CN-122010069-A - Wastewater recycling method for preparing ferric phosphate based on raffinate acid as raw material

CN122010069ACN 122010069 ACN122010069 ACN 122010069ACN-122010069-A

Abstract

The invention relates to the technical field of ferric phosphate production, and discloses a wastewater recycling method for preparing ferric phosphate based on raffinate acid as a raw material, which comprises the steps of 1) dissolving and removing impurity of ferrous sulfate heptahydrate to obtain ferrous sulfate solution A; 2) extracting Yu Suan, removing impurities with ammonia water to obtain a phosphorus salt solution B, mixing the phosphorus salt solution B with an oxidant to obtain a mixed solution C, washing a phosphorus salt filter cake with water for dilution with raffinate acid, 3) reacting the mixed solution C with the solution A, carrying out primary filtering and washing on slurry to obtain a synthetic filter cake, 4) adding phosphoric acid into the synthetic filter cake after size mixing, heating and ageing, and carrying out secondary washing, drying and calcining on the ageing filter cake to obtain the battery grade ferric phosphate. The invention uses multistage water circulation to recycle the phosphorus salt filter cake washing water, the first/second grade washing water recycled according to conductivity and the regenerated mother liquor for raw material dilution, dissolution and filter cake washing and size mixing to form wastewater closed circulation, and uses raffinate acid to replace the traditional phosphorus source, thereby realizing the high-efficiency recovery of water resources and phosphorus resources while reducing the cost.

Inventors

WANG JUNTING
MA HANG
ZHA ZUOTONG
WAN BANGLONG
WEI XING
LUO ZIYI
Lei XuSong
ZHANG ZHENHUAN
CHEN YU

Assignees

云南云天化股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260113

Claims (8)

1. The method for recycling the wastewater generated in the preparation of the ferric phosphate based on the raffinate acid as the raw material is characterized by comprising the following steps: 1) Mixing ferrous sulfate heptahydrate, ammonia water and dissolved water, performing impurity removal reaction, and filtering to obtain ferrous sulfate solution A; 2) Mixing raffinate acid, ammonia water and dilution water, performing impurity removal reaction, filtering to obtain a phosphorus salt solution B and a phosphorus salt filter cake, mixing the phosphorus salt solution B with an oxidant to obtain a mixed solution C, washing the phosphorus salt filter cake, and recycling generated washing water as dilution water of the raffinate acid; 3) Carrying out a synthesis reaction on the mixed solution C and the ferrous sulfate solution A, and filtering the obtained slurry to obtain a synthesized filter cake and a first-stage mother solution; 4) Mixing the synthesized filter cake with water for size mixing, adding phosphoric acid into the mixture for temperature rising and aging, filtering the aged slurry to obtain an aged filter cake and secondary mother liquor, and performing secondary washing, drying, calcining and crushing on the aged filter cake to obtain battery-grade ferric phosphate; The primary washing water generated by washing the synthesized filter cake and the secondary washing water generated by washing the aged filter cake are recycled in a grading way according to the conductivity of the primary washing water and the secondary washing water, and after the primary mother liquor and/or the secondary mother liquor are subjected to impurity removal treatment, the obtained recycled water is recycled to be used as at least one of the dissolved water of ferrous sulfate heptahydrate, the washing water of the phosphate filter cake, the washing water of the synthesized filter cake and the size mixing water of the synthesized filter cake.
2. The method for recycling wastewater from iron phosphate production based on raffinate as claimed in claim 1, wherein the dilution water is pure water when step 2) is performed for the first time.
3. The method for recycling wastewater generated in the preparation of ferric phosphate based on raffinate acid as a raw material according to claim 1, wherein the wastewater of the phosphate filter cake as dilution water is recycled, and the amount of the wastewater is 30% -50% of the mass of the raffinate acid.
4. The recycling method of wastewater for preparing ferric phosphate based on raffinate acid as a raw material, which is characterized in that the recycling mode of the primary washing water is that the primary washing water is subjected to impurity removal treatment together with primary mother liquor when the conductivity of the primary washing water is more than or equal to 10ms/cm, and is used as washing water of a phosphorus salt filter cake before the next synthesis reaction when the conductivity of the primary washing water is less than 10 ms/cm.
5. The recycling method of wastewater for preparing ferric phosphate based on raffinate acid as a raw material, which is characterized in that the recycling mode of the secondary washing water is that the secondary washing water is used as washing water for a filter cake at the front end of the next aging reaction when the conductivity of the secondary washing water is more than or equal to 3ms/cm, and is used as filter cake slurry mixing water before aging when the conductivity of the secondary washing water is less than 3 ms/cm.
6. The method for recycling wastewater generated in the preparation of ferric phosphate based on raffinate acid as a raw material according to claim 4, wherein the primary mother liquor and/or primary washing water with the conductivity of more than or equal to 10ms/cm is mixed with a impurity removing agent before recycling, and the mixture is filtered after the pH value is adjusted to 8-12, so that the recycled water is obtained.
7. The method for recycling wastewater generated in the preparation of ferric phosphate based on raffinate acid as a raw material according to claim 5, wherein the secondary mother liquor is mixed with a impurity removing agent before recycling, and is filtered after the pH value is adjusted to 8-12, so that the recycled water is obtained.
8. The method for recycling wastewater generated in the preparation of ferric phosphate by using raffinate acid as a raw material according to claim 6 or 7, wherein the impurity removing agent is any one of magnesium oxide, aluminum chloride, sodium carbonate or calcium hydroxide.

