Gas–liquid contacting for highly corrosive services: which contacting device is generally the most suitable?

Introduction / Context:
Handling corrosive gas–liquid systems (e.g., acid gases with aggressive solvents) demands contacting equipment that can be economically built from corrosion-resistant materials. The choice affects maintenance, uptime, and total cost of ownership. While trays can be fabricated in alloys, packed towers offer unique flexibility in material selection and surface area per unit volume.

Given Data / Assumptions:

• Highly corrosive fluids requiring nonmetallics or ceramic options.
• Desire for broad material choices and easy replacement of internals.
• Normal pressure and hydraulic ranges for absorption/stripping services.

Concept / Approach:
Packed towers can use ceramic, graphite, or plastic (e.g., PTFE, PVDF, PP) packings and internals, limiting metal exposure. This reduces corrosion and permits operation where alloy trays would be prohibitively expensive. High surface area of packing promotes mass transfer at moderate pressure drop. Trayed columns are workable but often require costly exotic alloys for decks, weirs, downcomers, and support structures.

Step-by-Step Solution:

Verification / Alternative check:
Industry experience and vendor offerings show wide use of ceramic/plastic packings in acid gas absorbers and scrubbing systems.

Why Other Options Are Wrong:

• Sieve and bubble-cap trays can work but typically force expensive alloy construction and more complex maintenance.
• “None” is incorrect given the strong case for packed towers.

Common Pitfalls:
Poor liquid distribution causing channeling; choosing packing unsupported by appropriate corrosion-resistant internals; neglecting thermal effects on plastics.

Final Answer:
Packed tower