Carbon dioxide absorption into piperazine promoted potassium carbonate using structured packing
A large-scale pilot plant (0.43 m ID) was extensively modified and converted into an absorber/stripper system to demonstrate CO₂ capture technology using aqueous piperazine promoted potassium carbonate for coalfired power plants. Four pilot plant campaigns were completed. Three campaigns were conducted using 5 m K⁺/2.5 m PZ and 6.4 m K⁺/1.6 m PZ. Flexipac 1Y and Flexipac AQ Style 20 structured packing were used in the absorber. The stripper was tested with 14 sieve trays, IMTP #40 random packing, and Flexipac AQ Style 20 packing. Monoethanolamine (7 m) was tested in the third campaign to establish a base case. An approximate rate analysis showed that 5 m K⁺/2.5 m PZ is two times faster than 7 m MEA and three times faster than 6.4 m K⁺/1.6 m PZ. The location of the temperature bulge moves from the top of the column to bottom as the liquid to gas flow rate ratio is increased. Foaming occurred in the absorber in the first two campaigns and occurred in the stripper in the fourth campaign. Data from the pilot plant was used to develop a K⁺/PZ absorber model in Aspen Plus® RateSep[trademark]. The Hilliard (2005) Aspen Plus® VLE model and the kinetics developed by Cullinane (2005) were incorporated in the model. Data-Fit was simultaneously used to reconcile pilot plant data and perform a regression of the interfacial area and heat loss parameters for the RateSep[trademark] absorber model. The lean loading for the pilot plant data was shifted down by 10% to account for a discrepancy with the Cullinane vapor-liquid equilibrium data. The Data-Fit results showed that the average interfacial area for Flexipac 1Y was 80% of the value measure by the air-water column. The average interfacial area for Flexipac AQ Style 20 for 5 m K⁺/2.5 m PZ was 56% of the air-water measurement. The CO₂ heat of absorption may not have been adequately predicted by the RateSep[trademark] absorber model because the regressed values of heat loss were consistent with forced convection.