The new Standard VDI 2762, Part 3 for filter cake deliquoring by gas pressure had been published for the first time in March 2017. This standard describes a measurement procedure to determine the deliquoring kinetics and equilibrium of filter cakes by gas pressure difference. It provides the basis for quantitative statements about the mechanical deliquorability of largely incompressible filter cakes by means of gas differential pressure and is relevant for vacuum as well as for gas overpressure filters, like nutsch filters, candle and leaf filters, drum, disc, belt or pan filters. It is a continuation of Standard VDI 2762, Part 2, which describes the formation of incompressible filter cakes from a suspension. The maximum gas pressure difference is limited to approximately 0.6Mpa for the typical range of technical applications. The measurement procedure provides data for the selection of separation apparatuses, filter design and scale up or diagnostic inspection. To get relevant and well defined data, several details of the filtration and deliquoring experiments must be followed carefully and will be discussed exemplarly. The method comes to its limits, if filter cakes become more and more compressible. In these cases parallel to the cake desaturation a consolidation of the particle structure takes place and the filter cake shrinks. In the worst case shrinkage cracks are occurring and the process failes due to high gas flow through the cake, overload of the gas compressor and following decrease of filtration pressure. In any case a change of the pore structure in the filter cake takes place during shrinkage, which influences the capillary pressure distribution and thus the desaturation. This interplay of consolidation and desaturation will be discussed in connection with the determination of practically applicable capillary pressure distributions, which are orientated on the prospective technical process...
Session: L6 - Cake Filtration – Two- and Multi-Component Slurries
Day: 14 March 2018
Time: 10:45 - 12:00 h