Isoparaffinic Kerosene Research Articles

Fischer-Tropsch coal-to-liquid fuel negative temperature coefficient region (NTC) and low-temperature heat release (LTHR) in a constant volume combustion chamber (CVCC)

The purpose of the study was to investigate the correlation between thermal characteristics of neat Iso-Paraffinic Kerosene (IPK) in relation to Low Temperature Heat Release (LTHR), ignition delay, and combustion delay within the Negative Temperature Coefficient region (NTC), utilizing a Box-Behnken design matrix. There were 15 trials of 3 control input parameters which were strategic manipulations of ASTM standard D7668-14a. The standard parameters are: 1000 bar for injection pressure, a combustion chamber temperature of 595.5 °C, and an injection pulse width of 2.5 ms. It was observed that, at ASTM standard, the Derived Cetane Number of neat Ultra-Low Sulfur Diesel (ULSD) and IPK was 47.38 and 25.9, respectively. Results show that the LTHR duration and energy release were reduced when two parameters were simultaneously increased in ULSD operation. Meanwhile, for both fuels, the duration and energy release in LTHR has increased when two parameters were simultaneously reduced. It was found that the lower set wall temperature resulted in increased NTC region and LTHR increased to over 10% of the total energy release. The maximum combustion pressure for both ULSD and IPK where increased by 17.2% and 16.1% respectively from the standard due to the increase in injection pressure and pulse width.

Lean flammability limits of alternative aviation fuels

Alternative fuels are being certified to be used in aircraft. However, the fire-safety properties of these fuels are unknown. The present work focused on measurements of the lean flammability limits (LFLs) of three alternative aviation fuels including Hydroprocessed Esters and Fatty Acids (HEFA), Synthesized Iso-Paraffins (SIP), and Fischer-Tropsch Iso-Paraffinic Kerosene (FT-IPK). The results were compared to that of conventional petroleum-based Jet A. The results showed that only FT-IPK had higher LFLs than that of Jet A. Additionally, the LFLs of four pure hydrocarbons including n-heptane, iso-octane, n-decane, and n-dodecane were measured since they are the major components of transportation fuels. The LFLs were within the range of 0.032–0.040 in terms of the fuel-air mass ratio for all four aviation fuels in the temperature range of 350–420 K. Unlike temperature, pressure had a minor influence on the lean flammability limit. For all measured samples (pure hydrocarbons and fuels), the lean limit decreases with increasing molecular weight.

The importance of incorporating intertemporal and spatial log market dynamics in projections of residue-based biomass supply for liquid biofuel production in western Oregon and Washington, USA

New methods of fiber pre-processing and cellulosic fermentation may allow production of isoparaffinic kerosene, a bio-based jet fuel, from abundant post-logging biomass residues in western Oregon and Washington, USA. Since production of these residues is characterized by complex spatial patterns that can shift markedly over time, and since residues may comprise roughly one-fifth of annual refinery operating costs, careful evaluation of residue supply (quantity/price) behavior is warranted. We examine potential residue supply characteristics at two likely refinery sites (Longview, WA and Springfield, OR) using a projection model of the regional log market that explicitly recognizes: (i) spatial locations of harvesting activities, (ii) the transportation network and residue haul costs, and (iii) the underlying conditions of the forest resource that determine harvesting methods and residue collection costs. We find that delivered residue prices in the range of $US64–75/bone dry metric tonne (BDMT) would be required to provide the 771,100 BDMT per year needed by a minimum commercial-sized refinery operation. Timber ownership and spatial harvesting patterns could give the Longview location nearly a $US12/BDMT wood cost advantage over Springfield at this minimum supply level, and operation of the Longview site would limit Springfield's ability to meet the minimum supply volume. Scenario analyses of lower residue collection costs indicate that a 1% reduction in costs could yield 0.6–0.9% increases in delivered supply at both refinery sites in the neighborhood of the minimum scale of commercial operation. Simulations of tripled residue output from federal lands, assuming RIN eligibility, suggest 15–30% increases in delivered residue supply at Springfield but only 0–10% increases at Longview, reflecting greater area and closer proximity of federal lands at Springfield.

