Why are there no jet fuel products in the side streams of secondary processing units such as diesel hydrogenation and coking?
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Why don’t secondary processing units such as diesel hydrogenation and coking produce jet fuel as a side product? The products drawn from the side streams of their distillation towers are naphtha and diesel – so why is there no jet fuel?
Currently, only two production processes are recognized in the country: one is the product obtained from the jet fuel stripping tower of atmospheric and vacuum distillation units, which is used for fighter jets； The other type is paraffin-based raw materials produced by cracking units, which are mainly used in civil aviation ； There is no consumption tax to pay on aviation fuel, amounting to over 1,400 ； So it earns more than 1,400 yuan per ton compared to diesel ； That’s all I know; fellow sailors, please add more if you have anything
Kerosene obtained through atmospheric and vacuum distillation cannot be shipped directly; it must first pass through a kerosene hydrogenation refining unit to remove sulfur and nitrogen, so as to meet the quality requirements. Since hydrocracking takes place in a hydrogen-rich environment, the product quality obtained from the side streams of its fractionation tower is generally sufficient to meet the requirements. But like other secondary processing units, the coking fractionation tower and the diesel hydrogenation fractionation tower can produce naphtha and diesel; then why can’t jet fuel, whose boiling point lies between those of them, be extracted via side streams? Logically, the severity of the diesel hydrogenation reaction is higher than that of jet fuel hydrogenation, with a greater degree of hydrogenation; so it should be possible, right?
Or does coking require bunker coal because there are too many olefins in it? If diesel hydrogenation side streams are used to produce Aviation fuel, isn’t there too much aromatic content in it? Even if it is extracted, it cannot meet the quality requirements for aviation fuel products; it’s pointless and not worth it, right?
Other secondary processing units, such as coking and diesel hydrogenation plants, have a high aromatic content in their kerosene fractions, resulting in freezing points that do not meet the requirements for aviation fuel
What is the aromatic content in the kerosene fraction resulting from diesel hydrogenation? How high is considered high? Against the backdrop of an excess supply of diesel, diesel hydrogenation units should find ways to produce more naphtha in order to reduce diesel production ； Alternatively, after adsorption separation of the refined diesel produced by the diesel hydrogenation unit, those with a BMCI of less than 15 can be used as raw material for ethylene production, while those with a high aromatic potential can be used as raw material for reforming; this way, the economic benefits of the diesel hydrogenation unit can be maximized.
The reason for not extracting aviation fuel may be that diesel hydrogenation results in a high content of aromatic compounds within the aviation fuel range, and such aromatic compounds cannot be removed even through extraction; moreover, deep hydrogenation to saturate and open these aromatic rings is too costly. Therefore, diesel hydrogenation makes the naphtha fraction heavier (compared to vacuum distillation) and the diesel fraction lighter (with a lower initial boiling point than straight-run diesel). The same principle applies to coking: in addition to having a high aromatic content, the fractions within the range suitable for aviation fuel also have a high olefin content; as a result, it is difficult to obtain fuel that meets national standards for aviation fuel, and processing such fuel is complicated and uneconomical.