CN-121972497-A - Multistage pickling and recycling method for solid waste incineration fly ash

CN121972497ACN 121972497 ACN121972497 ACN 121972497ACN-121972497-A

Abstract

The invention belongs to the technical field of solid waste treatment, and particularly relates to a multistage pickling and recycling method for solid waste incineration fly ash. The method comprises the steps of secondary water washing and desalting, ammonium chloride washing, acid washing and sintering. The invention can realize the resource recycling of the solid waste incineration fly ash, effectively improve the treatment efficiency of the solid waste incineration fly ash, reduce the treatment cost and reduce secondary pollution. The method has the following significance that a, resource utilization is realized by converting the solid waste incineration fly ash into valuable resources, recycling of the resources is realized, and sustainable development is promoted. b. The environmental protection is that the solid waste incineration fly ash is effectively treated, the secondary pollution to the environment is reduced, and the ecological environment is protected.

Inventors

CHEN KEFA
LIU DEXUE
LI WENFENG
HUANG GUOHONG
HUANG YUNLAN
HUANG GUOQING
LI DEKUN
LI YURONG
ZHOU SHILI
HUANG LINXIANG
LING JIAFU

Assignees

中节能（广西）清洁技术发展有限公司

Dates

Publication Date: 20260505
Application Date: 20260127

Claims (10)

1. A method for multi-stage pickling and recycling of solid waste incineration fly ash, which is characterized by comprising the following steps: (1) And (3) secondary water washing and desalting: The solid waste incineration fly ash enters a pulping kettle, liquid-solid ratio parameters are prepared in the primary pulping kettle, retention time parameters are set, primary washing water is added, filter pressing is carried out after primary washing of the fly ash, a filter cake enters a secondary washing pulping kettle, secondary washing is carried out continuously, liquid-solid ratio parameters are prepared in the secondary pulping kettle, retention time parameters are set, filtration is carried out after secondary washing of the fly ash, a filter cake enters the next working procedure, and secondary washing filtrate directly returns to the primary washing working procedure; Adding a heavy metal capturing agent into the primary water washing filtrate to carry out sulfuration reaction, removing heavy metal in the solution, transferring the solution into a sodium sulfate reaction kettle, adding sodium sulfate into the sodium sulfate reaction kettle to carry out stirring reaction, filtering to obtain byproduct calcium sulfate dihydrate and a first filtrate, adding sodium carbonate into the sodium carbonate reaction kettle to carry out stirring reaction continuously, filtering to obtain byproduct calcium carbonate and a second filtrate, cooling, crystallizing/filter pressing the second filtrate to obtain sodium sulfate decahydrate and a third filtrate, returning the sodium sulfate decahydrate to the sodium sulfate reaction kettle, and carrying out fractional evaporation, salt separation and crystallization on the third filtrate to obtain sodium chloride and potassium chloride byproducts; (2) Washing with ammonium chloride: The filter cake after the second-stage water washing enters an ammonium chloride pulping kettle for pulping, an ammonium chloride solution is added, the mixture is stirred uniformly and then transferred into a reaction kettle for reaction, after the reaction is completed, filter pressing is carried out, a filter cake and a fourth filtrate are obtained, and the filter cake enters an acid water washing process; Adding a heavy metal capturing agent into the fourth filtrate, stirring, stopping stirring after the filtrate is solid, adding a flocculating agent, stirring rapidly, stirring slowly, waiting for the particle size to become large, performing filter pressing, introducing the generated fifth filtrate into an evaporation kettle for ammonia distillation, condensing the evaporated gas, introducing into an ammonia water carbonization kettle, adding carbon dioxide for carbonization to form ammonium carbonate, mixing an ammonium carbonate solution with a deaminated calcium chloride solution for reaction to obtain calcium carbonate precipitate, filtering to obtain a calcium carbonate filter cake and a sixth filtrate, and drying the filter cake to obtain byproduct light calcium carbonate; The sixth filtrate after calcium carbonate filtration enters a diverter to be diverted, 20% -30% of solution directly enters an ammonium chloride solution tank, and the rest solution is subjected to salt separation; (3) Acid washing: feeding the filter cake washed by ammonium chloride into an acid washing pulping kettle, pulping, adding hydrochloric acid, adjusting the pH of the slurry to be less than 7, continuously adding hydrochloric acid, and leaching calcium, zinc and copper in fly ash into solution; After the reacted slurry is subjected to pressure filtration, transferring the seventh filtrate into an acid washing reaction kettle, adding a heavy metal capturing agent for removing impurities, and obtaining a product liquid calcium chloride; (4) Sintering: and (5) feeding the filter cake after pickling into a roasting kiln for sintering.
2. The method for multi-stage pickling and recycling of solid waste incineration fly ash according to claim 1, wherein the elements contained in the solid waste incineration fly ash comprise Na, ca, K, cl, si.
3. The method for recycling the solid waste incineration fly ash by multi-stage pickling according to claim 1, wherein the form of the calcium element in the solid waste incineration fly ash comprises CaCl 2 、CaCO 3 、CaSO 4 and CaO and/or Ca (OH) 2 .
4. The method for multi-stage pickling and recycling of solid waste incineration fly ash according to claim 1, wherein at least one of the following characteristics is satisfied: in the step (1), in a primary pulping kettle, the liquid-solid ratio parameter is 1.5-2.5:1, and the residence time parameter is 4-5 h; in the step (1), in a secondary pulping kettle, the liquid-solid ratio parameter is 1.5-2.5:1, and the residence time parameter is 3-4 h.
5. The method for multi-stage pickling and recycling of solid waste incineration fly ash according to claim 1, wherein at least one of the following characteristics is satisfied: in the step (1), the heavy metal capturing agent is sodium sulfide; In the step (1), the fractional evaporation and salt separation crystallization adopts a mechanical vapor recompression evaporation crystallizer.
6. The method for multi-stage pickling and recycling of solid waste incineration fly ash according to claim 1, wherein at least one of the following characteristics is satisfied: In the step (2), the flocculant is PAM; in the step (2), the heavy metal capturing agent is ferrous sulfate; in the step (2), the temperature of the reaction is 55-65 ℃, and steam is optionally introduced for indirect heating; In the step (2), the rotating speed of the rapid stirring is 300-500rpm, and the rotating speed of the slow stirring is 50-80rpm.
7. The method for recycling the solid waste incineration fly ash by multi-stage pickling according to claim 1, wherein in the step (2), the residual solution enters a triple-effect evaporator for salt separation, the mixed salt with the main component of NaCl and the concentrated ammonium chloride solution are obtained after the treatment of the triple-effect evaporator, the mixed salt is recycled in a water washing liquid evaporation crystallization process, and the ammonium chloride solution is recycled in an ammonium chloride washing process.
8. The method for recycling solid waste incineration fly ash by multi-stage pickling according to claim 1, wherein in the step (3), the heavy metal capturing agent is thiourea.
9. The method for recycling the solid waste incineration fly ash by multi-stage pickling according to claim 1, wherein in the step (3), after adding the heavy metal capturing agent, the method further comprises the steps of filter pressing, removing heavy slag by using pickling solution, adding calcium hydroxide into the obtained filtrate, and after reacting, performing filter pressing to obtain a magnesium hydroxide filter cake and liquid calcium chloride.
10. The method for recycling the solid waste incineration fly ash by multi-stage pickling according to claim 1, wherein in the step (4), the sintering time is 4-6h, and the sintering temperature is 900-1100 ℃.

