CDE solve fines problem for Kieswerk Kohler

M2500 mobile washing plant eliminates fines problem and creates beneficial new sand product

FOLLOWING the installation of a M2500 mobile washing plant, Kieswerk Kohler GmbH have addressed the issues caused by excess fines in the material at their quarry in Engen/Welschingen, Germany. Moreover, the solution offered by recently formed CDE GmbH has also allowed the production of an additional sand product which the company is now able to offer to its customers.

The raw material being processed by Kieswerk Kohler contains a large proportion of material smaller than 250 microns, and with the crushing and screening processes previously employed on the material, the sand was often out of specification for use in concrete.

‘This was causing a problem as local concrete manufacturers are my main customers,’ explained company owner Thomas Kohler. ‘I had been working to develop a system which would allow production of concrete aggregates, especially sand, so that it would meet the requirements of the European standards. The solution offered by CDE GmbH has also enabled the production of an additional saleable sand product which I can now offer to customers.’

In seeking to address the issues raised by the large proportion of –250 micron material in their sand and gravel feed, Kieswerk Kohler were investigating the option of washing the material after the initial dry screening process. ‘We were thinking about several different options and ways in which we could correct the gradation curve of the sand in order to meet the required concrete specification,’ said Mr Kohler.

‘When we explained the issue to CDE they came up with a solution very quickly, and since its introduction the plant is doing exactly what I wanted it to do.’ The processing system introduced by CDE GmbH includes an M2500 E4 mobile washing plant and an AggMax 83 portable log-washer.

However, in addition to the problems caused by the excess fines content in the feed material, Kieswerk Kohler were also faced with clays and silts which the dry processing system was not able to effectively remove. The consultation between Thomas Kohler and CDE GmbH revealed that by introducing the AggMax, the quality of aggregates produced would also be improved.

‘This solution also helps to maximize sand production from the washing plant,’ explained Stefan Koelsch, director of CDE GmbH. ‘The attrition process within the AggMax plant’s log-washer liberates a lot of valuable fines that would previously have been destined for the aggregate fraction.

‘By aggressively scrubbing the material and returning the liberated fines to the sand washing plant, we are ensuring that Kieswerk Kohler recover the maximum amount of sand from the material while also enhancing the quality of the washed aggregate products by removing these fines.’

The sand and gravel feed is delivered to the M2500 washing plant by loading shovel. Operating at a rate of 100 tonnes/h, the plant accepts 0–100mm material while a grid on the feed hopper rejects any oversize.

The feed material is delivered to the M2500 unit’s integrated Prograde P2-75 rinsing screen, the top deck of which separates at +32mm; this material is sent to stockpile via one of the integrated wing conveyors.

The bottom deck separates at –32mm +4mm and this material is sent to the AggMax for scrubbing, via the integrated Rotomax RX80 log-washer. Once material has been processed by the Rotomax it is discharged on to a triple-deck horizontal sizing screen which classifies the aggregates into –32mm +16mm, –16mm + 8mm and –8mm +4mm.

Meanwhile, any –4mm material collects in the Prograde screen sump and is pumped to the integrated Evowash sand washing plant. The Evowash screen is split to allow the production of two sand grades: a 0–4mm concrete sand and another 0–2mm product.

‘The creation of the additional 0–2mm sand product was necessary as there was too much of this material in the 0–4mm range,’ explained Stefan Koelsch. ‘The sand washing phase is configured to remove up to 25% of the 0–2mm material from the 0–4mm product to allow for the production of concrete sand.’

The creation of this extra 0–2mm sand product has been an additional benefit for Kieswerk Kohler, as they have now found a market for it as a cable sand.

‘This is a bonus for us as our initial focus was very much about getting the concrete sand right,’ said Thomas Kohler. ‘Having a new sand product as a result of the investment is final confirmation that we made the right decision in purchasing the new CDE plant.’