High Concentration, Coarse Particle, Hydraulic Conveying

Abstract

Conventional coarse particle hydraulic conveying is performed under turbulent flow conditions, usually at concentrations of less than 40% v/v. The last three or four decades have seen the development of much higher concentration conveying, with the successful transport of suspensions of 70% v/v or more. These suspensions can be conveyed at very low velocities and generally exhibit very benign characteristics, having the capability of being stopped and restarted at will. There are generally two methods of pumping coarse materials safely at low velocities. The first method, using a Newtonian such as water, can be applied when the particle size distribution is sufficiently broad to minimize percolation and the concentration sufficiently high to prevent particle restructuring during transport. A second method uses a non-Newtonian, visco-plastic carrier fluid, normally fine particle slurry, to convey the coarser particles. This second method removes the constraints of the first method, allowing a greater range of coarse solid distributions and concentrations to be pumped. In both cases, the conveying characteristics appear similar to laminar flow. Both methods are described and analyzed in this chapter.