The impact of tray corrosion on operation
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This post was last edited by dongliangsir on 2018-1-14 09:32. In the atmospheric distillation column of the vacuum distillation unit, the trays at the top stop functioning; several trays are stuck halfway and do not drop down. Severe corrosion occurs, and what impact does this have on product quality? The main effects concern the dry point of the atmospheric distillate and its flash point. What impact does it have on operations? What is the main type of corrosion at the top of the tower?
Given this situation, the rising gas does not come into effective contact, which leads to the emergence of higher-component substances, and the dry point may increase. I don’t think the flash point will be affected much, as the light components can always rise to the surface; it might increase a bit, but not by much. The impact of this operation is an increased load at the tower top, with all the heavy components rising to the top. Corrosion generally includes chloride ion corrosion and H2S corrosion; usually, the corrosion at the top of the tower is the most severe, as the corrosive gases are present there.
Thank you. Could this situation cause flooding? In this case, can the heavier components rise, but not descend? Will it be higher if I work? Personally, I think the increase in the recombination fraction should be less than normal, as the floating valve does not operate
It depends on the condition of your floating valve. In terms of this current image, a large number of floating valves have fallen off, and the proportion of those that have failed to function is higher; this means that the heavier components in the gas cannot be removed. If you replace all the floating valves that are missing in the diagram, after installation 80% of these valves will function properly while 20% will not. As long as the processing capacity remains within the range corresponding to 80% of the valves’ capacity, the impact should be minimal (unless the non-functional valves are located in the same area). However, if the processing capacity still operates at the upper limit specified in the original design, then the 20% of valves that do not function will result in a significant decrease in the efficiency of gas-liquid heat transfer; in such a case, the operation of the tower will be disrupted, and it will depend on the actual circumstances.
It severely affects mass and heat transfer; the pressure at the top of the tower is not accurate, heavy components are carried away, and the separation efficiency is poor. This tray is unusable, and it is necessary to check the condition of the trays below it, as this affects the quality of the product or intermediate products.
Personally, I think there will be severe leakage. Although not much, some gases with heavy components will still make it up to the top; these heavy components cannot come into good contact with the liquid phase at the tower top, resulting in poor separation, and therefore the dry point at the top is often high. Sometimes, there are some constant topping components, which result in a lower flash point. At the same time, the pressure drop at the top of the tower is very high. Please correct me
During operation at that time, the pressure fluctuated regularly up and down; I’m not sure what caused it.
That makes a lot of sense; thank you very much