In this paper, a computational framework for modelling the thermochemical conversion of powdered solid fuels in a MILD reactor is presented. Specific fuels of interest are high ash coals and lignocellulosic biomass. The novelty of the current framework lies in recognising that the devolatilisation process of charring fuels like biomass and coal is surface heat transfer limited at heating rates relevant to practical systems. The in-house unified ignition devolatilisation model developed for pelletised biomass in a packed bed configuration is extended to powdered fuels. Comprehensive modelling of a 50 kW solid fuel MILD reactor is accomplished by integrating the particle model with a commercially available CFD code. Unsteady Lagrangian particle tracking in an Eulerian gas phase is used to resolve the temperature profile in the reactor. Heat loss from the reactor walls, an essential parameter for obtaining accurate temperature profiles, is obtained by striking an energy balance over the entire domain using experimental data (from the earlier work of the authors). Results of numerical simulations with two different fuels (powdered coal and groundnut shells) covering a wide range of flow conditions obtained with the framework are presented in the current study. Normalised spatial temperature variation and the O${}_2$ mole fraction profiles with the two fuels indicate that the reactor operates in MILD mode. The temperature profiles predicted with the framework are in satisfactory agreement with the experimental results. The modelling approach successfully predicts the operational regimes of the reactor. A noteworthy feature of the new framework is its applicability in predicting devolatilisation of different fuels without the need for any adjustable constants. This enables the use of this framework as a predictive design tool.

在本文中，提出了一种模拟 MILD 反应器中粉末状固体燃料热化学转化的计算框架。感兴趣的特定燃料是高灰分煤和木质纤维素生物质。当前框架的新颖之处在于认识到炭化燃料（如生物质和煤）的脱挥发分过程是表面传热，受限于与实际系统相关的加热速率。为填充床配置中的颗粒状生物质开发的内部统一点火脱挥发分模型扩展到粉末燃料。50 kW 固体燃料 MILD 反应堆的综合建模是通过将粒子模型与商用 CFD 代码集成来完成的。欧拉气相中的非定常拉格朗日粒子跟踪用于解析反应器中的温度分布。反应器壁的热损失是获得准确温度曲线的一个重要参数，它是通过使用实验数据（来自作者的早期工作）在整个域上达到能量平衡来获得的。目前的研究显示了使用两种不同燃料（煤粉和花生壳）的数值模拟结果，涵盖了通过该框架获得的各种流动条件。归一化空间温度变化和 O 目前的研究显示了使用两种不同燃料（煤粉和花生壳）的数值模拟结果，涵盖了通过该框架获得的各种流动条件。归一化空间温度变化和 O 目前的研究显示了使用两种不同燃料（煤粉和花生壳）的数值模拟结果，涵盖了通过该框架获得的各种流动条件。归一化空间温度变化和 O${}_2$两种燃料的摩尔分数曲线表明反应堆在温和模式下运行。用该框架预测的温度曲线与实验结果吻合得很好。建模方法成功地预测了反应堆的运行状态。新框架的一个值得注意的特点是它适用于预测不同燃料的脱挥发分，而不需要任何可调节的常数。这使得可以将此框架用作预测设计工具。