Yves-Marc Schade, stela Laxhuber GmbH, discusses how tailored belt drying solutions are transforming waste heat into a
strategic asset for sustainable cement production.
The SCHWENK cement plant in Allmendingen prioritised the efficient utilisation of previously unused waste heat from the production process. This excess thermal energy, which would otherwise dissipate into the environment, presented an opportunity for operational efficiency and sustainability. At the same time, the plant was looking to efficiently dry its substitute RDF (refuse derived fuel) to improve its calorific value and enable more efficient combustion.
However, the space available for the belt dryer was highly restricted. SCHWENK had determined that a belt width of 6.2 m was optimal, based on instalations at other company sites. Integrating this equipment into a limited footprint posed a significant design and engineering challenge.
The need to integrate advanced drying capabilities without expanding the facility’s footprint reflects a broader trend in the cement industry, where modernisation efforts must align with ageing infrastructure. Stela’s ability to provide a tailored drying solution underscores the importance of flexible engineering in legacy plant upgrades.
In cement production, waste heat is often an overlooked resource. Effectively capturing and using this energy can reduce operating costs and greenhouse gas emissions, while also stabilising thermal processes.
The Allmendingen project exemplifies how industrial plants can turn site-specific limitations into innovation opportunities. Rather than downsizing the system or sacrificing efficiency, stela engineered a high-capacity dryer to fit the constraints. This project also reflects the evolving role of process integration, where heat recovery, emissions control, and fuel handling are no longer isolated systems but part of a unified design strategy.
Solution
To overcome the space limitations, stela implemented a custom configuration: the exhaust air fans were placed behind the dryer and linked to shafts routed beneath the belt system. This unorthodox layout enabled full integration of the dryer within the spatial constraints of the site.
The dryer was also constructed on an elevated 2 m strip foundation to integrate seamlessly with the customer's essential infrastructure. It utilises waste heat from the clinker cooler; previously, one-third of the hot air was vented unused into the atmosphere, representing a significant energy loss. Now, this energy is harnessed to dry RDF, which primarily consists of shredded plastics and serves as a lower-emission alternative to coal in the rotary kiln.
This waste heat recovery not only improves the site’s energy efficiency but also reduces its overall carbon footprint. "By repurposing thermal energy that would have otherwise been lost, the plant achieves meaningful emissions reductions and aligns with broader environmental regulations", says Daniel Werkstetter, responsible project manager.
The dryer’s modular design and adaptability were key factors in the project’s success, offering a repeatable solution for other constrained industrial environments. Such installations exemplify how cement producers can modernise core operations without the need for new construction.
The integration of RDF drying with clinker cooler waste heat has multiple cascading benefits. It minimises the need for auxiliary fuel sources, enhances fuel flexibility, and supports the use of lower-quality waste-derived fuels. By ensuring that RDF is consistently dried to the correct moisture content, combustion stability is improved, leading to improved kiln performance and reduced maintenance requirements.
Moreover, the project illustrates how custom drying installations can act as both environmental upgrades and productivity enhancers. The engineering team had to reconcile airflow dynamics, structural load distribution, and energy flow modelling to ensure that system performance remained optimal, even in a non-standard layout. Such site-specific solutions demonstrate the versatility of belt drying technology and its ability to adapt to a range of plant configurations and project goals.
Production and assembly
The belt dryer was fabricated at stela's manufacturing facility in Massing, Germany. Each component was produced according to stringent quality standards.
Assembly at the Allmendingen site took place in close coordination with SCHWENK. Local conditions and client specifications were factored into all phases of the assembly. Special considerations included aligning the dryer within existing spatial limits and integrating it with the site's energy and automation systems.
Meticulous planning in the pre-installation phase ensured that every step – from delivery to commissioning – proceeded on time and without complications.
The success of the installation is also a testament to cross-functional project management. Engineers, plant operators, and construction teams worked in parallel to resolve challenges in real time. This holistic project approach reduced installation timeframes and provided valuable insights for future deployments in similar spatially constrained industrial sites, particularly in retrofit scenarios where footprint limitations are common.
Conclusion and outlook
As one of Germany’s most respected cement producers, SCHWENK Zement maintains strict standards for product quality and operational reliability. The drying parameters of the stela system are precisely controlled to ensure that these standards are consistently met.
With the Allmendingen site now operational, all major SCHWENK locations – including Bernburg, Karlstadt, Heidenheim-Mergelstetten, and Broceni, Latvia – utilise stela belt drying technology. This reinforces a company-wide commitment to energy-efficient fuel preparation.
The new installation is part of a larger energy optimisation strategy at Allmendingen. Alongside the RDF dryer, the site includes an ORC (organic Rankine cycle) system for electricity generation and a downstream heat recovery unit for hot water production. Together, these systems enable the site to save over 8.5 million kWh/y of energy and avoid more than 13 200 t of CO2 emissions.
The project showcases how drying technology can serve as a strategic lever for decarbonising cement production. It highlights low-temperature belt drying technology’s role in enabling plants to operate more sustainably while enhancing process stability. As regulatory and energy pressures increase, such solutions will become central to future-ready industrial design.
This case shows how belt dryers can contribute not just as auxiliary systems but as core enablers of next-generation cement manufacturing strategies, supporting goals for decarbonisation, energy recovery, and circular economy alignment.
World Cement, June 2025
