The Usual Suspects in Renewable Jet Fuels
by KSL (Lee Enterprises/Renewable Energy World) As renewables are moving from niche to mainstream, the industry is facing a paradigm shift in cost, quality, complexity, and scale — creating opportunities to develop new and different technologies and operating models. Achieving the next phase of the industry potential will require a further revolution, not only in the laboratory but also in strategy, technology, and operations. Some of these organizations preferred to generate transportation fuel from non-fossil resources with a pivot towards more tangible chemicals. With a further pivot now the direction is towards renewable jet fuels.
The idea here is to prioritize for biofuel applications in industries — which do not have feasible alternatives to liquid fuels, such as aviation and shipping.
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Its composition depends on the raw crude oil, but the composition is typically around 20 percent paraffins, 40 percent isoparaffins, 20 percent naphthenes and 20 percent aromatics. Each component has a specific role towards critical fuel requirements. For example, the high hydrogen-to-carbon ratio of paraffins and isoparaffins enhance the heat density per unit mass of fuel; naphthenes help to reduce the freeze point, which is critical at high altitudes; while the aromatics contribute to material compatibility and prevent leaks in the seals of some aircraft models.
Jet fuel specifications are defined in the U.S. and Europe by two alternative standards: ASTM D1655 of the American Society for Testing and Materials (ASTM) and Def Stan 91-91 of the UK Ministry of Defense. Other commonly used specifications are the Joint Check List (AFQRJOS) and GOST 10227 TS-1. These specifications are broadly equivalent and focus primarily on performance properties rather than chemical composition, due to the complexity and variability of the latter.
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As of today, there are essentially five conversion pathways that have the potential to produce a drop in alternative for fossil kerosene; Fischer-Tropsch (FT) process, Hydro-processed Esters and Fatty Acids (HEFA) process, Direct Sugar to Hydrocarbon Conversion (DSHC), Direct Liquefaction, and Alcohol-to-Jet (AtJ). (See Table.) Next to these, there are several other production pathways that yield liquid fuels, although it is uncertain to which extent these fuels can be used as drop in alternative to fossil jet fuel. These are:
- Fatty Acid Esters
- Furan derivatives
- Succinic acids derivatives
- Cryogenic fuels (LNG & liquid Hydrogen)
- CO2 remediation
Thus far, certification has only been granted to FT and HEFA processes with a recent push within the industry towards the AtJ — stemming from the ubiquitous ethanol to butanol to jet. READ MORE
author name removed 12/21/20