Solid waste salt treatment system and method

Abstract

The embodiment of the invention discloses a solid waste salt treatment system, and belongs to the technical field of waste salt recovery treatment. The system comprises a pyrolysis system and a flue gas treatment system, harmful substances in waste salt are separated from solids to form flue gas through a treatment mode of carrying out secondary pyrolysis on the waste salt and reversely providing hot air at the same time, waste salt recovery and harmful substance decomposition are realized through a flue gas purification process, and the harmless purpose is achieved.

Description

Technical Field

[0001] This disclosure relates to the field of waste salt recycling and treatment technology, specifically to a solid waste salt disposal system and method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of this disclosure and is not necessarily an admission or implication in any way that such information constitutes related technology that is already known to those skilled in the art.

[0003] Waste salt originates from a wide range of industries, has complex characteristic pollutants, and its toxicity is unclear. According to the "Solid Waste Prevention and Control Law," waste salt has been classified as hazardous waste that must undergo special treatment. Key industry sources include pesticides, pharmaceuticals, coal chemicals, printing and dyeing, fly ash and soda ash, and new metallurgical materials.

[0004] Industrial waste salt contains toxic organic and inorganic impurities, posing certain hazards and therefore cannot be directly applied to other industries, such as food or pharmaceuticals. Currently, the main methods for treating industrial waste salt are stockpiling or landfilling, which wastes space and reduces land utilization. Especially when salt and its impurities are lost, it causes serious harm such as soil salinization and environmental pollution. Therefore, harmless treatment and resource utilization are the future solutions for industrial waste salt in my country.

[0005] The key to the harmless treatment and resource utilization of waste salt is the removal of toxic organic and inorganic impurities. The harmless treatment method first removes organic and inorganic impurities from the waste salt, and then obtains by-product salt through technologies such as membrane processing, freezing, and evaporation crystallization. Summary of the Invention

[0006] Therefore, this disclosure provides a solid waste salt disposal system and method to solve the problems of resource waste and environmental pollution caused by directly dumping and landfilling waste salt.

[0007] To achieve the above objectives, the embodiments of this disclosure provide the following technical solutions: In a first aspect of the embodiments of this disclosure, a solid waste salt disposal system is provided, the system comprising: The pyrolysis system includes a two-stage thermal kiln system, a cooling kiln, and a hot air system connected in series. Waste salt is pyrolyzed by progressively increasing and then decreasing the temperature. The hot air system is introduced in reverse into the second stage of the two-stage thermal kiln system, and then passes through the first stage to form pyrolysis flue gas. This pyrolysis flue gas enters the flue gas treatment system. The material from the two-stage thermal kiln system is discharged through a screw conveyor into the analysis tank of the salt dissolving and separating system. Flue gas treatment system: includes a secondary combustion chamber, waste heat boiler, quench tower, bag filter, waste acid recovery unit and water washing unit connected in sequence. The water washing unit is connected to an external water supply system. The secondary thermal kiln system includes a primary kiln and a secondary kiln connected in series. The primary kiln includes a pyrolysis chamber and a combustion chamber. The material outlet of the pyrolysis chamber is connected to the feed inlet of the secondary kiln. The combustion chamber is a heat exchange zone for heating and is connected to external natural gas and combustion-supporting gas. The tail end is connected to an exhaust stack. The hot air system includes a rotary kiln hot air furnace. The outlet of the rotary kiln hot air furnace is connected to the material outlet side sealing cover of the secondary kiln. The feed end of the primary kiln is provided with a flue gas outlet, which is connected to the flue gas treatment system.

[0008] Furthermore, the pyrolysis system includes a high-level silo, which is connected to the feed inlet of a primary kiln via a feed screw conveyor. The discharge outlet of the primary kiln is connected to the feed inlet of a secondary kiln, and the discharge outlet of the secondary kiln is connected to the feed inlet of a cooling kiln. The discharge outlet of the cooling kiln is connected to the salt dissolving and separating system via a discharge screw conveyor. The air outlet of the rotary kiln hot blast stove is connected to the discharge port side sealing cover of the second-stage kiln, and the feed end of the first-stage kiln is provided with a flue gas outlet, which is connected to the flue gas treatment system; The combustion chamber of the first-stage kiln is provided with a furnace flue gas outlet, which is connected to an exhaust stack.

[0009] Furthermore, a flue is provided between the kiln head of the second-stage kiln and the kiln tail of the first-stage kiln, and a cyclone dust collector is provided at the flue gas outlet of the kiln head of the first-stage kiln. The exhaust port of the cyclone dust collector is connected to the flue gas treatment system, and the solid discharge port of the cyclone dust collector is connected to a ton bag to collect solid particles.

[0010] Furthermore, a hot air heat exchanger is provided between the flue gas outlet of the furnace and the exhaust stack of the first-stage kiln. The hot air heat exchanger is connected to an external combustion-supporting pipeline, which is connected to the combustion port of the combustion chamber of the first-stage kiln.

