Studies on Bubble Column Evaporation in Various Salt Solutions

Abstract

The physical properties of concentrated salt solutions are an important aspect of many industrial processes. The effects of different salts on the inhibition of bubble coalescence have raised some unexpected observations, because some salts inhibit coalescence while others have no effect over a wide concentration range. Fortunately, many common salts inhibit bubble coalescence and although the mechanism is not fully understood, this effect allows the construction of bubble column evaporators (BCEs) for the efficient transfer of both vapor and heat. In this study the BCE process has been used under steady state conditions to determine the latent heat (enthalpy) of vaporization (ΔH vap) of concentrated solutions of several common salts. In addition, it was found that under non-steady state conditions using high inlet gas temperatures, the rate of vapor transfer, and hence thermal desalination, could be increased using the BCE process. Some new observations on the fundamental mechanism of the bubble coalescence phenomenon are also reported.