CN112775145A - Efficient secondary washing process for household garbage incineration fly ash - Google Patents

Efficient secondary washing process for household garbage incineration fly ash Download PDF

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CN112775145A
CN112775145A CN202011526592.2A CN202011526592A CN112775145A CN 112775145 A CN112775145 A CN 112775145A CN 202011526592 A CN202011526592 A CN 202011526592A CN 112775145 A CN112775145 A CN 112775145A
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fly ash
stage
sodium
rinsing
chloride
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宁晓强
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Jiangshan Huding Environmental Protection Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • B09B3/80—Destroying solid waste or transforming solid waste into something useful or harmless involving an extraction step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B2101/00—Type of solid waste
    • B09B2101/30—Incineration ashes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F2001/007—Processes including a sedimentation step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/12—Halogens or halogen-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds

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  • Chemical & Material Sciences (AREA)
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  • Processing Of Solid Wastes (AREA)

Abstract

The invention discloses a high-efficiency secondary washing process for incineration fly ash of household garbage. The invention reduces the chlorine content entering the first-stage rinsing from the second-stage rinsing by carrying out electrolytic dechlorination on the effluent after the second-stage rinsing, simultaneously adopts medium-temperature electrolytic plate frame filter pressing, controls the water content of the filter pressing fly ash to be less than 25 percent, and reduces the dissolving and adsorbing effects of the bound water on chloride ions, thereby ensuring that the chloride ion content in the fly ash after the second-stage rinsing is less than 0.8 percent and meeting the requirement of entering a cement kiln. Meanwhile, the method of the invention promotes the chloride ion dissolving-out process in the first-stage rinsing process by reducing the chloride ion content in the two-stage rinsing press-filtered water, and is an efficient and economic household garbage fly ash washing process.

Description

Efficient secondary washing process for household garbage incineration fly ash
Technical Field
The invention relates to a household garbage fly ash recycling treatment process, in particular to a high-efficiency household garbage fly ash secondary washing treatment process, and belongs to the field of solid waste recycling.
Background
As the mainstream of domestic waste treatment is gradually transferred from sanitary landfill to waste incineration, the fly ash from domestic waste incineration becomes an important pollutant. The household garbage incineration fly ash refers to residues collected by a household garbage incineration power plant in a flue gas purification system, and contains organic pollutants such as benzene series substances and dioxin, trace heavy metals such as Pb and Cr, and the like. According to the standard for controlling pollution of domestic waste incineration (GB 18485-2014): the household garbage incineration fly ash is managed according to dangerous waste. Therefore, the fly ash must be collected separately, and must not be mixed with household garbage, incineration residue, etc., and other hazardous wastes.
The traditional domestic waste water adopts a three-stage washing process, and the chlorine content in the domestic waste fly ash can be only reduced to below 1.5%, so that the load of a subsequent cement kiln is increased, the chlorine content in the cement is required to be less than 0.06% for finished cement, and meanwhile, the excessively high chlorine content seriously corrodes a blast furnace rotary kiln for the cement kiln, so that the chlorine ion content in the fly ash is required to be controlled to be less than 1%, and the influence of the fly ash on the environment is reduced to the maximum extent on the basis of ensuring the cement quality.
Chinese literature adopts the treatment modes of calcium hydroxide, aluminate and other medicaments to carry out complexation removal on chloride ions in fly ash, and the main principle comprises Ca2+、Al3+With Cl in the fly ash water wash-Reaction to generate insoluble Ca-Al-Cl compound Ca2Al(OH)6Cl to remove Cl from the washing liquid-The reaction equation is as follows 2Ca (OH)2+NaCl+NaAlO2+2H2O+Ca2Al(OH)6While Cl ↓ +2NaOH can reduce chloride ions in an aqueous solution by adding Ca: Al: Cl ═ 2:1:1 (molar ratio), the addition cost is low, the efficiency is low for high-concentration chloride ions, and the practical operability is not strong. [ Wangxahu, Lushengyong, Chenxiangliang, etc.. Studies on removal of chloride ions from fly ash washing solution from incineration of household garbage [ J]Science of environmental science, 37(6) 2218-]
The Chinese patent 201810388415.9 discloses a garbage fly ash treatment system and a treatment process, wherein three-level rinsing is adopted in the process, primary rinsing wastewater enters a subsequent wastewater treatment system, and a flocculating agent Polyacrylamide (PAM) is added in the wastewater treatment, so that the viscosity of effluent is increased, and the risk of scaling of an evaporator is increased. Meanwhile, a large amount of fresh water is consumed in the three-stage rinsing, and the water-cement ratio in the treatment process is lack of detailed control, so that the water saving and the simplified operation are difficult to achieve.
