Experimental Study On Absorption Of Volatile Organic Compounds From The Pharmaceutical Industry

With the rapid development of pharmaceutical industries in recent years, China has become the biggest producer of APIs and medicine intermediates. But the resulting air pollution (e.g. volatile organic compounds, VOCs) problem has attracted wide concerns. Compared to other treatment methods of VOCs, absorption method is more widely employed in real application due to its advantages as technical maturity easy operation, wide operating range, low cost and less secondary pollution etc. In this paper, the typical VOCs exhausted from pharmaceutical industries were selected as the treatment object. And various absorbents were tested for the removal of toluene. The best absorbent and optimal composition were then screened out based on the economy and feasibility. Finally, a process design was made for VOCs absoiption treatment.First, experiments of toluene absorption were conducted to compare the performances of various absorbents including white oil, engine oil, water-white oil, water-wash oil and sodium stearate solution in terms of feasibility, economy and absorption efficiency. The results showed that the best absorbent was water-white oil system. And the removal efficiency of84.7%could be achieved under the conditions as:water-white oil ratio=1:1; emulsifier content=5wt%, toluene concentration=200ppm.And then, the relationship between different contents of emulsifier, HLB values and stability of emulsifier was analyzed on the basis of water-white oil absorbent with span and tween as emulsifiers. When the dose of emulsifier is2.5wt%of the amount of water-white oil and HLB=12, the removal efficiency of400ppm was84.6%, and no foaming phenomenon was observed after long-term aeration.After that, the influence of inlet toluene concentration, inlet flow rate and absorbent temperature on the removal efficiency and the saturated absorbing capacity were investigated with the best emulsion as the absorbent. The absorption efficiency decreased with increasing inlet concentration; when the inlet flow rate was6L/min, the absorption efficiency reached its maximum value of87.9%; In general, the increase of emulsion temperature was in favor of the removal of toluene; The absorbing capacity of the absorbent was determined to be13.8mg/g of toluene. Furthermore, the absorption performances of the mixed waste gas containing toluene, dichloromethane and ethanol were investigated and their removal efficiencies could be obtained to be84.6%,74.9and100%, respectively.Finally, the process design of VOCs absorption engineering (gas flow rate=10000m3/h, the concentration of toluene=400mg/m3, water-white oil as absorbents) was conducted and the economy feasibility was evaluated.