| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 210232 | Fuel Processing Technology | 2012 | 6 Pages |
The purpose of the study was to investigate the influence of torrefaction on the quality of Scots pine pellets. Pellet samples were torrefied at 230, 250 and 270 °C for 1 h in nitrogen atmosphere. Higher heating value (HHV) was increased from 18.37 MJ kg− 1 to 24.34 MJ kg− 1. The energy to crush a pellet by mechanical compression was determined using a material tester and results showed a rapid decrease before torrefaction temperature reached 250 °C. Slightly further decrease was observed when increasing the temperature up to 270 °C. The strength loss was confirmed by determining the energy required for grinding the pellet samples in a bench scale disc mill. Particle size distribution measurements after grinding indicated a significant increase of small particles (diameter < ca. 1 mm) for torrefied pellets at a torrefaction temperature of 230 °C and further increase of temperature resulted in steep decrease of large particles (diameter > ca. 2 mm). To further analyze the effect on strength, the mechanical durability of pellets was tested according to wood pellet standards, EN 15210-1. The results have shown a good correlation between pellet durability and compression strength, and indicated that the pellet durability can be estimated based on compression strength data of about 25 pellets.
► The influence of torrefaction on the quality of Scots pine pellets. ► Pellets energy loss due to torrefaction is 84 times of the energy saved in grinding. ► Pellet durability can be estimated by compression strength of about 25 pellets. ► Pellet strengths decrease exponentially when weight loss increase in torrefaction. ► Good correlation among pellet durability, compression strength, and grinding energy.
