Wet Scrubber

Packed bed scrubbers are vertical towers filled with packing media to increase the interfacial area between gas and liquid. Contaminated gas flows upward while scrubbing liquid flows downward, enabling efficient mass transfer and absorption of acid gases such as SO2, HCl and chlorine-containing fumes. Packed-bed designs are particularly strong where gas-liquid contact and high mass transfer are required, and they can achieve very high removal efficiencies (often exceeding 95% for soluble gases when properly designed). Design choices — packing type, liquid distribution, and residence time — determine performance and pressure drop.

Venturi scrubbers use a high-velocity constriction to atomize the scrubbing liquid and create intense gas-liquid interaction; they excel at particulate removal (including very fine aerosols) because of the energetic collisions between droplets and particles. Although venturi designs can remove some gaseous contaminants, their mass-transfer for soluble gases is generally poorer than packed-bed absorbers, so their primary application is particulate and fume control, or as a pre-treatment stage ahead of an absorber. This makes venturi scrubbers an excellent choice for processes that generate high particulate loadings or sticky aerosols.

Cyclo-vane scrubbers combine centrifugal separation with wetted surfaces and are compact ways to remove coarse particulates and droplets with low maintenance. Multi-stage scrubbers combine the strengths of different technologies — for example, a venturi stage for particulate capture followed by a packed-bed stage for acid gas absorption — to meet strict emissions targets in a single footprint and with optimized operating costs. These hybrid systems are particularly useful where both particulate and gaseous pollutants are present.

Certain industrial processes, such as metal finishing and chemical manufacturing, generate highly corrosive and toxic acid gases (e.g., chromic acid vapours, chlorine). Systems treating these streams must use corrosion-resistant materials (stainless steels, FRP, or lined carbon steel), carefully selected scrubbing chemistries (e.g., alkaline washes for acidic gases), and robust monitoring and safety interlocks. For chlorine (Cl2) in particular, alkaline scrubber solutions (sodium hydroxide or sodium thiosulfate formulations) convert free chlorine to chloride salts, effectively neutralizing the gas before discharge. Design for chlorine service also emphasizes redundancy, containment, and safe handling of spent scrubbing liquor.

Incineration of medical waste produces acid gases, dioxins, furans and other hazardous emissions; wet scrubbers for this application often use multiple stages — quench and gas cooling, particulate capture (venturi or cyclonic), and an absorber stage (packed bed) with chemistry targeted at acid gases and specific toxic species. The multi-stage arrangement ensures temperature control (to prevent formation of certain byproducts) and maximizes removal of both particulate and soluble gaseous contaminants.