Challenging project: SÜLZLE group provides systems for sewage sludge utilisation to Stadtentwässerung Koblenz (city of Koblenz sewage authority)

Sewage treatment plants are among the greatest municipal power consumers – they take up around 20 percent of the power requirement of municipalities. The aim of the “SusTreat” project of the municipality of Koblenz is for the local sewage treatment plant to generate this energy on its own. The operator is relying on the great potential of the generated sewage sludge, which contains large amounts of carbon that can be converted into energy through gasification. A member of the Sülzle Group, SÜLZLE KOPF SynGas GmbH & Co. KG of Tübingen, Germany, is a pioneer of this technology.

However, before the sewage sludge can be used for generating energy it must be dried. For this purpose also, a SÜLZLE system is used: the drainage and drying specialists of SÜLZLE KLEIN GmbH of Niederfischbach, Germany, provide a conveyor dryer of type Pro-Dry 4/2. This reduces the sewage sludge to a dried residue of 90 to 96%. The result is solid granulated matter, which the sewage treatment plant operator temporarily stores in a storage silo. SÜLZLE KLEIN will also install the exhaust air treatment as well as the power and heat supply of the system.

Subsequently, the KOPF SynGas system gasifies the granulated matter at a temperature of around 850 degree Celsius. In this process, organic poisons such as medication residues, hormones and bacteria are completely destroyed. The result is a flammable gas that is then cleaned of adverse substances such as heavy metals, tars and sulphur. This gas can then be used in a connected combined heat and power plant for the generation of heat or in a gas motor for power generation. The design of the SynGas system is so flexible that it can be used to only generate heat, power or both, as required.

Combined expertise for a sustainable process chain

The ashes resulting from the gasification contain minerals and phosphate. These can then be used as an agricultural fertilizer or for recovery of the valuable phosphate. This way, the high usage potential of the sewage sludge is fully utilised. This aspect also convinced the decision makers in Koblenz: “The combined expertise of SÜLZLE KOPF SynGas and SÜLZLE KLEIN offers a sophisticated and sustainable energy concept in which all elements of the process chain are optimally linked,” explained Dr. Stephan Mey, Managing Director of KOPF SynGas. This is further enhanced by the geographical vicinity: “If needed, we can be on location within an hour,” added Björn Wunderlich, Managing Director of SÜLZLE KLEIN. “This allows us to intensively support the project and react quickly.” Assembly of the system commenced in December 2014. Until 2016, the individual system components are expected to take up operation one by one.

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Bernhard Mohrs (l.), Works Manager of the Koblenz sewage treatment plant, and Björn Wunderlich, Managing Director of SÜLZLE Klein, sign the contract for the “SusTreat” project.

In the background (from l.): Thomas Keßelheim, Operations Director of the Koblenz sewage treatment plant, Dr. Stephan Mey, Managing Director of SÜLZLE KOPF SynGas, Ulrich Marquart, Deputy Operations Director of the Koblenz sewage treatment plant, Andreas Kaufmann, Deputy Works Director of the Koblenz sewage treatment plant, Head of the Municipal Building Department Martin Prümm and Joachim Hölle of the engineering company Götzelmann + Partner.