A waste salt resource utilization system and method based on integrated energy conservation and environmental protection of thermal power plants

Abstract

The present invention relates to a waste salt resource utilization system and method based on integrated energy conservation and environmental protection for thermal power plants. The system comprises: a dryer A, a dust removal and deacidification device B, a vacuum device C, a liquid-liquid heat exchanger D, a solid-liquid heat exchanger E, a high-temperature pyrolyzer F, a negative pressure fan G, a dust removal and deacidification device H, a dissolution tank K, a coagulation and sedimentation tank J, a filter press I, a seed crystallization device O, a regulating tank S, an oxidizer T, a regulating tank U, a freeze crystallization device R, a re-dissolution tank N, an evaporative crystallizer M, a steam ejector X, an evaporative crystallizer Q, a desorption device L, an adsorption device P, a freezing device V, an evaporative crystallizer W, and an induced draft fan Z. The present invention can achieve harmless and resourceful disposal of industrially produced hazardous waste salt based on a thermal process that utilizes energy cascades and recovers waste heat, eliminates secondary pollution such as associated dioxins and hazardous waste smoke, and significantly reduces the effective operating energy consumption and hazardous waste salt disposal costs.

Description

Technical Field

[0001] The present invention relates to a waste salt resource utilization system and method based on the integration of energy conservation and environmental protection of thermal power plants, and specifically to a method for collaboratively disposing of high-salt hazardous waste using waste heat resources of thermal power plants. Background Art

[0002] Industrial waste salt comes from the pesticide, dye, pharmaceutical chemical, coal chemical, steel, metallurgy, refining, coking and other industries. One type is a by-product of industrial processes, and the other is a crystalline product from zero sewage discharge. my country's industrial by-product of hazardous waste salt exceeds 10 million tons each year, most of which are not properly handled and pose a great threat to the environment. With the increasing strengthening of my country's high-salt wastewater treatment, the amount of industrial waste salt generated has also increased, and the harmless and resource-based disposal of industrial waste salt has become increasingly urgent.

[0003] The mainstream technical route for resource disposal of industrial waste salt in my country is mainly based on the technical route of "thermal incineration, or even high-temperature melting of waste salt, to achieve carbonization and oxidation of organic matter in waste salt, remove organic matter in waste salt, and then rely on chemical purification of multivalent cations and membrane salt separation technology, combined with evaporation method for crystallization purification". The thermal incineration fuel is currently mainly natural gas. The current problems of the overall technical route are high operating costs, large investments, incomplete resource utilization, and secondary environmental pollution. In particular, there is no unified industry standard and detection method for the treatment of tail gas from burning industrial waste salt. There is a lack of effective technical means for monitoring and control of dioxins in tail gas, component analysis, and unclear dioxin content. The generation mechanism, amount, components, etc., simply applying conventional flue gas purification treatment processes makes it difficult to ensure the treatment effect, which in turn causes air pollution; during equipment operation, there are problems such as crystallized salt scarring, clogging, and corrosion of heat exchange pipes in process pipelines, high equipment replacement rates, and some ultra-fine crystallized salt particles escaping into the atmosphere in the form of aerosols, which invisibly aggravate the generation factors of haze. At the same time, excessive energy consumption causes high disposal costs. In addition, after the resource disposal of waste salt, there is still about 8% of hazardous waste residue that needs to be solidified and landfilled. The expensive landfill disposal costs make the companies that generate waste salt overwhelmed; and the solubility of waste salt makes waste salt unsuitable for landfill, which has extremely high requirements and high costs. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides a waste salt resource utilization system and method based on the integration of energy conservation and environmental protection in thermal power plants.

[0005] The specific description of the present invention is: a waste salt resource utilization system based on the integration of energy conservation and environmental protection of thermal power plants, characterized in that it includes: a dryer A, a dust removal and deacidification device B, a vacuum device C, a liquid-liquid heat exchanger D, a solid-liquid heat exchanger E, a high-temperature pyrolyzer F, a negative pressure fan G, a dust removal and deacidification device H, a dissolution tank K, a coagulation sedimentation tank J, a filter press I, a seed crystallization device O, a regulating tank S, an oxidizer T, a regulating tank U, a freezing crystallization device R, a back dissolution tank N, an evaporation crystallizer M, a steam ejector X, an evaporation crystallizer Q, an analysis device L, an adsorption device P, a freezing device V, an evaporation crystallizer W, and an induced draft fan Z; wherein the first inlet 1 of the dryer A is the waste salt inlet, and the first outlet 2 of the dryer A is the waste salt after drying. The outlet is connected to the first inlet 18 of the high-temperature pyrolyzer F, the second outlet 3 of the dryer A is the dry tail gas outlet, and is connected to the inlet 4 of the dust removal and deacidification device B; the first outlet 6 of the dust removal and deacidification device B is the exhaust gas outlet after dust removal and deacidification, and is connected to the inlet 7 of the vacuum device C, the second outlet 5 of the dust removal and deacidification device B and the first outlet 24 of the dust removal and deacidification device H are solid waste outlets, both of which are connected to the second inlet 19 of the high-temperature pyrolyzer F, the second outlet 25 of the dust removal and deacidification device H is the exhaust gas outlet after dust removal and deacidification, and is connected to the first inlet 91 of the induced draft fan Z through a pipeline; the non-condensable gas outlet 8 of the vacuum device C is connected to the second inlet 90 of the induced draft fan Z through a pipeline, and the outlet 92 of the induced draft fan Z is a gas outlet, and the gas into the power plant boiler; the first outlet 20 of the high-temperature pyrolyzer F is the pyrolysis gas outlet, which is connected to the inlet 23 of the dust removal and deacidification device H through the inlet 21 of the negative pressure fan G, and the second outlet 17 of the high-temperature pyrolyzer F is the hot waste salt outlet, which is connected to the first inlet 16 of the solid-liquid heat exchanger E; the first outlet 15 of the solid-liquid heat exchanger E is the outlet of the waste salt after cooling, which is connected to the inlet 26 of the dissolution tank K, the second inlet 14 of the solid-liquid heat exchanger E is the inlet of the water before heat exchange and heating, which is connected to the first outlet 11 of the liquid-liquid heat exchanger D, the second outlet 13 of the solid-liquid heat exchanger E is the outlet of the water after heat exchange and heating, which is connected to the first inlet 12 of the liquid-liquid heat exchanger D; the second inlet 9 of the liquid-liquid heat exchanger D is the inlet of the condensate discharged from the boiler , the second outlet 10 of the liquid-liquid heat exchanger D is the outlet of the heated condensate, and the condensate returns to the boiler system of the power plant; the outlet 27 of the dissolution tank K is the salt solution outlet, which is connected to the first inlet 28 of the coagulation sedimentation tank J, and the second inlet 29 of the coagulation sedimentation tank J is the dosing port. The first outlet 50 of the coagulation sedimentation tank J is the mud discharge port at the bottom, which is connected to the inlet 31 of the filter press I. The first outlet 32 ​​of the filter press I is the clear liquid discharge port generated after pressure filtration, which is connected to the third inlet 30 of the coagulation sedimentation tank J. The second outlet 33 of the filter press I is the solid matter discharge port generated by pressure filtration, and the second outlet 47 of the coagulation sedimentation tank J is the salt solution discharge port after precipitation and clarification, which is connected to the first inlet 48 of the seed crystal precipitation device O;The second inlet 46 of the seed crystal precipitation device O is a dosing port, the first outlet 49 of the seed crystal precipitation device O is an outlet for seed particles, the second outlet 51 of the seed crystal precipitation device O is a water outlet, and is connected to the first inlet 52 of the regulating tank S; the second inlet 63 of the regulating tank S is a hydrochloric acid inlet, the outlet 64 of the regulating tank S is connected to the inlet 65 of the oxidizer T, the first outlet 68 of the oxidizer T is connected to the first inlet 69 of the regulating tank U, the second inlet 70 of the regulating tank U is a sodium hydroxide inlet, the outlet 66 of the regulating tank U is connected to the inlet 62 of the freezing crystallization device R, the first outlet 53 of the freezing crystallization device R is connected to the first inlet 45 of the back-dissolution tank N, the second inlet 84 of the back-dissolution tank N is a condensed water inlet, and is connected to the first outlet 54 of the evaporation crystallizer M. Then, the outlet 44 of the back-dissolving pool N is connected to the first inlet 43 of the evaporation crystallizer M, the second outlet 61 of the freezing crystallization device R is the high brine outlet, and is connected to the first inlet 71 of the evaporation crystallizer Q; the second inlet 85 of the evaporation crystallizer M and the second inlet 86 of the evaporation crystallizer Q are steam inlets, the second outlet 55 of the evaporation crystallizer M and the first outlet 74 of the evaporation crystallizer Q are secondary steam outlets, which are respectively connected to the first inlet 57 of the steam ejector X and the second inlet 58 of the steam ejector X, the third outlet 42 of the evaporation crystallizer M and the second outlet 72 of the evaporation crystallizer Q are mother liquor discharge ports of evaporation crystallization, both of which are connected to the first inlet 41 of the adsorption device P, the third outlet 73 of the evaporation crystallizer Q is the crystallized salt outlet, and the evaporation crystallizer The fourth outlet of the device Q is the condensate outlet, the third inlet 59 of the steam ejector X is the high-pressure steam inlet, and the outlet 60 of the steam ejector X is the outlet for supplying steam outside the power plant; the second inlet 40 of the adsorption device P is the inlet of the hydrochloric acid solution, the first outlet 39 of the adsorption device P is the outlet of the solid matter containing sodium sulfate, which is connected to the first inlet 37 of the desorption device L, the second inlet 34 of the desorption device L is the inlet of sodium hydroxide, the first outlet 88 of the desorption device L is the adsorbent outlet, which is connected to the third inlet 77 of the adsorption device P, the second outlet 36 of the desorption device L is the outlet of the sodium sulfate solution after desorption, which is connected to the third inlet 38 of the evaporation crystallizer M, the second outlet 35 of the adsorption device P is the outlet of the solution after adsorption, which is connected to the refrigeration device V The second inlet 75 of the refrigeration unit V is connected to the first outlet 78 of the refrigeration unit V, which is the outlet for crystallized salt. The second outlet 79 of the refrigeration unit V is connected to the first inlet 80 of the evaporation crystallizer W, the first outlet 82 of the evaporation crystallizer W is the outlet for crystallized salt, the second outlet 81 of the evaporation crystallizer W is the outlet for the mother liquor of evaporation crystallization, and the third inlet 76 of the refrigeration unit V. The third outlet 87 of the evaporation crystallizer W is the outlet for the mother liquor of evaporation crystallization, and the fourth outlet 83 of the evaporation crystallizer W is the outlet for condensed water. The dryer A adopts one of an electrically heated rotary kiln, an electrically heated rake furnace, and an electrically heated drum dryer A. The solid-liquid heat exchanger E adopts a water-cooled drum slag cooler or a disc slag cooler. The liquid-liquid heat exchanger D adopts a plate or shell-and-tube heat exchanger.

