Dillinger Hütte’s 40-year-old sinter cooler modernized to be fit for the future

A new dedusting system for the circular cooler with an integrated heat recovery system increased the efficiency and decreased the environmental footprint of Dillinger Hütte’s sinter plant 3. This environmental project has not only made the 40-year-old sinter cooler available to operate in the coming decades but has also helped Dillinger Hütte take a step towards reducing their CO2 emissions. New, efficient heat recovery allows carbon emissions to be reduced by approximately 25,000 tons per year while cooler dedusting significantly decreases dust emissions from the circular cooler.  

Dillinger Hütte is a steel producer in Dillingen, in the federal state of Saarland in Germany. The company has a history spanning more than 300 years, with its plant founded in 1685. It is Europe's largest heavy plate producer. The total production of the company is around two million tons of heavy plate annually in a thickness range extending from 6 to 440 mm. The company’s product range includes heavy steel plate, cast slag pots, and semi-finished products that are used for the fabrication of drilling rigs, ships, petrochemical plants, bridges, and heavy machinery. Dillinger Hütte works strategically towards the goal of carbon-neutral steel production. 

Metso Outotec’s relationship with Dillinger Hütte extends back to the 1950s. In 1955, 1958, and 1980 Metso Outotec’s predecessor Lurgi delivered three sinter plants for the company’s steel plant. Over the last decades Metso Outotec and its predecessors have continued to provide maintenance and retrofits to the sinter plants. 

Aiming for sustainable performance 

Two of Dillinger Hütte’s sinter plants had been producing a reliable feed for the blast furnaces, but sinter plant 3 had to be optimized consistently. In addition to the need to improve the availability of sinter plant 3, the company wanted to make improvements, for example, in the plant‘s energy consumption and emissions levels. 

This is where Metso Outotec stepped in to support the company to find a sustainable solution. The co-operation started with a comprehensive study to design the required equipment to implement the planned improvements. With the final decision of our customer to implement the identified measures, Metso Outotec entered into a partnership with the brownfield specialist Küttner from Germany. Based on the long-term experience of Metso Outotec in sinter technology and process and plant engineering and the vast experience of Küttner in the fields of heat recovery, gas cleaning, and automation an entire integration concept was developed.

The key actions included, for example, retrofitting the cooler at the sinter plant for maximum efficiency.  Outdated and inflexible axial cooling air fans, which had low energy efficiency, were also replaced.  Another important aspect of the upgrade project was the evaluation of the possibilities for waste heat recovery to generate hot process water in order to reduce the environmental footprint.  

It was also important to comply with the new emission limits of the European Industrial Emissions Directive (IED), which commits plants in the European Union (EU) to control and reduce industrial emissions. 

Results with thorough studies and accurate design 

Metso Outotec supported the customer for more than five years in this complex project – from the very first idea to the final modernization of the old sinter cooler and the implementation of a waste heat recovery system.   

In 2015, Metso Outotec experts carried out a comprehensive study to evaluate the potential for cooler modification and reduction of emissions as well as different possibilities for waste heat recovery. For this, Metso Outotec designed a small mobile hood to measure gas volume, temperature, and dust load in the different sectors of the sinter cooler. By means of infrared cameras, heat distribution in the sinter bed in the cooler was investigated.  

Based on the results, Metso Outotec studied different scenarios to utilize the waste heat of the sinter cooler in the generation of electrical energy or hot water and in other areas. Dillinger Hütte decided that hot feedwater generation for the power plant would be the most economical approach. Heat recovery now generates an additional 82,000 MWh of energy, and this equals a reduction in carbon emissions of approximately 25,000 tons per year. 

In close cooperation with Küttner the cooler modernization was implemented in 2020. The upgrade included an extended hood with a dust absorber and an additional booster fan for gas cleaning as well as new cooling air fans and a waste heat boiler. The modern radial fans with variable speed drive control are more energy efficient. By always operating the cooling air fans at the minimum required speed, it is expected to save up to 20% of the energy consumption in the long run. The new dust absorber system allows the dust level in off-gas to be continuously kept below 5 mg/Nm³. 

Cooperation to benefit the environment 

Thanks to the good collaboration between and the leading expertise of Metso Outotec and Küttner, the 40-year-old sinter cooler is now fit for the coming decades and meets both the EU’s and the company’s own  emission limitation and energy efficiency targets. 

"With the new circular cooler dedusting system, we have successfully created a win-win situation for the environment and efficiency. The energy gained from heat extraction reduces carbon emissions and generates more electricity that does not need to be purchased. At the same time, dust emissions are being further reduced and recycled. We are thus continuing our efforts to ensure that the most sustainable steel companies are located at the Saar river,” said Martin Baues, Chief Technical Officer of Dillinger and Saarstahl. 

Metso Outotec’s predecessor Lurgi and Dillinger Hütte already built good co-operation decades ago. Lurgi had been the frontrunner in sinter technology since the introduction of this technology in 1910. Lurgi and later Metso Outotec have stayed in contact with Dillinger Hütte for the new plants, technical exchange, and the required continuous modernization of the assets. This way, Dillinger Hütte gets the maximum benefit from Metso Outotec’s latest technology developments and its end-to-end, sustainable solutions combined with solid process expertise. 

In the last boom years of the steel industry at the beginning of the 21^st century, Metso Outotec has delivered 17 sinter plants in Brazil, Africa, and India. These plants are the most advanced with regard to productivity, energy efficiency, emission control, and automation. Read more about Metso Outotec’s sintering solution.