During decades the Danish industry of energy producing equipment has been pushed for achieving higher and higher goals. The pressure has been made from the shifting governments in order to release Denmark from import of energy to becoming independent.

The results have been shown in many ways. These years the most visible effect has been the renewable energy market. There are however other technologies which earlier has proven its CO2 and emission reducing capabilities.

In 2003 Aalborg Engineering was awarded the heat recovery boiler for the new block 8 on H.C. Ørstedsværket in Copenhagen.  The plant would be a part of a master plan for the complete district heating system of the capitol. Basis for the plant was a gas turbine (Today known as a Siemens SGT 600) which was moved from Næstved to the site in Copenhagen.

In order to meet the required capacity the gas turbine had to be equipped with a heat recovery boiler with the possibility of increasing the production considerably. During the project study Aalborg Engineering worked closely with the plant owner to make the best technical and feasible solution. The result was a heat recovery boiler with a high degree of supplementary firing using natural gas.

In this solution we made it possible to increase the basic gas turbine load with additional app. 60 MWt. The parameters were defined as low pressure steam for the Copenhagen district heating system as well as district heating water. The plant was defined to have approx 500 annual operating hours. Not much compared to the work carried out and investment made. But still the installed capacity had to cover for the expected ambient conditions of the city and to make sure there was sufficient heat for the consumers.

The plant was installed in an old power plant building. This fact required extraordinary efforts to avoid making any changes to the old building which is considered worth preserving. The installation was made through the basement and access ports just below roof level. The plan succeeded and today a modern efficient plant is producing heat for the city of Copenhagen.

Speaking about efficiency there are some quite interesting operational features the heat recovery boiler is build for. As mentioned it was expected to use the installation for approx 500 hours per annum. Today after five years of service the plant has become base load. That means the plant is scheduled to operate all the time. Due to the combination of producing power and heat this is the most feasible installation of the system. The heat recovery boiler has efficiency as high as 98 % when the plant is on full gas turbine and supplementary firing mode.

Indeed an achievement which is difficult to speak against even in a time where fossil fuels in general is considered problematic. Let this be a good example of the climate friendly fossil usage.

That is how efficient it can be!