[0011] Furthermore, the flue gas treatment system includes a secondary combustion chamber, the flue gas outlet of which is connected to the inlet of a waste heat boiler, the material outlet of which is connected to an ash collection system, a urea spray system for primary cleaning of the waste heat boiler, a flue gas outlet of which is connected to a quench tower, a flue gas outlet of which is connected to a bag filter, a quench tower for secondary cleaning via an activated carbon injection system and a baking soda injection system, and a water washing unit for the flue gas outlet of the bag filter.

[0012] Furthermore, the water washing unit includes a graphite cooling composite tower connected to the flue gas outlet of the bag filter. The outlet of the graphite cooling composite tower is connected to the inlet of the water washing tower. The outlet of the water washing tower is connected to an alkaline washing device. The outlet of the alkaline washing device is connected to a chimney. The alkaline washing device includes a primary alkaline washing tower, a secondary alkaline washing tower, and an alkaline liquid tank connected thereto. The outlet of the water washing tower is connected to the inlet of the primary alkaline washing tower. The outlet of the primary alkaline washing tower is connected to the inlet of the secondary alkaline washing tower. The liquid outlet of the graphite cooling composite tower is connected to a waste acid recovery unit. The outlet of the secondary alkaline washing tower is connected to a chimney. The liquid outlet of the secondary alkaline washing tower is connected to the inlet of the primary alkaline washing tower.

[0013] Furthermore, the outlet of the water washing tower is connected to the inlet of the graphite cooling composite tower, the outlet of the graphite cooling composite tower is connected to the waste acid recovery unit, and the outlets of the graphite cooling composite tower, the primary alkaline washing tower, and the secondary alkaline washing tower are all equipped with self-circulating pumps connected to internal sprayers; The alkali tank and the water supply system are respectively connected to the graphite cooling composite tower, the water washing tank, the primary alkali washing tower, and the secondary alkali washing tower.

[0014] Furthermore, the kiln section includes a roller support assembly, which supports the kiln inner cylinder assembly at its front and rear ends via roller assemblies, and drives the kiln inner cylinder assembly to rotate via a rotation drive assembly. An outer kiln cylinder assembly is located outside the middle section of the kiln inner cylinder assembly. A combustion chamber is formed between the kiln inner cylinder assembly and the outer cylinder assembly. The interior of the kiln inner cylinder assembly is a pyrolysis chamber. Multiple weir plates are provided within the combustion chamber, dividing it into multiple cavities. Each cavity has uniformly distributed annular burners on its exterior, connected to an external air supply port. The kiln inner cylinder assembly is equipped with L-shaped turning plates evenly distributed in a ring along the inside of the vessel, with their open surfaces facing the kiln rotation direction. The kiln inner cylinder assembly is also equipped with a kiln head impeller. The kiln head impeller includes a fixing ring fixed to the inner wall of the kiln inner cylinder assembly. The fixing ring has multiple intersecting bends, each containing a steel ball. The bends include a bent portion and a straight portion, with the bent portion close to and connected to the fixing ring.

[0015] In a second aspect of the embodiments of this disclosure, a solid waste salt disposal system and method are provided. The method is applied to the system described in any of the above claims and includes the following steps: Primary pyrolysis of waste salt: After pre-drying, the waste salt enters a high-level silo and is conveyed into a primary kiln via a screw conveyor at the bottom of the silo. The first 6 meters of the primary kiln are made of composite plates of carbon steel and Hastelloy, with the temperature controlled below 350℃. The last 12 meters are made of 310s material, with the temperature controlled at 550℃. The waste salt is discharged from the tail of the primary kiln into the secondary kiln. The discharge temperature of the primary kiln is approximately 550℃. Secondary pyrolysis of waste salt: After entering the second-stage kiln, the material is heated for one hour, with the temperature increasing from 550℃ to 650℃. Finally, the material is fed into a cooling kiln for cooling, where it is cooled from 650℃ to 80℃ using water cooling. The material then exits the cooling kiln through a screw conveyor into the analysis tank of the salt-dissolving and separating system. Simultaneously, the rotary kiln hot blast stove is activated, generating 700℃ hot air, which enters from the tail end of the second-stage kiln, fully exchanging heat with the material. The air exits from the feed end of the second-stage kiln and enters the tail end of the first-stage kiln, where it fully exchanges heat with the material, reducing the temperature to 250~300℃. Flue gas calcination and purification: The flue gas enters the secondary combustion chamber for further combustion, reaching a temperature above 1100℃. It then passes through a waste heat boiler to recover waste heat, reducing the temperature to approximately 550℃. The waste heat boiler is equipped with an SNCR denitrification device, which can be supplemented with urea for denitrification. The flue gas exiting the waste heat boiler is cooled to below 200℃ via a quench tower. Residual dioxins and sulfur dioxide are further removed by injecting activated carbon and baking soda into the pipeline. Particulate matter from the reaction is captured by a bag filter. The flue gas then enters a spray system. An emergency discharge port is located at the top of the secondary combustion chamber, and a slag discharge port is located at the bottom. The steam generated by the waste heat boiler is sent to the salt dissolving and separation system after passing through a steam distribution cylinder. Gas washing and exhaust: The flue gas after dust removal by the bag filter enters the graphite cooling composite tower, where it is cooled to 80°C and absorbs acidic gases. It then enters the water washing tower for further absorption of residual acidic gases. In the graphite cooling composite tower, sprayed water comes into full contact with the flue gas, absorbing most of the acidic gases. When the concentration of waste acid in the spray liquid reaches a certain value, it is pumped to the waste acid tank and finally discharged from the system. After that, the flue gas enters the two-stage alkaline washing tower, where liquid alkali is added to thoroughly remove the acidic gases. Finally, it is led to the chimney for exhaust by a fan.

