Abstract Thermochemical conversion of biomass via fast pyrolysis is a proven pathway to product low-carbon crude bio-oils. In this research, an extended discrete element method (DEM) is proposed for simulating biomass fast pyrolysis reacting granular flows in a double auger reactor, in which particle hydrodynamics and interparticle heat transfer processes are involved and coupled with chemical reactions in solid particles. An adaptive time step algorithm is proposed to achieve a stable coupling between the integration of reaction ordinary differential equations and the DEM solver, and the algorithm is proven computationally efficient. A multi-component fast pyrolysis kinetics is adopted and its modeling accuracy is assessed by carrying out simulations of benchmark biomass pyrolysis experiments and comparing the prediction results with experimental data. The predicted product yields of bio-oil, char and non-condensable gas from the simulation of the biomass fast pyrolysis in the auger reactor are in satisfactory agreement with experimental measurements. The decomposition rates of biomass components in the reactor are revealed from the simulation and the pyrolysis number Py is calculated from the decomposition rate of biomass and the heat transfer coefficient. The Py number illustrates that the biomass fast pyrolysis process is limited by the heat transfer process at particle size of 2 mm.

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双螺旋反应器中生物质快速热解的 DEM 建模

摘要 通过快速热解对生物质进行热化学转化是一种经过验证的生产低碳粗生物油的途径。在这项研究中，提出了一种扩展离散元方法 (DEM)，用于模拟双螺旋反应器中生物质快速热解反应的颗粒流，其中涉及颗粒流体动力学和颗粒间传热过程，并与固体颗粒中的化学反应相耦合。提出了一种自适应时间步长算法来实现反应常微分方程的积分与 DEM 求解器之间的稳定耦合，并且该算法在计算上被证明是有效的。采用多组分快速热解动力学，通过对基准生物质热解实验进行模拟并将预测结果与实验数据进行比较来评估其建模精度。模拟螺旋反应器中生物质快速热解的生物油、焦炭和不可凝气体的预测产品产量与实验测量结果一致。通过模拟揭示反应器中生物质组分的分解速率，并根据生物质的分解速率和传热系数计算热解数Py。Py 数说明生物质快速热解过程受到粒径为 2 mm 的传热过程的限制。来自螺旋钻反应器中生物质快速热解模拟的炭和不可凝气体与实验测量结果令人满意地一致。通过模拟揭示反应器中生物质组分的分解速率，并根据生物质的分解速率和传热系数计算热解数Py。Py 数说明生物质快速热解过程受到粒径为 2 mm 的传热过程的限制。来自螺旋钻反应器中生物质快速热解模拟的炭和不可凝气体与实验测量结果令人满意地一致。通过模拟揭示反应器中生物质组分的分解速率，并根据生物质的分解速率和传热系数计算热解数Py。Py 数说明生物质快速热解过程受到粒径为 2 mm 的传热过程的限制。