The Chinese literature researches the research of biological dechlorination mechanism of the fly ash burned by the domestic garbage, and the analysis of synchrotron radiation X-ray diffraction shows that the soluble chlorine in the fly ash mainly exists in KCl, NaCl and CaClO and the insoluble chlorine mainly exists in AlOCl form, after the fly ash and the sludge are mixed and treated for 150 days, the chlorine content in the fly ash is obviously reduced, but the treatment time is too long and the fly ash has no practical operability [ Wu Boran, Wang Dong Yang, chai Li.
The Chinese invention patent 201910020356.4 describes a method for capturing heavy metals in the process of water washing pretreatment of fly ash, which captures heavy metals by sodium sulfide and ferrous sulfate. It uses ferrous sulfate to introduce sulfate, resulting in a crystalline salt containing a large amount of sodium/potassium sulfate. In addition, the main heavy metals after wastewater washing comprise amphoteric metals soluble under alkaline conditions, and the sludge contains ferrous sulfide due to excessive addition of sodium sulfide, so that the wastewater belongs to dangerous wastes, and the treatment cost of enterprises is increased.
The invention discloses a high-efficiency dechlorinating agent and a dechlorinating method for waste incineration fly ash. The electrochemical dechlorination is adopted, the electrode types and the dechlorination effect are not effectively described, and the improvement of the rinsing effect after dechlorination is not fully explained.
The Chinese invention patent 202010233283.X provides a preparation and application of a high-chlorine fly ash washing agent, chloride ions are removed by calcium ions and meta-aluminate, a large amount of additional agent is required to be added, and the preparation is similar to the research paper of Wangxahi et al, and has no operability in the actual use process.
The Chinese literature discusses that the liquid-ash ratio is 6: 1, performing grate waste incineration fly ash cleaning by adopting two-stage countercurrent rinsing, and finally cleaning the content of chloride ions to only 1.7 percent to cause serious influence on subsequent cement kiln mixed burning. Meanwhile, the liquid-cement ratio reaches 6: 1, the water consumption is higher, and the subsequent increasing energy consumption of wangting rain, tomb and dao and the like is increased; secondary countercurrent washing characteristics of the grate waste incineration fly ash [ J ]. Ergonomic edition, 2019,53(5):981-987], of Zhejiang university.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a high-efficiency secondary washing process for fly ash of household garbage, which comprises the following steps of controlling the water-ash ratio to be 1.2: 1-2: 1. secondary rinsing, maximally reducing the dosage of external chemicals, and realizing the resource treatment of the waste incineration fly ash through a scientific and refined management mode. Meanwhile, zero emission of water resources is realized, and the method is an economical, feasible and efficient resource treatment process for the household garbage incineration fly ash.
In order to achieve the technical purpose, the technical scheme of the invention is as follows:
a high-efficiency secondary washing process for fly ash of household garbage comprises the following steps:
(1) secondary rinsing: after the intermediate temperature electrolysis pressure filtrate after the second-stage fly ash rinsing enters a dechlorinating device for treatment, the content of chloride ions in the pressure filtrate is reduced, the dissolving and adsorption effects of the bound water on the chloride ions are reduced, and the first-stage fly ash rinsing treatment process is carried out; controlling the water-cement ratio (weight ratio) to be 1.2: 1-2: 1;
(2) wastewater/sewage treatment section: the pressure filtrate after the first stage of rinsing enters a sewage treatment system, and a mixed solution mainly containing potassium chloride and sodium chloride is formed through physicochemical processes of heavy metal removal, calcium and magnesium ion removal and the like;
(3) an evaporation and recycling section: an evaporative crystallization device is adopted to evaporate and crystallize the clean mixed solution of potassium chloride and sodium chloride, the condensate is recycled to the second-stage rinsing, the zero emission of wastewater is realized, the potassium and sodium of the crystallized salt are separated, and the product is sold after meeting the standard of GB/T5462 plus 2015 Industrial salt.
As a preferable scheme, the water-cement ratio is strictly controlled to be 1.2: 1-2: 1, so that the whole water consumption is saved to the maximum extent, and the volume and the energy consumption of the reactor are reduced under the same residence time.
