Retrofit of CO_2 capture at coal- and gas-fired power plants

摘要

The Dutch government and the power production companies have agreed to reduce the emissions of CO_2 from coal-fired power plants by applying co-firing of biomass. In the long term, additional measures such as the capture of CO_2 must be taken to achieve the emission targets. KEMA has performed a baseline study in which a number of CO_2 capture processes have been evaluated. The focus for the short term will be on existing power plants with retrofit of CO_2 capture. A 600 MWe pulverized coal-fired (PC) power plant and a 350 MWe gas-fired combined cycle (CC) power plant have been defined as reference plants. For the reference plants, process and economic calculations are performed for the original plant and the retrofitted plant with CO_2 capture based on available and proven technology. As a technology option, post combustion capture by absorption of CO_2 with solvents like MEA is considered. The energy consumption of the capture process and the compression of CO_2 to 110 bar is compared for the coal-fired and the gas-fired combined cycle plant. The energy penalty for CO_2 capture in a coal-fired power plant is much higher than in a combined cycle while the amount of CO_2 per kWh of a coal-fired power plant is twice the CO_2 emission of a combined cycle plant. However, the cost of avoided CO_2 is lower for the coal-fired power plant (33 EUR/t CO_2 for PC and 44 EUR/t CO_2 for CC). Special attention is given to the consequences of retrofit CO_2 capture at coal-fired power plants. This includes the need for a large amount of steam for the regeneration of the solvents and the consequences of this for the steam process, flexibility to operate the retrofitted power plant, space needed to locate the absorber, regenerator, CO_2 compressor station and eventually additional cooling towers, and extra heat disposal to the environment. For retrofit of post-combustion CO_2 capture technology at existing power plants, it is essential to decrease the energy consumption of the capture process. The lower energy consumption will reduce the limitations for retrofit such as the additional heat disposal via cooling water, and space requirements. This paper presents the results of the baseline study and future perspectives.