‘The dimensioning and shape of the ventilation ducts clearly influence the extraction’.
In the outskirts of the picturesque village of Rochefort situated in the heart of the Belgian Ardennes, lies the impressive Carrière des Limites quarry. Every year the quarry processes one million tonnes of limestone sand and granulates, where crushing, grinding and screening generates unwanted dust. A unique open air location, where Dust Control Partners (DCP) implemented a completely new dust control installation. The result? Dust reduced by over 50 percent!
Just imagine! A 65-metre deep quarry, subject to all the seasonal variations, was equipped with a completely new dust control installation. Despite the difficulties, DCP was able to expertly deal with this challenging, unusual prestige project. “All the installations are located outdoors, and the combination of lime and rain water is not ideal; over time, this will cause blockages in the pipes”, says Werner Gits, account manager at DCP. It quickly became apparent that the existing filter needed to be replaced by a compressed air-cleaned Carm-GH filter box, or in other words, a centrally located box filter which extracts from various points via a pipe extraction system. It also became clear that the supporting steel construction, fans and the entire piping needed to be replaced. All systems had to be focused on a more efficient dust extraction system for the four dust-producing units: the stone crusher, the screens, silos and conveyors. Gits: “The pipes consisted of rectangular ventilation ducts with dead zones, which resulted in a less than optimal flow of extracted dust. The old situation gave a distorted picture.”
This also proved to be the challenge. How do you calculate the correct extraction flow rate per unit when there is no comparative data available? For this reason, DCP decided to conduct a study and inspect all the separate points where dust was created, and to replace the rectangular ventilation ducts with circular ventilation ducts. And what did we find? The new Carm-GH filter needed to have a minimum extraction capacity of 34,000 m³, and a filter surface of 340 m². Almost half more than what the old filter was capable of. Although there is no comparative data, Hugues Antoine, the quarry manager at Carrière Des Limites, says there are noticeable differences between the new and old installations: ‘The dimensioning and shape of the ventilation ducts clearly have an effect on the extraction efficiency of some of the equipment. This is demonstrated by the fact that there are no more blockages, and there is less wear and tear to the pipes. The old, rectangular pipes were clearly not designed for the required extraction capacity and exhibited regular wear and tear.”
The fact that the area surrounding the quarry also benefits from a greatly improved dedusting system is not only evidenced by a reduction in dust settling on buildings and roads in the surrounding landscape. Equally as important is the fact that the design took noise pollution into account. For example, every 22 kilowatt fan was first built into a special sound-insulating box, and only then mounted on top of the Carm-GH filter box. And for a good reason! Had the fans been mounted on top of the ten-metre high filter box without any sound insulation, the noise from the fans could have been heard across a distance of a few kilometres. Moreover, this setup uses less floor space than the previous filter. A real bonus!
That the quarry has been reaping the benefits of the dust control installation since its implementation in 2015 is beyond dispute, according to Antoine. The study carried out by DCP on the required extraction capacity per unit resulted in increased efficiency, according to the quarry manager. “Of course, in a stone quarry you can’t avoid dust, that’s just the way it is. Yet the Carm-GH filter box does have an impact on the environment. There is noticeably less dust escaping at various equipment heights, such as the screens and conveyor belts.” What is remarkable is that Carrière des Limites is still working with the original set of filter cloths, as installed by DCP six years ago. An immense difference from the old filter installation, where the cloths had to be changed regularly because of the very high dust emissions at the time. Antoine: “There is considerably less maintenance. We also no longer need to inspect and unclog rectangular pipes, as we did before. That saves us a lot of time!”
It was clear to Carrière des Limites from the outset that DCP had the necessary professional experience. This was reinforced by positive references from the same heavy industry sector as the quarry. Antoine: “The collaboration was plain sailing. It is understandable that during the implementation of such a project, small challenges arise here and there, but they were always resolved effectively!”