The sulfur content in the naphtha from the diesel hydrocracking fractionator is higher than that in the resulting diesel
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The oil from the bottom of the stripping tower in our facility is heated in a furnace before being fed into the distillation tower, where naphtha and diesel products are separated through steam stripping. The sulfur content of the diesel product exiting the facility has always been below 7 ppm. However, recent analyses of the sulfur content in naphtha have shown that it can reach up to 30 ppm; after washing with an alkaline solution, this value drops to 10 ppm, which is still much higher than the sulfur content in the diesel product. The stripping steam of the stripper was also brought up. How should this be analyzed – the reason why the sulfur content in naphtha is higher than that in bottom diesel?
However, the sulfur content in the diesel meets the requirements; it has been running with a new catalyst for three years now, so there should be no issues with the catalyst. Sulfur in naphtha should be easier to remove than sulfur in diesel, right?
This post was last edited by qugd on 2022-3-16 at 10:52. 1. Factors related to sampling and analysis: sample contamination, contamination of the sampling containers, and errors in the operations during analysis. 2. Processing condition factors: 1) Inadequate stripping, 2) Poor separation of oil from water, 3) Decline in catalyst activity due to failure to adjust process parameters in a timely manner. However, based on the analysis results, the value of the sample after alkaline washing is close to 10, indicating that the decline in catalyst activity is not significant; appropriate optimization of the process conditions may lead to improvements. Additionally, enhance stripping and ensure effective oil-water separation.
Hydrogen sulfide did not emerge from the naphtha; the first approach is to reduce the pressure in the tower top reflux drum, and the second is to try increasing the feed temperature. What can be removed by alkaline treatment is usually hydrogen sulfide. If the sulfur content in the diesel is not a problem, it indicates that the reaction temperature is sufficient; it’s likely that the sulfur content in the raw materials has increased. It is recommended to compare this with the sulfur content of the raw materials during the same period.
The stripping flow meter can be calibrated, the top temperature of the tower can be increased appropriately, and the top pressure can be reduced
Analyze whether it is inorganic sulfur or organic sulfur