Insight into the bubble column evaporator and its applications

Abstract

This paper presents a review of the bubble column evaporator (BCE) and its many novel applications. The BCE process offers a continuously produced source of high air–water interface and consequently provides high overall heat and mass transfer coefficients. Although the bubbling process itself is both simple to use and apply, our understanding of the fundamental physical and chemical principles involved is surprisingly limited and there are many issues yet to be explained. Recently the process has been used to develop new methods for the precise determination of enthalpies of vaporisation (ΔHvap) of concentrated salt solutions, as an evaporative cooling system, a sub-boiling thermal desalination unit, for sub-boiling thermal sterilisation, for low temperature thermal decomposition of different solutes in aqueous solution and for the inhibition of particle precipitation in supersaturated solutions. These novel applications can be very useful in many industrial practices, such as desalination, water/waste water treatment, thermolysis of ammonium bicarbonate (NH4HCO3) for the regeneration in forward osmosis and refrigeration related industries. The background theories and models used to explain the BCE process are also reviewed and this fundamental knowledge is applied to the design of BCE systems and to explain recently explored applications, as well as potential improvements. Many other prospective applications of the BCE process are also reported in this paper.