Views on the common tower blockage problem in the wet catalytic oxidation method for gas desulfurization

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I’ve had some free time recently, so I’ve paid attention to my old field of work in gas desulfurization, particularly the wet catalytic oxidation method for desulfurization. It has been found that many people are troubled by the frequent clogging of desulfurization towers and the resulting increase in pressure. Moreover, people often attribute this problem to the high content of solid by-products in the desulfurization solution. In fact, upon careful analysis, it is not difficult to identify the real cause and address this issue at its root, so that this method can be applied more effectively. The process of desulfurization by wet catalytic oxidation is roughly as follows: The gas comes into contact with an alkaline desulfurization solution in the desulfurization tower, where the acidic hydrogen sulfide contained in the gas is removed, after which the gas proceeds to further processing stages. The desulfurization solution, in turn, passes through a regeneration tower where it reacts with oxygen from the air in the presence of a catalyst; as a result, the sulfides are converted into elemental sulfur, which is separated out, while the alkali is regenerated for reuse. Solving the tower blockage problem can be approached from two aspects: materials and equipment. Among these, the effect of the desulfurization liquid in blocking the tower is quite evident, as one can see that the liquid is turbid and not very clean; its ability to block the tower seems to be very significant. In fact, this is just one of the reasons for tower blockage. The solution to this problem is simply to filter the desulfurization liquid more thoroughly; both sulfur and by-products are substances that are relatively easy to filter out. If the filtering is done properly, and the reason is indeed that the desulfurization liquid is dirty, then this problem will be resolved. However, everyone should not overlook another factor that could also be the main source of blockages in the desulfurization tower: the gas itself. Most people reported that the substance blocking the tower was very dirty and black in color; it was likely tar and naphthalene residues from the gas. These substances are not as easily washed away by water as by-products; a large portion of them may not reach the filter and instead accumulate in the desulfurization tower, eventually causing the tower to become clogged. If such a problem does exist, it can be resolved by strengthening processes such as fire suppression and gas cleaning. Since both the gas and liquid phases are clean, won’t the tower be free from blockages? The answer is not necessarily. It also depends on what type of desulfurization tower you are using. It has been found that most manufacturers prefer to use packed towers. Why are packed towers chosen over other types such as spray towers or tray towers? The reason has not been found yet. However, easy clogging is a structural characteristic of packed towers. Spray towers and certain plate towers do not have this problem. Perhaps plate towers have issues such as high costs, more stringent operating requirements, and more complex design, but if the gas-liquid phases cannot be cleaned or purified properly, it might be advisable to consider using a different type of tower to address the problem at its root. Back then, I was involved in the design of a plate tower used for distilling mash to produce alcohol; the feed material was very dirty, but the tower worked quite well. Therefore, a technical and economic analysis should be conducted based on the specific circumstances to determine whether it is necessary to replace the tower in order to completely resolve the problem of tower blockage. It should be noted, however, that regardless of the type of tower, there is an issue related to the range of operational flexibility; if the operation is not carried out properly, even if the materials are very clean, there is still a risk of flooding. It is therefore important to maintain stable operations at all times. These days, CAPA (Corrective Action and Preventive Action) is emphasized; when addressing tower blockage issues, more attention should be paid to Preventive Action. It’s best to make tower blockage impossible. Some personal thoughts, for reference only