Study on the Pore Evolution of Pyrolysis Lignite via the Cubic Spline Interpolation Function Model Based on 1H-NMR Experimental Data
TENG Yingyue1,2, HOU Xingcheng1,2, BAI Xue1, LIU Quansheng1,2, LI Yi1,WU Kan1, ZHU Zhicheng1
1 College of Chemical Engineering, Inner Mongolia University of Technology, Huhhot 010051, China 2 Inner Mongolia Key Laboratory of High-value Functional Utilization of Low Rank Carbon Resources, Inner Mongolia University of Technology, Huhhot 010051, China
Abstract: The pores in lignite are important factors affecting their physical properties. In this work, the low field nuclear magnetic resonance (1H-NMR) technique was used to obtain the discrete data of the pore characteristics of lignite at different temperatures. Secondly, based on these discrete data, a cubic spline interpolation function model was constructed, and the new aperture distribution data different from the discrete data was obtained through the constructed function model. Finally, the new pore size distribution data obtained by the function model is compared with the experimental data, and the prediction accuracy of the function model was analyzed, the temperature threshold range is mainly investigated, and the reasons for the variation of the pore size distribution were analyzed from the physicochemical point of view. The results show that with the increase of experimental temperature, the pore structure of Shengli lignite mainly exists in the form of small pores (10—100 nm) and macropores (100—1 000 nm) below 200℃, micropores (<10 nm) and cracks (>1 000 nm) are mostly in the range of 200—500℃, and more cracks are generated at 715—950℃, which generally move toward the macropores and cracks. The function model can accurately predict the pore size distribution and temperature threshold based on 1H-NMR data. When predicting the overall pore size distribution of pyrolysis lignite, the root mean square error (RMSE) of the predicted value is small when the temperature is lower than 550℃, and the RMSE of the predicted value is larger when the temperature is higher than 550℃ compared with the experimental data. When predicting the proportion of pore size distribution of diffe-rent sizes, the error value of the micropore is only within 3.09%, the error of the small pore is within 0.85%—22.12%, and the error of the macropore is within 0.18%—7.95%. The ratio of the crack is within 4.43%, and the precision of forecasting is better. The model predicts that the temperature threshold of the pore size distribution of heat-treated lignite within 200—300℃ is 250℃, which is more suitable for the test results. The predicted temperature threshold of the model within 500—950℃ is 715℃, which is different from the temperature threshold of 700℃ obtained by the test results. It is caused by the model predicting the large RMSE of the overall pore size distribution of the heat treated lignite at 700℃. The model prediction results show that the cubic spline interpolation model has better prediction accuracy for the pore size distribution of different temperature pyrolysis lignite coal samples.
滕英跃, 候星成, 白雪, 刘全生, 李毅, 吴侃, 朱志成. 基于1H-NMR实验数据的三次样条插值函数模型对热解褐煤孔隙演化的研究[J]. 材料导报, 2020, 34(18): 18074-18080.
TENG Yingyue, HOU Xingcheng, BAI Xue, LIU Quansheng, LI Yi,WU Kan, ZHU Zhicheng. Study on the Pore Evolution of Pyrolysis Lignite via the Cubic Spline Interpolation Function Model Based on 1H-NMR Experimental Data. Materials Reports, 2020, 34(18): 18074-18080.
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2020, Vol. 34 
