Waste incineration fly ash high-temperature dry-process stage treatment recycling system and method

Abstract

The invention discloses a waste incineration fly ash high-temperature dry-method stage treatment recycling system and method, and belongs to the technical field of solid waste treatment. The system comprises a high-temperature volatilization reactor, a high-temperature dust removal device, a multi-stage gradient condensation device and a main control system, and the stage treatment process is as follows: fly ash and a regulator are mixed and then are heated in the high-temperature volatilization reactor at 800-1200 DEG C, so that dioxin is removed, and soluble salts and heavy metal chlorides are volatilized into gas states, so that the fly ash is obtained. The high-temperature flue gas passes through a high-temperature dust removal device to intercept a desalted fly ash matrix under the condition of 500-800 DEG C, and purified gas sequentially enters a multi-stage gradient condensation device; the heavy metal condensation unit, the potassium chloride condensation unit and the sodium chloride condensation unit are used for realizing fractional condensation separation of heavy metals, potassium chloride and sodium chloride. The method has the advantages of zero discharge of wastewater, high purity of salt products, short process flow, low energy consumption, less generation of hazardous wastes, 70-90% of potassium chloride recovery rate, 65-85% of sodium chloride recovery rate, and no less than 90% of fly ash matrix resource utilization rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste treatment, in particular to a garbage incineration fly ash high-temperature dry method graded treatment resource system and method. BACKGROUND

[0002] Garbage incineration fly ash is a fine particulate matter produced in the process of incineration of household garbage, containing a large amount of heavy metals (such as lead, cadmium, zinc, etc.) and soluble salts (such as potassium chloride, sodium chloride, etc.), and belongs to hazardous waste. According to the National Hazardous Waste List, fly ash is listed as HW18 hazardous waste, with an annual production of more than 5 million tons, and a treatment cost of 800-1500 yuan / ton. The traditional fly ash treatment method mainly includes cement solidification landfill and chelating agent stabilization, but there are problems such as occupation of land resources, long-term environmental risk, and inability to recover valuable components.

[0003] In recent years, the FAST process (fly ash desalination and heavy metal removal technology) adopts the technical route of "wet leaching + evaporation crystallization + incineration solidification", first uses water to wash out the soluble salts and part of the heavy metals in the fly ash to form a leaching solution, then separates potassium chloride and sodium chloride through multi-effect evaporation crystallization, and the residue is returned to the incinerator for cooperative thermal treatment. Although this process realizes a certain degree of resource utilization, it has the following technical defects: (1) A large amount of process wastewater is produced, 2-3 tons of water are needed to treat 1 ton of fly ash, and the subsequent water treatment and multi-effect evaporation crystallization energy consumption is as high as 200-300 kWh / ton of fly ash; (2) The leaching solution is complex, containing not only target salts but also sulfates, heavy metal ions, and organic matter, and the purity of the salt products obtained by evaporation crystallization is only 60-75%, which is difficult to reach the industrial grade standard of ≥95%, and the resource value is limited; (3) The desalination process produces 20-30% of hazardous waste of mixed salt, which contains a variety of heavy metals and complex salts that cannot be separated, and still needs to be disposed as hazardous waste, with high treatment cost; (4) The process flow is long, including leaching, solid-liquid separation, multi-effect evaporation, crystallization, centrifugal dewatering, etc. more than ten procedures, equipment investment is large, about 30-50 million yuan / 100 tons / day scale, occupies an area of about 2000-3000 square meters, and operation and maintenance are complex; (5) The system stability is poor, the evaporator is easy to scale and block, frequent cleaning and maintenance are needed, and the actual operation rate is only 70-80%.

[0004] Therefore, developing a fly ash treatment technology with shorter process flow, lower energy consumption, higher product purity, and zero wastewater discharge is an urgent need to realize fly ash resource utilization and "waste-free city" construction. SUMMARY

[0005] The purpose of the present application is to provide a waste incineration fly ash high-temperature dry method grading treatment resource system and method to solve the problems raised in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The present application provides a waste incineration fly ash high-temperature dry method grading treatment resource system and method to solve the problems of complex fly ash treatment process, high energy consumption, low product purity, and secondary pollution in the prior art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions: According to the first aspect of the embodiment of the present application, a waste incineration fly ash high-temperature dry method grading treatment resource system is provided, which comprises a high-temperature volatilization reactor, a high-temperature dust removal device, a multi-stage gradient condensing device, and a main control system. The high-temperature volatilization reactor has a fly ash feed inlet, an adjusting agent adding port, a heating device, and a high-temperature flue gas outlet. Under the condition of 800-1200℃, through the dioxin pyrolysis mechanism and condition optimization, efficient removal is ensured, so that dioxin is removed by pyrolysis or oxidation decomposition at high temperature, and the removal rate is ≥99.9%. At the same time, the soluble salts and heavy metal chlorides in the fly ash are volatilized into a gaseous state. The gas inlet of the high-temperature dust removal device is connected with the high-temperature flue gas outlet of the high-temperature volatilization reactor. The high-temperature dust removal device comprises a metal filter bag dust collector or a ceramic filter tube dust collector, which is used to intercept the fly ash matrix from which the salts and heavy metals have been removed under the condition of 500-800℃. The high-temperature dust removal device is provided with a solid discharge port and a purified gas outlet. The gas inlet end of the multi-stage gradient condensing device is connected with the purified gas outlet of the high-temperature dust removal device. The multi-stage gradient condensing device comprises a heavy metal condensing unit, a potassium chloride condensing unit, and a sodium chloride condensing unit connected in series. Each condensing unit is respectively provided with an independent temperature control system and a solid collecting device. The main control system is electrically connected with the high-temperature volatilization reactor, the high-temperature dust removal device, and the multi-stage gradient condensing device, respectively, for monitoring and controlling the operating parameters of each device.

[0008] Preferably, the dioxin pyrolysis / oxidation decomposition mechanism refers to a process of being completely destroyed through two paths at high temperature: Specifically as follows: one, pyrolysis decomposition mechanism (under anoxic or anaerobic conditions) Pyrolysis refers to a process in which dioxin (PCDD / Fs) molecules are broken down into low-molecular-weight compounds by absorbing heat energy in an oxygen-free or low-oxygen high-temperature environment.

[0009] Specific steps: (1) Absorbing heat energy to activate: under the condition of 800-1200℃, dioxin molecules absorb heat, and molecular vibration is intensified; The C-O ether bond with lower energy (bond energy about 360 kJ / mol) is preferentially broken, forming a phenoxy radical; Radical chain reaction: phenoxy radicals further crack to form intermediate products such as chlorobenzene, chlorophenol, etc. Intermediate products continue to dechlorinate and ring-open at high temperatures, eventually decomposing into: Small molecule gases: CO, CO2, H2, HCl Carbonaceous residue: trace amounts of carbon black or polycyclic aromatic hydrocarbons (further gasification at higher temperatures) (3) Temperature-time synergistic effect: 800-900℃: dioxin molecules are initially cracked, requiring a longer residence time (≥2 seconds); 950-1200℃: molecules are completely cracked into small molecules, with residence time shortened to 0.5-1 seconds.

[0010] Pyrolysis conditions: oxygen concentration <2%, relying on high temperature to directly destroy molecular structure without combustion reaction.

[0011] Dioxygenated decomposition mechanism (under aerobic conditions) Oxidative decomposition refers to the process of dioxin being completely mineralized into inorganic substances through radical oxidation in the presence of oxygen. The specific path is: (1) Initial oxidation stage: oxygen produces active oxygen radicals (O•, OH•) at high temperatures; Radicals attack C-H bonds and C-Cl bonds in dioxin molecules, forming peroxide intermediates; (2) Deep oxidation stage: intermediates undergo dechlorination-ring opening-oxidation three-step reactions: ① Dechlorination: Cl atoms are replaced by OH• to form hydroxylated derivatives; ② Ring opening: benzene ring breaks under oxygen attack to form straight-chain carboxylic acid compounds; ③ Complete oxidation: carboxylic acids are further oxidized into final products: Complete mineralization products: CO2, H2O, HCl Byproducts: trace amounts of CO (which can be further oxidized under sufficient oxygen concentration) (3) Key role of oxygen concentration: oxygen concentration 3-6%: oxidation reaction is dominant, with highest decomposition efficiency; Oxygen concentration >8%: NOx byproducts may be produced, requiring control of upper limit of oxygen concentration.

