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建立一维、非稳态单个球形木材颗粒热解模型,模型包含颗粒内部气相和固相质量、动量和能量守恒方程。颗粒内气体运动采用Darcy理论描述,传热模型包括颗粒内的导热和对流传热以及颗粒表面与外界的对流和辐射传热,热解动力学采用一步反应模型。运用文献中的实验结果对模型进行了验证,模型能够较好地预测颗粒内部不同位置处温度和固体失重率随时间的变化过程。运用模型考察进气温度和颗粒粒径对木材颗粒热解过程的影响。结果表明:进气温度越高,颗粒热解所需要的时间越短。相同无量纲直径处,小粒径的颗粒升温快,整个颗粒的温度趋于一致的时间较短,剩余固体率的变化规律与温度的变化一致。
A one-dimensional and unsteady single-particle pyrolysis model of wood particles was established. The model contained the internal gas and solid mass, momentum and energy conservation equations. The intraparticle gas movement is described by Darcy’s theory. The heat transfer model includes the thermal and convective heat transfer within the particle and the convection and radiative heat transfer between the particle surface and the outside. The pyrolysis kinetics is modeled using a one-step reaction model. The experimental results in the literature are used to validate the model. The model can predict the change of temperature and solid weight loss rate at different positions within the particle over time. Effect of inlet air temperature and particle size on pyrolysis process of wood pellets by using model. The results show that the higher the inlet temperature, the shorter the time required for the pyrolysis of the particles. In the same dimensionless diameter, the particles of small particle size rise rapidly, the temperature of the whole particle tends to be consistent for a short time, and the variation law of residual solid content is consistent with the change of temperature.