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.
There are some trial project that replace pulverized coal with bio-char to target the pulverized coal power plant. These will have to solve a lot of issues. However, an electric energy demand is expected to increase more and more in the future by sustainable energy resources. We developed the solid biomass fuel (hereinafter refer to as Bio-coke:BIC) and studies to use as a replacement for coal coke advance. But, BIC has a few demerit. One of them is that the calorific value for unit quantity decrease because it contains a lot of free water and volatile matters. Torrefaction processing is one of the way how to improve the energy efficiency. In this study, we produced BIC from green tea and improved fixed carbon content ratio by torrefaction processing. And we execute thermal analysis and the combustion experiment using torrefied BIC (hereinafter refer to as T-BIC). The purpose of the use in a pulverized coal power plant, the sample crushed it beforehand. Results are found in the following. (1) In the case of volatile matter content ratio less than about 45 %, as volatile matter content ratio is high, gasification time for unit quantity increase. In the case of volatile matter content ratio more than about 45 %, gasification time for unit quantity close to constant. (2) In the case of fixed carbon content ratio in more than about 50 %, as fixed carbon content ratio is high, char combustion time for unit quantity decrease. In the case of fixed carbon content ratio in less than about 50 %, char combustion time for unit quantity close to constant.
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