Unique in Europe: Cement plant makes use of waste heat for power generation

In June 2012 the Rohrdorf cement works near Rosen-heim, Bavaria, commissioned the first power generating station in a cement plant in Europe at a festive cere­mony (Fig. 1). During the last six years the company has invested a total of 100 million € in further measures for climate protection as well as for energy efficiency, thus ensuring that the production location remains in the region in the long term [1-2].

It took six years for the conversion work in Rohrdorf and an investment in various environmental protection measures pointing the way ahead. With the festive commissioning of the waste heat power plant, the company can claim that it runs the most environmentally friendly and, at the same time, the most energy efficient cement plant in the world.

The Rohrdorf cement works is part of the ­Rohrdorfer Group that produces cement as well as ready-mix concrete, concrete products and precast concrete units at 40 locations in Germany, Austria, Italy and Hungary. They also extract sand and gravel. Heinrich Rodlmayr, technical manager of the Rohrdorfer Group, underlined in his welcoming speech the importance of the plant for the location quoting Marcel Huber, the Bavarian Minister of the Environment, “We want to be able to meet our demand for power ourselves. The Bavarian industry must not depend on the wind turbines rotating in the North Sea.” Heinrich Rodlmayr added: “Now we can say proudly that the Rohrdorf cement works will contribute to this with the new power plant.”

Power generation from waste heat

The so far unused heat of waste gases from the rotary kiln and the clinker cooler as well as the residual heat of the nitrogen oxide removal plant will be used from now on to generate power by means of a steam turbine and a generator. Based on a new process, fresh superheated steam is produced by means of the heat energy of the waste gases. This steam drives the turbine that produces the electric current via the generator. At least one third of the power requirement of the entire plant is met by the electricity produced there. The waste heat power plant is to produce a total of about seven megawatts of electric power. 12 000 t of fossil fuels will be saved and, consequently, the emission of CO2 will be reduced by 30 000 t/a. The investment amounted to 31 million €.

The innovative and environmentally friendly plant was sponsored by the Ministry of the Environment within the framework of the climate protection initiative. Furthermore, the first plant of this kind in a cement factory in Europe received the first prize in the category “Environmentally sound products and solutions” of the Siemens Environmental Award 2011. The Siemens Environmental Award is an international award given by Siemens within their branches all over the world for particularly innovative solutions in the field of environmental protection.

Measures for environmental protection have top priority

Not only the waste heat power plant (Fig. 2) newly commissioned, but also three further large projects have been tackled during the last few years to improve environmental protection and energy efficiency, although the market situation in the cement industry was not looking promising when construction activities were started. However, the partners and the management of the South ­Bavarian Portland cement works Gebr. Wiesböck & Co. GmbH have always been aware of their responsibility towards man and nature. Therefore, their protection has always had top priority. The managing director Mike Edelmann knows: “This is only possible with owners who are not looking for short-term profit, but who think in the long term.”

In 2006 they started with a new raw mill including filter plant. Setting up the SCR nitrogen oxide removal plant in 2011, i.e. a catalyser to reduce nitrogen oxides, the company was a trailblazer in the branch because no comparable process had been started before worldwide (Fig. 3).

Due to its pilot character the project was funded with 4.7 million € also by the Ministry of the Environment. Furthermore, the cement works received the second prize of the “Energy Efficiency Award 2011” of the German Energy Agency (dena) for their daring investment. The rotary kiln was also converted in 2011. A modern and energy efficient pendulum grate cooler replaced the 35-year-old planetary cooler. 10 000 tons of coal and, consequently, 28 000 tons of carbon dioxide are saved per year due to the new cooler. In the last six years the company invested a total of 100 million € for environment protection and energy efficiency. The commissioning of the power plant marks the end of the longstanding conversion phase. www.rohrdorfer.eu

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