[0006] A waste salt resource recovery method based on a waste salt resource recovery system integrating energy conservation and environmental protection in thermal power plants, comprising the following process steps:

[0007] The waste salt is sent to the dryer A for drying. The drying temperature in the dryer A is controlled between 100°C and 300°C. The dryer A adopts a vacuum drying method with a vacuum degree between 0.008MPa and 0.01MPa.

[0008] The dry exhaust gas generated by dryer A is treated by dust removal and deacidification device B. The specific process is as follows: dust removal and deacidification device B uses a high-temperature resistant composite filter cartridge dust collector. The filter element of the high-temperature resistant composite filter cartridge dust collector is made of inorganic silicate composite materials. The core of the high-temperature resistant composite filter cartridge dust collector is built with a vanadium-titanium catalyst. The vanadium-titanium catalyst serves as a desulfurization and denitrification catalyst and reduces nitrogen oxides in the dry exhaust gas to nitrogen.

[0009] The dust removal and deacidification device B removes hydrogen chloride, sulfide gas, and hydrogen fluoride gas from the flue gas by adding an alkaline agent. The alkaline agent is sodium hydroxide, sodium carbonate, or calcium hydroxide. The operating temperature of the dust removal and deacidification device B is between 30°C and 600°C. The gas treated by the dust removal and deacidification device B is driven by the vacuum device C. The deacidified gas enters the power plant boiler through the induced draft fan Z and is burned.

[0010] The dried waste salt enters the high-temperature pyrolyzer F for pyrolysis. The high-temperature pyrolyzer F performs pyrolysis in an oxygen-free state. The pyrolysis temperature of the high-temperature pyrolyzer F is controlled between 300°C and 600°C, with the instantaneous maximum temperature not exceeding 1000°C. A continuous feeding and continuous discharging production method is adopted. The pyrolysis gas generated by the high-temperature pyrolyzer F passes through the negative pressure fan G and enters the dust removal and deacidification device H for dust removal and deacidification treatment. The gas treated by the dust removal and deacidification device H enters the power plant boiler.

[0011] The dust removal and deacidification device H adopts a high-temperature resistant composite filter cartridge dust collector. The filter element of the high-temperature resistant composite filter cartridge dust collector adopts an inorganic silicate composite material. The core of the high-temperature resistant composite filter cartridge dust collector is built with a vanadium-titanium catalyst. The vanadium-titanium catalyst is a kind of desulfurization and denitrification catalyst, which reduces nitrogen oxides in the dry exhaust gas to nitrogen.

[0012] The acid gas content at the outlet of the dust removal and deacidification device B and the dust removal and deacidification device H is less than 5 mg / L, and the dust content is less than 3 mg / L;

[0013] The solid waste generated by the dust removal and deacidification device B and the dust removal and deacidification device H is sodium sulfate, sodium chloride, sodium fluoride, or a mixture containing a small amount of sodium nitrate, some dust, or a mixture of calcium salts. The waste salt after pyrolysis produced by the high-temperature pyrolyzer F enters the solid-liquid heat exchanger E and exchanges heat with water from the liquid-liquid heat exchanger D. The waste salt cooled by heat exchange enters the dissolution tank K for dissolution. The water heated by heat exchange enters the liquid-liquid heat exchanger D and exchanges heat with condensate from the power plant boiler in the liquid-liquid heat exchanger D. The condensate heated by heat exchange returns to the boiler system, realizing the recovery of high-temperature heat in the waste salt into the boiler.

[0014] The inlet salt temperature of the solid-liquid heat exchanger E is lower than 700°C and the outlet salt temperature is lower than 100°C;

[0015] The condensate temperature entering the boiler through the liquid-liquid heat exchanger D is lower than 100°C, and the outlet water temperature is lower than 100°C;

[0016] The hazardous waste salts from the solid-liquid heat exchanger E enter the dissolution tank K. The salt solution in the dissolution tank K enters the coagulation sedimentation tank J, where it reacts with the added coagulant, flocculant, heavy metal remover, and sodium hydroxide. The divalent or higher cations of magnesium ions in the solution combine with hydroxide to form insoluble matter, and the heavy metals in the solution are adsorbed and chelated. Under the action of the coagulant, flocculation and sedimentation are formed and deposited at the bottom of the coagulation sedimentation tank J.

