Abstract
Biomass fuels in large storage units are prone to self-heating and ignition causing smoldering fires. Here, the susceptibility of such ignition processes to parameters is explored through small-scale experiments. In a silo geometry, wood pellets samples of size 0.75 to 1.5 kg were heated from below to initiate smoldering, while the top was open, allowing convective exchange of gases between the porous sample and the surroundings. The thermally insulated sidewalls reduce the heat flow in lateral direction in a similar way that additional pellets material would do in a larger set-up. Thus, the present experimental set-up mimics a much larger system in lateral direction. After heating was terminated, the procedure led to self-sustaining smoldering or spontaneous cooling, depending on parameters.The transition zone between smoldering and non-smoldering was explored under variation in sample size, imposed heating, pellets type, and height of sample container. Logistic regression was applied to fit the experimental data to a model. The model predicted the probability of an experiment to result in either smoldering or non-smoldering under variation in parameters – and the parameters were sorted according to importance. The duration of the external heating was found to be the most influential parameter. For risk assessments in connection with large biomass fuel storage units, this result indicates that the temperature increase could be more important than the size and geometry of the storage unit and the stored material type.
Highlights
Solar energy may be harvested using a number of different technologies, each with advantages and disadvantages
There are technological and economical challenges connected to transportation, production, and storage
When stored in large quantities, biomass products are prone to self-heating, spontaneous temperature increase that potentially lead to smoldering fires [5]
Summary
Solar energy may be harvested using a number of different technologies, each with advantages and disadvantages. Storage usually occurs in large units, typically silos, which makes sense from an economical and practical perspective. When stored in large quantities, biomass products are prone to self-heating, spontaneous temperature increase that potentially lead to smoldering fires [5]. Whether such a temperature increase will level out or increase till a smoldering fire is started depends on a number of parameters, most importantly the size of the stored material. From a practical point of view, one needs to keep the stored amount below this critical size – or, alternatively, keep storage times sufficiently short (typically, below 3 months for large silos) [6]
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