Wesenauer Florian, Jordan Christian, Azam Mudassar, Harasek Michael, Winter Franz
Institute of Chemical, Environmental and Bioscience Engineering, Vienna University of Technology (TU Wien), 1060 Vienna, Austria.
Institute of Chemical Engineering & Technology, University of the Punjab, Lahore 54000, Pakistan.
Materials (Basel). 2021 Aug 30;14(17):4942. doi: 10.3390/ma14174942.
A series of porous clay samples prepared at different pretreatment temperatures have been tested in a diffusion chamber. Diffusivity and permeability were examined in a temperature range from ambient to 900 °C. Gaseous mixtures of O, CO, and N have been applied, as these species are the relevant gases in the context of clay brick firing and similar thermochemical processes. Diffusive transport characteristics have been determined by means of the mean transport-pore model, and permeability has been evaluated by Darcy's law. CO diffusivity increased strongly with temperature, whereas O diffusion was limited to a certain level. It is proposed that one should consider CO surface diffusion in order to explain this phenomenon. The diffusion model was expanded and surface diffusion was included in the model equation. The results of the model fit reflected the important role of incorporated carbonates of the clay foundation in gas-phase (molecular or Knudsen) diffusivity. CO surface diffusion was observed to exhibit similar coefficients for two different investigated clays, and is therefore indicated as a property of natural clays. Permeability showed a progressive rise with temperature, in line with related literature.
一系列在不同预处理温度下制备的多孔粘土样品在扩散室中进行了测试。在从环境温度到900℃的温度范围内检测了扩散率和渗透率。应用了O、CO和N的气体混合物，因为这些物质是粘土砖烧制及类似热化学过程中的相关气体。扩散传输特性通过平均传输孔隙模型确定，渗透率通过达西定律评估。CO扩散率随温度强烈增加，而O扩散限于一定水平。为了解释这一现象，建议考虑CO表面扩散。扩展了扩散模型并将表面扩散纳入模型方程。模型拟合结果反映了粘土基体中所含碳酸盐在气相（分子或克努森）扩散率中的重要作用。观察到两种不同研究粘土的CO表面扩散表现出相似的系数，因此表明这是天然粘土的一种特性。渗透率随温度逐渐升高，与相关文献一致。
