Heterogeneous azeotropic distillation: Experimental and simulation results



Experimental measurements for an industrial azeotropic distillation tower that dehydrates secondary butyl alcohol (SBA) show erratic operation that only approaches a steady state. These are explained with steady-state simulations which show that slight variations in the aqueous reflux rate cause many trays to shift from homogeneous to heterogeneous operation, accompanied by significant changes in the SBA purity, with water or entrainer contaminating the bottoms product. When other methods failed, an arc-length homotopy-continuation method made small adjustments in the reflux ratios to obtain close agreement with the measurements.