Abstract

A two-dimensional, transient and single particle model was developed for biomass torrefaction. A wood cylinder $(\rho =700\mathrm{ }\mathrm{kg}/{\mathrm{m}}^3,\mathrm{ }28\text{ mm in diameter and }100\text{ mm long})$ was modeled as a porous solid. The transport, energy conservation and intra-particle pressure evolution equations were discretized by the finite volume method. The resulting linear algebraic equations were solved using the tridiagonal matrix algorithm. Intra-particle flow velocity was estimated by Darcy’s law. Simulation results for intra-particle temperature profile and mass loss history showed good agreement with experimental data from the literature. Thermal flux, drying and torrefaction fronts advanced into the interior of the particle in semi-ellipsoidal form. Water vapor is the main volatile released. The reduction in mass yield is higher than the reduction in energy yield due to loss of water and carbon dioxide. This model can be used in a wide range of process conditions and as an important tool in biomass thermal pretreatment.

摘要

为生物质烘焙开发了二维、瞬态和单粒子模型。一个木缸$(\rho =700\mathrm{ }\mathrm{公斤}/{\mathrm{米}}^3,\mathrm{ }28\text{ 毫米直径和 }100\text{ 毫米长})$被建模为多孔固体。输运方程、能量守恒方程和颗粒内压力演化方程采用有限体积法离散化。使用三对角矩阵算法求解得到的线性代数方程。颗粒内流速由达西定律估计。颗粒内温度分布和质量损失历史的模拟结果与文献中的实验数据非常吻合。热通量、干燥和烘焙前沿以半椭圆体形式进入颗粒内部。水蒸气是释放的主要挥发物。由于水和二氧化碳的损失，质量产量的减少高于能量产量的减少。该模型可用于广泛的工艺条件，并可作为生物质热预处理的重要工具。