CO2 capture from gases by using hollow-fiber membrane contactor

Abstract

The aim of this thesis was to examine the efficiency of CO2 capture by means of hollow-fiber membranes using potassium glycinate as the absorbent. The literature part presents the background for the thesis, conventional methods of CO2 capture technology for understanding the process principle. Membrane equipment, existing contactors and relevant problems are provided for reviewing the possible technological risks. Applications of membrane technology are presented to help to understand the maturity of technology. The experimental part of the work was conducted using a continuously operated pilot CO2 capture unit. The experimental part is divided into two parts, starting from baseline laboratory experiments to examine the basic parameters of hollow-fiber membrane module and potassium glycinate absorbent in absorption – desorption processes. Next, the process was supplemented with vacuum pump and ultrasound bath to investigate the influence of vacuum and ultrasound on the desorption process. The CO2 flux, capture efficiency, overall mass transfer coefficient and energy consumption were obtained as the main results of data analysis. The results show the dominant influence of desorption temperature and vacuum pressure on the process performance. According to the results the highest CO2 recovery efficiency of 94.24% was achieved at liquid desorption temperature of 80 °C and 500 mbar vacuum pressure. The largest CO2 molar flux and mass transfer coefficients are found 2.36 10–4 mol/m2s and 1.8 10–4 m/s respectively. Purity of CO2 in the product stream varied within 90% - 95% due to impurities in the CO2 inlet gas stream. The lowest heater energy consumption of 4602 kJ/mol with maintaining the high efficiency was obtained at the lowest vacuum pressure of 500 mbar.