Advances in the Theory and Practice of Hydrocyclone Technique
With numerical simulation of hydrocyclone separation based on the Navier-Stokes and mass transfer equations, it is possible to perform hydrocyclone experiments on a computer. With the help of computational engineering, the cost of conducting hydrocyclone experiments in the planning phase of new hydrocyclone units can be cut drastically. The simulation models also enable a deeper insight into the static and dynamic process behaviour in hydrocyclones. It is shown that the solids stored in the hydrocyclone represents a sensitive process variable for separation in the hydrocyclone. On this basis, a new control concept for a hydrocyclone battery has been developed. As the solids concentration in the feed increases, the combined overflow of all the hydrocyclones in the battery is throttled. At the same time, the feed pump speed is increased. In this way, while the total throughput remains constant, the volume split changes to effect that more solid material is discharged in the hydrocyclone underflow. This computer-based process control system is ideally suited for hydrocyclones in separation plants for tunnel driving projects as well as for those integrated closed-circuit grinding
True Grit. A Grit Removal Efficiency Investigation at Five Wastewater Treatment Plants
The Hampton Roads Sanitation District (HRSD) owns and operates thirteen wastewater treatment plants (WWTP) in Southeastern Virginia. Several HRSD WWTPs experience abrasive wear to equipment, reduced operating volume in aeration tanks and digesters, premature equipment repairs and increased maintenance cost due to poor grit removal. In 2007 and 2008 HRSD embarked upon a grit removal study at five of the WWTPs. The objective of the study was to evaluate the grit removal efficiencies of these plants. The study compared three medium energy forced vortex grit units, a gravity settling detritor, and an aerated grit system. All five plants use hydro cyclones and classifiers. The study concluded the detritor had the highest grit removal efficiency and the angle of the hydro-cyclone is a contributing factor in grit removal efficiency. The study also recommended several equipment and operational strategies to improve grit removal at the other facilities.
Statistical properties of momentum transfer in two-phase flow
Abstract The momentum transfer in a two-phase stream, consisting of particles carried by a fluid, was studied by applying the statistical theory of turbulence. Statistical relations showed that the correlation, scale and intensity of one phase can be calculated from those of the other phase. Approximate solution indicates the basic parameters affecting momentum transfer.