Development and modeling of a continuous simulated moving bed ion exclusion process for the separation of acid and sugar
The emission of large quantities of the greenhouse gas carbon dioxide into the atmosphere, as well as our increasing dependence on foreign oil supplies and the need to stimulate the tagging farm economy, has prompted research in the production of renewable liquid fuels from lignocellulosic materials. Acid hydrolysis of the cellulosic fraction of these materials into sugars that can be fermented to ethanol is one option. In support of this approach, a simulated moving bed ion exclusion chromatography system was constructed for the continuous separation of the product sugars from the acid used to effect hydrolysis. A numerical simulation model of the process is presented here. Our system consisted of 4 zones of 18 resin-packed columns, each approximately 820 mL in size, arrayed about a central manifold system using solenoid valves to control fluid flow. The model is based upon experimental data from the system arrayed with 9 doubled and 18 single columns. The numerical simulation model was used in conjunction with statistical experimental design techniques to probe the optimum operating conditions: the selection of the simulated flow rate, the number of columns needed in each zone and the appropriate number of columns in the system as a whole. A development facility more than 10-times the current system size is being pursued.