Reaction mechanism for syngas preparation by lignite chemical looping gasification using phosphogypsum oxygen carrier

In this study, syngas preparation by chemical looping gasification (CLG) process is investigated through theory and experiment. The starting materials for the syngas are low quality lignite, which cannot be used for other applications, and phosphogypsum (PG), the byproduct of wet phosphoric acid. The results show that the CO production is mainly due to the following reaction: (CaSO4 + 4C → CaS + 4CO) and (C + CO2 → 2CO), while the main reactions of H2 generation are (CO2 + H2O(g) + 2CH4 → 3CO + 5H2) and (C + H2O(g) → CO + H2). The analysis results indicate that high temperature and water vapor content are detrimental for phosphogypsum recycling. Furthermore, after three times recycling of phosphogypsum, some sintering is observed. The composition of syngas is very important for the corresponding applications. Therefore, the relationships between reaction factors and products are also investigated. The results of Analysis of Variance (ANOVA) show that H2 and CH4 generation are strongly dependent on water v...