How does an increase in the amount of catalytic slurry flowing back to the tower, resulting in a rise in the temperature at the bottom of the distillation tower, affect the properties of the slurry?
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An increase in the amount of catalytic slurry flowing back to the tower raises the temperature at the bottom of the distillation tower. What effects does this have on the properties of the slurry, such as its density, solid content, boiling range, and the yields at 350/500 degrees?
An increase in bottom temperature leads to an increase in density; the solid content should have little impact, as long as the bottom temperature is not extremely high, the density will rise
Let’s discuss two points briefly. First, it is normal for an increase in the amount of slurry returning to the tower to lead to a rise in the temperature of the distillation tower. As long as the temperature is not too high and does not cause coking of the slurry, its density may decrease slightly. Since more light components are washed back up to the tower, the rising temperature will cause these light components to evaporate as well; thus, there is a balance at play here. The effect on the solid content also has a similar relationship to the density mentioned above, I guess. As long as it does not cause coking, the density should decrease slightly. I’ll leave the rest to those more experienced for guidance.
Increasing the upward tower flow will reduce the downward tower flow, thus raising the temperature. But as long as it does not exceed the design specifications, there are generally no problems. If it exceeds the limit, severe coking may occur. Due to the increased amount of material returning to the tower, more light components are washed out, so the density of the slurry should decrease; at the same time, the amount of slurry discharged will increase.
The main function of the catalyst-rich slurry flowing back up the catalytic fractionation tower is to wash the oil and gas of catalyst, while the function of the slurry flowing back down the tower is to regulate the bottom temperature of the tower. When the amount of slurry recycled is constant, increasing the amount of slurry sent back up the tower results in a decrease in the amount of slurry sent back down the tower. This leads to an increase in the temperature at the bottom of the distillation tower; the density should decrease, while the solid content should remain unchanged. The yields for 350/500 should decline.
The density of the slurry is closely related to the reaction temperature; higher reaction temperatures result in a greater density of the slurry. This is mainly due to the increase in heavy components such as resins, asphaltenes, and polycyclic aromatic hydrocarbons in the oil slurry. The function of the bottom circulation slurry in the fractionation tower is to wash the catalyst and remove excess heat.
The answer in the bolded part is a bit problematic. Following the logic of the original question: under unchanged other conditions, increasing the amount of circulating slurry that returns to the tower means that more catalyst is used for washing; as a result, the probability that catalyst in the oil-gas mixture gets washed into the slurry increases, so the solid content in the slurry should rise at this point. I won’t go into detail about changes in other related factors.
The solid content of the slurry should increase; that’s not possible, as it is related to the efficiency of the reaction centrifuge.
If the amount of slurry returning to the tower increases, the liquefaction at the bottom of the distillation tower should rise; based on this, the density of the slurry should decrease. I’m not sure if this analysis is correct – please share your insights
The rise in the liquid level at the bottom of the distillation tower has little effect on the solid content in the slurry, as the slurry is taken from the bottom of the tower; an increase in the amount of material returning to the tower will inevitably carry more catalyst along with the oil and gas to the bottom of the tower. To use an analogy: suppose there is a pile of flour that is rising, with no liquid flowing downward; at the bottom, there are basically no flour particles ； When water is sprayed from above, the amount of flour particles at the bottom increases gradually as the volume of water sprayed increases. (Theoretical state, excluding factors such as gravity, analyzing this issue solely from the perspective of the flow direction of the object.) ）
As the amount of slurry returning to the top increases and the temperature at the bottom of the tower rises, it is possible to reduce the amount of slurry sent back downward; otherwise, excessive temperatures can lead to coking. The solid content isn’t a major issue – it is mainly related to the reaction process and the amount of slurry that is discharged outside. The density will decrease due to an increase in light components.