How to prevent scaling on the trays of the methanol water separation tower?
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As the title suggests, I was wondering if anyone has encountered the problem of scaling on the trays of methanol-water separation towers, and what preventive measures have been taken? How is it implemented specifically?
The situation here is also serious; mainly, there’s too much ash in the gasification zone
This post was last edited by 654262293 on 2016-6-15 at 10:57: 1. The system must be thoroughly purged when first started up, and the washing with water must be thorough. 2. Enhanced filtration is required for methanol-rich and methanol-poor streams. 3. For the body of the methanol-water separation tower, its internal components should be made of stainless steel. The exhaust gas washing tower, made of carbon steel, requires anti-corrosion treatment; its internal components as well should be made of stainless steel. The pipelines that carry washing water to the methanol-water separation tower must also be made of stainless steel. 4. After washing with water during maintenance, dry it promptly; after introducing oxygen, replace it with nitrogen immediately. 5. Strictly control the water content in the circulating methanol.
After prolonged operation, a layer of scale forms on the trays, which causes the floating valves on these trays to get stuck and unable to move up and down freely. This reduces the operational flexibility of the water separation tower. Are there any effective ways to prevent scaling on the trays? The pH value of the wastewater was just analyzed to be 6.66, with calcium ions at 1.61 mg/L.
Do you have a alkali addition pipeline in your design?
This post was last edited by 654262293 on 2016-6-15 at 15:25. There are basically no good solutions once scaling occurs; the key is prevention. If it’s caused by calcium ions, it’s necessary to identify their source so that appropriate measures can be taken. The source is mainly determined by checking the washing water from the ammonia washing tower, the desalinated water from the exhaust gas washing tower, or the feed gas, to see which one is the primary source.
The initial design did not include a pipeline for adding alkali; during the subsequent technical upgrades, we prepared a supply of sodium hydroxide on our own, but we didn’t add too much of it. What is the appropriate pH level to maintain?
How to prevent it? Can adding alkali prevent it? Or just pure prevention at the source?
If it is due to calcium ions, adding alkali can only exacerbate the scaling caused by those calcium ions. The source of the three calcium ions mentioned above depends mainly on which factor is at play; for example, if it is due to desalinated water, then it is necessary to check whether there is a problem with the quality of that desalinated water. If it is the washing water for the ‘ammonia tower’, it also falls under the category of desalinated water; if it is due to the feed gas, then the issue lies with gasification.
Our factory also suffers from scaling all year round; when it’s removed, it looks like cement. We’ve tried many methods, but none worked. Adding sodium hydroxide caused severe crystallization in the heat exchangers of the regeneration tower, so we stopped using it. We clean them once a year on average
Regular use of acid cleaning can easily remove the dirt on it, such as the commonly used mixed acid for descaling. Actually, acetic acid also works very well, and it does not cause corrosion to the equipment.