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首页> 外文学位 >Investigation into the roles of surface oxide complexes and their distributions in the carbon-oxygen heterogeneous reaction mechanism.
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Investigation into the roles of surface oxide complexes and their distributions in the carbon-oxygen heterogeneous reaction mechanism.

机译：研究表面氧化物配合物的作用及其在碳氧非均相反应机理中的分布。

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The combustion and gasification of chars are complex processes involving various subprocesses. These include mass and heat transfer to and from char particles, mass diffusion through the pores of the char, surface area evolution with char conversion, and heterogeneous reaction of gas molecules with sites and chemisorbed species on the internal surfaces of the char particle.; An extensive study was undertaken to characterize the intrinsic reactivity of char to oxygen. A variety of carbonaceous materials was employed in the study. The chars were subjected to a variety of heat treatment procedures, after which, oxy-reactivity tests were executed under kinetics-limited conditions using a pressurized thermogravimetric analyzer (PTGA). The PTGA system was also employed in performing BET-CO2 gas adsorption tests, which were used to determine the specific surface areas of chars during conversion.; A comprehensive char oxidation model was developed based on the results of the oxy-reactivity and surface evolution tests. The formulation includes an 11-step carbon-oxygen heterogeneous reaction mechanism and a surface area evolution model. The kinetic and pore structure parameters were carefully determined in order to reproduce the results of the oxy-reactivity and CO 2-adsorption experiments. The model was used to investigate the effects of surface oxide complexes and their distributions on char reactivity as well as to investigate the impact of surface area evolution on the char conversion process. A qualitative assessment of the impacts of inorganic matter and heat treatment was also performed.; The effect of surface area evolution was investigated by comparing a quasi-steady surface model with a dynamic surface model. It was demonstrated that the quasi-steady approximation resulted in an under-prediction of surface species, especially with increasing conversion. It was also demonstrated that activation energy distributions can characterize the reaction energetics of a char, and that approximating these distributions by average or effective activation energies can give rise to misleading results.; An increase in the inorganic composition of a char generally resulted in an increase in char reactivity. While some results suggested a decrease in char reactivity with heat treatment, other results suggest increase in reactivity due to heat treatment, an unexpected result that merits further investigation.
机译：炭的燃烧和气化是涉及多个子过程的复杂过程。这些包括质量和热量在焦炭颗粒之间的传递和传热，通过焦炭孔的质量扩散，随着焦炭转化的表面积演变以及气体分子在焦炭颗粒内表面上的位置和化学吸附物质的异质反应。进行了广泛的研究以表征炭与氧气的固有反应性。研究中使用了多种碳质材料。将炭进行各种热处理程序，然后，使用加压热重分析仪（PTGA）在动力学受限的条件下进行氧反应性测试。 PTGA系统还用于进行BET-CO2气体吸附测试，该测试用于确定转化过程中炭的比表面积。基于氧反应性和表面析出试验的结果，开发了一种综合的炭氧化模型。该配方包括11步碳氧异质反应机理和表面积演化模型。仔细确定了动力学和孔结构参数，以再现氧反应性和CO 2吸附实验的结果。该模型用于研究表面氧化物配合物及其分布对炭反应性的影响，以及研究表面积演变对炭转化过程的影响。还对无机物和热处理的影响进行了定性评估。通过比较准稳态表面模型和动态表面模型，研究了表面积演化的影响。结果表明，准稳态近似导致表面物种的预测不足，尤其是随着转化率的提高。还证明活化能分布可以表征炭的反应能量，并且用平均或有效活化能来近似这些分布会引起误导的结果。炭的无机组成的增加通常导致炭反应性的增加。虽然一些结果表明热处理会降低炭反应性，但其他结果表明由于热处理会提高反应性，这是一个令人意外的结果，值得进一步研究。

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