In the center of Stockholm there is one of the world's largest biomass-fired power plants, producing annually about 3,000 GWh of energy. This is enough to heat about 190,000 households. Stockholm Exergi is owned in equal parts by Fortum and the City of Stockholm. The plant in Värtan is exceptional, e.g. due to its central location. In addition, due to its large size, the power plant will play an important role in helping the City of Stockholm to meet its climate goals. Almost all the Värtan’s energy production is done from renewable energy sources. However, the power plant's functions must be constantly developed in order to make production more energy efficient.
Fuels arrive at the Värtan power plant by ship, train and truck. In 2018, a project was started at the Värtan power plant, which resulted in the installation of automatic sampling equipment for the acceptance inspection of fuels arriving by train and ship. There was a desire to pay more attention to fuel quality so that energy efficiency and occupational safety could be improved. Of course, it was also desired to take the samples as representatively and automatically as possible.
Insight of biomass
“By taking samples from different suppliers and storing them separate from each other, we have a much better understanding of the quality of fuel from each supplier. We have gained important insights into our fuel quality, says Rainer Korkiamäki”, Port Manager at Stockholm Exergi.
As a rule, the Värtan power plant receives an average of one train carrying biomass fuel per day. The train has dozens of wagons and nearly a hundred containers of biomass from various suppliers. It was decided to place the automatic sampling equipment in the same hall, where the unloading equipment of the train containers is also located. At the same time as the train’s container is lifted into the air and emptied into the fuel unloading pit, an automatic sampler, Q-Robot, drills the samples from the next container in the unloading turn. As the train moves, the Q-Robot drops the collected samples into a tank, from where they are later taken to the laboratory. The Q-Robot then returns to take a sample from the next container. The entire sampling process is automated.
Automated sampling - Simpler and smoother way
The automatic sampler was taken into production in October 2019. At the Värtan power plant, Q-Robot takes thousands of samples of fuels arriving by train every year.
“The automatic sampling works very well and has replaced at lot of manual labor. Our staff used to do all sampling manually, using a lift to gain access to train carts. We did this outdoors and in all types of weather conditions. The Q robot solution is a simpler and smoother way of taking necessary samples”, says Rainer.
Q-Robot does both, sampling, and the most parts of sample handling fully automatically. Q-Robot drops the collected samples into automatic mixing tanks. Each mixer tank is assigned to a specific supplier and a specific material according to a loading list. The Q-Mixer automated sample handling equipment helps a lot of laboratory staff because the mixers form a daily combined biomass type and supplier-specific samples and every sample do not need to be analyzed individually.