Multistage Countercurrent Crystallization for the Separation of Solid Solutions

Abstract

While one crystallization step can be sufficient to provide pure components in case of eutectic systems, multistage operation is required to resolve solid solutions. A recently published equilibrium stage model was adopted here and generalized to simplify the description of the corresponding solid‐liquid equilibrium (SLE). The equilibria of the system potassium sulfate/ammonium sulfate/water were studied at different temperatures. The existence of a controversially discussed miscibility gap below 25 °C could not be confirmed. Using the equilibrium stage model and the studied specific SLE data, process variants considering different evaporation strategies were simulated.

Exploiting Ternary Solubility Phase Diagrams for Resolution of Enantiomers: An Instructive Example

“…Main emphasis is laid on illustration and understanding of the relations in the phase diagram which are required for separation process design. The fundamental mass balances necessary for quantitative exploitation of the phase diagrams are not addressed in detail but are focus of other related works [23][24][25]. Both separation strategies will be illustrated on a couple of experiments leading to different separation results.…”

Global optimization of multistage binary separation networks

“…Crystallization unit. The model for the crystallization unit from [8] adapted for steady-state operation is written in terms of the primary component A, the solvent S and all components without solvent AB, with according index i = A, AB, S. Quantities at the end of step 1, i. e. mixing of feed ows, for the process illustrated in Figure 7 are calculated from the unit feed as…”

“…(2) S,n for step 2, i. e. dissolving all solid in the feed, is determined via the phase equilibrium. The phase equilibrium is given in [8] by polynomial ts to experimental data using mass fractions in the feed mass ow x i,n and in the virtual solid phase y i,n . The ows for non-solvent components are the same between step 1 and step 2, so L…”

“…Countercurrent cascades are deployed for a range of industrially relevant separation processes [1], including cooling crystallization cascades [2,3,4,5], evaporative crystallization cascades [6,7,8,9], organic solvent nanoltration cascades [10,11], and reverse osmosis cascades [12,13,14,15].…”

Generalizing Countercurrent Processes: Distillation and Beyond

“…Solid feed is added to stage j F , while products leave the cascade at the top and the bottom via stages 1 and N S . More details about the process can be found in . The process design is difficult due to the complex ternary phase equilibria and the challenging solid phase transport.…”