[0012] Oxidation conditions: oxygen concentration 2-8%, temperature above 850℃, utilizing radical reactions to achieve complete mineralization.

[0013] In this system, chlorobenzene / chlorophenol intermediates produced by pyrolysis are in contact with oxygen in the gas stream and are rapidly oxidized. The heat released by the oxidation reaction in turn promotes temperature rise in the pyrolysis zone, ultimately achieving a synergistic effect of dioxin removal rate ≥99.9%.

[0014] Preferably, the working temperature of the heavy metal condensing unit is 400-650℃, which is used for condensing zinc chloride, lead chloride, cadmium chloride and other high-boiling heavy metal chlorides; the working temperature of the potassium chloride condensing unit is 250-400℃, which is designed based on the optimal condensing temperature window of potassium chloride in the range of 300-350℃; the working temperature of the sodium chloride condensing unit is 150-250℃, which utilizes the boiling point difference of about 50-100℃ between sodium chloride and potassium chloride to realize fractional separation.

[0015] Preferably, the heavy metal condensing unit includes a high-temperature condenser, a heavy metal collection hopper, a first cyclone separator and a first ceramic filter, the inner wall of the high-temperature condenser is provided with corrugated or honeycomb condensing promoting lining plates, the surface area is 3-5 times that of a smooth tube, and the bottom of the heavy metal collection hopper is provided with a high-temperature resistant rotary valve or a star-shaped unloader; the potassium chloride condensing unit includes a medium-temperature condenser, a nucleation promoting device, a second cyclone separator, a second ceramic filter and a potassium chloride collection bin, the nucleation promoting device adopts an airflow jet mixer to uniformly disperse inert carrier particles into the airflow, the particle size is 5-50 microns, and the addition amount is 0.1-1% of the theoretical precipitation amount of potassium chloride; the sodium chloride condensing unit includes a low-temperature condenser, a mechanical ash removal device, a third cyclone separator, a third ceramic filter and a sodium chloride collection bin, and the mechanical ash removal device includes a spiral scraper, an electromagnetic vibrator or a sonic soot blower.

[0016] Preferably, the high-temperature dust removal device adopts a metal filter bag dust remover, the metal filter bag is made of sintered metal fiber or metal felt, the material is 316L stainless steel, Inconel 600 or FeCrAl alloy, the pore size is 0.5-5 microns, and the air permeability is 50-200 L / m²·min, which can be stably operated for a long time under the condition of 500-900℃; the metal filter bag dust remover is equipped with a high-temperature pulse back-blowing ash removal system, the ash removal gas source temperature is 300-500℃, the pressure is 0.4-0.8 MPa, and the pulse width is 0.05-0.3 seconds.

[0017] Preferably, the heat transfer medium of each condensing unit of the multi-stage gradient condensing device adopts molten salt or high-temperature heat conducting oil, the molten salt is a mixture of sodium nitrate and potassium nitrate or a mixture of carbonates, and the use temperature range is 200-600℃; the high-temperature heat conducting oil is a mixture of diphenyl-diphenyl ether or a synthetic heat conducting oil, and the use temperature range is 100-400℃; precise control of the temperature of each stage is realized through a precision proportional regulating valve and a cascade PID controller, the temperature fluctuation range is ≤±3℃, and the response time is ≤30 seconds.

[0018] Preferably, the system further comprises a flue gas co-processing device, which comprises a quench tower, an alkali washing tower, a bag filter and an induced draft fan. The gas inlet of the quench tower is connected to the tail gas outlet of the sodium chloride condensation unit, for rapidly cooling the tail gas from 150-200°C to below 70°C. The alkali washing tower uses sodium hydroxide or calcium hydroxide solution to absorb HCl, SO2 and other acidic gases, with an absorption efficiency of ≥95%. The bag filter uses a coated filter bag with a filtration accuracy of ≤5 microns to remove residual particulate matter.

[0019] Preferably, the high-temperature volatilization reactor is a vertical or horizontal rotary kiln structure with an inner diameter of 1.5-4 meters and a length of 6-15 meters. A multi-layer paddle or rake stirring device is arranged inside, with a rotation speed of 5-30 rpm. The adjusting agent is one or more of calcium chloride, magnesium chloride, sodium chloride or potassium chloride, with an addition amount of 3-20% of the mass of fly ash. The heating device is a burner, an electric heater or a waste heat exchanger using high-temperature flue gas from an incinerator.

[0020] Preferably, the system further comprises a detection system, which comprises: (1) Temperature detection: K-type or N-type armored thermocouples are used, with a measurement range of 0-1200°C and an accuracy of ±0.5%. They are arranged at key positions of the high-temperature volatilization reactor, the high-temperature dust removal device and each stage of the condensation unit. (2) Pressure detection: High-temperature pressure transmitters are used, with a measurement range of -10 kPa to +100 kPa and an accuracy of ±0.2%. They are used to monitor the pressure distribution of the system and the pressure difference of the dust remover. (3) Flow detection: Thermal mass flow meters or Venturi flow meters are used, with a measurement range of 500-50000 Nm³ / h and an accuracy of ±2%. They are used to monitor the flue gas flow. (4) Gas composition analysis: Online infrared gas analyzers or mass spectrometers are used to detect the concentrations of HCl, SO2, O2, CO, CO2 and other gases in real time. (5) Particulate matter monitoring: Laser particle size analyzers or light scattering dust meters are used to measure the particle size distribution and concentration of condensed particles. (6) Heavy metal monitoring: An online heavy metal monitoring system (such as ICP-MS) is installed at the tail gas discharge port to monitor the emission concentrations of lead, cadmium, mercury and other heavy metals.

[0021] Preferably, each condensation unit of the multi-stage gradient condensation device is made of corrosion-resistant alloy material. High-nickel alloys such as Hastelloy C-276, Inconel 625 or Incoloy 800HT are used in the high-temperature section (400-800°C). 316L or 317L stainless steel is used in the medium-temperature section (200-400°C), with a lining of silicon nitride ceramic or silicon carbide ceramic. 2205 or 2507 duplex stainless steel is used in the low-temperature section (100-250°C), with a lining of polytetrafluoroethylene or glass flake coating.

[0022] Preferably, both the potassium chloride condensing unit and the sodium chloride condensing unit adopt a modular parallel design. Each unit includes 2-4 parallel condensing modules. Each module can operate and switch independently. When one module is cleaned online or maintained offline, the other modules continue to operate, ensuring that the system has a continuous and stable operating rate of ≥95%.

[0023] Preferably, the system also includes a heat recovery device for recovering sensible and latent heat released during multi-stage condensation. The heat recovery device includes a waste heat boiler or a thermal oil heater, which uses the recovered heat to preheat fly ash, heat regulators, generate steam, or supply heating for the plant area. The heat recovery efficiency is ≥60%, which can reduce the total energy consumption of the system by 20-35%.

[0024] Preferably, the main control system adopts a distributed control system (DCS) or a programmable logic controller (PLC), equipped with an industrial touch screen human-machine interface, and has the following functions: (1) Real-time monitoring of process parameters and recording of historical trends, with a data acquisition cycle of ≤1 second and historical data retention of ≥1 year; (2) Multi-level alarm function, including early warning, first-level alarm, second-level alarm and emergency stop, with an alarm response time of ≤2 seconds; (3) Equipment interlock protection, such as automatic shut-off of heating when the temperature exceeds the limit, automatic enhanced dust removal when the pressure difference of the dust collector is too high, and automatic adjustment of the heat exchange medium flow rate when the temperature of the condenser deviates. (4) Automatic start-stop program control, including multiple operation modes such as cold start, hot start, normal stop, and emergency stop; (5) Adaptive optimization of process parameters: Based on fuzzy control or neural network algorithm, the temperature, residence time and other parameters of each section are automatically adjusted according to the changes in fly ash composition and processing volume. (6) Production data statistics and analysis, automatically generating daily and monthly reports, and calculating key indicators such as material balance, energy balance, recovery rate, and energy consumption; (7) Remote monitoring and diagnostics, supporting remote access and expert diagnostics via the Internet or Industrial Ethernet.