Preferably, each stage of the two-stage rinsing adopts a stirring and air mixing stirring mode, and high-intensity stirring and aeration intensity can be promotedThe dynamic dissolution balance of intermolecular binding water, and the air stirring strength of 5-20 m3/m2The reaction time is 20-500W/m, and the stirring intensity of the stirrer is2﹒h。
Preferably, the main principle of electrochemical chlorine reduction is to change chlorine ions into the form of elemental chlorine through direct current or alternating current electrolysis, so that the chlorine ions are thoroughly separated from the solution. Or calcium hypochlorite crystals are formed, and chloride ions are separated out by means of crystallization. By converting the chloride ion into elemental chlorine or a crystalline form from which the solution can be separated.
According to the preferable scheme, the electrochemical electrolysis process adopts a rhodium-iridium composite high-energy electrode instead of a traditional lead electrode, generates chlorine gas through high-efficiency electrolysis, reduces the side reaction between polar plates, reduces the content of chloride ions in the two-stage rinsing pressure filtrate, and has the current density of 35-120A/m2。
As a preferred scheme, sodium carbonate is adopted to remove calcium and magnesium ions, sodium sulfide is adopted to remove heavy metals, ferrous sulfide is adopted to remove excessive sulfur ions, a plate-and-frame filter press is adopted for filtering separation, and hydrochloric acid is adopted for adjusting the pH value back. The molar ratio of sodium sulfide to heavy metal is 2: 1-5: 1, the molar ratio of ferrous sulfide to sodium sulfide is 2: 1-5: 1. adding sodium carbonate and calcium ions at a molar ratio of 1.5: 1-3: 1, thereby ensuring the sufficient removal of metal ions such as calcium, magnesium and the like.
As a preferred scheme, the top of the reactor adopts a negative pressure absorption mode, so that the generated volatile chlorine and hypochlorous acid can be stably absorbed by adopting alkali spraying through a negative pressure fan, and a sodium hypochlorite solution with a certain concentration is generated. Or adopting calcium hydroxide solution to absorb, and finally forming calcium hypochlorite crystal particles. In order to reduce chloride ions in the second-stage pressure filtrate as much as possible, the negative pressure above the solution is maintained between-150 Pa and-100 Pa, and the stirring intensity of air in the electrolytic solution is 5-20 m3/m2﹒h。
Preferably, the scale cleaning of the evaporator is performed by using 0.5% nitric acid, 0.5% hydrochloric acid, and 0.5% citric acid according to a ratio of 1: 1:1 (volume ratio) and then cleaning for 2-6 h. Through reasonably constructing the cleaning period, the cleaning period is 20-30 days, and even if the capacity of the evaporator is not reduced, the cleaning is carried out according to the cleaning period, so that the stable treatment efficiency is realized.
From the above description, it can be seen that the present invention has the following advantages:
1. the method of the invention constructs a closed processing system of secondary rinsing, wastewater treatment, evaporative concentration crystallization and condensate recycling secondary rinsing according to the chlorine-containing characteristic of the household garbage incineration fly ash. The whole process is not limited by water resources and disposal areas, and has wide and wide use scenes.
2. The process water-cement ratio of the method is 1.2: 1-2: 1, much lower than conventional processes by more than 3: 1 water to cement ratio.
3. The invention adopts two-stage rinsing, and the content of chloride ions in the second-stage rinsing pressure filtrate is reduced in the middle, so that the dechlorination efficiency of the first-stage rinsing is increased, and the overall water consumption is reduced.
4. The fly ash filtering mode of the electrode medium-temperature plate-and-frame filter press is adopted, and the dissolution and adsorption effects of intermolecular bound water on chloride ions can be reduced in the rinsing process by reducing the moisture in the fly ash to be below 25%.
5. The invention does not adopt flocculating agent in the whole course, thus ensuring the stable operation of the whole flow system.
6. The method of the invention has simple operation and strong adaptability, and can meet the treatment requirements of fly ash with different scales and different chlorine contents.
Drawings
FIG. 1 is a schematic process diagram of a household garbage fly ash recycling treatment process of the present invention;
FIG. 2 is a crystal principal component diagram of the surface of a triple-effect evaporative crystallizer treated by the process of the invention in example 7;
FIG. 3 is an SEM micrograph of the evaporator of example 8 taken 1000 times.
Detailed Description
The features of the invention will be further elucidated by the following examples, without limiting the claims of the invention in any way.
