Declining ore grades pose a special challenge for mining operations. Of course there are various processing techniques to get the most out of the raw materials like thickening and flotation. But naturally they consume energy, chemicals and water. Which means that, to balance out the yield and the costs, the extraction processes must run at an optimum level. Especially in times of volatile markets and prices.
Flotation and thickening are fundamental steps in modern mining separation processes. Achieving an optimal separation however is a complex task due to the many interconnected variables. Both processes use chemicals which are one of the main cost drivers. And they consume also a lot of water, which in some mining regions can be a very scarce resource, which the plants first have to produce through processes like desalination of salt water for example.
Froth interface solutions for flotation tanks
Increase recovery rates and grades
Reduce gangue carry over
Optimize chemical dosing
Improve the water utilization
Flotation is used in various mining processes such as gold and copper to recover mineral particles finer than 500 micron or 35 Mesh. The most important parameters for process efficiency are: Flow and density measurement of feedstock, froth height, a precise determination of the froth and liquid slurry interface, liquid pH and Eh, dosing and quality of chemical reagents, froth bubble quality and air flow if used for agitation.
The level of the froth and the froth/pulp interface are one of the key factors for the process. We recommend using a Prosonic interface measurement transmitter with two ultrasonic sensors if instruments can be installed at the top of the tank in combination with an XPSFloatTM system consisting of a PTFE coated conical float, a teflon rod and a target plate. One sensor measures the distance to the bubble surface and the second, the distance to the target plate, the difference is the foam height.
The dry solids content and feed rate and the froth height can be used as a feed forward signal for the xanthate, frother and pH modification chemical dosing control loop. A Promass I coriolis flow meter can input these parameters and enable very accurate dosing. And the unique Promass Heartbeat Technology enables operators to monitor the quality of the reagent with respect to viscosity, density and temperature in addition to any pipe line corrosion or sticky build up.
Thickening is the separation of suspended particles from a liquid by gravity settling. The mineral feed stream enters the thickener through the central feed well as slurry. Solids settle on the tank bottom and this process is sped up by adding a liquid chemical flocculent. For effective thickener control, six measurements are critical: bed mass inventory, bed level, underflow density and flow, flocculent dosing and overflow clarity.
Bed level or height measurement controls the flocculent addition rate. It gives feedback regarding the effectiveness of the flocculent dosing process. Additionally, it can show the surface profile of the fluidized bed and give an early warning of solids carrying over in the clarified liquid overflow. Bed level is ideally measured using submersible sonar technology.
Bed mass inventory is inferred from a pressure measurement in the cone or tank outlet. This controls the underflow pump speed. It is best measured using a pressure sensor with a ceramic diaphragm since the solids particle mass is generally very abrasive. This measurement records the pressure of the sludge and liquid column that is present.
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Whatever challenges you face with your extraction processes - be it low yields, high OPEX or expensive maintenance routines - thanks to the in-depth industry expertise of our consultants they know exactly how to improve your processes. Together with our customers they have achieved remarkable results during the past 60 years - thanks also to our industry-optimized instrumentation portfolio.
reduction of chemicals used.
reduction of hours spend on maintenance possible.
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