarse salt and fine salt. The separation device 9 is also used to crush the coarse salt and return it to the rotary kiln 5. The melting module includes a melting furnace 20, with the separation device 9 connected to the melting furnace 20, used to transport fine salt into the melting furnace 20. The melting furnace 20 is equipped with a burner 201, several secondary air nozzles 203, and a salt outlet. The burner 201 is located at the top of the melting furnace 20, and the secondary air nozzles 203 are located on the middle section of the furnace wall of the melting furnace 20, arranged tangentially along the furnace wall, to allow the flue gas inside the melting furnace 20 to move tangentially around the furnace wall along the axial direction of the melting furnace 20. The salt outlet is located at the bottom of the melting furnace 20. Industrial waste salt first enters rotary kiln 5 for preliminary pyrolysis to remove water and some organic matter, thus initially reducing TOC. After pyrolysis, the industrial waste salt enters separation device 9, and the separated coarse salt is returned to rotary kiln 5 for re-pyrolysis. The separated fine salt, along with air blown in by primary blower 17 and natural gas supplied by natural gas transmission station 204, enters melting furnace 20 through burner 201. The natural gas is burned in melting furnace 20 to generate high-temperature flue gas, maintaining the temperature inside melting furnace 20 at 950℃. Secondary air is pressurized and blown in by secondary blower 19, entering melting furnace 20 through secondary air nozzle 203, causing the flue gas to move tangentially. This causes the molten salt to adhere to the inner surface of melting furnace 20 as it moves with the flue gas, allowing for sufficient mass transfer with the flue gas as it flows downwards along the furnace, achieving deep removal of TOC from the industrial waste salt. The treated industrial waste salt naturally exits melting furnace 20 through the salt outlet under gravity, facilitating collection and further processing.

[0075] In other embodiments, if the TOC content of the raw salt is low, it can be directly fed into the melting furnace 20 without going through the pyrolysis module.

[0076] The pyrolysis module also includes a first silo 2 and a feeding device connected sequentially along the direction of movement of industrial waste salt. The feeding device is connected to the rotary kiln 5 and is frequency-controlled to control the feed rate of the rotary kiln 5. A pyrolysis gas pipeline 52 is provided between the rotary kiln 5 and the melting furnace 20 to send the pyrolysis gas in the rotary kiln 5 to the melting furnace 20 for combustion. The pyrolysis gas is drawn by the pyrolysis gas blower 16, leaves the rotary kiln 5 through the pyrolysis gas pipeline 52, and enters the melting furnace 20 after the dust is removed by the dust collector 14. The dust collector 14 is a cyclone dust collector, but other types of dust collection devices can also be used. A discharge ash hopper is connected below the dust collector 14. 15; The feeding device includes a raw salt feeding auger 3 and a rotary kiln feeding auger 4 connected in sequence. Industrial waste salt is lifted to the first silo 2 by the raw salt bucket elevator 1. The industrial waste salt in the first silo 2 is sent to the rotary kiln feeding auger 4 by the raw salt feeding auger 3, and then sent into the rotary kiln 5 to undergo pyrolysis reaction. The residence time of industrial waste salt in the rotary kiln 5 is 2 hours. In other embodiments, the specific residence time of industrial waste salt can be adjusted according to the content of impurities such as water and organic matter in the industrial waste salt to ensure that the morphology of the waste salt after pyrolysis meets the feeding requirements of the melting furnace 20. The TOC of the industrial waste salt leaving the rotary kiln 5 is about 300 ppm. The feed rate of rotary kiln 5 is mainly controlled by frequency conversion of raw salt feed auger 3 to achieve quantitative conveying. The amount of industrial waste salt entering rotary kiln 5 is controllable, ensuring that the industrial waste salt is always treated uniformly and effectively. At the same time, since the raw salt feed auger 3 is inclined upward, as long as industrial waste salt is present in the first hopper 2 during system operation, the rotary kiln 5 can achieve material level sealing, thereby ensuring the overall airtightness of rotary kiln 5. The organic matter in the industrial waste salt is decomposed into combustible small molecule gas and elemental carbon black by heating in rotary kiln 5. Together with the impurities water in the waste salt that are converted into water vapor, they form pyrolysis gas. The pyrolysis gas is sent to the melting furnace 20 for combustion, which can make full use of the organic matter and reduce the overall energy consumption of the treatment system. The discharge ash hopper 15 is convenient for collecting the dust adsorbed from the flue gas for subsequent treatment.

