Fuel blending and switching has become the norm in response to regulatory and market forces, but many older boilers were designed for a particular fuel. Understanding the effects of different fuels on combustion system metals is crucial for ensuring smooth operations.

Is there a clear distinction between good and bad fuel to burn in a particular boiler? Apparently not! Some fuels may contain higher heating values, but they may also possess characteristics that cause emissions problems, as well as operational and reliability challenges. Other fuels may be more environmentally friendly, but may contain higher moisture content and lower heating values. Ideally, the “right fuel” is that for which a boiler is designed or retrofitted to specifically burn.

Congress extensively amended the Clean Air Act in 1990. Following those changes, the Environmental Protection Agency began imposing more stringent emissions regulations in the mid-1990s, which led to fuel blending and switching becoming the norm. Of course, there are other factors—such as cost, availability of mines, and meeting full-load requirements in a dynamic environment—that have also influenced fuel blending or switching decisions.…

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