(17b) Biorenewable Diesel and Jet Fuel Production

Conversion of natural plant and animal-derived oils to hydrocarbon fuels has been established using hydroprocessing technologies to produce renewable jet and diesel products by hydrotreating and then isomerizing/cracking the natural plant and animal-derived oils via a two-stage process.  Investigation of a range of conversion and cracking/isomerization levels has shown that an alternative design could provide better economics than just running at maximum jet yield.  This mode of operation also leads to an initial capital investment similar to the maximum diesel yield mode while allowing the refiner to produce a significant amount of jet fuel by operating at higher conversion levels with a modified fractionation scheme.  The positive relationship between conversion and isomerization requires optimization of fractionation to meet all critical jet fuel specifications, especially freeze point, at different levels of conversion.  However, operation at increased conversion risks cracking some of the high-value distillate range material into low-value naphtha range.  Additionally, the cold flow properties of the diesel product are impacted by fractionating out a jet product.  Therefore, maximizing product yields according to market demand while meeting all required product specifications requires careful management of cracking and fractionation.