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
A HYDROCYCLONE SEPARATION MODEL IN CONSIDERATION OF THE TURBULENT MULTI-PHASE FLOW
ABSTRACT High turbulent flow conditions exist in hydrocyclones. This turbulence cannot be disregarded and the separation takes place under the influence of the centrifugal field and the turbulent transport (eddy diffusion) in the two-phase flow. A separation model for the classification in dilute suspensions (Φp in feed < 0.05 - 0.1) was developed which results in the grade efficiency curve (separation curve, separation function). On its basis the cut size d50 and the sharpness of separation x = d75/d25 are defined. The suitability of the model was examined by means of experimental results of several authors. With the help of the model the role of the essential process variables can be quantitatively or at least qualitatively explained. Further improvements and developments are possible in connection with advances in the description of two-phase flows, in the correlation between design and turbulence parameters as well as regarding dense-flow separations.
Development of polyamide curable modified epoxy novolac resins with improved adhesion and chemical resistance
Purpose – To prepare modified epoxy resins from resorcinol, cresol and phenol for improved adhesion and chemical resistance. To evaluate the properties of such modified epoxy resins.Design/methodology/approach – Epoxy novolac resins (ENRs) were synthesised by condensing epichlorohydrin with novolacs based on different types of substituted phenols for improving adhesion and chemical resistance. Various compositions were made by incorporating different proportions of polyamide resin. The chemical and adhesive strengths of the conventional epoxy and the modified epoxy resins were characterised.Findings – The modified ENR using substituted phenols showed significant enhancement of chemical and adhesive strengths over the conventional DGEBA resin. The modified ENR had an increased number of glycidyl groups (thus increased functionality) of resin, which was responsible for improved chemical and adhesive strengths over the conventional DGEBA resin.Research limitations/implications – The EPN resins used in the pr...