Analysis of the Flue Gas Preparation Process for the Purposes of Carbon Dioxide Separation Using the Adsorption Methods

The necessity of limitation of carbon dioxide emissions, which also concerns the energy sector, causes that more and more effective and efficient methods of CO₂ capture from the flue gas are being tested. Among these technologies are adsorption ones, which have been used for a gas separation for many years. The characteristic features of adsorption separation are: long life of the sorbents used, low energy expenditure, and minim effect on the environment; however, their application requires adequate initial preparation of the flue gas fed into the system of CO₂ separation so that the flue gas temperature is as low as possible, and there is no water content in it. The study presents the concept and numerical calculations of the system for preparation of the flue gas feeding the CO₂ adsorption (vacuum pressure swing adsorption (VPSA)) separation unit, using the absorption chiller (AC). In the presented concept, the AC is driven by the flue gas which is used as both: upper and lower heat source for AC; however, due to the amount of energy being carried out with the flue gas, which is larger than required by the AC, the additional heat exchangers must be implemented. The calculations presented in the study show that owing to the application of AC, flue gas may be cooled down to temperatures even about 5 °C. Moreover, the simultaneous process of flue gas cooling and drying in such system is realized at low energy expenditure which leads to improvement of the overall energy efficiency of the system of CO₂ separation from flue gas and also to reduction of its dimensions.