Vacuum filtration applicability: for which duty is a vacuum filter most suitable in liquid–solid separation?

Introduction / Context:
Vacuum filters (e.g., rotary drum, disc, belt) are workhorses for continuous liquid–solid separation in mineral processing, chemicals, and wastewater treatment. Choosing them correctly requires understanding their advantages and limitations with respect to liquid properties and cake behavior.

Given Data / Assumptions:

• Aqueous or low-volatility slurries.
• Moderate viscosity liquids and vacuum levels typical of plant equipment.
• Goal: remove suspended fines and produce a filter cake.

Concept / Approach:
Vacuum filtration applies a pressure differential by lowering pressure on the filtrate side. It is effective for slurries containing fine solids where forming a permeable cake is feasible. High vapor-pressure liquids tend to flash under vacuum, causing gas breakthrough and poor operation. Very high viscosity liquids restrict flow severely and are better handled by pressure filters or centrifuges.

Step-by-Step Solution:
Match vacuum filters to duty: continuous removal of fines and cake washing/drying.Eliminate unsuitable cases: high vapor pressure (flashing) and very viscous liquids (excessive resistance).Choose "removal of fines from liquid" as the proper application.

Verification / Alternative check:
Vendors specify maximum filtrate viscosities and caution against volatile solvents unless controlled with condensers/seals.

Why Other Options Are Wrong:
High vapor pressure: vacuum induces flashing and unstable operation.Very high viscosity: leads to very low flux; pressure filters are preferred.

Common Pitfalls:
Attempting vacuum filtration of solvent-rich slurries without vapor handling; overlooking precoat/filter aid methods that can transform marginal slurries into filterable ones.

Final Answer:
removal of fines from liquid