Treatment of Spent Cation Exchange Regenerant with Eutectic Freeze Crystallization. Feasibility Study for Demin Water Plant Botlek

The goal of the study was to determine the technical and economic feasibility of Eutectic Freeze crystallisation (EFC) to treat the spent cation exchange (CIEX) regenerant at demin water plant Botlek (DWP Botlek). DWP Botlek is the largest demineralised water production plant in the Netherlands that applies CIEX for hardness removal from its source water. For the technical assessment, a semi-industrial EFC pilot plant was installed at DWP Botlek and series of pilot tests were performed to study the EFC process performance. The pilot tests were performed in two phases, phase 1 involved the operation of the pilot unit in
discontinuous mode (few hours each day) and phase 2 involved operation of the pilot unit in continuously mode (multiple days). In phase 1 the crystalliser was fed sequentially with two types of start solutions: (i) synthetic saline solution that contained approximately 20 wt% NaCl in the spent CIEX regenerant of DWP Botlek and (ii) start solution that contained multiple salts (4.9 wt%, NaCl, 12.6 wt% CaCl2 and 3.2 wt% MgCl2). In phase 2 only the multicomponent start solution that contained 4.9 wt%, NaCl, 12.6 wt% CaCl2 and 3.2 wt% MgCl2 was used. The main purpose of the pilot tests was to determine the influence of key
variables on heat transfer and the quality of products, and eventually to achieve steady state operation.