| With the rapid development of economy, the environmental pollution caused by industrial emissions of volatile organic compounds (VOCs) is getting worse year by year. Since atmospheric VOCs pose great threats to human health and environment, efficient and economic abatement technologies are the hot issues at present. Absorption method has been widely used for several advantages, such as mature processing and low running charge. Besides, VOCs can be recovered and recycled by desorption, which have good economical and ecological benefits.The treatment of waste gases containing toluene with biodiesel-based microemulsion as the absorbent was studied in this dissertation, and the absorption efficiency for simulated waste gases containing toluene was further investigated. The main research contents are as follows:Microemulsions were prepared and the pseudo ternary phase diagrams were obtained through titrimetric method. The stability of the microemulsion was characterized by the area of microemulsion region to gain the optimum microemulsion. The results showed that the optimum conditions for preparation of absorbents are as follows:the mass ratio of surfactant (tween-80) to cosurfactant (n-butylalcohol) was2:1and the HLB value was12.33at room temperature, respectively. Comprehensive consideration of stability and economy of microemulsions, the optimum system made up of tween-80(25%, mass fraction), n-butanol (12.5%), biodiesel (46.4%) and water (16.1%) was selected from the boundary points when Km was2:1. The optimum microemulsion absorbent was well-suited for toluene absorption with a removal efficiency of93.2%. The relationship between the kinematic viscosity of microemulsions and temperature was remarkable suited to the power function. The viscosity decreased with increasing temperature.The absorption efficiency of the optimum microemulsion absorbent for toluene was systematically investigated. Results showed that the absorption efficiency was notably influenced by operational variables such as inlet concentration of toluene, the intake air flow rate and temperature. The absorptive performance was improved with increasing inlet toluene concentration. The absorption efficiency for toluene decreased with increasing gas flow rate and the temperature, and low temperature could do good to facilitate operation. The saturated adsorption amount of activated carbon fibers (ACF) and modified activated carbon for toluene were about2.3and1.5times than that of the microemulsion absorbent. However, the price of ACF and modified activated carbon were approximately42and2.25times than that of the microemulsion. respectively. Thus it proved that microemulsion was a good absorbent with higher cost-effective compared with ACF and modified activated carbon.To reuse the absorbents, toluene-water can be distilled from the saturated absorbents by azeotropic distillation method and recovered as a liquid by condensation, and then toluene and water could be separated by separating funnel. Toluene can then be recovered for industrial utilization. GC-method based on internal calibration principle was developed for determination of toluene content in the saturated absorbents before and after distillation. In this work, the desorption ratio is as high as99.13%. indicating toluene can be easily desorbed from the saturated absorbents. Compared the removal effect between the original and regenerated absorbent, the recycled absorbent showed a good absorption performance. The absorption rate of the original, primary recycled and secondary recycled absorbents were86.17%.84.73%and83.85%, respectively. The attrition rate of secondary recycled absorbents is only9%. Therefore, azeotropic distillation was a feasible method to regenerate the saturated absorbents. |
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