Analyzing the influence of tower bottom liquid level on the distillation efficiency
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There are two views now. First, the liquid level is high and the residence time is long, resulting in good separation ； Secondly, the liquid level is low, resulting in a low reboiling and desorption load at the tower bottom, which facilitates good desorption. What do you all think of these two viewpoints – whether the liquid level is high or low, and whether desorption is effective? How can we assess the quality of desorption based on operational data, and determine whether over-desorption is occurring?
The level of the liquid has a very minor impact on the analysis efficiency; it is mainly the analysis temperature and pressure that have a significant influence. Controlling pressure and temperature is a prerequisite for ensuring good resolution, with corresponding adjustments made based on the load.
To raise the pressure at the top of the absorption tower from 1.2 to 1.4 MPa, what adjustments are needed in other aspects, such as the absorbent, and the steam flow rate to the reboiler at the bottom of the desorption tower?
High temperature and low pressure are favorable for resolution (to a certain extent; too much is not good), as excessively high temperatures and pressures are also undesirable
Is the tower pressure you analyze controlled separately? On the premise that the reaction load operating parameters remain unchanged, it is necessary to control the amount of dry gas, the amount of lean gas, and the amount of purge gas. The other parameters can be adjusted accordingly based on the gas volume.
Alas, it’s the only option available; there’s a leak in the reboiler used for heat exchange at the bottom of the desorption tower and in the light fuel distillation unit, and it’s not possible to repair it right now; repairs will be carried out next year
Yes, there is a pressure-controlled valve. I also want to ask if you have dealt with parsing before, and what kind of phenomena occur
First there is excessive absorption, followed by excessive separation; the main phenomena are an increase in the liquid level in the oil-gas separator at the compressor outlet and an increase in the amount of gas separated. Treatment reduces the absorption load.
The reboiler is leaking; cut off the feed severely! There’s no good solution
The level of the liquid has little effect on the analysis. A higher liquid level does not necessarily mean a longer residence time, nor does a lower liquid level imply a smaller heat load on the tower. Both of these approaches are wrong
With a high liquid level, the residence time is indeed relatively longer, as the circulation rate decreases! However, there is a limit to the degree of solution purification; given sufficient heating steam and with all other conditions unchanged, the solution will essentially be fully purified, and no matter how long you continue to operate it, it won’t make any difference! Similarly, when the liquid level is low, the relative load decreases, but the circulation rate increases; if this rate exceeds the resolution capacity under steam heating, insufficient resolution occurs, leading to a vicious cycle! Therefore, it is necessary to find an optimal operating point – that is, to determine what circulation rate is most suitable given a certain amount of heating steam. However, in practical use I have also made attempts, and it seems that the actual presentation takes a relatively long time!