Pore Structure and Fractal Characteristic Analysis of Gasification-Coke Prepared at Different High-Temperature Residence Times

Abstract

An accurate and quantitative description of the pore structure of gasification-coke using fractal geometry could be of great significance to its industrial utilization. In this study, gasification-coke was prepared with low-quality coal blending at different high-temperature residence times to investigate the variation in the pore structure, fractal dimensions, reactivities, and their relationship. The pore structure parameters (e.g., specific surface area, pore volume, and average pore diameter) of gasification-coke were investigated by low-temperature N 2 adsorption/desorption and mercury intrusion porosimetry. Fractal dimensions D 1 and D 2 (at relative pressures of 0–0.5 and 0.5–1, respectively) were calculated using the fractal Frenkel–Halsey–Hill model, and the fractal dimension D 3 was obtained using the Menger sponge model. The results show that the pore structure systems of gasification-coke prepared at different high-temperature residence times are continuous and complete, which contributes to the gasification reaction. The variation trend of the macropore structure parameters is more complex than that of micropore and mesopore with the extension of the high-temperature residence time. It is found that D 1 is linearly correlated with the micropore specific surface area, indicating that D 1 is more suitable for reflecting the roughness of the micropore surface; D 2 is linearly correlated with the mesopore volume and can describe the volumetric roughness of the mesopore; and D 3 reflects the irregularities and surface roughness of the macropores. Gasification reactivity is closely related to the D 2 value, and the reactivity of the gasification-coke may be improved if the number of mesopores is increased by controlling the high-temperature residence time or other pyrolysis conditions. The research results will provide theoretical reference for controlling the gasification reaction of gasification-coke and gasifier design.

Pore Structure Characterization of Eocene Low-Permeability Sandstones via Fractal Analysis and Machine Learning: An Example from the Dongying Depression, Bohai Bay Basin, China

“…According to fractal theory, self-similar fractal behavior does not change with the scale of magnification. 10 , 22 , 41 Since its introduction by Mandelbrot in 1977, it has been widely used in pore structure evaluation and characterization. 42 , 43 The self-similarity behavior of pore structures can be illustrated by eq 1 .…”

“…The traditional methods such as the Euclidean geometry and experimental techniques are no longer effective in characterizing and evaluating complex and heterogeneous pore structures . Numerous studies have demonstrated that pore structures in porous rocks are self-similar and do not change with investigation scales. ,, By applying the fractal theory, complex pore systems can be quantitatively investigated, − and the fractal dimensions obtained can also be applied for reservoir quality evaluation and estimation of petrophysical properties . Fractal analysis has been shown to be especially suitable for characterizing low-permeability terrestrial sandstones that have undergone complex diagenetic modifications …”

Influence of Temperature and CO2 on High-Temperature Behavior and Microstructure of Metallurgical Coke

“…19 After the reaction of coke with CO 2 , the change in big pores is much more complicated than that in small pores. 20 The minerals in coke, such as Ca and Fe, enhance the gasification. Specifically, Ca has a higher influence on the gasification of coke.…”

“…The changes in the coke structure and pore due to the gasification reaction lead to changes in the coke strength after gasification . After the reaction of coke with CO 2 , the change in big pores is much more complicated than that in small pores . The minerals in coke, such as Ca and Fe, enhance the gasification.…”

Pore structure characteristics and fractal structure evaluation of medium- and high-rank coal

“…The present work is closely related to two streams of literature: coal pore structure characteristics and coal fractal characteristics. In the study of Guo et al (2020), low quality blended coal is used as raw material to prepare gasified-coke under different residence time, and the changes of pore structure and fractal dimension are investigated. Their findings indicate that the pore structure characteristics, such as specific surface area, pore volume, and average pore diameter, at different residence times are continuous and complete.…”