Belt Drying Breakthrough

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 installations 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.

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Read the article online at: https://www.worldcement.com/special-reports/18062025/belt-drying-breakthrough/