Experimental characterization of jet fuels under engine relevant conditions – Part 1: Effect of chemical composition on autoignition of conventional and alternative jet fuels

Conventional and synthetic alternative jet fuels possess distinctive chemical compositions and physical/chemical properties since they are produced through different production processes. In this paper, the autoignition characteristics of four conventional aviation jet fuels (Jet-A POSF-4658, Jet-A POSF-10325, JP-5 POSF-10289, JP-8 POSF-6169), five alternative jet fuels (Syntroleum S-8 (S8), Shell synthetic paraffinic kerosene (Shell SPK), Sasol iso-paraffinic kerosene (Sasol IPK), hydro-processed renewable jet (HRJ8), alcohol to jet (ATJ), and 50/50 vol% blends of JP-8/alternative jet fuels were explored. The objective of the current work is to understand how the chemical composition of the fuels affects the gas phase chemical kinetic behavior and the ignition process of the liquid spray in an engine-relevant environment, thereby ultimately enabling their use in military ground vehicles with compression ignition engines. A modified Cooperative Fuel Research (CFR) motored engine was utilized and the gas phase ignition behavior was observed over a wide range of temperatures and pressures, while varying the compression ratio. In addition, an optically accessible constant volume spray combustion chamber was employed to observe significant differences in the global heat release characteristics and physical/chemical ignition delay times of synthetic alternative jet fuels in comparison to the conventional jet fuels. The results of this study show that synthetic alternative jet fuels with predominantly linear and lightly-branched alkane content (S8, Shell SPK and HRJ8) provide stronger low-temperature ignition characteristics, while other types of synthetic alternative jet fuels with high content of highly-branched alkanes (Sasol IPK and ATJ) exhibit weaker low-temperature ignition characteristics, when compared to conventional jet fuels (JP-8, Jet-A and JP-5). Their unique fundamental ignition behaviors, including the percentage of low-temperature heat release (% LTHR), the critical compression ratio (CCR), and the critical equivalence ratio (ϕcrit), are strongly related to the dominant chemical compositions of the fuel in a motored engine.

The capability of organic compounds to swell acrylonitrile butadiene O-rings and their effects on O-ring mechanical properties

As interest in replacing petroleum-derived aviation fuels with resilient, alternative fuels increases, the ability to derive correlations between the chemical compositions of aviation fuels and their properties and performance becomes more important. In this work, correlations between the exact chemical structures of organic compounds and their ability to increase the volume and decrease the tensile strength of Buna-N o-ring seals were explored. Buna-N o-ring seals are a representative group of essential seals in the hydraulic and pneumatic components of aircraft fuel delivery systems. They are utilized to prevent fuel leakage within the pumps, metering devices, and connectors. To measure the volume swell percent of o-ring seals caused by various organic compounds, a test rig was assembled that suspended o-ring seals in neat Sasol IPK (isoparaffinic kerosene) or in Sasol IPK doped individually with an organic compound at 8% by volume. Of the aromatic compounds tested, ethylbenzene and indane swelled o-ring seals most effectively, with volume swell percent values of 3.1 ± 0.2% and 2.8 ± 0.1%, respectively. In comparison, the approved aviation fuel Jet A/HEFA has volume swell percent value of 2.2 ± 0.2%. Alkylbenzenes with a smaller number of alkyl groups, less branching in the alkyl groups, and shorter alkyl chains caused greater swelling and greater decrease in the tensile strength for o-ring seals. Naphthene-containing aromatic compounds (i.e., indane and tetralin) swelled o-ring seals more effectively than alkylbenzenes with the same number of carbons (i.e., n-propylbenzene and n-butylbenzene). Therefore, steric hindrance seems to have an important impact on the ability of these compounds to swell o-rings. Nonaromatic unsaturated hydrocarbons, such as cyclohexene, were also found to swell o-ring seals to some extent. On the other hand, saturated hydrocarbons, such as cyclohexane, contributed to minimum or no swelling. Tensile strengths of intact o-rings were measured using an MTS Insight Electromechanical Testing Instrument. Aromatic compounds that facilitated greater swelling of o-ring seals also caused greater decrease in the tensile strength. For example, ethylbenzene and sec-butylbenzene, with volume swell percent values of 3.1 ± 0.2% and 0.9 ± 0.1%, respectively, reduced the o-ring tensile strength from 15.4 MPa to 13.6 MPa and 14.9 MPa, respectively. Additional experiments demonstrated that volume swell and tensile strength of o-ring seals are reversible properties. Hence, a decrease in tensile strength for o-ring seals does not imply irreversible damage. Overall, the extent of volume swelling and the lowering of tensile strength for o-ring seals was found to depend on the exact chemical structure of the organic compound.

Life cycle assessment of residual lignocellulosic biomass-based jet fuel with activated carbon and lignosulfonate as co-products