[0077] Burner 201 is a swirl burner, and secondary air nozzles 203 are symmetrically distributed around the axial direction of the melting furnace 20, with a total of 4 secondary air nozzles 203. Industrial waste salt enters the furnace through the swirl burner, and the secondary air blown out by the tangentially symmetrically arranged secondary air nozzles 203 forms a tangential motion. During the downward flow in the melting furnace 20, it fully undergoes mass transfer with the flue gas, thereby deeply removing TOC.

[0078] In other embodiments, the number of secondary air nozzles 203 may also be eight.

[0079] The processing system also includes an exhaust gas treatment module, which is connected to the melting furnace 20;

[0080] The exhaust gas treatment module includes a spray cylinder 24, which is cylindrical. The spray cylinder 24 has a water curtain inside and a nozzle 241 on the top inner surface. When the nozzle 241 is working, it sprays coolant into the internal space and inner wall of the spray cylinder 24. The bottom of the spray cylinder 24 has a coolant outlet, and the outer wall of the spray cylinder 24 is surrounded by a water-cooling jacket. The coolant flows in the coolant flow path DW1 to DW4. After leaving the spray cylinder 24, it enters the coolant circulation device 26 to replenish the coolant. Then, it flows back to the atomizing coolant flow path DW5 or the water curtain coolant flow path DW6 via the coolant circulation pump 27. A portion of it also flows to the salt system flow path 106. The coolant is deionized water. The flue gas leaving the melting furnace 20 has a temperature of 900℃, accompanied by some salt vapor and salt droplets. After entering the exhaust gas treatment module, the water curtain inside the spray cylinder 24 rapidly cools the flue gas to 650℃. During the cooling process, the salt vapor and salt droplets sublimate and solidify respectively, forming salt dust. Some of the salt dust adheres to the wall of the spray cylinder 24. The coolant sprayed from the nozzle 241 cleans the condensed industrial waste salt adhering to the inner wall of the spray cylinder 24, ensuring unobstructed flow inside the spray cylinder 24. The coolant leaves the spray cylinder 24 through the coolant outlet at the bottom of the spray cylinder 24 and can be used for subsequent treatment of industrial waste salt as downstream desalination water. The water-cooled jacket maintains a uniform temperature on the outer shell of the spray cylinder 24, ensuring that the industrial waste salt is cooled evenly.

[0081] The spray cylinder 24 is equipped with a flue gas outlet, and a first flue gas duct 251 is provided between the flue gas outlet and the rotary kiln 5 to send part of the flue gas generated by the melting furnace 20 back to the rotary kiln 5; a salt powder dust collector 25 is provided between the flue gas outlet and the first flue gas duct 251; the melting furnace 20 is equipped with an air inlet, and a second flue gas duct 252 is provided between the air inlet and the rotary kiln 5; the heat exchange method of the rotary kiln 5 is indirect heat exchange; the melting module also includes a primary air fan 17, which is connected to the air inlet; a heat exchanger 18 is provided between the primary air fan 17 and the air inlet, and the second flue gas duct 252 is connected to the heat exchanger 18 to send the flue gas that has completed heat exchange in the rotary kiln 5 into the heat exchanger 18 for non-contact heat exchange with the air; the flue gas leaving the heat exchanger 18 enters the flue gas tail treatment device 51 and is discharged after treatment. After being desalinated and dust-removed and initially cooled in spray tube 24, the high-temperature flue gas is sent to rotary kiln 5 for heat exchange, raising the internal temperature of rotary kiln 5 to 450℃. The specific internal temperature of rotary kiln 5 is determined based on the content of water, organic matter, and other impurities in the industrial waste salt, ensuring that the pyrolysis state of the waste salt meets the feeding requirements of melting furnace 20. Simultaneously, the flue gas is cooled to 320℃. After exiting rotary kiln 5, the high-temperature flue gas is further preheated by the air fed into the melting furnace by primary air fan 17, raising the primary air temperature to 60℃, reducing the air moisture content, and preventing the primary air from becoming damp. When the water vapor in the flue gas comes into contact with the pyrolyzed industrial waste salt, it precipitates out, causing the industrial waste salt to become damp. At the same time, the waste heat of the high-temperature flue gas is effectively utilized, improving the overall thermal efficiency of the treatment system. Meanwhile, the indirect heat exchange isolates the flue gas from the rotary kiln 5, avoiding affecting the industrial waste salt inside the rotary kiln 5. The residual salt in the flue gas flowing out of the flue gas outlet is adsorbed and collected by the salt powder dust collector 25, so that only flue gas enters the first flue gas duct 251, improving the overall output of the treatment system. The salt powder dust collector 25 is a cyclone dust collector, or a ceramic fiber filter tube dust collector can also be used.