Example 1:
a high-efficiency secondary washing process for fly ash generated by burning household garbage comprises the following steps:
(1) secondary rinsing: after the second-stage fly ash rinsing pressure filtrate (after electrolysis and medium-temperature plate frame pressure filtration) enters a dechlorinating device for treatment, the content of chloride ions in the pressure filtrate is reduced, and the first-stage fly ash rinsing treatment process is carried out; controlling the water-cement ratio (weight ratio) to be 1.2: 1-2: 1.
(2) a wastewater treatment section: the pressure filtrate after the first-stage rinsing enters a sewage treatment system, a mixed solution mainly containing potassium chloride and sodium chloride is formed through physicochemical processes of heavy metal removal, calcium and magnesium ion removal and the like, solid-liquid separation adopts a plate-and-frame filter press, and the effluent is clear and transparent;
(3) an evaporation and recycling section: an evaporative crystallization device is adopted to evaporate and crystallize the clean mixed solution of potassium chloride and sodium chloride, the condensate is recycled to the second-stage rinsing, the zero emission of wastewater is realized, the potassium and sodium of the crystallized salt are separated, and the product is sold after meeting the standard of GB/T5462 plus 2015 Industrial salt.
After the treatment by the method, the purity of the evaporated and crystallized wet salt is higher than the standard (the content of sodium chloride is higher than 93.3%, the moisture content is less than 4%, the content of calcium and magnesium ions is less than 0.7%, and the content of sulfate ions is less than 1%) of the second grade or more in the refined industrial salt industry wet salt, and in practice, the content of sodium chloride in the operation process can be higher than 96%, the content of calcium and magnesium ions is less than 0.1%, and the content of sulfate ions is less than 0.3%.
Example 2:
aiming at fly ash of a self-provided incineration plant of a certain marketed company of Jiangsu Nantong, the content of chloride ions in the fly ash is 6.8 percent, and the specific surface area measured by BET (BET method) is 7.38m2/g。
TABLE 1 fly ash Properties of owned incineration plants of Nantong company
Sample (mg/g) Al As Ba Be Ca Cd Cr Cu Fe
Sample
1 113.5389252 0.08063812 1.464844 0.001363 4.688172 0.00227 0.102179 0.087601 60.50213
Sample 2 111.9070529 0.08895567 1.562096 0.002017 4.688741 0.001707 0.114353 0.078822 49.93023
(mg/g) K Li Mg Mn Na Ni P Pb Zn
Sample
1 8.316022099 0.20058764 4.85668 0.827225 6.652587 0.056953 0.644603 0.048714 0.091567
Sample 2 9.140050378 0.22234786 5.248136 0.903393 7.367884 0.060979 0.715202 0.050777 0.088581
After the treatment by the method of the embodiment, through two-stage water washing, the two-stage water washing time is respectively set to be 4h, and the water-cement ratio is 1.3: 1, filter pressing temperature of a plate-and-frame filter pressing device in electrolysis is 72 ℃, electrolysis current density is 85A/m2, and the molar ratio of sodium carbonate to calcium and magnesium ions is 1.8: 1, sodium sulfide and ferrous chloride are not needed to be added. The pH value of the plate-frame filter press is adjusted back to 7.3, so that after amphoteric ions such as aluminum ions are removed, clear liquid obtained through secondary plate-frame filter pressing enters an evaporator system, triple effect evaporation is adopted in the evaporator, a vacuumizing mode is adopted in the triple effect evaporation, the evaporation temperature is guaranteed to be lower than 60 ℃, the whole system stably operates, salt particles after crystallization are uniform, stable and white, and the crystallized chlorine salt is used by other enterprises in a park.
Example 3:
a high-efficiency secondary washing process for fly ash generated by burning household garbage comprises the following main properties of fly ash collection:
TABLE 2 analysis of properties of certain fly ash from Jiaxing, Zhejiang
Sample name (%) SiO2 Al2O3 Fe2O3 CaO MgO K2O N2O Cl
Jiaxing fly ash 12.86 4.63 0.86 32.86 0.96 3.42 3.86 7.2
Through the second-stage water washing, the time of the second-stage water washing is respectively set to be 3.6h, and the water-cement ratio is 1.3: 1, the filter-pressing temperature of the electrolytic medium-temperature plate-and-frame filter-pressing is set to be 65 ℃, and the electrolytic current density is 85A/m2The chlorine content of the fly ash after the filter pressing of the electrolytic medium-temperature plate frame is less than 0.8 percent, and the molar ratio of sodium carbonate to calcium and magnesium ions is 1.8: 1, sodium sulfide and ferrous chloride are not needed to be added. The pH value of the plate frame filter pressing liquid is adjusted back to 7.3, so that clear liquid obtained through secondary plate frame filter pressing enters an evaporator system after amphoteric ions such as aluminum ions are removed, triple effect evaporation is adopted in the evaporator, a vacuumizing mode is adopted in the triple effect evaporation, the evaporation temperature is guaranteed to be lower than 60 ℃, the whole system stably operates, the content of wet salt and sodium chloride is higher than 97.42%, and the requirement of industrial salt high-grade products is met.
