Corrosion issues in the alkylation deisobutane system
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In my company’s alkylation unit, the pH value of the reaction products is neutral after washing, but corrosion occurs at the top of the isobutane tower; the air-cooling tubes at the tower top are severely corroded. I would like to ask the experts what could be the cause. Personally, I think it is due to sulfates formed as a result of the reaction of butadiene in the raw materials, which are carried into the tower and then decompose to produce sulfur dioxide
This situation is quite common; it occurs when organic acidic substances enter the backside area, causing corrosion of the tower. Generally, corrosion becomes severe after the installation has been in operation for one and a half years. It is recommended to install a coalescer before the isobutane removal tower to reduce corrosion in the subsequent sections.
You’re right; this kind of substance cannot be removed by alkaline cleaning, and coagulators may not work either, as it is neutral. But in the subsequent systems, it causes severe damage as soon as high temperatures are present – it corrodes the top of the tower at the upper end and the bottom of the tower at the lower end. Therefore, it is necessary to control production capacity and avoid overloading the reactor; otherwise, it will cause you trouble and result in heavy costs.
Increase the alkali washing temperature? It seems that pickling doesn’t have much effect either
Are there companies that use pickling, alkali washing, and water washing along with the addition of fillers, and what is the effect of this?
Is it caused by the thermal decomposition of sulfatides to produce weak acids, or is it a reaction issue? The products contain sulfatides, and if they are not thoroughly removed during acid cleaning, it leads to problems later on.
This form of existence is not sulfur in ionic state, so it is difficult to remove. Strengthening process control during the reaction phase is quite effective
Didn’t you consider adding hydrogen pretreatment to your raw materials?
The standard process involves pickling, alkali washing, and water washing; for neutral surfactants, pickling in the first step is essential. If possible, adding an acid coalescer beforehand can also have some effect.