engleski

The influence of process parameters on the granulometric properties of pentaerythritol in batch crystallization

Pentaerythritol is a widely used organic chemical ; which is used in the production of high – quality alkyd resuis, lacquers, lubricant additives. The quality of obtained crystals is influenced by many factors that determine its granulometric properties. Selection of the operating conditions which result with desired crystal size distribution is very important. Commonly, the unseeded cooling crystallization is controlled by selecting the appropriate cooling profile. Batch crystallizations of pentaerythritol from water solution were carrying out at four different cooling profiles: natural, linear, optimal and step. Crystal size distribution can be explained by the supersaturation changes during the experiment. The step and optimal cooling profile achieves a high level of maximum supersaturation which causes agglomeration and crystals with wide and bimodal size distribution. At linear cooling profile, supersaturation is increased rapidly and reached maximal value at nucleation point, afterwards supersaturation decreased. Obtained supersaturation isn't too high, and resulted crystals aren't agglomerate, but on the other hand the wide crystal size distribution is obtained. Optimal cooling profile provides the constant, not too high driving force for longer period of time, and resulted crystals meet requested characteristics – the narrow crystal size distribution without agglomeration. Further more, the granulometric characteristics of obtained crystals are influenced by retention time and mixing intensity. Extended retention time causes obtaining of bigger crystals, when decreasing of mixing speed, because of unfavorable hydrodynamic conditions – low mixing rate, causes obtaining of smaller crystals. The shape of crystals isn't changed regardless of the cooling profile.

batch crystallization; cooling profile; granulometric properties; pentaerythritol

nije evidentirano