Abstract: Coal-direct chemical looping (CDCL) is a promising CO₂ capture technology with low costs. Potassium modification can significantly enhance the reactivity of iron-based oxygen carriers and coal. However, potassium loss causes a decline in cyclic stability. To address this, we prepared a potassium hexatitanate-modified iron-based OC and conducted CDCL experiments in a fixed-bed reactor using Zhundong coal coke as fuel. The study examined the impact of potassium hexatitanate on carbon conversion, OC activity stability, and potassium maintenance. Additionally, FactSage was used to calculate potassium fugacity patterns at different temperatures, Fe₂O₃/C molar ratios, and OC reduction degrees. Results showed that potassium hexatitanate increased carbon conversion, achieving 50% conversion at 40% potassium addition. In multi-cycle tests, carbon conversion rose with increased cycle times, reaching 84%. This improvement is attributed to ion exchange between Fe³⁺ and Ti⁴⁺, which induces lattice distortion and creates oxygen vacancies, enhancing OC reactivity. Potassium content remained stable during multi-cycle tests, indicating the effective potassium retention capacity of potassium hexatitanate.

Key words: Coal-direct chemical looping combustion, Iron-based oxygen carrier, K₂Ti₆O₁₃, FactSage simulation

摘要： Coal-direct chemical looping (CDCL) is a promising CO₂ capture technology with low costs. Potassium modification can significantly enhance the reactivity of iron-based oxygen carriers and coal. However, potassium loss causes a decline in cyclic stability. To address this, we prepared a potassium hexatitanate-modified iron-based OC and conducted CDCL experiments in a fixed-bed reactor using Zhundong coal coke as fuel. The study examined the impact of potassium hexatitanate on carbon conversion, OC activity stability, and potassium maintenance. Additionally, FactSage was used to calculate potassium fugacity patterns at different temperatures, Fe₂O₃/C molar ratios, and OC reduction degrees. Results showed that potassium hexatitanate increased carbon conversion, achieving 50% conversion at 40% potassium addition. In multi-cycle tests, carbon conversion rose with increased cycle times, reaching 84%. This improvement is attributed to ion exchange between Fe³⁺ and Ti⁴⁺, which induces lattice distortion and creates oxygen vacancies, enhancing OC reactivity. Potassium content remained stable during multi-cycle tests, indicating the effective potassium retention capacity of potassium hexatitanate.

关键词: Coal-direct chemical looping combustion, Iron-based oxygen carrier, K₂Ti₆O₁₃, FactSage simulation