ANDRITZ
INDUSTRY NEWS
to produce as much electricity as possible at a given district heat demand. For this, we worked with them to develop a tailor-made solution to boost the electrical output without increasing the steam parameters in the plant”.
The boosting of electricity production is accomplished with Andritz’s Cyclex system (previously called a Heat Shift System). By utilising certain features of the Cyclex system, it is possible to replace the bleed steam from the turbine that was formerly used for preheating condensate and instead use this steam for maximising the turbo- generator’s electrical output. “In addition to making the process more efficient, it also made the boiler plant design simpler and improved control of the boiler process,” stated Slotte. “With the Cyclex system, you don’t need flue gas-to-air preheaters. This gives added flexibility and simplifies the layout. Also, it was possible to
use a low-dust catalyst after the bag filter, which is a very cost- effective way to reduce NOx emissions.”
The plant has a flue gas condenser system after the flue gas fan and a combustion air humidifier upstream from the combustion air fans. In this way, the latent energy in the flue gas is recovered and transferred to the district heating water. “This plant is really optimised for maximum overall efficiency, as well as electric output,” said Slotte. “It produces as much district heat as possible and then uses the remaining district heat load demand to produce as much electricity as possible.” Andritz delivered the complete boiler island, from fuel bin to flue gas fan outlet. The BFB design is efficient at burning wood-based fuels, including forest residuals, sawmill chips and bark. The new plant has created a number of win-win-win
scenarios when it comes to NOx emissions and puts Karlstads Energi right up there with the top producers in the country. Thelander reported, “We are now one of the top five plants in Sweden for efficiency. This year, we will be below 10 mg/ MJ of NOx emissions, which rewards us with about SEK 3 million (300,000 Euros). Andritz really helped us to achieve this with the Cyclex and Selective Catalyst Reduction systems”. The project ran very smoothly. “We were spot on with this installation from the very beginning,” said Thelander. “We are also delighted that the overall project came in at about 15% lower than we budgeted for.
“The installation and
commissioning was challenging in that there were a number of suppliers on-site at the same time,” added Hannu Ylönen, Andritz Project Manager. “Making sure that work was conducted safely and that
This chart illustrates the changes in fuel sources for Karlstads Energi’s Heden plant. The benefits of applying high steam parameters and the Cyclex system are higher electricity-to- heat ratios (28.2 MW/52 MW = 0.54). The downstream flue gas condenser ensures a very high overall efficiency of 116% (calculated using the effective heat value of the fuel and excluding auxiliary power consumption).
10 10 Summer 2016
everything came together took considerable planning and good collaboration with Johan’s team and the other suppliers.” However, he noted that the project flow and on-site co-operation with the team at Karlstads Energi was well organised and the project was conducted in a very friendly and constructive atmosphere with suppliers and sub-contractors working well with each other. Karlstads Energi decided to bring in some state-of- the-art project management tools to make sure that any potential interference or clashing scenarios were seen way in advance by the use of 3D modeling. “The 3D modeling was a real plus for this project,” said Thelander. “We combined the 3D models from all the suppliers into one common 3D model and could see where all their different pipes, wires and hardware were to be positioned. By doing this in a virtual way, we could sit together and make adjustments before the installation began. It was also a fantastic tool when
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