[0025] According to a second aspect of the present invention, a method for resource recovery from high-temperature dry grading of waste incineration fly ash is proposed, comprising the following steps: S1. Fly ash pretreatment: The fly ash from waste incineration is mixed with a regulator at a mass ratio of 100:(3-20) and mixed evenly using a twin-shaft or tri-shaft screw mixer for 3-10 minutes, with a mixing uniformity ≥95%. The mixed material is then fed into a high-temperature volatilization reactor via a screw feeder or pneumatic conveying system at a feed rate of 300-3000 kg / h, maintaining a continuous and stable feed rate. S2. High-temperature volatilization: The mixture is heated to 800-1200℃, preferably 850-1000℃, in a high-temperature volatilization reactor and held at this temperature for 20-90 minutes, preferably 30-60 minutes. Under stirring, dioxins in the fly ash are completely removed through pyrolysis or oxidative decomposition (oxygen concentration controlled at 2-8%), with a removal rate ≥99.9%. Simultaneously, regulators such as calcium chloride react with heavy metal oxides to generate volatile chlorides, for example: PbO + 2HCl → PbCl2↑ +H2O, allowing potassium chloride, sodium chloride, and heavy metal chlorides in the fly ash to fully volatilize into a gaseous state, with a volatilization rate ≥75%, preferably ≥85%. A slight negative pressure is maintained in the reactor, with a pressure of -50 to -500 Pa, to prevent leakage of harmful gases. S3. High-temperature dust removal: After volatilization, the high-temperature flue gas enters the high-temperature dust removal device through the high-temperature flue gas outlet. The flue gas temperature is 700-1000℃, and the flow rate is 3000-30000 Nm³ / h. Under the condition of 500-800℃, the fly ash matrix that has been desalted and heavy metals removed is intercepted through metal filter bags or ceramic filter tubes. The filtration velocity is 0.6-1.5 m / min, and the filtration efficiency is ≥99.5%. The intercepted fly ash matrix is ​​discharged through the solid discharge port. The discharge method is intermittent or continuous, and the collection volume is about 40-75% of the original fly ash volume. The sodium chloride content in this fly ash matrix is ​​<3%, the potassium chloride content is <2%, and the leaching toxicity of heavy metals is reduced by 75-90%. It can be directly utilized as a resource or further processed. S4. Heavy metal separation: The purified gas temperature is 700-900℃. After entering the heavy metal condensation unit, it is cooled by a heat exchange medium, with the temperature controlled at 400-650℃, preferably 450-550℃, and the cooling rate is 50-200℃ / min. The gas is preferentially condensed to match the boiling point windows of heavy metal chlorides, such as zinc chloride (boiling point 732℃), lead chloride (boiling point 950℃), and cadmium chloride (boiling point 960℃). The precipitated heavy metal particles are collected by a cyclone separator and a ceramic filter, with a collection efficiency ≥95%. The heavy metal content in the heavy metal condensate is ≥25%, preferably ≥35%, and can be used as a raw material for the extraction of valuable metals. S5. Potassium chloride recovery: The gas continues to cool and enters the potassium chloride condensation unit, with the temperature precisely controlled between 250-400℃, preferably 280-350℃. This temperature range is the optimal condensation window for potassium chloride, at which point a large amount of potassium chloride precipitates while sodium chloride remains mainly in a gaseous state. Inert carrier particles are injected into the gas flow through a nucleation promotion device at a rate of 0.1-1% of the theoretical potassium chloride precipitation amount, promoting the formation of uniform potassium chloride particles with a diameter of 50-300 micrometers for subsequent collection. The condensed potassium chloride particles are separated and collected by a cyclone separator and a ceramic filter, with a collection efficiency ≥97%. The purity of the collected potassium chloride product is ≥80%, preferably ≥88%, with sodium chloride content ≤15%, heavy metal content ≤0.8%, and moisture ≤2%, meeting the industrial-grade potassium chloride standard (GB / T 6549). The potassium chloride recovery rate is 70-90% of the potassium chloride content in the original fly ash. S6. Sodium chloride recovery: The gas temperature is further reduced to 150-250℃, preferably 180-220℃, and then enters the sodium chloride condensation unit. Sodium chloride condenses into a solid state within this temperature range, achieving fractional separation using its boiling point difference with potassium chloride. However, this process easily leads to scale buildup on the heat exchange surface. A mechanical cleaning device is activated, with a spiral scraper rotating continuously at 5-15 rpm to promptly remove accumulated salt from the pipe walls. An electromagnetic vibrator or sonic soot blower operates automatically every 1-5 hours for 5-15 minutes each time, with a vibration frequency of 50-200Hz to prevent salt layer caking. The collected sodium chloride product has a purity ≥75%, preferably ≥82%, with potassium chloride content ≤18%, heavy metal content ≤1.5%, and moisture content ≤3%. It can be used as industrial salt, de-icing agent, or raw material for the chlor-alkali industry. The sodium chloride recovery rate is 65-85% of the original sodium chloride content in the fly ash. S7. Tail Gas Treatment: The tail gas temperature after three-stage condensation is approximately 100-200℃, with main components of N2, O2, CO2, and H2O. It contains trace amounts of uncondensed heavy metal vapors (concentration <10mg / Nm³) and acidic gases (HCl concentration <500mg / Nm³, SO2 concentration <300mg / Nm³). The tail gas first passes through a quench tower, where atomized water or circulating cooling water is sprayed in to rapidly reduce the temperature to 60-80℃ within 0.5-2 seconds, simultaneously condensing residual heavy metal vapors into fine particles. It then enters an alkaline scrubbing tower, where a 5-15% sodium hydroxide solution or lime slurry is counter-currently sprayed at a liquid-to-gas ratio of 2-8L / m³ and a residence time of 3-8 seconds to absorb HCl and SO2 with an absorption efficiency ≥95%. Finally, it passes through a bag filter to remove fine particles with a dust removal efficiency ≥99.9%. The treated tail gas meets or exceeds GB standards in all aspects. The 18485-2014 Standard for Pollution Control of Municipal Solid Waste Incineration requires that: particulate matter ≤20mg / Nm³ (standard value 30mg / Nm³), HCl ≤40mg / Nm³ (standard value 60mg / Nm³), SO2 ≤80mg / Nm³ (standard value 100mg / Nm³), and heavy metals (Pb+Cd+Cr+Cu+Mn+Ni+As) ≤0.8mg / Nm³ (standard value 1.0mg / Nm³); clean exhaust gas is discharged from a 20-30 meter high chimney by an induced draft fan or returned to the incinerator for secondary combustion.

[0026] Preferably, in step S1, the regulator is calcium chloride with a purity ≥90% and an addition amount of 8-12% of the fly ash mass. When the sulfur content in the fly ash is high (>3%), the addition amount of calcium chloride can be appropriately increased to 12-15%. When the alkali metal content in the fly ash is high (>30%), the addition amount can be appropriately reduced to 5-8%.

[0027] Preferably, in step S2, the specific reaction mechanism of high-temperature volatilization includes: (1) The regulator reacts with sulfates and carbonates in fly ash to form volatile chlorides: CaSO4 + CaCl2 → CaO + CaCl2·CaSO4 (transition state) → 2CaO + SO2↑ + Cl2↑ CaCO3 → CaO + CO2↑ Na2SO4 + CaCl2→ CaSO4↓ + 2NaCl↑ (2) The hydrogen chloride atmosphere provided by the regulator promotes the conversion of heavy metal oxides into volatile chlorides: PbO + 2HCl → PbCl2↑ + H2O ZnO + 2HCl → ZnCl2↑ + H2O CdO + 2HCl → CdCl2↑ + H2O CuO + 2HCl → CuCl2↑ + H2O Alkali metal chlorides partially volatilize at high temperatures. Although their boiling points are relatively high (KCl 1420℃, NaCl 1465℃), they form a eutectic mixture in the presence of water vapor and hydrogen chloride, thus volatilizing prematurely. The effective volatilization temperature is reduced to 800-1000℃.

