Aurubis AG scores with waste heat utilisation

Winner of the Energy Transition 2.0 category. Use of industrial waste heat for internal processes and the heating of a city district.

Adolf Gottfried Tonwerke and Orcan Energy tap waste heat from kilns

The family business Adolf Gottfried Tonwerke GmbH extracts and refines clay and other raw materials for the ceramic and clay processing industry in Grossheirath, Bavaria. After the successful implementation of energy efficiency measures, the company pursued the goal of extending the use of waste heat, which had already been implemented but was limited to production, to the firing processes as well. The focus was on two rotary kilns for firing the clay. With as few changes as possible to the existing process, the high exhaust gas temperatures of the waste heat generated there were to be made usable.

The cooperation with Orcan Energy AG offered a suitable solution. The company, which specialises in ORC (Organic Rankine Cycle) plants, took over the planning and implementation of an ORC module in the plant. Due to its flexible behaviour, it can react to fluctuating heat quantities within seconds and achieves a high degree of efficiency in the conversion of heat into electricity even at partial load. In addition, the ORC module is characterised by a second high-temperature circuit and can therefore also generate higher temperatures in the waste heat flow.

A technical challenge in the project was the integration of the ORC units into the existing rotary kiln system. For example, an exhaust gas heat exchanger (AGWÜ) had to be additionally installed in the exhaust gas flow of furnaces 1 and 2. A high dust content in the exhaust gas made the situation more difficult. The solution was finally found in an exhaust gas heat exchanger specially designed for this application. Its operation made the ORC solution possible and reduced the utilization factor of the suction fan, which saved another 15 kW of energy. The achieved savings are proven by an integrated control system which continuously measures the generated electrical power.

The jury selects Adolf Gottfried Tonwerke GmbH as the winner of the Energy Efficiency Award 2019 in the category Energy Turnaround 2.0. The members of the jury are convinced that the company, in cooperation with a manufacturer of ORC systems, has succeeded not only in sensibly tapping the waste heat of an energy-intensive firing process, but also in showing an innovative way to successfully use dust-laden exhaust gases. This is a challenge that in many companies is opposed to the use of waste heat. The use of industrial waste heat is an essential component for increasing energy efficiency and reducing CO2 emissions. The economic attractiveness of the project could be increased even further by using the BMWi's industrial support programme.