[0017] The mud at the bottom of the coagulation sedimentation tank J enters the filter press I under the action of the mud pump for pressure filtration separation. The salt solution clarified by the precipitation in the coagulation sedimentation tank J enters the seed crystal precipitation device O. Calcium carbonate seeds and sodium carbonate reagent are introduced into the seed crystal precipitation device O. The principle of induced crystallization is used to achieve a reaction between sodium carbonate and calcium ions in the waste salt to form granular calcium carbonate.

[0018] The granular calcium carbonate is recycled into the desulfurization system of the power plant as a desulfurizer;

[0019] After the salt solution from the seed crystal precipitation device O enters the regulating tank S, hydrochloric acid is used in the regulating tank S to adjust the pH to between 5 and 7, and then enters the oxidizer T for oxidation treatment. The salt solution oxidized by the oxidizer T enters the regulating tank U, and sodium hydroxide is used in the regulating tank U to adjust the pH to above 7, and then enters the freeze crystallization device R;

[0020] The oxidizer T uses electrolytic oxidation to oxidize and decompose the residual organic matter in the salt solution into carbon dioxide and water, and oxidize the nitrogen oxides in the salt solution into nitrogen;

[0021] The freezing crystallization device R freezes and precipitates the sodium sulfate in the salt solution, and the obtained sodium sulfate decahydrate solid enters the re-dissolution tank N. The solution in the re-dissolution tank N enters the evaporation crystallizer M; evaporation crystallization is performed to obtain anhydrous sodium sulfate. The high brine produced by the freezing crystallization device R enters the evaporation crystallizer Q; evaporation crystallization is performed to obtain sodium chloride. The freezing temperature of the freezing crystallization device R is below 0°C, and the salt solution stays in the freezing crystallization device R for more than 2 hours.

[0022] The refrigeration device V adopts a heat pump type refrigeration unit;

[0023] The adsorption device P uses an adsorbent to adsorb sodium sulfate in the mother liquor. The adsorbent uses zirconium hydroxide. The pH value of the solution in the adsorption device P is maintained between 4 and 6. The adsorption device P discharges a solid compound formed by the reaction of zirconium hydroxide and sodium sulfate. At this time, the solution in the adsorption device P does not contain sodium sulfate. The solid matter and a trace amount of solution enter the analysis device L for analysis. The sodium sulfate solution after analysis by the analysis device L enters the evaporation crystallizer M. The solution after adsorption by the adsorption device P enters the freezing device V for low-temperature freezing crystallization to precipitate potassium chloride.

[0024] The desorbent L adds sodium hydroxide to reduce the desorbent, and the reduced desorbent returns to the adsorption device P to achieve desorbent recycling;

[0025] The adsorption device P discharges a solution mainly containing sodium chloride and potassium chloride into the freezing device V and then into the evaporation crystallizer W; evaporation and crystallization are carried out to obtain sodium chloride crystal salt, and part of the mother liquor of the evaporated crystallization is returned to the freezing device V, and the other part is discharged. The boiling point of the evaporation crystallizer W is maintained above 11°C; the evaporation crystallizer W adopts the FC reverse cycle evaporation crystallizer type or the Oslo evaporation crystallizer type.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. For the first time, a method for the coordinated disposal of waste salt based on thermal power plants is proposed. By utilizing the technical principle of energy cascade utilization, the resource-based disposal of hazardous waste salt is achieved with less energy consumption, thereby significantly reducing the cost of waste salt disposal. The basic technical implementation method is: the electricity consumed in the waste salt disposal process is taken from the power plant. In the waste salt drying, waste salt pyrolysis, thermal and cold crystallization salt precipitation links, the electricity is converted into heat energy. Through heat energy recovery, most of the heat energy is recovered to the power plant, realizing secondary energy recovery, or the secondary heat energy is used for industrial production, heating, etc., thereby realizing cascade and efficient utilization of energy.

[0028] 2. Utilize the secondary tail gas from the power plant's coordinated disposal of waste salt and achieve efficient utilization of the secondary tail gas. The technical implementation method is: the waste salt is dried and pyrolyzed using electricity, so the tail gas generated is all combustible organic gas. By removing the acidic gases in the gas and feeding the remaining tail gas into the power plant boiler for combustion as auxiliary fuel, the thermal energy of the organic tail gas is efficiently utilized and recovered. Furthermore, the conditions for the formation of dioxins in the tail gas are completely eliminated, thus completely solving the problem of tail gas treatment from waste salt disposal by utilizing the coordinated disposal method of the power plant.

[0029] 3. For the first time, it is proposed to use high-temperature resistant composite filter cartridge-type integrated dust removal, desulfurization and denitrification equipment for the waste salt drying and pyrolysis process links, and for the tail gas containing acidic gases generated in the drying and pyrolysis process links, and at the same time to achieve catalytic reaction and completely eliminate dioxins that may be contained in the tail gas; its technical advantage lies in avoiding the shortcomings of existing waste salt disposal technologies such as the use of high-temperature oxidation, carbonization or waste salt melting equipment to generate tail gas, which requires rapid cooling, wet deacidification, activated carbon adsorption and other measures, resulting in large heat energy losses in hot flue gas, the generation of deacidified high-salt wastewater, the generation of denitrification hazardous waste, and the generation of activated carbon hazardous waste in the activated carbon adsorption link, as well as the industry problem of incomplete removal of dioxins in tail gas and difficulty in meeting emission requirements.

[0030] 4. The use of electric heating drying and electric heating pyrolysis technology, on the one hand, the equipment technology used in this technology is mature and easy to implement; on the other hand, compared with the existing technical means of drying, carbonizing and oxidizing high-temperature flue gas generated by burning natural gas, there is no need to set up a secondary combustion chamber, which saves a lot of energy and reduces exhaust emissions by more than 90%, avoids a large amount of fine salt dust particles in the exhaust gas, and the generated exhaust gas does not contain solid particulate matter, thereby eliminating the problems of pipe blockage, corrosion, large exhaust emissions, difficult production control, excessive exhaust emissions, and emission of fine particles in the exhaust gas into the atmosphere, which aggravates atmospheric haze in the exhaust emission link of existing waste salt disposal equipment.

[0031] 5. Achieved 100% resource utilization of waste salt hazardous waste and no secondary hazardous waste was generated.

[0032] Another technical advantage of the present invention is that it achieves 100% resource utilization of waste salt disposal, without the generation of secondary pollutant waste residues and the need for landfill sites. It completely solves the safety hazards of waste salt leakage and groundwater pollution caused by landfill, and solves the problem of excessive secondary hazardous waste and solid waste generated by existing waste salt disposal devices. Compared with the existing technology, waste salt disposal inevitably produces secondary solid hazardous waste and requires landfill solidification treatment. The present invention realizes 100% resource utilization of soluble salts in waste salt, such as sodium sulfate, to produce industrial-grade sodium sulfate, 100% resource utilization of sodium chloride, and 100% resource utilization of potassium chloride. Solid insoluble matter is generated in the process of treating waste salt, which can be mixed with power plant coal ash after treatment and used as construction auxiliary materials, so no secondary solid hazardous waste is generated.

[0033] 6. Low processing cost, low disposal cost and easy implementation of technology.

[0034] Since waste salt disposal is coupled with power plants, the energy cascade utilization and recovery technology is easier to implement. Compared with existing technical routes, the technical method can significantly reduce operating costs, solve the current high energy consumption situation of waste salt disposal in my country, and reduce carbon emissions. The present invention is composed of different process links, and the technologies used in each process link are guaranteed by successful implementation cases. Therefore, the technical threshold for the implementation of the present invention is not high and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural block diagram of a waste salt resource utilization system based on the integration of energy conservation and environmental protection in thermal power plants provided by an embodiment of the present invention.

