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.