Soaking of pine wood chips with ionic liquids for reduced energy input during grinding

Abstract

Ionic liquids are of great interest as potential solvents/catalysts for the production of fuels and chemicals from lignocellulosic biomass. Attention has focussed particularly on the pretreatment of lignocellulose to make the cellulose more accessible to enzymatic hydrolysis. Any biomass processing requires a reduction in the size of the harvested biomass by chipping and/or grinding to make it more amenable to chemical and biological treatments. This paper demonstrates that significant energy savings can be achieved in the grinding of pine wood chips when the ionic liquid is added before the grinding operation. We show that this is due to the lubricating properties of the ionic liquids and not to physico-chemical modifications of the biomass. A brief impregnation of the chipped biomass results in higher savings than a longer treatment.

Effects of Soaking in Glycerol and Conventional Solvents on the Grinding of Kempas Wood (Koompassia malaccensis)

“…Brandt et al (2012) hypothesised that energy savings might relate to rougher grinding and larger final particle sizes due to the starting particle sizes being very similar. Therefore, the particle size distribution of the ground wood was measured for each sample and average particle size was calculated in order to determine whether the energy savings were related to less effective grinding.…”

“…The tubes were placed in an oven and kept at 90°C for 1 h (Brandt et al 2012). After that, they were allowed to cool down to room temperature.…”

“…After grinding, the wood chips were soaked overnight in 20 mL methanol as indicated in the study by Brandt et al (2012). They were then filtered and rinsed again with methanol and left to air-dry overnight.…”

“…Each sample was ground for 5 s as this was sufficient to grind the untreated wood chips into powder as shown by Brandt et al (2012). The energy consumption (E c ) was calculated as the energy E in joules (J) consumed during 1 h per g of sample, divided by the time period t in seconds (s) according to (2).…”

“…Adapa et al (2011) and Zhu et al (2010) found that the particle size reduction of biomass helps to increase the surface area, pore size and number of points of contact for inter-particle bonding in compaction operations such as densification process, which is an important step in the transformation of feedstock into bio-energy in the field of renewable energy obtained from renewable biomass-based resources. While from the studies conducted by Brandt et al (2012) on the energy consumption during the grinding process, it was found that the wood pre-soaked in ionic liquids or lubricants was able to be ground to a smaller particle size compared to the air-dried wood. However, there are still many challenges in putting ionic liquids into practical use due to their high cost and the need for regeneration techniques (Park & Kazlauskas 2003).…”