Grantee Research Project Results
Final Report: Small-Scale Ethanol Drying
EPA Contract Number: EPD07047Title: Small-Scale Ethanol Drying
Investigators: Majumdar, Sudipto
Small Business: Compact Membrane Systems Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2007 through August 31, 2007
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2007) RFA Text | Recipients Lists
Research Category: SBIR - Agriculture and Rural Community Improvement , Small Business Innovation Research (SBIR)
Description:
Membrane processes are ideal for small applications because the key components in membrane processes are the membranes themselves, and the associated hardware scales down linearly. Although many existing biomass-to-ethanol plants are at 40 million gallons per year or greater, very few are at 10 million gallons per year or less. A membrane process will lend itself to focus on small-scale fuel-grade ethanol production. In addition to being ideal for small-scale operations, membrane processes are ideal for removing the minor component. Specifically, fuel-grade ethanol at the fermentation level has upwards of 5–8 percent ethanol in water, which can be achieved with silicon rubber membranes. For highly concentrated streams, such as 90 percent ethanol, a different membrane, as proposed by Compact Membrane Systems, Inc. (CMS), that preferentially removes water would be ideal for the final drying to 99.5 percent ethanol.
The proposed concept is to operate membranes and related processes to convert low volumes of biomass to fuel-grade ethanol. The process consists of four components. These components are: a small fermentation system that will convert biomass to ethanol containing approximately 5 percent ethanol; a pervaporation membrane that preferentially permeates 20–25 percent ethanol; a simple unit operation (e.g., dephlegmator) that takes the 20–25 percent ethanol up to 90–95 percent ethanol; and a second drying membrane device. In this drying case, because water is the minor component at 5–10 percent, this membrane will be water permeable. The net result from the process is the conversion of 5 percent ethanol to 99.5 percent fuel-grade ethanol in one small-scale process.
Summary/Accomplishments (Outputs/Outcomes):
In Phase I, chemically resistant hollow fiber membrane modules were fabricated. These had the desired chemical resistance and transport properties consistent with the goals associated with the final ethanol drying step in a small-scale manufacturing process. Parallel successes with flat sheet systems for ethanol water separations also were achieved. Although both systems provided excellent performance, the use of hollow fiber is the preferred approach that will be used in future efforts. This is primarily because of CMS’ relationships with commercial hollow fiber partners in combination with better design and cost features. Hollow fiber membranes were evaluated under conditions consistent with small-scale ethanol manufacturing sites for both liquid phase and vapor phase separation of water from ethanol. Excellent flux and separation were obtained. This included very high water transport rates and very high water ethanol separation factors. The excellent flux and separation in combination with stability was demonstrated over a wide range of operating conditions.
Long-term testing demonstrated excellent membrane stability. This is consistent with parallel results and also consistent with the chemistry of the membrane materials. Phase I testing demonstrated excellent water ethanol separation, which probably relates to the unique chemistry of the CMS membrane materials.
Laboratory results were inserted into the small-scale membrane module/dephlegmation system model published by Leland Vane of the U.S. Environmental Protection Agency (EPA). These were compared to published results from the Department of Energy for fuel-grade ethanol costs. The results demonstrated that drying costs, using the CMS approach, were less than large-scale molecular sieve driers. Equally important, waste stream cellulose actually had net positive value when used for ethanol production in tandem with the CMS approach.
Conclusions:
This project exceeded all key milestones. The demonstration, using cellulose waste, of the novel ethanol drying membranes with a small-scale dephlegmation process yields fuel-grade ethanol at a lower cost than large switchgrass ethanol plants. This success leads to a positive value for cellulosic waste. The targeted EPA goal of developing low-cost environmentally friendly systems to enhance recovery of waste streams was achieved. In addition to this success, key partners have been engaged for both the fabrication of systems as well as field testing in related applications.
The broad objectives of the Phase I Small Business Innovation Research project were to demonstrate that a low-cost membrane-based system can be developed and applied simply to produce low-cost fuel-grade ethanol (99.5% ethanol) from small-scale biomass systems. Specifically, the results of this effort demonstrate that:
- the waster cellulose feed stream has a positive feed value (e.g., greater than $3/dry ton);
- it is feasible to remove water from 25 wt% ethanol up to 99.5 wt% ethanol;
- the proposed ethanol drying system using CMS membranes either in pervaporation or vapor permeation mode is the lowest cost technology for small-scale ethanol plants;
- the proposed technology provides a cost savings of greater than 14 percent compared to conventional pressure swing adsorption technology;
- the proposed technology using CMS membranes in the final drying step offers substantial cost savings over a similar system using PVA membranes;
- the proposed technology and waste material feedstocks are competitive with a 70 million gallons/year plant using the conventional ethanol drying technology and switchgrass feedstock; and
- the procedure was environmentally friendly for recovery of waste material and reduction of life-cycle environmental impacts given the positive value of the waste feed steam.
Supplemental Keywords:
small business, SBIR, waste stream cellulose ethanol production, harsh chemical separations, solvent drying, ethanol manufacturing,, RFA, Scientific Discipline, Sustainable Industry/Business, Environmental Chemistry, Sustainable Environment, Technology for Sustainable Environment, Environmental Engineering, agricultural byproducts, biomass, alternative fuel, ethanol, bio-based energySBIR Phase II:
Small Scale Ethanol Drying | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.