Biomass co-firing in existing coal-fired power plants has been proven successful and practised in many installations worldwide as a greener alternative to coal. Attempts to overcome the low efficiency of transporting raw biomass have resulted in global wood pellets market growth in the past decade. This research studies the effect of biomass densification on biomass co-firing with coal. A three-dimensional CFD model was used to simulate the co-firing of coal and wheat straw. The model was verified by comparing the simulation results and experimental data presented in the literature. The experimental and predicted results were found to be in good agreement and exhibit the same general trends in terms of the gas species (O₂, CO, CO₂, and H₂O) concentrations. The effect of pelletization on biomass particle combustion was then investigated by considering particle shrinkage due to compression during pelletization. The baseline case is for uncompressed particles having particle density of 600 kg/m³, whereas the two cases of densified particles have particle densities of 800 kg/m³ and 1000 kg/m³. Results show that, when compared to the baseline case, compressed particles experience slower volatilization and surface reaction rates, and hence a greater percentage of unburnt carbon. Larger wheat straw particles (>894 μm) have different aerodynamic interaction compared to smaller particles in terms of residence time and particle trajectory. CFD results also show that compressed particles would exhibit lower NO emission, and NH₃ as the intermediate product from biomass volatile-N has contributed to the reduction in NO emission during the volatilization process.

中文翻译：

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麦秸混烧煤球化效果的CFD研究

现有燃煤电厂中的生物质混烧已被证明是成功的，并在全球许多设施中作为一种更环保的煤炭替代品进行了实践。在过去十年中，为了克服运输生物质原料的低效率问题，全球木屑颗粒市场取得了增长。本研究研究生物质致密化对生物质与煤混烧的影响。使用三维 CFD 模型模拟煤和麦秸的混烧。通过比较模拟结果和文献中的实验数据来验证该模型。发现实验结果和预测结果非常吻合，并且在气体种类（O ₂、CO、CO ₂和 H _{2 ）}方面表现出相同的总体趋势O) 浓度。然后通过考虑造粒过程中压缩导致的颗粒收缩来研究造粒对生物质颗粒燃烧的影响。基线情况是未压缩颗粒的颗粒密度为 600 kg/m ³，而两种致密颗粒情况的颗粒密度分别为 800 kg/m ³和 1000 kg/m ³. 结果表明，与基准情况相比，压缩颗粒的挥发和表面反应速率较慢，因此未燃烧碳的百分比更高。与较小的颗粒相比，较大的麦秆颗粒（>894 μm）在停留时间和颗粒轨迹方面具有不同的空气动力学相互作用。CFD 结果还表明，压缩颗粒会表现出较低的 NO 排放，而 NH ₃作为生物质挥发性 N 的中间产物有助于减少挥发过程中的 NO 排放。