The importance of regeneration in wet flue gas desulfurization systems

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The wet desulfurization process for coke oven gas involves using an alkaline absorbent to absorb acidic gases such as H2S from the gas, and utilizing the properties of catalysts to catalytically oxidize H2S into elemental sulfur or sulfur-containing by-products. In systems that use complexed iron for desulfurization, the absorption process involves capturing H2S from the gas stream; gaseous hydrogen sulfide is ionized in the solution to form HS-, which is then catalytically oxidized by complexed iron (in the trivalent state) to produce a sulfur sol (with very small particles of elemental sulfur that are evenly dispersed in the solution). The complexed iron (trivalent state) itself is reduced to the divalent state ； During the regeneration process, on the one hand, the divalent iron complex is oxidized by air and regenerated, thereby restoring the catalyst’s activity; on the other hand, the elemental sulfur sol begins to aggregate, grow, and precipitate under the catalytic action of oxygen, and then floats to the surface. Therefore, if, during the desulfurization process, the load increases suddenly, there is insufficient regenerating air, or the regenerating effect of the injector is poor, the most obvious manifestation is a decrease in desulfurization efficiency; most directly, this results in an increase in hydrogen sulfide levels after desulfurization. If the problems of insufficient regeneration or poor regeneration efficiency of the equipment are resolved through judgment, inspection, and adjustment, the hydrogen sulfide levels downstream of the tower will gradually return to normal and remain within a certain range. If the desulfurization load increases, it is necessary to increase the amount of regenerative air; for systems that use spray regeneration, the solution circulation rate must be increased to boost the air intake, or additional compressed air may be supplied to assist with the regeneration process. In addition to promoting catalyst regeneration, another important function of the regeneration system is to achieve the flotation separation of sulfur produced by desulfurization. Theoretically, 1.57 Nm3 of air is required to remove 1 Kg of H2S, whereas in actual production the amount of air needed is more than 10 times the theoretical value; most of this excess air is used for the flotation of elemental sulfur. It emerges from the bottom of the regeneration tower along with the liquid and disperses; meanwhile, gas forms countless bubbles within the liquid. Under the surface tension of these bubble membranes, the elemental sulfur in the liquid moves toward the surface of the bubbles and adheres to them. Driven by their own buoyancy, these bubbles carry the sulfur particles toward the surface of the liquid, eventually forming a layer of sulfur foam on the surface. The sulfur foam that is formed must be allowed to flow out naturally over a certain period of time. Initially, the density of this newly formed sulfur foam is still lower than that of the liquid due to the presence of larger bubbles; however, as time passes, these bubbles will break apart, causing the foam to gradually become more dense. During this time, it is necessary to allow the sulfur foam to flow out, otherwise it will return to the solution and enter the desulfurization tower, increasing the load on the system and reducing the efficiency of desulfurization. Over time, this can even lead to blockages in the tower. Regeneration plays a pivotal role in the entire desulfurization process; it has a significant impact on both desulfurization and sulfur recovery, and is key to ensuring effective control of desulfurization