[0036] Figure 1The numbers and names of the components are as follows. Dryer A, dust removal and deacidification device B, vacuum device C, liquid-liquid heat exchanger D, solid-liquid heat exchanger E, high-temperature pyrolyzer F, negative pressure fan G, dust removal and deacidification device H, filter press I, coagulation sedimentation tank J, dissolution tank K, analysis device L, evaporation crystallizer M, back dissolution tank N, seed crystal precipitation device O, adsorption device P, evaporation crystallizer Q, freezing crystallization device R, regulating tank S, oxidizer T, regulating tank U, freezing device V, evaporation crystallizer W, steam ejector X, induced draft fan Z, first inlet 1 of dryer A, first outlet 2 of dryer A, second outlet 3 of dryer A, inlet 4 of dust removal and deacidification device B, second outlet 5 of dust removal and deacidification device B, first outlet 6 of dust removal and deacidification device B, inlet 7 of vacuum device C, non-condensable gas outlet of vacuum device C 8. Second inlet of liquid heat exchanger D 9, second outlet 10 of liquid-liquid heat exchanger D, first outlet 11 of liquid-liquid heat exchanger D, first inlet 12 of liquid-liquid heat exchanger D, second outlet 13 of solid-liquid heat exchanger E, second inlet 14 of solid-liquid heat exchanger E, first outlet 15 of solid-liquid heat exchanger E, first inlet 16 of solid-liquid heat exchanger E, second outlet 17 of high-temperature pyrolyzer F, first inlet 18 of high-temperature pyrolyzer F, second inlet 19 of high-temperature pyrolyzer F, first outlet 20 of high-temperature pyrolyzer F, inlet 21 of negative pressure fan G, inlet 23 of dust removal and deacidification device H, first outlet 24 of dust removal and deacidification device H, second outlet 25 of dust removal and deacidification device H, inlet 26 of dissolution tank K, outlet 27 of dissolution tank K, first outlet 28 of coagulation and sedimentation tank J an inlet 28 of the first coagulation sedimentation tank J, a second inlet 29 of the second coagulation sedimentation tank J, a third inlet 30 of the second coagulation sedimentation tank J, an inlet 31 of the filter press I, a first outlet 32 ​​of the filter press I, a second outlet 33 of the filter press I, a second inlet 34 of the analysis device L, a second outlet 35 of the adsorption device P, a second outlet 36 of the analysis device L, a first inlet 37 of the analysis device L, a third inlet 38 of the evaporation crystallizer M, a first outlet 39 of the adsorption device P, a second inlet 40 of the adsorption device P, a first inlet 41 of the adsorption device P, a third outlet 42 of the evaporation crystallizer M, a first inlet 43 of the evaporation crystallizer M, an outlet 44 of the back-dissolution tank N, a first inlet 45 of the back-dissolution tank N, a second inlet 46 of the seed crystal precipitation device O, a second outlet 37 of the second coagulation sedimentation tank J, a second outlet 38 of the second coagulation sedimentation tank J, a first outlet 39 of the second adsorption device P, a second outlet 40 of the second adsorption device P, a first inlet 41 of the adsorption device P, a third outlet 42 of the evaporation crystallizer M, a first inlet 43 of the evaporation crystallizer M, an outlet 44 of the back-dissolution tank N, a first inlet 45 of the back-dissolution tank N, a second inlet 46 of the seed crystal precipitation device O, a second outlet 38 of the second coagulation sedimentation tank J, a first inlet outlet 47, the first inlet 48 of the crystal seed precipitation device O, the first outlet 49 of the crystal seed precipitation device O, the first outlet 50 of the coagulation sedimentation tank J, the second outlet 51 of the crystal seed precipitation device O, the first inlet 52 of the regulating tank S, the first outlet 53 of the freezing crystallizer R, the first outlet 54 of the evaporation crystallizer M, the second outlet 55 of the evaporation crystallizer M, the third outlet 56 of the evaporation crystallizer M, the first inlet 57 of the steam ejector X, the second inlet 58 of the steam ejector X, the third inlet 59 of the steam ejector X, the outlet 60 of the steam ejector X, the second outlet 61 of the freezing crystallizer R, the inlet 62 of the freezing crystallizer R, the second inlet 63 of the regulating tank S, the outlet 64 of the regulating tank S, the inlet 65 of the oxidizer T,Outlet 66 of regulating tank U, first outlet 68 of oxidizer T, first inlet 69 of regulating tank U, second inlet 70 of regulating tank U, first inlet 71 of evaporation crystallizer Q, second outlet 72 of evaporation crystallizer Q, third outlet 73 of evaporation crystallizer Q, first outlet 74 of evaporation crystallizer Q, second inlet 75 of freezing device V, third inlet 76 of freezing device V, third inlet 77 of adsorption device P, first outlet 78 of freezing device V, second outlet 79 of freezing device V, first inlet 80 of evaporation crystallizer W, second outlet 81 of evaporation crystallizer W, first outlet 82 of evaporation crystallizer W, fourth outlet 83 of evaporation crystallizer W, second inlet 84 of remelting tank N, second inlet 85 of evaporation crystallizer M, second inlet 86 of evaporation crystallizer Q, third outlet 87 of evaporation crystallizer W, first outlet 88 of desorption device L, fourth outlet 89 of evaporation crystallizer Q, second inlet 90 of induced draft fan Z, first inlet 91 of induced draft fan Z, and outlet 92 of induced draft fan Z. DETAILED DESCRIPTION

[0037] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0038] Figure 1 The present invention provides a structural block diagram of a waste salt resource utilization system based on the integration of energy conservation and environmental protection of thermal power plants, which includes: a dryer A, a dust removal and deacidification device B, a vacuum device C, a liquid-liquid heat exchanger D, a solid-liquid heat exchanger E, a high-temperature pyrolyzer F, a negative pressure fan G, a dust removal and deacidification device H, a dissolution tank K, a coagulation sedimentation tank J, a filter press I, a seed crystallization device O, a regulating tank S, an oxidizer T, a regulating tank U, a freezing crystallization device R, a back-dissolution tank N, an evaporation crystallizer M, a steam ejector X, an evaporation crystallizer Q, an analysis device L, an adsorption device P, a freezing device V, an evaporation crystallizer W, and a fan Z.

[0039] First, the waste salt is mechanically conveyed to port 1 of dryer A. Dryer A can utilize an electrically heated rotary kiln, an electrically heated rake furnace, or an electrically heated drum dryer, with the latter being preferred. Electric heating can be either resistive or electromagnetic. The heating elements are located at the bottom or periphery of the kiln, and heat transfer between the heat source and the material occurs via kiln tubes or corrosion-resistant heat transfer materials. The heating temperature within dryer A is controlled between 100°C and 300°C. Dryer A is constructed of corrosion-resistant materials such as 316L, 2205, duplex steel, or titanium alloy. Negative pressure is maintained within dryer A, maintaining a vacuum between 0.008 MPa and 0.01 MPa. Port 2 of dryer A serves as the outlet for the dried waste salt, connected via a conveying pipeline to port 18 of pyrolyzer F, where the salt enters the pyrolyzer F for pyrolysis.

[0040] After drying in dryer A, the waste salt has a moisture content below 0.2%, is discharged through port 2, and enters inlet 18 of high-temperature pyrolyzer F through a conveying device, and enters the internal pyrolysis of high-temperature pyrolyzer F.

[0041] Port 3 of dryer A is the outlet of dry tail gas, which is connected to port 4 of dust collector and deacidifier B. Dust collector and deacidifier B adopts high-temperature resistant composite filter cartridge dust collector, which is a dry desulfurization and denitrification equipment. The high-temperature resistant composite filter cartridge core has a built-in vanadium-titanium catalyst. Vanadium-titanium catalyst is a catalyst. By adding an alkali agent to the dust collector and deacidifier B, the purpose of purifying acidic hydrogen gases such as sulfur dioxide, hydrogen chloride, and hydrogen fluoride in the gas is achieved, and the acidic gas is converted into the corresponding sodium salt or calcium salt. The alkali agent is preferably sodium bicarbonate, followed by limestone and sodium hydroxide. The operating temperature of the dust collector and deacidifier B is between 30℃ and 600℃. The preferred agent for removing nitrogen oxides is urea. The mechanism of the denitrification reaction is as follows.