[0016] Furthermore, the combustion chamber of the first-stage kiln is heated by natural gas to generate furnace flue gas at a temperature of 400~500℃. The flue gas is cooled by the hot air heat exchanger of the first-stage kiln and then led to the exhaust stack for venting. The combustion air of the first-stage kiln is preheated before entering the burner for combustion. The hot air stove directly uses ambient temperature air for combustion.

[0017] According to the embodiments of this disclosure, the system has the following advantages: This system includes a pyrolysis system and a flue gas treatment system. Through secondary pyrolysis of waste salt and simultaneous reverse hot air supply, harmful substances in the waste salt are separated from the solid to form flue gas. Through the flue gas purification process, waste salt is recovered and harmful substances are decomposed, achieving the goal of harmlessness. The first-stage kiln adopts an external heating structure, while the second-stage kiln adopts an internal heating structure. This combination of internal and external heating methods can cope with the complex working conditions of waste salt and is more inclusive of waste salt components. The combination of internal and external heating methods increases the residence time of waste salt in the kiln, effectively improving the removal rate of organic matter in the waste salt, reducing the TOC content of the salt exiting the kiln, and optimizing the intermediate process unit of the sodium chloride waste salt entering the pyrolysis-fed ion-exchange membrane caustic soda process. The cooling kiln uses circulating cooling water to indirectly cool the pyrolyzed salt, recovering heat from the salt and ensuring full recovery of waste heat. The 80°C water after heat exchange can be used for the hot water system in the workshop. During the flue gas purification process, acidic gases can be absorbed by spraying through a graphite cooling composite tower, and the by-product waste acid can be used at other acid-using points. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which this disclosure can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effectiveness and purpose that this disclosure can achieve, should still fall within the scope of the technical content disclosed herein.

[0020] Figure 1 This is a system block diagram illustrating a solid waste salt disposal system according to an exemplary embodiment; Figure 2 This is a schematic diagram of a pyrolysis system in a solid waste salt disposal system according to an exemplary embodiment. Figure 3 This is a schematic diagram of a flue gas treatment system in a solid waste salt disposal system according to an exemplary embodiment. Figure 4 This is a front view of a section kiln in a solid waste salt treatment system according to an exemplary embodiment. Figure 5 for Figure 4 Sectional view along line A; Figure 6 for Figure 4 Sectional view along line B Figure 7 A front view of a flipper plate according to an exemplary embodiment. Figure 8 A bottom view of a flipper plate according to an exemplary embodiment; Figure 9 This is a flowchart illustrating a solid waste salt disposal method according to an exemplary embodiment.

[0021] In the diagram: 101, Roller support assembly; 102, Roller assembly; 103, Kiln inner cylinder assembly; 104, Rotary drive assembly; 105, Kiln outer cylinder assembly; 106, Weir plate; 107, Tilting plate; 1071, Vertical plate; 1072, Horizontal plate; 1073, Folded edge; 108, Kiln head impeller; 109, Fixing ring; 110, Bend; 111, Steel ball; 112, Pyrolysis chamber; 113, Combustion chamber. Detailed Implementation

[0022] The following specific embodiments illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0023] The terms "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity of description and are not intended to limit the scope of this disclosure. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of this disclosure.

[0024] The main methods for treating industrial waste salt are stockpiling or landfilling, which have drawbacks such as wasting space and land, and reducing land utilization. In particular, when salt and its impurities are lost, it can cause serious harm such as soil salinization and environmental pollution.

[0025] Commonly used waste salt treatment methods primarily employ dissolution separation, which generally requires integration with MVR (Mechanical Vapor Reduction) evaporation systems. MVR evaporation systems are complex in layout and relatively expensive, suitable for large-scale waste salt treatment; small-scale chemical plants often struggle to afford the substantial construction and maintenance costs. Washing, another method for treating waste salt, separates components based on their varying solubility in solvents. This method is suitable for waste salt with simple compositions and few impurities, but it leaves some residual impurities, limiting the resource utilization of the waste salt. Furthermore, excessive solvent usage and the generation of concentrated solutions lead to resource waste and secondary pollution. Additionally, existing flue gas purification methods typically employ direct gas washing. Direct gas washing results in incomplete removal of harmful substances from solid materials, requiring repeated operations and significantly increasing external resource costs.

[0026] The present invention aims to provide a miniaturized system for removing toxic organic and inorganic impurities from waste salt, so as to meet the requirements of thoroughly removing harmful substances from waste salt and recycling waste salt.

[0027] like Figure 1 As shown, the solid waste salt disposal system of the present invention includes a pyrolysis system and a flue gas treatment system. Through secondary pyrolysis of waste salt and simultaneous reverse hot air supply, harmful substances in the waste salt are separated from the solid to form flue gas. Through the flue gas purification process, waste salt is recycled and harmful substances are decomposed to achieve the purpose of harmlessness.

