Ni-Zn-Fe复合氧化物脱硫剂再生研究

在固定床装置上考察了温度和O2浓度对溶胶-凝胶自燃法制备的Ni-Zn-Fe复合氧化物脱硫剂再生性能的影响,并进行了二次硫化实验;应用XRD、BET、SEM测试手段对新鲜脱硫剂及不同温度下再生后的样品进行了表征分析。结果表明,Ni-Zn-Fe复合氧化物脱硫剂在400℃下能够再生,而且体积分数为2%的O2对于该脱硫剂的再生较为合适,再生的脱硫剂具有良好的二次脱硫活性。再生后的XRD谱图与新鲜样品一致,且没有硫酸盐的生成;SEM测试结果显示,该脱硫剂在530℃或体积分数为4%的O2下再生发生严重烧结,基本没有二次脱硫活性。用收缩核模型对Ni-Zn-Fe复合氧化物脱硫剂的再生动力学行为进行了描述,发现其再生过程存在控制步骤由化学反应控制向扩散控制的转移。在反应起始阶段,受化学反应控制,化学反应活化能为27.16 kJ/mol,表观化学反应速率常数的指前因子为4.62 m/min;随着反应的进行,产物层逐渐增厚,再生过程受扩散控制,扩散活化能为40.37 kJ/mol,有效扩散系数的指前因子为0.49×10-3m2/min。

Study on regeneration of Ni-Zn-Fe based oxide desulfurizer

The regeneration characteristics of the Ni-Zn-Fe based oxide desulfurizer prepared by a sol-gel auto-combustion method were investigated. The effect of temperature and the concentration of O₂ on the regeneration behaviour were examined in a fixed bed reactor under atmospheric pressure. In addition, the second cycle desulfurization experiments were conducted. XRD, BET and SEM techniques were used to analyze and characterize the fresh and regenerated sorbent. The results show that the sorbent can be basically regenerated at 400℃. The sorbent shows good second cycle sulfidation reactivity after being regenerated with 2% of oxygen concentration at 400℃. X-ray powder diffraction patterns of the sorbent regenerated at 400℃ is almost same as that of fresh sorbent and no sulfate is generated. SEM results show that the sorbent regenerated at 530℃ or with 4% of O₂ (vol) concentration has been seriously sintered. Kinetic model tests show that the regeneration process can be well fitted by the shrinking core model. The kinetic controlling steps will transfer with the sorbent conversion. At the initial stage, the regeneration process is controlled by the chemical reaction, which has the activation energy of 27.16kJ/mol and the pre-exponential factor of 4.62m/min. As the reaction proceeds, the product layer is gradually thickened, and the regeneration process gets to being controlled by the diffusion through the reacted layers. The diffusion activation energy is 40.37kJ/mol and pre exponential factor is 0.49×10^-3m²/min.