Step on the gas

As the race gathers pace to find the ‘green’ fuel of the future for cars, could the answer be found in the deserts of Qatar? Shell certainly thinks so. George Coupe reports.

If you follow the road north out of Dawhah, about half an hour’s drive across the desert will bring you to Ras Laffan industrial city.

In 1990 there was nothing to see here, only a sunburnt and dusty promontory that jutted into the sea on Qatar’s eastern shore. Within 10 years industry sprouted across more than 100m2 of this desolate place. The reason: gas – more gas in a single place than anywhere else in the world.

Ras Laffan is located strategically at the centre of the Arabian Gulf on Qatar’s vast northern gas field. It holds nine per cent of the world’s proven gas resources. This is where Qatar has embarked on the execution of its Strategic Plan for Natural Gas Utilisation, and the city accommodates a range of gas-based industries including liquefaction, processing and export, petrochemicals, refining of condensates and the construction of the world’s largest port exporting LNG to serve these activities.

But that is not the end of it: a new type of fuel production has taken root in the past few months and is scheduled for rapid growth. A huge second round of construction and investment is set to take place, and fuel producers, car makers and aviation experts are talking excitedly about the prospects for their new baby to be born at Ras Laffan.

The fuel in question is synthetic diesel, produced from natural gas, and known as gas to liquid fuel, GTL.

While the concept of the hydrogen fuel economy remains a dim and distant prospect, GTL diesel is being promoted by the fuel industry as the most viable next step towards a sustainable transport future. The likes of Shell, ChevronTexaco, BP and ExxonMobil have all been involved in developing the technology to convert natural gas to diesel and most are now on the threshold of commercialising their processes, a large proportion of which will take place at Ras Laffan.

GTL fuel offers lower emissions with improved performance and efficiency. It contains next to no sulphur (one part per million), and is one per cent aromatics. It also has a much higher cetane number (75-80) than conventionally produced fuel, offering more complete combustion.

On average GTL fuel in a modern diesel engine would produce approximately 40 per cent less particulates; five per cent less NOx; 60 per cent less hydrocarbon and 75 per cent less carbon monoxide than current European fuel.

The major advantage of GTL diesel over LNG, CNG and hydrogen is that it can be used in conventional diesel engines, without modification, to instantly reduce pollution and noise. It can also be distributed via the existing supply infrastructure, unlike hydrogen. In the future, according to the fuel producers, the introduction of sulphur-free fuel will allow a new generation of exhaust filters to be used that could ‘virtually eliminate tailpipe emissions’.

Similarly the improved combustion qualities of GTL fuel offer some potential for the development of yet more efficient diesel engines. Together these advantages would foster a global shift away from petrol/spark-ignition engines to higher-performance and ultra-clean/efficient diesels.

Several major car manufacturers, including Mercedes Benz, Mitsubishi and Toyota, have or are in the process of conducting road trials of GTL fuel. The most recent is taking place in London. Earlier this month Toyota and Shell donated 10 cars to three local charities to run on GTL fuel for three months.

Mike Hawes of Toyota Motor Europe said that at this stage his company has its eyes firmly on incoming European legislation which will demand dramatic cuts in the levels of car exhaust emissions. ‘The use of GTLs in the conventional commonrail diesel engine, combined with the DCAT exhaust system, should enable Toyota to reduce emissions in line with the Euro 4 levels which come into effect next year.’

Euro 4 will limit the amount of sulphur in all petrol and diesel to 10 milligrams per kilogramme, or 10 parts per million, by January 2009. The current level is about 50ppm. The directive also mandates that sulphur-free diesel must be at least available in member states no later than January next year.

Hawes added that Toyota is also looking ahead to Euro 5 and believes that GTL could enable the company to cut emissions from its engines even further. ‘We believe that the regulations on emissions can and should be tighter.’

But what about the other benefits extolled by the fuel companies? How likely is it that car makers such as Toyota will actually take the plunge and invest in a new engine design? ‘When a new fuel becomes available in commercial quantities there is an opportunity to design a bespoke engine to maximise the benefits offered by that fuel,’ said Hawes. ‘At the moment we cannot see any downside with GTL fuels. If we can find a way of improving the engine’s power without sacrificing the progress on emissions or economy, then clearly this engine would be a very attractive prospect.’

