Calculation of an advanced ultra-supercritical power unit with CO2 capture installation

An efficiency enhancement of coal-fired power units becomes a basis for the reduction in the consumption of primary fuels and as a result in CO2 emissions. Steam parameters increasing is an effective way to improve the efficiency of electricity generation. The progress in materials engineering has led to the more and more common implementation of the technology of power units for ultra-supercritical parameters. The next generation of this technology - the advanced ultra-supercritical parameters A-USC - opens new perspectives. Obtaining a higher efficiency of electricity generation and exceeding the 50% net efficiency barrier, apart from the increase in the steam parameters, requires an optimisation of the thermodynamic cycle, together with the modernisation of the flow system of steam, condensers, regenerative water heaters. The development of the advanced ultra-supercritical technologies is the subject of European, Japanese, American and Chinese projects, which aims at the completion of a power unit with the live steam parameters of 700 °C and 35 MPa and the net efficiency exceeding 50%. The paper presents the results of the calculations which were performed for a conceptual power unit in two configurations - with single and double steam reheat. The CCS Directive contains a clause providing for the new construction of power installations as “capture ready”. Newly built power unit gives possibility of optimized integration with CO2 capture installation. The power and efficiency loss related with the integration with CO2 capture process can be reduce. Due to the state of knowledge of CO2 capture methods and the ability of its application into the high power unit only the chemical absorption was considered in the paper. The CO2 capture installation requires large amount of heat to solvent regeneration in appropriate quantity and quality, cooling system to discharge waste heat and power to drive CO2 compressor and auxiliary equipment (pump, fans). In the paper the steam to CCU is extracted from IP/LP crossover pipe. The design IP/LP crossover pressure has very significant impact on the power unit efficiency. Its reduction to the level which is required by the CCU can improve power unit efficiency. However, lower crossover pressure results in efficiency looses in part-load operation. Therefore, the analysis of power unit operation with partial load for various design crossover pressure was considered. The slight improvement of power unit efficiency can be gained also through the recovery of waste heat from the overhead condenser and CO2 compressor intercoolers in the feed water preheating system.