SYNTHESIS OF FLOTATION BASED SEPARATION SYSTEMS
In this work a methodology is presented for defining the optimal configuration for flotation circuit and selection of appropriate equipment for the process. The problem is represented by three hierarchized superstructures. The first level represents separation tasks, which include: feed processing, concentrate processing, and tail processing. The second level represents the stream network needed to carry out each tasks. Where for each task a superstructure is developed which includes several operational stages. At the third level, several equipment alternatives are considered for each stage. The equipment discussed in the model includes flotation column and flotation cell banks, with and without grinding. The optimal selection of the circuit is made with an appropriate objective function, upon which the values of the operational and structural variables may be determined. The problem is formulated using disjunctive programming, which is converted to a MILP problem. The model includes mass balance, equipment models, operational conditions, and logic relationship. The paper presents an example to illustrate its application for effective design of a copper concentration plant.
An experimental investigation on column flotation circuit configuration
Abstract The integration of flotation columns into existing flotation circuits of conventional mechanical cells is becoming increasingly common in industry. Nevertheless, the study of column circuit configuration is scarce and problems relating to the selection of the appropriate circuit have not been addressed. Various column circuits for flotation of coal fines have been experimentally examined and theoretically analyzed in the present study to reveal the effect of circuit configuration on the overall circuit performance evaluated using separation efficiency and separation curves. The flotation circuits examined in this study included single–stage (SS), rougher–scavenger (RS), rougher–cleaner (RC), rougher–scavenger–scavenger cleaner (RSSC), rougher–scavenger–cleaner (RSC), and rougher–cleaner–recleaner (RCRC). The flotation tests were carried out with the Pittsburgh No. 8, Illinois No. 6 and Upper Freeport coal samples that were precleaned using conventional flotation. It has been demonstrated that the overall separation efficiency of the column flotation system was rather insensitive to circuit arrangements due to the unique characteristics of the unit flotation column distinguished from the conventional flotation cell. The flotation separation efficiency changed with ash or sulfur rejection and the Pittsburgh No. 8 and Illinois No. 6 coal samples showed a stronger dependence of separation efficiency on ash rejection than the Upper Freeport coal sample. The experimental results were shown to be in good agreement with theoretical circuit analysis conclusions.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.