Conventional spray towers emit absorbent droplets that are nonuniform in size and spatial distribution; as a result, capture efficiency is degraded. This paper presents the design and evaluation of a novel spray tower for capturing CO2 with much increased capture efficiency. The tower uses a multinozzle plate, and can spray sorbent drops of almost the same size vertically and quite uniformly across the flow cross section. Uniform size and spatial distribution of droplets greatly increased the capture efficiency η, although much bigger drops were used, achieving η ∼ 95%, which has rarely been reported to date for CO2 capture by a spray tower. Experimental results were compared with the predictions by numerical simulations in excellent agreement. The new spray tower has a number of strong points that are favorable for scaling up of diameter and length.

Chemical absorption of CO2 with aqueous NH3 was numerically analyzed in an Eulerian manner for steady 1D spray towers in which gas velocity and liquid flow were uniform, and the results were formulated into a universal correlation. The capture efficiency η predicted by the proposed correlation is a sort of upper bound, and can be used as a base to evaluate the optimality of each design. Drop-size poly dispersity was considered; a spray of poly dispersed droplets was found to be equivalent in η to a spray of monodispersed droplets of an equivalent diameter, and a general formula for the equivalent size was attained in terms of mean size and geometric standard deviation. Total mass transfer coefficient was linearly proportional to the gas–liquid flow rate ratio, and the efficiency correlation agreed well with published results.