Sistema híbrido ultrassônico-capacitivo para análise da qualidade de óleo combustível

Abstract

Heavy fuel oils (HFO) are widely exploited to produce electric energy in Thermoelectric Power Plants (TPP), mainly due to the amount of heat released during its combustion. Economic factors also influence the use of HFO for energy generation, including the low cost of energy content, availability due to raw materials, ease of transport and storage, low operating investment costs, among others. The power to produce energy from HFO is defined by its calorific value (or heating value) and is linked to the quality of the fuel oil and the presence of contaminants, such as water. A fuel oil with properties different from those expected/specified can not only decrease the calorific value, but also can cause damage to the TPP equipment. Therefore, the analysis of the quality of fuel oils is of great importance for TPPs. This work proposes a methodology to estimate three parameters of the quality of fuel oils: the density, the water content in the oil and the calorific value. The proposed methodology has developed a system that has techniques such as ultrasonic, capacitive and temperature measurement to estimate quality parameters. The ultrasonic system is based on the propagation time of the ultrasonic waves to estimate two quantities, the speed of sound and the flow of the fluid. The capacitive system correlates the capacitance variation with the water content in oil, starting from the existing association between sensor, fuel oil and water. Temperature measurement data is used in conjunction with sound velocity data to compensate for the effect of temperature on the density estimation. Based on the temperature and velocity of sound information, and using a classification algorithm, a method was developed to recognize the existing similarity between the OC under analysis and the OC information from a database. With the result of the classification, the scores and the information from the database are obtained to estimate the density. Finally, the calorific value is calculated by associating the density and water content data. The results obtained from the tests were compared with data from laboratories and technical sheets of the OCs, reaching relative deviations lower than 1.0% and 0.5% for the density and calorific value, respectively.