VOCs are removed from the exhaust gas by contact with the washing solution, and then neutralized, oxidized, or destroyed by other chemical reactions using chemical agents. The commonly used chemical washing equipment is the washing tower. Under the action of the fan, the exhaust gas flows upward, and the chemical washing solution is sprayed from the top of the tower downwards. VOCs are fully contacted and reacted with the washing solution to be removed. Generally, strong acids and strong bases are chosen as detergents to remove odor and VOCs components through mass transfer and chemical reaction processes in the washing tower. Strong acids (such as H2SO4) remove nitrogen-containing odorants such as ammonia and amines, while strong bases and oxidants remove sulfur-containing odorants such as H2S and R-SH.

There are four main types of washing towers: packed tower, spray tower, plate tower, and bubble tower. The ratio of washing solution to exhaust gas flow rate (liquid/gas ratio) is generally 1:3 L/m3, the packing height is generally 2-5 meters, and the gas flow rate in the empty tower is generally 0.5-1 meter/second. A well operated filling tower can achieve a processing effect of over 90%.

2. Process schematic diagram