(70d) Non-Isothermal Crystallization Kinetics of Waxy Crude Oils

A new method to study the quiescent non-isothermal crystallization kinetics of waxy crude oils is presented. The measurement technique consists of a cross polarized microscopy coupled with enhanced depolarized light signal detector and image analysis. This integrated optical system enables direct visual detection of wax crystallization temperature (also known as wax appearance temperature or cloud point) at a given cooling rate and, more importantly, makes it possible to monitor the associated morphological changes of the formed wax crystals. Analysis of the wax particles nucleation as well as their growth process using two oil samples from different geographical locations is presented. Results indicate the similar crystallization trend as observed in simple compounds, such as - normal paraffins and polymers, and modeled in terms of Avrami and Ozawa theories for non-isothermal crystallization. This novel approach is adopted to screen commercial wax crystal modifiers and optimize their respective dosages in waxy crude oils. Basic rheological measurements and cold finger deposition kinetics for selected waxy crude oils are also reported.