A countercurrent rotary kiln pyrolysis device and method for solid waste salt

Abstract

The present invention discloses a countercurrent rotary kiln pyrolysis device and method for solid waste salt, which includes a countercurrent rotary kiln pyrolysis furnace, a hot blast stove, a solid waste salt screw feeding device, an auxiliary burner, an auxiliary burner combustion-supporting blower, a pyrolysis blower, a water-cooled screw discharging device, an oxygen content meter and a CO analyzer. The hot blast stove provides hot air with stable and adjustable temperature for the pyrolysis furnace. The solid waste salt undergoes the processes of drying, pyrolysis and gasification in the countercurrent rotary kiln, so as to completely remove the organic pollutants in the waste salt. The present invention adopts the one-step countercurrent rotary kiln pyrolysis technology. The hot blast stove directly heats and precisely controls the pyrolysis temperature of the solid waste salt, significantly improving the heat transfer area and efficiency of the countercurrent rotary kiln pyrolysis furnace, which is beneficial to the large-scale application of the solid waste salt pyrolysis; the pyrolysis blower precisely controls the air volume required for pyrolysis, effectively removing the difficult-to-classify organic substances in the solid waste salt, and improving the material universality and process reliability of the solid waste salt pyrolysis treatment.

Description

Technical Field

[0001] The present invention relates to the field of hazardous waste treatment technologies and equipment, and particularly to a countercurrent rotary kiln pyrolysis device and method for solid waste salt, belonging to the field of waste salt treatment technology. Background Art

[0002] In China, the amount of waste salt generated by the pesticide, pharmaceutical, fine chemical, and coal chemical industries is huge. Solid waste salt containing organic pollutants and heavy metals has characteristics such as being toxic, harmful, and soluble. If not properly disposed of, it is extremely easy to cause groundwater and soil pollution, affecting human health and production and life.

[0003] Traditional solid waste salt treatment mainly has two methods: incineration and landfill. When the content of organic pollutants in solid waste salt is low, a large amount of auxiliary fuel needs to be added to maintain the operating temperature of the incinerator when treating solid waste salt by the incineration method. At the same time, under high-temperature incineration conditions, inorganic salts severely erode the refractory lining of the incinerator; although the rigid landfill method can achieve the isolation of solid waste salt from the environment, it cannot eliminate the pollution characteristics and environmental risks of solid waste salt, and the treatment cost is high. Therefore, neither the incineration method nor the landfill method can well solve the problem of solid waste salt treatment.

[0004] Currently, the pyrolysis method for treating solid waste salt often uses an indirect heat exchange type anaerobic pyrolysis furnace. Due to the small heat exchange area and small processing capacity of the equipment, it cannot meet the demand for large-scale treatment of solid waste salt. At the same time, the operating temperature of the indirect heat exchange type anaerobic pyrolysis furnace is low, and it cannot remove the difficult-to-decompose organic pollutants in the waste salt, resulting in the phenomenon of excessive TOC content of organic substances, affecting subsequent refining and purification and resource utilization. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a countercurrent rotary kiln pyrolysis device and method for solid waste salt, which directly heats the solid waste salt with hot air, significantly increasing the heat transfer area of the pyrolysis furnace and facilitating the improvement of the processing scale of a single set of solid waste salt pyrolysis device. The countercurrent rotary kiln pyrolysis device can automatically and quickly adjust in high-temperature, medium-low temperature modes. At the same time, the device is equipped with a pyrolysis air blower, which can accurately control the air volume required for the pyrolysis of organic pollutants in the waste salt, remove the difficult-to-decompose organic pollutants in the solid waste salt, facilitate the refining and purification after the pyrolysis of the waste salt, and realize the resource recycling of the solid waste salt for use in chemical industries and other fields.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A countercurrent rotary kiln pyrolysis device for solid waste salts, characterized in that it includes a countercurrent rotary kiln pyrolysis furnace, a hot blast stove, a solid waste salt screw feeding device, an auxiliary burner, an auxiliary burner combustion-supporting fan, a pyrolysis fan, a water-cooled screw discharging device, an oxygen content meter and a CO analyzer. The hot blast stove provides hot air with stable and adjustable temperature for the pyrolysis furnace. The solid waste salts enter the countercurrent rotary kiln pyrolysis furnace from the kiln tail and experience the processes of drying, pyrolysis and gasification, thoroughly decomposing and removing the organic pollutants in the solid waste salts. The pyrolysis fan precisely controls the air volume required for the pyrolysis gasification of the organic pollutants in the waste salts.

[0008] Further, the countercurrent rotary kiln pyrolysis furnace comprises a rotary kiln furnace body, a lining refractory material, a kiln tail cover, a kiln head cover, a kiln tail sealing device, a kiln head sealing device, a supporting roller device, a retaining wheel device, a variable frequency drive device and a rotary kiln observation sight glass. The rotary kiln furnace body adopts a horizontal rotating cylindrical structure. The central axis of the rotary kiln furnace body forms an angle of 1-4° with the horizontal. The inner lining of the rotary kiln is corundum-mullite refractory material. The two ends of the rotary kiln furnace body are respectively inserted into the kiln tail cover and the kiln head cover. The connections between the rotary kiln furnace body and the kiln tail cover and the kiln head cover are respectively provided with a kiln tail sealing device and a kiln head sealing device. Both the kiln tail sealing device and the kiln head sealing device adopt a structure of stainless steel fish scales + carbon silicon aluminum fiber + stainless steel fish scales + traction rope. The sealing device makes the air leakage of the countercurrent rotary kiln pyrolysis furnace less than 2%. The kiln tail cover is provided with a solid waste salt feed inlet and a pyrolysis flue gas outlet. The oxygen content meter and the CO analyzer are arranged on the horizontal section of the pyrolysis flue gas outlet pipeline. The kiln head cover is provided with a hot air tangential inlet, a pyrolysis air tangential inlet, a pyrolysis product discharge outlet and a rotary kiln observation sight glass. The supporting roller device is provided with a front supporting roller group and a rear supporting roller group to meet the rotating operation of the rotary kiln under load. The retaining wheel device can prevent the rotary kiln from moving axially and ensure the safe and reliable operation of the countercurrent rotary kiln pyrolysis furnace. The variable frequency drive device can adjust the rotating speed of the rotary kiln to meet the pyrolysis time requirements of different solid waste salts.

