When a formaldehyde absorber develops white deposits in cold or stagnant sections, review formaldehyde concentration, water evaporation, stabilizer conditions, minimum liquid temperature, shutdown residence time, distributor geometry, and deposit identity. The fouling mechanism can be fundamentally different from mineral scaling.

When a geothermal H₂S scrubber develops silica-rich scale, evaluate upstream brine carryover, cooling profile, water chemistry, pH, packing openness, distributor blockage, and solids removal. A corrosion-resistant packing can still lose capacity rapidly if mineral-bearing droplets continuously enter the tower.

When siloxane-rich or oily condensate enters a biogas packed scrubber, it can alter surface wetting, promote foam, contaminate the recirculation loop, and reduce effective contact area without producing conventional scale. Upstream condensation control, knockout separation, liquid analysis, packing material, and compatible cleaning should be reviewed together.

When a nitric-acid packed absorber leaves excessive NOx, identify NO and NO₂ separately. NO oxidation, oxygen concentration, residence time, acid temperature, acid strength, cooling, and packing contact must be evaluated together. Additional bed height may provide limited benefit if gas-phase NO oxidation is controlling.

When excess water enters a sulfuric-acid drying tower, local acid dilution can release heat, change corrosion conditions, reduce drying performance, and create thermal stress in ceramic or other internals. Upstream liquid separation, acid concentration, temperature, dilution location, distribution, and upset conditions should be part of the design basis.