Transactions of the JSME (in Japanese)
Online ISSN : 2187-9761
ISSN-L : 2187-9761
Thermal, Engine and Power Engineering
Influence of size and density of highly densified biomass briquette on combustion behavior
Hiroyuki ITO
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2017 Volume 83 Issue 852 Pages 17-00080

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Abstract

To investigate the influence of briquette size and density on the combustion behavior in both flaming and char combustion stage, the combustion experiments with the highly densified columnar briquette made from cypress sawdust were carried out. Three sizes of the briquette, φ30 mm×60 mm, φ35 mm×70 mm and φ40 mm×80 mm, of which diameter/length ratio is kept constant at 1/2 and three types of the briquette density, 900, 1100 and 1300 kg/m3 were employed. The water content of the briquette was kept around 10 wt%. The mass loss rate and the duration in both combustion stages were measured. In the flaming combustion stage, it is observed that the average mass loss rate per unit specific surface area is proportional to the briquette surface area, while it doesn't depend on the briquette density. It is expected by considering Fourier number that the flaming combustion duration is proportional to the product of the inverse square of the specific surface area and the briquette density and it is shown that the experimental results correspond to the expectation. It is found that the relationship between normalized mass loss rate and normalized time is nearly the same regardless of the briquette size and density. In the char combustion stage, normalized mass loss can be approximately expressed with the shrinking core model by assuming the effective oxygen diffusion coefficient in the ash layer for each briquette density used in this study. And it is found that the effective oxygen diffusion coefficient in the ash layer obtained by the shrinking core model decreases with increasing the briquette density.

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© 2017 The Japan Society of Mechanical Engineers
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