Abstract: In a kraft pulp mill, a process and apparatus for removing and washing dregs from green liquor so that the pH of the dregs is below "hazardous waste" levels. Specifically, green liquor clarifier underflow is filtered using a simple non-precoat cassette filter to form a first dregs cake. The dregs cake is diluted, preferably with water. The diluted dregs cake is then filtered in a precoat dregs filter to produce a dregs cake that is at least 50% solid and has a pH of about 12.0 or less.

Abstract: A method for treating the fine-grained spend absorbent (primarily calcium sulfite and calcium sulfate) from a dry flue gas desulfurization process. The absorbent, having a small amount of binder therein, is oxidized in a fluidized bed reactor at a temperature in the range from about 700.degree. C. to about 1000.degree. C. to produce a dry essentially fully oxidized pelletized calcium sulfate product.Calcium sulfate pellets having an average diameter of from about 0.5 mm to 5 mm and containing from about 1% to about 3%, by weight, of binder constituents, are composed of agglomerated calcium sulfate particles having an average diameter of from about 50.mu. to about 100.mu. bound to each other by the binder constituents.

Abstract: Phosphate rock is calcined under conditions calculated to completely oxidize the carbon and sulfur in the rock. Calcination is also conducted at elevated temperature to eliminate cadmium metal, a poisonous substance in fertilizers, from the calcined rock product. A fluid bed system for eliminating cadmium metal in the calcination of phosphate rock involves a two-vessel system in which an independent cadmium removal vessel served by a separate fluidizing air stream carries out volatilization of cadmium, while preheating, precalcining and cooling is conducted in another multi-bed reactor which is served by a separate fluidizing air stream.

Abstract: A method for dehydrating alunite ore prior to further processing to recover metals therefrom, comprising exposing the ore in particulate form to burning coal as the heat supply in a fluidized bed fluidized with an oxygen containing gas. The invention is illustrated by the removal of water from alunite ore prior to further processing the ore to recover aluminum.