Determinação de teor de água em emulsões de água em petróleo usando técnicas ultrassônicas.

Abstract

Piezoelectric ultrasonic sensors have been developed for the characterization of solid and fluid samples. However, the characterization of fluids with high opacity, such as waterin-crude oil emulsions, has much to be improved. This work develops a set of sensors, capable of being installed in several stages of petrochemical processes. The first one, a pulse-echo-transmission probe working at 3.5 MHz, measures the propagation velocity. The second one, a delay line cell operating at 5 MHz, measures the propagation velocity and the attenuation. The third one, a backscattering ultrasonic cell, was used to study ways of maximizing sensitivity, using a deterministic model to find the best distribution of the passive components. Due to the high acoustic attenuation in water-in-crude oil emulsions, the backscattering cell designed in this work was used in an attempt to quantify the oil content in crude oil-in-water emulsions, which have lower attenuation. Taking into account the temperature effect, the first two prototypes manufactured in this work were able to measure the content of water in water-in-crude oil emulsions up to 40% in volume with a sensitivity up to 1.2 m/s per each degree variation in the concentration. For the delay line cell, this result was achieved even with flowing samples. Even though the third prototype (backscattering cell) was not capable of detecting the crude oil content in a range of the parts per million (ppm) in crude-in-water emulsions, it was developed a design criterion for this sort of technology based on the scattering model. The information provided by the pulse-echo/transmission probe and by the delay line cell can be used to optimize the water separation in the first stages of petrochemical processes. This implies a significant reduction in the emission of pollutants that cause the greenhouse effect during the production of crude oil-based materials.