Small Scale Ethanol Drying

This program exceeded all key milestones. Using cellulose Waste, CMS demonstrated novel ethanol drying membranes via small scale dephlegmation process that yields fuel grade ethanol (FGE) at a lower cost than large switch grass ethanol plants. This success yields positive value for cellulose waste. We achieved targeted EPA goals of developing low cost environmentally friendly systems to enhance recovery of waste streams. In addition to this success we have lined up key partners for both the fabrication of membrane systems as well as field testing in related applications. In Phase I, we fabricated chemically resistant hollow fiber (HF) membrane modules that had desired chemical resistance and transport properties consistent with the goals associated with the final ethanol drying step in small scale manufacturing processes. There was success with flat sheet systems for ethanol-water separation and though HF and flat sheet systems provided excellent performance results, HF is preferred in Phase II. This is because of excellent relationships with commercial partners combined with associated better design and cost features. Using the HF membranes prepared in the earlier tasks, we evaluated these materials specifically under conditions consistent with small scale ethanol manufacturing sites for both liquid phase and vapor phase separation of water from ethanol. We obtained excellent flux and separation. This included very high water transport rates and very high water-ethanol separations factors. This excellent flux and separation in combination with stability was demonstrated over a wide range of operating conditions. Long term testing showed the membranes had excellent stability. This is consistent with parallel result, and also consistent with the chemistry of the CMS materials. Reviewers had concerns related to CMS membrane water/ethanol selectivity but tests in Phase I showed excellent water/ethanol separation which likely related to the unique chemistry of the CMS membranes. We took lab results and put them into the small scale membrane module/dephelmation system published by Leland Vane from the EPA and comparing to published results from the Department of Energy on FGE costs. We demonstrated CMS membrane drying costs were actually less than large scale molecular sieve driers. Most important results showed that waste stream cellulose stream actually had significant positive value ($16-$18/ton). Phase II will build and evaluate pilot system. Fortunately we have established a number of key relationships with membrane suppliers, ethanol engineering design firms and the EPA test sites. This positions CMS well for both Phase II success and subsequent commercialization.