Tonnage
350tph
Material
Dredged Sands
Output
0 to 400μm | 0-4mm | 4-22mm | 22-45mm
THE CHALLENGE
When Holcim took ownership of Chepintsi quarry on the outskirts of Sofia in Bulgaria it was clear that in order to be able to maximise the potential offered at the site a complete re-evaluation of the extraction and processing system was required. Chepintsi was first opened in 1978 by Kerierni Materiali and the original equipment was still in place when Holcim took over in 1998. “Production was very inefficient with the old equipment that was on site” explains Ivan, production manager for Holcim. “It was clear that this site offered significant potential that was not being achieved.”
To ensure that the new washing plant was entirely fit for purpose and would allow Holcim to maximise returns from Chepintsi, the company embarked on a project to clearly define the requirements of the new plant.
The project to upgrade the processing plant at Chepintsi also included a plan to replace the existing dredging plant which was seen by Holcim as being very inefficient. Another issue at Chepintsi is the presence of very ‘plastic’ clay within the dredged material. The levels of clay vary as dredging is moved around the lake but at some points a significant amount of clay is present in the feed material. “Under this clay layer is where the good quality sand and gravel is to be found but we have to cut through the clay in order to expose it.”
THE SOLUTION
The new CDE plant features a main 6000 tonne stock pile with four extractors placed underneath which feed onto two screens – one conventional and the other split into two to separate the fines, gravel and oversize material. The 4 to 45mm gravel is fed into a hopper for the Atrofeed which applies attrition to remove clay material, followed by two Rotomax log washers to ensure the gravel is free from clay contamination. The product is then rinsed and dewatered before being dry screened into 4 to 22mm and 22 to 45mmproducts. Depending on the level of clay in the feed, the plant includes a facility whereby the first RotoMax can be by-passed as and when required. “We first treat the material on the dredge which allows us to remove the very large lumps of clay” explains Mathieu Provost. “This reduces the pressure on the washing plant and also means that we are not increasing the required capacity of the 1 kilometre land conveyor and the washing plant simply to transport waste material.”
The EvoWash sand production system separates the 0 to 4mmsand for concrete and the 0 to 400μm sand for the ceramic adhesive market, thanks to a combination of sumps, pumps and hydrocyclones which can be manipulated to ensure delivery of the final sand specification. “Given the variations in feed material an off-the-shelf sand washing plant was simply not an option” explains Ivan Slavov. “The CDE plant offers a high level of adaptability and this gave us comfort that our specific requirements in relation to product specification could be delivered. A key success here is the capability for us to easily manipulate the sand washing element if the sand becomes too coarse.”
THE RESULTS
Speaking about the final delivery of the Chepintsi Project, Thomas Gullot says “CDE came to the party late on in the tender process and had much less time to submit their proposal than the others. Despite this their whole approach impressed us. They didn’t just deliver on our basic requirements. They focused on maximising efficiency, making access and maintenance easy and ensuring very high health and safety standards. They presented a modern vision of how projects like this should be managed.”
