Investment in sustainability
New filter system for Stahlwerk Bous
It is a clear sign of commitment to the production site in Bous as well as an important indication of how compatible in future steel production and environmental protection can become in Germany: the installation of a new filter system at Stahlwerk Bous, which has now been commissioned.
At 560,000 cubic meters of exhaust air per hour, the capacity of the old system was already impressive - but the new system with a capacity of 1.3 million cubic meters per hour is clearly superior. The new technology also makes further output increases possible in Bous’ three-phase electric arc furnace, which produces up to 70 tonnes of steel per melting process. The dust content in the elaborately filtered exhaust air is reduced to less than 1 milligram per cubic meter, corresponding to just one fifth of the legally permitted limit value of 5 milligrams per cubic meter.
In the interests of transparency and active dialogue with the public, it is intended to publish the values measured online on the website of Stahlwerk Bous (www.stahlwerk-bous.de) in the foreseeable future. The heat absorbed in the suction process is also used: The system’s whole water management is connected to the operational district heating system via a heat exchanger.
The commissioning of the new filter system also presented considerable technical challenges, however: In the 1980s, when the old system went into operation, chimneys were not a strict requirement and the exhaust air was released into the environment via a diffusor. Today, chimneys with a height of 50 metres are mandatory in the Saarland as a way of reducing pollution levels. It was not possible to connect such a chimney to the old system. On account of the increased output at the steel plant, a more powerful dust extraction unit was necessary. To incorporate the significantly bigger hood above the furnace and the enormous exhaust ducts with diameters of up to 4.3 metres, it was necessary to develop a sophisticated structural engineering concept because the steel plant building could not support the new loads. A 50-metre-long and up to 20-metre-wide steel bridge was erected over the roof of the building, from which the loads of the filter system were hung. The design of the system is extremely progressive: the hot furnace exhaust gas is completely burned in a post-combustion chamber. This process destroys the pollutants. Subsequently the gas is suddenly mixed with cold air – a process known as “quenching” the exhaust gas. The extraction of the gases and the confluence have been optimised by means of CFD simulations. The filter housing is made of pre-cast concrete elements. This offers three advantages: The filtering is sound-proofed on the outside and thermally insulated on the inside. The flow-optimised guidance of the gas in the filter guarantees an extremely low level of pressure loss, with the result that the energy consumption for the ventilators is as low as possible. The steel plant therefore has more extraction capacity than planned, which provides for a better climate at the workplace. The concept and design of the system is the most modern in the world.
“The investment in the new dust extraction unit, involving a sum in the low double-digit million range, is a clear and conscious sign of commitment to the future organisation and further development of our steel plant site in Bous. Particularly in times such as these, which are characterised by stiff - and sometimes even unfair - competition in the global steel industry, we are extremely aware of our responsibility both to people and the environment", says Franz Josef Schu, Managing Director of Stahlwerk Bous GmbH. "In order to ensure sustainability at the Bous site, we are pursuing constructive dialogue with the responsible committees in order also to improve infrastructural accessibility to the site."
Stahlwerk Bous employs 350 persons and in 2016 generated turnover of almost 217 million euros. The company is part of GMH Gruppe, which focuses on steel production and steel processing and is also involved in forging technology, railway systems and casting. GMH Gruppe currently employs a total of 8,500 persons across the world.