A numerical study on gasification of a single-pore char particle in supercritical water
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A numerical study on gasification of a single‑pore char particle in supercritical water Chao Fan1 · Hui Jin1 · Yunan Chen1 · Zhiwei Ge1 · Qiuyang Zhao1 Received: 24 December 2019 / Accepted: 13 February 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Gasification models of a char particle based on the true porous structure are essential for the accurate simulation of gasifiers, and pore-scale study might provide important information for the development of the porous char particle gasification models. In this paper, a numerical study was conducted on the gasification of a single-pore char particle in supercritical water, and the emphasis was put on the gasification process inside the pore with the effects of surrounding fluid, pore structure and pore position considered. The results showed that the gasification in a pore was quite affected by pore diffusion. The increase in temperature and particle Reynolds number promoted the gasification in the pore, and convection mainly enhanced the heat transfer but had limited promotion on mass transfer in kinetically controlled regime. Increasing pore length and decreasing pore diameter caused the increase in diffusion resistance and the former had more obvious effects. However, the decreased pore diameter increased the specific surface area and benefited the whole char conversion. The pore position affected the species distribution inside the pore for non-diffusive gasification, and the impact was limited in kinetically controlled regime. Finally, study in this work will be further extended to the gasification of the porous char particle. Keywords Supercritical water · Char gasification · Pore diffusion · Numerical simulation
Introduction Coal is the main energy source and will continue to play an important role in next decades in China [1]. Currently, however, traditional coal utilization way of burning coal in a boiler has caused severe environmental problems such as high emission of gas pollutants, dust and carbon dioxide, and the efficiency is difficult to be further improved [2, 3]. Thus, seeking for a clean and efficient coal conversion way is of great significance. Supercritical water gasification (SCWG) provides a promising option for the large-scale utilization of coal [4, 5]. In supercritical water (SCW), coal can be converted into hydrogen-rich gases efficiently, and pollutant elements are deposited and discharged in form of inorganic salts, owing to the excellent physical and chemical properties of SCW [6–8]. Besides, CO2 can be enriched by means of pressure * Hui Jin [email protected] 1
State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF), Xi’an Jiaotong University, 28 Xianning West Road, Xi’an 710049, Shaanxi, China
regulation at the gasifier outlet [9]. Thus, this technology will have broad market prospect. In research on SCWG, gasification behavior at the particle scale is the fundament of reaction-scale study. The gasification characteristics of solid particles can provide useful information for developing sub-models
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