Causes of tower blockage in desulfurization systems and countermeasures

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Reasons for tower blockage 1: Control of indicators in the desulfurization system. 2. Heat in the liquid phase when the temperature is low. This item is listed separately because it is a common practice among nitrogen fertilizer manufacturers at present; perhaps it is the only option available, or maybe they have not yet realized the harms of doing so. 3. Selection of components for the desulfurization tower. 4. The appropriate desulfurizer was not selected. 5. The regeneration effect is poor, and the sulfur content in the depleted solution is high. 6. Quality of sulfur recovery. 7. Dust removal efficiency of the previous section. Countermeasure 1: Strictly control various process parameters. Temperature is a key factor for the proper operation of the desulfurization system; low temperatures result in high liquid viscosity, leading to poor desulfurization efficiency, while high temperatures cause the formation of more by-products, which also hinders the absorption of H2S. Experiments have shown that as long as the temperature of the desulfurization solution is above 45°C, the formation rates of Na2S2O3 and Na2SO4 increase sharply. Furthermore, when the regeneration temperature is too high, excessive bubbles form in the regeneration tank, making it difficult to aggregate and float sulfur particles, which results in a gradual increase in suspended sulfur in the lean solution. The desulfurization temperature should generally be maintained between 38°C and 42°C; it should not be lower than 35°C, nor higher than 45°C. pH value is also an important factor in chemical reactions; the pH of the regeneration solution must be strictly controlled in the desulfurization process, generally keeping it between 8.2 and 8.8. In production, efforts should be made to avoid a pH level higher than 9.0. When the pH value of the solution is greater than 9.2, the formation rate of by-products also increases linearly. The main components of the desulfurization solution need to be adjusted in a timely manner according to the production process, while strictly controlling the levels of suspended sulfur and by-products in the solution. 2. Reasonable methods for raising temperature: Many enterprises, especially those in the north, use steam heaters to heat the desulfurization liquid in order to raise its temperature during the cold winters; steam is used directly to heat the desulfurization liquid. Some other companies add steam coils at the bottom of the regeneration tank or introduce steam directly. 3. Replacing the packed tower with a spray air tower: In the wet oxidation method for desulfurization, traditional packed towers are still the most commonly used for absorption towers; only a distributor is installed at the top of the tower. The desulfurization liquid flows from top to bottom through the packing layer. Since the height of such towers can be several dozen meters, combined with the resistance posed by the coal gas, flow deviation can easily occur over time. Today, many nitrogen fertilizer manufacturers have carried out technical upgrades by adding redistributors above each layer of packing to reduce liquid skew flow, prevent the formation of dry zones, and effectively alleviate tower blockages. 4. Select high-quality catalysts: The choice of desulfurization catalysts will fundamentally determine key parameters such as desulfurization efficiency, auxiliary material consumption, and desulfurization costs. There are currently many types of wet desulfurization agents available in China. There is no fixed standard for selecting such agents; rather, the choice must be based on the existing process flow and equipment configuration, as well as the H2S content in the gas and the desulfurization targets that need to be achieved. 5. The inefficiency of the regeneration equipment lies in the fact that NaHS, which is formed when Na2CO3 absorbs H2S inside the tower, is not completely oxidized to elemental sulfur. This NaHS ends up in the foam tank as a result of flotation, and then is carried into the desulfurization tower, where the oxidation reaction takes place in the upper section of the tower, resulting in the formation of elemental sulfur that adheres to the surface of the packing. This is the main cause of blockages in the upper section of the desulfurization tower. 6 Improving the sulfur recovery process: The effectiveness of sulfur recovery directly reflects the amount of H2S that has been removed. Even if the desulfurization system is operating perfectly, if sulfur cannot be recovered, it must remain inside the tower, posing a risk of blocking the tower. Also, if the sulfur melting return fluid is fed back into the system, it is an important factor contributing to high levels of by-products in the solution. Many companies use continuous sulfur melting, and due to environmental and cost pressures, the liquid resulting from sulfur melting is usually returned to the system after being cooled. 7 Ensuring gas purity: It is well known that the gases entering the desulfurization system have a complex composition, containing numerous impurities and contaminants. Once these gases enter the desulfurization tower, it is difficult to remove them; they mix with the sulfur paste and can cause blockages in the tower. Typical packed towers are divided into 3 sections; if the pressure difference across the packing in the lowest section is high, it is most likely due to poor dust removal performance. Ensure the proper operation of the dust remover at the outlet of the gasification furnace, and remove ash on schedule. It is best for the gas generation circulating water to have micro-vortices. To operate an electrostatic dust removal device properly, it is necessary not only to maintain the secondary voltage and current of the electrostatic filter, but also to perform regular thermal cleaning of the filter, in order to minimize errors in the readings of the secondary voltage and current meters and thus avoid misjudgments regarding the efficiency of dust removal. Manage the circulating water in the scrubber towers and cooling and cleaning towers properly; companies that have the means should replace it frequently, and it is ideal to carry out both addition and discharge simultaneously. Summary: Desulfurization is a job that requires integrity. After the process and equipment are selected, the day-to-day management of minor details is also key to carrying out desulfurization effectively. Employees responsible for desulfurization not only need to have high professional skills, enabling them to analyze and solve problems, but also must possess a strong sense of responsibility. They need to be fully aware of the status of desulfurization processes at all times, able to identify issues that arise during production and take effective actions promptly.