The key to success for GTL, then, will be ready availability: enough fuel to make it possible for fleet owners around the world to transfer from less efficient gasoline engines to the new diesel technology. The other crucial factor will be price. But GTL fuel has never been produced on a commercial scale large enough to supply the road transport market. So why did Shell, for example, decide at the end of last year to invest $5bn (£2.75bn) in building the first world-scale GTL plant (140,000 barrels per day) in Qatar?

New legislation is helping to create favourable market conditions for GTL diesel in Europe. Other parts of the world, however, consider ‘clean’ diesel to be anything with a sulphur content as high as 500ppm. In the US and Australia diesel is seen as dirty and noisy, and until recently policy discussion focused solely on alternatives such as CNG, LPG biofuels and hydrogen. However, the US will also tighten rules on exhaust emissions by 2006.

Like other technologies that are being considered for the future of motor transport, such as the hydrogen fuel cell, the method for converting natural gas into a liquid was invented many decades ago.

The Fischer-Tropsch process (invented in Germany in 1913) is the bench-top technology the big fuel producers plan to scale up at Ras Laffan. Again, like the early fuel cell, the system, although relatively simple, was far from practical in economic terms. Pioneers such as Shell and the South African fuel producer Sasol have spent millions and many years refining the technology to reduce its unit cost.

The processes both companies plan to use in Qatar are essentially similar. They each follow three fundamental steps. The first is to reform the natural gas into synthesis gas (syngas), a predetermined mixture of hydrogen and carbon monoxide. Next the syngas is passed through the Fischer-Tropsch reactor, where in both cases a cobalt-based catalyst (low temperature) will be used to produce a variety of liquid hydrocarbons in the form of a synthetic version of crude oil (syncrude). Following this, the syngas-derived liquid will be upgraded and refined into a specific slate of fuels or petrochemicals.

Shell’s integrated plant at Ras Laffan, which will include the gas extraction as well as its conversion, is the largest planned in the world today. Neil Fabricius, technical director of the Qatar Shell GTL project, said preparations for the plant are now well underway. ‘We are in the beginning of the front-end engineering design phase, FEED, and we are working with JGC Inc and MW Kellogg, work that started in March this year. In parallel with this we started the first appraisal drilling, two appraisal wells, and the first was spudded in February, and we are in the final phase of the testing.’

The Shell Middle Distillate Synthesis process has been successfully developed and tested in its mid-scale (15,000bpd) GTL plant at Bintulu, Malaysia, which began operating in 1993.

The Qatar Shell GTL project will produce naphtha, kerosene and some speciality chemical feedstocks, but the primary focus will be on ultra-clean diesel. ‘The emphasis in our product slate is on middle distillates, and that is achieved at a low temperature and for a low temperature you need a high-activity catalyst,’ said Fabricius.

In 1993 Shell still had to improve the process to make it economic. The breakthrough came in 2000 with the launch of the cobalt-based catalyst. ‘The main issue was to develop the technology to a stage that it is economic, and for Shell the big breakthrough was a second-generation catalyst which was finally proven in the pilot plant and now also in Bintulu,’ said Fabricius.

‘The main feature is that in the same reactor you will basically be able to produce considerably more products. It is both active and stable and these are always two conflicting things. It is working satisfactorily in the Bintulu plant. That was the breakthrough, together with some design developments that brought the whole economics picture together to show that it is robust, even at a reasonably low oil price.’

Shell’s design can also easily be scaled up, and that is another reason, according to Fabricius, why the company is willing to make the jump to a 140,000bpd plant. ‘Clearly all the experiences gained in Bintulu are the cornerstone of the confidence we have in going forward on this huge scale. Our plan is to build a 140,000bpd plant, with two trains of 70,000bpd, but with each train containing multiple sections. In the syngas manufacturing you have multiple gasifiers, in the Fischer-Tropsch synthesis you have multiple reactors.’

The size of the plant will present new technical challenges, however. ‘The Fischer-Tropsch process is immensely exothermic and so is syngas manufacturing. The total release of process heat from these is in the order of 5GW, which you want to harness and use actively in the process and still have it operable. That is a huge challenge,’ said Fabricius.