[0009] Further, the hot blast stove includes a hot blast stove furnace body, an auxiliary burner and an auxiliary burner combustion-supporting fan. The hot blast stove furnace body adopts a horizontal cylindrical structure. One end of the furnace body is provided with a burner interface, and the other end of the furnace body is provided with a hot air outlet. The auxiliary burner is connected to the burner interface of the hot blast stove. The auxiliary burner combustion-supporting fan provides combustion-supporting air for the auxiliary burner. The auxiliary fuel is supplied to the auxiliary burner through a pipeline.

[0010] Furthermore, the solid waste salt screw feeding device is connected to the solid waste salt feeding port of the tail hood of the countercurrent rotary kiln pyrolysis furnace. The solid waste salt is transported into the countercurrent rotary kiln pyrolysis furnace through the screw feeding device. The hot air outlet of the hot blast stove is connected to the tangential hot air inlet of the head hood of the countercurrent rotary kiln pyrolysis furnace through a pipeline. The hot air rotates and flows into the countercurrent rotary kiln pyrolysis furnace along the circular head hood. The tangential hot air enhances the gas turbulence in the countercurrent rotary kiln pyrolysis furnace and improves the heat transfer efficiency between the hot air and the solid waste salt. The hot blast stove provides heat source for the heating and start-up of the countercurrent rotary kiln pyrolysis furnace for solid waste salt, supplies heat for the pyrolysis of the organic matter contained in the solid waste salt and precisely controls the pyrolysis operation temperature. The air outlet of the pyrolysis blower is connected to the tangential pyrolysis air inlet of the head hood of the countercurrent rotary kiln pyrolysis furnace through a pipeline. The pyrolysis blower controls the air volume required for the pyrolysis of solid waste salt by frequency conversion. The difficult-to-decompose organic matter can be effectively removed, which is beneficial to the refining, purification and resource utilization of the inorganic salts after pyrolysis. The water-cooled screw discharging device is connected to the pyrolysis product discharging port of the head hood of the countercurrent rotary kiln pyrolysis furnace. The inorganic salts after pyrolysis are cooled by the water-cooled screw discharging device and transported out of the furnace.

[0011] Furthermore, temperature transmitters and pressure transmitters are installed on both the tail hood and the head hood of the countercurrent rotary kiln pyrolysis furnace. A temperature transmitter is installed at the pyrolysis product discharging port of the head hood. The frequency conversion drive device adopts a remote control mode. The oxygen analyzer and the CO analyzer have functions of remote data transmission, recording and alarming and participate in the automatic control of the device.

[0012] Furthermore, the auxiliary fuel is provided with a flow transmitter, a flow regulating valve, a flow control loop and a pressure transmitter. The combustion-supporting air is provided with a flow transmitter, a flow regulating valve and a flow control loop. A ratio control loop is set between the auxiliary fuel flow control loop and the combustion-supporting air flow control loop. The combustion-supporting blower of the auxiliary burner is provided with a frequency converter. A temperature transmitter is installed in the middle of the hot blast stove to monitor the operation temperature of the hot blast stove.

[0013] Furthermore, a dual-loop control is set between the operation temperature of the countercurrent rotary kiln pyrolysis furnace and the auxiliary fuel flow of the auxiliary burner of the hot blast stove. The pyrolysis air supplied by the pyrolysis blower is provided with a flow transmitter, a flow regulating valve and a flow control loop. A dual-loop control is set between the oxygen content of the pyrolysis flue gas in the countercurrent rotary kiln pyrolysis furnace and the pyrolysis air flow.

[0014] A solid waste salt countercurrent rotary kiln pyrolysis device, characterized in that: it includes a solid waste salt countercurrent rotary kiln pyrolysis device, and also includes a solid waste salt pretreatment device, a secondary combustion chamber, a waste heat recovery device, a flue gas purification device, an induced draft fan, a chimney, a fly ash collection device, and a sewage treatment device. The discharge port of the pretreatment system is connected to the feed port of the solid waste salt spiral feeding device of the solid waste salt countercurrent rotary kiln pyrolysis device. The flue gas outlet of the solid waste salt countercurrent rotary kiln pyrolysis device is connected to the flue gas inlet of the secondary combustion chamber. The flue gas outlet of the secondary combustion chamber is connected to the flue gas inlet of the waste heat recovery device. The flue gas outlet of the waste heat recovery device is connected to the flue gas inlet of the flue gas purification device. The flue gas outlet of the flue gas purification device is connected to the flue gas inlet of the induced draft fan. The flue gas outlet of the induced draft fan is connected to the chimney inlet, finally realizing the purification treatment and up-to-standard discharge of the pyrolysis flue gas of solid waste salt; the fly ash generated by the waste heat recovery device and the flue gas purification device is landfilled after collection, and the production wastewater of the flue gas purification device is pumped to the sewage treatment device for treatment.

