Characterization of Zinc Ferrite Sorbent Using Auger Electron Spectroscopy and Scanning Electron Microscopy

摘要

Samples of zinc ferrite pellets used in H sub 2 S sorption experiments were subjected to extensive surface analysis using Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM). The analysis indicates that hydrogen sulfide penetrated the pellets starting at the edges and through the cracks in the pellets. By the time H sub 2 S appeared in the effluent of the bed (50 ppM), a region of high-sulfur concentration had traveled 1.3 to 1.5 mm into the pellets at the bottom of the bed (introduction point for H sub 2 S-laden gas) and 0.2 to 0.5 mm into the pellets at 1 3/8 inches from the bottom of the bed. The sulfur was just penetrating into the edge of the pellets collected from heights of 3 3/4 inches and above in the bed. The boundary region between the high- and low-sulfur regions was discernable as a brightening in secondary electron micrographs. The presence of insulating oxide may be responsible for the detection of this boundary. The sulfur concentration in the high-sulfur region ranged from 14 to 40 mole percent, and from 0 to 10 mole percent in the low-sulfur region. The high-sulfur region observed in samples taken from 4 1/4 inches above the bottom of the bed were not uniform and did not follow any discernible pattern. This random distribution of high-sulfur levels may have resulted from the presence of large cracks in the pellets or structural changes taking place in the sorbent during the sulfidation. It was learned that the rate of absorption of H sub 2 S into the sorbent may be controlled by diffusion of H sub 2 S to the reaction sites. 4 refs., 13 figs., 6 tabs. (ERA citation 10:041118)