PEARL; The Green Jewel

As the aerospace industry continues its search for a greener alternative to today’s aviation fuel, a futuristic facility on the coast of Qatar is poised to deliver one of the answers.

Tapping into one of the world’s largest reserves of natural gas, the Pearl GTL (gas to liquids) plant, with capacity to produce 12,000 barrels of new-generation synthetic kerosene per day, is on the way to completion at Ras Laffan, a vast industrial zone the size of Amsterdam, on Qatar’s coast, some 90 kilometres north of Doha. 

Pearl, a joint development by Qatar Petroleum and Shell, will process about three billion barrels of clean-burning, oil-equivalent products over its lifetime. Apart from the new jet fuel, output will include GTL diesel, automotive lubricants, paraffin (used in detergent production) and naphtha, an essential catalyst in plastics production.

Shell says the project is “proceeding in line with expectations”. Construction is scheduled for completion “around 2010” with what the company describes as “project ramp-up” (the phase leading to start of production) beginning in 2011.

More than 40,000 workers from more than 50 countries are currently engaged in the construction effort, which covers an area equal to New York’s Central Park.

A partnership comprising Qatar Airways, Qatar Petroleum, the Qatar Fuel Company, Airbus, Rolls-Royce, Shell and the Qatar Science and Technology Park is carrying out research into the benefits of synthetic jet fuel and the potential for its commercial use.

The collaboration believes GTL offers a “practical and viable ‘drop-in’ fuel for commercial aviation in the short term,” emphasising its benefits for local air quality (it is virtually sulphur-free) and its potential to improve fuel-burn because of a higher energy content and lower density than today’s Jet A-1.

Qatar Airways has already signalled its intent to be the world’s first commercial airline to operate flights using GTL kerosene. “There is a huge movement lobbying for the reduction in carbon emissions to make for a cleaner and safer environment,” says the airline’s chief executive officer Akbar Al Baker. “As industry leaders, the partners are committed to the cause, and this move highlights how seriously we take the issue.”

Natural gas will be piped to the Pearl facility from two platforms sitting 60 kilometres offshore in the North Field, which stretches from Qatar’s coast out into the Gulf and accounts for around 15% of the world’s reserves.

This will then be converted into a range of products including GTL kerosene, which has properties similar to standard aviation fuel, making it highly compatible when the two are combined.

A fuel mix containing 37% GTL kerosene has already been successfully flight-tested using an Airbus A380. An unmodified Rolls-Royce Trent 900 was fed with the blended fuel, while the remaining three engines used standard Jet A-1. The three-hour exercise measured engine responses throughout the flight envelope to a maximum altitude of 43,000ft. The trial Trent performed successful windmill starts and routinely delivered max power when commanded for a final touch-and-go.

LNG (liquefied natural gas) is a clear, colourless non-toxic liquid that forms when natural gas is cooled to –160C. This shrinks the volume of the gas 600 times, making it easier to store and transport.

The two offshore production platforms sit 40 metres above the seabed. Their top sections have been built at shipyards in Dubai. Eleven wells are being drilled from each platform.

Pearl has been likened to a giant chemistry set. Using natural gas as its starting point, it first combines, then breaks up and rearranges chains of atoms. Chains of varying lengths have different properties, producing a range of GTL products, including synthetic jet fuel.

Construction at Pearl involves two million tons of prefabricated parts for the GTL plant and its equipment, including 12,000 kilometres of cables and enough steel to make 10 Eiffel Towers.  

At the heart of the GTL process are 24 cylinder-shaped, steel reactors, each weighing 1,200 tons – the equivalent of seven Boeing 747s. Built in Germany, they travel by barge to Amsterdam before being shipped to Qatar.

Preliminary results from flight-testing earlier this year involving a Pratt & Whitney-powered Japan Air Lines Boeing 747 show that viable biojet fuels processed from a range of green raw materials can be mixed, both with each other and with standard Jet A-1 kerosene.

Fuel used in the JAL trial was refined from a variety of bio feedstocks including camelina, jatropha and algae.

Alan Epstein, the company’s VP technology and environment, says: “Drop-in, sustainable aviation biojet fuels will reduce aviation’s CO2 while diversifying our fuel supply and promoting energy independence. Aviation no longer needs to bet on a single source of fuel.”

However, to achieve significant performance improvements through the use of next generation fuels, P&W contends that future engines will need to be expressly designed to fly on biojet fuel, or a biojet/kerosene mix which includes at least 25% bio.

“There is no performance gain from biofuels burned in current engines,” says Epstein.  

Last year, P&W approved the use of biofuels in all its non-afterburning military engines (some of which have commercial variants) and expects to clear bio for afterburning fighter aircraft by the end of this year.

The next flight test demonstration with P&W involvement is due next year, using an IAE V2500 on a JetBlue Airbus A320 – Pratt is a senior partner in the four-nation International Aero Engines consortium alongside Rolls-Royce, MTU and the Japanese Aero Engines Corporation. As well as marking a bio debut for the V2500, the flight is believed to be the first using fuel from third-generation feedstock.

In Epstein’s view, challenges of mass production are likely to make biofuels a long-term alternative. “It may be several decades before they are available in the tens of billions of gallons per year this (demand) implies, so we are a way off being able to exploit some superior biofuel properties in our engine designs.”

GROUND TESTS WILL PRODUCE VABUABLE FUELS SCIENCE

Rolls-Royce is continuing its broad-based approach to alternative aviation fuels, including plans to ground-test a variety of contenders in a joint initiative with British Airways.

A number of potential fuel suppliers responded to an initial invitation to bid last year, but only one fully met the required criteria, leading Rolls and BA to conclude that the position was not yet mature enough to proceed. The electronic bid process is due to be repeated towards the end of the year, or early in 2010.

Robert Nuttall, vice president, strategic marketing at Rolls-Royce, says: “We’re keen to ensure as much quality science as possible sits behind fuel research. This is a global issue and the results of these trials will be made available publicly so that the whole industry, its customers and the environment itself can benefit.”

BA will supply one of its RB211-524 fleet engines for the testing, which will be carried out at the Rolls-Royce civil aerospace facilities in Derby, UK. A key feature of the exercise is the plan to include a range of synthetic or bio fuels in side-by-side comparisons, both with each other, and standard Jet A-1 aviation fuel.

“We’ll be looking to try and clear biofuels for commercial flying in the next two years, in conjunction with the wider industry,” says Nuttall. “Of the views currently out there, the most optimistic is that 30% of aviation fuel, by volume, could be from bio stocks by 2030.”

As well as its involvement in the A380/Trent 900 GTL (gas to liquid) kerosene flight-test last year, Rolls-Royce also took part in a joint exercise with Air New Zealand and Boeing using an RB211-524-powered 747. The segregated engine was fed with a 50-50 mix of Jet A-1 and biofuel derived from jatropha. Data analysis resulted in predictions that the bio drop-in would improve fuel-burn by 1.2% on long-haul flights (12 hours/5,800 n.m.) with an anticipated 1% benefit on shorter routes. 

Rolls-Royce bases its outlook on three triggers: suitability, sustainability (effects on food production and land use) and scalability – the issue of commercial production.

“Volume and consistent quality are obviously key issues,” says Nuttall. “If you want to replace half the world’s kerosene, you have to build half the world’s refining capacity, which has taken decades to get where it is today.”