The filter media is indexed by pneumatic cylinders located on the exterior of the unit. The pneumatic operation and fixed trays eliminates a motor and variable speed drive, there are no rails/rollers, no rubber carrier belt and flexible pressure-vacuum rated hoses are not required. For cloth movement, the vacuum is broken by butterfly valves and the cloth moves (indexes), by pneumatic cylinders, in the space above the vacuum trays. The belt moves along but never touches the trays, which allows for long filter cloth life.
The vacuum trays, are fixed in place, and divided into zones. Each tray has a filtrate outlet, which allows for the filtrates to be collected individually. Supporting grids with large open sections are provided in the vacuum trays to support the belt.
Each individual zone in the vacuum tray is connected to the filtrate manifold. The filtrate manifold is divided by butterfly valves according to the process. These valves rapidly open for vacuum and the close to break the vacuum belt advances.
The continuous, circulating filter cloth belt is indexed by pneumatic cylinders and rollers. When the belt is stopped, vacuum is applied to the trays, for filtration, caske washing and drying. For cloth movement, the vacuum is broken by butterfly valves and the cloth moves (indexes), by pneumatic cylinders, in the space above the vacuum trays. The belt moves along but never touches the trays, which allows for long filter cloth life.
The suspension is delivered from a stationary feed device designed to prevent solids plugging. An oscillating feed device can be provided for fast settling suspensions.
Washing can be by spray nozzles or overflow channels. The washing can be co-current or counter-current.
The initial portion of the cake is removed during forward feed, the remainder when the extraction roller travels back. A scraper removes residual cake from the cloth.
A pressing plate is pneumatically pressed onto the cake when the belt is stopped. Compressed gas or hot gas cake can be blown through the cake for additional drying.
Following filtration and washing, it is possible to apply a variety of drying techniques such as vacuum, pressing, blowing/convection as well as a combination of techniques. The trays can be heated for further drying.
Criteria / demands
The BHS vacuum belt filter can be used to for applications such as the following:
- Filtration, Cake Washing and Drying
- Enclosed gastight production
- Fully automatic operation
- Temperature up to 95°C and higher depending upon the materials of construction
- Dewatering by mechanical expression up to 6 bar
- Filter cake drying
To meet customer specifications, various types of enclosed filters are available:
- Dust Hood
- Closed hood over the entire filter
- Closed box
- Gas and pressure-tight
- Pharmaceutical design