Pasi Karinkanta

Effect of grinding conditions in oscillatory ball milling on the morphology of particles and cellulose crystallinity of Norway spruce (Picea abies)

Abstract Norway spruce (Picea abies) has been submitted to oscillatory ball milling at room temperature and at -196°C. The effects of moisture content (MC) and cryogenic milling on the morphology and crystallinity of cellulose were investigated. At room temperature, MC had a significant effect on particle morphology and it was possible to produce powders of smaller particle size and rounder shape when the wood feed had a lower MC. Under cryogenic conditions, MC had less influence on the morphology, and the particle size was even smaller than that produced under ambient conditions. The degree of cellulose crystallinity in the milled wood was influenced by the MC of the feed, milling time, and milling temperature.

Effect of mild torrefaction on pulverization of Norway spruce (Picea abies) by oscillatory ball milling: particle morphology and cellulose crystallinity

Abstract The effects of mild torrefaction on the pulverization of Norway spruce sawdust have been studied. To this end, sawdust was dried and torrefied below 230°C for different periods of time to obtain samples with mass losses (ML) of 0.2%, 1.4%, and 2.8%, milled in an oscillatory ball mill, and the particle morphology and cellulose crystallinity of the powders were studied. The pretreatment leading to 0.2% ML had no effect on grindability, but that resulting in 1.4% ML improved grindability and a median particle size below 17.4±0.2 μm was attained. Torrefaction involving 2.8% ML reduced the specific energy consumption more than 21% when the targeted median particle size of the torrefied wood was between 18.7±0.5 and 79±3 μm. The mild torrefaction had a negligible influence on the aspect ratio distribution and cellulose crystallinity in the ball-milled wood.

Utilization of Mineral Wools as Alkali-Activated Material Precursor

Mineral wools are the most common insulation materials in buildings worldwide. However, mineral wool waste is often considered unrecyclable because of its fibrous nature and low density. In this paper, rock wool (RW) and glass wool (GW) were studied as alkali-activated material precursors without any additional co-binders. Both mineral wools were pulverized by a vibratory disc mill in order to remove the fibrous nature of the material. The pulverized mineral wools were then alkali-activated with a sodium aluminate solution. Compressive strengths of up to 30.0 MPa and 48.7 MPa were measured for RW and GW, respectively, with high flexural strengths measured for both (20.1 MPa for RW and 13.2 MPa for GW). The resulting alkali-activated matrix was a composite-type in which partly-dissolved fibers were dispersed. In addition to the amorphous material, sodium aluminate silicate hydroxide hydrate and magnesium aluminum hydroxide carbonate phases were identified in the alkali-activated RW samples. The only crystalline phase in the GW samples was sodium aluminum silicate. The results of this study show that mineral wool is a very promising raw material for alkali activation.