Description

Multistage pickling and recycling method for solid waste incineration fly ash Technical Field The invention belongs to the technical field of solid waste treatment, and particularly relates to a multistage pickling and recycling method for solid waste incineration fly ash. Background The incineration harmless treatment technology is most widely applied in the field of solid waste treatment due to the advantages of capacity reduction and quantity reduction and heat energy recovery. The harmless treatment technology for incineration is an efficient treatment method for realizing reduction and harmlessness of solid waste by reasonably matching the solid waste to reach proper heat value and combustion condition and performing oxidative decomposition in a high-temperature incinerator. The solid waste incineration temperature is above 1100 ℃, so that the composition structure of most toxic and harmful organic matters can be effectively destroyed, the volume of most waste is reduced, and a large amount of fly ash is generated in the solid waste incineration process. However, with the wide application of the incineration disposal technology, the incineration fly ash of the solid waste incineration secondary waste is produced in a large amount, the incineration fly ash has a large daily average yield, contains a large amount of pollution components such as salts, heavy metal elements, dioxin and the like, and has the characteristics of complex components and the like. At present, the main treatment mode of the solid waste incineration fly ash is that the medicament stabilized cement is solidified and then enters a landfill site for safe landfill, so that the stabilized solidification landfill mode occupies more land resources, the treatment efficiency is low, the treatment cost is higher, the risk that the pollution components are possibly released again exists, and the environment-friendly potential safety hazard exists. Therefore, the development of a new solid waste incineration fly ash treatment technology has important significance for effective treatment and resource utilization. The harm of the solid waste incineration secondary fly ash mainly comes from the first water-soluble salt. The fly ash contains a large amount of water-soluble sodium salt, potassium salt and calcium salt, and the fly ash is nontoxic, but the existence of the water-soluble salt can cause great harm to harmless treatment of the fly ash. After harmless landfill treatment, the water-soluble salt in the solidified body can be slowly leached out, so that the solidified body collapses, and heavy metals can be leached out, and meanwhile, the soluble salt enters the percolate, so that the treatment difficulty of the percolate is increased, and the generation of impurity salt is avoided. In the high temperature solidification process, although the fly ash can be used as a building material after vitrification, the water-soluble salt is used as a chloridizing volatile, and in the high temperature vitrification process, the solidification of heavy metals is seriously affected, equipment is severely corroded and refractory materials are corroded. Therefore, the water-soluble salts in fly ash are generally separated before harmless and recycling. Second, heavy metals and small amounts of dioxins. The fly ash contains a large amount of heavy metals and compounds thereof, mainly Cr 6+、Pb2+、Zn2+ and the like, and if the heavy metals are improperly treated, the heavy metals not only seriously pollute soil, water sources and the like, but also possibly enter human bodies through food chains, and the heavy metals are toxic to human health. Dioxins contained in fly ash, mainly polychlorinated dibenzodioxin (PCDD S) and polychlorinated dibenzofuran (PCDF S), are extremely toxic substances that are difficult to degrade and eliminate naturally once they penetrate into the environment. The traditional fly ash treatment technology mainly comprises a stabilization solidification landfill method, a pyrolysis method and the like. The treatment by the method of stabilizing, solidifying and burying occupies more land resources, has low treatment efficiency, simultaneously has the risk that the polluted components can be released again, and has environmental protection and safety hidden trouble. In addition, the fly ash is rich in inorganic salt and heavy metal, so that the landfill treatment can cause waste of a large amount of resources. The pyrolysis method is used for treatment, and because the heat value of the fly ash is low, the combustion efficiency is low, more energy sources are required to be consumed to realize harmless treatment, and the fly ash has small particle size and is not easy to settle, so that difficulties are brought to transportation and treatment, the disposal cost is increased, and the disposal cost is high. The main elements in the solid waste incineration fly ash are Na, ca, K, cl, si and the like, and the solid waste incineration fly a