Methanol distillation reboiler
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1 For methanol distillation, the steam inlet diameters of the reboiler in Tower 1 and Tower 2 are 300 and 350 respectively； The exports are 150, 125. The reason is that when steam condenses into water, its volume decreases. But why is the diameter of the outlet pipe at the second tower smaller than that at the first tower? Also, what is the volume of water formed when a certain amount of steam condenses? At atmospheric pressure, thank you. The diameter of the reboilers in the three-tower system is larger than that of those in the two-tower system. The reason for using two reboilers is that the heat required by the reboilers in the three-tower system corresponds to the amount of methanol that needs to be evaporated; this amount is usually around 100 cubic meters of methanol vapor per unit time. Meanwhile, the amount of steam required in the two-tower system is 26 tons (at 1.3 MP pressure), which is why two reboilers are used there. So, how many times greater is the heat released when one volume of water condenses into liquid water compared to that of an equal volume of methanol?
The pressure tower has pressure, while the pre-tower does not; therefore, the diameter of the outlet pipe doesn’t need to be that large, right?
1. Regarding the pipe diameter issue, I can’t answer it; it’s likely a design error. Please ask other experienced sailors for help. To convert the volume of water vapor into the volume of water, one can first convert the water vapor to its volume at standard conditions, divide that value by 22.4, and then multiply by 18 to get the mass; from this mass, the volume of water can be determined. 2. The distillation tower is designed with two reboilers; there are discussions on forums, please search for them. Regarding the heat release of methanol vapor, I think I just need to look up the condensation heat of methanol and water. It’s just my personal opinion; I’d appreciate everyone’s feedback.
I don’t think there’s any fixed requirement regarding the size of the outlet; what’s important is that it can handle the discharge of the steam-water mixture after vapor condensation
For the density of steam, you can refer to the steam manual; the density of 8 kilograms of steam is 7 kilograms per cubic meter.
First, it is necessary to determine whether it is three-column or two-column distillation; secondly, what type of reboiler is used and what is the medium inside it?
In the three-column distillation process with a reboiler of the shell-and-tube type, the shell side is filled with steam. That’s why two three-tower reboilers are used; it’s because the methanol vapor volume in the two-tower system is high, and the diameter of the three-tower system is 3 meters larger.
The issue with the outlet diameter is probably due to the fact that the pre-tower generates less steam and less condensate, while the second tower produces more steam and more condensate. The condensates from both towers eventually converge in the same main condensate pipe. To prevent the relatively large amount of condensate from the second tower from interfering with the condensate discharge from the pre-tower and causing problems in that discharge, the outlet diameter of the second tower is made smaller than that of the pre-tower.
As for the reboiler, I think it’s because the third tower produces a large amount of methanol, which requires a lot of heat; therefore, a sufficiently large heat exchange area is needed. If there is only one reboiler, the equipment will have to be very large, increasing costs related to manufacturing, transportation, and operation, as well as posing greater risks during actual operation. These factors are all taken into consideration during process design, though it’s not necessarily the only possible solution.
The reason why the reboiler in the third tower has a larger diameter than those in the second tower is that the heat source for the second tower is low-pressure saturated steam, whose heat value is much higher than that of the methanol steam used as the heat source in the third tower. As a result, a relatively smaller heat exchange area is required, and hence the diameter of the reboiler is smaller.
This is just for reference
As for the reboiler, I think it’s because the third tower produces a large amount of methanol, which requires a lot of heat; therefore, a sufficiently large heat exchange area is needed. If there is only one reboiler, the equipment will have to be very large, increasing costs related to manufacturing, transportation, and operation, as well as posing greater risks during actual operation. These factors are all taken into consideration during process design, though it’s not necessarily the only possible solution.
The reason why the reboiler in the third tower has a larger diameter than those in the second tower is that the heat source for the second tower is low-pressure saturated steam, whose heat value is much higher than that of the methanol steam used as the heat source in the third tower. As a result, a relatively smaller heat exchange area is required, and hence the diameter of the reboiler is smaller.
This is just for reference
I’m not sure about the first question; I don’t quite understand the explanation given on floor 8. For the second question, I agree with what was said on floor 8
The three towers are heated using methanol vapor from the outlets of the two towers. The temperature of the methanol vapor is much lower than that of ordinary steam; naturally, the heat exchange area required is larger. As for the diameter of the outlet pipes, it’s best to ask the designers
One ton of steam can vaporize about two tons of methanol. As for the pipe diameter, you need to check the design drawings again; it should be correct
The steam pressure is the same in all cases!!