Patent ID: 7910080

Claim:
A phosphorous pentoxide producing method comprising: forming a kiln bed using feed agglomerates in a counter-current rotary kiln, the bed having a length; the agglomerates containing phosphate ore particles, carbonaceous material particles, and sufficient silica particles for the agglomerates to exhibit a calcium-to-silica mole ratio of from 0.5 to 1.0; maintaining a bed temperature at or above 1260° C. along a portion of the bed length without exceeding 1380° C. along the entire bed length; and generating kiln off gas from the portion of the bed at or above 1260° C. and collecting phosphorous pentoxide from the kiln off gas, the kiln discharging a residue containing processed agglomerates, less than 10% of the agglomerates' phosphate input to the kiln remaining in the residue as phosphate.