[0028] Preferably, in step S3, when the differential pressure of the metal filter bag dust collector reaches a set threshold (usually 2-3 times the initial differential pressure, about 800-1500 Pa), or at a set time interval (30-90 minutes), the high-temperature pulse backflushing cleaning system is automatically started; the cleaning is carried out in a compartment-by-compartment rotation manner, cleaning one compartment at a time, closing the air inlet valve of that compartment during cleaning, and the cleaning duration is 1-5 minutes, after which normal filtration is restored; the cleaning air source is heated compressed air or nitrogen, with a temperature of 300-500℃, a pressure of 0.4-0.8 MPa, a pulse width of 0.05-0.3 seconds, and a pulse interval of 5-30 seconds.

[0029] Preferably, in steps S4-S6, the temperature of each condensation unit is automatically adjusted by the main control system according to the following parameters: (1) The inlet flue gas temperature and flow rate are monitored in real time by thermocouples and flow meters; (2) The concentrations of potassium chloride and sodium chloride in the inlet flue gas are estimated by an online gas analyzer or based on the composition and volatility of fly ash; (3) The outlet gas temperature and particulate matter concentration serve as feedback signals for the condensation effect; (4) Product collection quantity and purity are used as comprehensive evaluation indicators of system performance; The control system employs cascade PID or fuzzy control algorithms to automatically adjust the flow rate and temperature of the heat exchange medium, achieving precise temperature control and adaptive optimization of each condensation unit, ensuring optimal separation performance and product quality under different operating conditions.

[0030] Preferably, in step S7, the waste alkaline solution generated by the alkaline washing tower contains sodium chloride, sodium sulfite, sodium sulfate, and a small amount of heavy metals. After the heavy metals are removed by precipitation or filtration, the waste solution can be treated in the following way: (1) Evaporation and concentration to produce mixed salt products, which are used as de-icing agents or chemical raw materials; (2) After neutralization, it enters the sewage treatment system and is discharged in compliance with standards; (3) Return to the waste incinerator as a combustion aid, and use the high temperature inside the furnace to completely decompose organic matter and fix heavy metals.

[0031] Preferably, the dust collected by the bag filter mainly consists of uncondensed salts and heavy metals, with a collection amount of about 1-3% of the original fly ash. It can be returned to step S1 for reprocessing or subjected to separate stabilization treatment.

[0032] The material and energy balance of this method are as follows: Material balance (taking the treatment of 1000 kg of fly ash as an example, fly ash composition: KCl 15%, NaCl 20%, heavy metal oxides 5%, the remainder being inert components): Input: 1000kg fly ash + 100kg calcium chloride regulator = 1100kg Output: Fly ash matrix: 550-650 kg (containing inert components such as CaO, SiO2, and Al2O3) Heavy metal concentrate: 30-50 kg (containing ≥35% of Pb, Zn, Cd, Cu, etc.) Potassium chloride product: 110-135kg (purity ≥88%) Sodium chloride product: 140-170kg (purity ≥82%) System losses and solid waste from exhaust gas treatment: 30-50 kg Gas emissions: SO2, CO2, H2O, etc., approximately 150-200 kg Total material balance: 1100kg ≈ (550-650) + (30-50) + (110-135) + (140-170) + (30-50) + (150-200) = 1010-1255kg. Considering measurement error and sampling loss, the balance rate is 92-98%.

[0033] Energy balance (taking a 100-ton / day scale unit as an example): Energy input: High-temperature volatilization heating: 2500-3500 kWh / ton of fly ash (depending on initial and target temperatures) System operating power consumption: 150-250 kWh / ton of fly ash (including fans, pumps, agitators, control systems, etc.) Total energy consumption: 2650-3750 kWh / ton fly ash Energy output and recovery: Multi-stage condensation sensible heat recovery: 800-1200 kWh / ton of fly ash Latent heat recovery of condensation: 400-600 kWh / ton of fly ash Waste heat recovery from exhaust gas: 150-250 kWh / ton of fly ash Total recovery: 1350-2050 kWh / ton of fly ash Net energy consumption: 1300-2400 kWh / ton of fly ash, significantly lower than the 2500-3500 kWh / ton of fly ash (including evaporation and crystallization energy consumption) of the traditional FAST process.

[0034] Compared with existing technologies, this invention achieves efficient fractional separation of matrix, heavy metals and salts in fly ash through a combination of high-temperature dry volatilization, high-temperature dust removal and multi-stage gradient condensation, and has the following significant advantages: (1) It truly achieves zero wastewater discharge, completely avoiding the large amount of process wastewater (2-3 tons of water / ton of fly ash) generated by wet process and the subsequent water treatment and evaporation crystallization energy consumption (200-300kWh / ton of fly ash), which meets the requirements of "zero waste city" and circular economy development. (2) The purity of salt products is significantly improved. Through precise temperature gradient control, the physical fractional condensation of potassium chloride and sodium chloride is achieved, increasing the product purity from 60-75% in the wet process to 80-92%, reaching industrial-grade standards, and increasing the resource value by 50-100%. (3) Significantly reduce the amount of hazardous waste generated. The leaching toxicity of heavy metals in the treated fly ash is reduced by 75-90%, and about 50-65% of the original fly ash can be directly utilized as a resource. Heavy metals are enriched separately (accounting for 3-5% of the original fly ash), which facilitates further extraction or safe disposal. The amount of mixed salt hazardous waste generated is reduced from 20-30% in the wet process to 3-5%. (4) The process flow is short, and the investment and operating costs are low. Compared with the wet process, the steps of leaching, solid-liquid separation, multi-effect evaporation, crystallization, and centrifugal dehydration are reduced. Equipment investment is reduced by 30-40%, the floor space is reduced by 40-50%, the number of operators is reduced by more than 50%, the system operation stability is improved, and the actual operating rate can reach more than 95%. (5) Reduced net energy consumption: Although high-temperature volatilization requires a higher temperature, 50-60% of the energy can be recovered through waste heat recovery, and the overall energy consumption is reduced by 20-35% compared with the wet process. (6) It has a high degree of automation and intelligence. Through the distributed control system, it can realize automatic monitoring, intelligent control and adaptive optimization of the whole process, and can realize unattended or minimally attended operation, reducing labor costs and operational risks. (7) Environmentally friendly, the exhaust gas is treated to a level that is superior to the national standard for various pollutant emission indicators, with no wastewater discharge and a solid waste resource utilization rate of ≥90%. It is a clean, efficient and economical fly ash treatment technology. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the waste incineration fly ash high-temperature dry graded treatment and resource recovery system of the present invention.

[0036] Figure 2This is a detailed structural schematic diagram of the multi-stage gradient condensation device of the present invention.

[0037] Figure 3 This is a schematic diagram of the high-temperature dust removal device of the present invention.

[0038] Figure 4 This is a schematic diagram of the high-temperature volatilization reactor of the present invention.

[0039] The components are as follows: 1-High-temperature volatilization reactor, 2-Fly ash inlet, 3-Regulator addition inlet, 4-Stirring device, 5-Heating device, 6-High-temperature flue gas outlet, 7-High-temperature dust removal device, 8-Metal bag filter dust collector, 9-Dust removal system, 10-Solid discharge outlet, 11-Purified gas outlet, 12-Multi-stage gradient condensation device, 13-Heavy metal condensation unit, 14-Potassium chloride condensation unit, 15-Sodium chloride condensation unit, 16-Heavy metal collection hopper, 17-Potassium chloride collection bin, 18-Sodium chloride collection bin, 19-Flue gas co-treatment device, 20-Quick cooling tower, 21-Alkali washing tower, 22-Bag filter dust collector, 23-Induced draft fan, 24-Main control system, 26-Heat exchange medium circulation system, 27-Mechanical dust removal device, 28-Cyclone separator, 29-Ceramic filter, 30-Nucleation promotion device, 31-Heat recovery device. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] Example 1: Medium-scale fly ash treatment system (50 tons / day) like Figure 1 As shown, a high-temperature dry graded treatment and resource recovery system for fly ash from waste incineration includes a high-temperature volatilization reactor 1, a high-temperature dust removal device 7, a multi-stage gradient condensation device 12, a flue gas co-treatment device 19, a heat recovery device 31, and a main control system 24.

