CN-117361593-B - Method for preparing magnesium fluoride from household garbage incineration fly ash

Abstract

The invention discloses a method for preparing magnesium fluoride from household garbage incineration fly ash, which comprises the steps of carrying out acid washing/water washing on household garbage fly ash to obtain water-based fly ash slurry, carrying out solid-liquid separation on the slurry to obtain coarse brine containing calcium and magnesium, carrying out weight removal on the coarse brine containing calcium and magnesium, standing and settling, carrying out denitrification, oxidation and neutralization reaction on clear liquid, carrying out solid-liquid separation to obtain refined brine containing calcium and magnesium, carrying out calcium removal on the refined brine containing calcium and magnesium, carrying out solid-liquid separation to obtain refined magnesium water, carrying out alkali adding and magnesium removal on the refined brine containing calcium and magnesium hydroxide, preparing the magnesium hydroxide into slurry with a certain concentration, slowly adding the slurry into a pretreated waste hydrofluoric acid solution, fully stirring, carrying out solid-liquid separation, carrying out three-stage countercurrent oxidation washing on the obtained solid, and carrying out thermal desorption to obtain a magnesium fluoride product.

Inventors

• MA JUNJUN
• HAN ZHENGCHANG
• ZHU JIAMING
• BU XULING
• TAO ZHIHUI
• HUANG HAIFENG
• CHEN XIAO

Assignees

• 南京格洛特环境工程股份有限公司

Dates

Publication Date

20260508

Application Date

20231013

Claims (5)

1. 1. A method for preparing magnesium fluoride from household garbage incineration fly ash is characterized by comprising the following specific steps: (1) Washing the household garbage fly ash with acid and water to obtain a water-based fly ash slurry, and carrying out solid-liquid separation on the water-based fly ash slurry to obtain coarse brine with high calcium and magnesium content; (2) Removing the weight of the coarse brine with high calcium and magnesium content obtained in the step (1), standing and settling, performing denitrification, oxidation and neutralization reaction on clear liquid, and performing solid-liquid separation to obtain refined brine with calcium and magnesium content; (3) Carrying out a calcium removal procedure on the refined brine containing calcium and magnesium obtained in the step (2), and carrying out solid-liquid separation to obtain refined brine containing magnesium; (4) S1, adding a magnesium removal agent into the magnesium refined brine obtained in the step 3, carrying out solid-liquid separation to obtain magnesium removal water and magnesium salt, preparing the magnesium salt into slurry with the mass concentration of 10-20% for later use, wherein the magnesium removal agent is any one of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, the adding amount of the magnesium removal agent is 0.1-5% of the total mass of the solution, and the magnesium removal pH is 11-12; S2, adding a pH regulator into the waste hydrofluoric acid to convert the waste hydrofluoric acid into milder low-acidity waste liquid, wherein the pH regulator is soluble hydroxide or carbonate, the adding amount of the pH regulator is 4-40% of the total mass of the solution, and the pH of the low-acidity waste liquid after regulation is 1-3; S3, adding a weight removing agent into the low-acidity waste liquid regulated in the step S2, removing heavy metals under an acidic condition, and performing solid-liquid separation to obtain weight removing waste water, wherein the weight removing agent is sodium sulfide, potassium sulfide and potassium ferrocyanide, the use amount of the weight removing agent is 0.3-0.8% of the total mass of the solution, and the weight removing reaction pH is 1-3; S4, slowly dropwise adding magnesium hydroxide or magnesium carbonate slurry prepared in the S1 into the low-acidity hydrofluoric acid waste liquid heavy water obtained in the S3 according to the molar ratio Mg: F=0.5-1:1, stirring for reaction, wherein the dropwise adding time is 1-2 h, continuing to react for 0.5-1.5 h, and obtaining a magnesium oxide crude product after solid-liquid separation, wherein the pH value of a reaction end point is controlled to be 4-5; (5) And (3) washing the magnesium fluoride crude product obtained in the step (4) through three-stage countercurrent oxidation, and then carrying out thermal desorption and drying to obtain a magnesium fluoride product.
2. 2. The method for preparing magnesium fluoride from household garbage incineration fly ash according to claim 1, wherein in the step (1), the washing time is 15-60 min, the mass ratio of the household garbage incineration fly ash to acid added by acid washing and water washing to water is 1:2-3:2-3, the acid concentration is 6-10 mol/L, and the acid is any one or more of hydrochloric acid, sulfuric acid and nitric acid.
3. 3. The method for preparing magnesium fluoride from household garbage incineration fly ash, which is characterized by comprising the specific steps of adding a weight removing agent, removing weight, settling and separating to obtain black heavy metal mud, adding a denitrification agent to denitrify the obtained filtrate, adding an oxidant for heterogeneous catalytic oxidation, neutralizing to obtain yellow heavy metal mud, and performing solid-liquid separation to obtain filtrate which is calcium-magnesium-containing refined brine.
4. 4. The method for preparing magnesium fluoride from household garbage incineration fly ash, which is characterized in that the weight removing time is 0.5-1 h, the denitrification and heterogeneous catalytic oxidation time is 1-2 h, the weight removing agent is sodium sulfide, potassium sulfide and potassium ferrocyanide, the weight removing agent is 0.3-0.8% of the total mass of the solution, the weight removing agent is sodium hypochlorite or sodium chlorate, the weight removing agent is 0.5-1% of the volume of the solution, the oxidant is any one of hydrogen peroxide, ozone, potassium permanganate, sodium persulfate and potassium persulfate, and the oxidant is 1-5% of the volume of the solution.
5. 5. The method for preparing magnesium fluoride from household garbage incineration fly ash, which is characterized in that the specific step (3) is that a calcium-removing agent is added into the calcium-magnesium-containing refined brine obtained in the step (2), and the magnesium-containing refined brine is obtained through stirring reaction, sedimentation and solid-liquid separation, wherein the calcium-removing agent is sodium carbonate, potassium carbonate or sulfuric acid, the adding amount of the calcium-removing agent is 0.3-30% of the total mass of the solution, and the calcium-removing pH is 5-7.

