Abstract: A phosphorous pentoxide producing method includes forming pre-feed agglomerates containing phosphate ore particles, carbonaceous material particles, and silica particles and heating the pre-feed agglomerates in a reducing or inert atmosphere to an induration temperature from above 900 C to less than 1180 C and maintaining the induration temperature for 15 minutes or more. The method includes forming feed agglomerates and increasing a compression strength of the feed agglomerates to above 25 lbf using the heating, the feed agglomerates exhibiting a calcium-to-silica mole ratio less than 1 and a silica-to-(calcium+magnesium) mole ratio greater than 2. A reducing kiln bed is formed using the feed agglomerates, kiln off-gas is generated, and phosphorous pentoxide is collected from the kiln off gas.

Abstract: A phosphorous pentoxide producing method includes forming a reducing kiln bed using feed agglomerates containing a lignin sulfonate both inside the agglomerates and coating a surface of individual agglomerates. Freeboard particulates are generated from the agglomerates, an amount of particulates generated being less than would occur in the method with no lignin sulfonate. Kiln off gas is generated and phosphorous pentoxide is collected from the kiln off gas. The kiln discharges a residue containing processed agglomerates, less than 20% of the agglomerates' phosphate input to the kiln remaining in the residue. The percentage of input phosphate that remains in the residue is less than would occur in the method with no lignin sulfonate. The method may include forming green agglomerates. Controlling a drying rate of the green agglomerates may wick some of the lignin sulfonate onto the surface of individual drying agglomerates without adhering the agglomerates together.

Abstract: A phosphorous pentoxide producing method includes forming a kiln bed using feed agglomerates with a calcium-to-silica mole ratio of from 0.5 to 1.0 and 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. Less than 10% of the agglomerates' phosphate input to the kiln remains in the kiln residue as phosphate. Another method includes maintaining a bed temperature at or above 1180° C. along a portion of the bed length and establishing a bed surface-to-volume ratio multiplied by a time for bed heat up to 1180° C. of less than 50 minutes-ft2/ft3.