Oxyfuel Process for Hard Coal Power Plants with CO_2-Removal

摘要

The removal of CO_2 from the flue gases of conventional hard coal power stations, where volumetric concentrations of about 15 % are reached, imposes very high energy demands. The Oxyfuel process proposes to increase the CO_2 concentration in the flue gas by burning coal with pure oxygen instead of air. An upstream cryogenic Air Separation Unit provides the required oxygen. To reduce temperatures in the boiler, flue gas is recycled. Here, various configurations for the location of the recycle branching within the flue gas treatment are possible. With Oxyfuel combustion it is possible to achieve CO_2 concentrations of above 90% in the dry flue gas and the liquefaction of the exhaust gas now can be managed with a lower energy input. Taking into account that a direct compression of the exhaust gas would result in high impurities in the CO_2 stream, one has to study alternative options. The research at the Hamburg University of Technology (TUHH) investigates the cryogenic separation of the flue gas, leading to a relatively pure CO_2 stream, which will supposedly not interfere with the geologic formations where it is to be stored. Therefore, the Oxyfuel process represents an attractive technology for relatively efficient removal of the CO_2 from the flue gas of fossil fuel combustion plants and preparing it for sequestration.