CO 2 absorption by aqueous NH 3 at low temperature is a complex chemisorption process that can convert captured carbon to ammonium bicarbonate. The process has been investigated by several pilot plant studies, however its design for a particular industrial case still relies on process modelling. In this work, the rate-based model for CO 2 absorption in aq. NH 3 was initially assessed for its fidelity to predict vapour-liquid equilibrium and pilot plant data; and consequently, the model was applied to simulate an industrial flowsheet to investigate the effect of column size, operating flow rates, and operating column pressure on CO 2 loading (mol CO 2 /mol NH 3 ) in the product stream, ammonia slip and carbon capture efficiency. The e-NRTL-RK or e-NRTL with modified binary interaction parameters provided reasonable agreement with the vapour-liquid equilibrium data. Further, the mass transfer correlation of Onda et al. (1968), mass transfer condition parameters of 1 and reaction condition parameter of 0 provided predictions for the Munmorah pilot plant data with less than 10% discrepancy. In industrial flowsheet simulations, an increase in column packing height (from 9 m to 22 m) or diameter (from 1.8 to 3.2 m) was able to increase the CO 2 loading to 0.63 and capture efficiency to 77%. Further increases in packing height and/or column diameter did not produce a higher CO 2 loading, inferring the system had reached thermodynamic limitations. Increased operating pressure from 1 to 5 bar was able to further raise the CO 2 loading to 0.71 and capture efficiency to 87%. • Rate-based model used to simulate industrial CO 2 absorption in aqueous NH 3 . • Modified-e-NRTL with Onda model best matched experimental results. • Increasing column size improved CO 2 capture, up to equilibrium limits. • Higher pressure boosted capture and product loading; NH 3 slip stayed low.
Stojanovski et al. (Sun,) studied this question.