Self-heating and Off-gassing from Biomass Pellets during Storage

• The use of biomass pellets is increasing. As a consequence,large indoor storage facilities are needed along the transportation line. Theincreased production volumes, transportation, handling and storage of pellets resultin increased risks. A number of fire incidents due to spontaneous ignition inwood pellets storages and accidents due to CO intoxication have been reported.Increased efforts concerning safety and quality assurance are, therefore,important. The aim of the present work is to provide methods for estimatingrisks for self-heating of and off-gassing from pellets stored in bulk. Theexperimental work ranges from small-scale characterizations to large-scalestorage tests and includes several different types of pellets. One aim has been to develop smallscale screening methods to assess the propensity for self-heating andoff-gassing, thereby trying to define the specific type of “activity” occurringin the pellets as well as characterising it. In addition to using said methods,isothermal calorimetry (micro calorimeter) and Oxipres (oxygen depletion), theformation of different gases (e.g. aldehydes) was analyzed. Thirteen  samples from different types of pellets havebeen ranked relative to each other. Effects of processes like aging can also beseen in the results. The results clearly reveal that different activity levelsof the pellets can be measured using small scale screening methods and thatthere are certain correlations between off-gassing and heat development, althoughthese are not yet fully understood.

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Energy- and Environmental Engineering

energi- och miljöteknik

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