Control of diesel at 95 points
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Our factory sets a standard of 95 points for diesel, but in practice, we still encounter situations where the temperature returning to the tower and the distillation temperature of the diesel are the same; yet the resulting value for 95 points varies significantly. I would like to know what could be the reasons for this Which temperature parameters are used as the basis for adjustment in the specific tuning?
Is it related to the properties of the raw materials? It’s necessary to accumulate more experience
It shouldn’t be due to the properties of the raw material; we have been refining this type of oil all along
While ensuring that what you said remains unchanged, factors such as changes in the properties of the crude oil, the degree of reaction, the processing volume, the pressure at the top of the distillation tower, and the temperature at which the slurry is returned to the tower can all affect the 95% cut point of diesel. Attention should also be paid to the amount of stripping steam and the pressure. For reference, it is advisable to use the extraction temperature mentioned in Reference 1 as well as the vapor phase temperature on the chevron baffle, ensuring that there are minimal fluctuations in the bottom temperature of the tower and the top pressure
Let me add one more point: our reaction unit has been frequently adjusting the feed rate of crude oil lately. Could this have an impact?
It’s a problem – how do you control the temperature at which diesel is extracted? So where to start. Is the temperature the same, and is the flow rate the same? Raw material properties, instrument factors, changes in the tower environment, and so on
This will definitely have an impact! The amount of re-refined oil also has an impact
Although the properties of the raw materials remain unchanged, changes in the feed rate at the reaction unit also affect the degree of reaction; changes in the reaction temperature and the catalyst circulation rate likewise influence the composition of the reaction gases and liquids. As a result, when all other conditions remain unchanged, the column pressure of the distillation tower also changes; although the distillation temperature stays the same, the quality of the product changes. Therefore, specific issues need to be analyzed on a case-by-case basis, with adjustments made according to the actual conditions at the site.
Changes in the processing volume affect the degree of reaction, as well as the partial pressures of the fractions in the oil and gas stream and the temperatures within the tower. Especially when there are large or frequent changes in the processing volume, the variations in parameters such as atomization, pre-raising, mixing, and stripping often cannot keep up, and adjustments to the flow rates in various circuits are not made in a timely manner. It will cause changes in product quality.
A 95% point variation in diesel is normal; it’s fine as long as it remains within a reasonable range. There are many influencing factors, among which the effect of the reaction is fundamental: feed rate, properties of the raw materials, degree of reaction, whether there is reprocessing of oil, reprocessing of slurry oil, and so on. Changes in the various refluxes of the distillation column also have an impact on this point. Because these adjustments directly affect the heat and mass transfer between gas and liquid within the entire distillation column, they cause changes in the amount of diesel produced, and as a result, the boiling range also changes.