EENVIRONMENTAL PROTECTION (Absorption and Stripping unit, HCL scrubber)


This process is needed when gases or vapours to be blown-down are not soluble in water. The absorption of organic solvent contained in an air stream is performed by a special high boiling medium in the Absorption Column, equipped with special packing with low pressure drops and high efficiency. In the second Column (Stripping Column) the bottom solution from the first Column is stripped by direct injection of steam or by an heating system. The solvent is recovered from the top and the absorbent medium, free of the organic solvent, is recycled back to the absorption Column. The solvent is condensed and reutilized, if needed can be sent to further purification. This system is suitable for the purification of an air stream containing in example toluene, xilene and other aromatics, ketones, chlorinated, hydrocarbons, and so on. The advantages of this process are low energy consumption and stability of the absorption medium, which is higher if compared to active carbons.


Hot fumes containing hydrochloric acid are quenched by saturation with water to reduce their temperature. The liquid is pumped to quencher to provide the intimate contact between the liquid and gaseous phase. An automatic valve connected to the fire water provides the refrigerant fluid in case of pumps or electrical power failure. The gases rise a packed column and HCl is absorbed by a counter current demi-water flow. From the bottom of the column the recovered hydrochloric acid solution is circulated to the quencher and discharged in automatic under level control. A density analyser controls the flow of water to reach the required acid concentration. An heat exchanger removes part of the enthalpy of the inlet gas in order to reduce the water flow used to quench and obtain a concentration of about 20%. The gas leaving the first column flows to the second one where the residual hydrochloric acid is removed by an alkaline solution. A level controller discharges continuously the solution of sodium chloride collected at the bottom. A pH analyser regulates the quantity of caustic soda and controls the pH of the washing solution. A variable speed fan, regulated by a pressure control in the suction line, provides the head required to overcome the system pressure drops

Thermal or catalytic oxidizer unit are convenient when the concentration of the polluted vent are poor in solvent concentration, or when the polluted vent are containing more different solvent not suitable for the recovery.