| Summary: |
The purpose of this project is to study the phenomena of impurity transfer into crystals in industrial crystallization processes. Analyses techniques for several impurities, namely high molecular weight (HMW) compounds, will be developed and employed, as well as a new model that allows to quantify the transfer of impurities into the crystals. The case study will be the crystallization of sucrose.
The presence of impurities in crystallization processes has been the subject of much work. The impurities, whose origin can be the raw materials or be created during the manufacturing processes, can affect the properties of solutions (viscosity, for example), which will affect in turn the several process operations namely crystallization, either modifying the crystal habit, the nucleation, growth and agglomeration kinetics, or migrating to the crystals affecting its purity, viz the product quality. In the case of sugar, there are several compounds that can affect its production process and the quality of the product. Some are inorganic, like calcium and potassium, while other are organic, namely high molecular weight (HMW) compounds. These compounds can be originated from sugar cane, as starch, or can be formed during sugar extraction or refining. It is important to find a better understanding of the mechanism involved in migration of these compounds into sugar crystals. It will be important to know the characteristics that influence this affinity, as well as to model and quantify the transfer process.
The two most significant innovation of this work comprise: the study of the physico-chemical characteristics of the compounds that influence its affinity to the sucrose crystal, implying the development of techniques suitable to its separation and characterization; and the development of a model to allow for a better understanding and quantification of the transfer of impurities into the crystals. This will allow, together with the already known nucleation, growth and ag  |
Summary
The purpose of this project is to study the phenomena of impurity transfer into crystals in industrial crystallization processes. Analyses techniques for several impurities, namely high molecular weight (HMW) compounds, will be developed and employed, as well as a new model that allows to quantify the transfer of impurities into the crystals. The case study will be the crystallization of sucrose.
The presence of impurities in crystallization processes has been the subject of much work. The impurities, whose origin can be the raw materials or be created during the manufacturing processes, can affect the properties of solutions (viscosity, for example), which will affect in turn the several process operations namely crystallization, either modifying the crystal habit, the nucleation, growth and agglomeration kinetics, or migrating to the crystals affecting its purity, viz the product quality. In the case of sugar, there are several compounds that can affect its production process and the quality of the product. Some are inorganic, like calcium and potassium, while other are organic, namely high molecular weight (HMW) compounds. These compounds can be originated from sugar cane, as starch, or can be formed during sugar extraction or refining. It is important to find a better understanding of the mechanism involved in migration of these compounds into sugar crystals. It will be important to know the characteristics that influence this affinity, as well as to model and quantify the transfer process.
The two most significant innovation of this work comprise: the study of the physico-chemical characteristics of the compounds that influence its affinity to the sucrose crystal, implying the development of techniques suitable to its separation and characterization; and the development of a model to allow for a better understanding and quantification of the transfer of impurities into the crystals. This will allow, together with the already known nucleation, growth and agglomeration processes, a better awareness and modelling of the crystallization process, which is an essential condition for the optimization of the production and of final product quality. |