Continuous preparation of water-in-heavy oil emulsion without emulsifier by SiC membranes at high temperature and its micro-explosion performance

Emulsified heavy oil as an alternative fuel is of great significance for reducing environmental pollution and settling energy crisis. The micro-explosion of the emulsion plays a vital role in improving the fuel efficiency as well as reducing harmful gas emissions. Here, the water-in-heavy oil emulsion was prepared by membrane emulsification at high temperatures (60–100 °C) without using any emulsifier, and its puffing and micro-explosion performance were investigated by the suspended drop method. The water droplet size (D₉₀) of emulsions can be controlled from 3.8 μm to 7.0 μm by controlling the emulsification process parameters (i.e., membrane pore size, the flow rate ratio of the dispersed phase to the continuous phase, the flow rate of the continuous phase on the membrane surface and temperature of continuous phase) using SiC membranes. Moreover, the trend of droplet size can be predicted based on analyzing the forces on an individual droplet that govern by the emulsification parameters. The puffing and micro-explosion probability of the emulsions increased with the increasing water content and droplet size, which can also effectively reduce the coking of heavy oil at 500 °C. As a result, the highest probability of micro-explosion (90%) and the lowest probability of coking (10%) were realized at a water content of 5 vol% and an average droplet size of 6.5 μm. Therefore, the utilization efficiency of heavy oil can be improved by membrane emulsification process.