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CHEMISTRY AND CHEMICAL ENGINEERING

CHEMISTRY AND CHEMICAL ENGINEERING

Abstract

The aim of the research was to study the effect of temperature, the ratio of P2O5EPA:P2O5PRM and the duration of calcination on the content of various forms of P2O5 in calcium polyphosphate. The effect of calcination temperature from 150 to 300 °C, the ratio of P2O5EPA:P2O5FRM from 2,15 to 4,50 and the duration of the process from 20 to 120 minutes on the changes in various forms of P2O5 were studied. It was shown that with increasing temperature to 200-250 °C the content of the total (ortho + poly) assimilable form of Р2О5 increases and then decreases, passing through a maximum. The content of assimilable orthophosphates with an increase in the calcination temperature first sharply decreases to a temperature of 200 °C, and then more smoothly changes at temperatures from 200 °C to 300 °C. The content of assimilable polyforms P2O5 is increased independently of the ratio of P2O5EPA: P2O5PRM to a temperature of 200 °C. With a further increase in temperature in calcium polyphosphate with a ratio of P2O5EPA:P2O5PRM equaled to 2,15, the content of the P2O5 poly decreases by 5%, and at higher ratios P2O5EPA:P2O5PRM increases by 5-10% compared to a temperature of 200 °C. Upon reaching a temperature of 300 °C, the content of the P2O5 polyforms decreases on average by 10-20%, independently of the ratio of P2O5EPA:P2O5PRM. With an increase in the calcination duration from 20 to 40 minutes at temperatures of 200 and 240 °C, the content of the total assimilable form of P2O5 significantly increases. A further increase in the duration of calcination does not lead to a significant increase in the assimilable form of P2O5 as at a temperature of 260 °C. The content of the water-soluble form of P2O5 varies from 6,80-17,52% to 24,30-43,43%, regardless of the temperature and duration of calcination of 20-120 minutes.

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