Walsum Unit 10, Duisburg, Germany

A 750MW hard-coal-fired cogeneration unit at Duisburg-Walsum will generate various forms of energy. Unit 10 at the power plant produces 790MW gross – made up of electricity, district heating, process steam (for a paper mill) and compressed air (for the Walsum coal mine). The plant uses advanced flue gas desulfurisation.

Net efficiency will be above 45%, about 5% higher than other German coal-fired power plants. This increase comes in part from advanced material allowing higher boiler steam pressures and temperatures. An efficient 181m tall cooling tower allows high steam energy utilisation in the turbine.

The plant is being built by energy company Steag and infrastructure company EVN, with EVN and EnBW Energie Baden-Württemberg buying the electricity. It will supply enough electricity for a city of half a million people.

Costing around €800m, the plant will take 3 years to complete. Commissioning is planned for autumn 2009, with start of commercial operation in 2010.

ENVIRONMENTAL PROTECTION MEASURES

Air pollution control includes flue gas desulfurisation (FGD) systems. Hitachi uses the quicklime and limestone process to remove sulfur dioxide from the flue gases. The gas is then cooled to saturation temperature in a flue gas scrubber and cleaned with a slurry suspension injected in the counter stream.

The cleaned flue gas is discharged to the atmosphere through the "wet" stack or cooling tower after being heated in a gas/gas heat exchanger through a "dry" stack. The limestone needed for desulfurisation is normally stored on the site and turned into a limestone slurry in a limestone treatment process. Gypsum is dewatered and sent to the manufacturing industries.

Hitachi uses selective catalytic reduction (SCR) after combustion to practically eliminate NOx pollution. SCR is normally used between the economiser and air heater. Ammonia/ammonium hydroxide is injected and blended, followed by processing in a nitrogen oxide reduction (DeNOx) reactor with rectifier and sootblower.

Catalysts are at the heart of the DeNOx process, with processes using either plate or honeycomb types. The system uses the ammonia and catalysts to convert the oxides of nitrogen into water and nitrogen. Ash particles and dust cling to electrically charged plates in the electrostatic precipitator.

Cleaned flue gases are carried away in a flue gas duct via the cooling tower, so the plant needs no stack.

CONSTRUCTION AHEAD OF SCHEDULE

Construction began ahead of schedule. Steag (51%) and EVN (49%) awarded the contract for the turnkey construction to Hitachi Power Europe GmbH (HPE) of Oberhausen, Germany. The supply includes a steam turbine and generator, a large-scale steam generating unit, environmental protection equipment, and structural and civil engineering work including a cooling tower. It is also handling overall plant engineering (which is based on a Steag design).

The plant in Duisburg-Walsum is the first in Germany to be ordered as a "complete package". It will have considerable impact on employment in North Rhine-Westphalia, and the Ruhr district in particular. Roads and much other infrastructure will be provided by regional companies. After earth-moving, the first few months saw the foundations for the individual sections of the plant (boiler, cooling tower and so on). The pillars and individual sections will be followed by first boiler support in the summer of 2007. Construction will see up to 1,000 jobs, with around 60 more long term at the plant.

ORGANISATION AND FINANCE

Steag GmbH is a wholly owned subsidiary of RAG Aktiengesellschaft, and is the fifth largest German power generator. Its core business is power generation in hard-coal-fired power plants (eight in the Rhine/Ruhr region and the Saarland; three abroad), in industrial power plants, and in decentralised energy supply installations. The total installed electric capacity, nationally and internationally, is about 9,000MW. In 2005 the 4,900 employees generated around €5bn in revenues.  

Steag maintains its use of hard coal instead of natural gas at Walsum is based on secure long-term electricity production from a guaranteed supply of hard coal, which is not subject to the price fluctuations of oil and gas.

EVN AG is a listed Austrian energy and infrastructure company which supplies electric power to three million customers in Europe. Controlling shareholder with 51% is the province of Lower Austria. The EVN Group offers its customers electricity, gas, heat, water, heat recovery incineration and related services.

The company relies on a flexible production mix combining water and thermal power with alternative energy, and currently has a production capacity in Lower Austria of some 1,600MW.

Through wholly owned subsidiaries the company is active in the water and waste-to-energy business in Austria and eleven other Central and East European countries.

KfW IPEX-Bank, IKB and Helaba are providing €615m ($785m) in finance. EVN and EnBW are headquartered in Austria and Southern Germany, but deliver electricity in the Ruhr district and elsewhere.

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