[0042] 4NO+2NH 22 CO+O2---4N2+4H2O+2CO2

[0043] After purification by the high-temperature resistant composite cartridge dust collector, the dust content in the gas is less than 5mg / m3, the hydrogen chloride removal rate is as high as 97%, the sulfur oxide removal rate is as high as 95%, the nitrogen oxide removal rate is as high as 95%, and the dioxin removal efficiency is as high as 99%.

[0044] The general reaction equation for dioxin removal is:

[0045] C12HnCl8-nO2+9+0.5nO2=n-4H2O+12CO2+8-nHCl

[0046] After deacidification, the waste gas is discharged from port 8 of the vacuum device C under the action of the induced draft fan Z, enters port 92 of the induced draft fan Z, is connected to the inlet of the power plant's combustion-supporting fan, and enters the boiler for combustion.

[0047] Since the amount of tail gas generated by the drying of waste salt is small, after entering the combustion-supporting air system of the power plant, it is quickly diluted by the combustion-supporting air and then enters the boiler, so the operation is safe.

[0048] The vacuum device C maintains a vacuum degree between 0.008 MPa and 0.01 MPa. The vacuum device C can adopt one or two of a Roots vacuum pump, a water ring pump, a reciprocating pump, a sliding valve pump, a rotary vane pump, and a diffusion pump, and a precision gas filter is configured at the gas source inlet of the vacuum pump.

[0049] The waste salt after drying and dehydration enters the high-temperature pyrolyzer F, which is an electrically heated rotary kiln. It can adopt two heating methods: resistive or electromagnetic. The structure adopts rotary and disc heaters. The high-temperature pyrolyzer F realizes pyrolysis and carbonization of the waste salt in an oxygen-free state. The high-temperature pyrolyzer F cylinder is constructed of corrosion-resistant materials such as 316L or 2205, duplex steel, or titanium alloy. The furnace lining utilizes a corundum-compounded inorganic, salt-resistant material. The optimal pyrolysis temperature in the high-temperature pyrolyzer F is controlled between 300°C and 600°C, with a maximum instantaneous temperature not exceeding 1000°C. The pyrolyzer F utilizes a continuous feed and discharge system. Under high temperature and oxygen depletion, the organic matter in the waste salt undergoes molecular chain breakage, transforming into small, gaseous organic compounds based on carbon, hydrogen, oxygen, and nitrogen, as well as sulfur and chlorine. These compounds may also contain acidic gases such as hydrogen fluoride and hydrogen chloride. Some of the carbon in the waste salt remains in the form of carbon ash. The pyrolysis temperature in the high-temperature pyrolyzer F can be smoothly adjusted, with a maximum temperature not exceeding 900°C. The advantages of using electric heating for pyrolysis include a small furnace, high efficiency, and no secondary dust generation. The pyrolysis gas generated by the high-temperature pyrolyzer F is discharged from the high-temperature pyrolyzer F20 port and enters the 21 inlet of the negative pressure fan G. The negative pressure fan G is a high-temperature and corrosion-resistant fan with a rated high temperature resistance of 600°C. Under the action of the fan boost pressure, the gas enters the dust removal and deacidification device H. The dust removal and deacidification device H adopts a high-temperature resistant composite filter cartridge dust collector. Its mechanism is the same as that of the dust removal and deacidification device B. After deacidification and dust removal, hydrogen fluoride, hydrogen chloride, hydrogen sulfide, sulfur dioxide, nitrogen oxides and other gases that may be contained in the gas are reacted and adsorbed and then solidified in the form of sodium salt or calcium salt.

[0050] After deacidification and dust removal, the high-temperature gas exits through port 25 of dust removal and deacidification unit H and enters the inlet of the induced draft fan Z. It then enters the boiler for combustion, where the waste heat of the gas is reused. Solid waste generated by dust removal and deacidification units H and B, such as sodium sulfate, sodium sulfide, sodium chloride, or their corresponding calcium salts, enters port 19 of the high-temperature pyrolyzer F through ports 5 and 24, respectively, and enters the solid-liquid heat exchanger E along with the waste salt.

[0051] After pyrolysis, over 90% of the organic matter in the waste salt is removed. Large organic molecules in the waste salt are broken down into smaller molecules, eliminating their toxicity. The hot waste salt enters solid-liquid heat exchanger E. Port 16 of solid-liquid heat exchanger EE receives hot salt, port 15 discharges cooled salt, port 14 receives low-temperature water, and port 13 discharges high-temperature water. The water temperature entering port 14 of solid-liquid heat exchanger E is between 37°C and 70°C, while the water temperature at outlet 13 is between 42°C and 99°C. Solid-liquid heat exchanger E is a water-cooled drum-type slag cooler, with an inlet waste salt temperature below 600°C and an outlet salt temperature below 100°C. The heat exchanger walls in contact with the waste salt are made of corrosion-resistant materials such as 2205 duplex steel or titanium alloy. The advantage of using solid-liquid heat exchanger E is that it cools the high-temperature waste salt while simultaneously recovering heat energy from the waste salt to the power plant boiler system, with a heat recovery efficiency of at least 80%.

[0052] Liquid-liquid heat exchanger D is a plate-type or shell-and-tube heat exchanger. Its inlet 9 receives condensate from the boiler system, with a temperature exceeding 30°C. After reaching an outlet 10 with a temperature exceeding 42°C, the condensate returns to the boiler system. This heat is circulated within a closed circuit formed by ports 11 and 14 of liquid-liquid heat exchanger D, ports 12 and 13 of solid-liquid heat exchanger E, and the interconnecting insulated piping, acting as a heat carrier and heat transfer agent. Cooled waste salt is discharged from port 15 of solid-liquid heat exchanger E. This waste salt passes through a conveyor and enters dissolution tank K for dissolution, where the water-to-solids ratio is greater than 4.

[0053] The solid salt in the dissolution tank K is converted into a liquid salt solution. The salt solution flows out from the 27th port of the dissolution tank K and enters the pool through the pipe connected to the 28th port of the coagulation sedimentation tank J. The 29th port of the coagulation sedimentation tank J is the dosing port, where coagulants, heavy metal removers, sodium hydroxide, etc. are added. Through the reaction of the agents, the magnesium ions, iron ions and other multivalent cations, as well as heavy metal ions, suspended insoluble matter, etc. in the coagulation sedimentation tank J are effectively removed. The coagulation sedimentation tank J adopts an integrated clarification tank.

[0054] The sedimentation time of coagulation sedimentation tank J is not less than 120 minutes. The mud at the bottom of coagulation sedimentation tank J enters port 31 of filter press I through port 50. After separation by filtration, the moisture content of the solid matter is reduced to below 50%. It then goes out through port 33 and enters the waste coal slag and fly ash of the power plant as construction auxiliary materials. The clear liquid returns to port 30 of coagulation sedimentation tank J through port 32 of filter press I.

[0055] Filter Press I utilizes a plate and frame filter press, which consists of five major components: filter plates, a hydraulic system, a filter frame, a plate transport system, and an electrical system. Plate and frame filter presses are mature and widely used, making them essential equipment for wastewater treatment.

