(320f) Oxy-Coal Combustion in a Pilot-Scale Circulating Fluidized Bed

Oxy-coal combustion to facilitate carbon capture and sequestration is the focus of numerous research and development activities. Recently, Praxair collaborated with the University of Utah to study some of the fundamental impacts of oxy-coal combustion in fluidized bed combustion. An existing circulating fluid bed (CFB) combustor was modified to allow firing with oxygen-enriched recirculated flue gas. Experiments with this facility were able to routinely achieve CO2 concentrations greater 85% (dry basis). Bed temperature and pollutant emissions were measured under both air-firing and oxy-coal firing.

INTRODUCTION

Oxy-coal combustion has received a great deal of attention in recent years as a way to facilitate carbon capture and sequestration (CCS). Many groups have demonstrated the feasibility of using oxygen diluted with recirculated flue gas (RFG) as a replacement for air in pulverized coal (PC) fired boilers. Pilot and full-scale demonstrations of oxygen enriched RFG for PC units are planned or ongoing. Others have published limited experimental data and commercial circulating fluid bed (CFB) boiler design concepts based on oxygen enriched RFG. Praxair has teamed with Foster Wheeler, and others, to propose a 50 MW oxy-coal CFB at Jamestown, NY. Even with this work, there are still details that need to be addressed to optimize the use of oxygen in oxy-coal firing. For example, are there mixing strategies to optimize oxygen use and are there trace species that may create problems for the CO2 purification unit (CPU).

Praxair was involved with some of the earliest oxy-coal combustion studies1 and was the first company to inject oxygen into coal-fired utility boilers15. Praxair has teamed with the University of Utah to explore optimized oxygen use for PC and CFB units. Preliminary data has been collected using oxygen-enriched wet RFG in the L1500 furnace, a 1.5 MW pulverized coal combustor, and will be reported elsewhere. Data has also been collected using the laboratory-scale CFB. These data will be discussed in this presentation.