An Experimental Investigation Of Desulfurization And Regeneration Of Fe-based Sorbents Supported On Lignite Char For Coke Oven Gas Cleaning

Efficient use of coal resources in China which mainly relies on coal for energy production is of great significance. With the rapid development of coking industry, more attention has been given to coke oven gas as a high calorific value source of energy and chemical raw materials. However, the development of China’s coking industry is restricted by the environmental pollution and low energy utilization. The sulfur species in coke oven gas is one of major air and environment pollutants which also cause corrosion in the downstream equipment and poison catalysts. Iron oxide is abundant, low-cost, and has high sulfur adsorption capacity. Therefore, iron based sorbent are promising for desulfurization gas streams. The regeneration and recycling of the deactivated sorbent is an effective way to reduce the cost and recover sulfur resource. By using steam, the sintering of the sorbent can be avoided effectively and the high concentration of H2 S can be obtained, which increases the sulfur recovery.Iron-based sorbent was chosen in this study. By loading of Zn and Cu to iron-based sorbents, active char supported Fe, Zn, Cu, Fe-Zn, Fe-Cu, and Fe-Zn-Cu sorbents were prepared by ultrasonic assisted co-precipitation method. Desulfurization and regeneration experiments of sorbents were carried out using a quartz fixed-bed reactor under ambient pressure. The effects of addition of Zn and Cu on desulfurization were investigated. The effects of regeneration conditions such as space velocity, temperatures, and steam content on the regeneration performance were also systematically studied, and the optimum regeneration conditions were confirmed.Multiple desulfurization-regeneration tests were carried out under the optimum regeneration conditions. For comparison, the regeneration of sulfidated sorbent with SO2 at the optimal experimental condition was also investigated and the results were compared with the steam regeneration. Elemental sulfur could be obtained during SO2 regeneration. However, a high SO2 concentration and long regeneration time were needed. The crystal structure and distribution of activated component and the physical structure of sorbents before and after regeneration were characterized by XRD, FTIR, SEM, XPS and BET surface area methods.The results showed that addition of Zn and Cu improved the sulfur uptake and breakthrough time, enhancing the sorbent performance. The char supported Fe-Zn-Cu sorbent showed the best desulfurization performance with 540 min breakthrough time and 217 mg S/g Sorbent sulfur uptake. The optimum regeneration space velocity, temperature, and steam partial pressure were 5000 h-1, 700 °C and 0.5 atm, respectively. The steam regeneration increased the porosity of the sorbents, enhancing the desulfurization performance of regenerated sorbent. The steam regenerated sorbent showed a stabile performance after several desulfurization-regeneration cycles.