[0082] The intermediate processing module also includes a cooling device 6, a conveying device 7, and an intermediate storage tank 8 connected sequentially along the direction of movement of the industrial waste salt. The outlet of the intermediate storage tank 8 is connected to the separation device 9. The industrial waste salt that has undergone preliminary pyrolysis treatment is sent to the cooling device 6 for cooling, and then sent to the intermediate storage tank 8 by the conveying device 7. It is then separated into coarse salt and fine salt by the separation device 9 for subsequent collection and processing.

[0083] The intermediate storage tank 8 includes a first intermediate storage tank 81 and a second intermediate storage tank 82 arranged in parallel. The bottom of both intermediate storage tanks 81 and 82 has a discharge port. The conveying equipment 7 is connected to either the first intermediate storage tank 81 or the second intermediate storage tank 82. The separation device 9 also includes a second silo 12, which has a coarse salt outlet and a fine salt outlet. The fine salt outlet is sequentially connected to the intermediate auger 10, the pyrolysis salt bucket elevator 11, and the second silo 12. The second silo 12 is equipped with a heating device to maintain the air temperature inside the silo. The temperature is higher than the ambient temperature; the second silo 12 is connected to the melting furnace 20 through the bottom auger 13 of the second silo; the coarse salt outlet is connected to the coarse salt flow path 105, so that the coarse salt is temporarily stored after leaving the separation device 9. After the quantity meets the requirements, it is connected to the rotary kiln 5 through the crusher and the coarse salt pipeline in sequence and sent to the rotary kiln 5 for reprocessing; the cooling equipment 6, the conveying equipment 7, the first intermediate storage tank 81 and the second intermediate storage tank 82 are all equipped with water-cooled jackets on the outside; the cooling equipment 6 is a slag remover or a scraper conveyor; the separation device 9 is a vibrating screen. The conveying device 7 can adjust its running direction. After one intermediate storage tank is full, it can adjust its direction to convey the pyrolysis-treated industrial waste salt to another intermediate storage tank and open the discharge port at the bottom of the full intermediate storage tank to achieve discharge from the tank. The separation device 9 separates the pyrolysis-treated industrial waste salt into coarse salt and fine salt. The coarse salt is crushed and sent back to the rotary kiln 5 for processing, thereby ensuring the quality of the industrial waste salt entering the melting furnace 20. At the same time, it isolates the intermediate processing module from the outside world and improves the sealing of the processing system. The second silo 12 is equipped with a heating device to make the air temperature in the second silo 12 15°C higher than the ambient temperature and maintain the relative humidity of the air in the second silo 12 at a low level, thereby effectively inhibiting the precipitation of moisture in the air and ensuring the dryness of the industrial waste salt in the second silo 12. The cooling device 6, the conveying device 7, the first intermediate storage tank 81 and the second intermediate storage tank 82 are equipped with water-cooled jackets, so that the industrial waste salt therein is effectively and uniformly cooled.