Example 4:
a high-efficiency secondary washing process for fly ash generated by burning household garbage comprises the following main properties of fly ash collection:
TABLE 2 analysis of properties of certain fly ash from Jiaxing, Zhejiang
Sample name (%) SiO2 Al2O3 Fe2O3 CaO MgO K2O N2O Cl
Jiaxing fly ash 16.86 3.53 0.36 30.56 0.96 3.42 3.86 12.2
Through the second-stage water washing, the time of the second-stage water washing is respectively set to be 3.5h, and the water-cement ratio is 1.5: 1, the filter pressing temperature of the electrolytic medium-temperature plate-and-frame filter pressing is set to be 75 ℃, and the electrolytic current density is 80A/m2The molar ratio of sodium carbonate to calcium and magnesium ions is 1.5: 1, sodium sulfide and ferrous chloride are not needed to be added. The pH value of the plate-frame pressure filtrate is adjusted back to 7.3, so that clear liquid obtained by secondary plate-frame pressure filtration enters an evaporator system after amphoteric ions such as aluminum ions are removed, triple-effect evaporation is adopted in the evaporator, a security filter is arranged in front of the evaporator, and a vacuumizing mode is adopted in the triple-effect evaporation to ensure evaporationThe temperature is less than 65 ℃, the whole system operates stably, the content of wet salt sodium chloride is 96.2 percent, and the requirement of industrial salt high-grade products is met.
Example 5:
a high-efficiency secondary washing process for fly ash generated by burning household garbage aims at Jiaxing low-chlorine ash, the chlorine content is 5.6%, the chlorine ion content of secondary rinsing effluent is 1.2%, the chlorine ion content in pressure filtrate directly entering a primary rinsing stage is 4.3%, and the chlorine content of fly ash generated after pressure filtration of an electrolytic medium-temperature plate-and-frame filter press is 1.1%; after the second-stage rinsing passes through the dechlorinating device, the content of chloride ions can be reduced to 0.4%, the first-stage rinsing is carried out, the content of chloride ions in the pressure filtrate after the rinsing is 4.6%, and the chlorine content of fly ash after the pressure filtration of the electrolytic medium-temperature plate-and-frame filter press is 0.8%, so that the treatment efficiency of the cement kiln is greatly improved, and the economic benefit of enterprises is enhanced.
Example 6:
a high-efficiency secondary washing process for fly ash generated by burning household garbage aims at Jiaxing low-chlorine ash, and when the filter pressing temperature is 60 ℃, the chlorine content of the fly ash subjected to filter pressing by an electrolytic medium-temperature plate-and-frame filter press is 0.95 percent; when the filter pressing temperature is 70 ℃, the chlorine content of the fly ash obtained after filter pressing of the electrolytic medium-temperature plate-and-frame filter press is 0.80 percent; when the filter pressing temperature is 80 ℃, the chlorine content of the fly ash obtained after filter pressing of the electrolytic medium-temperature plate-and-frame filter press is 0.78%; when the filter pressing temperature is 90 ℃, the chlorine content of the fly ash obtained after filter pressing by the electrolytic medium-temperature plate-and-frame filter press is 0.77 percent; therefore, the filter pressing temperature of the electrolysis medium-temperature filter pressing plate frame is 70 ℃, so that the treatment efficiency of the cement kiln is greatly improved, and the economic benefit of enterprises is enhanced.
Example 7:
a two-stage water washing process for high-efficiency fly ash generated by burning domestic garbage aims at Jiaxing low-chlorine ash, and the main crystallization components on the surface of a three-effect evaporation crystallizer after the Jiaxing low-chlorine ash is treated by the process are shown in figure 2.
As can be seen from fig. 2, the stainless steel surface can be kept as smooth as new by cleaning with 0.5% nitric acid, 0.5% hydrochloric acid, 0.5% citric acid, and 0.1% APG.
