Fig. 1. Effects of type and concentration of immersing solution on the contents of Klason (top) and soluble (bottom) lignins of larch sawdust immersed in tap water (TW), 1% and 2% sulfuric acid (AC-1% and AC-2%) and 1% and 2% sodium hydroxide (AK-1% and AK-2%) solutions. Same capital letters denote results that are not significantly different from each other at p = 0.05 (least significance difference test).
Fig. 2. Effect of immersion time on the contents of Klason (top) and soluble (bottom) lignins of larch sawdust immersed in tap water, sulfuric acid and sodium hydroxide solutions.
Fig. 3. Effect of type of immersing solution on the monomeric sugars content of larch sawdust immersed in tap water, sulfuric acid (top) and sodium hydroxide (bottom) solutions. Same capital letters denote results that are not significantly different from each other at p = 0.05 (least significance difference test).
Fig. 4. Effects of type and concentration of immersing solution on the durability of wood pellets fabricated with larch sawdust, which was immersed in tap water (TW), 1% and 2% sulfuric acid (AC-1% and AC-2%) and 1% and 2% sodium hydroxide (AK-1% and AK-2%) solutions. Same capital letters denote results that are not significantly different from each other at p = 0.05 (least significance difference test).
Fig. 5. Effect of immersion time and the concentration of immersion solution on the durability of wood pellets fabricated using larch sawdust immersed in sodium hydroxide (left) and sulfuric acid (right) solutions.
Fig. 6. Durability of wood pellets fabricated with larch sawdust, which was immersed in tap water, sodium hydroxide and sulfuric acid solutions. Results show the relationship between pellet durability and contents of Klason lignin (top-left), soluble lignin (top right), glucose (bottom-left) and galactose (bottom-right). Durability of larch pellets by content of Klason lignin = 1.51x + 48.05, r2=0.63; soluble lignin = 2.56x + 89.21, r2 = 0.12; glucose = −0.57x + 116.22, r2 = 0.21; galactose = 0.71x + 81.47, r2 = 0.04.
Fig. 7. Fluorescent microscopic images of the surface, which was pressured by piston, of wood pellets fabricated with non- (top-left), tap water- (top-middle), 1% sulfuric acid- (top-right), 1% sodium hydroxide-(bottom-left), 2% sulfuric acid- (bottom-middle) and 2% sodium hydroxide- (bottom-right) immersed larch sawdust. The sawdust was stained with a phloroglucinol-HCl solution for 24 h. Bars = 2 mm. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).
Fig. 8. Scanning electron microscopic (SEM) images of wood pellets fabricated with A) non- (top-left), B) tap water- (top-middle), C) 1% sulfuric acid-(top-right), D) 1% sodium hydroxide- (bottom-left), E) 2% sulfuric acid- (bottom-middle) and F) 2% sodium hydroxide- (bottom-right) immersed larch sawdust. SEM image (left) and corresponding SEM-EDX (energy dispersive X-ray spectrometer) maps (right) taken of the same area of the wood pellets. Bright purple spots and arrow indicate the existence of lignin. Bars = 60μm. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).
Fig. 9. Content of manganese distributed on the surface of wood pellets fabricated using larch sawdust immersed in, tap water (TW), 1% sulfuric acid (AC-1%), 1% sodium hydroxide (AK-1%), 2% sulfuric acid (AC-2%), 2% sodium hydroxide (AK-2%) solutions, and non-immersed (NI) larch sawdust. The results were obtained by SEM-EDX analysis. Same capital letters denote results that are not significantly different from each other at p = 0.05 (least significance difference test).
Table 1. Fuel characteristics of wood pellets fabricated with larch sawdust immersed in tap water (TW), sodium hydroxide (AK) and sulfuric acid (AC) solutions
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