低阶煤热解含尘焦油气品质调控及除尘分析

Quality control and dust removal analysis of dust-containing gaseous tar from low rank coal pyrolysis

  • 摘要: “双碳”背景下,以热解技术为核心的低阶煤分级分质转化利用对煤炭加工产业绿色低碳发展具有重要意义。针对低阶煤转化过程中存在的含尘热解焦油气高温除尘及品质调控等瓶颈问题,从煤热解和挥发物反应机理出发,阐述了含尘焦油气组成及挥发物反应特性等对焦油品质、析炭行为的影响,提出利用挥发物反应规律,通过煤种特性与工况条件的优化匹配,抑制含氧化合物对析炭形成的诱导作用,并对自由基碎片进行有效供氢,进而提高焦油品质,减少析炭形成,是有效缓解后续焦油气油尘分离压力的可行方法。并基于此,详细分析了热解焦油气除尘技术及焦油原位提质相关研究进展及技术应用情况,指出利用颗粒床除尘技术通过改变过滤材料的物理、化学特性和床层的空间效应调变挥发物反应路径,可实现高温含尘焦油气除尘和原位提质的协同效果。在保证焦油产率前提下开发适用于颗粒床过滤和焦油气原位提质的多功能介质材料尤为重要。多级孔炭基催化剂作为颗粒床过滤材料,在过滤粉尘的同时可实现重质组分裂解以及富氢组分活化的功能,既可减小重质焦油在孔结构中的传质阻力,又可通过活性位和孔隙结构的组合效应实现“同步供氢”,有效提质焦油并抑制析炭,有望为大规模粉煤热解及含尘焦油气高效气固分离技术的发展提供理论指导。

     

    Abstract: Under the background of “carbon peaking and carbon neutrality”, the grading and qualitative conversion of low-rank coal through pyrolysis as the core technology is of great significance to the green and low-carbon development of the coal processing industry. Aiming at the bottleneck problems of high temperature dust removal and quality control of dust-containing pyrolysis tar, the mechanism of coal pyrolysis and volatiles’ reaction is first analyzed, and the effect of dust-containing gaseous tar composition and volatiles’ reaction characteristics on the tar quality and carbon deposition behavior is discussed. Based on the mechanism of volatiles’ reaction, it is proposed to suppress the induction effect of oxygenated compounds on the formation of coke and to supply effective hydrogen to free radical fragments by optimally matching the coal characteristics and operating conditions. Ultimately, the tar quality is improved, and the coke deposition is reduced, thus, a feasible method to effectively relieve the separation pressure of oil and dust in subsequent gaseous tar is put forward. Based on the above method, the related research progress and technical application of dust removal technology and the in-situ upgrading of pyrolysis gaseous tar are analyzed in detail. It is pointed out that the use of granular bed dust removal technology can adjust the volatiles’ reaction path by changing the physical and chemical properties of the filter material and the spatial effect of the packed bed, so as to achieve the synergistic effect of the dust removal and in-situ upgrading of dust-containing gaseous tar. It is particularly important to develop multi-functional media materials suitable for the granular bed filtration and in-situ upgrading of gaseous tar under the premise of ensuring tar yield. As a granular bed filter material, the hierarchical porous carbon-based catalyst can realize the cracking of heavy components and the activation of hydrogen-rich components while filtering dust. In this case, the mass transfer resistance of heavy tar in the pore structure is reduced and the “synchronous hydrogen supply” through the combined effect of active sites and pore structure is also achieved, leading to an effective upgrading of tar quality and inhibiting of coke. The study provides a theoretical guidance for the development of large-scale pulverized coal pyrolysis and the efficient gas-solid separation technology of dust-containing gaseous tar.

     

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