Wood pellets; straw pellets; internal particle size distribution
Abstract :
[en] Several methods for disintegration of biofuel pellets were tested and compared for their ability to break
up the pellets into the original particles of the raw material. Analyses performed on softwood pellets and
straw pellets concluded that wet disintegration in water at ambient temperature is insufficient for a
determination of the internal particle size distribution of wood- and straw pellets. When the wet disintegration
was performed with water heated to the boiling point and coupled with mechanical disintegration
in terms of stirring a more complete disintegration of the pellets was obtained. Based on the results
obtained in the initial study a round robin was set up including six European laboratories where the
selected method was tested. In the round robin test the method combining heated water and stirring
of the slurry was tested on solid biofuel pellets produced of comminute straw, deciduous wood and coniferous
wood respectively. With the method a satisfactory disintegration was obtained of all three types of
pellets.
Further wet disintegration of coniferous pellets was compared to a dry disintegration using a hammer
mill. The dry disintegration of the coniferous pellets resulted in smaller particle sizes compared to the
wet disintegration using heated water and stirring of the slurry indicating a further disintegration of
the original particles in the hammer mill process.
Overall the wet disintegration combined with mechanical impact was found to be the most suitable
method for disintegration of solid biofuel pellets. Combined with sieving analysis the method gives realistic
image of the internal particle size distribution of solid biofuel pellets.