Bilfinger Berger - Power Services

The boiler of Electrabel’s power plant at Rodenhuize previously burned oil, coal and gas. But that’s about to change as Bilfinger Berger converts the plant to run on a renewable resource: From now on, it will be wood-fired.

With a screeching noise to set your teeth on edge, the crane cable slowly lifts the colossal gas preheater out of the plant. For more than twenty years, the five-meter long block-shaped device heated gas from a temperature of 40 degrees up to 300 degrees so that it could be fed back into the burner.

Lars Dörnenburg points to the black substance trickling down the sides. “It was because of this gas residue that it was time for a replacement”, says the Construction Manager from Bilfinger Berger. The crane operator sets down the old gas pre-heater and lifts the new component into place using a computer-controlled system. The complicated maneuver takes two hours.

Lars Dörnenburg and his colleagues are modernizing the Rodenhuize power plant north of Ghent, and converting it to run on biomass. Belgian energy supplier Electrabel, a subsidiary of GDF SUEZ, intends to burn wood pellets in the plant, thus generating carbon-neutral power. The project is a pioneering venture. After the conversion, the power plant will achieve a thermal output of 560 megawatts. This is the first time that a power plant of this size has undergone such a modernization. In addition to the engineering units in Oberhausen, the company also has its own manufacturing capacities for special power plant components and the largest installation team in Germany. Development, construction, manufacturing, installation and commissioning are thus all available from a single source.

It’s not only the new fuel that makes the task at Rodenhuize a challenge. Besides biomass, Electrabel also wants to be able to burn natural gas and the blast furnace gas from the neighboring steelworks.

“Burning three fuels in one boiler requires complex technology and very sophisticated planning”, explains Dr. Christian Storm, Head of Technology and Engineering at Bilfinger Berger Power Services. In the planning phase, the engineers simulated all possible scenarios on the computer to ensure that the strict limits for the emission of nitrogen oxides are complied with. Dimensions had to be reworked again and again for the ventilation ducts and steam generation components until a practicable solution was on the table and the order was all wrapped up.

Bilfinger Berger adapted 24 burners to operate with wood pellets, delivered twelve new blast furnace gas burners along with the gas preheater, renewed ventilation ducts and installed a burnout air level – a module that reduces emissions by adding extra air.

It was the first time that engineers from Bilfinger Berger had designed a biomass combustion plant of this size. Although biomass burners are similar in design to coal-burning plants with which they have extensive experience. They were faced with the task, however, of adapting the burners to deal with the significant mechanical stress from the hardwood dust. The combustion specialists soon found a simple but effective solution. They lined the burners with particularly heat-and erosive resistant ceramic plates. “During installation, the components had to be handled very carefully”, emphasizes Project Engineer Dr. Holger Oleschko. “One false move, and you could damage the ceramic protections.”

In the power plant, Lars Dörnenburg points to a transport shaft, hardly more than two meters by two meters and not something you would take note of wen passing by. “That’s the only way to get material to the boiler. Pipes, connection elements, blowers – everything has to go through here.” In the past, the plant was repeatedly converted for the use of additional fuels. That makes access more difficult today.

For their planning, the specialists relied on old construction plans which, as it turned out, were not always up to date. “There were a number of surprises waiting for us beneath the insulation”, says Dörnerburg. “But, together, we always managed to find a solution. It was exactly how I imagined a constructive cooperation should be”, confirms Frank Van den Spiegel, Project Manager at Electrabel.

“For Bilfinger Berger, Rodenhuize is an important reference project in a business that is full of promise”, says Christian Strom: “In the conversion of conventional power plants to biomass,we now have a real competitive advantage.”

(Text: Anne Meyer, Photos: Eric Vazzoler)