Процесс Vrm Raw Mill . Dipl.-Ing. Th. Fahrland, Dr.-Ing. K.-H. Zysk, Loesche . that of a vertical roller mill (VRM) carrying out the same oper - ations by a factor of between 1.5 and 2, depending on the degree of optimisation of the ball mill. Fig. 1 illustrates this connexion, as well as showing the increasing energy bene-fit that can be obtained with a vertical roller mill as the spe ...