Physico-chemical principles of preventing salts crystallization on heat-exchange surfaces

The work discusses physico-chemical grounds of conventional methods for preventing crystallization of salt on heat-exchange surfaces, and dwells upon the role of temperature and supersaturation, as well as the role of the heat-exchange surface as an initiator of calcium carbonate crystallization. The paper provides a brief summary of some methods based on reducing supersaturation of the solution with the salt getting crystallized and on a physical impact upon the solution. Particular consideration is given to a method for preventing calcium carbonate deposits, namely restructurization of the solution as initiated by magneto-hydrodynamic resonance (magnetic treatment). As a criterion for choosing a method of preventing scale formation on the heat-exchange surface, it is suggested that the relative supersaturation with calcium carbonate be taken into consideration. The limitations of and conditions for employment of some methods of preventing scale formation are also presented. The equation of a predictable dependence in increase power consumption by heat-exchange equipment on supersaturation of the solution with calcium carbonate in the surface-adjoining layer is proposed. (C) 2009 Published by Elsevier Ltd.