Method for recycling phosphorus and fluorine in defluorination residues

Abstract

The invention discloses a method for recycling phosphorus and fluorine in defluorination residues. The method comprises the following steps of: returning sulfuric acid and a certain amount of phosphoric acid to decompose the defluorination residues, extracting the phosphorus and the fluorine in the defluorination residues to generate bi-water or semi-water calcium sulfate crystals and a dilute phosphoric acid solution, performing solid-liquid separation, and thus obtaining dilute phosphoric acid and a byproduct, namely ardealite; concentrating the dilute phosphoric acid to obtain concentratedphosphoric acid, recycling overflow fluorine-containing gas in the phosphoric acid concentrating process and the acid preparing process to obtain fluorides such as fluosilicic acid and the like, or adding a defluorination agent into the dilute phosphoric acid, and recycling fluorine resources in a mode of the fluorides such as sodium fluosilicate and the like; and processing the obtained concentrated phosphoric acid by the conventional method, and thus obtaining phosphate products such as ammonium phosphate and the like. By the method, phosphorus and fluorine resources in the defluorination residues can be effectively recycled, wastes are made profitable, and the recycling value of the phosphorus and the fluorine in the defluorination residues is improved.

Description

technical field [0001] The invention relates to sewage treatment, in particular to a method for recovering phosphorus and fluorine in defluorination slag. Background technique [0002] At present, the defluorination press filter process is usually used in my country to prepare feed grade calcium hydrogen phosphate. The large amount of waste residue produced in the defluorination section is called defluorination residue (also known as "white fertilizer"), and the defluorination residue is a cement-like mass. , rich in phosphorus and fluorine resources, the dry basis of the defluorination slag generally contains 15% to 30% of P 2 o 5 and 5% to 15% of F. At present, the recycling of defluorinated slag is to dry it and use it as raw material of rough manure or compound fertilizer. However, due to the P contained in the defluorination slag 2 o 5 citrate soluble P 2 o 5 , when used to produce compound fertilizers, the water-soluble P content required in GB15063-2009 cannot...

AI Technical Summary

Problems solved by technology

When the defluorinated slag is directly used as coarse fertilizer and applied to crops, it may cause poisoning of crops due to its rich F

Therefore, the defluoridation slag can neither be directly put into the market as a commercial fertilizer, but also limited as a raw material for compound fertilizer

[0003] In the patent literature with the application number 97107676, a kind of "method for producing ammonium phosphate fertilizer by using wet phosphate waste residue" is disclosed, the method includes passing through wet phosphoric acid After reacting with defluorination slag, react with liquid ammonia or ammonium bicarbonate, and finally dry the slurry to obtain modified ammonium phosphate fertilizer. This method needs to add wet-process phosphoric acid, which increases the cost, and does not recycle the rich defluorination slag. fluorine, so that a large amount of fluorine resources in the defluorination slag wasted

At present, there are almost no recycling methods for the fluorine resources in the defluorination slag in my country.

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