Citation: Cairns, Paul & Clements, Bruce & Anthony, Edward & Macchi, A.. (2011). Combustion of solid fuels in high pressure oxygen environments under different firing scenarios. 28th Annual International Pittsburgh Coal Conference 2011, PCC 2011. 2. 963-977.
Abstract
Oxy-fired combustion has been identified as one of the promising technologies for CO2 capture because it is capable of producing a concentrated CO2 stream suitable for sequestration. The use of pressurized oxy-fired combustion leads to certain advantages including thermal efficiency gains and physical size reduction of the combustor and flue gas treatment equipment. High pressure oxy-fired (HiPrOx) combustion systems have been proposed for use in power generation applications which fire coal with either a wet or dry flue gas recycle stream as a method for temperature moderation. HiPrOx has also been proposed for direct contact steam generation (DCSG) for use in industrial applications such as heavy oil extraction with solid fuels such as petroleum coke or asphaltenes. These firing scenarios present unique operating conditions and chemical species concentrations that affect the combustion characteristics of solid fuel chars. TGA experiments were performed to study the effects of steam on a Canadian high-volatile bituminous coal char’s reactivity in an oxy-fuel (O2/CO2/H 2O) environment. It was found that under kinetically controlled conditions, the increased addition of steam led to a reduction in burning time and temperature. The findings may have resulted from the lower heat capacity and higher thermal conductivity of steam compared to CO2. These results differed from the lower gas temperatures observed near the burner of a pilot scale plant using a wet primary gas recycle in another study. It was postulated that, the suppression of H radical concentrations resulting from the presence of H2O and CO2 during homogeneous ignition may have a greater affect on combustion temperature than the higher thermal conductivity and lower heat capacity of H2O present in the environments investigated in this study.