Petroleum Coke as a Supplementary Fuel for Cyclone Boilers: Characteristics and Test Results

Petroleum coke is periodically tested and used as a supplementary fuel for cyclone boilers. Its high heat content and low cost make it an attractive fuel for power generation. In cyclone boiler firing, it also has environmental advantages. While it is high in sulfur content, it can be used to reduce NO_x emissions along with such trace metal emissions as mercury and arsenic. Successful firing of petroleum coke in cyclone boilers, however, requires considerable attention to fuel properties of the coal and the opportunity fuel including fuel structure and reactivity, and ash chemistries. This paper reviews selected properties of petroleum coke including traditional analyses plus structural characterization using ¹³Carbon Nuclear Magnetic Resonance (NMR), drop tube reactor (DTR) characterization for kinetics and volatility evaluation, and thermogravimetric analysis (TGA) for char oxidation kinetics. The paper then summarizes results of petroleum coke firing at the Paradise Fossil Plant of TVA, and Bailly Generating Station of Northern Indiana Public Service Company (NIPSCO). Results presented include impacts of cofiring on boiler efficiency, NO_x emissions, and the fate of selected trace metals including arsenic, mercury, nickel, and vanadium. It documents the overall benefits and issues associated with cofiring petroleum coke with coal in cyclone boilers as a significant opportunity fuel.