[0045] like Figure 4 As shown, the high-temperature volatilization reactor 1 is a vertical cylindrical structure with an inner diameter of 3 meters and a height of 8 meters, employing a three-layer design. The innermost layer is refractory castable (300mm thick, made of corundum-mullite, refractoriness ≥1700℃), the middle layer is an aluminum silicate fiber insulation layer (200mm thick), and the outermost layer is a carbon steel shell (12mm thick, made of Q345R). The top of the reactor is equipped with a fly ash inlet 2 (DN200) and a regulator addition inlet 3 (DN150), both fitted with pneumatic airlock valves to prevent the leakage of high-temperature gases.

[0046] The reactor is equipped with a three-layer paddle-type stirring device 4. The stirring shaft is a hollow structure (outer diameter DN250, wall thickness 20mm, material 310S stainless steel), and cooling air is circulated inside for cooling. Each layer of stirring paddles has 4-6 blades, each blade is 1.2 meters long and 0.3 meters wide, and is made of heat-resistant cast steel. The stirring device is driven by a variable frequency motor (power 22kW), with an adjustable speed range of 5-30 rpm, and a normal operating speed of 15 rpm.

[0047] The reactor is equipped with two heating systems: the main heating system is a gas burner (1.5MW power, fueled by natural gas or liquefied petroleum gas), which injects tangentially through 12 burners to form a rotating flame; the auxiliary heating system is an electric heater (total power 500kW), consisting of 10 groups of silicon carbide heating elements, used for start-up preheating and temperature fine-tuning. A high-temperature flue gas outlet (DN800) is located at the bottom conical section of the reactor, connected to a high-temperature flue gas duct.

[0048] Fly ash treatment process: Waste incineration fly ash (moisture content <10%) is fed from the silo into a twin-screw mixer via a screw feeder, while calcium chloride regulator (92% purity, powder, particle size <1mm) is added simultaneously. The mixing ratio is fly ash:calcium chloride = 100:10. The mixer speed is 60 rpm, the mixing time is 5 minutes, and the mixing uniformity is 96%. The mixed material is continuously fed into the high-temperature volatilization reactor at a rate of 2100 kg / h via a screw feeder.

[0049] The reactor temperature is maintained at 900±20℃, monitored by 12 K-type thermocouples distributed across the upper, middle, and lower sections of the reactor, with 4 thermocouples per section. The burner and electric heater are automatically regulated by the temperature control system to maintain temperature stability. The material residence time in the reactor is approximately 45 minutes, and under high temperature and stirring, the fly ash is fully dispersed and comes into contact with the high-temperature atmosphere.

[0050] The following reaction occurs at 900℃: CaSO4 + CaCl2 → 2CaO + SO2↑ + Cl2↑ (2) PbO + 2HCl → PbCl2↑ + H2O (3) ZnO + 2HCl → ZnCl2↑ + H2O (4) 2NaCl → 2Na↑ + Cl2↑ (partial) (5) 2KCl → 2K↑ + Cl2↑ (partial) Dioxins are removed via pyrolysis at high temperatures (5% oxygen concentration), with a removal rate ≥99.9% as monitored by an online gas analyzer. The actual volatilization mechanism of potassium chloride and sodium chloride is as follows: in the presence of water vapor and HCl, they form low-melting-point hydrochloride eutectic compounds such as NaCl·HCl and KCl·HCl, lowering their effective boiling points to 800-900℃, thus achieving volatilization. The volatilization rates are: KCl 88%, NaCl 82%, ZnCl2 95%, PbCl2 91%, and CdCl2 93%.

[0051] like Figure 3 As shown, the high-temperature dust removal device 7 uses a metal bag filter dust collector 8, model GMDMC-128 (128 filter bags). The dust collector body is a square box with dimensions of 4m×4m×6m, divided into 4 chambers, each with 32 filter bags. The filter bag specifications are: diameter DN160, length 4000mm, material 316L sintered metal fiber, pore size 2 microns, single bag air permeability 120L / m²·min, single bag filtration area 2.01m², and total filtration area 257m².

[0052] High-temperature flue gas (approximately 850℃, flow rate approximately 8500 Nm³ / h, dust concentration approximately 300 g / Nm³) from a high-temperature volatile matter reactor enters the metal bag filter dust collector through an insulated pipe (lined with refractory castable). The flue gas flows from the outside to the inside of the filter bags, where fly ash particles are trapped on the outer surface to form a filter cake layer. Clean gas collects from the inside of the filter bags into the clean gas chamber and is discharged through the purified gas outlet 11 (DN600). The dust removal efficiency is 99.7%, and the dust content of the purified flue gas is <1 g / Nm³.

[0053] The dust collector is equipped with a pulse jet cleaning system, including: a compressed air system (working pressure 0.6MPa, air tank volume 3m³), an electric heater (heating the compressed air to 400℃), 32 pulse valves (model DMF-Z-76S), blowpipes, and venturi tubes. The cleaning control method is timed + differential pressure control. When the filter bag differential pressure reaches 1200Pa or after 60 minutes of operation, the cleaning program is automatically started. Cleaning is performed in compartments in turn, one compartment (8 filter bags) at a time. During cleaning, the inlet valve of that compartment is closed, and the pulse valves operate sequentially with a pulse width of 0.15 seconds and a pulse interval of 10 seconds. A total of 4 cleaning cycles are performed, with a total time of approximately 3 minutes.

[0054] The retained fly ash matrix is ​​discharged into the hopper through solid discharge port 10 (DN300) and discharged every 2 hours via a rotary discharger, with approximately 850 kg discharged each time. The chemical composition of the fly ash matrix is: CaO 45%, SiO2 22%, Al2O3 10%, Fe2O3 5%, NaCl 2.5%, KCl 1.8%, and other components 14.7%; heavy metal content: Pb 180 mg / kg, Zn 950 mg / kg, Cd 12 mg / kg; leaching toxicity test shows that the Pb leaching concentration is 0.8 mg / L (standard limit 5 mg / L), which meets the requirements of GB 5085.3 and can be used as a building material raw material.

[0055] like Figure 2 As shown, the multi-stage gradient condensation device 12 includes a heavy metal condensation unit 13, a potassium chloride condensation unit 14, and a sodium chloride condensation unit 15 connected in series.

[0056] The heavy metal condensation unit 13 includes a shell-and-tube high-temperature condenser, a heavy metal collection hopper 16, and a first cyclone separator 28A. The condenser has a vertical structure with a shell-side inner diameter of DN1000 and a height of 4 meters. The tube side has 37 heat exchange tubes (outer diameter DN76, wall thickness 5mm, length 3.5 meters, material Inconel 625). The inner wall of the tubes is welded with spiral baffles (pitch 200mm) to form a corrugated structure, with an effective heat exchange area of ​​35m².

[0057] High-temperature flue gas (approximately 800℃, flow rate approximately 8500 Nm³ / h, containing gaseous KCl, NaCl, and heavy metal chlorides) enters the tube side of the condenser from the bottom and flows upwards. The shell side uses molten salt heat exchange medium (composition: 53% KNO₃ + 40% NaNO₂ + 7% NaNO₃, operating temperature range 200-600℃), driven by a molten salt pump, entering from the top and flowing downwards, forming counter-current heat exchange. The molten salt flow rate is 12 m³ / h, the inlet temperature is 480℃, and the outlet temperature is 520℃. The flue gas residence time in the condenser is approximately 8 seconds, and the outlet temperature drops to 500±15℃.

[0058] At this temperature, the vapors of high-boiling-point heavy metal chlorides (ZnCl2 boiling point 732℃, PbCl2 boiling point 950℃, CdCl2 boiling point 960℃) reach a supersaturated state, condensing into droplets or solid particles on the tube wall and the surface of the baffles. The droplets flow down the tube wall, while the solid particles are carried out by the airflow. A heavy metal collection hopper 16 (0.5 m³ volume) is connected to the bottom of the condenser to collect the liquid and flowing-down solid heavy metals. The heavy metal concentrate is discharged every 4 hours through a high-temperature rotary valve (DN150, temperature resistance 600℃), approximately 18 kg each time.

[0059] The flue gas exiting the condenser enters the first cyclone separator 28A (model XLP9-02, diameter DN800, height 3 meters), which separates heavy metal particles entrained in the gas flow, achieving a separation efficiency of 92%. The collected solids are also discharged into the heavy metal collection hopper. The chemical composition of the collected heavy metal concentrate is: Zn 28%, Pb 12%, Cd 0.8%, Cu 3%, Ca 8%, Cl 35%, and other components 13.2%, with a total heavy metal content of 43.8%.

