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MEI Online: Solid-Liquid Separation: Latest News: October 11th 2006


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:: Two of the Largest Filter Presses Ever Built to be Supplied to Goedehoop Colliery

Seprotech will supply two of the largest filter presses ever built to Anglo Coal’s Goedehoop Colliery for the dewatering of fine coal. The filter presses will be commissioned by Seprotech during the last quarter of 2006.

Worldwide, there is a growing awareness that fine coal needs to be recovered as final product from plant effluent streams. The driving force behind this move is two-fold: environmental aspects as well as the need to generate additional income. Fine coal does not require additional mining, but does require further processing to be recovered as a saleable product.

The two automatic Ishigaki ISD GC H2100 X1000 filter presses will be fully imported from the OEM in Japan. Each filter press weights 140 t and has a throughput capacity of 36 tph.

These Ishigaki filter presses were selected because these are the only units available on the market that can individually achieve the colliery’s required tonnages. The fact that they are fully automatic will translate into labour savings, as the filter cake is automatically discharged by a traveling cloth system, also a first in fine coal filtration. The filter presses will be assembled and erected on site by DRA under the expert supervision of Seprotech and Ishigaki.

"In this application at Goedehoop, fine coal which was previously regarded as waste will now be recovered as a saleable commodity," comments Horst Schulte, managing director of Seprotech.

With fine coal, it is important to remove the waste material from the coal fines, which lowers ash content and improves the calorific value of the coal. "This is achieved using in-house flotation technology developed at Goedehoop," says Schulte.

"Because flotation is a wet process, it will be necessary to dewater the product. In some applications, centrifuges are used for this purpose but in this particular case the moisture content in the solids discharge and the solids losses in the centrate would be too high. It was therefore decided that the most appropriate solution would be to use filter presses, which were tested and approved by the client" he explains.

During the filtration process, the feed slurry is pumped into the feed port, distributed into the individual chambers of the filter press and filtered through a cloth-filtering medium. Effective cloth washing, which is crucial in the filtration process, has now been integrated, resulting in a high level of dewatering with optimum filtration and separation of solid matter from the filtered solution. The life of the cloths increases exponentially if they are washed on a regular basis.

As the filter cake accumulates and become thicker and more compact, it restricts the flow of the solution and more pressure is required to overcome this resistance. Once the compact filter cake is formed inside the filter press, it is discharged quickly and easily with the traveling cloth system. After cake discharge the cloths travel down a second time for the washing process. Static spray bars with spray nozzles wash the filter cloths in approximately 40 seconds as the cloth travels down and then back up into position, effectively giving the cloths a double wash. The cloths are washed in banks and the cloths on these specific presses will be washed once every fourth cycle.

"All the process sequences are completely automatic requiring zero manual intervention, apart from normal maintenance," says Schulte.

Seprotech was established in 1958 and during 2000 became a member of the Multotec Group of companies. The company has been supplying filter presses for 20 years.




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