Why is the temperature at the top of the methanol-water separation column in low-temperature methanol washing higher than the temperature in the upper middle part of the column?
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During operation of the methanol-water separation tower, it is common for the temperature at the top of the tower to be higher than that in the upper middle part of the tower (above the sensitive plate). Could someone please explain the reasons for this and suggest ways to address it? Also, how to maintain stable liquid levels when the tower is first started up, how to control the amount of steam used, and how to bring each temperature level as close as possible to the target values? Due to a lack of experience, this tower seems quite difficult to operate. Please discuss among yourselves, share your experiences, and tell us your methods of operation so that we can use them as a reference! ! Note: Dalian University of Technology’s process package! (With exhaust gas scrubber)
Inverted temperature in the methanol water column: Check whether the temperature of the recycled pure methanol at the top of the column is too high! The water content in the methanol containing water that comes from the water concentration section at the bottom of the thermal regeneration tower; if this water content is too high, it may lead to high temperatures! How to control steam usage: Gradually increase the amount of steam at a normal rate of heating up, but not too quickly! How to maintain stable liquid level: Put the exhaust gas scrubber into use as soon as possible, so that the washing water from the scrubber can be continuously supplied to the methanol water tower; this helps to keep the liquid level in the water tower stable!
I wonder what the production load of your company is? The amount of steam is adjusted based on the amount of methanol entering the methanol-water separation tower and the amount of reflux liquid at the top of the tower, with the goal of maintaining the temperature of the tower. Generally, the temperature at the bottom of the tower is controlled around 137 degrees, around 98 degrees at the top of the tower, and 104–140 degrees for the sensitive plate. The amount of steam is determined by temperature. If it is difficult to control, conduct an analysis to check whether the CO2 content in the methanol feed water is too high.
It mainly comes down to where the feed inlet is located. If the feed inlet is in the middle, then yes, you end up raising the temperature too quickly, so the feed inlet isn’t able to raise the temperature, while the temperature at the top of the tower already increases.
It’s most likely that there is an issue with the backflow at the top of your tower. Failure to supply in a timely manner, or there is an issue with the location of the feed inlet. Also, check if there are any issues with the installation location of the reboiler. We’re from Dalian University of Technology as well; similar problems have occurred in the past due to the reboiler being installed at too high a position. It’s also possible that there’s a problem with your thermometer, so have it calibrated. . . . Our methanol-water separation tower is operating fairly well. . .
The high temperature at the top of your tower is likely caused by an excessive water content in the methanol-rich stream coming from the concentration section. In such cases, you can increase the reflux rate and maintain an appropriate reflux ratio. During the initial startup phase, if the liquid level fluctuates significantly, you should switch from automatic to manual control in order to make fine adjustments slowly. Once the liquid level approaches normal values and there are no more significant fluctuations, you can switch back to automatic control. That's how we do it. Relatively stable. The control of the steam volume is based on the temperature of the tower; by taking three temperature measurement points at the upper and middle parts of the tower as well as on the reboiler, and comparing these values to ensure balance, the appropriate steam volume can be determined. It also alternates between manual and automatic modes, and it’s essential to maintain stability to avoid large fluctuations.
It’s caused by flooding; there are excellent suggestions regarding the methanol distillation section – you should take a look
I think it’s because too little water was added. If the liquid level of water at the bottom of the tower is unstable, it’s not possible to ensure an adequate supply of steam, which leads to such phenomena. This issue can also occur in distillation towers, and the main reason for it is again too little water being added
Is the temperature of the recycled methanol coming from the hydrogen sulfide concentration tower high?
Temperature inversion in the methanol-water separation tower: Check whether the circulation volume of pure methanol in the reflux at the top of the tower is too low, resulting in an excessive amount of water at the top and thus a high temperature there； Also, check whether the circulation volume from the exhaust gas scrubber is too high, which results in an insufficient amount of steam being supplied and thus causes a rapid drop in the temperature inside the tower. How to control steam usage: Gradually increase the amount of steam at a normal heating rate, making adjustments slowly; once the temperature stabilizes, the steam control valve can be set to automatic control. How to maintain stable liquid levels: First, activate the exhaust gas scrubber, allowing the wash water from this scrubber to be continuously supplied to the methanol-water tower. At the same time, it is necessary to keep the outlet flow from the water separation tower stable, as this helps to maintain a stable liquid level in that tower as well!
In class, I learned something new again! Thank you, masters!