Study On The Screening Method Of Absorbent For Volatile Organic Compounds With Toluene As An Example

Volatile organic compounds (VOCs) is a common pollutant in the atmosphere, direct emission of VOCs will cause huge threat to the environment and human health. As one of the most efficient VOCs processing technology, absorption technology has been comprehensively studied. The key of absorption technology is the selection of the efficient absorbtent, the thermodynamic and kinetic factors of the absorption process were comprehensively considered in this paper. By comparing the results of static gas-liquid equilibrium experiments with the results of dynamic bubble absorption experiments and combining the results of screening experiments with the results of simulation of the UNIFAC model, a new method for screening absorbent for VOCs has been set up.The 0# diesel oil, methyl silicone oil, PEG 400, DBP, DOP and DEHA were choosed as the absorbents in this paper, by using static gas-liquid equilibrium experiments and dynamic bubble absorption experiments which were all carried out under 303.15 K, a detailed comparison and an evaluation of these six absorbents were undertaken in purpose of toluene absorption.The results showed that the absorption performance of DBP, DOP and DEHA for toluene were better than the others; and besides this, they also had moderate viscosity, high boiling point, low saturation vapor pressure and stable chemical properties, which made them have the potential for treating toluene gas efficiently.UNIFAC model is used to simulate the gas-liquid equilibrium under 303.15 K for the binary system of PEG 400, DBP, DOP, DEHA and water with toluene in the whole concentration range of the phase equilibrium data, the excess Gibbs function and the absorption potential of the binary system were calculated. Efficient absorbent were screened according to the maximum excess Gibbs function and absorption potential. The results showed that, for a low inlet toluene concentration, the simulation results agreed well with the bubble absorption experimental results. Above all, the maximum excess Gibbs function and the absorption potential can be used as a thermodynamic standard to screen the absorbent for toluene gas.Through a series of static gas-liquid equilibrium experiments, dynamic bubble absorption experiments, UNIFAC model simulation and considering the other absorbent selection factors, a scientifically and accurately screening method of the selection of absorbent for toluene gas had been set up, which will provides valuable information for the screening of industrial absorbent in the absorption process.