Treatment Of Industrial Waste Gas-loaded With Toluene Using Liquid Absorption And Resource Recovery Method

Industrial organic waste gas is a main source of atmospheric pollution and its impact on human health is getting an increasing attention. There is now still lack of effective technologies for the treatment of organic waste gas, especially hydrophobic VOCs. The present study, taking gaseous toluene as a target pollutant, conducted a research on treatment of organic waste gas by means of liquid absorption and resource recovery method. The main items included: absorption efficiencies of different types of absorption liquids to toluene waste gas, processes and conditions of absorption liquid regeneration and toluene recovery by distillation, design of a pilot scale system, and setting up of the pilot equipments and evaluation of the absorption performance.A self-designed dynamic absorption device was applied to make a full comparison of absorption efficiencies between different types of absorption liquid to toluene waste gas. One the basis of this, microemulsions formed by some fluorocarbon surfactants were designed, their mass transfer efficiency and mechanism under different conditions was investigated, and a microemulsion with the best performance was selected. Based on absorption experiments under different conditions for toluene waste gas from laboratory to pilot scales, the processes and technological parameters for the selected microemulsion were proposed.Some important achievements were made from the present study. A microemulsion with the best performance, consisted of FSO100, BC(a kind of higher alcohol) and water(FSO100: BC: water=1: 70: 29), was developed. Compared with varieties of aqueous absorption liquids reported in literatures, it shows the greatest capacity for absorbing toluene from waste gas. The distillation conditions(90-95℃) for the regeneration and toluene recycling of the microemulsion were determined. A very high toluene recovery rate(up to 90%) was achieved from the saturated microemulsion by this distillation and the regenerated microemulsion largely kept its initial absorption performance during reuses. The suitable absorption conditions for the microemulsion were obtained, mainly including: an inlet toluene concentration < 4000 mg/m3, an absorption liquid temperature < 30℃ a treating capacity of 1-2 m3/kg?h. Under this condition, the absorptivity to toluene waste gas is greater than 90%, the tail gas could be discharged directly with a concentration of less than 40 mg/m3(toluene discharged standard from industrial waste gas), and the saturated toluene absorption capacity can reach 30 mg/g.These results provide a technological supporting for the treatment of organic waste gas using liquid absorption and resource recovery method. The developed fluorocarbon surfactant microemulsion and related absorption processes and parameters can be applied to practical projects to treat waste gas- loaded with toluene or other hydrophobic VOCs.