Modeling and analysis of the selected carbon dioxide capture methods in IGCC systems

Carbon dioxide capture from energy systems, as a result of imposed by European Union regulations, can in the future become a necessity. The biggest disadvantage of the existing methods of CO₂ separation is high energy intensity of the process, which causes significant degradation of the efficiency of electricity production by even ten percentage points. Thus, it is important to look for such methods of CO₂ capture, that will allow to decrease energy intensity of such processes. One of the electricity generation systems that is termed prospective in the context of "zeroemission" (thus, coupled with CCS installation) technology is Integrated Gasification Combined Cycle (IGCC) system. Here, carbon dioxide capture process is conducted before combustion, what significantly facilitates CO₂ separation. In this paper two methods of carbon dioxide capture from the process gas are compared. First is at present the most frequently considered CO₂ capture method, i.e. chemical absorption, second is termed as having a big potential of development, i.e. membrane CO₂ separation. In order to conduct the analysis proper models of CO₂ capture installations were built in Aspen Plus software. Selected methods were compared mainly with respect to energy intensity of the processes but also taking into account the possibility of development and accessibility of both of these methods. The results of analysis show, that the use of membranes allows for a significant decrease of energy intensity of a capture process (by even more than 15 times) in comparison to the absorption process, however, the purity of separated CO₂ significantly depends on the type of membrane, membrane surface and process parameters, and not always the required high purity of this gas can be obtained. Nevertheless, the development of membrane techniques allows to predict, that this technology will be competitive in the future as regards effectiveness and cost to other methods of separation.