[0084] The melting module also includes a discharge conveying device, which is connected to the bottom of the melting furnace 20 through a salt outlet. After being processed inside the melting furnace 20, the industrial waste salt enters the discharge conveying device through the salt outlet, is sent out of the melting furnace 20, and is collected for subsequent processing and utilization.

[0085] The discharge conveying device includes a condensing device 202 and a discharge conveying device 22. The condensing device 202 has a scraper 202 inside, used to scrape off the solidified product from its inner surface and allow it to fall onto the discharge conveying device 22. The discharge conveying device 22 is connected to the discharge hopper 23. The condensing device 202 has a heat transfer oil cooling structure inside and a heat transfer oil cooler 21 outside. The heat transfer oil cooler 21 and the heat transfer oil cooling structure are connected through cooling oil flow paths OIL1 to OIL2, forming a heat transfer oil circulation loop. The condensing device 202 is a drum-type slag cooler. The condensing device 202 dissipates heat through heat transfer oil circulation, maintaining its operating temperature at 350℃, ensuring effective and uniform cooling of the industrial waste salt falling into it. After solidification, the salt is scraped off and transported to the discharge conveying device 22 for collection and then sent to the discharge hopper 23 for temporary storage.

[0086] This embodiment also provides a treatment process for industrial waste salt. The treatment process uses the above-described treatment system and includes the following steps:

[0087] Industrial waste salt enters the pyrolysis module and is fed into rotary kiln 5. After pyrolysis, it is divided into pyrolysis gas and preliminary products. The preliminary products enter the intermediate processing module. The temperature inside rotary kiln 5 is maintained at 450℃, the pressure inside rotary kiln 5 is 0.5kPa, and the residence time of industrial waste salt in rotary kiln 5 is 2h.

[0088] The initial product enters the separation device 9, where it is separated into crude salt and fine salt. The crude salt is returned to the rotary kiln 5 for reprocessing, while the fine salt enters the melting furnace 20. The temperature inside the melting furnace 20 is maintained at 950℃, and the pressure inside the melting furnace 20 is -1kPa. The residence time of the industrial waste salt in the melting furnace 20 is 0.75min. The particle size of the crude salt is greater than 0.3mm.

[0089] Fine salt enters the melting furnace 20 from the top, and is burned and melted through the burner 201 and secondary air nozzle 203 to generate flue gas and solid products. The industrial waste salt undergoes a series of processes including pyrolysis, separation, and melting. Through the industrial waste salt treatment system, the TOC of the final product is reduced to below 5 ppm, which greatly improves the product quality and facilitates subsequent utilization and treatment.

[0090] An industrial waste salt treatment center applying the industrial waste salt treatment system of this invention will be established. The main component of the industrial waste salt is sodium chloride, and the TOC content is 3500 ppm. The planned annual processing capacity is 60,000 tons / year, with an annual production time of 7200 hours. The processing capacity of a single production line is 15,000 tons / year. Five production lines applying the industrial waste salt treatment system of this invention will be designed (4 in operation and 1 as a standby). The diameter of the first silo is 3.2m, the diameter of the rotary kiln 5 is approximately 1.7m, and the length is 17m. The diameter of the melting furnace 20 is approximately 5.4m, and the height is approximately 20m. The dimensions of the salt powder dust collector 25 are 6.2m*6.2m*16m. The footprint of a single line is approximately 20m*28m. The installed capacity of the electrical equipment for a single line is approximately 220kW, and the natural gas consumption is approximately 230Nm³. 3 / h. The TOC of the treated waste salt is approximately 2.7ppm.

[0091] In the industrial waste salt treatment system of the present invention, solids flow in solid flow paths S1 to S7, and gases flow in gas flow paths G1 to G12; cooling water flows through cooling water inlet 101 and cooling water return 102, air flows through air flow path 103, and nitrogen flows through nitrogen flow path 104.

