Robert Zarzycki

Analysis of the flue gas preparation process for the purposes of carbon dioxide separation using the adsorption methods

Extensive research has been done in recent years to limit CO2 emissions from the processes of coal fuels combustion in the energy sector to the atmosphere. New oxy-fuel combustion technologies and several methods of CO2 emissions have been developed based on these studies. One of them is the methodology of vacuum pressure swing adsorption (VPSA). In the VPSA technology, processes of adsorption and desorption are ensured by changes in pressure. The effectiveness of this method largely depends on properties of sorbent and its sorption ability with respect to CO2. The parameters which affect sorption capacity are temperature of flue gas and its pressure. In the case of sorbents used, sorption capacity increases as flue gas temperature is reduced and its pressure is higher. In this case, it is possible to limit the dimensions of the adsorption unit and costs of initial process of flue gas compression. This study presents the proposal for the technology of preparation of furnace flue gas for the VPSA process, assuming minimization of energy costs of the process and demand for sorbent. The proposed technology assumes initial cooling of flue gas that leaves the boiler in dedicated heat exchangers, where flue gas is cooled and the condensation of water from flue gas is obtained. The waste heat obtained in this way can be used in the steam power unit e.g. to heat the condensate or power the adsorption cooling system that generates chilled water. The chilled water obtained in the system that is supplied to heat exchangers allows for a more efficient flue gas cooling, reduction in heat exchanger dimensions and obtaining flue gas with lower content of humidity and lower temperature, which is advantageous due to the process of CO2 separation. The study presents an analysis of the impact of preparation process parameters on dimensions of heat exchangers and demand for sorbent. The simulation calculations were used to evaluate demand for energy for initial process of flue gas compression before the VPSA unit and minimal demand for sorbent for CO2 separation from the flue gas stream flowing through the adsorber for specific dimensions of the heat exchanger. The results obtained in the study can be used for economic analyses of flue gas preparation installation and evaluation of unit costs of CO2 separation from flue gas aimed at determination of optimal parameters of the CO2 separation process.