[0060] The potassium chloride condensation unit 14 employs three parallel modules. Each module includes a shell-and-tube medium-temperature condenser, a nucleation promoting device 30, a second cyclone separator 28B, and a ceramic filter 29. During normal operation, all three modules work simultaneously. When one module requires cleaning or maintenance, it can be switched offline, while the other two modules continue to operate.

[0061] The single-module medium-temperature condenser has a vertical structure with a shell-side inner diameter of DN800 and a height of 3.5 meters. The tube side consists of 61 heat exchange tubes (outer diameter DN51, wall thickness 4mm, length 3 meters, made of 316L stainless steel) with smooth inner walls, providing an effective heat exchange area of ​​28 m². Flue gas enters the tube side from the bottom, while the shell side uses high-temperature heat transfer oil (synthetic type, model Dowtherm A, operating temperature range -50℃ to 400℃), which enters from the top.

[0062] The heat transfer oil flow rate is 8 m³ / h, with an inlet temperature of 280℃ and an outlet temperature of 310℃. The flow rate is controlled by a precision proportional control valve (Siemens VVF53, adjustment accuracy ±0.5%), achieving precise temperature control. The tube-side flue gas temperature decreases from 500℃ at the inlet to 310±8℃ at the outlet. The condenser outlet flue gas temperature is measured by two platinum resistance thermometers (Pt100, accuracy ±0.3℃). The temperature signal is fed back to the PID controller, which adjusts the heat transfer oil flow rate in real time.

[0063] A nucleation promoting device 30 is installed before the condenser inlet, employing an airflow jet mixer. The inert carrier particles are high-purity alumina microspheres (99.5% purity, 10-30 micrometers in diameter, bulk density 0.8 g / cm³), stored in a silo and fed into the jet mixer at a rate of 0.8 kg / h via a screw feeder. The jet mixer uses compressed air (0.4 MPa pressure, 50 Nm³ / h flow rate) to disperse the alumina microspheres and spray them into the flue gas, achieving a mixing uniformity >90%.

[0064] Alumina microspheres act as condensation nuclei, allowing gaseous potassium chloride molecules to condense and grow on their surfaces, forming core-shell composite particles with an average particle size of 120 micrometers. This controllable nucleation technology avoids the problem of spontaneous nucleation of gaseous KCl forming a large number of fine particles (particle size <5 micrometers) that are difficult to collect, increasing the collection efficiency from 85% to 98%.

[0065] The solid potassium chloride particles formed by condensation are carried by the airflow into the second cyclone separator 28B (model XLT / A-6, diameter DN600, height 2.5 m), with a separation efficiency of 96%. The collected solids (containing approximately 5% alumina microspheres) are discharged into the potassium chloride collection chamber 17 (volume 5 m³). Fine particles not captured by the cyclone separator enter the ceramic filter 29 (filtration area 15 m², material silicon nitride ceramic, pore size 1 micrometer) for further removal, ensuring a total collection efficiency ≥98.5%.

[0066] The three modules collectively collect approximately 232 kg / h of potassium chloride product (5.57 tons per day). The chemical composition of the product is: KCl 91%, NaCl 6.5%, CaCl2 0.8%, Al2O3 (carrier residue) 0.5%, heavy metals <0.3%, and moisture <1%. The product quality meets the GB / T 6549-2011 standard for first-class industrial potassium chloride (KCl≥90%). For further purification, the purity can be increased to over 98% through a water washing-recrystallization process.

[0067] The sodium chloride condensation unit 15 also uses three parallel modules. Each module includes a shell-and-tube low-temperature condenser, a mechanical cleaning device 27, a third cyclone separator 28C, and a ceramic filter 29.

[0068] The structure of a single-module cryogenic condenser is similar to that of a potassium chloride condenser, but the heat exchange tubes are made of 2205 duplex stainless steel (resistant to chloride ion stress corrosion), and a spiral scraper cleaning device is installed inside the tubes. Each heat exchange tube contains a rotating shaft (diameter DN20, material 316L), with spiral scraper blades welded onto the shaft (150mm pitch, 1mm gap between the blade and the tube wall). The 37 rotating shafts are driven by a single motor (5.5kW power, 10rpm speed) via a bevel gear mechanism.

[0069] The flue gas temperature drops from 310℃ at the inlet to 200±10℃ at the outlet. The condenser shell side uses high-temperature heat transfer oil with an inlet temperature of 180℃ and an outlet temperature of 210℃. At this temperature, a large amount of sodium chloride condenses and precipitates, but it easily deposits on the tube wall. A rotating scraper operates continuously to promptly remove the salt layer deposited on the tube wall, and the scraped salt powder is carried away by the airflow.

[0070] The condenser casing is also equipped with three electromagnetic vibrators (model ZDJ-2.5, excitation force 2.5kN, frequency 100Hz), which automatically vibrate once every 3 hours for 10 minutes each time to further prevent salt buildup and caking. During vibration, a significant increase in the amount of salt powder discharged from the bottom of the condenser can be observed.

[0071] The condensed sodium chloride particles are collected by the third cyclone separator 28C (same model as 28B) and ceramic filter 29, with a total collection efficiency of ≥97%. The three modules collect a total of approximately 305 kg / h of sodium chloride product (7.32 tons per day). The chemical composition of the product is: NaCl 85%, KCl 10%, CaCl2 2%, CaSO4 1.5%, heavy metals <1%, and moisture <2%. The product can be used as industrial salt or a de-icing agent, with a selling price of approximately 400-600 yuan / ton.

[0072] The exhaust gas temperature after three-stage condensation is about 150℃, and the flow rate is about 8000 Nm³ / h. The main components are N2, O2, CO2, and H2O, and it contains trace amounts of uncondensed KCl and NaCl (total <8mg / Nm³), heavy metal vapors (Pb+Zn+Cd<6mg / Nm³), and acidic gases (HCl about 380mg / Nm³, SO2 about 220mg / Nm³).

[0073] like Figure 1 As shown, the exhaust gas enters the flue gas co-treatment device 19. First, it passes through a quench tower 20, where atomized circulating water (water temperature 20℃, water flow rate 1200L / h, atomization pressure 0.6MPa) is sprayed into the tower, rapidly cooling the exhaust gas temperature from 150℃ to 65℃ within 1.2 seconds. During the quenching process, residual heavy metal vapors quickly condense into fine particles (particle size 0.1-1 micrometer), while HCl partially dissolves in the water droplets.

[0074] Then it enters alkaline scrubbing tower 21 (model: spray scrubbing tower, diameter DN1200, height 6 meters, packing layer height 3 meters, packing material: Φ50mm polypropylene Pall rings). A 10% NaOH solution is sprayed from the top of the tower (circulation rate 8 m³ / h, replenishment rate 0.2 m³ / h), contacting the flue gas counter-currently to absorb HCl and SO2. HCl + NaOH → NaCl + H2O SO2 + 2NaOH → Na2SO3 + H2O Na₂SO₃ + 1 / 2O₂ → Na₂SO₄ The scrubbing tower had a liquid-to-gas ratio of 1:1000, a residence time of 5 seconds, and achieved an HCl removal efficiency of 98% and an SO2 removal efficiency of 96%. After scrubbing, the HCl concentration in the flue gas was reduced to <8 mg / Nm³, and the SO2 concentration was reduced to <10 mg / Nm³.

[0075] Finally, the dust is collected by a bag filter 22 (model PPCS128-6, 128 filter bags, PTFE membrane needle-punched felt material, filtration velocity 0.8m / min) to remove fine particulate matter, with a dust removal efficiency of 99.95%. The purified flue gas is then sent to a 20-meter-high chimney by an induced draft fan 23 (model Y9-35-11No16D, air volume 12000m³ / h, air pressure 5000Pa, power 45kW).

[0076] Exhaust emission monitoring results (average over 7 consecutive days): particulate matter 12 mg / Nm³, HCl 6 mg / Nm³, SO2 8 mg / Nm³, heavy metals (Pb+Cd+Cr+Cu+Mn+Ni+As) 0.42 mg / Nm³, NOx 65 mg / Nm³, all of which are better than the GB 18485-2014 standard.

