Process integration analysis of a brown coal-fired power station with CO2 capture and storage and lignite drying

Abstract

Abstract Integration of CO2 capture and storage (CCS) into existing and new coal fired power stations is seen as a way of significantly reducing the carbon emissions from stationary sources. A significant proportion of the estimated cost of CCS for post-combustion capture from coal-fired power stations is due to the additional energy expended to capture the CO2 and compress it for transport and storage. The additional energy either reduces the power plant output or creates additional CO2 which will increase the CCS requirements. Therefore, reductions in the overall energy penalty of CCS by improving the efficiency of both the carbon capture processes and the integration of the capture technology with the power plant can lead to significant reductions in the cost of CCS. Pre-drying lignite using low temperature heat sources enables power stations to increase their energy efficiency by the use of low grade heat, providing energy that is less carbon intensive and potentially reducing the cost of electricity production. This work reviews the current thinking for integration of CO2 capture plants using solvent absorption for postcombustion coal fired power stations. It also reviews the integration potential of brown coal dewatering processes to a power plant with CCS. The review uses as a basis a 200MWe(nominal) train of an existing pulverised brown coal fired power plant using heat and process integration techniques such as heat pinch analysis to determine the potential for reductions in capture cost by minimising the energy penalty associated with the addition of the CCS. The study shows that the energy penalty reduces from 39% for a CCS plant with no heat integration to 24% for a plant with effective heat integration. The energy penalty can be further reduced by the addition of pre-drying of the coal. This study shows there is potential to reduce the energy penalty associated with the addition of CCS, however the heat exchanger network and the required modifications to the existing equipment have not been determined and further work identifying these issues is required and these will have a large impact into whether the reductions suggested by this study can be economically implemented.