As the properties of crude oil become lighter, how do the extraction temperature and volume from the side streams of the atmospheric distillation column change?
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As the title suggests: As the properties of crude oil become lighter, how do the extraction temperature and amount from the side streams of the atmospheric distillation column change? Please advise, experts
This post was last edited by lijianhuai on 2012-2-16 at 15:13. These are personal opinions for reference only: First, it is necessary to determine any changes in the properties of crude oil; if such changes cannot be identified, then it’s impossible to make any operational adjustments. If it is merely a matter of a reduced severity, as well as changes in the extraction temperature and amount from the side stream of the atmospheric pressure tower, this can be found in many books. The key is to be able to determine whether the property is becoming lighter or heavier, so as to make the necessary adjustments. I suggest that you definitely consult the experienced masters. They all know which parameters can be used to determine whether the properties of crude oil have become lighter or heavier after tank transfer. Moreover, it is necessary to pay closer attention to the trend chart.
This post was last edited by jbcyf on 2012-2-14 at 20:51. Theoretically, as the weight decreases, the pressure in the tower increases; if the pressure is automatically controlled, the amount of gas discharged from the reflux drum at the top of the tower will increase. If the draw rate of each side stream remains unchanged, the temperature will drop because the internal reflux flow will increase, causing the liquid level in the side stream stripping tower to rise. Therefore, after becoming lighter, the side-line extraction temperature can be appropriately increased to boost the extraction amount.
When the properties of crude oil become lighter, the temperature of the feed to the tower remains unchanged; then why does the extraction temperature for the third fraction of diesel increase (from 298 to 301)? To maintain a 95% quality standard, it becomes necessary to reduce the amount of diesel extracted – why is that? I’ve never been able to figure out this problem
When there is an excess of light components, the amount of vapor-phase components increases per unit time. An increase in the vapor phase volume raises the temperature at the side streams; meanwhile, an increased vapor load reduces the separation efficiency of the tower (this is especially evident near the feed inlet). Therefore, if the operating flexibility of the tower is limited, the situation you described will occur. If the tower has sufficient operating flexibility, this problem should not occur. Additionally, if there is not much diesel component among the increased light components, and only gasoline and light diesel components increase significantly, this can also lead to an increase in the dry point of heavy diesel.
As the properties of the crude oil become lighter, and if the other operating conditions in the atmospheric distillation column remain unchanged, the amount of light components increases. This causes the gas-liquid equilibrium in the entire column to shift upward. To maintain the original equilibrium, it is necessary to lower the bottom temperature and increase the reflux rate; however, if these adjustments are substantial, the amount of product extracted will decrease
As the properties of the crude oil become lighter, both the temperature at the inner line of the tower and the top temperature increase. The tower pressure also rises significantly at this point, as tower pressure has a major impact on the vaporization rate within the tower. Therefore, in order to maintain product quality, it is not possible to adjust the reflux rate drastically just by controlling the extraction temperature.
Under normal operating conditions, a lighter crude oil composition leads to a decrease in distillation temperatures and an increase in side stream yields.