What should I do if the temperature at the bottom of the tower doesn’t rise during PRO simulation?
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Could someone with experience give some advice? Thank you!
That senior has relevant literature; thank you.
In Aspen, the temperature at the bottom of the tower doesn’t rise. If it’s not a problem with the unit settings, then it’s likely that there isn’t enough heat from the tower reboiler, or perhaps the pressure settings are incorrect
During the simulation, the bottom temperature of the tower has little relation to the heat in the reboiler. The correctness of the thermodynamic approach is closely related to whether the bottom temperature of the tower is correct. In addition, the composition of the heavy components in the material, tower pressure, and pressure drop also affect the bottom temperature of the tower.
It might be due to the wrong composition of the tower bottom and operating pressure.
If the temperature at the bottom of the tower doesn’t rise, it’s not necessarily related to heat; it could be that the data regarding the components of the feed stream are insufficiently detailed, and this is particularly evident in oil simulation. Additionally, the pressure at the top of the tower directly affects the temperature at its bottom – try increasing the pressure at the top of the tower.
If the requirement for separation purity is fixed, then the factor of pressure should be taken into consideration. Starting from the top of the tower, followed by the tower pressure drop – these two factors determine the pressure at the bottom of the tower. But I’m not sure what the original poster means by “the pressure in the tower can’t be increased.” If the separation requirements can be met, why raise the pressure? Can’t it be at normal pressure?
It is related to the bottom temperature and composition of the tower; it has little to do with the heat load of the reboiler
The composition and pressure drop of the reboiler correspond to the temperature of the reboiler. The composition of the tower bottom is related to thermodynamic considerations.
It mainly has to do with the composition; when simulating a heavy aromatic tower, the simulated temperature is 160 degrees, while the actual temperature is around 220 degrees, showing a significant difference. In the end, the isomer with the highest boiling point and the same number of molecules was chosen, resulting in a temperature of around 200 degrees. Furthermore, due to errors in experimental analysis, trace amounts of recombined components may not be detectable; therefore, I added a small amount of additional substance (within the allowable range), raising the temperature to over 220, which is not much different from the actual value. Practical experience is for reference only!
The pressure drop should be taken into account in vacuum towers; it has a significant impact on the temperature of the tank within such towers. Of course, the composition, as mentioned above, is also quite important.
If the separation in the column is not thorough, the temperature cannot rise. I conducted a simulation of methanol distillation; the temperature at the bottom of the column was required to be above 105°C, but my temperature stayed at 90°C. Upon analyzing the reasons, the report showed that the methanol content at the bottom of the tower was above the specified limit; after making adjustments, the methanol content was reduced to less than 100PPM, and the temperature at the bottom of the tower rose to 106°C.