BackgroundBio-jet fuels are emerging as a valuable alternative to petroleum-based fuels for their potential for reducing greenhouse gas emissions and fossil fuel dependence. In this study, residual woody biomass from slash piles in the U.S. Pacific Northwest is used as a feedstock to produce iso-paraffinic kerosene, through the production of sugar and subsequent patented proprietary fermentation and upgrading. To enhance the economic viability and reduce the environmental impacts of iso-paraffinic kerosene, two co-products, activated carbon and lignosulfonate, are simultaneously produced within the same bio-refinery. A cradle-to-grave life cycle assessment (LCA) is performed for the residual woody biomass-based bio-jet fuel and compared against the cradle-to-grave LCA of petroleum-based jet fuel. This paper also discusses the differences in the environmental impacts of the residual biomass-based bio-jet fuel using two different approaches, mass allocation and system expansion, to partition the impacts between the bio-fuel and the co-products, which are produced in the bio-refinery.ResultsThe environmental assessment of biomass-based bio-jet fuel reveals an improvement along most critical environmental criteria, as compared to its petroleum-based counterpart. However, the results present significant differences in the environmental impact of biomass-based bio-jet fuel, based on the partitioning method adopted. The mass allocation approach shows a greater improvement along most of the environmental criteria, as compared to the system expansion approach. However, independent of the partitioning approach, the results of this study reveal that more than the EISA mandated 60% reduction in the global warming potential could be achieved by substituting petroleum-based jet fuel with residual woody biomass-based jet fuel. Converting residual woody biomass from slash piles into bio-jet fuel presents the additional benefit of avoiding the impacts of slash pile burning in the forest, which results in a net negative impact on ‘Carcinogenics’ and ‘Respiratory effects’, and substantial reduction in the ‘Smog’ and ‘Ecotoxicity’ impacts. The production of woody biomass-based bio-jet fuel, however, did not show any significant improvement in the ‘Acidification’ and ‘Eutrophication’ impact categories.ConclusionsThe study reveals that residual woody biomass recovered from slash piles represents a more sustainable alternative to petroleum for the production of jet fuel with a lower impact on global warming and local pollution. Future research should focus on the optimization of chemical processes of the bio-refinery to reduce the impacts on the ‘Acidification’ and ‘Eutrophication’ impact categories.

‘Woods-to-Wake’ Life Cycle Assessment of residual woody biomass based jet-fuel using mild bisulfite pretreatment

The residual woody biomass (a.k.a. harvest slash) produced during forest harvest operations in the Pacific Northwest is generally collected into piles and burned and/or left on the forest floor to decompose. Producing drop-in biofuels from this residual cellulosic feedstock can provide an alternative use for this unused resource while simultaneously displacing petroleum based fuels. Utilizing a ‘Woods-to-Wake’ (WoTW) Life Cycle Assessment (LCA) approach, which is comparable to a Well-to-Wake (WTW) LCA for petroleum based aviation fuel, this paper assesses the environmental implications of feedstock recovery, production, and utilization of residual woody biomass based biojet fuel. This paper also presents a comparative assessment of the environmental implications of substituting petroleum based jet fuel with that of residual woody biomass based biojet fuel.The bioconversion process presented in this paper uses a mild bisulfite pre-treatment of the feedstock to liberate the C5 and C6 sugars which then go through enzymatic hydrolysis and saccharification to produce fermentable sugars. The sugars are then converted to bio-jet fuel (iso-paraffinic kerosene, IPK) using a proprietary biocatalytic fermentation and oligomerization process. The WoTW environmental implications of producing woody biomass based jet-fuel are then compared to the WTW environmental impacts of producing petroleum based jet-fuel. The results reveal that the WoTW global warming impact of residual wood based bio-jet fuel represents a 78% improvement over the WTW global warming impact of petroleum-based jet fuel.

ELLIPSOMETRIC MEASUREMENTS OF THE THERMAL STABILITY OF ALTERNATIVE FUELS.

Thermal stability is an important characteristic of alternative fuels that must be evaluated before they can be used in aviation engines. Thermal stability refers to the degree to which a fuel breaks down when it is heated prior to combustion. This characteristic is of great importance to the effectiveness of the fuel as a coolant and to the engine's combustion performance. The thermal stability of Sasol IPK, a synthetic alternative to Jet-A, with varying levels of naphthalene has been studied on aluminum and stainless steel substrates at 300 to 400 °C. This was conducted using a spectroscopic ellipsometer to measure the thickness of deposits left on the heated substrates. Ellipsometry is an optical technique that measures the changes in a light beam's polarization and intensity after it reflects from a thin film to determine the film's physical and optical properties. It was observed that, as would be expected, increasing the temperature minimally increased the deposit thickness for a constant concentration of naphthalene on both substrates. The repeatability of these measurements was verified using multiple trials at identical test conditions. Lastly, the effect of increasing the naphthalene concentration at a constant temperature was found to also minimally increase the deposit thickness.