[0015] Furthermore, the flue gas purification device includes an SNCR denitration device, a quenching device, an activated carbon injection device, a dry acid removal device, a bag filter, a wet scrubber, and a GGH flue gas heat exchanger, which are arranged in the high-temperature section of the waste heat recovery device at 850-1100°C. The 1100°C high-temperature flue gas at the outlet of the secondary combustion chamber is connected to the flue gas inlet of the waste heat recovery device. The waste heat recovery device uses a full-membrane wall waste heat boiler to recover waste heat. After waste heat recovery, the flue gas is cooled to 500°C. The SNCR denitration device is arranged in the high-temperature section of the full-membrane wall waste heat boiler at 850°C - 1100°C to achieve flue gas denitration treatment; the flue gas outlet of the waste heat recovery device is connected to the flue gas inlet of the quenching device. The 500°C flue gas enters the quenching device for quenching and cooling treatment, so that the flue gas is quickly cooled to 200°C within 1 second, thereby avoiding the temperature range of 500°C - 200°C for dioxin resynthesis and preventing dioxin resynthesis; the flue gas outlet of the quenching device and the activated carbon outlet of the activated carbon injection device are connected to the flue gas inlet of the dry acid removal device. The dry acid removal device realizes the removal of some acidic gases in the flue gas and the adsorption and removal of dioxin; the flue gas outlet of the dry acid removal device is connected to the flue gas inlet of the bag filter. The bag filter filters and removes particulate matter and most heavy metals in the flue gas; the flue gas outlet of the bag filter is connected to the raw flue gas inlet of the GGH flue gas heat exchanger. The raw flue gas enters the wet scrubber after being cooled by the GGH heat exchange; the raw flue gas outlet of the GGH flue gas heat exchanger is connected to the flue gas inlet of the wet scrubber. The wet scrubber further removes acidic gases in the flue gas; the flue gas outlet of the wet scrubber is connected to the flue gas inlet of the induced draft fan. The purified flue gas after wet acid removal enters the GGH heat exchanger after being pressurized by the induced draft fan; the flue gas outlet of the induced draft fan is connected to the purified flue gas inlet of the GGH heat exchanger. The GGH heat exchanger realizes the heat exchange between the low-temperature purified flue gas after wet acid removal and the high-temperature raw flue gas after bag dust removal; the purified flue gas outlet of the GGH heat exchanger is connected to the flue gas inlet of the chimney. The flue gas is discharged into the atmosphere through the chimney.

[0016] A thermal decomposition method for solid waste salt in a countercurrent rotary kiln, characterized by comprising the following steps:

[0017] Step 1: Classify the solid waste salts from different waste-producing enterprises according to their components;

[0018] Step 2: Conduct chemical analysis on the solid waste salts from different waste-producing enterprises and different batches, detect the water content, organic matter content, volatile chlorine content, sulfur content, and heavy metal items, and establish a disposal characteristic database for solid waste salts to provide basic data for subsequent blending and thermal decomposition operation;

[0019] Step 3: Conduct comprehensive blending on the same type of solid waste salts to homogenize the organic matter content, volatile chlorine content, sulfur content, and heavy metal content of the solid waste salts, determine the thermal decomposition treatment batches and quantities of the solid waste salts, and clarify the thermal decomposition process conditions and operation parameters;

[0020] Step 4: Crush and screen the solid waste salt to remove sundries and mechanical impurities;

[0021] Step 5: Start the flue gas purification device and the induced draft fan;

[0022] Step 6: Start the waste heat recovery device;

[0023] Step 7: Start the hot blast stove to heat up and start the countercurrent rotary kiln pyrolysis furnace;

[0024] Step 8: Start the secondary combustion burner in the secondary combustion chamber and heat up the secondary combustion chamber to 1100 °C;

[0025] Step 9: Start the solid waste salt screw feeding device and the pyrolysis fan, and feed the solid waste salt into the countercurrent rotary kiln pyrolysis furnace. The solid waste salt undergoes drying, low-temperature pyrolysis, and medium-temperature pyrolysis gasification in the countercurrent rotary kiln to remove the organic pollutants contained in the solid waste salt; through the dual-loop control system composed of the temperature transmitter at the tail hood of the countercurrent rotary kiln, the flow transmitter of the auxiliary burner of the hot blast stove, and the flow regulating valve, the pyrolysis temperature of the solid waste salt in the countercurrent rotary kiln is adjusted; through the control system composed of the frequency converter of the pyrolysis fan and the oxygen content meter of the countercurrent rotary kiln, the pyrolysis atmosphere of the solid waste salt in the countercurrent rotary kiln is adjusted, and the oxygen content in the countercurrent rotary kiln is controlled below 1%; through the precise control of the pyrolysis temperature and pyrolysis atmosphere, the pyrolysis efficiency of the solid waste salt in the countercurrent rotary kiln is ensured;

[0026] Step 10: Start the water-cooled screw discharging device to cool and convey the pyrolyzed inorganic salts outside the furnace;

[0027] Step 11: The flue gas generated by the countercurrent rotary kiln pyrolysis furnace undergoes secondary combustion, waste heat recovery, rapid cooling, dry acid removal, bag dust removal, GGH heat exchange, wet scrubbing, and is pressurized by the induced draft fan, and then is discharged into the atmosphere through the chimney.

[0028] Compared with the prior art, the present invention has the following advantages and effects: The countercurrent rotary kiln pyrolysis furnace using direct heat exchange has the hot air supplied by the hot blast stove flowing in opposite directions and directly contacting and exchanging heat with the solid waste salt, increasing the heat transfer area and heat exchange efficiency, improving the pyrolysis treatment efficiency, and realizing the large-scale application of solid waste salt pyrolysis; the pyrolysis fan accurately provides the air required for the pyrolysis of waste salt in the countercurrent rotary kiln, and the difficult-to-decompose organic substances in the solid waste salt are completely removed through pyrolysis gasification, improving the flexibility of the pyrolysis process and the universality of the materials, and solving the problems of complex existing solid waste salt pyrolysis technology, unstable equipment operation, small processing capacity, high energy consumption, and incomplete detoxification; the countercurrent rotary kiln pyrolysis furnace can accurately control the temperature and oxygen under different temperature and atmosphere modes, has strong process reliability, excellent pyrolysis process conditions and operating parameters, and the organic matter content TOC of the pyrolyzed inorganic salts is low, which can meet the pyrolysis resource treatment requirements of solid waste salts with different sources, types, and properties. Brief Description of the Drawings

[0029] Figure 1 Schematic diagram of a countercurrent rotary kiln pyrolysis device for solid waste salt of the present invention

[0030] Figure 2 Schematic diagram of waste heat recovery and waste gas treatment of a countercurrent rotary kiln pyrolysis device for solid waste salt of the present invention

[0031] Description of the drawing reference numerals: 1 - rotary kiln, 2 - kiln tail hood, 3 - kiln head hood, 4 - screw feeding device, 5 - hot blast stove, 6 - pyrolysis fan, 7 - water-cooled screw discharging device, 8 - pyrolysis flue gas outlet, 9 - auxiliary burner, 10 - auxiliary burner combustion-supporting fan. Detailed Description of the Invention

