熱等離子體煤裂解制乙炔的轉(zhuǎn)化規(guī)律與定向控制

程易顏++彬航++張樂++程炎

摘 要：煤炭資源的清潔、高效轉(zhuǎn)化和利用是緩解石油資源短缺、保障我國能源安全的關(guān)鍵。熱等離子體煤裂解一步法制乙炔工藝具有流程短、水耗少、碳排放低等特點，是一條極具前景的煤直接轉(zhuǎn)化路線。該過程在超高溫下實現(xiàn)煤粉的毫秒級轉(zhuǎn)化，目前國際上尚未實現(xiàn)工業(yè)化。該研究實驗和理論并重，研究了等離子體反應(yīng)器內(nèi)煤粉的裂解特性及復(fù)雜的氣固流動和反應(yīng)行為。該研究自主設(shè)計、開發(fā)了等離子體煤裂解實驗裝置，考察了典型煤種的超高溫裂解特性。實驗結(jié)果表明了過程的煤質(zhì)依賴性，為工業(yè)過程的煤種篩選提供了科學(xué)方法和實驗依據(jù)。通過對不同升溫速率下的煤粉熱解情況的考察比較，全面認(rèn)識了煤的熱解特性，為快速熱解選煤實驗平臺提供了理論基礎(chǔ)。基于大量熱解實驗數(shù)據(jù)改進了煤粉脫揮發(fā)分動力學(xué)模型，使其具有良好的煤種適用性和預(yù)測精度；進而建立了耦合煤質(zhì)分子結(jié)構(gòu)、顆粒內(nèi)部傳熱、顆?！黧w間傳熱—反應(yīng)等要素的跨尺度氣固反應(yīng)流動模型，實現(xiàn)了對2 MW和5 MW工業(yè)反應(yīng)器內(nèi)煤粉裂解行為的三維復(fù)雜熱態(tài)模擬，與工業(yè)反應(yīng)器的運行數(shù)據(jù)符合良好，準(zhǔn)確地揭示了反應(yīng)器的放大效應(yīng)和過程的顆粒尺寸依賴性。

關(guān)鍵詞：煤 乙炔 熱等離子體 計算流體力學(xué)

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）