What could be the possible reasons for significant fluctuations in the night level at the bottom of an atmospheric pressure tower?
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As the title suggests, fluctuations in the bottom liquid level of the atmospheric pressure tower – could this be a precursor to a tower surge? What other reasons could lead to such situations? What is the impact on the third-line mass? What about the others?
Changes in the feed rate, as well as whether the raw material contains water, can all cause fluctuations in the liquid level.
In addition to fluctuations in the feed rate, common issues include fluctuations in steam pressure and abnormalities in the extraction of liquid from the reactor. If the temperatures at the three points remain stable, it has little impact on the quality at those points; however, when there are significant fluctuations in liquid level, the temperatures will also change accordingly, so such fluctuations are likely to affect the quality.
Is the furnace temperature and feed stable? Check some?
The feed rate and the properties of the raw materials, as well as whether water is present, can all affect the bottom liquid level of the tower
Fluctuations in the liquid level at the bottom of the atmospheric pressure tower do not necessarily lead to a tower surge, but if not managed properly, a drop in liquid level and a sharp rise in temperature can result in a tower surge. Reasons for liquid level fluctuations: changes in processing capacity, changes in the properties of the feedstock, water carried in the feedstock or steam, fluctuations in steam pressure or temperature, changes in the temperature of the atmospheric pressure furnace, pump or instrument failures, as well as changes in the reflux volume and temperature at various sections of the atmospheric pressure tower, and so on. Fluctuations in liquid level will inevitably cause fluctuations in the temperature at the bottom of the tower, and the yield from the third line will also fluctuate as a result, which has more or less an impact on the quality of the product from that line.
Increased feed temperature, heavier raw materials, higher bottom blowing volume, reduced reflux in the lower section of the tower
High outlet temperature of the regular furnace, changes in the properties of the raw materials, high temperature at the side streams, reduced reflux in the middle and lower sections, and high steam injection volume at the tower bottom
Possible reasons for significant fluctuations in the night level at the bottom of the atmospheric tower include: 1. Water in the feedstock (this is less likely if there is a distillation column), as the probability of water being present in the overhead oil is very low; moreover, the overhead oil pump would empty out first. 2. The steam used for bottom blowing contains water (blowing temperature control > 300°C). 3. Improper setting of the PID parameters (proportional, integral, derivative) in the control system leads to unstable control. 4. The level gauge indication drifts. Other influences such as changes in feed quantity, furnace temperature, and raw material properties are temporary, and do not result in significant fluctuations over extended periods of time. A high liquid level may cause tower flooding; whether flooding occurs depends on whether the temperature gradient in the atmospheric pressure tower is normal. If the temperatures of the various side lines do not change much, there will be no tower flooding. Column 3 generally produces heavy diesel; if the liquid level at the bottom of the column is high, it will cause the 95% distillation temperature to increase. If the temperature difference between Column 3 and Column 4 (or the feed temperature) is no more than 10°C, it can be considered that there is a problem with the column operation. The sample taken from Column 3 should be black in color.