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MEI Online: Solid-Liquid Separation: Latest News: April 22nd 2003

:: New High-efficiency HVBF Filters to be Produced in Australia by Outokumpu  

New generation high efficiency horizontal vacuum belt vacuum filters (HVBFs) are to be manufactured in Australia by Outokumpu Technology.

The Pannevis RB-CDV and RT filters are designed to eliminate conventional impediments to the efficiency of HVBFs in mineral processing and chemical industry dewatering applications.

Improvements of the Pannevis designs over conventional types include enhanced hydraulic capacity and energy efficiency, high purity cake (up to 99.99 per cent from the RT) and reduced mechanical complexity, offering installation and maintenance cost benefits.

HVBFs are increasingly used as the sole mechanical dewatering technology where the material generated by the separation process has high solids content, such as cyclone underflow in iron ore washing. HVBFs are also preferred technology for filtering coarse materials, such as fine coal dewatering, and for hydrometallurgical applications including cake washing, where they are used as an intermediate step to wash away salts or recover liquid.

RB-CDV filter

RB-CDV filter
RB-CDV filter

The new RB-CDV filter which is more suited to coarse particle, single-pass dewatering has its vacuum box positioned on one or both sides, instead of underneath the filter, as in conventional designs. Because the vacuum box is therefore easily accessible for operational and maintenance reasons, the structure around the RB-CDV can be minimised and installation costs reduced. Further advantages of the RB-CDV include:

  • Enhanced hydraulic capacity. The filterís support rubber belt has no holes in it, instead using channels on top of the belt to transport liquid to the vacuum box, increasing hydraulic capacity
  • Reduced power requirements. Because the rubber belts have no holes they are thinner, allowing the drive and return pulleys to be smaller, requiring less power.
  • Belt strength. The rubber belts are grooved along their entire width to facilitate transportation of dewatered liquid into the vacuum box. These grooves act as reinforcing ply across the entire width of the belt, providing mechanical strength.
  • Liquid-gas purity. The filtersí smooth transverse travel path for their liquid-gas mixture is clean all the time. This means, as well as a higher specific capacity, there is less chance of back-mixing of liquids during counter-current washing.
  • Mechanical simplicity. The liquid-gas flow is smooth and laminar into the vacuum box and is directly separated in the vacuum box. This eliminates the need for hoses, manifold and filtrate receiver. Where counter-current washing is used to maintain liquid level control, only small receivers are required.

RT Filter

The new RT filter, meanwhile, is more suited to complex cake washing dewatering applications, similar to those frequently encountered in the chemical industry. The RT design eliminates the rubber support belt found in conventional filters. Instead, an open grid tray along the full length of the filter supports the filter cloth. The cloth, when under vacuum pulls the tray along at the same speed as the cloth until it reaches the travel end. The vacuum is briefly cut off to retract the tray to its original position and the vacuum is reapplied.

RT filter
RT filter

The major advantage of the RT filter is its ability to accommodate multi-step processing in one unit. This makes it possible to address complex dewatering requirements encountered in hydrometallurgical and chemical applications, including multiple washing steps, vibration, hot air drying and mechanical compression of the cake. Further advantages include:

  • Suitability for use for very high purity products because the RT can carry out multiple steps with each wash filtrate precisely collected into its own receiver if necessary. Washing can be undertaken with more than one liquid and can be either co-current or counter current.
  • Very high purity cakes, up to 99 per cent. The continuous cloth movement facilitates even distribution of cake across with filter, with no ripples or undulations. This results in even cake washing, both across the filter width and along its length.
  • Drying and compression options. Because the RT filter runs with thinner cakes, post-drying operations can, if required, be performed on the cake in a gas-tight or pressure-tight container. A variety of mechanical cake compression options can also be provided on the RT, such as vacuum seal belt, vacuum press belt and mechanical press belt.
  • Extendibility. Because the RTís tray is of modular construction the principle of extendability is built in.




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