Description

Method for preparing magnesium fluoride from household garbage incineration fly ash Technical Field The invention belongs to the field of waste resource utilization, and particularly relates to a method for preparing magnesium fluoride from household garbage incineration fly ash. Background The current national production amount of the household garbage incineration fly ash is about 900 ten thousand tons/year, and along with the improvement of the household garbage collection amount and the incineration power generation ratio, the peak amount of the household garbage incineration fly ash reaches about 1500 ten thousand tons, and the fly ash mainly contains a large amount of soluble salts and water. The waste incineration fly ash contains a large amount of soluble salts, calcium, silicon, aluminum, active carbon, lead, zinc, copper, dioxin and other substances, and contains 2% -5% of magnesium element. The fly ash recycling technology mainly aims at removing or recycling dioxins, heavy metals and soluble salts, but basically does not involve the removal or recycling of magnesium element. The etching waste liquid mainly comes from the cleaning process and the etching process. The glass etching liquid is based on the principle that hydrofluoric acid reacts with glass (SiO 2) to generate fluosilicic acid (H2 SiF 6) which is an ageing substance and glass slag and silicic acid (water glass) in the reaction process. With the gradual consumption of hydrofluoric acid and the continuous increase of the concentration of the aging substances, the aging of the bath solution of the glass etching bath can be caused, the etching rate is reduced, and the etching failure rate is increased. The traditional method for solving the problems is to treat and discharge the aged bath solution as waste acid and rebuild the bath to prepare etching solution. However, a relatively high concentration of hydrofluoric acid is also present in most spent acid. Taking fluorine-containing wastewater generated in etching process and cleaning process in the chip production process of electronic factory as an example, the ions contained in the wastewater contain SO 42- with higher concentration, organic matters, trace metal impurity ions and the like besides F -. The common means for treating the fluoride-containing waste acid at present is to add alkaline metal oxide to neutralize and realize neutral sludge, and the recycling of etching solution is not realized. The invention creatively provides a technical scheme for preparing magnesium fluoride from the household garbage incineration fly ash, realizes the reclamation of magnesium ions, solves the problem of treatment of waste hydrofluoric acid containing etching waste liquid, and has great significance in the fields of dangerous solid waste treatment and high-quality reclamation utilization. Disclosure of Invention The invention discloses a method for preparing magnesium fluoride from household garbage incineration fly ash, which is characterized in that the household garbage fly ash is firstly subjected to acid washing/water washing to obtain water-based fly ash slurry, the slurry is subjected to solid-liquid separation to obtain coarse brine with high calcium and magnesium content, solids enter the next process, gao Hangai magnesium coarse brine is subjected to a weight removal process, standing and settling, clear liquid is subjected to denitrification, oxidation and neutralization reaction, solid-liquid separation to obtain refined brine with calcium and magnesium content, the refined brine with calcium and magnesium content is subjected to a calcium removal process, the solid-liquid separation to obtain refined brine with magnesium hydroxide, the magnesium hydroxide is prepared into slurry with certain concentration, the slurry is slowly added into pretreated waste hydrofluoric acid, the mixture is fully stirred, the solid-liquid separation is carried out, and the obtained solid is subjected to three-stage countercurrent oxidation washing and then is subjected to thermal desorption drying to obtain a high-purity magnesium fluoride product. In order to achieve the above purpose, the technical scheme of the invention is as follows: a method for preparing magnesium fluoride from household garbage incineration fly ash comprises the following specific steps: (1) Washing the household garbage fly ash with acid and water to obtain a water-based fly ash slurry, and carrying out solid-liquid separation on the water-based fly ash slurry to obtain coarse brine with high calcium and magnesium content; (2) Removing the weight of the coarse brine with high calcium and magnesium content obtained in the step (1), standing and settling, performing denitrification, oxidation and neutralization reaction on clear liquid, and performing solid-liquid separation to obtain refined brine with calcium and magnesium content; (3) Carrying out a calcium removal procedure on the refined brine containing calcium and ma