Method to improve acidulation quality of North Carolina phosphate rock

摘要

Phosphate rock is heated under controlled conditions to essentially eliminate organic impurities and sulfides from the rock and subsequently leached with water to substantially increase the porosity and surface area of the calcined solid and remove any traces of sulfide still remaining in the calcine. This process yields an improved calcined product rendered more suitable for acidulation to wet-process phosphoric acid and is beneficial for apatitic phosphate rocks possessing a moderate to high content of organic impurities and a high degree of carbonate substitution in the apatite crystal lattice.