AUTOMATION OF TURBIDIMETRIC METHODS FOR SOLUBILITY DIAGRAMS DETERMINATION

摘要

In crystallization process several characteristics of the product ought to be known : growth and nucleation kinetics, solubility diagram and crystallization enthalpy. Solubility diagram represents the first step for the studying of crystallization process. Once this one achieved, operational parameters and process yield can be calculated. In order to determine solubility data, an automated system has been developed using FIX MMITM software from Intellution~?. The experimental setup is completely driven by a CQM1 OMRON~? programmable logic controller (PLC). The batch crystallizer is equipped with a stirrer and a glycol-jacket for heating and cooling. Since turbidimetry has proved to be an adequate technique for determination of solids concentration, it was applied. A turbidimetry sensor FSC402 Mettler-Toledo? has been used to find out transition between saturation and supersaturation zones with an accuracy of 1g/100g. Turbidity allows the programming of successive heating, cooling and dissolution cycles, inside a temperature area previously defined. Real-time graphic display enables to show results in graphical and numerical form. Saturation and supersaturation data are automatically determined. This system has been successfully tested on organic and inorganic substances : glycine, galacturonic acid, sodium bicarbonate and sodium acetate. Experimental results agree with the ones found in literature (deviation<5 %). Furthermore, this method is adequate for colored substances even in presence of a large quantity of impurities.