[0028] like Figure 2 As shown, this is the system structure of the pyrolysis system in this invention: it includes a two-stage thermal kiln system and a hot air system connected in series. The waste salt is pyrolyzed by gradually increasing the temperature and then decreasing it. The hot air system is introduced into the second stage kiln of the two-stage thermal kiln system in reverse, and then passes through the first stage kiln to form pyrolysis flue gas. The pyrolysis flue gas enters the flue gas treatment system. The material of the two-stage thermal kiln system enters the analysis tank of the salt dissolving and separating system through a screw discharge. The secondary thermal kiln system includes a first-stage kiln and a second-stage kiln connected in series. The first-stage kiln includes a pyrolysis chamber 112 and a combustion chamber 113. The material outlet of the pyrolysis chamber 112 is connected to the feed inlet of the second-stage kiln. The combustion chamber 113 is used for heat exchange zone heating and is connected to external natural gas and combustion-supporting gas. The tail end is connected to an exhaust stack. The hot air system includes a rotary kiln hot air furnace. The outlet of the rotary kiln hot air furnace is connected to the material outlet side sealing cover of the second-stage kiln. The feed end of the first-stage kiln is provided with a flue gas outlet, which is connected to a flue gas treatment system.

[0029] In the specific structure, the pyrolysis system includes a high-level silo, which is connected to the feed inlet of the first-stage kiln via a feed screw conveyor and is connected to the pyrolysis chamber 112. The discharge outlet of the first-stage kiln is connected to the feed inlet of the second-stage kiln, and the discharge outlet of the second-stage kiln is connected to the feed inlet of the cooling kiln. The discharge outlet of the cooling kiln is connected to the salt dissolving and separating system via a discharge screw conveyor. The combustion chamber 113 of the first-stage kiln is connected to a natural gas system, which heats the material in the pyrolysis chamber 112 by using natural gas.

[0030] The air outlet of the rotary kiln hot blast stove is connected to the kiln tail (discharge port end) of the second-stage kiln. The rotary kiln hot blast stove is fueled by a natural gas system and equipped with a combustion fan. The kiln head (feed port end) of the first-stage kiln is equipped with a flue gas outlet, which is connected to a flue gas treatment system. This device allows hot air generated by the hot blast stove to directly enter the second-stage kiln, and then the first-stage kiln, creating a reverse flow with the material. This further pyrolyzes the material into flue gas, improving pyrolysis efficiency and overall effectiveness. The first-stage kiln uses an external heating structure, while the second-stage kiln uses an internal heating structure. This combination of internal and external heating methods can handle more complex operating conditions and is more tolerant of waste salt components. During flue gas purification, acidic gases can be absorbed by spraying through a graphite cooling composite tower, and the byproduct waste acid can be used at other acid-using points.

[0031] A cyclone dust collector is installed at the flue gas outlet of the kiln head. The exhaust port of the cyclone dust collector is connected to the flue gas treatment system, and the solid discharge port of the cyclone dust collector is connected to a ton bag to collect solid particles.

[0032] The combustion chamber 113 of the first-stage kiln is equipped with a furnace flue gas outlet, which is connected to a hot air heat exchanger. The hot air heat exchanger is connected to an external exhaust stack and provides combustion air to the combustion chamber 113 of the first-stage kiln. The hot air heat exchanger is connected to an external combustion gas pipeline, which is connected to the combustion port of the combustion chamber 113 of the first-stage kiln. By setting up a hot air heat exchanger, the high-temperature furnace flue gas is used to exchange heat with the external combustion gas, avoiding cold air from directly entering the high-temperature combustion chamber 113, which would directly reduce the temperature of the combustion chamber 113 and affect the pyrolysis effect of the material. At the same time, it prevents the high-temperature furnace body from directly contacting the low-temperature combustion gas and causing it to crack.

[0033] like Figure 3 As shown, this is the flue gas treatment system of the present invention: it includes a secondary combustion chamber, a waste heat boiler, a quench tower, a bag filter, a waste acid recovery unit, and a water washing unit connected in sequence. The water washing unit is connected to an external water supply system. The flue gas treatment system includes a secondary combustion chamber. The flue gas outlet of the secondary combustion chamber is connected to the inlet of the waste heat boiler. The material outlet of the secondary combustion chamber is connected to the ash and slag collection system. A urea SNCR system is introduced into the waste heat boiler for denitrification. The flue gas outlet of the waste heat boiler is connected to a quench tower. The flue gas outlet of the quench tower is connected to a bag filter. The quench tower is connected to an activated carbon injection system and a sodium bicarbonate injection system. The flue gas outlet of the bag filter is connected to a water washing unit.

