Steam regeneration of PEI impregnated silica sorbents for post-combustion CO_2 capture: preliminary results

摘要

Extensive research work is under progress in the field of post-combustion CO_2 capture from flue gas, focusing on design of new, cost-effective and selective adsorbents and adsorption technologies. Recently, a lot has been mentioned in literature on using steam stripping for capturing CO_2 from flue gas and the ease of recovery of CO_2 by condensing the moisture. But very little data is available on suitability of steam for multi-cyclic CO_2 adsorption study. Previous work on suitability of amine based solid adsorbents for CO_2 capture using an inert gas for the regeneration step has been carried out in our research group. The primary focus of the current work is to study CO_2 regeneration using steam stripping. Commercial silica support (Fuji Silysia Cariact Grade Q-10, particle size 75-150 μm) was impregnated with low molecular weight Polyethyleneimine (PEI) (Sigma Aldrich, Mn-600), using wet impregnation technique. CO_2 adsorption-desorption cyclic study was conducted in a lab-scale packed bed reactor. The reactor was a 1/2 inch stainless steel tube with a frit to hold the sample. All the connecting lines were heated to prevent condensation of steam. 1g of sorbent was fed at a time. The effluent gas composition from reactor was analyzed with a Pfieffer Mass spectrometer (Omnistar GSD 320). Firstly, the sample was heated to 110°C and purged with 100 cc/min N_2 to remove any CO_2 and moisture adsorbed in the sample. The sorbent was then cooled down to 75°C (adsorption temperature). After the temperature stabilized, 100 cc/min. of gas (10% CO_2 balanced with N_2 (henceforth mentioned as flue gas)) was passed through the reactor. Adsorption was carried out for 10 min. After this the temperature of reactor was ramped up to 110°C. At this point, the sorbent was stripped of CO_2 using a mixture of 90% H_2O and 10% N_2 (henceforth mentioned as steam). N_2 was added as a reference gas in the MS. Steam stripping was carried out for 10 min, followed by drying of sample at 110°C using N_2 and then cooling to 75°C for the next cycle. A set of 20 cycles was performed in this way. A K-type thermocouple was used to record the temperature profile in the sample during adsorption and desorption.