Regeneration of Fe-Zn-Cu sorbents supported on activated lignite char for the desulfurization of coke oven gas

In this paper, the regeneration characteristics of activated-char-supported Fe-Zn-Cu sorbents were studied. The desulfurization and regeneration experiments were carried out using a quartz fixed-bed reactor at ambient pressure. The effects of regeneration conditions, such as space velocity, temperature, and steam concentration, on the regeneration performance were examined. The crystal phase, chemical structure of activated components, and physical structure of sorbents before and after regeneration were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area. The experimental results indicated that the char-supported Fe-Zn-Cu sorbents can be regenerated at temperatures above 500 °C. The optimal regeneration parameters with a space velocity of 5000 h^-1, temperature of 700 °C, and steam concentration of 50 vol % have been obtained. The result of regeneration by steam suggested that the BET surface area of the sorbent after regeneration was larger than that of the fresh sorbent, and steam can restore the physical structure of the sorbent and expand its aperture during regeneration. Regeneration using SO₂ was also studied under the optimal conditions. The XRD, FTIR spectroscopy, and XPS analyses indicated that the composite metal oxides in the sorbent formed during sulfidation were transformed into metal sulfides, which can be converted back to metal oxides during regeneration.