Issues regarding the design of the bottom reboiler
Thread Content
One reboiler at the bottom of the tower; the design in the process package calls for the temperature at the tower bottom to be raised from 170 degrees to 178 degrees, using 23 kilograms of steam. In practice, the temperature at the bottom outlet of the tower is between 145 and 150 degrees. At this time, the opening degree of the condensate control valve is between 5-7%. May I ask, if the steam amount is increased to 10 kilograms, can the material be heated to 145–150 degrees? Also, what negative consequences can arise from the control valve having such a low opening degree?
In actual production, the saturation temperature of 10 Kg of steam is around 180–190 degrees; therefore, there should be no problem in heating it to the temperature you mentioned. Why not adjust the temperature of the reboiler by controlling the amount of steam used?
10KG of steam is more than sufficient to reach the heating temperature required by the poster
It is completely possible to achieve the desired effect; our unit uses 10 kilograms of steam, and the temperature can be controlled by adjusting the steam valve. The separation effect is good, but I’m not sure whether it’s separation at the bottom of the tower or at the top of the tower. It is best to preheat or cool the feed.
There should be no problem, but under different circumstances the internal design of the reboiler varies slightly, so it cannot be generalized. It is rare to hear of condensate control valves being used to regulate the reboiler.
I heard for the first time that temperature can be controlled using condensate water – is it really possible to do that? It is better to control it using the steam flow rate.
What I’m saying is that a control valve should be installed at the outlet of the steam reboiler for control; many of our systems are controlled in this way. Also, as the steam pressure and temperature decrease, the heat transfer coefficient of the heat exchanger should decrease as well, which then relates to the issue of the heat exchanger’s area.
The temperature difference under the new operating conditions has indeed decreased, but it hardly affects the heat transfer coefficient. As long as there is a sufficient margin in the design area, it should be fine. Does the control valve at the reboiler outlet regulate the condensate level to keep it constant?
The condensate control valve is used to regulate the reboiler level, which in turn controls the heat exchange area, thereby achieving control over the reboiling process
After reading LS’s explanation, it’s indeed learning something new. Such control either involves a very wide range of heat transfer amounts that can be regulated; for example, in batch distillation, there are periods when no large amount of heat transfer is required ； Or it’s designed to be too large. In that case, is it necessary to add a level indicator for the condensate water as well? This post was last edited by clfclfclf on 2008-12-1 22:03]
We also use condensate control design; it hasn’t been put into use yet, so we don’t know how it will work. Those who have used these two types of TXs, please share your experiences