Method for recycling phosphorus and fluoride in sewage residue of phosphorus fertilizer plant

Abstract

The invention discloses a method for recycling phosphorus and fluoride in the sewage residue of a phosphorus fertilizer plant. According to the method, the sewage residue is decomposed by using sulfuric acid, the phosphorus and the fluoride in the sewage residue are extracted, calcium sulfate dihydrate crystal or calcium sulfate hemihydrate crystal and diluted phosphoric acid solution are generated, diluted phosphoric acid and phosphogypsum which is the by-product are obtained through solid-liquid separation, the diluted phosphoric acid is concentrated into concentrated phosphoric acid, the escaped fluorine containing gas is recycled in the process of concentrating the phosphoric acid and making acid and produced into the fluoride such as the fluosilicic acid and the like, or defluorination agent is added into the diluted phosphoric acid to recycle fluoride resources in the form of the fluoride such as the sodium fluosilicate and the like, and the obtained concentrated phosphoric acid can be used to prepare other phosphate products such as the ammonium phosphate and the like by using the traditional method. The method can be used to effectively recycle the phosphorus and fluoride resources in the sewage residue of the phosphorus fertilizer plant so that the waste materials can be changed into the valuable materials and the recycling value of the phosphorus and fluoride resources in the sewage residue of the phosphorus fertilizer plant can be improved. The method has good economic benefit and environment protection significance.

Description

technical field [0001] The invention relates to sewage treatment, in particular to a method for recovering phosphorus and fluorine in the sewage residue of a phosphate fertilizer plant. Background technique [0002] Phosphorus and fluorine are important mineral resources in short supply in my country, and play an important role in the national economy. The production sewage of my country's phosphate fertilizer plants generally contains relatively high concentrations of phosphorus and fluorine. The sewage residue of the phosphate fertilizer plant is a large-tonnage waste separated from the filtration and separation equipment after the phosphorus and fluorine-containing sewage undergoes a water treatment process. The sewage residue is rich in Phosphorus and fluoride resources are urgently needed to be recycled to realize turning waste into treasure. Taking a state-owned phosphate fertilizer factory as an example, about 90,000 tons of sewage residue (water content is about 50%...

AI Technical Summary

Problems solved by technology

Domestic phosphate fertilizer plants used to dry this kind of sewage residue as the raw material of crude fertilizer or compound fertilizer, but because most of the P2O5 contained in the sewage residue It is citrus soluble P2O5, which cannot reach the water-soluble P2O required in GB15063-2009 when used in the production of compound fertilizers 5 should not be lower than the requirement of 40% of the effective P2O5 content, so this kind of sewage residue is generally used as waste in domestic phosphate fertilizer plants Stockpiling, the phosphorus and fluorine in it have not been recycled, so that the phosphorus and fluorine resources are wasted, and high storage maintenance costs are required, land resources are occupied, and the surrounding environment is polluted

[0003] After retrieval, Chinese Patent No. 201010169236.X "Using Struvite Precipitation Method to Recover Phosphorus from Wastewater and Process Method" and No. 200480014765.5 "A Recycling Phosphorus "methods" have provided methods for recovering phosphorus, but there is no technical solution involving the simultaneous recovery of phosphorus and fluorine in sewage residues

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