Description

Wastewater recycling method for preparing ferric phosphate based on raffinate acid as raw material Technical Field The invention relates to the technical field of iron phosphate production, in particular to a wastewater recycling method for preparing iron phosphate based on raffinate acid as a raw material. Background Iron phosphate is used as a core precursor of a lithium iron phosphate battery, and is driven by new energy automobiles and energy storage industries, so that the demand is continuously and explosive-type. However, the conventional ammonium process relies on monoammonium phosphate as a phosphorus source, and the increase in raw material cost leads to a decrease in profit. The wastewater produced in the existing ferric phosphate production process contains high-concentration phosphate and sulfate, the wastewater can meet the water outlet requirement only by high-energy-consumption technology treatment such as multi-effect evaporation, membrane separation and the like, the wastewater treatment energy consumption is high, the impurity content of raw materials is high in the ferric phosphate production process, and the resource waste is caused by using high-purity water in a whole line. The problems can not be effectively solved in the prior art, so that the production cost of the ferric phosphate can not be effectively reduced. The raw material cost of the iron phosphate production can be obviously reduced by taking the raffinate acid as the raw material, and partial enterprises already finish the application of the production technology, but the raffinate acid is taken as the raw material, more impurities are introduced, the wastewater treatment and recycling application difficulty is higher, and the phosphorus yield of the raffinate acid treatment is lower. The extract Yu Suan has complex element composition and higher content, so that the wastewater treatment complexity of the iron phosphate production system is obviously improved. Based on the characteristics, the technical standard of wastewater treatment needs to be further improved, so that a more efficient wastewater recycling and treatment system needs to be constructed to cope with the problems caused by the inherent properties of the raw materials. Meanwhile, the yield of phosphorus in the raffinate acid treatment process is low, so that the cost advantage of the method is difficult to fully develop. For this problem, the effective recovery and utilization of phosphorus is achieved by means of a reasonable washing process, which also depends on a scientific and reasonable wastewater recycling mechanism. In addition, the waste water generated by the raffinate acid treatment also contains various pollutants such as heavy metal ions, if the treatment is improper, serious threat is caused to the environment, and the urgency and the necessity of constructing a systematic and scientific waste water treatment and recycling system are further highlighted. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a wastewater recycling method for preparing ferric phosphate based on raffinate acid as a raw material, which is characterized in that the cost is obviously reduced, and the high-efficiency recovery and low emission of resources can be realized through a multi-stage water recycling system and the closed-loop recycling of waste acid and washing water as well as low energy consumption treatment. The scheme of the invention is as follows: the method for recycling the wastewater generated in the preparation of the ferric phosphate based on the raffinate acid as the raw material is characterized by comprising the following steps: 1) Mixing ferrous sulfate heptahydrate, ammonia water and dissolved water, performing impurity removal reaction, and filtering to obtain ferrous sulfate solution A; 2) Mixing raffinate acid, ammonia water and dilution water, performing impurity removal reaction, filtering to obtain a phosphorus salt solution B and a phosphorus salt filter cake, mixing the phosphorus salt solution B with an oxidant to obtain a mixed solution C, washing the phosphorus salt filter cake, and recycling generated washing water as dilution water of the raffinate acid; 3) Carrying out a synthesis reaction on the mixed solution C and the ferrous sulfate solution A, and filtering the obtained slurry to obtain a synthesized filter cake and a first-stage mother solution; 4) Mixing the synthesized filter cake with water for size mixing, adding phosphoric acid into the mixture for temperature rising and aging, filtering the aged slurry to obtain an aged filter cake and secondary mother liquor, and performing secondary washing, drying, calcining and crushing on the aged filter cake to obtain battery-grade ferric phosphate; The primary washing water generated by washing the synthesized filter cake and the secondary washing water generated by washing the aged filter cake are recycled in a grading way according to