Study of powder injection into water using an on-line particle detection system

Particle behaviour during the downwards, pneumatic injection of powder into an aqueous medium (water) has been investigated by means of a new method which involves the direct measurement of particles by an Aqueous Particle Sensor (APS) unit. Through this method, phenomena and parameters related to injection processes, such as gas-particle disengagement distance, liquid-particle jet diameter, jet cone angle, particle dispersion and distribution within the liquid, have been investigated both qualitatively and quantitatively. The effect of gas and powder flow rates (powder/gas loading ratio) in determining the injection regimes and particle behaviour within the liquid were the main parameters investigated. It was demonstrated that the jetting regime can be easily achieved as a result of increasing momentum transfer from the particles to the gas phase. However, this required a high loading of particles. The entrainment of gas with the injected particles took place not only during jetting, but also during bubbling flow, such that some gas was always entrained by penetrating particles, the two enter the liquid as a gas particle jet, but Leave large gas bubbles at the lance tip. It was further demonstrated that the gas flow rate had a greater effect on particle suspension within the liquid than did the powder flow rate. (C) 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.