Research On The Measurement Of Water Content In Crude Oil By Double Channel Microwave

With the widely use of oil, more and more oil is extracted by countries all around the world. During extraction process, the measurement of water content of crude oil is an important link which can not be ignored. Microwave method takes use of space radiation method to pass through internal part of media, and it has such advantages as non-contact, suitable to online detection, wide measurement range, non-radiation, highly accuracy and so on, as a result, it has been widely used recently.In this paper, according to the principle of transmission attenuation method in microwave nondestructive detection method, an analyzer used to measure water content of crude oil is designed. The basic principle is dielectric constant of oil is different from that of water so that when microwave passes through mixture of oil and water, changes of its energy attenuation changes is mainly caused by water content. As a result, according to attenuation, water content in the mixture is obtained.The whole system includes three parts: microwave testing, signal processing and display. Microwave testing module makes circulator and modulator combine to achieve double channels measurement including measurement channel and reference channel which is aimed to avoid interference caused by poor stability and space signals of microwave signal sources and to achieve high measurement accuracy; Microwave testing module mainly includes microwave sensor, modulation, transmission, attenuation, detector of microwave signal and so on; HFSS software is used to simulate microwave sensor, index of microwave sensor are as follows: gain is 16.37dB, S11 is -35.44dB, VSWR is 1.15. Microwave signal from measurement channel after attenuation is compared with reference channel. Signal processing module is used to deal with microwave signal carrying water content information through selective frequency amplification, precision rectifier, low-pass filter, and then send them to A/D converter, and then these signals are sent to MCU, finally actual water content is displayed by LCD. The measurement range of the whole system is 0~35%, that is to say, water content can be accurately displayed in the range of 0~35% and measurement error is only±1%. But when water content of crude oil is more than 35%, measurement error will increase, because when water content increase, mixture of oil and water is not uniformed which will cause instability of microwave signal detected. In a word, this system is suitable to low water content measurement.