Increasing the sensitivity of measurement of a moisture content in crude oil

Abstract

Purpose. Investigation of a moisture frequency transducer based on a moisture-sensitive capacitive element of a cylindrical structure with mesh electrodes for a system for measuring the amount and parameters of crude oil. Methodology. When constructing a moisture-sensitive element, an oscillatory method for measuring humidity was applied to achieve high sensitivity and accuracy while maintaining a low cost of the device. A moisture sensitive capacitive sensor based on a cylindrical structure with mesh electrodes was introduced into the measuring generator system based on a transistor structure with a negative differential resistance. Findings. Analytical expressions are obtained to describe the dielectric constant of an inhomogeneous mixture of water and oil. Using these equations, the capacitance of a moisture-sensitive sensor with mesh electrodes is calculated as a dependence of the moisture content of crude oil. It was determined that the capacitance of the moisture sensitive sensor increased from 20 to 44 pF when the mass moisture of crude oil changed from 0 to 30%. The sensitivity of the developed capacitive sensor is 0.8 pF/% when using a measuring device in the form of a crude oil pipeline with a diameter of 50 millimeters. Originality. A mathematical model has been developed for the primary transducer of the moisture content of crude oil based on a cylindrical capacitor structure with net-like electrodes, which allows determining the value of the capacitance of the primary transducer of the moisture content of crude oil. A self-oscillator device for controlling the moisture content of crude oil has been developed on the basis of the structure of bipolar and field-effect transistors with a cylindrical capacitor structure with mesh electrodes. Practical value. Circuitry solutions for a moisture transducer for crude oil have been developed. The results of experimental studies showed that for the selected version of the moisture converter circuit, the output signal frequency decreased in the range from 1.617 to 1.27 MHz with a change in the mass moisture content of the Turkmen mixture from 0 to 30%, respectively, and is close to a linear dependence. The wide frequency range of the output signal of the secondary converter with the frequency output of the measured information increases the accuracy of moisture measurement in crude oil by an order of magnitude.

Capacitive Water-Cut Meter with Robust Near-Linear Transfer Function

“…After substituting these capacitances into Formula (2), we received the following maximal and minimal values of moisture content: W max = 30.235%, and W min = 29.633%. The value of absolute moisture measurement's extended uncertainty was equal to U(W) = (30.235 − 29.633)/2 = 0.3%, which is very good for a capacitive water-cut meter, because modern accuracy limits are mostly no lower than 0.5% (in [20,24], we have 1%; in [26], −0.67%; in [21], −3%...)…”

“…In other cases, the effectiveness of traditional compensation methods essentially decreases, because of which further improvement of the existing methods of moisture measurement with a view to solving the problem of type-uncertainty compensation is a relevant and perspective mission [20]. In-depth analysis of modern moisture control approaches with the purpose of further development and improvement is still a relevant task, and the process of searching for new methods of water-cut sensing optimization is under constant continuation [21][22][23].…”

Device for measurement and control of humidity in crude oil and petroleum products

“…The sensitivity and accuracy of amplitude humidity sensors can be increased by complicated methods involving computer processing of electrical signals measured [3]. Another way to increase the sensitivity of measuring parameters of physical quantities is to use generator methods [17] and resonance methods [18]. In [19], it was proposed to use the generator method to increase the sensitivity and accuracy of humidity measurement of petroleum products.…”

“…The accuracy of the device is improved by automatic compensation of the systematic error [29]. This automatic compensation includes automatic setting of zero before a measurement starts, automatic calibration operation (self-calibration), self-monitoring, and reducing the impact of random errors by multiple measurements with averaging the results [18,19].…”

Developing and Investigating the Analyzers of Kinematic Viscosity and Density of Petroleum Products on Throttle Bridge Transducers

“…This requires restoration of the operating condition of equipment. The solution is to create new methods and automatic devices for determining the quality of fuels and lubricants, suitable for use in refineries and in processes of transportation, storage and utilization of petroleum products [4][5][6].…”