Energy from Waste

Utilised to the very last step

The thermal treatment of waste leaves behind material residues in the form of ash or slag. Depending on the type of combustion, this represents approx. 20 % of the raw waste quantity. A large proportion of the slag can be recycled. Today, up to 95 % of the metallic raw materials in waste can be recovered by the treatment of slag. The rest of the slag can be used for road construction or landfills. At Steinmüller Babcock Environment we rely on leading-edge processes for extracting slag, and provide both wet and dry deslagging.

Decades of experience and countless projects have made us into specialists for slag extraction systems from the firing chamber, and for dust extraction and transport systems from flue gas cleaning. We have developed our own technologies for this purpose, and combine these perfectly with the techniques of other experts. We have developed hydraulically-driven ram slag extractors especially for extracting slag from the firing chambers of waste incineration plants, which also safely extract larger impurities or incombustible waste components. The robust and reliable construction allows low-wear operation with long lifetimes. 

Wet deslagging is currently one of the most commonly used methods. Here, the hot slag at the end of the combustion grate is fed into a water bath. The aim is to cool the slag and extinguish any remaining embers. The soaking reduces the dust pollution to a minimum in the subsequent stages. The water in the process generates an alkaline environment, which can lead to reactions among the base metals contained in the slag. The slag, enriched with water, is fed at fixed time intervals via ram slag extractors and conveyer systems to the slag bunker. The later treatment process starts here, including an ageing process that lasts several weeks. While the wet deslagging process is stable and robust, it does not achieve the maximum possible resource recovery. The water leads to the binding of fine-grained slag particles, meaning that the fine slag is lost to the treatment process. The recovery quota is approx. 90 %.


Since dry deslagging does not use any water, the metals do not become silted, and there are no reactions in the alkaline environment. It was the most widespread system in Europe until the 1990s, but was increasingly replaced by wet deslagging due to high dust pollution. Today’s reformed technology produces low dust quantities, using system-wide negative pressure and cyclones. Dry deslagging facilitates resource recovery of up to 95 %, including the treatment of fine slag. In dry deslagging, all of the materials and particles remain in their original state, allowing categorisation by shape, size, weight, and conductivity. The process enables a better use of energy by recovering the heat from the slag via the combustion air, and due to a better burn-off. The system is robust and safe, combining low capacity and monitoring needs with low wear, a long lifetime, and low costs for maintenance and repair.

Talk to us! We will be happy to advise you on which system will benefit you the most.

Up to 95 % of resources in the slag can be recovered

Up to 95 % of resources in the slag can be recovered  

Steinmüller Babcock Environment GmbH

Fabrikstraße 1

D-51643 Gummersbach, Germany

+49 (0) 2261 85 - 0

+49 (0) 2261 85 - 2999

info@steinmueller-babcock.com