[0092] To achieve the technical effect of the industrial waste salt treatment system of the present invention, the system is also equipped with corresponding auxiliary equipment, including a storage site for incoming industrial waste salt, crushing equipment, auxiliary utilities such as fresh water, deionized water, nitrogen, and compressed air, and a transfer and storage site for product salt. These devices and apparatuses are auxiliary equipment to achieve the technical effect of the industrial waste salt treatment system of the present invention, but since they do not affect the integrity of the industrial waste salt treatment system of the present invention, they are not described in detail in this embodiment.

[0093] Example 2

[0094] The industrial waste salt treatment system used in this embodiment is the same as that in Embodiment 1, except that: the operating temperature of the melting furnace 20 is maintained at 1000℃, the residence time of the industrial waste salt in the melting furnace 20 is 1.2 min, and the TOC of the waste salt after treatment is about 1.8 ppm.

[0095] Example 3

[0096] The industrial waste salt treatment system used in this embodiment is the same as that in Embodiment 1, except that: an industrial waste salt treatment center using the industrial waste salt treatment system of this invention is established. The main components of the industrial waste salt are sodium chloride and sodium sulfate, and the TOC content of the industrial waste salt is 3000ppm. The planned annual processing capacity is 30,000 tons / year, the annual production time is 7200 hours, the processing capacity of a single production line is 10,000 tons / year, and four production lines using the industrial waste salt treatment system of this invention are designed (3 in operation and 1 in standby). The diameter of the first silo is 2.6m, the diameter of the rotary kiln 5 is approximately 1.5m, and the length is 15m. The diameter of the melting furnace 20 is approximately 4.32m, and the height is approximately 17m. The dimensions of the salt powder dust collector 25 are 5m*5m*14m. The installed capacity of the electrical equipment on a single line is approximately 185kW, and the natural gas consumption is approximately 198Nm³. 3 / h. The TOC of the treated waste salt is approximately 3.4 ppm.

[0097] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A system for treating industrial waste salt, characterized in that, The processing system includes a pyrolysis module, an intermediate processing module, and a melting module; The pyrolysis module includes a rotary kiln for pyrolyzing the industrial waste salt into preliminary products and pyrolysis gas. The intermediate processing module includes a separation device connected to the rotary kiln, used to separate the preliminary product into crude salt and fine salt, and to crush the crude salt and send it back into the rotary kiln. The intermediate processing module also includes a cooling device, a conveying device, and an intermediate storage tank connected in sequence along the direction of movement of industrial waste salt, and the outlet of the intermediate storage tank is connected to the separation device. The melting module includes a melting furnace, and the separation device is connected to the melting furnace for conveying the fine salt into the melting furnace; The melting furnace is equipped with a burner, several secondary air nozzles and a salt outlet. The burner is located at the top of the melting furnace, and the secondary air nozzles are located on the middle section of the furnace wall and are arranged tangentially along the furnace wall to make the flue gas in the melting furnace move tangentially around the furnace wall along the axial direction of the melting furnace. The salt outlet is located at the bottom of the melting furnace. The separation device also includes a second silo, and the separation device is provided with a coarse salt outlet and a fine salt outlet; the fine salt outlet is connected in sequence to the second silo and the melting furnace; the coarse salt outlet is connected in sequence to the rotary kiln through a crusher and a coarse salt pipeline, for crushing the coarse salt separated by the separation device and sending it to the rotary kiln for reprocessing.

2. The processing system as described in claim 1, characterized in that, The pyrolysis module also includes a first silo and a feeding device connected sequentially along the direction of movement of industrial waste salt. The feeding device is connected to the rotary kiln and is frequency-controlled to control the feed rate of the rotary kiln. A pyrolysis gas pipeline is provided between the rotary kiln and the melting furnace to send the pyrolysis gas in the rotary kiln to the melting furnace for combustion.

3. The processing system as described in claim 1, characterized in that, The burner is a swirl burner, and the secondary air nozzles are symmetrically distributed around the axial direction of the melting furnace. The number of secondary air nozzles is 4 or 8.

