VEGA Americas unveiled its density-compensated level measurement system during an in-booth event at MINExpo 2016. A reliable, repeatable means of controlling froth thickness in flotation cells, density-compensated level drew many visitors to the VEGA booth, and is expected to draw major interest from the mining industry.

Flotation cells are utilized in mining applications where specific chemical compositions and aeration are used to separate fine materials from slurry. Adding chemicals to aggregate materials causes reactions that separate the desired particles from the waste. Those particles then adhere to air bubbles rising from the bottom of the cell to the surface where froth is created. The froth is then raked off for further processing. Flotation cells work in packs and cascade from one to the other, separating finer and finer particles.

For flotation cells to operate efficiently, froth thickness needs to remain consistent. If the froth is too thin, the process has not been given adequate reaction time and the froth does not contain enough product. If the froth is too thick, the chemicals have been given too much time to react and they are not processing as much product as they could. In either case the process is inefficient.

Maintaining the highest efficiency in the process means tightly controlling the froth thickness. Froth thickness is controlled by the fluid level, which is constantly changing density with the addition of chemicals, water, and ore. In this case an accurate density-compensated level measurement eliminates waste in this application.

VEGA uses an electronic differential pressure system (EDP) to track density-compensated level and, by extension, froth thickness. Consisting of two VEGABAR 80 series pressure transmitters, EDP systems measure differential pressure using electronics instead of capillaries or impulse lines. The two independent transmitters measure the pressure at the mounting point and then provide the difference as an output.

One of the many advantages EDP has over traditional differential pressure systems is the ability to output more than just the differential pressure. Multiple output variables are available to users, who may select built-in applications including density, level, flow, interface, and density-compensated level. With two independent transmitters any of these variables can be set as the primary analog output, or two with the optional second current output. Additionally, up to four variables can be accessed digitally. The VEGABAR Series 80 devices can be mounted from any vessel position as well as suspended from the top to make installation easy.

Density-compensated level presents a dependable option for a mining industry accustomed to using an unreliable float system to measure the froth thickness in flotation cells. The current mechanical instrument is maintenance intensive and fraught with errors absent from VEGA’s electronic solution. The innovative density-compensated level system is already up and running in several mines across the U.S., and users report reduced maintenance, increased confidence in froth thickness measurement, and improved process efficiency.