Process for drying cakes of filtracao constituted in the chambers of filtracao of a filter press filter press as well as a process for the preparation of

摘要

To dry accumulated filter cakes in the filter chamber (4) of a filter press, the cakes are heated only at the side away from the membrane (6). The temperature is set according to the boiling point of the retained liquid under vacuum, so that a vapor layer is formed to penetrate through the filter cake and press the retained liquid against the drainage surface of the unheated membrane (6). The heat is distributed evenly over the filter cake surface so that the transit zone between the vapor and liquid phases is even and homogenous through the filter cake, without local vapor break-through points. The vacuum is applied during the final press phase, to accelerate the drainage action, and the heating of the filter cake surface starts during the final press phase. Heating elements are directly at the filter cake surfaces. During drying under final press pressure, the filter cakes lie against the membrane (6), using a final pressure which is higher than the vapor pressure of the retained fluid in the cake. The pressure medium for the membrane can be cooled or heated to set raised temp. differences or to match process requirements within a restricted range. Vacuum is applied at the filter outlet or the inlet for the clouded liquid for filtering. An Independent claim is included for a filter press with a heating element directly between two filter membrane units (1). The filter surface has filter openings for the filtrate, evenly distributed over it. Preferred Features: The filtrate outflow channels, at the corner of the membrane filter unit (1), has a preferably triangular cross section to improve the flow. The plate frame (3) has a vacuum-tight edge seal, with an inner integrated filter cake clamp. The heater is of a material with high thermal conductivity, and preferably metal. The side of the heater towards the filter membrane unit (1) is flat or part of the filter cake, without drainage surfaces. The heater is in one or more parts, held together by an adhesive or welding or with additional seals. The heater has heating channels which are round and/or oval and/or rectangular, in a serpentine layout. The heaters have a thermal insulation at the edges of the frame. The heaters have electrical heating conductors.