Explain the working principle and design of a wet scrubber.

Wet scrubbers remove pollutants by contacting gas with scrubbing liquid. Spray towers inject liquid droplets counter-current to gas flow. Packed towers use packing for gas-liquid contact. Venturi scrubbers accelerate gas through throat where liquid is atomized. Design parameters include liquid-to-gas ratio (1-3 L/m3), pressure drop (0.5-25 kPa), and contact time. Effectiveness depends on particle size (better for >5 microns) and pollutant solubility. Wastewater treatment required for recirculated liquid.