|Ralph “Rusty” Schroedel and Steven Delight both have experience handling gas as an energy source for water resource recovery facilities. They were invited to participate in the U.S. Department of Energy workshop because of their extensive biogas utilization experience.
Ralph “Rusty” Schroedel
Schroedel, a Water Environment Federation (WEF; Alexandria, Va.) member since 1974, is a member of WEF’s Residuals and Biosolids, and Municipal Resource Recovery Design committees. He works as a client service manager for Brown and Caldwell (Walnut Creek, Calif.). He has worked on projects with biogas for most of his 38-year career.
Delight, California Water Environment Association (Oakland) member since 2009, works as a senior engineer for Dublin San Ramon Services District. He first started working with biogas when the district started a project to install fuel cells in 2006. He was project manager for the installation and worked on the project until its conclusion in March 2013.
Several contaminants found in gas, especially such types of biogas as anaerobic digester gas, seriously affect fuel cells. So the Fuel Cell Technologies Office of the U.S. Department of Energy convened a workshop March 6–7 to explore the problem and identify potential solutions.
The Water Environment Federation (WEF; Alexandria, Va.) and California Water Environment Association (CWEA; Oakland) were represented along with various other sectors at the workshop. Together, the workshop attendees explored current gas-cleaning technologies and identified research needs for increased performance and use of fuel cells.
The workshop began with an introduction to the problem. Very small concentrations, starting in the parts-per-billion range, of several compounds found in natural gas, biogas, and gas associated with petroleum production greatly affect fuel cells. For example, a breakthrough of sulfides in the gas-stream made its way into the Dublin San Ramon Services District (Dublin, Calif.) fuel cell. Once the sulfides made their way into the fuel-cell stack, temperatures fluctuated, affecting the stack’s integrity, electricity production, and life. The district had to pay to replace the polishing media rendered useless by the bad gas. The cost was about $40,000. Also a white powder composed of chlorine coated the interior of the stack, further shortening its life. In 2013, the district removed its fuel cells. During the workshop, speakers presented information on similar problems and an overview of how the quality of gas affects fuel cells.
Three major sessions followed the introduction. The first addressed opportunities inherent in using different fuel types and problems associated with impurities. The second covered industry experiences managing fuel impurities in real-world applications. The third focused on research and development needs as well as opportunities for managing impurities, avoiding gas emissions, and flaring, especially for gas associated with petroleum production.
Manufacturers, researchers, and academics gave presentations during each session and then participated in a panel discussion, taking questions and comments from attendees. The attendees then separated into one of three breakout groups addressing each session topic.
Through the breakout sessions, attendees attempted to identify the impurities that have the greatest affect on fuel cells and prioritize the state of the technologies to remove these contaminants. They also reviewed the ability of current clean-up technologies to remove the critical contaminants, the cost issues relating to the systems, and what systems could benefit from increased research and development. Participants also attempted to identify which short- and long-term research and development activities would be most beneficial to advance the deployment of fuel cell systems. Several suggested forward-thinking concepts and options. Participants also noted that field trials and applications will be needed.
Several species of sulfur — especially carbonyl sulfide — siloxanes, chlorine, and organic sulfur compounds received the most attention. The participants also identified other critical issues to be addressed, including on-line, low-level measurement of contaminants, the negative effects of contaminants on fuel cells after breakthrough from a clean-up system, and the potential for improving fuel cell materials to handle contaminants.
The Department of Energy plans to issue a draft report of the workshop findings — first to participants and then to a larger community of potential fuel cells users. It also plans to use the information to identify future research projects.
— Ralph Schroedel, WEF member, and Steven Delight, CWEA member