Sucrose crystal growth rate in process of cooling crystalization. Doctoral dissertation | Brzina rasta kristala saharoze u postupku kristalizacije hlađenjem. Doktorska disertacija
2009
Grbić, J.
This thesis presents the study of sucrose cooling crystalization under laboratory conditions from model sucrose solutions and model sucrose solutions in the presence of sodium acetate or calcium acetate. The influence of acetate salts on sucrose crystal growth rate, size and uniformity of crystals and quantity of crystallized sucrose were examined. The sucrose crystal growth rate was determined as crystal mass growth rate and linear growth rate by a method for measuring the crystal size distribution. The results of investigations showed that the crystal mass growth rate, the linear crystal growth rate, the quantity of crystallized sucrose per time and crystal mean size passed through a maximum at a same temperature with increasing sodium acetate or calcium acetate concentration. Small crystals grew slower than larger crystals under the same hydrodynamic conditions. Growth rates dispersion affected the formation of crystal size distribution in suspension. The presence of acetates in model sucrose solutions influenced on the change of crystal mass size distributions. Crystal size distributions, during the growth of crystals, satisfy the Rosin-Rammler-Sperling-Bennett function. The activation energy of sucrose crystal growth is a combination of the activation energies of the single processes of mass transfer and of surface reaction. Volume diffusion was dominating step in model sucrose solution, which was indicated by the activation energy value of 17 KJ/mol. The activation energy i.e. dominating process to the crystal growth was influenced by the temperature, the nonsucrose compounds and the crystal size under the same hydrodynamic conditions.
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