Technology Developments in Psa Ethanol Dehydration
Charles D. Tereck, KATZEN International, Inc., 2300 Wall Street, Suite K, Cincinnati, OH 45212
U.S. production of motor fuel grade ethanol (MFGE) has grown at the rate of 20% per year for the past 12 years outpacing all other chemical and biochemical products. Concurrently, there has been similar growth worldwide. Pressure swing adsorption (PSA) application to the dehydration, using molecular sieve zeolites, of azeotropic ethanol/water mixtures has been key to the economic, environmental, and safety requirements in this expansion. Methods for energy reductions and consequent cost savings will be presented that show dramatic improvements over first generation azeotropic distillation systems as well as resistance to market penetration by various membrane systems. Design parameters and heuristics are discussed that have resulted in more than 1,000,000 cycles on the same initial charge of molecular sieve media. Integration of the adsorption system with the distillation, energy recovery, and vacuum systems are key to the overall operability and viability of the production plant in terms of both a fermentation facility and stand-alone dehydration up-grader unit. Smaller in market but more technically challenging is the production ultra-low moisture product for downstream chemical synthesis and anhydrous high grade ethanol meeting U.S.P. specifications. Developments are presented that allow tailoring the final product quality in light of the catalytic activity of the molecular sieve stationary phase.