[0034] The water washing unit includes a graphite cooling composite tower connected to the flue gas outlet of a bag filter. The outlet of the graphite cooling composite tower is connected to the inlet of the water washing tower, and the outlet of the water washing tower is connected to an alkaline washing device. The outlet of the alkaline washing device is connected to a chimney. The alkaline washing device includes a primary alkaline washing tower and a secondary alkaline washing tower, and an alkaline solution tank connected to them. The outlet of the water washing tower is connected to the inlet of the primary alkaline washing tower, and the outlet of the primary alkaline washing tower is connected to the inlet of the secondary alkaline washing tower. The outlet of the graphite cooling composite tower is connected to a waste acid recovery unit, and the outlet of the secondary alkaline washing tower is connected to the chimney. The outlet of the secondary alkaline washing tower is connected to the inlet of the primary alkaline washing tower. The combination of the graphite cooling composite tower, the water washing tower, and the two-stage alkaline washing tower can recover some waste acid and effectively remove acidic gases from the flue gas. Simultaneously, the recovery of waste acid reduces the consumption of alkaline solution, thus lowering the system's operating costs.

[0035] The graphite cooling composite tower not only recovers waste acid but also provides a good cooling effect, reducing the temperature resistance requirements for the subsequent spray tower material selection. The outlet of the water washing tower is connected to the inlet of the graphite cooling composite tower, and the outlet of the graphite cooling composite tower is connected to the waste acid recovery unit. The outlets of the graphite cooling composite tower, the primary alkaline washing tower, and the secondary alkaline washing tower are all equipped with self-circulating pumps, which are connected to the internal sprayers.

[0036] The water supply system connects to the graphite cooling composite tower, water washing tank, primary alkaline washing tower, and secondary alkaline washing tower, while the alkaline solution tank connects to both the primary and secondary alkaline washing towers. Each branch pipe of the water supply system is equipped with an automatic valve to control the water supply volume. This configuration offers a higher degree of automation and reduces manual operation costs. This device provides more efficient air washing. In the actual alkaline solution to water ratio, the alkaline solution concentration in the primary and secondary alkaline washing towers increases sequentially. The alkaline solution concentration is adjusted according to the equipment location, operating temperature, and working status to ensure saturation, maximizing complete neutralization and preventing excessive concentration from creating new pollution sources.

[0037] like Figure 4-8As shown, a section of the kiln includes a roller support assembly 101. The front and rear of the roller support assembly 101 are supported by roller assemblies 102, which in turn support the kiln inner cylinder assembly 103. The inner cylinder assembly is rotated by a rotation drive assembly 104. The middle section of the inner cylinder assembly 103 is provided with an outer cylinder assembly 105. A combustion chamber 113 is formed between the inner cylinder assembly 103 and the outer cylinder assembly. The interior of the inner cylinder assembly 103 is a pyrolysis chamber 112. The combustion chamber 113 is provided with multiple weir plates 106, which divide the combustion chamber 113 into multiple cavities. Each cavity is provided with a ring of evenly distributed burners on the outside, which are connected to an external air supply port. Two sets of cleaning chains are arranged in the 1.5m area in front of the first kiln shell. The weir plate 106 inside the first kiln jacket (combustion chamber 113) divides the inner part of the shell into multiple cavities, which can be divided into different combustion chamber 113 temperature zones. The first kiln, the second kiln and the cooling kiln are all equipped with tilt angle adjustment devices and shims in the overall frame structure. The angled kiln body installation form is conducive to the rapid transportation of materials.

[0038] The kiln inner cylinder assembly 103 is provided with a circularly distributed material-turning plate 107 along the inside of the vessel. The material-turning plate 107 is L-shaped, with its open surface facing the kiln rotation direction. The kiln inner cylinder assembly 103 is also provided with a kiln head impeller 108, and a material-draining component is provided at the tail end of the kiln head impeller 108. The turning plate 107 includes a vertical plate. The bottom of the vertical plate 1071 is fixed to the inner wall of the kiln inner cylinder assembly 103 by an angle iron connector (not shown). The top of the vertical plate 1071 is bent to form a horizontal plate 1072 with a folded edge 1073. The folded edge 1073 is open and faces the kiln rotation direction.

[0039] The kiln features a frequency converter motor with adjustable speed control. The kiln has an integral frame structure and is equipped with an tilt angle adjustment device. The roasting residence time of the material can be adjusted by changing the speed and tilt angle to ensure sufficient roasting of relevant components. During installation, the cylinder is typically tilted at a 0.5-1° angle to ensure material flowability. When the cylinder is long, a weir plate 106 is installed internally to divide the cylinder into multiple cavities to ensure uniform filling rate and material residence time. The use of a tipping plate 107 reduces material wear while increasing the heat transfer area between the cylinder and the material, enhancing the flow and heat transfer effect between materials, and ensuring uniform heating of the material.

[0040] In this example, the size of the turning plate 107 gradually increases from the kiln head to the kiln tail, mainly due to the increased width of the vertical plate 1071. The purpose is that the material at the kiln head has high moisture content and requires dense turning, while the material at the kiln tail has a high degree of drying after pyrolysis and can be directly turned over and transported outward on a large scale, thereby improving the pyrolysis efficiency of the material. At the same time, combined with the combustion temperature of different areas of the combustion chamber 113, the pyrolysis efficiency is further accelerated.

