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Enhanced safety and lower emissions using CFD

One of the leading energy companies in the Nordic countries and elsewhere around the Baltic Rim, Fortum has made extensive use of Computational Fluid Dynamics (CFD) in R&D work on its power generation processes.
Fortum Corporation

Fortum is committed to ensuring that its operations are as environmentally friendly and as safe as possible – and continuously carries out research on new and innovative ways of cutting the emissions and enhancing the efficiency and safety of its generating facilities.

One of the key methodologies used by Fortum in this work is Computational Fluid Dynamics (CFD), the process of mathematically modelling how fluids flow in different spaces.

Fortum has employed CFD since the early 1980s. It has proved particularly useful in the nuclear field, but has also proved its worth in developing better combustion processes for coal- and peat-fired power plants.

Safe, targeted modifications at Loviisa

Fortum has used, and continues to use, CFD calculations to simulate enhancements to its Loviisa nuclear power plant prior to implementation. CFD has been found to be an invaluable tool in accident simulation and analysis work, in particular, in cases where actual or experimental testing is not possible.

Finland’s first nuclear power plant, which came on stream in 1977 and 1980, generated 7.74 TWh in 2004. Built to meet the highest Western standards of the time, the safety performance and operability of the two reactors have been steadily enhanced over the years through a series of extensive projects.

Sophisticated computational models created with the help of CFD have made the design of the actual experiments needed as the basis for these projects both easier and more accurate, and have reduced the number of field trials necessary.

One of the most extensive areas where Fortum has applied CFD at Loviisa has been the plant’s life-cycle management. One recent CFD study focused on simulating the behaviour of water droplets in steam flows, for example. The results of this CFD work enabled the phenomenon, which is an important factor in the erosion of steam pipes, to be modelled very precisely, and made it possible to plan maintenance work more accurately.

NOx emissions halved at Haapavesi

In line with stricter EU environmental regulations, Fortum has been looking at ways of reducing emissions, and nitrogen oxide (NOx) emissions in particular, at its Haapavesi power plant, the world’s largest peat-fired condensing power plant – also with the help of CFD.

Built in 1989, the Haapavesi plant is capable of generating a maximum output of 154 MW from between two and three million cubic metres of peat a year.

High combustion temperature is a key factor in reducing NOx emissions when burning peat, but achieving sufficiently high temperatures with Haapavesi’s standard burners proved impossible.

This problem could have been overcome with the help of secondary NOx reduction techniques, in the shape of selective catalytic reduction, but the investment costs associated with this are very high. As a result, Fortum’s R&D people concentrated their efforts on looking for a solution that would reduce NOx emissions during combustion. The only problem was that there were no commercially available technologies for doing this.

Working with VTT Technical Research Centre of Finland, Fortum used CFD to calculate how remodelling the burners could increase the combustion temperature. After the computer model had produced the desired results, Fortum’s engineering team built a new set of burners and validated the computational model under test conditions.

The test results matched what the model had predicted exceptionally well, and the new burners resulted in the boiler generating between 40% and 50% less NOx emissions than before. Six new burners were installed in 2005, and another six will be installed in 2006.

Fortum has designed new burners to cut NOx emissions at its Haapavesi peat-fired power plant with the help of CFD data. The flame pattern and ammonia concentration of the old burner and the new burner can be seen here.

World-class expertise

The rapid improvements that have been seen in computational capabilities in recent years has made CFD an ever-more useful method for experimental work and system code simulation – whether in life-time management and accident analyses or in reducing emissions in coal- and peat-fired power plants.

Drawing on its extensive experience and expertise in CFD, Fortum has been able to make its own power generation both safer and friendlier to the environment, and offers this know-how to customers in selected markets internationally. Close cooperation with international organisations and institutes of higher education also means that Fortum’s know-how is available to the scientific community as well.

A CFD model simulating the flow and pressure in a reactor coolant pump at the Loviisa nuclear power plant. The effect of modifications was simulated using the model prior to actual work being carried out.
> Pauliina Henttonen
(Published in High Technology Finland )