1921. ------. [KOPPERS, H.] (Heinrich Koppers G. m. b. H.). [Removing Dust From Gases.] German Patent 677,222, June 21, 1939 (Cl. 26 d-1.20). Chem. Abs., vol. 33, 1939, p. 6663.

Tar-free gases containing dust, which tends to form hard cementitious deposits, are washed in a centrifugal washing apparatus fed with H₂O containing an inert solid, such as sandy clay, in suspension. The formation of deposits on the surfaces of the washer is thus restrained. The process may be applied to CO-H₂ mixtures obtained from brown coal or coke.