Estudo teórico de um sensor capacitivo helicoidal aplicado ao analisador de mistura etanol-água

• Autor(a) principal: Cavalcanti, Vladyr Yuri Soares de Lima
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/12898
• topic: Constante dielétrica etanol-água; Mistura dipolar etanol-água; Sensor capacitivo helicoidal; Ethanol-water dielectric constant; Ethanol-water dipolar mixture; Helical capacitive sensor; CNPQ::ENGENHARIAS::ENGENHARIA MECANICA

The alcohol production industry has had a major technological breakthrough in the last three decades. Alcohol is present in the most diverse industries, from beverages, perfumery, pharmaceutical and to fuels, the latter being a booming market because alcohol is a renewable and sustainable source of energy. The added value of alcohol is exactly in the degree of purity that it has. This degree of purity is provided by the alcohol content measured during the alcohol production process. The technique commonly used to carry out this measurement is the determination of the specific mass and the alcohol content by digital bench mass densitometer (Brazilian Standard ABNT NBR 15639/2016). The technique proposed in this work is based on the measurement of the electric capacitance of the ethanol-water mixture and of the alcohol content with Mix Dipole Polarization Analysis (AMPD). This work presents two theoretical models applied to the AMPD in order to increase the accuracy in the measurements of the alcohol content of ethanol performed by the equipment. The first model is developed to obtain the dielectric constant value of the ethanol-water mixture, given the material’s ratio and the temperature. With the value of the dielectric constant, it is possible to calculate the capacitance value using the second proposed model, which provides the capacitance value for a capacitive sensor with helical geometry, given its configurations and dielectric constant (dielectric) of the inside content. In the direct problem, from the proportion of the ethanol-water mixture, the dielectric constant value is obtained with the proposed model for the calculation of the dielectric constant for the ethanol-water binary mixture and with the mathematical model for the helical sensor we can determine the value of the capacitance. In the inverse problem, with the measured capacitance value, it is possible to determine the dielectric constant value, and hence the value of the proportion of material in the ethanol-water mixture, i.e. its alcoholic strength. To validate the models proposed herein, simulated capacitance reading values were obtained, with a random error of 1.00%, simulating a random error of the instrument, due to the fluctuation of the electronics, due to the temperature variation. The first model, which determines the value of the dielectric constant, is able to decrease the absolute percentage deviation value from 4.65% to 0.96%, while the second model has a capacitance reading value with estimated value close to the ideal value, with a standard deviation of less than 1.00%. Obtaining the real-time alcoholic content within the ethanol industry improves the ethanol production process, since with the guarantee of obtaining the desired alcohol content, the processes are closed within the minimum time required, bringing the advantages of saving resources such as energy and inputs.