Solidification characteristics of green tea as raw material of solid fuel

Abstract

Biocoke (BIC), made from all types of biomass is a solid fuel. Hemicellulose and lignin, essential chemical components of biomass, work as bonding agents of BIC solidification because they have softening and fluidity characteristics. Their characteristics make bonding structure inside of BIC during the formation process. Previous studies suggested that physical and mechanical characteristics of BIC are different if raw materials (kinds of biomass) are different even if forming conditions are the same. It was inferred that the reason was different of content rate of main components. Among various biomass, green tea has excellent formability. In this paper, we focus on the potential of green tea as a raw material of BIC. Firstly, we compared the fluidity of green tea with other biomass. Then, compressive strength tests of BIC made from green tea and other biomass were conducted. We used the trunk of conifers, the bark of conifers, bagasse, and rice straw other than green tea. The result of fluidity test indicated that green tea is easiest-to-flow biomass among the five biomasses. Moreover, the flow starting temperature was able to estimate from a content percentage and moisture content with ±30% accuracy by using our estimated equation. As results of compressive strength test, each BIC which was made from five biomasses have two peak points of compressive strength and apparent density. Green tea BIC made under all the test conditions has high apparent density 1.3-1.4 g/cm 3. On the other hand, green tea BIC has the lowest compressive strength among the five biomasses tested. We found out that the raw material which it is easy to fluidize by heating has low compressive strength from these results.

Estimation of maximum Bio-coke compressive strength based on chemical composition

“…Experimental results suggested that samples with high hemicellulose and lignin contents, together with high moisture contents underwent fluidization at lower temperatures. This is consistent with the fact that biomass containing large amounts of hemicellulose, such as herby biomass (Tagami and Ida, 2019), undergoes fluidization at lower temperatures. Furthermore, we previously assessed the compressive strength of Bio-coke produced from five biomass sources, and found that higher cellulose content, resulted in higher compressive strength (Tagami and Ida, 2018).…”

The influence of additional hemicellulose on Japanese cedar based pre-carbonized solid biofuel properties

“…The highest and lowest apparent density of BIC in this research is at 1.435 g/cm 3 and 1.416 g/cm 3 repectively, from 15% of additional hemicellulose. This result is explained by the softening behavior of hemicellulose, the softening temperature of dried hemicellulose has been reported at 423 K by Goto et al, 2012 andTagami et al, 2019. The softening behavior of Japanese cedar was reported by Tagami et al, 2019 at approximately 460 K. Since the forming temperature of this research is 463 K, the increasing of additional hemicellulose results in greater reaction between materials particles.…”

“…The forming temperature of BIC at 463 K in this study is in the softening region of Japanese cedar (for the initial moisture content at 10 wt. %) and 20 K greater than glucomannan powder (Tagami et al, 2019). As mentions earlier about the reaction during the BIC transformation process in the molecular level, the additional hemicellulose react and bond with the molecules JC components.…”

“…% of hemicellulose, which mean the reaction between the hemicellulose particles itself decreases the strength of BIC. Hemicellulose is reported to be decomposed by thermal around 453 to 573 K. According to Tagami et al, 2019, glucomanan powder used in this study starts to decompose at 443 K. The additive glucomannan particles could transform into different structures such as furfural or O-acetyl during the BIC production, results in improvement of the product with 5 to 10 wt. % of hemicellulose.…”

“…It varies depending on the type of material, such as hardwoods, softwoods, and glasses. According to Tagami and Ida, 2019, which conducted the experiment on the solidification characteristics and maximum compressive strength, the higher initial moisture content the lower maximum compressive strength. In this case, the higher moisture content of mixtures could negatively affect the product strength.…”