[0032] In order to elaborate in detail on the technical solutions adopted by the present invention to achieve the predetermined technical objectives, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. And, without creative efforts, the technical means or technical features in the embodiments of the present invention can be replaced. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0033] As Figure 1 shown, a countercurrent rotary kiln pyrolysis device for solid waste salt of the present invention includes a rotary kiln 1, a kiln tail hood 2, a kiln head hood 3, a screw feeding device 4, a hot blast stove 5, a pyrolysis fan 6, a water-cooled screw discharging device 7, a pyrolysis flue gas outlet 8, an auxiliary burner 9, an auxiliary burner combustion-supporting fan 10, an oxygen analyzer and a CO analyzer. The hot blast stove 5 provides heating air with stable and adjustable temperature for the rotary kiln 1. The pyrolysis fan 6 provides and precisely controls the air volume for the pyrolysis gasification of solid waste salt in the rotary kiln 1. The solid waste salt enters the rotary kiln 1 from the kiln tail hood 2 through the screw feeding device 4 and undergoes moisture drying, pyrolysis and gasification of organic pollutants, thereby decomposing and removing the organic pollutants contained in the solid waste salt.

[0034] The rotary kiln 1 adopts a horizontal rotating cylindrical structure. The included angle between the central axis of the rotary kiln 1 and the horizontal line is 1 - 4°. The inner lining of the rotary kiln 1 is made of corundum-mullite refractory material. Both ends of the furnace body of the rotary kiln 1 are inserted into the kiln tail hood 2 and the kiln head hood 3 respectively. The connections between the rotary kiln 1 and the kiln tail hood 2 and the kiln head hood 3 are respectively provided with a kiln tail sealing device and a kiln head sealing device. Both the kiln tail sealing device and the kiln head sealing device adopt a structure of stainless steel fish scales + carbon silicon aluminum fiber + stainless steel fish scales + traction rope. The sealing device makes the air leakage rate of the rotary kiln 1 less than 2%. The kiln tail hood 2 is provided with a solid waste salt feed inlet and a pyrolysis flue gas outlet 8. The oxygen analyzer and the CO analyzer are arranged on the horizontal section of the pyrolysis flue gas outlet pipeline. The kiln head hood 3 is provided with a hot air tangential inlet, a pyrolysis air tangential inlet, a pyrolysis product discharge outlet and a rotary kiln observation sight glass. The rotary kiln 1 is provided with a supporting wheel device. The supporting wheel device is provided with a front supporting wheel group and a rear supporting wheel group to meet the rotational requirements of the rotary kiln under load operation. The rotary kiln 1 is provided with a retaining wheel device. The retaining wheel device can prevent the rotary kiln from moving axially and ensure the safe and reliable operation of the countercurrent rotary kiln pyrolysis furnace. The rotary kiln 1 is provided with a variable frequency drive device. The variable frequency drive device can adjust the rotational speed of the rotary kiln to meet the pyrolysis time requirements of different solid waste salts.

[0035] The hot blast stove 5 adopts a horizontal cylindrical structure. One end of the hot blast stove 5 is provided with a burner interface, and the other end is provided with a hot air outlet. The auxiliary burner 9 is connected to the burner interface of the hot blast stove 5. The auxiliary burner combustion air blower 10 provides combustion air for the auxiliary burner 9 to use. Natural gas is supplied to the auxiliary burner 9 through a pipeline for use.

[0036] The screw feeding device 4 is connected to the solid waste salt feed inlet of the kiln tail hood 2. The solid waste salt is transported into the rotary kiln 1 through the screw feeding device 4. The hot air outlet of the hot blast stove 5 is connected to the hot air tangential inlet of the kiln head hood 3 through a pipeline. The hot air flows into the rotary kiln 1 along the circular kiln head hood 3 in a rotating manner. The tangential hot air enhances the gas turbulence in the rotary kiln 1 and improves the heat transfer efficiency between the hot air and the solid waste salt. The hot blast stove 5 provides a heat source for the start-up and temperature rise of the rotary kiln 1, supplies heat for the pyrolysis of the organic matter contained in the solid waste salt and precisely controls the pyrolysis operating temperature. The air outlet of the pyrolysis air blower 6 is connected to the pyrolysis air tangential inlet of the kiln head hood 3 through a pipeline. The pyrolysis air blower 6 controls the air volume required for the pyrolysis of the solid waste salt by frequency conversion, fully removes the refractory organic pollutants contained in the solid waste salt, and is beneficial to the subsequent refining and purification of the solid waste salt. The water-cooled screw discharging device 7 is connected to the pyrolysis product discharge outlet of the kiln head hood 3. The pyrolysis products of the solid waste salt are cooled by the water-cooled screw discharging device 7 and transported out of the furnace. The flue gas generated during the pyrolysis process of the solid waste salt enters the secondary combustion chamber, the waste heat recovery device and the flue gas purification device in sequence through the pipeline from the pyrolysis flue gas outlet 8, and is discharged into the atmosphere through the chimney after purification.

[0037] Temperature transmitters and pressure transmitters are installed on both the tail hood 2 and the head hood 3 of the rotary kiln 1. A temperature transmitter is installed at the pyrolysis product discharge port of the head hood 3. The frequency conversion drive device of the rotary kiln 1 adopts a remote control mode. The oxygen analyzer and the CO analyzer have functions of remote data transmission, recording, and alarming and participate in the automatic control of the device.

[0038] Flow transmitters, flow regulating valves, flow control loops, and pressure transmitters are set for the auxiliary fuel of the auxiliary burner 9. Flow transmitters, flow regulating valves, flow control loops, and pressure transmitters are set for the combustion-supporting air of the auxiliary burner 9. A proportional control loop is set between the auxiliary fuel flow control loop and the combustion-supporting air flow control loop of the auxiliary burner 9. A frequency conversion controller is set for the combustion-supporting air blower 10 of the auxiliary burner. A temperature transmitter is installed in the middle of the hot blast stove 5 to monitor the operating temperature of the hot blast stove 5.

