Elements of the theory of forced mixing of oils in tanks

Abstract

To prepare for transportation at the fields, light and heavy oils are mixed with the help of jet mixers, which are injection devices that are installed in the receiving and distributing nozzle inside the tank. The work considers the simplest technological mixing scheme. The basic equations are presented that describe the processes of mixing light and heavy oils in a mixer, in which the light oil stream is the working stream, and the source stream in the heavy oil tank is the injected stream. The characteristic equation of the mixer is obtained. A system of equations is presented that describes the trajectory of the center line of the jet, changes in oil composition and average velocity along the jet. An example of a mixer, which is used in practice in a reservoir of the PBC 2000 type, is considered. Based on the characteristic equation for the known pressure drop of the working and injected flows, as well as the ratio of the sections of the working nozzle and the output section of the mixing chamber, the mixer injection coefficient is found. The calculated graphs of the characteristics of a turbulent flooded jet in an oil field oil storage tank are presented. From the graphs it follows: 1) there is a complete alignment of the concentration of the injected oil mixture with the concentration of heavy oil in the tank; 2) the speed of the jet decreases at a distance of the order of several meters to a value exceeding the minimum fishing speed known from the practice of liquidating bottom sediments. The main role of the mixer when mixing oils is that due to the injection of heavy oil from the reservoir, forced circulation flows are formed that exclude the formation of stagnant zones and the precipitation of solid inactive deposits.