[0041] The kiln head impeller 108 includes a fixing ring 109 fixed to the inner wall of the kiln inner cylinder assembly 103. The fixing ring 109 has multiple intersecting bends 110. Each bend 110 contains a steel ball 111. The bend 110 includes a bent part and a straight part. The bent part is close to and connected to the fixing ring 109, which enables the steel ball 111 to roll along the inside of the bend 110. By vibrating and striking the inner wall of the kiln inner cylinder assembly 103, the bend can clean up the ringed waste salt and make it fall off. The bending direction of the bend 110 is opposite to the kiln rotation direction.

[0042] In a second aspect of the embodiments of this disclosure, a solid waste salt disposal system and method are provided. The method is applied to any of the systems described above. Waste salt enters the primary kiln pyrolysis furnace through a spiral feed inlet of a hood. Inside the kiln, the waste salt is heated by burners and evenly lifted by rotating lifting plates within the kiln body, forming a counter-current with the exhaust gas from the secondary kiln. Finally, it enters the feed inlet of the secondary kiln feed hood through the discharge outlet. The waste salt continues to be heated within the secondary kiln to remove organic matter (COD), and is then evenly lifted by the rotating lifting plates within the kiln body. The hot air flows in a countercurrent with the heating gas from the hot air inlet of the second-stage kiln's discharge hood. The hot air carries away the carbonized organic matter and moisture into the first-stage kiln, and the waste salt is finally discharged from the discharge hood and enters the cooling kiln for cooling. The detoxified waste salt enters the kiln body through the inlet of the cooling kiln's feed hood, and after being cooled by the cooling circulating water on the outer wall of the jacket, it is discharged from the system through the discharge hood's discharge outlet. In the heating section of the kiln, the waste salt's moisture is vaporized and its small-molecule organic matter is carbonized. The high-temperature waste gas generated by the waste salt's heating is discharged through the flue gas outlet. The first-stage kiln is an externally heated type, while the second-stage kiln is an internally heated type.

[0043] The core advantage of a cooling kiln is that it can achieve continuous and uniform cooling of materials, while adapting to high-temperature and high-volume industrial scenarios, ensuring the stability of subsequent processing.

[0044] It can be directly connected to high-temperature calcination equipment (such as rotary kilns) to form a continuous "calcination-cooling" process, reducing intermediate transfer links and improving overall production efficiency.

[0045] After carbonization, the salt discharge temperature is >100℃, and after passing through the cooling kiln, it is <60℃. When it enters the next stage and comes into contact with water, the amount of water vapor generated can be reduced, thereby protecting the on-site operating environment. It can also be used for direct ton bag packaging. The water after heat exchange can be used for waste heat recovery.

[0046] like Figure 9 As shown, the method includes the following steps: Primary pyrolysis of waste salt: The pyrolysis feed must have a moisture content of 3-5% and a particle size of less than 2mm. After pre-drying, the waste salt enters a high-level silo and is conveyed to the primary kiln via a screw conveyor at the bottom of the silo. The first 6m of the primary kiln is made of composite plates of carbon steel and Hastelloy, with the temperature controlled below 350℃. The last 12m is made of 310s material, with the temperature controlled at 550℃. The waste salt is discharged from the tail of the primary kiln into the secondary kiln. The discharge temperature of the primary kiln is approximately 550℃. Secondary pyrolysis of waste salt: After entering the second-stage kiln, the material is heated for one hour, with the temperature increasing from 550℃ to 650℃. Finally, the material is fed into a cooling kiln for cooling, where it is cooled from 650℃ to 80℃ using water cooling. The material then exits the cooling kiln via a screw conveyor into the analysis tank of the salt-dissolving and separating system. Simultaneously, a hot blast furnace is activated, generating 700℃ hot air, which enters from the tail end of the second-stage kiln, fully exchanging heat with the material. The hot air exits from the feed end of the second-stage kiln and enters the tail end of the first-stage kiln, where it also fully exchanges heat with the material, reducing the temperature to 250~300℃. Flue gas purification: The flue gas enters the secondary combustion chamber for further combustion, reaching a temperature above 1100℃. It then passes through a waste heat boiler to recover waste heat, reducing the temperature to approximately 550℃. The waste heat boiler is equipped with an SNCR denitrification device, which injects urea into the boiler for denitrification. The flue gas exiting the waste heat boiler is cooled to below 200℃ via a quench tower. Residual dioxins and sulfur dioxide are further removed by injecting activated carbon and baking soda into the pipeline. Particulate matter from the reaction is captured by a bag filter. The flue gas then enters a spray system. An emergency discharge port is located at the top of the secondary combustion chamber, and a slag discharge port is located at the bottom. The steam generated by the waste heat boiler is sent to the salt dissolving and separation system after passing through a steam distribution cylinder. Gas washing and exhaust: The flue gas after dust removal by the bag filter enters the graphite cooling composite tower, where it is cooled to 80°C and absorbs acidic gases. It then enters the water washing tower for further absorption of residual acidic gases. In the graphite cooling composite tower, sprayed water comes into full contact with the flue gas, absorbing most of the acidic gases. When the concentration of waste acid in the spray liquid reaches a certain value, it is pumped to the waste acid tank and finally discharged from the system. After that, the flue gas enters the two-stage alkaline washing tower, where liquid alkali is added to thoroughly remove the acidic gases. Finally, it is led to the chimney for exhaust by a fan.