[0056] After precipitation and clarification, the salt solution enters the seed crystallization device O, which is a crystallization reaction tank for precipitating calcium carbonate crystals. Calcium carbonate seeds and a sodium carbonate reagent are introduced into the seed crystallization device O at port 46. Using the principle of induced crystallization, the sodium carbonate and calcium ions react to form fine calcium carbonate particles. These fine particles circulate repeatedly within the salt solution through the seed crystallization device O, gradually adhering to the surface of the calcium carbonate seeds and gradually growing to form granular calcium carbonate. Calcium carbonate particles of a certain size are then discharged through port 49 of the seed crystallization device O. After dehydration, they are used as a desulfurization agent in thermal power plants. The depth of the seed crystallization device O is more than five times the flow rate of the salt solution, the width is more than four times the flow rate, and the device volume is more than ten times greater. The mature technology of induced calcium carbonate crystallization has achieved resource recovery and utilization of calcium ions in salt, and is used as a desulfurization agent in power plant desulfurization systems. The decalcification rate of the seed crystallization device OO exceeds 80%.

[0057] The effluent from the seed crystal precipitation device O exits at port 51 and enters the regulating tank S. The regulating tank S is a civil structure with a corrosion-resistant design. Its port 63 receives hydrochloric acid to adjust the pH to between 5 and 7. The effluent from the regulating tank S enters the oxidizer T, which is characterized by the production of hydroxyl radicals (OH) with strong oxidizing power. The oxidizer T has a free radical formation time of 10-14 seconds and a free radical reaction time of approximately 1 second. The reaction time of the free radicals with other organic matter is 1-10 seconds, with an oxidation rate constant of 10-109 L / mol.s and a diffusion rate limit of 10-10 L / mol.s. The oxidizer T reduces residual organic matter in the salt solution to below 2 ppm and total nitrogen to below 10 ppm.

[0058] The effluent from oxidizer T is regulated in regulating tank U, and after the pH of the salt solution is increased to greater than 7 by the addition of sodium hydroxide, it enters freeze crystallization unit R. This unit freezes and precipitates sodium sulfate from the salt solution, freezing it below -0°C to produce sodium sulfate decahydrate. The freeze crystallization unit R consists of a heat pump refrigerator, a precooler, a freezer, a crystallizer, and a settler. The condenser in the heat pump-type chiller cooling system utilizes a combination of water and air cooling. Its inlet water is deionized water supplied by the thermal power plant's boiler, which is at room temperature. After heat exchange, the water temperature rises and enters the power plant's boiler feed water system, with a heat exchange temperature difference of no less than 2°C. The air-cooled portion is cooled by the power plant's combustion air. After heat exchange, the combustion air enters the boiler, where the air-cooled heat exchanger utilizes a partition-type heat exchanger with a heat exchange temperature difference of no less than 2°C. By cooling the condenser with water and air in the chiller cooling system, the water and gas temperatures entering the boiler are increased, and waste heat generated by the chiller is recovered back into the boiler system, achieving a heat recovery efficiency exceeding 80%. The salt solution in the freeze crystallizer R remains in the crystallization chamber for more than two hours.

[0059] The sodium sulfate decahydrate precipitated from the freezing crystallization device R enters the re-dissolution tank N, and the re-dissolution water is the condensed water from the evaporation crystallizer M. The condensed water exits from the 54th port and enters the re-dissolution tank N from the 84th port of the evaporation crystallizer M.

[0060] The evaporation crystallizer M utilizes a reverse-circulation FC or Oslo crystallizer to produce large-particle anhydrous sodium sulfate. It utilizes positive pressure evaporation, with saturated steam exceeding 110°C entering the power plant at port 85. Secondary steam at a temperature of no less than 100°C is discharged at port 55, and mother liquor from the evaporation crystallization is discharged at port 42. This mother liquor is piped to port 41 of the adsorption device P. Anhydrous sodium sulfate exits the evaporation crystallizer M through the third outlet 56, with a moisture content of less than 5%. Secondary steam from port 55 enters port 57 of the steam ejector X, which then receives high-temperature, high-pressure steam from the power plant's boiler at port 59. Medium-pressure steam is discharged from port 60 of the steam ejector X for external steam supply. The steam at port 60 can meet production requirements for steam pressure and temperature, enabling external steam supply. Steam ejectors are mature technology and are commonly used in industrial production. The liquid discharged from the freezing crystallization device R is high brine mainly containing sodium chloride, which exits from port 61 and enters the sodium chloride evaporation crystallizer W from port 71.

[0061] The evaporation crystallizer Q uses a reverse circulation FC or Oslo crystallizer to produce large-particle sodium chloride. It employs positive pressure evaporation. Saturated steam no higher than 110°C enters the thermal power plant at port 86, and secondary steam at a temperature no lower than 100°C is discharged at port 89. This enters port 58 of the steam ejector X. Crystallized sodium chloride is discharged at port 73, condensed water is discharged at port 74, and mother liquor from evaporation crystallization is discharged at port 72, which enters port 41 of the adsorption device P. The moisture content of the crystallized sodium chloride is less than 5%.

[0062] The adsorption device P uses an adsorbent to adsorb sodium sulfate in the mother liquor. The port 41 entering the adsorption device P is connected to the port 42 from the evaporation crystallizer M through a pipeline. The mother liquor of the evaporation crystallizer Q is a saturated mother liquor, and its port 72 is connected to the port 41 of the adsorption device P through a pipeline. The sodium chloride and potassium chloride content in the evaporation crystallizer Q's outflow mother liquor is greater than 20%, and the sodium sulfate content is greater than 5%, which is in a saturated state. The solution enters the port 41 of the adsorption device P through the port 72, and is first adsorbed to separate the sodium sulfate. The port 40 of the adsorption device P is the inlet for the hydrochloric acid solution, and the port 39 is the outlet for the solid matter containing sodium sulfate, which enters the port 37 of the analytical device L for analysis. The adsorption device P uses zirconium hydroxide for adsorption, and the pH value of the solution is maintained between 4-6. The basic reaction is as follows;

[0063] 2ZrOOH2+Na2SO4+2HCl——[ZrOOH]2SO4+2NaCl+2H2O

[0064] [ZrOOH]2SO4 is solid. After solid-liquid separation and removal of most of the water, it enters the analysis device L.

[0065] The analytical device L reacts as follows:

[0066] [ZrOOH]2 SO4+ 2NaOH--- 2ZrOOH2+Na2SO4+2H2O

[0067] ZrOOH2 is an extremely insoluble substance that is recyclable and renewable, with virtually no one-time purchase costs, minimal pollution, and virtually no solid waste generated. After the reaction, the sulfate concentration in the salt solution is less than 2 ppm, indicating that adsorption is essentially complete.

[0068] The high-purity sodium sulfate solution after analysis is returned to the port 38 of the evaporation crystallizer M through the pipeline from the port 36 of the analysis device L, and evaporated and crystallized solid sodium sulfate in the evaporation crystallizer M.

[0069] The solution after adsorption by the adsorption device P is discharged from port 35 and enters port 75 of the freezing device V. The salt solution after adsorption is mainly composed of saturated sodium chloride and potassium chloride, and contains a small amount of other impurities. Since the solubility of potassium chloride changes greatly with temperature, the temperature of the salt solution in the freezing device V drops below 0°C, potassium chloride precipitates, and solid-liquid separation is achieved by the centrifuge of the freezing device V. The potassium chloride crystals are discharged from port 78 of the freezing device V.

[0070] The refrigeration unit V, consisting of a refrigerator, a cooling crystallizer, and a solid-liquid separator, utilizes a heat pump-type cooling device, a mature technology. The condenser in the heat pump-type refrigerator's cooling system utilizes a combination of water and air cooling. Its inlet water is deionized water supplied by the thermal power plant's boiler, which is at room temperature. After heat exchange, the water temperature rises and enters the power plant's boiler feed water system, with a heat exchange temperature difference of no less than 5°C. The air-cooled portion is cooled by the power plant's combustion-supporting air. After heat exchange, the combustion-supporting air enters the boiler, with the air-cooled heat exchanger utilizing a partition-type heat exchanger, with a heat exchange temperature difference of no less than 5°C.

