桉木屑颗粒燃料固体桥结构构建与燃烧特性研究

Construction of Solid Bridge Structured Biomass Pellets by Eucalyptus Sawdust and Its Combustion Characteristics

在成型燃料内部构建固体桥结构可有效改善其物理品质,利用不同粒径桉木屑构建了具有固体桥结构的颗粒燃料,并进一步研究了颗粒燃料的燃烧特性。提出的构建方法为同种原料不同粒径混配成型,在电子压力机上进行了粒径(0,1 mm]原料混配粒径(4 mm, 5 mm]原料的颗粒压缩成型实验,结果显示混配量5%~10%时颗粒内部长粒径粒子的交叉缠绕,可形成适量的固体桥结构,短粒径粒子填充饱满,粒子间结合紧密。较佳的混配量为5%,颗粒具有较高的松弛密度,为1 074.79 kg/m^(3),最高的Meyer强度,为23.93 MPa,最低的比能耗,为27.06 kJ/kg,平衡含水率为11.65%,吸水速率k为0.015 3 min^(-1)。在热分析仪上进行了成型颗粒燃烧实验,颗粒燃烧过程较为平稳且有所延长,在升温速率10~40℃/min的范围内,着火温度Ti在246.60~265.00℃之间,最大失重速率(dm/dτ)_(1max)在-6.84~-29.10%/min之间,综合燃烧指数S在7.26×10^(-12)~1.09×10^(-10)min^(-2)·K^(-3)之间。在X射线荧光光谱仪上分析了颗粒灰分的元素组成,预测颗粒燃烧时具有中等或较高的结渣沾污趋势。

It is an effective way to improve the physical properties of biomass pellets by constructing“solid bridge”structures inside the pellets.A way of constructing“solid bridge”structured pellets was proposed by blending different particle sizes from one material.The construction scheme was set to add eucalyptus sawdust with(4 mm,5 mm]particle size into eucalyptus sawdust with(0,1 mm]particle size.The blending amount(referred to mass fraction of material with(4 mm,5 mm]particle size in the total materials)was 0,1%,3%,5%,7%,10%,15%,20%,25%,30%,40%and 100%,respectively.The cross-sectional structures of the made pellets showed that with 5%~10%blending amount,a proper amount of“solid bridge”structures can be constructed by long fiber particle mechanical interlocking.Under this condition,short fiber particles were filled among these mechanical interlocks sufficiently and thus the pellet possessed particle tightly arrangements.The appropriate blending amount was 5%,under which condition the relaxed density,Meyer hardness and specific energy consumption of the pellets reached the relatively higher,the highest and the lowest values of 1074.79 kg/m^(3),23.93 MPa and 27.06 kJ/kg,respectively.Meanwhile,the equilibrium moisture content and moisture absorption rate of the pellets was 11.65%and 0.0153 min^(-1),respectively.Then,the heating value analysis given the information that the structured pellets maintained the same higher heating value as the eucalyptus sawdust,which was 18.44 MJ/kg.At the heating rates of 10~40℃/min,the ignition temperature of pellet combustion(with 5%blending amount)was evaluated at 246.60~265.00℃,the burnout temperature was measured at 504.40~508.40℃,the maximum mass loss rate was assessed at-6.84~-29.10%/min,and the mean mass loss rate was calculated at-6.84~-29.10%/min,the integrated combustion index was determined at 7.26×10^(-12)~1.09×10^(-10) min^(-2)·K^(-3).Besides,the slagging and fouling indices predicted a high or medium tendency for combustion.