Turning previous unusable materials into valuable resources
BHS-Sonthofen and MSW Mineralstoffwerke Südwest received the German Resources Efficiency Award 2016 on 16 February 2017. The prestigious prize was awarded by the German Federal Minister for Economic Affairs and Energy to the two companies to commend the development and successful implementation of the Combimix process. This process turns a previously worthless mining by-product accumulated in quarries into a valuable building resource.
BHS developed the Combimix process based on their twin-shaft batch mixers and implemented it together with MSW at their quarry in Mönsheim. This marked the first German project of this kind. It helped to increase raw material efficiency from the previous level of 65-70% to around 93%.
In quarries and gravel pits, the Combimix process takes clay-and-rock mixtures – which previously had to be refilled or disposed at a landfill – and turns them into a marketable building material. Furthermore, this means that millions of tons of material previously considered worthless and dumped can now be reactivated.
BHS has also installed the Combimix system in several quarries in France using continuous mixers. Before the system was installed, in one facility more than 100,000 t of rock/clay mixture from the quarry had to be dumped every year. More than 90 % of contaminated feed material is now sold as rock grade thanks to the Combimix system. The plant manager is extremely pleased about the significant reduction in costs: „Before the mixer was installed, we had to break down 400,000 t of rock each year to obtain 300,000 t of salable material. The new procedure means we only require 330,000 t to achieve the same delivery quantity.“
The German Federal Ministry for Economic Affairs and Energy (Bundesministerium für Wirtschaft und Energie) awards the German Resources Efficiency Award to exemplary products that efficiently use raw materials and other materials, processes or services, as well as application-oriented research results. A jury comprising 14 members screened over 40 submissions to select four winners in the „Companies“ category and a single winner in the „Research Facilities“ category.
Andre Däschlein, Director of International Sales for Mixing & Crushing Technology at BHS, and Benedikt Fahrland, Managing Director of MSW Mineralstoffwerke Südwest GmbH & Co. KG, accepted the award presented by Uwe Beckmeyer, Parliamentary State Secretary of the Federal Minister for Economic Affairs and Energy at the „Efficient use of raw materials – Market success“ symposium.
A happy moment for Däschlein: „This award demonstrates yet again that deep industry know-how and close ties to their customers allow mid-sized companies, in particular, to create innovative processes and solutions that deliver true efficiency gains.“
Except from the laudation of State Secretary Beckmeyer: „The sparing and efficient use of natural resources is a key skill needed to create a sustainable society. This year“s winning projects serve as role models of innovative and competitive industrial entrepreneurship in Germany. They furthermore pave our way to becoming less dependent on resource imports.“
MSW introduced the process at their Mönsheim quarry in the summer of 2016. It allowed the company to increase their repository“s yield by 25%. To produce the same volume of the final product, it was previously necessary to extract about 620,000 tons of limestone annually. Now the total is around 188,000 tons less, which corresponds to a relative reduction of around 30%. It helped to increase raw material efficiency from the previous level of 65-70% to around 93%.
Dennis Kemmann, the Managing Director of BHS-Sonthofen GmbH, is already thinking ahead: „Our Combimix process holds a vast potential as it enables companies across the globe and throughout various industries to utilize resources more efficiently. In the context of rehabilitating contaminated soil, Combimix can be used to remove oil and other harmful substances. As a result, only a small fraction of the feed material needs to be dumped in hazardous waste landfills. The process is also viable for the cement industry. Here, it can be applied to processing limestone, a key ingredient that improves the burning process in rotary kilns and thus contributes to reducing fuel consumption.“
The technology in detail: Combimix process
The unique characteristics of the BHS twin-shaft continuous mixer of type DKXC lays the foundation for the Combimix process. Specifically, this type of mixer is the first to allow regulation of the retention time of the material in the mixer within broad limits. Thanks to this feature, the lime has enough time to mix intensively with the clay, to dry and to undergo a chemical reaction that allows it to be reliably separated from the rock in the next processing step.
The new process thus conserves limestone resources and extends the usable lifetime of quarries. Because less material will be classified as unmarketable, Combimix also creates space in landfills and backfills. Furthermore, this means that millions of tons of material previously considered worthless and dumped can now be reactivated. Given that roughly 25% of the material no longer needs to be backfilled, the BHS method also helps to make space in the landfill – space that can be used to deposit other materials.
Small limestone deposits or those previously labeled unprofitable can be turned into viable sites at very little effort using this technology. For example, the method allows for the extended operation of quarries that were on the verge of being shut down due to a large share of clay in the rock or because of insufficient backfill capacity.
Combimix also contributes to securing resources by providing the means necessary to reactivate large quantities of dumped materials that had been considered unmarketable in previous decades. As a result, millions of tons of material can be processed and sold at a profit.
Another innovation is that operators can now opt for a dry process instead of a wet process. In many quarries, not enough water is available for wet processing in a log washer, and the subsequent water treatment as well as sludge disposal prescribed by law are extremely costly.
BHS is the only mixer manufacturer to offer a continuous twin-shaft mixer with adjustable retention time, which is precisely the tool needed for this task.
MSW case study
The shell limestone extracted at the Mönsheim quarry operated by MSW Mineralstoffwerke Südwest has a high clay and silt content, which contaminates the valuable rock. For this reason, an average of 30 to 35% of the material extracted at the quarry could not be marketed. On top of that, the clayey screen waste had to be backfilled on site as overburden.
In the summer of 2016, MSW commissioned a Combimix system based on a customer-specific twin-shaft batch mixer that admixes the clayey screen waste with approx. 1% fine-ground high-calcium lime.
The mixer processes the material such that the clay cleanly separates from the rock in the next process step. Thanks to this, the use of raw materials, normalized to an annual production of 365,000 t, is reduced by roughly 130,000 t. This figure corresponds to a reduction of 25%, so the resource efficiency is boosted from 65 to 70% to approx. 93%.
As an added benefit, the Combimix process reduces the energy needed for processing. The annual consumption was reduced by around 235,000 kWh and 100,000 liters of diesel. This results in a total power reduction in the order of 17%.
While MSW previously produced a maximum of 280 t salable material per hour, the supply capacity has now increased to 430-460 t per hour, despite the reduced resource expenditure.
BHS-Sonthofen GmbH is an owner-operated group of companies in the field of machinery and plant engineering based in Sonthofen, Germany. The company offers technical solutions for mechanical process technology, concentrating primarily on mixing, crushing, recycling and filtration. With more than 350 employees and several subsidiaries, BHS-Sonthofen has a global presence.
The Mixing Technology division produces batch and continuous mixers and offers the full range of process technology services for mixing applications. The twin-shaft batch mixer, which is considered a global benchmark in the concrete industry, is a key product.
Building companies use the mixers first and foremost to produce transport, precast, high-performance and dam concrete or concrete paving blocks. BHS mixers are also highly suited for mixing dry mortar, cement and sand-lime products or for processing clay-and-rock mixtures.
They are widely used for processing mineral mixes, landfill substances, fly ash, dusts or other bulk materials or for the conditioning of sludges and the production of suspensions. The latter is often done in the context of backfilling mines or depositing mineral waste.
For further information, please visit: www.bhs-sonthofen.de