[0071] Sodium hydroxide enters port 34 of the analytical device L, and analytical agent exits port 88 and enters port 77 of the adsorption device P, thus realizing the recycling of analytical agent. The freezing temperature of the freezing device V is below 0°C.

[0072] The second outlet 79 of the refrigeration device V is the cold liquid outlet, which enters the 80th port of the evaporation crystallizer W for evaporation and crystallization. The sodium chloride crystal salt is discharged from the 82th port, and the mother liquor of the evaporation and crystallization is returned to the 76th port of the refrigeration device V from the 81st port of the evaporation crystallizer W. A part of the trace mother liquor is discharged from the 83rd port of the evaporation crystallizer W and enters the fly ash and ash slag system of the power plant as a construction auxiliary material.

[0073] The boiling point of the evaporation crystallizer W is maintained above 11°C, and a multi-effect evaporator or an MVR evaporation crystallizer can be used. The evaporation crystallizer W adopts a first-level forced circulation evaporation crystallizer, and the type of the crystallizer can adopt an Oslo crystallizer or a DTB type or a reverse circulation FC type crystallizer.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A waste salt resource system based on the integration of energy conservation and environmental protection of thermal power plants, characterized by: include: Dryer A, dust removal and deacidification device B, vacuum device C, liquid-liquid heat exchanger D, solid-liquid heat exchanger E, high-temperature pyrolyzer F, negative pressure fan G, dust removal and deacidification device H, dissolution tank K, coagulation sedimentation tank J, filter press I, seed crystal precipitation device O, regulating tank S, oxidizer T, regulating tank U, freezing crystallization device R, back dissolution tank N, evaporation crystallizer M, steam ejector X, evaporation crystallizer Q, analysis device L, adsorption device P, freezing device V, evaporation crystallizer W, induced draft fan Z; wherein, the first inlet (1) of dryer A is the waste salt inlet, the first outlet (2) of dryer A is the outlet of the dried waste salt, which is connected to the first inlet (18) of high-temperature pyrolyzer F, and the second outlet (3) of dryer A is the outlet of the dry tail gas, which is connected to the dust removal and deacidification device. The first outlet (6) of the dust removal and deacidification device B is the outlet of the waste gas after dust removal and deacidification, and is connected to the inlet (7) of the vacuum device C. The second outlet (5) of the dust removal and deacidification device B and the first outlet (24) of the dust removal and deacidification device H are solid waste outlets, both of which are connected to the second inlet (19) of the high-temperature pyrolyzer F. The second outlet (25) of the dust removal and deacidification device H is the outlet of the waste gas after dust removal and deacidification), and is connected to the first inlet (91) of the induced draft fan Z through a pipeline. The non-condensable gas outlet (8) of the vacuum device C is connected to the second inlet (90) of the induced draft fan Z through a pipeline. The outlet (92) of the induced draft fan Z is a gas outlet, and the gas is introduced into the power plant boiler. The first outlet (20) of the high-temperature pyrolyzer F is the outlet of the pyrolysis gas. The inlet (21) of the negative pressure fan G is connected to the inlet (23) of the dust removal and deacidification device H. The second outlet (17) of the high-temperature pyrolyzer F is the outlet of hot waste salt and is connected to the first inlet (16) of the solid-liquid heat exchanger E. The first outlet (15) of the solid-liquid heat exchanger E is the outlet of the waste salt after cooling and is connected to the inlet (26) of the dissolution tank K. The second inlet (14) of the solid-liquid heat exchanger E is the inlet of water before heat exchange and is connected to the first outlet (11) of the liquid-liquid heat exchanger D. The second outlet (13) of the solid-liquid heat exchanger E is the outlet of water after heat exchange and is connected to the first inlet (12) of the liquid-liquid heat exchanger D. The second inlet (9) of the liquid-liquid heat exchanger D is the inlet of condensate discharged from the boiler. The second outlet ( 10) is the outlet of the condensed water after heating, and the condensed water returns to the boiler system of the power plant; the outlet (27) of the dissolving tank K is the outlet of the salt solution, which is connected to the first inlet (28) of the coagulation sedimentation tank J, the second inlet (29) of the coagulation sedimentation tank J is the dosing port, the first outlet (50) of the coagulation sedimentation tank J is the mud discharge port at the bottom, which is connected to the inlet (31) of the filter press I, the first outlet (32) of the filter press I is the discharge port of the clear liquid generated after the filtration, which is connected to the third inlet (30) of the coagulation sedimentation tank J, the second outlet (33) of the filter press I is the discharge port of the solid matter generated by the filtration, and the second outlet (47) of the coagulation sedimentation tank J is the discharge port of the salt solution after precipitation and clarification, which is connected to the first inlet (48) of the seed crystal precipitation device O;The second inlet (46) of the seed crystal precipitation device O is a dosing port, the first outlet (49) of the seed crystal precipitation device O is a seed crystal particle outlet, the second outlet (51) of the seed crystal precipitation device O is a water outlet, and is connected to the first inlet (52) of the regulating tank S; the second inlet (63) of the regulating tank S is a hydrochloric acid inlet, the outlet (64) of the regulating tank S is connected to the inlet (65) of the oxidizer T, the first outlet (68) of the oxidizer T is connected to the first inlet (69) of the regulating tank U, the second inlet (70) of the regulating tank U is a sodium hydroxide inlet, the outlet (66) of the regulating tank U is connected to the inlet (62) of the freezing crystallization device R, the first outlet (53) of the freezing crystallization device R is connected to the first inlet (45) of the re-dissolution tank N, the second inlet (84) of the re-dissolution tank N is a condensed water inlet, and is connected to the first outlet (54) of the evaporation crystallizer M, and the outlet (44) of the re-dissolution tank N is connected to the first inlet (43) of the evaporation crystallizer M. Then, the second outlet (61) of the freezing crystallizer R is a high-salt water outlet, which is connected to the first inlet (71) of the evaporation crystallizer Q; the second inlet (85) of the evaporation crystallizer M and the second inlet (86) of the evaporation crystallizer Q are steam inlets, the second outlet (55) of the evaporation crystallizer M and the first outlet (74) of the evaporation crystallizer Q are secondary steam outlets, which are respectively connected to the first inlet (57) of the steam ejector X and the second inlet (58) of the steam ejector X, the third outlet (42) of the evaporation crystallizer M and the second outlet (72) of the evaporation crystallizer Q are mother liquor discharge ports of evaporation crystallization, both of which are connected to the first inlet (41) of the adsorption device P, the third outlet (73) of the evaporation crystallizer Q is a crystallized salt outlet, the fourth outlet of the evaporation crystallizer Q is a condensed water outlet, the third inlet (59) of the steam ejector X is a high-pressure steam inlet, and the outlet (60) of the steam ejector X is an outlet for supplying steam outside the power plant;The second inlet (40) of the adsorption device P is the inlet of the hydrochloric acid solution. The first outlet (39) of the adsorption device P is the outlet of the solid matter containing sodium sulfate, which is connected to the first inlet (37) of the analytical device L. The second inlet (34) of the analytical device L is the inlet of sodium hydroxide. The first outlet (88) of the analytical device L is the outlet of the adsorbent, which is connected to the third inlet (77) of the adsorption device P. The second outlet (36) of the analytical device L is the outlet of the sodium sulfate solution after analysis, which is connected to the third inlet (38) of the evaporation crystallizer M. The second outlet (35) of the adsorption device P is the outlet of the solution after adsorption, which is connected to the second inlet (75) of the freezing device V. The first outlet (78) of the freezing device V is the crystal salt. The discharge outlet, the second outlet (79) of the freezing device V is connected to the first inlet (80) of the evaporation crystallizer W, the first outlet (82) of the evaporation crystallizer W is the outlet of the crystallized salt, the second outlet (81) of the evaporation crystallizer W is the outlet of the mother liquid of the evaporation crystallizer, and is connected to the third inlet (76) of the freezing device V, the third outlet (87) of the evaporation crystallizer W is the outlet of the mother liquid of the evaporation crystallizer, and the fourth outlet (83) of the evaporation crystallizer W is the outlet of the condensed water; the dryer A adopts one of an electrically heated rotary kiln, an electrically heated rake furnace, and an electrically heated drum dryer A; the solid-liquid heat exchanger E adopts a water-cooled drum slag cooler or a disc slag cooler; the liquid-liquid heat exchanger D adopts a plate or shell-and-tube heat exchanger.

