Objective

Within the project A6 the behaviour of biomass pellets during storage and transport for domestic use is investigated. The challenge in the processes is to maintain the quality of the pellets in terms of their mechanical stability. Low stability leads to increased breakage of the pellets when subjected to mechanical stress and to high fines content due to detachment of individual wood shavings. The fine particles accumulate in the storage room and in the transport systems and lead to dead zones. The mechanical stability of biomass pellets can be negatively influenced in particular by a high water content (>10% wt.-%) resulting from high humidity (>80%). Therefore, the influence of the water content on the structure and stability of biomass pellets is investigated experimentally. In addition, experiments will be carried out in a silo constructed for this project with a screw conveyor to investigate the effect of high water and fines content on the flowability of a pellet bulk. In addition, DEM simulations will be carried out to analyse velocity distributions and force influences.

Person Responsible

Abdullah Sadeq, M.Sc., Institute of Solids Process Engineering and Particle Technology

Betreuer

Prof. Dr.-Ing. habil. Dr. h.c. Stefan Heinrich, Prof. Dr.-Ing Jürgen Grabe

Methods and work programme

The following experimental and numerical methods are applied to investigate the research question.

Characterisation of wood pellets with different water content and evaluation with regard to their structure and stability:

• Micro computed tomography (µCT)
• Confocal laser scanning microscopy
• Scanning electron microscopy
• Compression and bending tests of single pellets

Figure 1: Representation of the pore structure (red) of wood pellets using µCT.

Characterisation of the flowability of a pellet bed as a function of water content and fines content:

• Experiments on the transport of pellets from the silo with a screw conveyor
• DEM simulation of the transport of pellets from the silo by means of the MUSEN framework using the Bonded Particle Model

Figure 2: CAD representation of the silo and the screw conveyor with the dimensions in millimetres.