Simultaneous absorption and desorption with reversible first-order chemical reaction: analytical solution and negative enhancement factors

Abstract

The problem of gas absorption accompanied by a first-order reversible reaction, producing a volatile reaction product, is considered. A general analytical solution is developed for the film model, resulting in explicit relations for the concentration profiles in the film and for the mass transfer enhancement factors. The solution is not restricted to equal diffusivities, and is also applicable to the simultaneous absorption and reversible reaction of two gases. Several limiting cases are derived. It is shown that enhancement factors are possible with values larger than one, but also smaller than one, and even negative. The latter occur in the industrially important absorption of formaldehyde in aqueous solution.