[0077] The main control system 24 adopts ABB's AC800M DCS system, configured with 3 operator stations, 2 engineering stations, and 1 database server. The system has approximately 800 I / O points, including: 120 temperature measurement points, 45 pressure measurement points, 28 flow measurement points, 16 level measurement points, 180 digital inputs, 150 digital outputs, and 85 analog outputs. Key locations are also equipped with an online gas analyzer (infrared method, monitoring HCl, SO2, and CO), a laser particle size analyzer (monitoring condensate particle size), and an online heavy metal monitoring system (ICP-MS method).

[0078] The main functions implemented by the control system include: (1) Real-time monitoring of process parameters: All data at measuring points are refreshed every 1 second and displayed as a trend curve. Historical data is saved for 3 years. (2) Automatic start-stop control: Four operating modes are designed: cold start, hot start, normal stop, and emergency stop. Each mode contains automatic sequential control of dozens of operating steps. (3) Automatic adjustment and control: 18 key parameters, such as the temperature of the high-temperature volatilization reactor, the temperature of each stage of the condensation unit, and the pH value of the washing tower, are automatically adjusted by PID, and the adjustment accuracy and response speed are better than manual operation. (4) Alarm and interlock protection: 135 alarm points are set up, divided into three levels of alarm (early warning, first-level alarm, and second-level alarm) and emergency shutdown. For example, an early warning is issued when the reactor temperature exceeds 950℃, a first-level alarm is issued when it exceeds 980℃ and the heating power is automatically reduced, a second-level alarm is issued when it exceeds 1000℃ and the feeding is automatically stopped, and an emergency shutdown is initiated when it exceeds 1050℃ and the emergency cooling program is activated; (5) Data statistics and analysis: The system automatically records indicators such as fly ash processing volume, product output, energy consumption, and recovery rate for each shift, day, and month, and generates statistical reports; (6) Fault Diagnosis: Based on the expert system, when equipment malfunctions, the system will analyze possible causes and provide handling suggestions. For example, when the product purity of the potassium chloride condensation unit suddenly drops, the system will indicate possible causes including: high condensation temperature, insufficient nucleating agent addition, cyclone separator blockage, etc., and suggest checking each item one by one; (7) Remote monitoring: Through industrial firewall and VPN technology, authorized users are allowed to access the system via the Internet to view operating data and alarm information, and realize remote diagnosis and technical support.

[0079] The system is operated by four personnel (two in two shifts), whose main tasks include monitoring system operation, conducting regular equipment inspections, replacing filter bags, and cleaning the collection chamber. In automatic operation mode, the system can run continuously and stably without the need for daily manual intervention.

[0080] The heat recovery unit 31 includes three waste heat boilers: (1) Waste heat boiler for heavy metal condensation unit: recovers heat (temperature 520℃) from molten salt heat exchange medium and generates 1.2 tons / hour of 1.0MPa saturated steam; (2) Potassium chloride condensing unit waste heat boiler: recovers heat from the heat transfer oil (temperature 310℃) and generates 0.8 tons / hour of saturated steam at 0.6MPa; (3) Sodium chloride condensing unit waste heat boiler: recovers heat from the heat transfer oil (temperature 210℃) and generates 0.5 tons / hour of saturated steam at 0.3MPa.

[0081] A total of 2.5 tons of steam is generated per hour, which is used for: Preheating of feed fly ash and conditioning agent: 0.3 tons / hour Heating alkaline scrubbing tower washing liquid: 0.2 tons / hour For heating and domestic use in the factory area: 1.2 tons / hour Power generation from the steam turbine generator: 0.8 tons / hour (approximately 120kW) Through waste heat recovery, the system's total energy consumption is reduced by 28%, from the theoretical value of 3200 kWh / ton of fly ash to the actual value of 2300 kWh / ton of fly ash (of which 1850 kWh / ton is purchased electricity and 450 kWh / ton is natural gas equivalent).

[0082] Example 2: Large-scale fly ash treatment system (200 tons / day) Based on Example 1, a scale-up design was carried out, with the main parameters adjusted as follows: High-temperature volatilization reactor: inner diameter 4.5 meters, height 12 meters, processing capacity 8400 kg / h, stirring device power 75 kW, heating device is gas burner (6 MW) + electric heater (1.5 MW); High-temperature dust removal device: Two GMDMC-256 dust collectors are connected in parallel, each with 256 filter bags, a total filtration area of ​​1028m², and a processing air volume of 34000Nm³ / h. Multi-stage gradient condensation unit: Each condensation unit uses 6 modules connected in parallel, with 5 operating normally and 1 on standby for maintenance, ensuring high system availability; Product output: Approximately 22 tons of potassium chloride (90% purity), approximately 29 tons of sodium chloride (84% purity), approximately 1.4 tons of heavy metal concentrate (40% heavy metal content), and approximately 130 tons of fly ash matrix per day (which can be recycled). Economic benefits: The total investment is approximately RMB 85 million, the annual operating cost is approximately RMB 28 million (including energy, labor, maintenance, and depreciation), the annual fly ash processing capacity is 66,000 tons, the annual revenue is approximately RMB 42 million (fly ash processing fee of RMB 33 million, calculated at RMB 500 / ton; by-product sales of RMB 9 million), the annual profit is approximately RMB 14 million, and the investment payback period is approximately 6 years.

[0083] Example 3: Integrated design with waste incinerator The system of this invention can be integrated with newly built waste incineration power plants, making full use of the high-temperature flue gas from the incinerator as a heat source to further reduce energy consumption.

[0084] System Layout: The high-temperature volatilization reactor is directly connected after the secondary combustion chamber of the incinerator and before the waste heat boiler. It utilizes the flue gas (temperature 950-1050℃) from the outlet of the secondary combustion chamber as the heat source for high-temperature volatilization, eliminating the need for additional burner heating. The mixture of fly ash and regulator is injected into the high-temperature flue gas flow from the side wall of the reactor and moves upward under the influence of the flue gas to complete the volatilization reaction.

[0085] Advantages: (1) Saves fuel, and the energy consumption in the high-temperature volatilization process is reduced to zero; (2) Simplified equipment, no separate reactor and heating device required; (3) Improve the efficiency of waste heat boilers. Since chlorides in fly ash are removed in advance, corrosion and ash accumulation on boiler heating surfaces are reduced, and boiler availability is increased by 5-10%. (4) Reduce the amount of fly ash generated in the incinerator. Since some materials have been separated during the volatilization process, the amount of fly ash entering the waste heat boiler and flue gas purification system is reduced by 30-40%, which reduces the load on the bag filter.

[0086] After adopting this integrated design scheme, a waste-to-energy plant with a capacity of 800 tons / day reduced its fly ash treatment cost from the original external transportation and landfill (1200 yuan / ton) to self-treatment (comprehensive cost of about 400 yuan / ton, after deducting by-product revenue after considering depreciation and operating costs), saving about 18 million yuan annually.

[0087] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A high-temperature dry graded treatment and resource recovery system for waste incineration fly ash, characterized in that, It includes a high-temperature volatilization reactor (1), a high-temperature dust removal device (7), a multi-stage gradient condensation device (12), and a main control system (24); The high-temperature volatilization reactor (1) includes a fly ash inlet (2), a regulator addition inlet (3), a heating device (5), and a high-temperature flue gas outlet (6), which is used to remove dioxins by pyrolysis or oxidative decomposition at 800-1200℃, while soluble salts and heavy metal chlorides in the fly ash volatilize into gaseous state. The air inlet of the high-temperature dust removal device (7) is connected to the high-temperature flue gas outlet (6) of the high-temperature volatile reactor (1). The high-temperature dust removal device (7) includes a metal filter bag dust collector or a ceramic filter tube dust collector, which is used to intercept fly ash matrix that has been desalted and heavy metals removed under conditions of 500-800℃. The high-temperature dust removal device (7) is provided with a solid discharge outlet (10) and a purified gas outlet (11). The inlet of the multi-stage gradient condensation device (12) is connected to the purified gas outlet (11) of the high-temperature dust removal device (7). The multi-stage gradient condensation device (12) includes a heavy metal condensation unit (13), a potassium chloride condensation unit (14), and a sodium chloride condensation unit (15) connected in series. The heavy metal condensation unit (13), the potassium chloride condensation unit (14), and the sodium chloride condensation unit (15) are each equipped with an independent temperature control system and a solid collection device. The main control system (24) is electrically connected to the high-temperature volatilization reactor (1), the high-temperature dust removal device (7), and the multi-stage gradient condensation device (12) respectively, and is used to monitor and control the operating parameters of each device.

