| abstract |
A method of filtering a sludge, which consists of solid material and a liquid phase. In the method, the sludge is fed to a filtering unit, such as a suction filter, with which the solid material is separated from the liquid. According to the present invention, the sludge is treated with foam in association with the filtering, for example by mixing a pre-prepared foam into the sludge or by spreading a foam layer onto the surface of the filtrate cake. By the present invention, it is possible to increase the filtering capacity and to reduce the residual moisture of the filtrate cake and the moisture variations in the filtrate cake. It is also possible to leave out thermal drying which is used to achieve the desired residual moisture. In addition, the amount of dissolved and colloidal substance in the filtrate is reduced. |