An Equilibrium Based Process Modeling of a Packed Bed Scrubbing System for the Removal of Model Tar Compounds

Wet scrubbing systems often use water as a solvent for producer gas tar removal. The major drawbacks with the water-based wet scrubbing systems are poor solubility of tar compounds and the costly wastewater treatment. Vegetable oils can be considered as a potential solvent for the removal of producer gas tars. This study considers soybean oil as a solvent for the removal of model tar compounds. Soybean oil is one of the largest sources of vegetable oil in the United States. In addition, soybean oil is renewable, plant based, CO2 neutral, and hazard free. The aim of this study is to develop an equilibrium based process model of a wet packed bed scrubbing system. The wet packed bed column is modeled using “RadFrac” block of the Aspen PlusTM software. Raschig rings 6 mm in size are used as the packing media. A model tar compound mixture consists of benzene, toluene and ethyl benzene. Because the model tar compounds are non-polar, Peng-Robinson and RK-Soave thermodynamic property methods are considered for the process modeling. The effect of packing bed height, solvent temperature, and liquid-to-gas ratio on the tar removal efficiency will be presented. The process model will be useful in the design and optimization of a laboratory and pilot scale oil-based packed bed scrubbing system for removal of biomass producer gas tars.