铁基载氧体的污泥化学链气化过程中氮迁移热力学模拟与实验研究

基于吉布斯自由能最小化原理,采用HSC Chemistry 6.0软件,对污泥化学链气化过程中NO_x前驱物（NH₃和HCN）与Fe₂O₃载氧体的氧化还原行为进行了热力学模拟。基于污泥热解实验中NO_x前驱物的含量,计算载氧体与污泥的摩尔比（OC/SS）对NH₃、HCN以及NH₃和HCN混合气氧化过程的影响。热力学模拟结果表明：Fe₂O₃能显著促进NO_x前驱物的氧化和裂解,主要生成N₂,几乎无NO_x生成;当NH₃、HCN以及混合气（NH₃和HCN）分别作为还原剂时,其最优OC/SS分别为0.02、0.04和0.05;由于HCN还原性强于NH₃,其氧化速率较快。基于Fe₂O₃/Al₂O₃混合物（FeAl）载氧体,实验对比了污泥化学链气化与污泥热解过程中NO_x前驱物的释放特性,发现Fe₂O₃能显著降低烟气中NO_x前驱物的产率,NH₃和HCN产率分别下降32%和62%。实验结果与热力学模拟结果一致。

Thermodynamic Analysis and Experimental Study of Nitrongen Migration during the Sludge Chemical Looping Gasification Using Iron-Based Oxygen Carriers

Based on the Gibbs free energy minimization principle, thermodynamic analysis and process simulation of the redox reactions between the NO_x precursors (NH₃ and HCN) and Fe₂O₃ (oxygen carrier) during the sludge chemical looping gasification were performed using the software of HSC Chemistry 6.0. According to the content of NO_x precursors during the sludge pyrolysis, the effect of the molar ratio of oxygen carrier to the sludge (OC/SS) on the oxidation of NH₃, HCN, and the mixed gas of NH₃ and HCN were investigated. The simulation results showed that the oxidation of NO_x precursors was effectively promoted by Fe₂O₃, the N element was mainly converted to N₂ and almost no NO_x was formed. The OC/SS ratio of 0.02, 0.04, and 0.05 were determined to achieve the complete conversion of NO_x precursors as well as minimize the amount of oxygen carrier when the NH₃, HCN, and the mixed gas of NH₃ and HCN were used as the reductants, respectively. Additionally, the oxidation rate of HCN was higher than that of NH₃ due to the stronger reducibility of HCN. Furthermore, the yields of NO_x precursors during the sludge pyrolysis and the sludge chemical looping gasification were compared in a fixed bed. It was found that the yields of NO_x precursors in the flue gas were significantly reduced by Fe₂O₃, and the yields of HCN and NH₃ decreased by 62% and 32%, respectively. The thermodynamic analysis was validated by the experiment results, and the chemical looping gasification of sludge was beneficial to inhibit the generation of the NO_x.