Evaluation of thermally promoted reaction products of some selected phosphate rocks from India

Phosphate rocks (PRs) from Jordan and others from Kasipatnam (Andhra Pradesh), Purulia (West Bengal) and Mussoorie (Uttar Pradesh) (all from India) were heated either alone or with Na2CO3 or KCl at 300, 500, 700 and 900°C in the weight ratio of 1:0.5, 1:0.25 and 1:0.15. The utilisation of KCl in the PR-KCl mixture was very low. The products obtained by heating PR-KCl mixtures of different weight ratios at different temperatures (300–900°C) contained much lower amount of available P compared to those of PR-Na2CO3 mixtures. The waterand citrate-soluble P content of these products decreased with a change in the PR:Na2CO3 ratio from 1:0.5 to 1:0.15. The amount of Na2CO3 in the 1:0.25 and 1:0.15 ratio of the PR additive mixture was found to be insufficient to complete the reactions. About 72–98.6% of the total P content of the product obtained by heating PR-Na2CO3 mixture in the 1:0.5 ratio at 900°C was in the available form. The inherent accessory minerals present in the PRs might have taken part in the thermally promoted reactions of PR-Na2CO3 mixture resulting in a product which has got most of its P in the available form. The contribution from the accessory minerals present in the Jordan PR was not sufficient to meet the requirement of the reactions which resulted in lower amount of available P in the product.