Research On Action Characteristics Between Inner Electrode And Power Supply In Electrostatic Coalescer

The wide use of polymer flooding and alkaline flooding in oil extraction process can make the oil produced contain complex components and too much water, which results in electric field collapse in traditional electric dehydrator and then affects the efficiency of crude oil dehydration. Instead, the newly developed electric dehydrator- electrostatic coalescer has high work stability and dehydration efficiency, with small covering area and low energy consumption. Therefore, it has broad application prospects in oil producing process. The dehydration efficiency of electrostatic coalescer is tied to emulsion properties, flow regime, electrode, power system, residence time and other factors. Meanwhile, the selective assembly of inner electrode and power supply is the key to efficient and stable operation of the device. Consequently, it has great industrial significance to study action characteristics between inner electrode and power supply in electrostatic coalescer.In this paper, based on theoretical research on circuit system and capacitance characteristics in electrostatic coalescer, a fluctuation model of peak current in AC circuits with capacitive loads is established, reflecting the change rules of currents at each side of the transformer and capacitance of the coalescer. According to the fluctuation model, calculation methods of u0.3 and u0.4 are put forward, which provides theoretical basis for experimental study on action characteristics between inner electrode and power supply in electrostatic coalescer and design of the power system.According to the results of theoretical study and field production research, the indoor experiment system has been designed and built, and the experiment system consists of power supply, transformer, insulated plate electrode coalescer with internal dual channel and circulation pipelines. Through indoor experiments, the effects of emulsions dielectric constant, flow and other factors on peak current in the startup, operation and shutdown processes of power system in electrostatic coalescer are studied. Correction factor of the theoretical model is confirmed according to experimental results, and computational formulas of i1, i2, u0.3 and u0.4 are reached. Meanwhile, based on the computational formulas, electrode structure of the industrial experiment prototype is improved, and the power system design index suitable for electrostatic coalescer is proposed. Experimental results indicate that in the startup and shutdown processes of power system, current fluctuation range increases with the increase of emulsion dielectric constant and flow; and peak current increases with the increase of emulsion dielectric constant in AC circuits with capacitive loads.Based on indoor experimental results and the power system design index, electrical source controller, transformer and other electrical devices are selected for industrial experiment prototype, and field experiment on efficient separation in electrostatic coalescer has been carried out. Experimental results indicate that there is optimal electric field strength EO for separating efficiency. When the electric field strength exceeds EO, the separating efficiency will decline. Meanwhile, moisture content of emulsions in separator export will decline when the working time of electric field and gravitational settling time increases, and then the oil-water separation efficiency will increase.The power system selected according to the power system design index operates stably and in every operating condition, moisture content of crude oil in separator export can reach the requirement for transportation, achieving high oil-water separation efficiency. And the field experiment proves that the electrode manufacturing plan and power supply design index are rational and effective.