Reduction behavior and growth kinetics of metallic iron in slag bath of BGL coal gasifier

• Published in: Fuel (Guildford) Vol. 342; p. 127795
• Main Authors: Wu, Chuang, Lu, Hao, Bai, Jin, Kong, Lingxue, Wang, Ji, Huang, Lei, Feng, Wei, Yuan, Zongshuai, He, Chong, Guo, Zhenxing, Bai, Zongqing, Li, Huaizhu, Li, Wen
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.06.2023
• Subjects: BGL gasifier; Coal ash slag; Metallic iron; Reduction kinetics; Residual char; Coal ash slag; BGL gasifier; Residual char; Reduction kinetics; Metallic iron
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2023.127795

•The relative carbon content (α) had the strongest effect on the precipitation of iron in iron-rich industrial BGL slag at α=1.2.•With the increase in temperature and reduction time, the content and the average particle size of metallic iron increased.•The reduction behavior and particle growth can be divided into two stages: the rapid increase and stable stage.•The growth model of the metallic iron in slag under gasification conditions was established. The appearance of metallic iron reduced by residual char leads to the serious blockage and unpredictable shut-down of coal gasifiers, especially in moving bed slagging gasifiers. To prevent blockage, the reduction and growth characteristics of metallic iron are required to understand. In this study, slag mixed char and metallic iron from an industrial British Gas-Lurgi (BGL) coal gasifier was separated and analyzed to the properties of metallic iron formation process under gasification conditions. Results showed the relative carbon content (α) had the strongest effect on the content and average particle size of iron at α = 1.2 in this work. The reduction was weakened by poor mass transfer of reduction reaction when α > 1.2. The endothermic reduction reaction was promoted by the increase in high temperature. The iron precipitation and particle growth can be divided into rapid increase and stable stage with the increase of reduction time, corresponding to the reduction and accumulation of iron. The growth model of the metallic iron in slag under gasification condition was established as D = 4.439 × 10^10 × t^(1/1.190) × exp^(−340.716 × 10^3/RT) (t ≤ 900 s) and D = 4.277 × 10^14 × t^(1/3.580) × exp^(−412.253 × 10^3/RT) (t > 900 s, R2 = 0.9868). The growth model of metallic iron in slag can provide guidance for slag tapping operation of fixed-bed slagging gasifier during iron-rich coal gasification.