LabNotes - September 2008
Student says studying biogas at NETL
was a great learning experience
(Editor’s note: Penn State student Justin Weber spent his summer at NETL studying the effectiveness of a stabilization method on biogas combustion. This is his account of his research and his impressions of the value of working alongside NETL research staff.)
By Justin Weber
Justin Weber, summer intern in 2008 at the National Energy Technology Laboratory, peers at a biogas flame stabilization method.
As an aspiring mechanical engineering student at Penn State, I had the opportunity to work this summer at one of the country’s top national labs. More specifically, I got to work at the U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). This was an invaluable experience. Better than any class I have ever taken, and I probably learned more from this two-month adventure than two semesters taking classes.
I had the opportunity last summer through the Technical Career Intern Program between Penn State and the DOE’s Office of Fossil Energy to work in Washington, DC at DOE’s headquarters. I got to see the policy side of energy while experiencing Washington.
I liked this summer better, working with Peter Strakey and the other members of NETL’s Energy System Dynamics Group. I had a crash course in the basics of combustion, working on a fuel flexibility project. We were trying to see how effective a particular flame stabilization method, called a low swirl injector, was at stabilizing biogas flames.
Yes, biogas at a primarily fossil energy-oriented facility. NETL was tasked by DOE’s office of Energy Efficiency and Renewable Energy to develop and study fuel flexible burners. In other words, find a burner design that can stabilize flames at different gas compositions; whether it’s natural gas, biogas, hydrogen or all these gases mixed together. This is a rather daunting task because as the gas compositions change, the flame could become unstable causing the flame to go out, or could cause damage to the combustor.
The low swirl injector was developed by Robert Cheng at Lawrence Berkeley National Laboratory in California. This burner design is a fairly simple design sporting good benefits such as fuel flexibility, low cost and low NOx output (a contributor to smog).
Biogas is gas that comes from the anaerobic (no oxygen) breakdown of organic matter. This gas is produced at landfills, sewage treatment plants and specifically designed anaerobic digesters. Biogas is primarily made up of about half methane and half carbon dioxide. Unfortunately, carbon dioxide poses a threat to stable combustion. As you probably have heard by now, carbon dioxide likes to trap heat. As the carbon dioxide interacts with the flame, this could potentially cool the flame down enough that it becomes unstable and blows out.
We simulated biogas by combining methane and carbon dioxide at different dilution levels. Then we compared that to dilution with nitrogen, which is inert and should not affect the flame.
After doing numerous test runs, we came to the conclusion that this low swirl injector can effectively stabilize the biogas simulated flame. The carbon dioxide does affect the flame, both through cooling, as expected, and its effect on the physical reactions taking place. The nitrogen dilution has no effect on the flame.
The low swirl injector is fuel flexible, depending on the definition of fuel flexibility, because it can stabilize methane flames, natural gas flames, hydrogen flames, and now biogas flames. This burner can now be used to stabilize these flames in industrial processes such as cement making.
The eventual goal is to use this burner design with micro turbines to produce electricity from biogas and other fuels. However, more information is needed to study how this burner design adapts to the turbine environment.
In the end, this has been a very productive summer. I learned a great deal of information while helping to secure energy for the future.
This fall I head back to Penn State to learn more and conduct research on oxygen enhanced combustion of coal in a fluidized bed reactor. I am also taking a class titled Intro to Combustion. After this summer, I might not have to study for that class.