[0039] A dual-loop control is set between the measured value of the temperature transmitter of the tail hood 2 of the rotary kiln 1, which is the pyrolysis operating temperature, and the auxiliary fuel flow of the auxiliary burner 9 of the hot blast stove 5. Flow transmitters, flow regulating valves, and flow control loops are set for the pyrolysis air supplied by the pyrolysis blower 6. A dual-loop control is set between the oxygen content of the pyrolysis flue gas of the rotary kiln 1 and the pyrolysis air flow of the pyrolysis blower 6.

[0040] As Figure 2 shown, a solid waste salt countercurrent rotary kiln pyrolysis device of the present invention includes a solid waste salt countercurrent rotary kiln pyrolysis device, and also includes a solid waste salt pretreatment device, a secondary combustion chamber, a waste heat recovery device, a flue gas purification device, an induced draft fan, a chimney, a fly ash collection device, and a sewage treatment device. The discharge port of the pretreatment device is connected to the feed port of the solid waste salt screw feeding device. The flue gas outlet of the solid waste salt countercurrent rotary kiln pyrolysis device is connected to the flue gas inlet of the secondary combustion chamber. The flue gas generated during the pyrolysis process of the solid waste salt is completely burned in the secondary combustion chamber to achieve the complete decomposition of the pyrolysis flue gas. The flue gas outlet of the secondary combustion chamber is connected to the flue gas inlet of the waste heat recovery device. The flue gas outlet of the waste heat recovery device is connected to the flue gas inlet of the flue gas purification device. The flue gas outlet of the flue gas purification device is connected to the flue gas inlet of the induced draft fan. The flue gas outlet of the induced draft fan is connected to the chimney inlet, finally realizing the purification treatment and up-to-standard discharge of the solid waste salt pyrolysis flue gas. The fly ash generated by the waste heat recovery device and the flue gas purification device is landfilled after collection. The production wastewater of the flue gas purification device is pumped to the sewage treatment device for treatment.

[0041] The flue gas purification device includes a waste heat recovery device, an SNCR denitration device installed in the high-temperature section of the waste heat recovery device at 850 - 1100°C, a quenching device, an activated carbon injection device, a dry acid removal device, a bag filter, a wet scrubbing tower, and a GGH flue gas heat exchanger. The 1100°C high-temperature flue gas at the outlet of the secondary combustion chamber is connected to the flue gas inlet of the waste heat recovery device. The waste heat recovery device uses a full-membrane wall waste heat boiler for waste heat recovery. After waste heat recovery, the flue gas temperature drops to 500°C. The SNCR denitration device is installed in the high-temperature section of the full-membrane wall waste heat boiler at 850°C - 1100°C. 10% urea solution is metered and injected into the high-temperature section of the waste heat boiler through a dual-fluid spray gun, so that NO x in the flue gas is selectively non-catalytically reduced to N2, and the SNCR denitration efficiency > 40%; the flue gas outlet of the waste heat recovery device is connected to the flue gas inlet of the quenching device. The flue gas after waste heat recovery enters the quenching device for quenching and cooling treatment. The quenching water is pumped to the dual-fluid spray gun at the top of the quenching tower. The quenching water is atomized into small particle mist water of 30μm by the compressed air of the dual-fluid spray gun and sprayed into the quenching tower, and flows in the same direction as the flue gas entering from the top of the quenching tower. The mist water is completely vaporized into water vapor within 1 second, and the flue gas is quickly cooled to 200°C within 1 second, so that the flue gas avoids the temperature range of 500°C - 200°C for dioxin resynthesis and prevents dioxin resynthesis; the flue gas outlet of the quenching device and the activated carbon outlet of the activated carbon injection device are connected to the flue gas inlet of the dry acid removal device. The acidic gases such as HCl, SO2, and HF in the flue gas react with the slaked lime sprayed by the slaked lime injection device to achieve partial removal of acidic gases, and the acidic gas removal rate > 20%. The powdered activated carbon sprayed by the activated carbon injection device adsorbs and removes dioxins and some volatile heavy metals in the flue gas; the flue gas outlet of the dry acid removal device is connected to the flue gas inlet of the bag filter. The particulate matter in the flue gas is removed due to the interception of the filter bag of the dust collector. Most heavy metals such as lead and cadmium exist in solid form below 300°C and are removed together with the particulate matter by the bag filter. After bag dust removal, the particulate matter content of the flue gas is less than 10mg / m 3, the flue gas outlet temperature of the bag filter is between 170°C and 180°C; to make full use of the flue gas waste heat, the flue gas outlet of the bag filter is connected to the raw flue gas inlet of the GGH flue gas heat exchanger, and heat exchange between the high-temperature flue gas and the wet flue gas is achieved in the GGH heat exchanger, that is, heat exchange between the high-temperature flue gas at the outlet of the bag filter and the low-temperature flue gas at the outlet of the wet scrubbing tower; the raw flue gas outlet of the GGH flue gas heat exchanger is connected to the flue gas inlet of the wet scrubbing tower, and in the wet scrubbing tower, the flue gas contacts the circulating alkali liquid sprayed from the top of the tower countercurrently from bottom to top and undergoes a neutralization reaction, so that most of the acidic gases in the flue gas are removed, and the wet acid removal efficiency can reach 99%. Most of the volatile heavy metals with relatively high saturated vapor pressure exist in the flue gas in gaseous form. During the wet acid removal process, mercury in the flue gas can react with HCl to form HgCl2, and HgCl2 is a water-soluble compound, which reacts with the circulating alkali liquid and is removed; the flue gas outlet of the wet scrubbing tower is connected to the flue gas inlet of the induced draft fan, and the clean flue gas after wet acid removal enters the GGH heat exchanger after being pressurized by the induced draft fan; the flue gas outlet of the induced draft fan is connected to the clean flue gas inlet of the GGH heat exchanger, and the GGH heat exchanger realizes the self-heat exchange between the low-temperature clean flue gas after wet acid removal and the high-temperature raw flue gas after bag dust removal; the clean flue gas outlet of the GGH heat exchanger is connected to the flue gas inlet of the chimney, and the flue gas is discharged into the atmosphere through the chimney.

