Points to note in wet flue gas desulfurization

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Any desulfurization system involves three key elements: regeneration balance, sulfur balance, and water balance. Regeneration equilibrium refers to the process of regenerating the catalyst with sufficient air, and it is also the process by which elemental sulfur floats normally to form foam that is then discharged from the system. When the foam is not functioning properly, it is necessary to identify the cause promptly and take appropriate actions to restore normal operation as soon as possible. For example, in cases where the foam is weak or contains liquid, or there is no foam at all, and when the cause is unknown, it is generally advisable to first reduce the amount of regenerative air flow (jet regeneration can block the air intake ports, while high-tower regeneration involves simply reducing the flow rate of compressed air); only as a last resort should the circulation volume be reduced. Reducing the air flow usually helps to prevent foam from escaping from the tank. This thus provides the time to address the problem. The reduced circulation rate must be restored as soon as possible to ensure that it meets the process requirements. The sulfur balance refers to the equilibrium between the removal of hydrogen sulfide by the desulfurization system and the production of sulfur. The absorption process is related to catalyst performance, system temperature, and the environment in which the catalyst operates (including the alkalinity of the desulfurization solution and its oil and dust content). Common issues include foam treatment, the suitability of the equipment, the reliability of the process flow, and the skill level of the operators. When there is excessive foam and the level of the foam tank is high, post-treatment measures should be considered first; it is possible to control foam overflow in the short term. The desulfurization system should avoid using reduced circulation volume to control foam flotation. Reducing the circulation volume to control foam flotation means that a large amount of foam remains in the desulfurization tower and settles at the bottom of it; if not dealt with promptly, there is a risk of blockage. With no change in catalyst stability, the abnormal foam is primarily attributed to desulfurization fluid poisoning, which requires prompt classification and treatment. Water balance is the lifeblood of the desulfurization system; the control system generally maintains water balance or a slight deficit. A slightly negative system liquid level is beneficial for the stability of the tri-salt and catalyst concentrations, as well as for the efficiency of hydrogen sulfide absorption. If the system continues to lose fluid, it is necessary to add water; desalinated water is the best choice for this purpose. Adding water once or twice will inevitably result in an accumulation of large amounts of calcium and magnesium ions within the system, which eventually leads to the formation of insoluble salt deposits on the surface of the fillers or to blockages in the nozzles. Peripheral desulfurization liquid or water of unknown composition must be utilized in a targeted and appropriate manner through analysis and testing; substances such as certain wastewater treatment agents and tar should not be added to the desulfurization liquid, as this can disrupt the system’s dynamic balance and cause unnecessary problems due to foam instability and the accumulation of clear liquid. For whatever reason, the system must maintain a relatively stable flow rate; with this flow rate as the key factor, any elements that deviate from it must be corrected promptly. Once the circulation volume deviates from the normal value, it is a very serious incident. As environmental regulations become increasingly stringent, the importance of desulfurization becomes ever more prominent. Desulfurization is not actually simple; it requires patience and perseverance. One needs to take the time to observe the system, identify problems promptly and address them in the correct manner, so as to ensure the long-term stable operation of the equipment.