Q1: The controlling resistance in a rotary drum vacuum filter is the __________ resistance.

ANS:B - cake

In a rotary drum vacuum filter, the controlling resistance is typically the cake resistance.

Explanation:

• Rotary Drum Vacuum Filter: This type of filter consists of a rotating drum covered with a filter medium. The drum is partially submerged in the slurry to be filtered. Vacuum is applied inside the drum, which draws the filtrate through the filter medium, leaving behind a filter cake on the drum surface.
• Controlling Resistance:
  • Cake Resistance: The filter cake that forms on the surface of the drum is often the main resistance to filtration. This is because as the cake thickness increases, it restricts the flow of filtrate through the filter medium. The resistance offered by the cake depends on factors such as its thickness, porosity, and compressibility.
  • Filter Medium Resistance: While the filter medium (cloth or mesh) also offers resistance to flow, its impact is usually less significant compared to the cake resistance.
  • Piping Resistance: Refers to the resistance encountered in the piping system leading to and from the filter. This resistance is typically low compared to the cake and filter medium resistances.
• Significance:
  • To optimize the filtration process in a rotary drum vacuum filter, efforts are often focused on managing the characteristics of the filter cake, such as thickness and porosity, to minimize resistance and maximize filtration efficiency.
  • The filter medium is designed to provide adequate support and filtration capability but is secondary to the cake in terms of resistance.