Polyphosphoric acid production

摘要

Polyphosphoric acids for fertilisers, technical salts and synthesis, free from orthophosphoric acid are produced by combustion of phosphorus in a current of air of velocity 60-120 m/s., treatment of the ensuing gases, cooled to 850-1000 degrees with polyphosphoric acids of 100-170 degrees, contng. 84-89% P2O5 and separation of the final product. In an example, the gases resulting from the treatment of 100 kg./hr. of phosphorus with a 450 m3./hr. of air (velocity 70 m./s) are cooled to 950 degrees and passed first through a tower cooled by circulating polyphosphoric acid of 140 degrees and contng. 85% P2O5, then through an electrostatic precipitator. The issuing acid contng. 72% P2O5 is mixed with the polyphosphoric acid giving a final product contng. 85% P2O5.