Effect of gas state on solid movement with three-phase flow in riser

The gas states (gas volume or movement characteristics of gas-phase) have an important effect on the move- ment and lifting efficiency of ores when using an air-lift system to lift the slurry in borehole hydraulic jet mining. The solid velocity model in riser was proposed based upon the three-phase flow theory and bubble dynamics theory. By sim- ulating the ore using the ceramic particles,the experimental study on the effect of different operating parameters (gas volume,submergence ratio) on particle lifting was carried out by using a self-designed airlift system. The moving ima- ges of gas-liquid-solid three-phase flow in different air-inlet was obtained by using the high-speed camera. The influ- ence mechanism of gas-phase on solid movement was discussed based on the image processing,moreover,the analytic results were compared with the experimental results. Results show that the influence modes of bubbles acting on solids is not the same under the different air volumes,as well as the influence degree of bubbles. Liquids have a significant effect on solid movement when the air-inlet is small,meanwhile,solids were lifted followed with gas-liquid phase along pipe wall,and its quantity and velocity is maintained at a low level. The bubbles have an significant effect on the pro- motion of solid and liquid with the increase of air-inlet,the concentration of solid-liquid phase and mixture flow veloci- ty are close to the maximum,the whole is moving to pipe center. In addition,the lifting velocity of solid in pipe center is greater than that at the pipe wall,and the moving trajectory of mixture flow in pipe is a spiral progress;however,the gas velocity is too high and the mixture flow turbulence is strengthened when the air-inlet is maintained in a high lev- el,the solids lifting is discontinuous and the concentration of liquid-solid phase is decreased significantly. In addition, compared with the submergence ratio,the effect of gas volume on the solid movement is more significant. The different characteristics of three-phase flow patterns is showed with the air-inlet changes,and the effect law of gas on liquid-sol- id phase is smaller. The experimental results gives a good fit to the numerical analysis which has a guiding significance for borehole hydraulic jet mining.