[0042] A thermal pyrolysis method for solid waste salt in a countercurrent rotary kiln, characterized by comprising the following steps:

[0043] Step 1: Classify the solid waste salts from different waste-producing enterprises according to their components into three categories: solid waste salts with one inorganic salt component, solid waste salts with two inorganic salt components, and solid waste salts with three or more inorganic salt components;

[0044] Step 2: Conduct chemical analysis on the solid waste salts from different waste-producing enterprises and different batches, detect the water content, organic matter content, volatile chlorine content, sulfur content, and heavy metal items, and establish a disposal characteristic database for solid waste salts to provide basic data for subsequent formulation and pyrolysis operation;

[0045] Step 3: Conduct comprehensive formulation on the same type of solid waste salts, equalize the organic matter content, volatile chlorine content, sulfur content, and heavy metal content of the solid waste salts, determine the pyrolysis treatment batches and quantities of the solid waste salts, and clarify the pyrolysis process conditions and operation parameters;

[0046] Step 4: Crush and screen the solid waste salts to remove sundries and mechanical impurities;

[0047] Step 5: Start the flue gas purification device and the induced draft fan. As Figure 2 shown, open the flue gas inlet valve and outlet valve of the bag filter, start the wet acid removal tower, and start the induced draft fan to make the solid waste salt countercurrent rotary kiln pyrolysis system in an air operation state;

[0048] Step 6: Start the waste heat recovery device, and keep the drum water level of the all-membrane wall waste heat boiler within the normal control range;

[0049] Step 7: Start the hot blast stove to heat up and start the countercurrent rotary kiln pyrolysis furnace; as Figure 1 shown, remotely manually open the combustion air flow regulating valve of the burner, and start the combustion air blower 10 of the auxiliary burner; remotely manually open the auxiliary fuel flow regulating valve of the burner, and start the auxiliary burner 9 in the small flow mode of the auxiliary fuel; after the temperature of the hot blast stove 5 and the temperature of the kiln head hood 3 are stable, put the auxiliary fuel flow regulating valve (flow control loop) and the combustion air flow regulating valve (flow control loop) of the burner 9 into the automatic control mode respectively, put the auxiliary fuel flow control loop and the combustion air flow control loop into the proportional control mode, and put the combustion air blower 10 of the auxiliary burner into the remote frequency conversion control mode; gradually increase the auxiliary fuel flow, and steadily increase the temperature of the hot blast stove 5 and the kiln head hood 3; when the temperature of the kiln head hood 3 reaches 700 °C and is stable, put the dual-loop control between the temperature of the kiln tail hood 2, i.e., the pyrolysis temperature of the rotary kiln, and the auxiliary fuel flow of the auxiliary burner 9 into the automatic control mode;

[0050] Step 8: Start the secondary combustion chamber auxiliary burner and heat up the secondary combustion chamber to 1100 °C;

[0051] Step 9: As Figure 1 shown, start the solid waste salt screw feeding device 4, and feed solid waste salt into the rotary kiln 1. When the waste salt is close to the middle position of the rotary kiln 1 furnace chamber, start the pyrolysis blower 6, put the solid waste salt screw feeding device 4 and the pyrolysis blower 6 into the remote frequency conversion control mode, put the pyrolysis air flow control loop of the pyrolysis blower 6 into the automatic control mode, observe the temperature of the kiln tail hood 2 and the oxygen content in the rotary kiln 1, and balance and adjust the frequency of the solid waste salt screw feeding device 4 of the countercurrent rotary kiln pyrolysis furnace, the temperature of the kiln tail hood 2, the auxiliary fuel flow of the hot blast stove 5, the pyrolysis air flow of the pyrolysis blower 6, the frequency of the drive device of the rotary kiln 1, the oxygen content and CO content of the pyrolysis flue gas in the rotary kiln 1, so that the countercurrent rotary kiln pyrolysis working condition quickly enters the stable state; when increasing the pyrolysis load of the rotary kiln 1, the running frequency of the screw feeding device 4 should be adjusted slowly and steadily, the feeding rate of the solid waste salt should be gradually increased, the auxiliary fuel flow of the auxiliary burner 9 should be adjusted synchronously, the pyrolysis air flow of the pyrolysis blower 6 should be adjusted synchronously, so that the temperature, oxygen content and CO content of the kiln tail hood 2 meet the requirements of the waste salt pyrolysis characteristics, the running frequency of the drive device of the rotary kiln 1 should be adjusted steadily, meet the requirements of the solid waste salt pyrolysis time, and ensure that the organic matter content TOC of the pyrolysis products at different treatment loads of the rotary kiln 1 is ≤ 30 ppm;

[0052] Step 10: Start the water-cooled screw discharging device 7, and the inorganic salts after pyrolysis treatment in the rotary kiln 1 are cooled and discharged out of the furnace through the water-cooled screw discharging device 7;

[0053] Step Eleven: As shown in Figure 2 , the pyrolysis flue gas generated by the rotary kiln 1 is secondarily combusted in the secondary combustion chamber, subjected to waste heat recovery, quenching, dry acid removal, bag dust removal, GGH heat exchange, wet scrubbing, pressurized by an induced draft fan, and then discharged into the atmosphere through a chimney;

[0054] Step Twelve: Refine and purify the pyrolysis products of the countercurrent rotary kiln pyrolyzer for solid waste salts; according to the disposal characteristics of solid waste salts, namely the heavy metal components and inorganic salt components contained therein, reasonably select two or more process combinations from various chemical engineering unit technologies such as dissolution, heavy metal precipitation, advanced oxidation, fluoride and hardness removal, evaporation crystallization, and fractional evaporation crystallization, and apply them to refine and purify the inorganic salts after pyrolysis, so as to obtain solid industrial salt products or industrial brine solutions, meeting the product quality requirements for industrial salt use and the environmental pollution control requirements.

