Optimized post combustion carbon capturing on coal fired power plants

Abstract

Abstract Worldwide coal contributes to over 40% of the electricity generation today and its share is expected to increase steadily over the coming decades. The continued dominance of coal in global energy structure and the growing concern of climate change necessitate accelerated development and deployment of new technologies for clean and efficient coal utilization. Coal fired power plants with CO 2 capture and sequestration (CCS) are widely expected to be an important part of a sensible future technology portfolio to achieve overall global CO 2 reductions required for stabilizing atmospheric CO 2 concentration and stopping global warming. Within the last decades the efficiency of coal fired power plants was significantly raised by different technical steps as running the steam generator on higher temperatures and pressures. So an efficiency (based on LHV) of higher than 45% for hard coal and 43% for lignite coal are more or less the technical standard for modern supercritical coal fired power plants. The amine scrubbing carbon capturing technology, which is planed to be added for fossil fuel fired power stations, will raise the self consumption of the plant and so lower the efficiency drastically. To minimize this effect it is necessary not only to find solvents with a small heat duty for the carbon dioxide scrubbing process, but also to optimize the heat re-integration to the water steam cycle and reduce the electrical self consumption of the scrubbing plant. This can be successfully designed with a detailed review of all key components as the turbine, LP–and HP–preheaters, the steam generator, the flue gas cleaning systems including CO 2 scrubbing equipment and the cooling system of the plant. By improving the internal heat recovery in the power station the efficiency penalty of carbon capture (including the compression) can be reduced to values of 8 percentage points instead of 12 or more percentage points for systems without heat recovery and turbine modifications. This optimization is shown for different stages of heat reintegration from the CO 2 -compression unit, CO 2 capture unit to the water-steam and flue gas side of the power station. Hardware modifications of components like the steam turbine are as well discussed as the additional components to be inserted in the boiler and water-steam cycle. As a global technology and equipment provider for complete thermal power plants, Hitachi has the knowledge and capability to address the above challenges of CCS.