SASOL, South Africa’s global, oil-from –coal pioneer, scored a major triumph at the AAD 2010 exhibition at the Ysterplaat Air Force Base, Cape Town, recently when the world’s first flights using its internationally approved, fully synthetic jet fuel, landed there soon after the gates to the exhibition area had opened.
The landmark flights to Ysterplaat took off a few hours earlier from both Lanseria International Airport, near Johannesburg, and Kruger Mpumalanga International Airport, Nelspruit.
Involved in the historic operation were three National Airways Corporation turbine-powered aircraft-the flagship Hawker 4000 corporate jet, atop-of-the-range Beech craft King Air 350i and a PAC750 equipped with a state-of-the-art airborne surveillance system-and a chartered Boeing 737-200,all of which were the first aircraft to use Sasol’s 100% Synthetic Jet A-1.
This is the only fully synthetic fuel that is a true “drop-in” replacement for conventional jet fuel that is approved for commercial use in all types of turbine aircraft around the world. The Jet A-1 fuel that was used is made using Sasol’s proprietary Fischer-Tropsch technology that produces liquid fuel from coal at its Synfuels production plant in Secunda, South Africa.
Although the 100% synthetic Jet A-1 fuel is not yet commercially available, Sasol has supplied jet fuel since 1999 that is a 50:50 blend of synthetic and conventional ,crude-oil-derived JetA-1 fuel to the country’s main gateway, the OR Tambo International Airport, near Johannesburg.
The flights to the AAD exhibition using the 100% synthetic jet fuel were the culmination of a complex process that resulted in Sasol receiving the worlds first formal approval of a fully synthetic jet fuel published in Issue 6 of the Defence Standard 91-91 in April 2008, followed soon after by the inclusion in the USA jet fuel specification ASTM D1655.
Sasol is an integrated energy and chemicals company operating predominantly in South Africa ,where its history dates back to its establishment in 1950.Sasol currently has operations in 38 countries, employs about 34000 people, and is listed on both the Johannesburg and New York stock exchanges.
Technology is core to Sasol and, through its proprietary Fischer-Tropsch (FT) technology; Sasol converts coal and natural gas into liquid fuels, fuel components and chemicals. Sasol has chemical manufacturing and marketing operations in South Africa, Europe, Asia, and the Americas, and it mines coal in South Africa, extracts gas in Mozambique and oil in Gabon.
Pioneering Alternative Jet Fuels
Although Sasol focused primarily on the production of chemicals, road transportation fuels and the jet fuel from crude oil in the first four decades of its existence, a prediction in the mid-1990s of an imminent shortage of jet fuel at what is now the OR Tambo International Airport prompted Sasol to investigate opportunities for the production and qualification of synthetic jet fuel.
Road transportation fuels specifications are allowed to vary from one region to another, but the development of a viable alternative fuel for aviation application requires a drop-in replacement fuel with global acceptance and approval by all the international stakeholders.
In June 1996, Sasol embarked on discussions with international specification authorities, including the American Society for Testing and Materials(ASTM) and the British Ministry of Defence (UK MoD) .Between 1996 and 1998 ,Sasol conducted extensive laboratory and engine test work in South Africa and the USA to gain understanding ,acceptance, and demonstration of the use of an FT-derived synthetic jet fuel component up to a maximum of 50 volume percentage when blended with crude oil-derived jet fuel.
In April 1998, Sasol became the first company in the world to gain approval for the commercial use of a synthetic jet fuel component at up to 50% in a blend with petroleum kerosene as Jet A-1 .This approval for the use of iso-paraffinic kerosene (IPK), produced by the Sasol Synfuels facility in Secunda, was written into the UK MoDs Defence Standard (DEFSTAN 91-91),Issue 3.On February22,1999,Sasol made history by certifying the first batch of Sasol semi-synthetic jet fuel at the Natref refinery in Sasolburg, and since then, most aircraft leaving OT Tambo International Airport have flown on Sasol’s semi-synthetic jet fuel.
100% Synthetic Jet Fuel
Between 2001 and 2007, Sasol continued with extensive test work on blends of potential jet fuel streams from its synfuels facility with the aim of gaining official qualification of a fully synthetic jet fuel. In support of this objective, the prestigious Southwest Research Institute (SWRI) in San Antonio, Texas, was commissioned and a joint research report was submitted to the UK MoD in December 2003 with a request to approve the use of fully synthetic jet fuel as a commercial aviation turbine fuel.
The major engine manufacturers required further engine tests, including an endurance test on a Pratt & Whitney JT-9D engine, to be performed before final approval could be given. The 250-hour endurance test, conducted in February 2006 at the engine overhaul facilities of South African Airways in Johannesburg, necessitated the special production of 1, 2-million litres of synthetic jet fuel in Secunda.
Finally, in April 2008, the formal approval of Sasol fully synthetic jet fuel from the Synfuels plant in Secunda was published in Issue 6 of the Defence Standard 91-91.
Following shortly afterwards, Sasol’s fully synthetic jet fuel was also included in the USA jet fuel specification, ASTM D1655.Sasols 100% synthetic Jet A-1 from Synfuels was thus approved for commercial use in all types of turbine aircraft in the USA (ASTM D1655) and the rest of the world (DEFSTAN 91-91), and it remains on this day the only fully synthetic fuel that is a true drop-in replacement for conventional jet fuel.