[0055] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention and is based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims

1. A countercurrent rotary kiln pyrolysis device for solid waste salt, characterized in that: It includes a countercurrent rotary kiln pyrolysis furnace, a hot blast stove, a solid waste salt screw feeding device, an auxiliary burner, an auxiliary burner combustion air blower, a pyrolysis air blower, a water-cooled screw discharging device, an oxygen analyzer and a CO analyzer; the countercurrent rotary kiln pyrolysis furnace comprises a rotary kiln furnace body, a kiln tail hood, a kiln head hood, a kiln tail sealing device, a kiln head sealing device, a supporting roller device, a retaining ring device, a variable-frequency drive device and a rotary kiln observation sight glass. The rotary kiln furnace body adopts a horizontal rotating cylindrical structure, and the central axis of the rotary kiln furnace body forms an angle of 1-4° with the horizontal. The inner lining of the rotary kiln is made of corundum-mullite refractory material. The two ends of the rotary kiln furnace body are respectively inserted into the kiln tail hood and the kiln head hood. The connections between the rotary kiln furnace body and the kiln tail hood and the kiln head hood are respectively provided with a kiln tail sealing device and a kiln head sealing device. Both the kiln tail sealing device and the kiln head sealing device adopt a structure of stainless steel fish scales + carbon silicon aluminum fiber + stainless steel fish scales + traction rope. The sealing device makes the air leakage rate of the countercurrent rotary kiln pyrolysis furnace less than 2%. The kiln tail hood is provided with a solid waste salt feeding port and a pyrolysis flue gas outlet. The oxygen analyzer and the CO analyzer are arranged on the horizontal section of the pyrolysis flue gas outlet pipeline. The kiln head hood is provided with a hot air tangential inlet, a pyrolysis air tangential inlet, a pyrolysis product discharging port and a rotary kiln observation sight glass. The supporting roller device is provided with a front supporting roller group and a rear supporting roller group to meet the rotating operation of the rotary kiln under load. The retaining ring device is used to prevent the creeping of the rotary kiln furnace body to ensure the safe and reliable operation of the countercurrent rotary kiln pyrolysis furnace. The variable-frequency drive device is used to adjust the rotating speed of the rotary kiln to meet the pyrolysis time requirements of different solid waste salts.

2. The countercurrent rotary kiln pyrolysis device for solid waste salt according to claim 1, characterized in that: The hot blast stove includes a hot blast stove furnace body, an auxiliary burner and an auxiliary burner combustion air blower. The hot blast stove furnace body adopts a horizontal cylindrical structure. One end of the furnace body is provided with a burner interface, and the other end of the furnace body is provided with a hot air outlet. The auxiliary burner is connected to the burner interface of the hot blast stove. The auxiliary burner combustion air blower provides combustion air for the auxiliary burner, and the auxiliary fuel is supplied to the auxiliary burner through a pipeline.

3. The countercurrent rotary kiln pyrolysis device for solid waste salt according to claim 1, characterized in that: The solid waste salt screw feeding device is connected to the solid waste salt feeding port of the kiln tail hood of the countercurrent rotary kiln pyrolysis furnace, and the solid waste salt is transported into the countercurrent rotary kiln pyrolysis furnace through the screw feeding device; the hot air outlet of the hot blast stove is connected to the hot air tangential inlet of the kiln head hood of the countercurrent rotary kiln pyrolysis furnace through a pipeline. The hot air rotates and flows into the countercurrent rotary kiln pyrolysis furnace along the circular kiln head hood. The tangential hot air enhances the gas turbulence in the countercurrent rotary kiln pyrolysis furnace and improves the heat transfer efficiency between the hot air and the solid waste salt; the hot blast stove provides a heat source for the heating and start-up of the solid waste salt countercurrent rotary kiln pyrolysis furnace, supplies heat for the pyrolysis of the organic matter contained in the solid waste salt and precisely controls the pyrolysis operation temperature; the air outlet of the pyrolysis air blower is connected to the pyrolysis air tangential inlet of the kiln head hood of the countercurrent rotary kiln pyrolysis furnace through a pipeline. The pyrolysis air blower variably controls the air volume required for the pyrolysis of the solid waste salt, and the difficult-to-decompose organic matter can be effectively removed, which is beneficial to the refining, purification and resource utilization of the inorganic salts after pyrolysis; the water-cooled screw discharging device is connected to the pyrolysis product discharging port of the kiln head hood of the countercurrent rotary kiln pyrolysis furnace, and the inorganic salts after pyrolysis are cooled and transported out of the furnace through the water-cooled screw discharging device.

4. The countercurrent rotary kiln pyrolysis device for solid waste salt according to claim 1, characterized in that: Temperature transmitters and pressure transmitters are installed on both the kiln tail hood and the kiln head hood of the countercurrent rotary kiln pyrolysis furnace. A temperature transmitter is installed at the pyrolysis product discharge port of the kiln head hood. The variable frequency drive device adopts a remote control mode. The oxygen analyzer and the CO analyzer have functions of remote data transmission, recording, and alarm, and participate in the automatic control of the device.

5. The countercurrent rotary kiln pyrolysis device for solid waste salt according to claim 2, characterized in that: Flow transmitters, flow regulating valves, flow control loops, and pressure transmitters are provided for the auxiliary fuel. Flow transmitters, flow regulating valves, and flow control loops are provided for the combustion-supporting air. A proportional control loop is set between the auxiliary fuel flow control loop and the combustion-supporting air flow control loop. A variable frequency controller is provided for the combustion-supporting air blower of the auxiliary burner. A temperature transmitter is installed in the middle of the hot blast stove to monitor the operating temperature of the hot blast stove.

6. The countercurrent rotary kiln pyrolysis device for solid waste salt according to claim 3, characterized in that: The operating temperature of the countercurrent rotary kiln pyrolysis furnace and the auxiliary fuel flow of the auxiliary burner of the hot blast stove are set for dual-loop control. Flow transmitters, flow regulating valves, and flow control loops are provided for the pyrolysis air supplied by the pyrolysis blower. A dual-loop control is set between the oxygen content of the pyrolysis flue gas and the pyrolysis air flow of the countercurrent rotary kiln pyrolysis furnace.

