New technique for producing disodium phosphate

Abstract

A process for preparing sodium tripolyphosphate includes adding waste phosphoric acid to neutralizing reactor, steam heating while adding sodium carbonate under stirring until 82 deg.C and pH=8+ / -1, adding liquid sodium hydroxide until 90 deg.C and pH=12+ / -1, stirring for 5-20 min, depositing, transferring it to another neutralizing reactor, adding waste sodium carbonate, adding phosphoric acid and sodium hydroxide while regulating K=3.0+ / -0.1, adding ammonium nitrate, filtering and dewatering polymerization.

Description

technical field [0001] The invention relates to a process for producing sodium tripolyphosphate. Background technique [0002] The main raw material and specification that prior art produces sodium tripolyphosphate use are phosphoric acid (H 3 PO 4 ≥85%) and soda ash (Na 2 CO 3 ≥98%), the reaction principle is neutralization of phosphoric acid and soda ash to generate disodium hydrogen phosphate and sodium dihydrogen phosphate, the chemical reaction formula is [0003] <chemistry num="001"> <chem file="200310105368_cml001.xml" / > < / chemistry> [0004] Gained sodium phosphate is dried and polymerized to generate pentasodium phosphate, and the chemical reaction formula is [0005] <chemistry num="002"> <chem file="200310105368_cml002.xml" / > < / chemistry> [0006] The production process usually adopts the converter one-step method: first add about 1,200 kg of clear water to the neutralization kettle, and then pass in steam. When t...

AI Technical Summary

Problems solved by technology

The disadvantage is that the raw materials used are all ≥85% phosphoric acid and ≥98% soda ash. For every ton of sodium tripolyphosphate produced, the unit cost of raw materials is about 3300 yuan / ton, which is high.

In addition, a large amount of waste phosphoric acid and waste soda ash produced in industrial production pose serious pollution hazards to the surrounding environment

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