Ecological principles of wet-process phosphoric acid technology

Based upon fundamental results obtained for phosphate rock dissolution and calcium sulphate crystallization, the behaviour of both substances inside industrial reactors of wet-process phosphoric acid (WPPA) production is described. This approach results in some new ideas for the ecological production of WPPA. The main feature requires separation of the phosphate rock dissolution from the calcium sulphate crystallization stage. As a result, the optimal chemical, i.e. the acidity level for the dissolution and supersaturation value for crystallization, and hydrodynamic, i.e. high agitation intensity for the dissolution and slow agitation intensity for the crystallization, conditions could be provided. A brief technological scheme for ecologically clean WPPA production technology is also proposed. (C) 1998 SCI.