7. The countercurrent rotary kiln pyrolysis device for solid waste salt according to any one of claims 1-6, characterized in that: It also includes a solid waste salt pretreatment device, a secondary combustion chamber, a waste heat recovery device, a flue gas purification device, an induced draft fan, a chimney, a fly ash collection device, and sewage treatment and disposal. The discharge port of the pretreatment device is connected to the feed port of the solid waste salt screw feeding device of the solid waste salt countercurrent rotary kiln pyrolysis device. The flue gas outlet of the solid waste salt countercurrent rotary kiln pyrolysis device is connected to the flue gas inlet of the secondary combustion chamber. The flue gas outlet of the secondary combustion chamber is connected to the flue gas inlet of the waste heat recovery device. The flue gas outlet of the waste heat recovery device is connected to the flue gas inlet of the flue gas purification device. The flue gas outlet of the flue gas purification device is connected to the flue gas inlet of the induced draft fan. The flue gas outlet of the induced draft fan is connected to the chimney inlet, finally realizing the purification treatment and up-to-standard discharge of the solid waste salt pyrolysis flue gas; the fly ash generated by the waste heat recovery device and the flue gas purification device is landfilled after collection, and the production wastewater of the flue gas purification device is pumped to the sewage treatment device for treatment.

8. The countercurrent rotary kiln pyrolysis device for solid waste salt according to claim 7, characterized in that: The flue gas purification device includes an SNCR denitration device, a quenching device, an activated carbon injection device, a dry acid removal device, a bag filter, a wet scrubber, and a GGH flue gas heat exchanger installed in the high-temperature section of 850 - 1100 °C of the waste heat recovery device flue gas. The 1100 °C high-temperature flue gas at the flue gas outlet of the secondary combustion chamber is connected to the flue gas inlet of the waste heat recovery device. The waste heat recovery device uses a full-film wall waste heat boiler for waste heat recovery and utilization. After waste heat recovery, the flue gas is cooled to 500 °C. An SNCR denitration device is installed in the high-temperature section of 850 °C - 1100 °C of the full-film wall waste heat boiler to achieve flue gas denitration treatment; the flue gas outlet of the waste heat recovery device is connected to the flue gas inlet of the quenching device. The 500 °C flue gas enters the quenching device for quenching and cooling treatment, so that the flue gas is quickly cooled to 200 °C within 1 second, thus enabling the flue gas to avoid the temperature range of 500 °C - 200 °C for dioxin re-synthesis and preventing dioxin re-synthesis; the flue gas outlet of the quenching device and the activated carbon outlet of the activated carbon injection device are connected to the flue gas inlet of the dry acid removal device. The dry acid removal device realizes the removal of some acidic gases in the flue gas and the adsorption and removal of dioxin. The flue gas outlet of the dry desulfurization device is connected to the flue gas inlet of the bag filter. The bag filter filters out particulate matter and most heavy metals in the flue gas. The flue gas outlet of the bag filter is connected to the raw flue gas inlet of the GGH flue gas heat exchanger. The raw flue gas enters the wet scrubbing tower after being cooled by heat exchange in the GGH. The raw flue gas outlet of the GGH flue gas heat exchanger is connected to the flue gas inlet of the wet scrubbing tower. The wet scrubbing tower further removes acidic gases in the flue gas. The flue gas outlet of the wet scrubbing tower is connected to the flue gas inlet of the induced draft fan. The clean flue gas after wet desulfurization enters the GGH heat exchanger after being pressurized by the induced draft fan. The flue gas outlet of the induced draft fan is connected to the clean flue gas inlet of the GGH heat exchanger. The GGH heat exchanger realizes the heat exchange between the low-temperature clean flue gas after wet desulfurization and the high-temperature raw flue gas after bag filtering. The clean flue gas outlet of the GGH heat exchanger is connected to the flue gas inlet of the chimney. The flue gas is discharged into the atmosphere through the chimney.

9. A countercurrent rotary kiln pyrolysis method for solid waste salt, characterized in that, The method is based on a countercurrent rotary kiln pyrolysis device for solid waste salt described in claim 8 and comprises the following steps: Step 1: Classify solid waste salts from different waste-producing enterprises according to their components and properties. Step 2: Conduct chemical analysis on solid waste salts from different waste-producing enterprises and different batches, detect the water content, organic matter content, volatile chlorine content, sulfur content and heavy metals, and establish a disposal characteristic database for solid waste salts to provide basic data for subsequent blending and pyrolysis operation. Step 3: Conduct comprehensive blending on the classified solid waste salts, homogenize the organic matter content, volatile chlorine content, sulfur content and heavy metal content of the solid waste salts, determine the pyrolysis treatment batches and quantities of the solid waste salts, and clarify the pyrolysis process conditions and operation parameters. Step 4: Crush and screen the solid waste salts to remove sundries and mechanical impurities. Step 5: Start the flue gas purification device and the induced draft fan. Step 6: Start the waste heat recovery device. Step 7: Start the hot blast stove to heat up and start the countercurrent rotary kiln pyrolysis furnace. Step 8: Start the secondary combustion chamber auxiliary burner and heat up the secondary combustion chamber to 1100 °C. Step 9: Start the solid waste salt screw feeding device and the pyrolysis fan, feed solid waste salts into the countercurrent rotary kiln pyrolysis furnace. The solid waste salts are dried, pyrolyzed and gasified in the countercurrent rotary kiln to remove the organic pollutants contained in the solid waste salts. Through the dual-loop control system composed of the temperature transmitter at the tail hood of the countercurrent rotary kiln and the flow transmitter and flow regulating valve of the hot blast stove auxiliary burner, adjust the pyrolysis temperature of the solid waste salt countercurrent rotary kiln. Through the control system composed of the pyrolysis fan frequency converter and the oxygen content meter of the countercurrent rotary kiln, adjust the pyrolysis atmosphere of the solid waste salt countercurrent rotary kiln and control the oxygen content in the countercurrent rotary kiln below 1%. Through the precise control of the pyrolysis temperature and pyrolysis atmosphere, ensure the pyrolysis efficiency of the solid waste salt countercurrent rotary kiln. Step 10: Start the water-cooled screw discharging device to cool and convey the pyrolyzed inorganic salts outside the furnace. Step 11: The flue gas generated by the countercurrent rotary kiln pyrolysis furnace is discharged into the atmosphere through the chimney after secondary combustion in the secondary combustion chamber, waste heat recovery, rapid cooling, dry desulfurization, bag filtering, GGH heat exchange, wet scrubbing and pressurization by the induced draft fan.

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