Towards Second Generation Oxy-pulverized Coal Power Plants: Energy Penalty Reduction Potential of Pressurized Oxy-combustion Systems
Résumé
During the last decade, CO2 capture on coal power plants has been the subject of sustained attention as one of the most credible way to drastically reduce anthropogenic greenhouse gas emissions. Significant reduction in the energy penalty related to the oxy- combustion routes has been achieved but uncertainties remain in the operation of such a process inducing major modifications of the power island. In this context, for oxy-combustion, and more generally carbon capture to become a reality, its energy penalty shall be drastically reduced. In that perspective, cutting edge strategies allowing taking full advantage of oxy-fired operation have to be investigated. Among them, boiler pressurization has been identified as one of the most promising solution. Two major pressurized oxy-combustion concepts have emerged in literature: the flameless combustion technology (ISOTHERM®) and the staged-pressurized oxy-combustion (SPOC) concept. According to the authors describing those two processes, whilst very different in the combustion temperature control strategy, they both succeed in allowing pressurized operation.
In this work, those two concepts have been compared to an air-fired, a conservative and optimized atmospheric oxy-fired power plants in terms of energy performances. The reason underlying below the observed differences, have been determined using exergy analysis. The SPOC process leads to significantly lower energy penalty, as low as 3.8%-pts compared to the ISOTHERM® concepts which lead to performance in the same order of magnitude than the optimized atmospheric design. It has been highlighted that this difference is essentially due to the large flue gas recycling requirement for the latter concept to control combustion temperature.