[0047] The heat from the high-temperature flue gas generated in the combustion chamber 113 can be recovered through a hot air heat exchanger and used for preheating the combustion air, thereby saving natural gas. Specifically, the combustion chamber 113 of the first-stage kiln generates furnace flue gas at a temperature of 400-500℃ through natural gas heating. This flue gas is cooled by the first-stage kiln hot air heat exchanger and then discharged through the exhaust stack. The combustion air of the first-stage kiln, after preheating, enters the burners for combustion, while the hot blast stove directly uses ambient temperature air for combustion.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0049] Although the present disclosure has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of the present disclosure are all within the scope of protection claimed by the present disclosure.

Claims

1. A solid waste salt disposal system, characterized in that... The system includes The pyrolysis system includes a two-stage thermal kiln system, a cooling kiln, and a hot air system connected in series. Waste salt is pyrolyzed by progressively increasing and then decreasing the temperature. The hot air system is introduced in reverse into the second stage of the two-stage thermal kiln system, and then passes through the first stage to form pyrolysis flue gas. This pyrolysis flue gas enters the flue gas treatment system. The material from the two-stage thermal kiln system is discharged through a screw conveyor into the analysis tank of the salt dissolving and separating system. Flue gas treatment system: includes a secondary combustion chamber, waste heat boiler, quench tower, bag filter, waste acid recovery unit and water washing unit connected in sequence. The water washing unit is connected to an external water supply system. The secondary thermal kiln system includes a first-stage kiln, a second-stage kiln, and a cooling kiln connected in series. The first-stage kiln includes a pyrolysis chamber and a combustion chamber. The material outlet of the pyrolysis chamber is connected to the feed inlet of the second-stage kiln. The combustion chamber is a heat exchange zone for heating and is connected to external natural gas and combustion-supporting gas. The tail end is connected to an exhaust stack. The hot air system includes a rotary kiln hot air furnace. The outlet of the rotary kiln hot air furnace is connected to the material outlet side sealing cover of the second-stage kiln. The feed end of the first-stage kiln is provided with a flue gas outlet, which is connected to the flue gas treatment system.

2. The solid waste salt disposal system according to claim 1, characterized in that... The pyrolysis system includes a high-level silo, which is connected to the feed inlet of a primary kiln via a feed screw conveyor. The discharge outlet of the primary kiln is connected to the feed inlet of a secondary kiln, and the discharge outlet of the secondary kiln is connected to the feed inlet of a cooling kiln. The discharge outlet of the cooling kiln is connected to the salt dissolving and separating system via a discharge screw conveyor. The air outlet of the rotary kiln hot blast stove is connected to the discharge port side sealing cover of the second-stage kiln, and the feed end of the first-stage kiln is provided with a flue gas outlet, which is connected to the flue gas treatment system; The combustion chamber of the first-stage kiln is provided with a furnace flue gas outlet, which is connected to an exhaust stack.

3. The solid waste salt disposal system according to claim 2, characterized in that... A flue is provided between the kiln head of the second-stage kiln and the kiln tail of the first-stage kiln. A cyclone dust collector is provided at the flue gas outlet of the kiln head of the first-stage kiln. The exhaust port of the cyclone dust collector is connected to the flue gas treatment system. The solid discharge port of the cyclone dust collector is connected to a ton bag to collect solid particles.

4. The solid waste salt disposal system according to claim 3, characterized in that... A hot air heat exchanger is provided between the flue gas outlet of the furnace and the exhaust stack of the first-stage kiln. The hot air heat exchanger is connected to an external combustion-supporting pipeline, which is connected to the combustion port of the combustion chamber of the first-stage kiln.

5. The solid waste salt disposal system according to claim 1, characterized in that... The flue gas treatment system includes a secondary combustion chamber. The flue gas outlet of the secondary combustion chamber is connected to the inlet of a waste heat boiler. The material outlet of the secondary combustion chamber is connected to an ash and slag collection system. A urea spraying system is introduced into the waste heat boiler. The flue gas outlet of the waste heat boiler is connected to a quench tower. The flue gas outlet of the quench tower is connected to a bag filter. The quench tower is connected to an activated carbon injection system and a sodium bicarbonate injection system. The flue gas outlet of the bag filter is connected to a water washing unit.

6. The solid waste salt disposal system according to claim 5, characterized in that... The water washing unit includes a graphite cooling composite tower connected to the flue gas outlet of a bag filter. The outlet of the graphite cooling composite tower is connected to the inlet of the water washing tower. The outlet of the water washing tower is connected to an alkaline washing device. The outlet of the alkaline washing device is connected to a chimney. The alkaline washing device includes a primary alkaline washing tower, a secondary alkaline washing tower, and an alkaline liquid tank connected thereto. The outlet of the water washing tower is connected to the inlet of the primary alkaline washing tower. The outlet of the primary alkaline washing tower is connected to the inlet of the secondary alkaline washing tower. The liquid outlet of the graphite cooling composite tower is connected to a waste acid recovery unit. The outlet of the secondary alkaline washing tower is connected to a chimney. The liquid outlet of the secondary alkaline washing tower is connected to the inlet of the primary alkaline washing tower.