Example 8:
a high-efficiency secondary washing process for fly ash generated by burning household garbage aims at Jiaxing low-chlorine ash, and is characterized in that after the Jiaxing low-chlorine ash is washed by mixed solution with the concentration of 0.5% nitric acid, 0.5% hydrochloric acid, 0.5% citric acid and 0.1% APG, the surface of an evaporator is smooth, no scaling substances exist on the surface, see SEM picture and see picture 3.
It should be understood that the detailed description of the invention is merely illustrative of the invention and is not intended to limit the invention to the specific embodiments described. It will be appreciated by those skilled in the art that the present invention may be modified or substituted equally as well to achieve the same technical result; as long as the use requirements are met, the method is within the protection scope of the invention.

Claims (10)

1. A high-efficiency secondary washing process for fly ash generated by burning household garbage is characterized by comprising the following steps: (1) secondary rinsing: after the second-stage fly ash rinsing pressure filtrate enters a dechlorinating device for treatment, reducing the content of chloride ions and the content of bound water in the pressure filtrate, and then entering a first-stage fly ash rinsing treatment process; controlling the water-cement ratio to be 1.2: 1-2: 1; the filter press adopts a medium-temperature electrolytic plate-and-frame filter pressing process to ensure that the water content of the fly ash after filter pressing is less than 25 percent;
(2) a wastewater treatment section: the pressure filtrate after the first stage of rinsing enters a sewage treatment system, and a mixed solution mainly containing potassium chloride and sodium chloride is formed through physicochemical processes of heavy metal removal, calcium and magnesium ion removal and the like;
(3) an evaporation and recycling section: and (3) evaporating and crystallizing the clean mixed solution of potassium chloride and sodium chloride by using an evaporation crystallization device, recycling the condensate to the second-stage rinsing, and separating crystallized salt potassium and sodium for sale.
2. The treatment process according to claim 1, wherein each stage of the secondary rinsing in the step (1) adopts a mode of stirring by a stirrer and mixing and stirring by air, and the intensity of the stirring by the air is 5-20
m3/m2H, the stirring intensity of the stirrer is 20-500W/m2·h。
3. The treatment process of claim 1, wherein sodium carbonate is adopted to remove calcium and magnesium ions in the wastewater treatment, sodium sulfide is adopted to remove heavy metals, and sodium sulfide can be selectively added according to fly ash components; removing excessive sulfur ions from ferrous sulfide, separating by using a plate-and-frame filter press, and adjusting the pH value by using hydrochloric acid.
4. The process of claim 1, wherein potassium chloride and sodium chloride are crystallized by triple effect evaporation or MVR and sodium and potassium are separated according to different boiling points to obtain white sodium chloride and potassium chloride crystals.
5. The treatment process of claim 1, wherein in the step (1), the plate-frame filter pressing adopts medium-temperature electrolytic plate-frame filter pressing equipment, the electrolytic electrode adopts a rhodium-iridium composite anti-pollution electrode, and the medium-temperature drying temperature is controlled to be 65-90 ℃.
6. The process of claim 1, wherein the dechlorination process employs a rhodium iridium composite electrode to reduce the chloride ion content in the second stage rinse press filtrate by efficiently electrolyzing the chlorine gas with a current density of 35 to 120A/m2。
7. The treatment process as claimed in claim 1, wherein the top of the reactor adopts a negative pressure absorption mode to ensure that the generated volatile chlorine and hypochlorous acid can be stably absorbed by a negative pressure fan through alkali spraying to generate a sodium hypochlorite solution with a certain concentration; or adopting calcium hydroxide solution to absorb, and finally forming calcium hypochlorite crystal particles; in order to reduce chloride ions in the second-stage pressure filtrate as much as possible, the negative pressure above the solution is maintained between-150 Pa and-100 Pa, and the stirring intensity of air in the electrolytic solution is 5-20 m3/m2·h。
8. A process according to claim 3, wherein the molar ratio of sodium sulphide to heavy metal in the wastewater is from 2: 1-5: 1, the molar ratio of ferrous sulfide to sodium sulfide is 2: 1-5: 1.
9. the process of claim 2, wherein the molar ratio of sodium carbonate to calcium ion is 1.5: 1-3: 1.
10. the method according to claim 4, wherein the evaporator is cleaned by using 0.5% nitric acid, 0.5% hydrochloric acid, 0.5% citric acid or 0.1% APG for 2-6 h.
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Application publication date: 20210511