Pulverized-Coal Deposits Collected Under Staged and Unstaged Oxy-Fuel Conditions for Four U.S. Coals

Abstract

Coal ash deposits were collected in a 160 kW_th, down-fired oxy-coal reactor under staged and unstaged conditions for four different coals at two locations. The deposits were embedded in epoxy for imaging and element composition analysis using scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). Particles were found to be categorized into four groups: non-porous non-molten mineral matter, unburned coal/char, porous non-molten mineral matter, and molten mineral matter. Near burner deposits on the upstream side of tubes in cross-flow contained all four types of particles. Downstream deposits contained primarily molten mineral matter, approximately an order of magnitude smaller in size. No measureable chlorine (greater than 1%) was found in the deposits. Sulfur was observed to correlate with coal calcium content in oxidizing regions. The only major difference between the air and oxy-combustion deposits measured previously was the sulfur concentration; deposits collected with oxy-combustion contained higher concentrations of sulfur.

Keywords:

• Coal
• Deposition
• Oxy-combustion
• Ultra-supercritical

ACKNOWLEDGMENTS

This material is based upon work supported by the U.S. Department of Energy under award number DE-FG26-01NT41175, the Ohio Coal Development Office under award number D-00-20, and the Babcock & Wilcox Company Power Generation Group. The work was initiated and managed by Steven C. Kung of the Babcock & Wilcox Company. His advice and guidance was much appreciated.