2. The waste incineration fly ash high-temperature dry graded treatment and resource recovery system according to claim 1, characterized in that, The high-temperature volatilization reactor (1) is a vertical or horizontal rotary kiln structure with an inner diameter of 1.5-4 meters and a length of 6-15 meters. It is equipped with a multi-layer paddle or rake stirring device (4) with a rotation speed of 5-30 rpm. The high-temperature dust removal device (7) adopts a metal filter bag dust collector (8). The metal filter bag in the metal filter bag dust collector (8) has a pore size of 0.5-5 micrometers and an air permeability of 50-200 L / m²·min. The metal filter bag dust collector (8) is equipped with a high-temperature pulse back-flushing cleaning system (9). The cleaning air source temperature is 300-500℃, the pressure is 0.4-0.8MPa, and the pulse width is 0.05-0.3 seconds.

3. The waste incineration fly ash high-temperature dry graded treatment and resource recovery system according to claim 1, characterized in that, The working temperature of the heavy metal condensation unit (13) is 400-650℃, the working temperature of the potassium chloride condensation unit (14) is 250-400℃, and the working temperature of the sodium chloride condensation unit (15) is 150-250℃. The heavy metal condensation unit (13) includes a high-temperature condenser, a heavy metal collection hopper (16), a first cyclone separator (28), and a first ceramic filter (29); The potassium chloride condensation unit (14) includes a medium-temperature condenser, a nucleation promotion device (30), a second cyclone separator (28), a second ceramic filter (29), and a potassium chloride collection chamber (17); The nucleation promoting device (30) uses an air jet mixer to uniformly disperse inert carrier particles into the airflow. The particle size is 5-50 micrometers, and the amount added is 0.1-1% of the theoretical precipitation amount of potassium chloride. The sodium chloride condensation unit (15) includes a low-temperature condenser, a mechanical cleaning device (27), a third cyclone separator (28), a third ceramic filter (29), and a sodium chloride collection chamber (18).

4. The waste incineration fly ash high-temperature dry graded treatment and resource recovery system according to claim 1, characterized in that, The heavy metal condensing unit (13), potassium chloride condensing unit (14) and sodium chloride condensing unit (15) all use molten salt or high-temperature heat transfer oil as heat exchange medium (26); The molten salt is a sodium nitrate-potassium nitrate mixture or a carbonate mixture, with an operating temperature range of 200-600℃; the high-temperature heat transfer oil is a biphenyl-diphenyl ether mixture or a synthetic heat transfer oil, with an operating temperature range of 100-400℃. Both the potassium chloride condensing unit (14) and the sodium chloride condensing unit (15) adopt a modular parallel design. Each unit includes 2-4 parallel condensing modules. Each module can operate and switch independently to ensure that the system has a continuous and stable operating rate of ≥95%.

5. The high-temperature dry graded treatment and resource recovery system for waste incineration fly ash according to claim 1, characterized in that, It also includes a flue gas co-treatment device (19), which includes a quench tower (20), an alkaline scrubbing tower (21), a bag filter (22), and an induced draft fan (23). The inlet of the quench tower (20) is connected to the tail gas outlet of the sodium chloride condensation unit (15) to rapidly cool the tail gas temperature from 150-200℃ to below 70℃. The alkaline scrubbing tower (21) absorbs HCl and SO2 acidic gases with sodium hydroxide or calcium hydroxide solution.

6. The high-temperature dry graded treatment and resource recovery system for waste incineration fly ash according to claim 1, characterized in that, It also includes a heat recovery device (31) for recovering sensible and latent heat released during multi-stage condensation; the heat recovery device (31) includes a waste heat boiler or a thermal oil heater, which uses the recovered heat to preheat fly ash, heating regulators, generate steam, or supply heating for the plant area, with a heat recovery efficiency of ≥60%; The main control system (24) adopts a distributed control system DCS or a programmable logic controller PLC and is equipped with an industrial touch screen human-machine interface.

7. A method for resource recovery from waste incineration fly ash treated by a high-temperature dry graded treatment system as described in any one of claims 1-6, characterized in that, The resource recovery method includes the following steps: Step S1: Fly ash pretreatment, mix the waste incineration fly ash and regulator at a mass ratio of 100:(3-20) evenly, and send the mixed material into the high temperature volatilization reactor (1) through a screw feeder or pneumatic conveying system. Step S2: High-temperature volatilization. The mixture is heated to 800-1200℃ in a high-temperature volatilization reactor (1) and held for 20-90 minutes to allow dioxins to be decomposed and removed at 850℃ or above. At the same time, the regulator promotes the full volatilization of potassium chloride, sodium chloride and heavy metal chlorides in fly ash into gaseous state. Step S3: High-temperature dust removal. The high-temperature flue gas after volatilization is filtered through metal filter bags or ceramic filter tubes at 500-800℃ to remove the fly ash matrix that has been desalted and heavy metals, with a filtration efficiency of ≥99.5%. Step S4: Heavy metal separation. The purified gas enters the heavy metal condensation unit (13) and is cooled to 400-650℃, so that the high-boiling-point heavy metal chlorides are preferentially condensed and precipitated. Step S5: Potassium chloride recovery. The gas continues to be cooled and enters the potassium chloride condensation unit (14). The temperature is controlled at 250-400℃. The potassium chloride is promoted to form uniform particles through the nucleation promotion device (30) and collected. The purity of the collected potassium chloride product is ≥80%. Step S6: Sodium chloride recovery. The gas temperature is further reduced to 150-250℃ and enters the sodium chloride condensation unit (15). The sodium chloride is condensed into a solid and removed and collected by a mechanical dust removal device. The purity of the collected sodium chloride product is ≥75%. Step S7: Tail gas treatment. After three-stage condensation, the tail gas is treated by a quench tower (20), an alkaline scrubbing tower (21), and a bag filter (22) in sequence before being discharged in compliance with standards.

8. The method for resource recovery of high-temperature dry graded treatment of waste incineration fly ash according to claim 7, characterized in that, In step S1, the regulator is calcium chloride with a purity ≥90%, and the amount added is 8-12% of the fly ash mass. In step S2, the temperature of high-temperature volatilization is 850-1000℃, the residence time is 30-60 minutes, and the high-temperature volatilization reactor (1) is maintained in a slightly negative pressure state with a pressure of -50 to -500 Pa.

9. The method for resource recovery of high-temperature dry graded treatment of waste incineration fly ash according to claim 7, characterized in that, In step S4, the temperature of the heavy metal condensation unit (13) is 450-550℃, the cooling rate is 50-200℃ / min, and the heavy metal content in the heavy metal condensate is ≥25%. In step S5, the temperature of the potassium chloride condensation unit (14) is 280-350℃, the injection rate of the inert carrier particles is 0.1-1% of the theoretical potassium chloride precipitation, promoting the formation of uniform potassium chloride particles with a particle size of 50-300 micrometers, and the potassium chloride recovery rate is 70-90% of the potassium chloride content in the original fly ash; In step S6, the temperature of the sodium chloride condensation unit (15) is 180-220℃, the spiral scraper rotates continuously at a speed of 5-15 rpm, the electromagnetic vibrator or sonic soot blower runs automatically once every 1-5 hours, and the sodium chloride recovery rate is 65-85% of the sodium chloride content in the original fly ash.

10. The method for resource recovery of high-temperature dry graded treatment of waste incineration fly ash according to claim 7, characterized in that, In step S7, the exhaust gas first passes through a quench tower (20) to rapidly reduce the temperature to 60-80℃ within 0.5-2 seconds, then enters an alkaline scrubbing tower (21) to absorb HCl and SO2 with a 5-15% sodium hydroxide solution or lime milk, with an absorption efficiency ≥95%, and finally passes through a bag filter (22) to remove fine particles, with a dust removal efficiency ≥99.9%.

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