PROCESS FOR SEPARATING HYDROGEN FLUORIDE FROM EXHAUST GASES FORMED IN AN ELECTROLYTIC PROCESS FOR THE PRODUCTION OF ALUMINUM

摘要

This invention is concerned with a process for separating hydrogen fluoride from exhaust gases containing same and formed in an electrolytic process for the production of aluminum, by dry absorption of alumina with complete separation of the solid impurities contained in said gases, wherein said exhaust gases are introduced as fluidizing gas into a fluidized-bed reactor containing alumina at such a velocity that the gas and solids form an expanded fluidized bed in which the solids concentration decreases from bottom to top, a major portion of the solids is upwardly discharged together with the gas and the solids discharged are separated in an immediately succeeding electrostatic precipitator. The process according to the present invention is characterized in that the solid impurities which are contained in the exhaust gases are first separated in an additional electrostatic precipitator before the gases are introduced into the fluidized-bed reactor. This results in a preliminary separation of deleterious impurities to a high degree so that the fluorine-laden alumina used for dry absorption can be returned to the electrolytic process without the introduction of any such impurities.