Real-time monitoring of polyester esterification rate

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The esterification reaction typically involves 4 substances; for example, terephthalic acid (PTA) and ethylene glycol (EG) undergo an esterification reaction under certain conditions to produce bis(2-ethyleneglycol) terephthalate (BHET) and water. There are significant differences in the density (specific gravity) of these 4 substances: the reactant PTA has a density of 1.55, EG has 1.1155, the product BHET has 1.089, and water has a density of 1.000. Obviously, when the feed ratio is constant (known), the density of the entire reactant system (i.e., the material system comprising the four substances mentioned above) varies depending on the degree of reaction progression (i.e., the esterification rate). Therefore, by monitoring the density of the system in real time and taking the feed ratio into account, it is possible to calculate the esterification rate of the esterification reaction using a model. Given the complexity of the esterification reaction, building on the aforementioned density method and taking into account other characteristics of the esterification process, multiple approaches are utilized to estimate the esterification rate, thereby forming what is known as \"multi-sensor information fusion\" in order to improve the accuracy and reliability of detecting the esterification rate. For example, the heat cross-method, the boiling point elevation method, etc. Through the above methods, parameters such as the esterification rate of the esterification reaction are calculated using models, and these values are displayed in real time on the DCS to guide production.