Comeback to fire-damaged silo in a top-safe versionLena Heldgaard Pind Jensen2024-08-07T15:36:48+02:00 Comeback to fire-damaged silo in a top-safe version The CHP plant Studstrupværket’s enormous wood pellet silo is facing a reconstruction with several significant upgrades to prevent future fires. Artelia helps establish the new initiatives, which include a nitrogen factory, a water mist system and a fire detection system. On 22 September 2022, Studstrups-værket’s silo for certified wood pellets, which is used in the plant’s unit 3, caught fire. In this block, heat is produced equivalent to the consumption of 106,000 households and electricity corresponding to the consumption of 230,000 households. The silo therefore plays a significant role, and even though the heat supply was initially unaffected, the owner Ørsted immediately started cleaning up and investigating, while planning the reconstruction. A project that Artelia is now taking part in, as we are consultants on the construction project and provide machine and process-related services. The nitrogen factory Damp comprises a sort of fire hazard and probably initiated the fire in 2022. Just a little bit of increased damp in the wood pellets can start a biological process that generates heat that can escalate quickly if not released. This may be close to impossible if the process takes place in the middle of a stack of 56,000 tons of wood pellets. This results in high temperatures, which is extra risky when very large quantities of fuel are within reach. The phenomenon is also known from piles of compost that combust spontaneously. A major preventive measure at Studstrupsværket is a new nitrogen factory, which will remove oxygen from the silo’s wood pellets and atmosphere. This means challenging conditions for organic processes, and more importantly, it can prevent fire development. The nitrogen factory works in such a way that normal atmospheric compressed air is sent through special filters and containers that absorb the oxygen and allow the air’s remaining nitrogen to pass. For all the new initiatives, we are responsible for descriptions and tenders of the technical facilities, which must be manufactured specially for the purpose, says Jens Schaltz Bertelsen, who is project manager for the machine and process part: We provide fairly detailed descriptions of the desired functions and help clarify all technical issues. In certain cases, we define the choice of material and ATEX-related aspects. At the same time, there is a task in designing all necessary piping, which connects the nitrogen factory to the silo. Jens Schaltz BertelsenProject DirectorEnergy Plants © Colourbox, Kenneth Bagge Jørgensen The water mist system If worst comes to worst, another new installation will come into effect, says Jens: The nitrogen factory is part of plan A, while plan B is a water mist plant at the top of the silo. Once a fire is impossible to stop, the system can produce a large cooling cloud that will protect the roof structure. As Jens points out, the nitrogen plant is one of several new installations that will come into play before plan B becomes effective, since the use of water has complications as mentioned and therefore is a last resort. 2,000 temperature measurements Another assignment is a new fire detection system. From top to bottom of the silo, approx. 65 cables will be placed carefully with small temperature gauges attached for every metre all the way down through the wood pellet stack. This will give a total of approx. 2,000 temperature measurements. This way, the operating organisation can observe any kind of heat development in the sea of wood pellets and intervene in time by e.g. adding extra nitrogen. Here we have mapped the length and location of cables and defined the required number of measurements. We have also made a presentation on how the system can be programmed and implemented in the plant’s control system. In reality, we have enough temperature measurements to create a 3D model if desired. The reconstruction Our engineers in Aarhus are responsible for the structural aspects, and they model all structures in Tekla, which contains the project’s master model. For this, the installation design is imported from Revit together with models from the programme Plant, which our specialists in machine and process use. The digital platform must be used in particular to coordinate the many interfaces. Large parts of both the silo and the transport facility survived the fire, and Ørsted mapped how much can be reused and what must be thrown away. Existing structures, installations and equipment must thus be combined with new parts, which makes this part of the project special, Jens concludes: A contractor will probably find it easier to build a new facility from scratch using own well-known methods. But since we must ensure the greatest possible reuse of the materials, it will be our job to provide a solid knowledge base regarding the existing material, since the alternative will be too many unknown factors. It is not just about describing what is already there, but also how it can be connected to something new.