Rotary drum vacuum filter — effect of drum speed on filtration rate\nAs the rotational speed of a continuous rotary drum vacuum filter increases (within normal operating limits), how does the filtration rate generally respond?

Introduction / Context:
Rotary drum vacuum filters carry the filter medium through zones of cake formation, washing, drying, and discharge. Drum speed determines the residence time in each zone and the frequency with which new cake is formed, thus influencing the overall filtration rate (throughput per unit area).

Given Data / Assumptions:

• Operation within practical limits (not so fast that cake cannot form properly, not so slow that capacity is wasted).
• Feed solids concentration and slurry properties are constant.

Concept / Approach:
Increasing drum speed increases the number of cycles per hour and, up to a point, raises filtrate volume per unit time. However, extremely high speeds may reduce cake thickness (insufficient formation time) and reduce washing or drying efficiency. Thus, the first-order trend is that filtration rate increases with speed in the useful operating window, though not necessarily linearly across the entire range.

Step-by-Step Solution:

Verification / Alternative check:
Vendor performance curves show rising filtrate rate with speed until a plateau or decline due to thin cake and poor dewatering.

Why Other Options Are Wrong:

• Linear across the full range is rarely accurate due to formation/drying limits.
• Decrease or no effect contradicts observed behavior in the normal operating window.

Common Pitfalls:
Running too fast and sacrificing cake quality; throughput is not the only objective—washing and dryness matter.

Final Answer:
Increases