The first 70,000bpd train is due to begin production in 2009, with the second opening the following year. The products are valued on current blending prices in refinery use, without a premium. ‘On that assumption the total project is robust against the Shell screening criteria which are pretty conservative, at oil prices below $20 [£11],’ he said.

Shell’s plant, however, will not be the first commercial-scale GTL project to open in Qatar. Sasol and its joint venture company SasolChevron are involved in developing three GTL plants at Ras Laffan. The companies have rapidly increased their stake on the Northern Field. The first project, Oryx, is a 34,000bpd plant, 51 per cent owned by Qatar Petroleum and 49 per cent by Sasol. SasolChevron provides technical support and advice as required by the Sasol parent company.

That plant is in the middle of construction. ‘In low temperature terms we view it as really the first truly commercial plant. Obviously Shell is running Bintulu, but Oryx was actually designed to make a profit. Clearly 34,000bpd is probably the smallest thing we will ever build – we would view that as a commercial quantity but only just,’ said Malcolm Wells, a spokesman for SasolChevron. The second step will be Oryx 2, a 65,000bpd extension plant.

Next will come an integrated plant. Like the giant Shell plant it will have both a downstream and an upstream element. Charlene Pretorius, manager of technology and environment on the SasolChevron GTL project in Qatar, said once they have extracted the gas from their own platform it will go through a purification process to remove sulphur and metals such as mercury, before it is reformed into the syngas, and then put into the Fischer-Tropsch reactor.

‘Once again over a catalyst the two components, the CO and hydrogen, are converted to longer-chain molecules and you typically produce a whole range from a condensate fraction to the very heavy waxy medium from which the [fuel] products are made, and also you create a lot of reaction water.

‘Then the condensate, the wax and the water are treated further. The condensate and the wax go to the third main process block, the product work-up unit, which is where they are split into the different fractions. Our main product is diesel, which represents about 66 per cent of the product slate, and then there is a naphtha fraction which is 22 per cent or so and then you have LPG which is about two or three per cent,’ she said.

Like Shell, Sasol has gained experience with its own Fischer-Tropsch plant in South Africa. This, however, relies on an iron-based, high-temperature catalyst, which is more suitable for the production of gasoline and other petrochemicals.

‘The Qatar plant is a low-temperature process with cobalt catalyst. The one in South Africa we scaled up from very small to a 200,000bpd facility. We are quite confident in scaling up the [low-temperature] FT process – we have developed it in the same way from micro unit to pilot to demonstration unit and the Oryx plant in Qatar is the first large-scale plant.’

Although designs have not been finalised, SasolChevron plans a ‘big’ increase in capacity over that of Oryx 1 for the integrated plant. As with Shell this will be achieved with multiple trains of around 22,000bpd each. Pretorius said this scalability is crucial to economic viability. ‘If there is the opportunity to add more trains, then you can bring your unit cost down.’

The demand for GTL fuel will be crucial to its viability. Another potential route to market is via the conventional refiners who can blend GTL with diesel produced from crude oil. This will help to improve the environmental credentials of conventional diesel, without the cost of having to reconfigure the refinery to meet the ever tougher specifications, said Wells.

‘It’s a combination of things. GTL is actually the first of the alternative fuels and at this stage it’s the more viable. GTL diesel is ready now – we can produce it at a commercially viable level. Oryx was for example financed on the international money market, and that’s a very tough court to convince. Also if you look at the trend in transport fuels compression ignition would seem to be the future in terms of efficiency over spark ignition.’

So if the technology and the market is ready, does anything stand in the way of the GTL industry? According to Fabricius, logistics is the the most immediate concern. The breathtaking rate of expansion planned at Ras Laffan will be difficult to manage.

‘This is truly a big project, where you are talking something like 2,300 equipment items for the total of the two Shell phases alone. More than 100,000 tonnes of equipment will need to be brought in, and the simple logistics of bringing all that to Ras Laffan where there are numerous other projects going on at the same time is quite a challenge.

‘Qatar has tremendous ambitions and there seems to be no end to the number of contracts being signed,’ said Fabricius.