Conversion of biomass into gas suitable for further exploitation is one of the valuable renewable energy pathways due to the wide distribution and availability of raw materials. Biomass gasification is a thermochemical process of partial combustion in a reduced oxygen environment that aims to produce hydrogen-enriched syngas. Updraft gasifier design, with its advantages of high efficiency, produces syngas with higher hydrogen yield compared to other gasifier designs. The main drawback of the updraft gasifier is high yield of tars in the outflow gas decreasing its lower heating value. Recently, significant research efforts have focused on the optimization of the updraft gasifiers operating conditions, especially by developing numerical models as a complementary approach to experiments. The simplest modelling approach for predicting biomass gasification behaviour is the thermodynamic equilibrium model. When describing the behaviour of an updraft gasifier, special focus needs to be given to the pyrolysis stage, since in this type of reactor pyrolysis products directly outflow from the gasifier. In this work, a pilot-scale biomass gasifier was modelled using a combination of a pyrolysis kinetic model with a thermodynamic equilibrium model. To describe the pyrolysis behaviour, the CRECK-S-BIO and two secondary gas-phase mechanisms with distinct levels of complexity were used. The gasification and oxidation of char were modelled using a thermodynamic equilibrium model through the minimization of Gibbs free energy approach. The predicted results of dry clean syngas were compared to the experimental data considering eleven different operating conditions. The model combination that used the detailed secondary gas-phase mechanism achieved generally lower average prediction errors. Although some discrepancies were observed in the predictions, these preliminary results show that the model approach considered in this study represents a good basis for future development of the model.

中文翻译：

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结合热解动力学模型和热力学平衡模型对生物质上升气流气化过程进行建模

由于原材料的广泛分布和可用性，将生物质转化为适合进一步开采的气体是有价值的可再生能源途径之一。生物质气化是在低氧环境下部分燃烧的热化学过程，旨在产生富氢合成气。上升气流式气化炉设计具有效率高的优点，与其他气化炉设计相比，产生的合成气具有更高的氢气产率。上升气流气化炉的主要缺点是流出气体中焦油产量高，降低了其较低的热值。最近，重要的研究工作集中在上升气流气化器操作条件的优化上，特别是通过开发数值模型作为实验的补充方法。预测生物质气化行为的最简单的建模方法是热力学平衡模型。在描述上升气流气化器的行为时，需要特别关注热解阶段，因为在这种类型的反应器中，热解产物直接从气化器中流出。在这项工作中，使用热解动力学模型与热力学平衡模型的组合对中试规模的生物质气化炉进行了建模。为了描述热解行为，使用了 CRECK-S-BIO 和两种具有不同复杂程度的二级气相机制。通过最小化吉布斯自由能方法，使用热力学平衡模型对炭的气化和氧化进行建模。将干洗合成气的预测结果与考虑十一种不同操作条件的实验数据进行比较。使用详细的二次气相机制的模型组合总体上实现了较低的平均预测误差。尽管预测中存在一些差异，但这些初步结果表明，本研究中考虑的模型方法为模型的未来开发奠定了良好的基础。