Rotary Drum

Rotating drums are important components used in various industrial processes for mixing, segregating, drying or coating of particles.

?How does it work

  1. As the drum rotates, it is partially submerged in the feed slurry.
  2. Vacuum draws liquid through the filter medium (cloth) on the drum surface which retains the solids.
  3. The vacuum pulls air (or gas) through the cake and continues to remove moisture as the drum rotates.

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.

A Rotary Vacuum Filter Drum consists of a cylindrical filter membrane that is partly sub-merged in a slurry to be filtered. The inside of the drum is held lower than the ambient pressure. As the drum rotates through the slurry, the liquid is sucked through the membrane, leaving solids to cake on the membrane surface while the drum is submerged. A knife or blade is positioned to scrape the product from the surface.

The technique is well suited to slurries, flocculated suspensions, and liquids with a high solid content, which could clog other forms of filter. It is common to pre-coat with a filter aid, typically of diatomaceous earth (DE) or Perlite. In some implementations, the knife also cuts off a small portion of the filter media to reveal a fresh media surface that will enter the liquid as the drum rotates. Such systems advance the knife automatically as the surface is removed.

Advantages

-The rotary vacuum drum filter is a continuous and automatic operation, so the operating cost is low.

-The variation of the drum speed rotating can be used to control the cake thickness.

-The process can be easily modified (pre-coating filter process).

-Can produce relatively clean product by adding a showering device.

Disadvantages

– Due to the structure, the pressure difference is theoretically limited to atmospheric pressure (1 bar), and in practice somewhat lower.

– Besides the drum, other accessories, for example, agitators and vacuum pump, vacuum receivers, slurry pumps are required.

– The discharge cake contains residual moisture.

– The cake tends to crack due to their air drawn through by the vacuum system, so that washing and drying are not efficient.

– High energy consumption by the vacuum pump.

MATERIALS OF CONSTRUCTION

Available materials of construction for rotary drums include:

– Carbon Steel

– Stainless Steel

– Specialty Alloys

– Explosion-Bonded

– Abrasion-Resistant Steel

– Cladded Steel