Rotary Vacuum Drum Filter Basics

Rotary Vacuum Drum Filters process slurry and discharge cake in a continuous process. RVDFs can be used in waste water treatment, sludge dewatering, chemical manufacturing, the pharmaceutical industry, cosmetics, mineral mining and refining, and the food processing industry. It is ideal for a slurry with variable cake thickness, moisture content, and stickiness.

Slurry sits in a tank with a partially submerged drum. As the drum rotates into slurry, vacuum pulls the liquor through the industrial filter media, trapping the solid particles on its surface, forming a cake. As the drum continues to travel through slurry, the cake thickens.

As the drum emerges from the slurry tank, spray bars wash the cake, allowing air, water, and the remaining liquor to travel through the drum section into piping, through the valve, and into a vacuum receiver.

As the rotary vacuum drum filter begins to rotate facing the ceiling, it enters the drying zone. The drum remains under vacuum, pulling air through the cake for more dewatering.

The drum then reaches its discharge zone as it roll to the position just over the slurry tank. Drum filters discharge in a variety of ways; scraper discharge, belt discharge, string discharge, roll discharge, and pre-coat discharge.

Pre-coat discharge is used if slimy, sticky, oily, or blinding solids are present. Cloth covers the drum, then around four inches of diatomaceous earth, perlite, cellulose, carbon, or some combination form the ideal filter cake. Next, the cloth runs through the slurry, picks up and dries the problem solid. Next, a scraper blade removes the solid along with a thin layer of the pre-coat. This pre-coat removal gives every cycle the ideal filter cake to pass through.

The drum completes its rotation in a no vacuum zone prior to reentry into the slurry. This dead zone is necessary to maintain vacuum across the surface of the rotary vacuum drum filter. While we just went through one panel’s rotation, the rest of the drum continued its own function. There is always a section of drum going through each step of the process.