7. The solid waste salt disposal system according to claim 6, characterized in that... The outlet of the water washing tower is connected to the inlet of the graphite cooling composite tower, and the outlet of the graphite cooling composite tower is connected to the waste acid recovery unit. The outlets of the graphite cooling composite tower, the primary alkaline washing tower, and the secondary alkaline washing tower are all equipped with self-circulating pumps connected to internal sprayers. The alkali tank and the water supply system are respectively connected to the graphite cooling composite tower, the water washing tank, the primary alkali washing tower, and the secondary alkali washing tower.

8. The solid waste salt disposal system according to claim 7, characterized in that... The kiln section includes a roller support assembly. The front and rear of the roller support assembly support the kiln inner cylinder assembly through roller assemblies, and the kiln inner cylinder assembly is driven to rotate by a rotation drive assembly. The middle section of the kiln inner cylinder assembly is provided with a kiln outer cylinder assembly. The top of the kiln outer cylinder assembly is provided with an air outlet. A combustion chamber is formed between the kiln inner cylinder assembly and the outer cylinder assembly. The interior of the kiln inner cylinder assembly is a pyrolysis chamber. The combustion chamber is provided with multiple weir plates, which divide the combustion chamber into multiple cavities. Each cavity is provided with a ring of evenly distributed burners on its exterior, which are connected to an external air supply port. The kiln inner cylinder assembly is provided with a ring of evenly distributed turning plates along the inside of the vessel. The turning plates are L-shaped with their open surfaces facing the kiln rotation direction. The kiln inner cylinder assembly is also provided with a kiln head impeller, and a material unloading assembly is provided at the tail end of the kiln head impeller. The kiln head impeller includes a fixing ring fixed to the inner wall of the kiln inner cylinder assembly. The fixing ring has multiple intersecting bends, each containing a steel ball. The bends include a bent portion and a straight portion, with the bent portion close to and connected to the fixing ring.

9. A method for disposing of solid waste salt, wherein the method is applied to the system described in any one of claims 1-8, characterized in that... The method includes the following steps: Primary pyrolysis of waste salt: After pre-drying, the waste salt enters a high-level silo and is conveyed into a primary kiln via a screw conveyor at the bottom of the silo. The first 6 meters of the primary kiln are made of composite plates of carbon steel and Hastelloy, with the temperature controlled below 350℃. The last 12 meters are made of 310s material, with the temperature controlled at 550℃. The waste salt is discharged from the tail of the primary kiln into the secondary kiln. The discharge temperature of the primary kiln is approximately 550℃. Secondary pyrolysis of waste salt: After entering the second-stage kiln, the material is heated for one hour, with the temperature rising from 550℃ to 650℃. Finally, the material is fed into a cooling kiln for cooling, where it is cooled from 650℃ to 80℃ using water cooling. The material then exits the cooling kiln through a screw conveyor into the analysis tank of the salt-dissolving and separating system. Simultaneously, the rotary kiln hot blast stove is activated, generating 700℃ hot air, which enters from the tail end of the second-stage kiln, fully exchanging heat with the material. The air exits from the feed end of the second-stage kiln and enters the tail end of the first-stage kiln, where it fully exchanges heat with the material, reducing the temperature to 250~300℃. Flue gas calcination and purification: The flue gas enters the secondary combustion chamber for further combustion, reaching a temperature above 1100℃. It then passes through a waste heat boiler to recover waste heat, reducing the temperature to approximately 550℃. The waste heat boiler is equipped with an SNCR denitrification device, which can be supplemented with urea for denitrification. The flue gas exiting the waste heat boiler is cooled to below 200℃ via a quench tower. Residual dioxins and sulfur dioxide are further removed by injecting activated carbon and baking soda into the pipeline. Particulate matter from the reaction is captured by a bag filter. The flue gas then enters a spray system. An emergency discharge port is located at the top of the secondary combustion chamber, and a slag discharge port is located at the bottom. The steam generated by the waste heat boiler is sent to the salt dissolving and separation system after passing through a steam distribution cylinder. Gas washing and exhaust: The flue gas after dust removal by the bag filter enters the graphite cooling composite tower, where the flue gas is cooled to 80°C and the acidic gases in the flue gas are absorbed. It then enters the water washing tower, where the residual acidic gases in the flue gas are further absorbed. In the graphite cooling composite tower, the sprayed water comes into full contact with the flue gas and absorbs most of the acidic gases in the flue gas. When the concentration of waste acid in the spray liquid reaches a certain value, it is pumped to the waste acid tank and finally sent out of the system. After that, the flue gas enters the two-stage alkaline washing tower, where liquid alkali is added to completely remove the acidic gases in the flue gas. Finally, it is led to the chimney for exhaust by the fan.

10. The solid waste salt disposal system according to claim 9, characterized in that... The combustion chamber of the first-stage kiln is heated by natural gas to generate furnace flue gas at a temperature of 400-500℃. The flue gas is cooled by the hot air heat exchanger of the first-stage kiln and then led to the exhaust stack for venting. The combustion air of the first-stage kiln is preheated before entering the burner for combustion. The hot air stove directly uses room temperature air for combustion.

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