ISU ponders permanent biomass cofiring after test burn
Armed with newly-compiled results from a four-month biomass test burn, Iowa State University representatives will discuss the parameters and requirements of permanent biomass utilization with the state Department of Natural Resources.
Together with NextGen Biofuels Inc., the university cofired biomass in its coal-fired combined-heat-and-power plant over the summer. Working with both wood pellets and wood chips, the test burns started at 5 percent biomass and jumped up to 10 percent and 15 percent, according to Rob Ravlin, NextGen president. Pellets were also tested at a 20 percent blend. “[The tests were] very successful,” he said. “If the will is there, we can immediately displace a large percentage of coal in existing boilers without any capital investment required.”
The tests in ISU’s boiler combined biomass carrying a Btu value of 7,800 per pound with a blend of western Kentucky and southern Illinois coals at 11,800 Btu per pound. They showed an 11.5 percent reduction in sulfur dioxide; a .5 percent reduction in carbon dioxide; a 24.2 percent reduction in particulate matter; and a 6.5 percent reduction in carbon monoxide parts per million. Not surprisingly, though, the tests also showed a 3 percent increase in nitrogen oxide, as biomass is a more volatile fuel source than coal, Ravlin said. The results will vary from boiler to boiler and with coal type, he added.
“I would agree the tests were successful,” said Jeff Witt, assistant director of utilities at the university. “We obtained the information we need to say yes we can do this.” The decision on whether to move forward will depend on what requirements the DNR outlines for permanent cofiring, as well as the cost to the university, as biomass is currently more expensive than coal, Witt said. “Based on data, I don’t think it’s going to be an issue with the DNR,” he added. Ravlin echoed that same sentiment. Later this month, Witt’s team and NextGen will present an assessment of the findings and DNR’s requirements to the university administration, which will make the final decision.
Witt intends to permit the CHP plant to burn up to 15 percent biomass, using 2-inch minus wood chips instead of pellets because of their cheaper cost. That means, though, that the chips will need to be sized appropriately for the plant’s processes. “Our goal is to blend this fuel with existing fuel handling systems,” Witt said, adding that chips too large or small will pose problems. “There’s a window there of what we need.”
“We are using these tests as an incubator to jump-start the local biomass market to supplement or eliminate the imported biomass,” Ravlin said. Fortunately for the company, the tests have garnered attention from many local utilities looking to reduce emissions, he added.