Scaling-Up Eutectic Freeze Crystallization

Doctoral thesis (2008)

Authors

Contributors

G.J. Witkamp (promotor)

Faculty

Mechanical Maritime and Materials Engineering (Mechanical Maritime and Materials Engineering) (TU Delft)

Mineral Interface Scale-up Irreversible thermodynamics Thermogravimetric analysis Non-equilibrium thermodynamics Waste water treatment Crystallization Eutectic freeze crystallization Magnesium sulfate Mgso4.11h2o Meridianiite Inline supersaturation determination Inline conductivity measurement Inline refractive index measurement Epsomite Xrd X-ray diffraction Negative crystal Micro raman spectroscopy Antarctic ice Saroma lake Sea ice Coupled heat and mass transfer Onsager relations Crystal growth on a cold surface Cyclic innovation model Cim Cooled disc column crystallizer Cdcc Skid mounted unit Aqueous process stream treatment Tga

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Published Date

21-01-2008

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Faculty

Mechanical Maritime and Materials Engineering

Abstract

A novel crystallization technology, Eutectic Freeze Crystallization (EFC) has been investigated and further developed in this thesis work. EFC operates around the eutectic temperature and composition of aqueous solutions and can be used for recovery of (valuable) dissolved salts (and/or or acids) and water from a wide variety of aqueous process streams. Using EFC, processes producing large quantities of saline solutions could be carried out in an ecologically and economically attractive way. An introduction and a brief summary of earlier work are given in Chapter 1. The experimental study on pilot scale Cooled Disc Column Crystallizer (CDCC-2) designed for continuous EFC operation is presented in Chapter 2. CDCC-2 was tested for an industrial MgSO4 stream and evaluated in terms of heat transfer, ice and salt sizes, production and growth rates. Application of conductivity and refractive index measurement techniques for inline concentration and supersaturation measurements of MgSO4 solution was studied in Chapter 3. Chapter 4 presents the CDCC-3 and Skid Mounted Unit, designed and constructed for 130 ton/year MgSO4.7H2O and water production capacities. MgSO4 salt crystal structure at eutectic conditions was studied and reported in Chapter 5. The MgSO4 crystal hydrate formed below approximately 0 oC was proven to be MgSO4.11H2O instead of the common reported MgSO4.12H2O. Crystal structure analysis and the molecular arrangement of these crystals were determined using single crystal X-ray diffraction. Raman spectroscopy was used for characterizing MgSO4.11H2O and for comparing the vibrational spectra with MgSO4.7H2O. Thermo gravimetric analysis confirmed the stochiometry of MgSO4.11H2O. Additionally the Miller indices of the major faces of MgSO4.11H2O crystals were defined. Chapter 6 covers the discovery of the natural occurrence of the MgSO4.11H2O new mineral -Meridianiite- as salt inclusions in sea ice from Saroma Lake-Japan and in Antarctic ice. In Chapter 7 nucleation and crystal growth of MgSO4 aqueous solution on a cooled surface were studied theoretically and experimentally. Coupled heat and mass flux equations from non-equilibrium thermodynamics (Onsager theory with reciprocal relations) were defined for crystal growth and the temperature jump at the interface of the growing crystal. Chapter 8 aims to describe the Cyclic Innovation Model (CIM) and to set a path for commercialization of the EFC technology.

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