Gas consumption, solids throughput and residual cake moisture - relation between operating expenses and process results fo rotary filters

During the operation of continuously operating rotary vacuum and pressure filters a gas flow arises through the partially deliquored filter cake. This gas flow is determining significantly the energy demand of the process and thus the operating expenses. To maintain the filtration pressure for cake formation and deliquoring the gas flow must be exhausted in the case of vacuum filtration and be delivered in the case of pressure filtration by the compressor into the filter housing. The necessary expenses in form of gas consumption are corresponding with the process results in form of solids throughput and residual cake. One question to be answered is, whether a certain cake moisture can be achieved most energy efficient with regard to the ratio of demanded gas consumption per unit solids produktion. As variable parameters the relation of cake formation and cake deliquoring angle in the filters control head, the rotation speed of the filter, the gas pressure difference and the slurry concentration had been selected for this investigation. For the formation of approximately incompressible filter cakes, their desaturation and the parallel arising gas flow physically based model equations are known, which contain the relevant influencing parameters. ... mehrThese can be transferred to the operational conditions of a rotary filter. Thus the correlations between energy demand, operational parameters and process results could be estimated and compared with the results of a broadly layed out experimental parameter study. This study was based on discontinuous laboratory filter experiments with a zincsulfide slurry from the mineral processing. From the results could be concluded, that for rotary filters the ratio of gas consumption per produced solids mass is depending mainly on the residual moisture content of the filter cake. The parameter combination to achieve a certain moisture content seems to be not relevant. As a final consequence the parameter combination for a desired moisture content should be set for maximal solids production. This leads for a given slurry feed flow and constant energy demand to the smallest necessary filter area and thus the optimal solution for the given separation task.