CDE Combo Offers Eco-friendly Sand Washing Techniques

In India the restrictions imposed on the mining of river beds by the Green Tribunal set up by the Supreme Court for extraction of sand has resulted in severe sand shortage in the construction industry for both concrete making as well as for plaster. This matter is being debated and discussed in almost every forum of the industry and M-Sand has become the saviour at this time of seemingly insurmountable crisis. As a result quite a few sand washing plants have been put in the country by quality conscious operators who have adopted a green environment-friendly technology. In these plants, the crusher dust either from two stage crushing or three stage crushing, is washed and graded to produce concrete or plaster sand which is decidedly superior than river sand.

The main criticisms of the washing technology are essentially as below:

1. Requires significant quantity of water which is not always available at the location or area.
2. Produces sludge from the rejects of the crusher dust and this needs to be handled and disposed off as there is no value for this item. Moreover, it is an environmental hazard.
3. Large land requirement for sludge disposal.

The matters are particularly sensitive as these plants are mostly located in the vicinity of cities & towns and any leakages could be causing serious pollution problems.

CDE has very effectively sorted out the first problem of water management by offering a highly efficient online wastewater treatment function within their Combo range of sand washing plants through which 90% of the water is recovered and recirculated for reuse. In addition to this, CDE Combo range is equipped with the unique EasySettle technology to further add to the recovery of water from the sludge discharged during wastewater treatment so that totally +95% of the water is recovered and recycled, the balance being lost as evaporation or moisture in the product. This has reduced the water requirement to such a level that the washing plants have become cost-effective and sustainable even in areas reporting severe water shortages. This technology not only increased water recovery but enabled the operators to operate the washing plants in a small land area.

The matter of finding utilisation of the sludge, which is about 10-15% of the rock handled in the plant, has been one of the research topics of CDE for quite a while. Many of operators report that their plant efficiency was affected due to local disposal options of the sludge. Since the sludge is essentially silt, clay and very fine silica no application would be possible in the construction industry unless it could be agglomerated into some useable shape or form. Various options were thought of but it was felt that the most appropriate would be bricks or pavement blocks or similar such shapes.

A solution has been found by CDE in collaboration with a German company and it has been established that the sludge can be consolidated in any desired shape through the use of a binding agent. The chemical is to be mixed with the dry sludge in suitable proportions, which may vary from rock to rock type, and cast into mould of desired shape. The mould could be made of any material such as plastic or steel.

The advantage of these bricks is that they do not require any heating for achieving hardness. Left to itself for 24 hours they attain the workable strength. In case faster hardening is required then additional hardener could be added to the chemical mix and 6-8 hours would be sufficient. This is a great advantage for the operators as the energy requirement is minimum. The bricks are being tested for their various properties and depending on the results the application area could be decided.

With this innovative application the customers can now utilise the entire feed material and there is no wastage for disposal. Also the water requirement is bare minimum as a result of +95% recycling. This has changed the economics of washing plant operation completely.

The legacy of CDE is value recovery from wastes through use of environment-friendly technologies and the company is continually innovating to develop sustainable wet processing techniques that will mitigate the risks of pollution and its adverse impact to the environment. To use every bit of waste but yet waste nothing.