Many times we encounter an “if it ain’t broke don’t fix it,” mentality. Process engineers in particular run up against this constantly. Yet, when it comes to palladium recovery, we’ve seen some strong results from taking an inventive approach to the filtration technologies uses. Currently, in recovering palladium catalysts the slurries are clarified with the use of filter presses, manual plate or nutsche filters, bag filters, or cartridge filters.
All of these require manual operations for cake discharge and cleaning between batches or campaigns. Other drawback include:
- high labor and maintenance costs
- high disposal costs
- exposure of the operators to toxic and hazardous solvents and solids
- environmental impact of used and contaminated filter cloth, bag filters and filter cartridges.
A new approach developed by BHS uses Pressure Plate Filters, which are batch-operated, pressure-filtration systems. Here’s what’s involved.
Pressure Plate Filtration Systems
Pressure plate filters are comprised of filter plates, contained within a pressure vessel. The vessel contains the circular horizontal filter plates in a plate stack. The slightly sloped plates are conical-shaped metal that support a coarse-mesh backing screen covered with filter cloth. An opening in the center of the plate allows the filtrate to travel between plates and out of the vessel.
The slurry enters the bottom of the vessel and is pumped upward. The solids build up between the plates, while the liquid flows through the core of the filter plates and exits from the top of the vessel. The cake is then washed and dried. Two unbalance motors vibrate the filter plates to dislodge the cake from the filter cloth so it can be discharged.
Pressure plate filters are used for filtration of cakes greater than 20 mm thick. They are selected for cakes that are stable horizontally because of the orientation of the plates.
Palladium Catalyst Filtration, Washing and Drying
There are many choices of technologies, but we’ve found pressure plate filters provide higher quality filtration. In one application, manual filter presses were used to recover and reuse the palladium catalyst. The filter presses exposed the operators to the process and had inefficient washing and drying. The process had a very short cycle of 4 hours per batch.
However, when the BHS pressure plate filter technology was implemented, the filtration, two-step cake washing, nitrogen blow drying and cake discharge were all completed in less than 4 hours with full containment. Read the full article to learn more.