The 95% issue with catalytic cracking diesel
Thread Content
As the reaction depth in the catalytic cracking unit increases while the temperature at which diesel is extracted remains unchanged, what will happen to the temperature at the 95% cut of the diesel distillate? Raise it or lower it? Why?
Diesel specifications are related to the operating conditions of the distillation system, and have little to do with the degree of reaction.
The yield of each product is determined by the reaction, while the yield and quality of each product are determined by the distillation and stabilization systems.
It will be a bit lower, but not by much. The change in the dry point of diesel mainly depends on the distillation process, but an increase in the degree of reaction primarily leads to a higher degree of cracking of diesel, thereby increasing the yields of gasoline, liquefied gas, and other products.
If the fractionation tower is operating properly, the reaction depth may not affect the 95% point of diesel
The draw-off temperature at the side stream of the fractionation tower is the bubble point temperature of that side stream product under its vapor pressure. As the reaction depth in the catalytic cracking unit increases, the diesel yield decreases; in other words, the vapor pressure at that side stream decreases due to the drop in yield. If the draw-off temperature for diesel remains unchanged, the temperature at the 95% cut of the diesel fraction will increase.
An increase in reaction depth and gas production leads to an increase in the vapor pressure of the oil and gas at the top of the fractionation tower; with the diesel extraction temperature remaining unchanged, its 95% cut point decreases slightly.
Agree with the view on floor 5; there should be a slight decline, but the impact is minimal.
I don’t think it will change; on the one hand, from the perspective of product quality, the dryness of diesel should be related to distillation and has little to do with the degree of reaction； As for the 7th floor, a good point was raised. It is true that the extraction temperature corresponds to the bubble point temperature of that material under its oil-gas partial pressure; therefore, the reduction in diesel components seems to lower their bubble point temperature, which leads to an excessive extraction of these components when the extraction temperature remains unchanged, resulting in an increase in the dry point. However, as the amount of light components increases, the system pressure may actually rise slightly, compensating for the loss in partial pressure caused by the reduction in diesel components, so the overall result should remain more or less the same. In other words, there shouldn’t be much change in the output.
Agree with the analysis on floor 8. But I think in production operations, no one would change the reaction depth just to control diesel quality. Moreover, this impact should be minimal.
I agree with the view from floor 7: the 95 value increases slightly. The greater the degree of reaction, the more significant the cracking occurs, resulting in an increase in the amount of light components (as carbon chains break apart). This leads to an increase in gas production, while the relative amount of heavier components increases as well; hence, the 95 value rises slightly.
As the reaction depth increases, diesel production rises. The extraction temperature remains unchanged, and the temperature at the 95% point also does not change much
The reaction depth has an impact on the product distribution; increasing the reaction depth raises the yield of light oil. As the reaction temperature rises, if the distillation system is not operated, the temperature of the entire system increases, as do the temperatures of various reflux streams. The temperature at which diesel is extracted also rises. If the temperature is kept constant, it is equivalent to shifting the extraction point slightly upward, resulting in a lower dry point. I’m not sure if my analysis is sound; please give me your advice
It should be increased! The heavy components in the diesel fraction oil increase, so the 95% value increases accordingly!
As the reaction depth increases, the most direct effect is a decrease in diesel yield. Among the components of diesel, it is the long-chain molecules that are most prone to breaking apart; as a result, the proportion of relatively light components in diesel increases, and the 95% concentration will definitely decrease. The disagreement among everyone lies in the extent of this reaction: whether it is the light components in diesel that crack first, or the heavier components. According to the catalytic positive carbocation theory, carbon chains with longer lengths are more prone to cleavage than those with shorter lengths. . Therefore, the reformed fraction in diesel decreases relatively. . :Lol, just my personal opinion. . . .
Reaction depth controls the physicochemical properties of diesel, such as density and group composition, and does not affect the dry point
Agree with the view from floor 7. As the reaction depth increases, diesel production decreases and the partial pressure of diesel vapor falls; without adjusting the diesel extraction temperature, the 95% cut of diesel increases.