2. A method for recycling waste salt based on the system according to claim 1, characterized in that: The process includes the following: The waste salt is sent to the dryer A for drying. The drying temperature in the dryer A is controlled between 100°C and 300°C. The dryer A adopts a vacuum drying method with a vacuum degree between 0.008MPa and 0.01MPa. The dry exhaust gas generated by dryer A is treated by dust removal and deacidification device B. The specific process is as follows: dust removal and deacidification device B uses a high-temperature resistant composite filter cartridge dust collector. The filter element of the high-temperature resistant composite filter cartridge dust collector is made of inorganic silicate composite materials. The core of the high-temperature resistant composite filter cartridge dust collector is built with a vanadium-titanium catalyst. The vanadium-titanium catalyst serves as a desulfurization and denitrification catalyst and reduces nitrogen oxides in the dry exhaust gas to nitrogen. The dust removal and deacidification device B removes hydrogen chloride, sulfide gas, and hydrogen fluoride gas from the flue gas by adding an alkaline agent. The alkaline agent is sodium hydroxide, sodium carbonate, or calcium hydroxide. The operating temperature of the dust removal and deacidification device B is between 30°C and 600°C. The gas treated by the dust removal and deacidification device B is driven by the vacuum device C. The deacidified gas enters the power plant boiler through the induced draft fan Z and is burned. The dried waste salt enters the high-temperature pyrolyzer F for pyrolysis. The high-temperature pyrolyzer F performs pyrolysis in an oxygen-free state. The pyrolysis temperature of the high-temperature pyrolyzer F is controlled between 300°C and 600°C, with the instantaneous maximum temperature not exceeding 1000°C. A continuous feeding and continuous discharging production method is adopted. The pyrolysis gas generated by the high-temperature pyrolyzer F passes through the negative pressure fan G and enters the dust removal and deacidification device H for dust removal and deacidification treatment. The gas treated by the dust removal and deacidification device H enters the power plant boiler. The dust removal and deacidification device H adopts a high-temperature resistant composite filter cartridge dust collector. The filter element of the high-temperature resistant composite filter cartridge dust collector adopts an inorganic silicate composite material. The core of the high-temperature resistant composite filter cartridge dust collector is built with a vanadium-titanium catalyst. The vanadium-titanium catalyst is a kind of desulfurization and denitrification catalyst, which reduces nitrogen oxides in the dry exhaust gas to nitrogen. The acid gas content at the outlet of the dust removal and deacidification device B and the dust removal and deacidification device H is less than 5 mg / L, and the dust content is less than 3 mg / L; The solid waste generated by the dust removal and deacidification device B and the dust removal and deacidification device H is sodium sulfate, sodium chloride, sodium fluoride, or a mixture containing a small amount of sodium nitrate, some dust, or a mixture of calcium salts. The waste salt after pyrolysis produced by the high-temperature pyrolyzer F enters the solid-liquid heat exchanger E and exchanges heat with water from the liquid-liquid heat exchanger D. The waste salt cooled by heat exchange enters the dissolution tank K for dissolution. The water heated by heat exchange enters the liquid-liquid heat exchanger D and exchanges heat with condensate from the power plant boiler in the liquid-liquid heat exchanger D. The condensate heated by heat exchange returns to the boiler system, realizing the recovery of high-temperature heat in the waste salt into the boiler. The inlet salt temperature of the solid-liquid heat exchanger E is lower than 700°C and the outlet salt temperature is lower than 100°C; The condensate temperature entering the boiler through the liquid-liquid heat exchanger D is lower than 100°C, and the outlet water temperature is lower than 100°C; The hazardous waste salts from the solid-liquid heat exchanger E enter the dissolution tank K. The salt solution in the dissolution tank K enters the coagulation sedimentation tank J, where it reacts with the added coagulant, flocculant, heavy metal remover, and sodium hydroxide. The divalent or higher cations of magnesium ions in the solution combine with hydroxide to form insoluble matter, and the heavy metals in the solution are adsorbed and chelated. Under the action of the coagulant, flocculation and sedimentation are formed and deposited at the bottom of the coagulation sedimentation tank J. The mud at the bottom of the coagulation sedimentation tank J enters the filter press I under the action of the mud pump for pressure filtration separation. The salt solution clarified by the precipitation in the coagulation sedimentation tank J enters the seed crystal precipitation device O. Calcium carbonate seeds and sodium carbonate reagent are introduced into the seed crystal precipitation device O. The principle of induced crystallization is used to achieve a reaction between sodium carbonate and calcium ions in the waste salt to form granular calcium carbonate. The granular calcium carbonate is recycled into the desulfurization system of the power plant as a desulfurizer; After the salt solution from the seed crystal precipitation device O enters the regulating tank S, hydrochloric acid is used in the regulating tank S to adjust the pH to between 5 and 7, and then enters the oxidizer T for oxidation treatment. The salt solution oxidized by the oxidizer T enters the regulating tank U, and sodium hydroxide is used in the regulating tank U to adjust the pH to above 7, and then enters the freeze crystallization device R; The oxidizer T uses electrolytic oxidation to oxidize and decompose the residual organic matter in the salt solution into carbon dioxide and water, and oxidize the nitrogen oxides in the salt solution into nitrogen; The freezing crystallization device R freezes and precipitates the sodium sulfate in the salt solution, and the obtained sodium sulfate decahydrate solid enters the re-dissolution tank N. The solution in the re-dissolution tank N enters the evaporation crystallizer M; evaporation crystallization is performed to obtain anhydrous sodium sulfate. The high brine produced by the freezing crystallization device R enters the evaporation crystallizer Q; evaporation crystallization is performed to obtain sodium chloride. The freezing temperature of the freezing crystallization device R is below 0°C, and the salt solution stays in the freezing crystallization device R for more than 2 hours. The refrigeration device V adopts a heat pump type refrigeration unit; The adsorption device P uses an adsorbent to adsorb sodium sulfate in the mother liquor. The adsorbent uses zirconium hydroxide. The pH value of the solution in the adsorption device P is maintained between 4 and 6. The adsorption device P discharges a solid compound formed by the reaction of zirconium hydroxide and sodium sulfate. At this time, the solution in the adsorption device P does not contain sodium sulfate. The solid matter and a trace amount of solution enter the analysis device L for analysis. The sodium sulfate solution after analysis by the analysis device L enters the evaporation crystallizer M. The solution after adsorption by the adsorption device P enters the freezing device V for low-temperature freezing crystallization to precipitate potassium chloride. The desorbent L adds sodium hydroxide to reduce the desorbent, and the reduced desorbent returns to the adsorption device P to achieve desorbent recycling; The adsorption device P discharges a solution mainly containing sodium chloride and potassium chloride into the freezing device V and then into the evaporation crystallizer W; evaporation and crystallization are carried out to obtain sodium chloride crystal salt, and part of the mother liquor of the evaporated crystallization is returned to the freezing device V, and the other part is discharged. The boiling point of the evaporation crystallizer W is maintained above 11°C; the evaporation crystallizer W adopts the FC reverse cycle evaporation crystallizer type or the Oslo evaporation crystallizer type.

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