When a packed scrubber develops severe foam immediately after cleaning, detergent or surfactant residue should be considered before changing packing or demister design. Residual cleaner in packing, distributor branches, sump, or piping can alter surface tension, increase liquid holdup, raise pressure drop, and create secondary mist carryover.

A packed tower can pass commissioning with water and flood with the real process liquid because viscosity, density, surface tension, temperature, wetting, and foaming behavior change liquid holdup and hydraulic capacity. Water testing should be treated as a commissioning tool, while final hydraulic assessment must use actual process-fluid properties.

A bromine caustic scrubber can develop an oxidizing, salt-rich circulating liquid that differs substantially from fresh alkaline solution. Packing selection should therefore consider bromine species, temperature, dissolved-solids accumulation, blowdown, distributor fouling, demister exposure, and all wetted materials before finalizing the packing resin and geometry.

When SO₂ is scrubbed with hydrogen peroxide, the circulation loop can progressively accumulate sulfate and sulfuric-acid-containing products while peroxide is consumed or decomposed. Material compatibility, heat release, liquid properties, demister duty, blowdown or recovery, and oxidant control should therefore be based on the evolving operating solution rather than fresh reagent alone.

When a kraft-mill reduced-sulfur scrubber develops foam and sticky deposits, investigate black-liquor, soap, or contaminated-condensate carryover, not only H₂S/TRS gas loading. Recirculation contamination, packing wetting, foam, upstream separation, demister fouling, and cleaning should be reviewed as one system.