Treatment Of Binary Polar VOCs From Off-gas By Silica Gel Using Coupled Pressure And Temperature Swing Adsorption

Adsorption and desorption of acetone and ethyl acetate(two typical polar VOCs)on silica gel have been systematically studied by vacuum swing adsorption(VSA)combined with temperature swing adsorption(TSA)process.It is found that the adsorption of acetone on silica gel is in conformity with the Langmuir-Freundlich model.Results also show that increasing flowrate,height to diameter ratio(H/D)and initial concentration is beneficial for the adsorption.The kinetic adsorptions are poorly fitted by Boyd model,showing that the adsorption of acetone on silica gel is controlled by external diffusion.The same thing happens to ethyl acetate.When the two polar VOCs are mixed for the adsorption,it is evidenced that ethyl acetate is more easily adsorbed on silica gel than acetone.This property allows ethyl acetate to partially replace adsorbed acetone when the adsorption approaches the saturation,suggesting a competitive adsorption between ethyl acetate and acetone on silica gel.Further modeling demonstrates that the whole kinetic adsorption of binary polar components could be divided into three regions: the free adsorption region,the competitive adsorption region and the equilibrium region.Additionally,the final ratio of adsorbed acetone and ethyl acetate on silica gel is highly dependent on height of the adsorption bed.The adsorbed polar VOCs on silica gel are observed to be desorbed by vacuum pumping,resulting in the increase in concentration.This desorption is also found to be significantly enhanced by increasing temperature from ambient temperature to 55?,achieving 2.5 times of concentration increase in the desorbed gas stream.