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CN-122010153-A - Method for preparing polyaluminum chloride by electrocatalytically activating fly ash

CN122010153ACN 122010153 ACN122010153 ACN 122010153ACN-122010153-A

Abstract

The invention provides a method for preparing polyaluminium chloride by electrocatalytically activating fly ash, which belongs to the technical field of fly ash recycling, and comprises the steps of taking the fly ash, crushing the fly ash, adding electrolyte containing sodium bicarbonate, carbon paper is used as a cathode and an anode respectively, the electric catalytic reaction is carried out by electrifying, after the electric catalytic reaction is finished, al (OH) 3 sediment is obtained by filtering and regulating the pH value, and Al (OH) 3 sediment is polymerized to obtain polyaluminium chloride. The invention overcomes the problems of high energy consumption and high pollution of the existing alkali activation and provides a green and efficient method for preparing polyaluminium chloride by activating the fly ash by the electrocatalytic activation method, wherein the reaction temperature is normal temperature, the energy consumption can be obviously reduced, the energy utilization efficiency is improved, and the dissolution rate of the alumina can reach more than 95 percent.

Inventors

  • Pei Hongjing
  • ZHOU JINMING
  • SUN XINRU
  • DONG XUEYING
  • CAO HEMING
  • SHI YUEMEI
  • ZHAO JINGMIN
  • NI ZHIYUAN
  • LI XIANQI
  • XIAO XIONG
  • WANG HAOWEI

Assignees

  • 唐山三友化工股份有限公司

Dates

Publication Date
20260512
Application Date
20260225

Claims (10)

  1. 1. A method for preparing polyaluminium chloride by electrocatalytically activating fly ash is characterized in that the method is characterized in that after the fly ash is crushed, electrolyte containing sodium bicarbonate is added, carbon paper is respectively used as a cathode and an anode, the electrocatalytic reaction is carried out by electrifying, after the electrocatalytical reaction is finished, the pH value is regulated by filtering, al (OH) 3 sediment is obtained, and Al (OH) 3 sediment is polymerized, so that the polyaluminium chloride is obtained.
  2. 2. The method for preparing polyaluminum chloride from electrocatalytically activated fly ash according to claim 1, wherein the method comprises the following steps: crushing, namely crushing and sieving the fly ash to obtain the sieved fly ash; Preparing electrolyte, namely adding water into NaOH and/or KOH and NaHCO 3 to prepare the electrolyte; electrocatalytic reaction, namely adding the screened fly ash into electrolyte, wherein both the cathode and the anode are carbon paper, electrifying to perform electrocatalytic reaction, and continuing the reaction after stopping electrifying to obtain an electrocatalytic system; Precipitating by filtering the electrocatalytic system, regulating pH value of the obtained filtrate to precipitate Al (OH) 3 , drying the Al (OH) 3 precipitate to obtain Al (OH) 3 ; and (3) polymerization, namely dissolving Al (OH) 3 in hydrochloric acid, reacting, and adding an initiator to polymerize to obtain the solid polyaluminium chloride.
  3. 3. The method for preparing polyaluminum chloride by electrocatalytically activating fly ash according to claim 1 or 2, wherein the voltage of the electrocatalytic reaction is 0.3-0.8V and the electrifying time is 1-3 h.
  4. 4. The method for preparing polyaluminum chloride by electrocatalytically activating fly ash according to claim 1 or 2, wherein the weight-volume ratio of the fly ash to the electrolyte is 1:30-100.
  5. 5. The method for preparing polyaluminum chloride from electrocatalytically activated fly ash according to claim 1 or 2, wherein the final value of the pH value is adjusted to 9.5-10.5 after filtration.
  6. 6. The method for preparing polyaluminum chloride by electrocatalytically activating fly ash according to claim 2, wherein in the electrocatalytic process, the total concentration of NaOH and/or KOH in the electrolyte is 0.5-1.5M, and the concentration of NaHCO 3 is 0.5-1.2M.
  7. 7. The method for preparing polyaluminum chloride by electrocatalytically activating fly ash according to claim 2 or 6, wherein the continuous reaction time is 1-5 h after the energization is stopped in the electrocatalytic process.
  8. 8. The method for preparing polyaluminum chloride from electrocatalytically activated fly ash according to claim 2 or 6, wherein the weight-to-volume ratio of Al (OH) 3 to hydrochloric acid in the polymerization process is 1:10-50; The concentration of the hydrochloric acid is 15-36wt%.
  9. 9. The method for preparing polyaluminum chloride from electrocatalytically activated fly ash according to claim 2 or 6, wherein the weight-to-volume ratio of hydrochloric acid to initiator is 10-2:1.
  10. 10. The method for preparing polyaluminum chloride from electrocatalytically activated fly ash according to claim 2 or 6, wherein the initiator is calcium aluminate or sodium hydroxide.

