Common problems and solutions in the operation of single-tower desulfurization units

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The tower-type desulfurization unit without a reaction tank is quite popular due to its advantages such as small footprint, low investment cost, and easy operation. It is particularly widely used in the desulfurization of coal gas within the coking industry. Some problems may arise during operation: I. Issues with the equipment and their solutions: 1. Selection of the head capacity for the mother liquor pump: It is advisable to use a pump with high flow rate but low head capacity, in order to prevent the motor from experiencing excessive current and getting damaged. For example, the desulfurization tower of a certain coking plant is 43 meters high; pumps with a head of 80–85 meters are generally used for this purpose. To make use of existing equipment, an old pump with a head of 120 meters is employed. It is necessary to control the flow rate of this pump, as any mistake could lead to damage to the motor. It was later changed to a mother liquor pump with a head of 82 meters, and everything is working normally now. 2. Jet selector: Since different catalysts require varying amounts of oxygen for regeneration, it is necessary to engage professional design and manufacturing firms to carry out the design and production process, in order to avoid shoddy work that would result in suboptimal performance, low air intake, frequent blockages in the throat and tail pipes, and poor regeneration effects ； Factors that are detrimental to production include high hydrogen sulfide levels, increased catalyst consumption, and heavy maintenance workload later on. For example, in a certain coking plant, the reducer inside the injector had welds; upon inspection after it was opened, it was found that this reducer had been manufactured by the construction team itself to save costs – it was not a standard part. As a result, liquid splashed out during the operation of the injector, causing sulfur paste or salt crystals to accumulate frequently on the interior surfaces of the components and the air chamber, leading to severe backflow of liquid. This situation made it impossible to meet the requirements for regeneration, forcing the use of forced air supply as a means to compensate for the insufficient regeneration process. 3. Mother liquor heat exchanger: Spiral plate heat exchangers are commonly used for this purpose. Due to differences in water quality, active sludge accumulates on the walls of the refrigerant tank, which affects the heat exchange efficiency; as a result, the temperature of the desulfurization liquid does not drop, leading to imbalances in the parameters of the desulfurization system. If offline cleaning disrupts production, some manufacturers use compressed air to regularly blow away the activated sludge adhered to the inner walls, and this method also proves effective ； Some manufacturers also install a secondary line for reverse flushing on the refrigerant pipeline, and waste discharge is another good option. Of course, the best option is to hire a professional cleaning company to do the cleaning. II. Process-related issues and solutions 1. In a one-tower desulfurization unit without a reaction tank, the catalyst containing complexed iron is usually added at the bottom of the tower. The short reaction time at the bottom makes it difficult to control the levels of salts; therefore, the liquid level at the bottom should be kept as high as possible to allow the liquid to have the maximum possible reaction time. 2. The single-tower desulfurization unit has a short process flow and a small liquid storage capacity; as a result, high operational precision is required, otherwise operational accidents are likely to occur. Make frequent adjustments and operate with care to prevent operational accidents such as foam escaping from the channel or the tower bottom being submerged. Its greatest advantage is that when the desulfurization liquid becomes contaminated by impurities such as tar, preventing the foam from floating properly or reducing the desulfurization efficiency, the system can quickly return to normal by replacing a small amount of the desulfurization liquid and adding a small amount of catalyst, which verifies the old saying that a small boat is easy to maneuver. In summary, for each single-tower desulfurization unit, through experimentation after it is put into operation, the problems that arise with the process and equipment can be continuously addressed, allowing for the development of an appropriate operating mode that enables the system to reach an ideal operating condition and ensures its stability and reliability.