4. The processing system as described in claim 1, characterized in that, The processing system also includes an exhaust gas treatment module connected to the melting furnace; the exhaust gas treatment module includes a spray cylinder, which is cylindrical, and a nozzle is provided on the top inner surface of the spray cylinder. When the nozzle is working, it sprays coolant into the internal space and inner wall of the spray cylinder; a coolant outlet is provided at the bottom of the spray cylinder, and a water-cooling jacket is provided around the outer wall of the spray cylinder.

5. The processing system as described in claim 4, characterized in that, The spray cylinder is provided with a flue gas outlet, and a first flue gas pipe is provided between the flue gas outlet and the rotary kiln to send part of the flue gas generated by the melting furnace back to the rotary kiln; a salt powder dust collector is provided between the flue gas outlet and the first flue gas pipe; the melting furnace is provided with an air inlet, and a second flue gas pipe is provided between the air inlet and the rotary kiln; the heat exchange method of the rotary kiln is indirect wall heat exchange; The melting module also includes a primary air fan connected to the air inlet; a heat exchanger is provided between the primary air fan and the air inlet, and the second flue gas duct is connected to the heat exchanger to send the flue gas that has completed heat exchange in the rotary kiln into the heat exchanger for non-contact heat exchange with the air.

6. The processing system as described in claim 1, characterized in that, The intermediate storage tank includes a first intermediate storage tank and a second intermediate storage tank arranged in parallel. The bottom of the first intermediate storage tank and the second intermediate storage tank are provided with discharge ports. The conveying equipment is connected to the first intermediate storage tank or the second intermediate storage tank. The second silo is equipped with a heating device to make the air temperature inside the second silo higher than the ambient temperature; the cooling equipment, the conveying equipment, the first intermediate storage tank and the second intermediate storage tank are all equipped with water-cooled jackets on their outer sides.

7. The processing system as described in claim 1, characterized in that, The melting module also includes a discharge conveying device, and the bottom of the melting furnace is connected to the discharge conveying device through the salt outlet.

8. The processing system as described in claim 7, characterized in that, The discharge conveying device includes a condensing device and a discharge conveying device. The condensing device is equipped with a scraper inside, which is used to scrape off the solidified product on the inner surface of the condensing device and let it fall onto the discharge conveying device. The condensing device is equipped with a heat transfer oil cooling structure inside, and a heat transfer oil cooler is equipped on the outside of the condensing device. The heat transfer oil cooler and the heat transfer oil cooling structure form a heat transfer oil circulation loop.

9. A process for treating industrial waste salt, characterized in that, The processing technology uses the processing system as described in any one of claims 1-8, and the processing technology includes the following steps: The TOC of the industrial waste salt entering the treatment system is 200ppm~20000ppm. The industrial waste salt enters the pyrolysis module and is fed into the rotary kiln for pyrolysis, where it is separated into pyrolysis gas and preliminary products. The preliminary products enter the intermediate treatment module. The temperature inside the rotary kiln is maintained at 350℃~550℃, the pressure inside the rotary kiln is 0~2kPa, and the residence time of the industrial waste salt in the rotary kiln is 0.5~3h. The initial product enters the separation device and is separated into crude salt and fine salt. The crude salt is returned to the rotary kiln for reprocessing, while the fine salt enters the melting furnace. The temperature inside the melting furnace is maintained at 850~1200℃, and the pressure inside the melting furnace is -5~3kPa. The residence time of the industrial waste salt in the melting furnace is 0.5~3min. The particle size of the crude salt is greater than 0.3mm. Fine salt enters the melting furnace from the top, and is burned and melted by the burner and the secondary air nozzle to generate flue gas and solid products.

10. The industrial waste salt treatment process as described in claim 9, characterized in that, The TOC of the solid product is less than 5 ppm; Maintain the operating temperature of the melting furnace above 950°C; The residence time of industrial waste salt in the melting furnace is less than 1.5 minutes; The pressure inside the melting furnace is -1 to 1 kPa.

11. The industrial waste salt treatment process as described in claim 10, characterized in that, The TOC of the solid product is less than 2 ppm.

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