SO₂ Removal from Flue Gas by Char-Supported Fe-Zn-Cu Sorbent

In this study, the mechanisms of SO₂ adsorption on lignite char and char-supported Fe-Zn-Cu sorbent (FZC sorbent) were investigated. The FZC sorbent was prepared by the impregnation of metal components on raw coal followed by steam gasification. Flue gas desulfurization experiments were carried out on a fixed-bed reactor at 100-300 °C by using simulated flue gas containing SO₂/O₂/H₂O balanced by N₂. The flue gas composition was monitored by using an online flue gas analyzer. The solid samples before and after desulfurization were analyzed by using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetric Analysis-Mass Spectroscopy (TG-MS), and Brunauer-Emmett-Teller (BET) surface area analysis. The experimental results showed that both lignite char and the FZC sorbent can effectively adsorb SO₂ under the present experimental conditions. The presence of O₂ and H₂O in the flue gas promoted the adsorption of SO₂ on the FZC sorbent. The SO₂ adsorption capacity of the FZC sorbent increased with the increase in the temperature up to 250 °C. When the temperature was further increased to 300 °C, the SO₂ adsorption capacity of the sorbents decreased rapidly. Under optimum experimental conditions with a space velocity of 1500 h^-1, a desulfurization temperature of 250 °C, and 5% (vol) O₂ and 10% (vol) H₂O in the flue gas, the sorbents exhibited the longest breakthrough time of 280 min and breakthrough SO₂ adsorption capacity of about 2200 mg (SO₂) per gram sorbent.