Study On The Size Control In The Crystallization Process Of Ethyl Maltol

In this paper, purification technology of ethyl maltol-crystallization process has been systematically and theoretically studied, which is a kind of the synergistic agent and multifunctional food additive. And the crystal size control methods of ethyl maltol has been put forward. The main contents include:Firstly, the solubility of ethyl maltol in water and 1-propyl alcohol-water mixed solvent were measured by the equilibrium method. The solubility data of ethyl maltol were simulated by the polynomial and semi-empirical activity model. Meanwhile, the metastable zone width of ethyl maltol also was measured by the laser method in 1-propyl alcohol-water mixed solvent, and the influence of agitation rate and cooling rate on metastable zone width were analyzed. The results showed that the solubility of ethyl maltol in water only has the tiniest increase with temperature rise, and the solubility of it in the 1-propyl alcohol-water mixed solvent gradually increases with temperature rise; Semi-empirical activity model is more suitable for dissolution equilibrium prediction of ethyl maltol in water and mixed solvent; the metastable zone width of ethyl maltol in 1-propyl alcohol-water mixed solvent narrow with the increase of stirring rate; it broaden the increase of cooling rate and narrow with the rise of saturation temperature.Secondly, the crystallization kinetics of ethyl maltol in batch cooling process was measured by the intermittently dynamic method in 1-propyl alcohol-water mixed solvent. And whether or not the growth of ethyl maltol crystal is related to particle size was analysed. The results showed that the growth of ethyl maltol crystal is related to particle size, especially when the crystal grain size is smaller than 100 μm. Therefore, the crystallization kinetics of ethyl maltol was analysed by MJ2 model of two parameters and the crystallization kinetic equations ethyl maltol were obtained in 1-propyl alcohol-water mixed solvent.Thirdly, after crystallization thermodynamics and kinetics of ethyl maltol were fully studied, the crystal size control of ethyl maltol in 1-propyl alcohol-water mixed solvent was researched in batch cooling crystallization process. That the agitation rate, cooling rate and seeding effect on the crystal size of ethyl maltol were analyzed. The results showed that the crystal size of ethyl maltol was smaller with the increase of stirring rate along with the increase of cooling rate in batch cooling crystallization process. In seeding policy, crystal size distribution(CSD) of ethyl maltol narrow with the decrease of seed size and also narrow firstly with the increase of seed amount. But if seed was continued to add, which seed amount is too much, CSD of ethyl maltol will become wider. At the same time, granularity control principle of seeding is analyzed by the granularity theoretical model which the seed amount is inversely proportional to the cube of the crystal grain size when the seed size is certain and the seed size is proportional to the crystal particle size when seed amount is certain were met basically. Meanwhile, local deviation reasons for the experimental results and the theoretical model predicted curves which the primary nucleation phenomena occurs because additive seed crystal provided insufficient surface area for the all crystal growth when the additive seed amount is less than the practically critical seed mass; when the additive seed amount is more than the practically critical seed mass, although the degree of supersaturation solution can be entirely consumed by surface area of additive seed crystal, because seed crystal is added too much, leading to frequent collisions between crystals and crystals, the result is that crystals are brokened and the secondary nucleation occurs. When the seed size is certain and the additive seed amount is more than the practically critical seed mass, the crystallization product size distribution can be predicted by the granularity theoretical model.