In August 2006 a consortium comprising Hitachi Power Europe GmbH (HPE) and GE Energy signed an agreement with Eon Gasturbiner Sverige to build a turnkey combined heat and power (CHP) plant in the Swedish town of Malmö. Incorporating state-of-the-art technology, the new CHP Öresundsverket power plant promises to be one of the most modern cogeneration plants in the world.

The power plant has been designed for more than 7000 hours of annual operation, with an electrical capacity of approximately 440MW, and more than 250MW of thermal heat generation. Under combined operations it will have a maximum gross fuel utilisation of over 89percent.

At the time of signing a very tight project time schedule was agreed upon, with the construction time for the CHP plant being 28 months, and a commercial operation date of the beginning of 2009.

Power train design

The CHP power train will consist of one GE gas turbine type 9FB, one condensing-extracting steam turbine and one vertical heat recovery steam generator (HRSG). The main components will be arranged in a multi-shaft arrangement.

The fuel for the gas turbine is a high caloric natural gas, with a light fuel oil, serving as back up fuel.

During condensing operation mode the power plant will have a net electrical power output of 447MW, of which the gas turbine will generate 293MW, and a heat consumption of 767MJ/s, resulting in a top net electrical efficiency of 58.3percent.

The hot flue gas leaving the gas turbine is used to generate steam in the HRSG, which will produce 310t/h of live steam. The steam will be used to operate the steam turbine, generating a maximum electrical power output of 161MW.

Approximately 5000 hours of district heating per year is required for Malmö city, so the steam turbine can be operated in extraction mode to generate 250MW of thermal heat.

To get the maximum flexibility from the CHP plant, and to avoid the start-up of other heat production units in the district heating system, it will be possible to produce 408MW of thermal heat for peak load operation by shutting down the steam turbine and feeding the district heating heat exchanger directly with steam from the HRSG.

The CHP is expected to generate approximately 3TWh of electricity and around 1TWh of thermal heat per year.

Challenges faced

The biggest challenge of the project is that the CHP plant is to be installed within an existing building, and that components and equipment located outside of the existing building are to be kept to a minimum.

The original Öresundsverket power plant was built in three stages between 1953 and 1964, and used coal and oil fired boilers for electricity and heat production. The plant is located in an industrial and harbour area in Malmö.

To be able to build a power plant within an existing building special attention needs to be made to the layout of the CHP during the design phase.

This is to ensure the best possible use of the building’s existing structure with respect to space and arrangements for erection, daily operation, maintenance and overhaul.

Plant technology

To be able to reach the required power output and efficiency it is necessary to build the power plant using high quality and highly efficiency equipment. The main component of the power plant is the GE gas turbine type 9FB.

Behind the gas turbine a triple pressure HRSG with reheat will be located.

To fulfil the strict emission regulations of 15mg/MJ fuel for NOx operating on natural gas, the HRSG is equipped with a selective catalytic reduction system, working on aqueous ammonia. An auxiliary boiler supplies steam for start-up.

The steam turbine is a three casing condensing-extracting turbine connected with a ‘one-pass’ condenser with titanium tubes because the cooling medium is sea water.

Because of a gas turbine power output of more than 281MW during ISO-conditions the gas turbine generator is hydrogen-water cooled. For the steam turbine power output an air/water cooled generator is sufficient.

To provide the necessary demineralised water for the water/steam cycle and the gas turbine during operation on liquid fuel oil, a water treatment plant will be supplied.

A second water treatment plant will be erected to compensate for any losses in the district heating system of Malmö city. In order to maintain the pressure of the district heating system, a pressure control system will be provided.

The CHP plant’s distributed control system (DCS) is located in the control room. It handles the overall plant control functions, monitors the field instrumentation and controls the auxiliary systems. Due to the high automation standard only one operator is necessary to control the entire CHP plant via the DCS.

Project status

HPE is the consortium leader and has responsibility for the overall design of the CHP plant. In addition, the company will execute the civil works, the installation, the commissioning and supply the balance of plant and electrical equipment. GE Energy will supply the gas turbine and steam turbine generator set, as well as the HRSG and the DCS.

In nine months the gas turbine will have its ‘first fire’, starting the hot commissioning phase for the CHP plant and ending in a trial run with a performance test to demonstrate that the cogeneration plant fulfils the agreed operating characteristics and performance.

Olaf Lipinski is with Hitachi Power Europe, Germany. www.hitachi-power.com