The fuel is fully fungible and aligned with the current aviation infrastructure .It is compatible with existing jet engine requirements and can be used with conventional crude oil-derived jet fuelling systems.
Synthetic Jet A-1 Production
Sasol Synfuels is based in Secunda where it operates the world’s only commercial, coal-based, synthetic fuels manufacturing facility. A high temperature Fischer-Tropsch (HTFT) process, utilizing the unique Sasol Advanced Synthol technology, converts low-grade coal into fuel (LPG, petrol, kerosene and diesel) as well as chemicals .The coal-to-liquids (CTL) plant in Secunda produces approximately 160000 barrels per day of FischerTropsch Products.
This facility uses the Sasol, fixed bed, dry bottom (FBDB) gasification process to convert the coal into synthesis gas. The Fischer-Tropsch process is catalyzed, chemical reaction in which the synthesis gas, a mixture of carbon monoxide and hydrogen, is converted into liquid hydrocarbons of various forms (synthetic fuel).
The Fischer-Tropsch process can proceed through low temperature fischer-Tropsch (LTFT) or HTFT technology, with the main differences between the two processes being the operation parameters, reactor type, product spectrum and catalyst type.
The range of possible feed materials for the Sasol Fischer-Tropsch synthesis process are firstly, coal (coal-to-liquids, CTL), secondly, natural gas (gas-to-liquids, GTL) or biomass (biomass-to-liquids, BTL).These feed stocks can also be used in combination as is done at the Synfuels’ plant in Secunda where coal and natural; gas have been used together as feedstock since 2003 when pipeline bringing natural gas from Mozambique to Secunda was commissioned.
Five separate hydrocarbon streams in the Synfuels complex, as stipulated in Issue 6 of DEFSTAN 91-91, have been qualified for use in blending 100% Synthetic Jet A-1 .The product that was used in the first demonstration flights last month was blended from two of these streams. These were iso-paraffinic kerosene, which is also used routinely in the semi-synthetic blends supplied to the OR Tambo International Airport, and an aromatics-containing stream derived from severely hydro-treated coal tar kerosene.
It is the latter stream that contributes the required minimum of 8% aromatics and provides the high density and elastomeric seal swell properties to make the synthetic jet A-1 seamlessly compatible with conventional crude oil-derived jet A-1 . A part from the clean-burning nature of the synthetic jet fuel, leading to lower emissions than from conventional Jet A-1, the synthetic product has been shown to contain significantly better thermal and oxidative stability properties than normal jet fuels. This could enable the development of more efficient engines, running at higher temperatures than at present.
Alternative Jet Fuel Developments
Based on the two pioneering Sasol-specific synthetic jet fuel international approvals mentioned above, and with the worldwide drive to qualify alternative jet fuel for commercial use, the need for a generic approval protocol and specification for alternative jet fuel was identified by the aviation community.
The approval process and qualification protocol that was developed by the industry during Sasol’s seven-year quest to qualify 100% synthetic jet fuel became the benchmark for any future alternative fuel. It was subsequently formalized and adopted by the ASTM as specification D4054 “Standard Practice for Qualification and Approval of New Aviation Turbine Fuels and Fuel Additives”.
During the first generic approval process, five blends of individual Fischer-Tropsch-derived synthetic paraffinic kerosenes, blended with crude oil derived jet A, Jet A-1 or JP-8 fuel to produce semi-synthetic jet fuel, were evaluated. Sasol provided three of the synthetic kerosene samples while the other synthetic products were provided by Shell and Syntroleum.
A report prepared for the coordination Research Council in September 2008 concluded that semi-synthetic jet fuel containing up to a maximum of 50% volume of synthetic paraffinic kerosene derived from synthesis gas via the FT processes, complying with specified properties, would be fit for purpose. This was further validated by eleven years of commercial operation on Sasol semi-synthetic jet fuel using its iso-paraffinic kerosene.
In September 2009, a new ASTM specification D7566 (aviation turbine fuel containing synthesized hydrocarbons) was approved. This means that synthetic, FT-derived jet fuel component from any CTL or GTL plant can be blended up to a maximum of 50% of volume in crude oil derived jet fuel-this marked the first generic approval for a jet fuel component, independent of the production facility, based on the Sasol-developed protocol.
Looking Ahead
Sasol has actively participated in changing the jet fuel landscape and pioneering the way for the approval and use of viable alternative fuels. This also opened up opportunities for Sasol to include kerosene in its product offering to the international market from future GTL and CTL Plants.
The approval of synthetic jet fuel without aromatics, as is the case with LTFT jet fuel, is under investigation by the international aircraft industry, and Sasol is part of this initiative. The challenge is the legacy aircraft still in use that need aromatics to ensure elastomeric seal swell, thereby enabling the proper functioning of fuel system.
New and future aircraft are designed to handle fuel without aromatics. The generic qualification of synthesized aromatics as a jet fuel component is currently being pursued to enable fully synthetic LTFT jet fuel in the interim.
A further aspect that is currently receiving more and more research focus is the development of pathways to increase the renewable carbon content of jet fuels, in order to help the aviation industry with the reduction of its carbon footprint.
Given the pioneering role that Sasol has played thus far in alternative aviation fuels and with an increased international focus on all synthetic jet fuels including FT-based synthetic Jet Fuels, this aviation fuels area is exciting place to be.
