TWO-STAGE RECRYSTALLIZATION WITH THE REGENERATION OF THE SOLVENT

In this paper we propose an option of an energy-saving scheme for the two-stage recrystallization of substances from aqueous solutions with regeneration of the solvent from the final solutions by evaporation using a closed-type heat pump and recuperative heat exchange between the mass flows. Theoretical equations describing this process were derived. On the basis of these dependences we carried out analysis of the impact of some parameters on potassium nitrate recrystallization from aqueous solutions. It was found that the regeneration of the solvent from the final solutions allows reducing significantly the consumption of fresh solvent for the purification process. It was shown that the use of heat pumps at the stage of the solvent extraction from the final solutions combined with recuperative heat exchange between the mass flows is energetically most advantageous in most technological regimes. This is confirmed by high values of the energy conversion coefficient and low values (<1) of relative consumption of reference fuel. It was found that an additional stage of the product crystallization of from the evaporated solution allows increasing the output of refined products almost by a factor of 1.3. This has a positive effect on the technical and economic indicators of the purification process.

purification of substances, crystallization, heat pumps, power consumption, solvent regeneration, recuperative heat exchange

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