Analysis of fractional distillation phenomenon
Thread Content
Is the large amount of water carried in the top circulation due to an excessively low temperature in the tower? What about the heat exchanger? Internal leaks can be ruled out
Is there a problem with the oil-water separation in the tower top condenser?
Yes, it’s because the temperature returning to the tower is too low; simultaneously, the temperature control at the top of the tower is also too low, resulting in water being condensed due to pressure, even with a relatively high pressure at the outlet of the top circulation pump, around 110. . . :lol
This explanation is too far-fetched; the condensation temperature at the top of the tower is only in the low tens of degrees.
Is it because too much steam is injected into the tower, resulting in high partial pressures and thus condensation? What should be the normal control levels for the tower top temperature and the temperature of the liquid returning to the tower?
Diesel sometimes contains water; it is suspected to have leaked from the oil collection tank at the top
A large amount of gas is introduced into the distillation tower, or a large quantity of reaction steam enters it. Due to the low temperature of the overhead reflux stream in the distillation tower, some of the steam in the rising airflow cools down rapidly upon contact with this cold reflux fluid and exists in liquid form. Since the saturated vapor pressure of water vapor at this point is lower than the vapor pressure at the top of the distillation tower, some water is generated. Then some of the water flows downward, absorbs heat and vaporizes, which again causes the temperature to drop, leading to some of the steam condensing.
If diesel contains water, first check whether the steam volume in the stripping tower is too high~~~~~~~~
The answer on the 3rd floor is correct. The reasons for water presence in the distillation tower are, first, steam injection during the reaction process, and second, steam injection during distillation. Regarding your plant’s situation: 1. Reduce the amount of steam injected during both the reaction and distillation processes appropriately. 2. Increase the return temperature to the tower in the top circulation. 3. Increase the top temperature of the distillation column. 4. Appropriately reduce the pressure.
An excessively low temperature of the reflux stream to the tower can lead to water being carried along with it, as at the pressure at the top of the tower, water begins to form when the temperature is below 105 degrees. Generally, the reflux temperature should be kept at least at 95 degrees to prevent excessive amounts of water from being carried along. Additionally, a high water level in the oil-gas separator can also result in water being carried along; usually, even if a large amount of steam is injected during the reaction, as long as the reflux temperature is maintained properly, the water vapor can be carried to the oil-gas line at the top of the tower and then discharged through the separator.
If diesel contains water, first check whether the steam volume in the stripping tower is too high – this can be ruled out. The top temperature of the stripping tower and the temperature of the material returning to the tower can also be adjusted; if the dry point of the gasoline becomes too high, it will no longer meet the requirements
It is very likely that the temperature in the top recycle tower is too low; someone did this before to meet yield requirements. Other than that, it might be caused by excessive reaction gas injection. This post was last edited by wsts00100 on 2009-2-12 19:02.]
The opinion on the 3rd floor is correct. Please take a look at the relationship between water vapor pressure and temperature, and you’ll understand. . . Both the dew point and the bubble point are associated with a certain temperature and pressure. . . :lol
Hehe, I don’t blame the person in floor 4; they might not have considered the relationship between the phase of water and temperature and pressure. At normal pressure (1 atmosphere, 100 degrees Celsius), this is the boiling point of water – the point at which water starts to boil. At this stage, water exists in a mixed gas-liquid state, with both gas and liquid phases present. . . 1. If the pressure is higher than its boiling point pressure and the temperature is around its boiling point, then a liquid phase of water begins to appear. 2. Generally, the outlet pressure of a top circulation pump is much higher than one atmosphere, and if the temperature of the reflux returning to the tower is around 110 degrees Celsius or lower at that time. . . Hahaha. . . So water is a liquid state. . . :lol Last edited by wangsc on 2009-2-13 08:58 ]
It’s the water vapor pressure, right? If the tower pressure is high, the water vapor pressure isn’t necessarily high. The steam injection volume may increase, altering the water vapor pressure; even if the temperature remains unchanged, water can still liquefy.
It refers to the water in the top recirculation flow zone. . . . :lol
It’s not the low temperature in the top reflux tower; rather, it’s the excessively low temperature at the top of the distillation tower – a temperature that is below the dew point corresponding to the vapor pressure at the tower top. As a result, the vapor condenses inside the tower and cannot escape. This problem was already solved seven or eight years ago by simply carrying out dehydration in the top reflux tower.