BHS examines the cake structure and process parameters to determine the optimum technology. The major difference between the two technologies depends on the cake structure that is formed. Some cakes are better handled in the horizontal and some in the vertical.

Cake Thickness and Filtration: The candle filter is limited to cake structures that can be formed to about 5 – 20 mm. The pressure plate filter can handle cakes up to 75 mm. Both units can conduct filtration up to 150 psig.

Filter Media: The candle filter uses only synthetic media with a clean removal efficiency from 1 –3 micron range and finer down to 0.5 microns. The pressure plate filter can also use metal media. For the pressure plate filter, the clean micron range removal efficiency is also 1 – 3 microns and finer.

Cake Washing: If the process requires washing to remove the API from the solids, then generally the pressure plate filter is a better alternative. If washing is not as critical, then the candle filter may be the optimum technology for clarification and recovery.

Heel Filtration: The remaining liquid in the vessel (liquid heel) after filtration or washing can be removed from the candle filter or pressure plate filter by circulation, heel filter in the cone of the vessel, or additional heel filter plates in the pressure plate filter.

Cake Drying: The candle filter can produce cakes with approximately 10% moisture. This moisture level depends upon the specific cake but the moisture lower limit is that moisture just above the cake cracking point. The pressure plate filter can produce bone dry cakes.

Cake Discharge: Both designs can easily discharge most cakes equally with no residual heel.

Clean-In-Place (CIP)/ Steam-In-Place (SIP): Both units conduct CIP / SIP operations in identical manners by filling and circulating cleaning fluids while blowing gas in the reverse direction to the filtration direction, which crates a turbulent mixture or a quasi-ultrasonic cleaning effect. The pressure plate filter further enhances this operation with plate vibration.