With an imported catalyst conversion unit, how often should the bottom screen be replaced?
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In units that use imported catalysts, the bottom temperature of the first layer is maintained at 630–640°C, while that of the second layer is 560°C. How often should the bottom screens be replaced? Initially, our units used screens made of 321 material, and these were replaced every 6 years. The mesh currently in use is made of 310S material. The other layers are made of 304 material and have not been replaced. What is the frequency at which the wire mesh at the bottom of each conversion layer needs to be replaced in various sulfuric acid systems? Let’s take that as a reference
In chemical processing equipment, conversion units that use imported catalysts are typically a key component in sulfuric acid plants; they are responsible for converting SO2 into SO3, thereby producing sulfuric acid. The bottom mesh plays a role in filtration and catalytic support during this process, ensuring the uniform distribution and effective utilization of the catalyst. Therefore, the integrity and performance of the screen are directly related to the conversion efficiency and product quality. The cycle for replacing the bottom screen depends on various factors, including: 1. Screen material: Different materials have varying levels of corrosion resistance and heat resistance; for example, 310S offers better high-temperature and corrosion resistance compared to 321 and 304. 2. Operating temperature: You mentioned that the temperature at the bottom of the first layer should be maintained between 630–640°C, and that of the bottom of the second layer at 560°C. These are relatively high temperatures, and they can affect the lifespan of the screen. 3. Quality of catalyst and raw materials: If the raw materials contain high levels of impurities, or if there are issues with the catalyst itself, it may lead to premature wear or damage of the screen. 4. Equipment operating conditions: pressure fluctuations, mechanical shocks, as well as the frequency of cleaning and maintenance, can all affect the service life of the screen. Given that you used screens made of material 321 and had to replace them every 6 years, switching to screens made of material 310S should result in a longer service life; however, the specific replacement interval still needs to be determined based on actual operating conditions and equipment maintenance records. Generally, it is recommended to inspect the screen regularly; once obvious deformation, damage, or corrosion is detected, replacing it should be considered. As for the time required to replace the bottom mesh at each layer in other sulfuric acid systems, this figure may vary from one plant to another, depending on the various factors mentioned above. The best approach is to contact other sulfuric acid producers or specialized equipment suppliers to learn about their maintenance experience and maintenance schedules. At the same time, it is also possible to refer to the recommendations and guidelines provided by the equipment manufacturers, and determine the replacement cycle based on the actual conditions of one’s own factory. .
Just check it whenever the catalyst is screened each year
We used 304 as well, and it wasn’t replaced regularly.
It’s a 316 model; I’ve been using it for 8 years without replacing it. It works very well.
The service life of the conversion support screen is still largely dependent on operating conditions; frequent start-up and shutdowns, especially frequent short-term hot shutdowns, can lead to the formation of condensed acid in the first or second stage, which causes corrosion to the support screen.
Inspection during major maintenance showed no corrosion (narrowing) or deformation; no replacement is required. It’s a 10-year-old unit, and the sieve screen still has its original luster after inspection.