By Peter Rugg, MacArthur Energy
At the recent ACC Fuel Flexibility Conference in Chicago, there was considerable discussion relating to variations in fuel. Historically, boilers were designed for a specific fuel, usually the closest or most economically available. Periodic regulation, emissions standards, transportation logistics and changing coal prices have forced utilities to purchase coal from farther afield to remain in compliance. These variations in fuel characteristics create new problems with burner operations, including grindability, ash and slagging inefficiencies.
Additionally, with few tools previously available to clean up fuel prior to combustion, costly systems to clean up off gasses post-combustion (scrubbers) were added to meet emissions standards. As a result, to date most technologies employed have focused on combustion tuning and optimization, and the removal of the pollutants out of exhaust gasses post-combustion.
A second major theme at the Fuel Flexibility Conference was the morass of conflicting regulations facing anyone burning solid fuel today. For example, the U.S. EPA has a program covering the use of Land Fill Gas (LFG) for generation, but the proposed Minimum Achievable Control Technology (MACT) rules for industrial boilers restrict carbon monoxide, without exempting LFG with its high CO footprint. The installed fleet of coal-fueled plants produces 40 percent of global electricity, and coal combustion will grow at least through 2030 to meet increasing demand, according to EIA forecasts. Thus, since the world will be significantly dependent on solid fuels for the existing installed base for at least the next 50 years, it is imperative that we have regulations that foster burning solid fuels as cleanly as possible. The regulators should allow industry to choose the best alternative between reducing methane as a GHG and an offsetting increase in less polluting CO. We must look for opportunities to utilize clean renewable solid fuels, including biomass, in our existing solid fuel-burning infrastructure.
Conference participants heard presentations on a range of issues facing variations in fuel characteristics, as well as the use of solid biomass fuels. Attempts to co-fire moist low-BTU biomass as a fuel in coal-fueled plants have failed many times. Upon reflection, such attempts seem analogous to introducing leftover paint, solvents or cleaning fluids with combustion value into the gas tank of a car or the tank for a home oil burner. For safety and efficiency reasons, there must be a serious focus on pre-treating solid fuels to meet energy and emission goals.
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