热等离子体煤裂解制乙炔的转化规律与定向控制

程易颜++彬航++张乐++程炎

摘 要：煤炭資源的清洁、高效转化和利用是缓解石油资源短缺、保障我国能源安全的关键。热等离子体煤裂解一步法制乙炔工艺具有流程短、水耗少、碳排放低等特点，是一条极具前景的煤直接转化路线。该过程在超高温下实现煤粉的毫秒级转化，目前国际上尚未实现工业化。该研究实验和理论并重，研究了等离子体反应器内煤粉的裂解特性及复杂的气固流动和反应行为。该研究自主设计、开发了等离子体煤裂解实验装置，考察了典型煤种的超高温裂解特性。实验结果表明了过程的煤质依赖性，为工业过程的煤种筛选提供了科学方法和实验依据。通过对不同升温速率下的煤粉热解情况的考察比较，全面认识了煤的热解特性，为快速热解选煤实验平台提供了理论基础。基于大量热解实验数据改进了煤粉脱挥发分动力学模型，使其具有良好的煤种适用性和预测精度；进而建立了耦合煤质分子结构、颗粒内部传热、颗粒—流体间传热—反应等要素的跨尺度气固反应流动模型，实现了对2 MW和5 MW工业反应器内煤粉裂解行为的三维复杂热态模拟，与工业反应器的运行数据符合良好，准确地揭示了反应器的放大效应和过程的颗粒尺寸依赖性。

关键词：煤 乙炔 热等离子体 计算流体力学

Coal Pyrolysis to Acetylene in Thermal Plasmas：Principles and Controlled Production

Cheng Yiyan Bin Hang Zhang Le Cheng Yan

（Tsinghua University）

Abstract：Highly efficient， clean coal conversion techniques to chemicals and alternative fuels play important roles in meeting the urgent energy demand due to the shortage of oil and natural gas resources in order to secure the Chinas energy safety. One-step conversion from coal to acetylene in thermal plasma opens up a direct route to make chemicals from coal resources， representing a rather cleaner process characterized by short process， low water consumption and low CO2 emission. This is especially applicable for the development of coal industry in the areas lacking water resources. As the essential feature of millisecond coal conversion at ultra-high temperatures， such a sophisticated reactor technique has not been commercialized yet in the world. In this work， comprehensive studies on the complex gas-particle flow and reaction behaviors were carried out in thermal plasma reactors from both experimental and theoretical aspects. Experiments were performed in a series of self-designed， lab-scale plasma reactors to investigate the effects of coal properties and key operating conditions on the basic rules in coal pyrolysis to acetylene. The results revealed that the behavior of pyrolysis process relies on coals properties. A preliminary criterion for the industrial coal rank selection has been established on the basis of the achieved fundamental knowledge from the experiments. The relationship of coal devolatilization behaviors at different heating rates was discussed by comparing the gaseous products and solid residues， which helped to deeply understand the common rules in coal pyrolysis. The chemical percolation devolatilization （CPD） model was improved to predict the physical and chemical transformations of various kinds of coal based on the experimental data of coal pyrolysis. To better understand the complex gas-particle reaction behavior in the 2 MW and 5 MW pilot-plant plasma reactors， a comprehensive cross-scale computational fluid dynamics with discrete phase model （CFD-DPM） was established， with special consideration on coal chemical structure and particle-scale physics such as the heat conduction inside particle. The model predictions were in good agreement with the performances of the two pilot-plant reactors. The simulations revealed the detailed particle-scale heat transfer/devolatilization behavior and the scale-up effect.

Key Words：Coal； Acetylene； Thermal plasma； Computational Fluid Dynamics （CFD）