Description

Method for preparing polyaluminum chloride by electrocatalytically activating fly ash Technical Field The invention relates to the technical field of fly ash recycling, in particular to a method for preparing polyaluminium chloride by electrocatalytically activating fly ash. Background Fly ash is the main solid waste discharged from coal-fired power plants, the annual output is over 6 hundred million tons, the accumulated stock quantity is over 30 hundred million tons, a large amount of land is occupied, and serious environmental risks are caused by dust and heavy metal infiltration. The content of Al 2O3 in the fly ash is generally 15-35%, and part of high-alumina coal can reach more than 45%, so that the fly ash is an important non-traditional aluminum resource, and aluminum in the fly ash is efficiently extracted and prepared into a flocculant with high added value, namely polyaluminium chloride (PAC), so that the bauxite supply pressure can be relieved, the large-scale high-value utilization of solid waste can be realized, and the requirements of double-carbon strategy and circular economy development are met. At present, the main flow route for industrially extracting aluminum from fly ash and preparing PAC is a high-temperature alkali activation-acid dissolution-basicity regulation and control process, which comprises the following steps: 1) The activation stage, namely mixing the fly ash with auxiliary agents such as Na 2CO3, caO or CaCl 2·2H2 O and roasting for 0.5-2 hours at 800-1300 ℃ to convert inert mullite and quartz phases into readily soluble chamotte such as nepheline, gehlenite or gehlenite; 2) Leaching clinker by hydrochloric acid or sulfuric acid to obtain an aluminum salt solution with the Al 3+ concentration of about 80-120 g/L; 3) And in the polymerization stage, calcium aluminate powder or NaOH is added to adjust the basicity to 60-80%, and the liquid PAC is prepared after curing. Although the technology has been demonstrated in kilotons, the following prominent problems exist: ① The method has the advantages of high energy consumption, high calcination temperature of more than or equal to 800 ℃, comprehensive energy consumption of 2.8-3.5 tons of standard coal per ton of Al 2O3, serious deviation from a double-carbon target, large ② pollution, high emission of CO 2、SO2 and dust released by high-temperature alkaline calcination, high emission of CO 2 per ton of Al 2O3 of more than or equal to 2t, high production of alkaline waste residue of 0.6-0.8 t, severe ③ equipment, high-temperature equipment such as a rotary kiln, a vertical kiln and the like, fire resistance, corrosion resistance and continuous operation, high investment and maintenance cost, limited ④ dissolution rate, limited conversion rate of fly ash, common Al 2O3 dissolution rate of only 70-85 percent, aluminum content of tailings of more than 10 percent, low resource utilization rate, and ⑤ secondary pollution risk, difficult disposal of high-basicity waste liquid and alkaline residues, and easy soil salinization and water eutrophication. Therefore, it is necessary to develop a new technology for activating the fly ash with high dissolution rate of Al 2O3 at normal temperature and pressure, low energy consumption and low emission. Disclosure of Invention The invention aims at the problems and relates to a method for preparing polyaluminum chloride by electrocatalytically activating fly ash. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: A process for preparing polyaluminium chloride from powdered coal ash by electrocatalytically activating includes such steps as pulverizing powdered coal ash, adding electrolyte containing sodium hydrogen carbonate, electrifying to obtain electrocatalytic reaction, filtering, regulating pH value to obtain Al (OH) 3 deposit, and polymerizing Al (OH) 3 deposit. Further, the method comprises the steps of: crushing, namely crushing and sieving the fly ash to obtain the sieved fly ash; Preparing electrolyte, namely adding water into NaOH and/or KOH and NaHCO 3 to prepare the electrolyte; electrocatalytic reaction, namely adding the screened fly ash into electrolyte, wherein both the cathode and the anode are carbon paper, electrifying to perform electrocatalytic reaction, and continuing the reaction after stopping electrifying to obtain an electrocatalytic system; Precipitating by filtering the electrocatalytic system, regulating pH value of the obtained filtrate to precipitate Al (OH) 3, drying the Al (OH) 3 precipitate to obtain Al (OH) 3; And (3) polymerization, namely dissolving Al (OH) 3 in hydrochloric acid, reacting, and adding an initiator to polymerize to obtain solid polyaluminium chloride (PAC for short). Further, the voltage of the electrocatalytic reaction is 0.3-0.8V, and the electrifying time is 1-3 h. Further, the weight-volume ratio of the fly ash to the electrolyte is 1:30-100. Further, after filtration, the final value of