Reduction of Aircraft Gas Turbine Noise with New Synthetic Fuels and Sound Insulation Materials

The need to reduce the sound and vibration characteristics in the aerospace industry is continuously increasing because of the need to meet FAA regulations, to reduce noise pollution, and to improve customer satisfaction. To improve customer satisfaction, aircraft and engine manufacturers must work to control sound and vibration levels so that passengers do not experience discomfort during a flight. Sound and vibration characteristics of a fixed-wing aircraft with jet engines are composed of complex-frequency contents that challenge engineers in the development of quiet engine designs, aerodynamic bodies, and advanced sound- and vibration-attenuating materials. One of the noisiest parts of an aircraft, the gas turbine, was analyzed in this research. In Part 1 of this project, the use of alternative fuels in a gas turbine engine was investigated to determine whether those fuels have negative effects on sound and vibration levels. Three types of fuels were used: Jet A as the reference fuel, natural gas–derived S-8, and coal-derived isoparaffinic kerosene (IPK). The alternative fuels, S-8 and IPK, are Fischer–Tropsch process fuels. Overall sound and vibration characteristics of the alternative fuels presented a similar pattern across the frequency spectrum to those of the reference fuel, with the alternative fuels being slightly quieter. In Part 2, the sound path was treated by introducing sound-absorbing materials and investigating their acoustic performance. A melamine-based foam and soy-based foam were used in this research. Melamine is very lightweight, has excellent thermal endurance, and is hydrophobic. The soy-based foam was selected for its potential application in the aerospace industry to work toward a greener aircraft, in an effort to promote environmental sustainability. The soy-based material reduced the sound level by more than 20 dB(A) and presented better performance than the melamine at high frequencies.

Demonstration of a Regulatory Method for Aircraft Engine Nonvolatile PM Emissions Measurements with Conventional and Isoparaffinic Kerosene fuels

The aviation industry is exploring the economic viability and environmental sustainability of the use of alternative fuels to power aircraft main engines and auxiliary power units. The International Civil Aviation Organization is also developing a regulatory standard for aircraft engine nonvolatile particulate matter (nvPM) emissions to meet the growing public demand for improvement in air quality. This study compared the nvPM emissions in the exhaust stream of a small (<26.7 kN thrust) mixed turbofan aircraft engine burning a conventional Jet A fuel as well as a Sasol isoparaffinic kerosene (IPK) fuel derived from coal, using a standardized sampling and measurement system. The goal of the study was to demonstrate the regulatory system on a small mixed turbofan engine and to assess the suitability and limitations of using such systems for turbofan engines burning fuels with different fuel properties. Significant reductions in both nvPM number- and mass-based emission indices were observed with the IPK fue...

Process development and demonstration of coal and biomass indirect liquefaction to synthetic iso-paraffinic kerosene

To demonstrate coal- and biomass-to-liquid (CBTL) hydrocarbon fuel technology, a supported, iron-based Fischer–Tropsch (FT) catalyst was developed. The catalyst preparation procedure was optimized and then scaled up to produce 2 kg of catalyst to fill a pilot-scale FT reactor system. Synthesis gas was produced from a fluidized-bed gasification system that is capable of processing up to 9 kg/h of coal and biomass. Impurities from the raw syngas such as sulfur, tars, and particulate matter were reduced to levels that would not significantly diminish FT catalyst performance. The gasification and FT reactor systems were operated continuously for 5 days on feed stocks consisting of sub-bituminous coal and blends of coal and various biomass sources such as olive pits, switchgrass, and dried distillers' grain. Liquid and wax hydrocarbon products were collected and subsequently upgraded into synthetic isoparaffinic kerosene, which used elements of a proprietary process for converting crop oils into jet fuel. The finished fuel very nearly met specifications for synthetic military-grade isoparaffinic kerosene.

Properties, Characteristics, and Combustion Performance of Sasol Fully Synthetic Jet Fuel

In 1999, as the only inland petroleum refinery in South Africa was reaching capacity, Sasol gained approval of a semisynthetic jet fuel (SSJF) for civil aviation to augment production and meet the growing demand for jet fuel at the airport in Johannesburg. Prior to this, all jet fuel had to be refined from petroleum sources. SSJF consists of up to 50% of an isoparaffinic kerosene produced from coal using Fischer–Tropsch processes. The production of SSJF remains vulnerable to the production capacity of conventional jet fuel, however. To ensure supply, Sasol has proposed producing a fully synthetic jet fuel (FSJF) using synthetic kerosene streams that contain aromatics and satisfy all the property requirements of international specifications for jet fuel. Being fully synthetic, it was necessary to demonstrate that the fuel is “fit-for-purpose” as jet fuel, i.e., behaves like conventional jet fuel in all aspects of storage and handling as well as air worthiness and flight safety. Four sample blends were developed, covering the practical range of production. Extensive tests on chemistry and physical properties and characteristics demonstrated that Sasol FSJF will be typical of conventional jet fuel. As a final demonstration, the engine manufacturers requested a series of engine and combustor tests to evaluate combustion characteristics, emissions, engine durability, and performance. The performance of the synthetic test fuel was typical of conventional jet fuel. This paper identifies the tests and presents the results demonstrating that Sasol fully synthetic jet fuel is fit-for-purpose as jet fuel for civilian aviation. Sasol FSJF is the first fully synthetic jet fuel approved for unrestricted use.