Page 26 - HUB-4 Magazine Issue 71

Quarrying
Most companies today need to produce the driest possible cake that can be stockpiled, transported, and potentially used as a product from the end of the washing process. To achieve this filter press technology offers the best solution to process a variable feed and produce the driest possible cake. Typically, the moisture content of the filter cake is below 25% moisture compared to 40% moisture from other alternative technologies. This guarantees the maximum return of water into the washing process and the lowest loss of water out of the process.
Filter presses are machines used to dewater slurry. They separate solids from the waste water or slurry and recover the water, which can be re-used in the processing cycle. Filter presses are used in a wide range of applications - aggregates washing, mining concentrate and tailings, recycling, concrete batching plants and virtually in any process where water/solid separation is involved.
Tyrone International work exclusively in the UK market with our Italian partner Fraccaroli & Balzan, who have been
designing and manufacturing industry leading filter presses for more than fifty years as one of the world leaders in this technology.
A common misconception:
The filter press is basically constructed from a heavy-duty steel chassis carrying a series of recessed plates covered by a filtering medium (cloths and sometimes backing cloths). The plates are kept tightly closed by hydraulic rams creating a seal around the perimeter of the plates. A high-pressure slurry pump forces slurry into the empty chambers between the plates which have an inner cavity holding the solids, while the water drains through the clothes and is recovered for the process. It is a common misconception that the hydraulic rams squeeze the water out of the sludge when it is the pump that feeds the sludge into the press which creates the pressure to force the water out of the sludge. The result is dry solid cakes containing a low percentage of moisture, which are dropped beneath the filter press at the end of the filtration cycle. This process is fully automatic and does not require the presence of an operator.
The feed pressure to the press is also an important consideration. If the feed pressure is too high (for example 20 bar) then this will result in high energy consumption, accelerated wear on the filter cloths, accelerated wear on the pump impellors and liners and damage to pump seals. The goal is to achieve filtration at the lowest possible feed pressure which in our industry can be found between 10 and 14 bar pressure. To achieve the driest possible cakes, factors other than feed pressure are considered such as the density of the feed sludge, the thickness of the filter cake and the choice of filter cloths.
When considering which filter press to purchase customers have a choice between a side beam press or overhead beam press. Side beam presses are manufactured from rectangular steel box sections which run along either side of the filter plates whereas overhead beam presses are manufactured from heavy duty I section beams located at the top of the filter plates. Therefore, side beam presses are cheaper to construct and tend to be used for smaller applications as they cannot support as many filter plates as overhead beam presses without the addition of further steel frame supports. Overhead beam presses offer unrivalled access to the filter cloths whereas side beam presses obstruct access and maintenance to the cloths must be done from the top of the filter press.
To meet the growing demand of the market for larger throughput capacity, the size of the filter presses has constantly increased and now Fraccaroli & Balzan manufacture some of the largest filter presses in our industry that can discharge up to 32 tons of cake per press cycle.
Even though the basic concept of filtration is quite simple, Fraccaroli & Balzan has enhanced many features to improve the performances of the filter press, reducing operational costs, increasing the production rate, and making the management of the filter press much easier.
The larger filter presses are equipped with dual over-head beams, to provide a high structural integrity, plate stability and easy access to the plates for maintenance or any other intervention. In fact, the structure of the filter press is completely open from the sides and from above, so that the operator can enter directly into the filter press and the plates can be removed from the top.
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www.hub-4.com Nov-Dec 21 - Issue 71