Self-heating and drying in two-dimensional bagasse piles
Self-heating and drying in two-dimensional bagasse piles
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DOI：
10.1088/1364-7830/5/4/302
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发表时间：
2001-12-01
影响因子：
1.3
通讯作者：
Gray, BF
中科院分区：
文献类型：
--
作者：
Sexton, MJ;Macaskill, C;Gray, BF
本文描述了等截面矩形或三角形甘蔗渣堆中的自热和水位变化的二维模型。(甘蔗渣是从甘蔗中提取糖后剩下的残留物，主要是纤维素。)经过碾磨后，蔗渣中几乎有50%的水，因为热水被用来去除最后的糖。甘蔗渣可以用作发电站的燃料，但在使用之前需要干燥。本文讨论了桩的干燥方式取决于环境条件，以及桩的形状和大小。相应地，能量方程和液态水、水蒸气和氧气的方程用直线法进行了数值求解。这些方程包括描述热传导、水蒸气和氧气的扩散、冷凝和蒸发的项以及Arrhenius自加热项。此外，最近的测量表明，由于甘蔗渣中存在水，也存在自加热，最大影响在60摄氏度附近，这是由修正的Arrhenius表达式模拟的。问题的热释放曲线中的局部最大值导致在短时间尺度上的近似稳态行为，最终随着堆积的干涸而丢失。这一有趣的物理行为激发了一个近似的分析模型，用于计算堆中液态水的还原速度。文中给出了各种桩型的解析和数值结果，并得出了一些相当普遍的结论。
This paper describes a two-dimensional model for self-heating and changes in water levels in bagasse piles of constant rectangular or triangular cross section. (Bagasse is the residue, mainly cellulose, that remains after sugar has been extracted from sugar-cane.) After milling, the bagasse has almost 50% water by weight, as hot water is used to remove the last of the sugar. The bagasse can be used as fuel in electrical power stations, but needs to be dried out before use. This paper discusses the way in which the drying out of a pile depends on the ambient conditions, and the shape and size of the pile. Accordingly, the energy equation, and equations for liquid water, water vapour and oxygen are solved numerically using the method of lines. The equations include terms describing heat conduction, diffusion of water vapour and oxygen, condensation and evaporation and an Arrhenius self-heating term. In addition, recent measurements show that there is also self-heating due to the presence of water in the bagasse, with a maximum effect near 60degreesC, which is modelled by a modified Arrhenius expression. The local maximum in the heat release curve for the problem leads to approximate steady-state behaviour on short time scales that eventually is lost as the pile dries out. This interesting physical behaviour motivates an approximate analytical model for the rate at which liquid water is reduced in the pile. Analytical and numerical results are presented for a variety of pile configurations and some fairly general conclusions are drawn.