Rotary drum vacuum filter — vacuum application zones:\nIn a general continuous rotary drum vacuum filter, vacuum is applied in which zone(s)?

Introduction / Context:
Continuous rotary drum vacuum filters divide a rotation into arcs for cake formation (filtration), washing, and dewatering/drying. The vacuum system is valved to apply suction to the sectors passing through these zones. Understanding which arcs are under vacuum is essential for troubleshooting throughput, wash efficiency, and cake dryness.

Given Data / Assumptions:

• Standard drum filter with filtrate receiver and valved sectors.
• Three functional arcs: filtration, wash, and drying prior to discharge.

Concept / Approach:
Vacuum is fundamental in all three arcs: it draws slurry liquor through the medium to form cake (filtration), pulls wash liquor through the cake to displace mother liquor (washing), and continues to remove liquid by suction and evaporation assistance (drying). Only the cake discharge zone is valved off vacuum to allow gas blowback or mechanical discharge. Hence the correct answer is that vacuum is applied in filtering, washing, and drying zones.

Step-by-Step Solution:

Verification / Alternative check:
Piping and instrumentation diagrams show rotary valve ports connected to vacuum headers across the filtration, wash, and dewatering sectors.

Why Other Options Are Wrong:

• Limiting vacuum to a single zone neglects essential wash and drying operations.
• “None” contradicts the operating principle of vacuum filtration.

Common Pitfalls:
Assuming drying is purely evaporative; in drum filters it is largely vacuum-assisted drainage.

Final Answer:
All of the above: filtering, washing, and drying zones