Abstract: In a continuous process for reacting particulate ore with a liquid reagent in a counter-current vertical column the improvement comprising:(a) providing an upper and lower chamber for the vertical column;(b) maintaining sufficient upward flow of liquid reagent in The upper chamber so that the particulate ore is wetted and deaerated, at least some fine particles thereof are carried overhead for removal, and the remainder thereof settle and enter the lower chamber; and(c) maintaining sufficient fluidization and retention time in the lower chamber so that the desired amount of reaction with the ore takes place, at least some of the fine ore particles which are generated from the reaction process and/or which are introduced with the particulate ore are entrained and carried upward for removal, and the reacted particulate ore exits the lower chamber.

Abstract: A dimeric cyclic ester of an alpha-hydroxycarboxylic acid (lactide) is separated and recovered from a vapor product stream containing the cyclic ester, the corresponding lower-boiling hydroxycarboxylic acid (lactic), higher-boiling oligomeric hydroxycarboxylic acid and water without the use of solvents. More specifically, the vapor stream is condensed to obtain a condensate containing substantially all the cyclic ester, and the condensate is refined by distillation means alone to recover the cyclic ester substantially free of water, the alpha-hydroxycarboxylic acid and the higher-boiling oligomers.

Abstract: A distillation process for converting lactic acid oligomer to lactide wherein the oligomer is depolymerized in the presence of a co-vaporizable solvent at a temperature and pressure which forms a vapor fraction comprising water, lactide, lactic acid and solvent, and the vapor fraction is condensed and the lactide is recovered from the condensate.