Sulphur yields new products

DOHA // A looming world glut of sulphur is prompting Royal Dutch Shell to come up with new uses for the distinctive yellow substance that is already stockpiled in some gas-producing countries.

At a laboratory in Qatar, the Gulf state with the world's biggest deposit of sulphur-laced gas, researchers test new building materials strengthened with sulphur. They include a plastic-like sulphurated concrete and a sulphur asphalt for road surfaces.

The company hopes to prove that each is more durable than the comparable conventional product as it attempts to develop new sulphur markets.

The poisonous gas hydrogen sulphide is found in many natural gas reservoirs in the Gulf region and elsewhere, especially those that are deeply buried. These so-called sour gas deposits are increasingly being tapped because gas reserves with low sulphur content are depleted.

"We are looking for new applications for sulphur because more and more sour fields are being developed," said Willem Scholten, the research and development manager of the Qatar Shell Research and Technology Centre in Doha.

To make sulphur concrete, molten sulphur, instead of water and cement, is blended with crushed rock. The result is a building material with a smooth plastic surface that is easy to paint and which sets much faster than normal concrete while being more resistant to salty and acidic conditions.

Those properties particularly suit the material to the construction of walls and barriers exposed to water, such as dykes around low-lying land areas, hydro-electric dams, the linings of man-made ponds for aquaculture and waste treatment, and the embankments and locks of canals.

Sulphur concrete might be a particular boon to the construction sectors of fast-growing economies in the Gulf region, where fresh water is in short supply. Qatar would be a double beneficiary because the emirate also lacks the right sort of low-salt sand for making cement.

"In Qatar, sand has to be imported for cement," says Mr Scholten. "If they can use a local product instead of cement, it's a huge gain."

There is just one problem: sulphur concrete softens and melts at 120°C, making it insufficiently fire-resistant for use in most buildings.

That means energy companies face a big challenge to convince construction firms to try the new product, even for specific applications such as water works. That is why Shell researchers are putting moulded sulphur-concrete blocks through a battery of tests at the research centre to determine the product's limitations and optimise its strengths.

"These are intrinsically conservative industries," Egbert Veldman, the head of Shell Sulphur Solutions, says of construction companies and other potential users of new sulphur-enhanced materials. "They need very significant proof and trials before agreeing to use new products."

Another new material that Shell is field-testing in Qatar, with the aim of getting it certified there for road construction, is sulphur asphalt. Laboratory tests suggest the product is more resistant to rutting, especially in very hot or cold climates. This should make sulphur asphalt a premium road-building material in the Middle East and the continental interiors of Asia and North America.

Shell is therefore also testing sulphur-reinforced asphalt in Canada and China.

But construction companies are likely to adopt the new product only if it is cheap. That depends on sulphur prices staying low.

Rising prices may not become a barrier for some time, however. Already, the major sour-gas producers Canada and Kazakhstan have accumulated yellow mountains of stacked sulphur blocks that are visible from passing aircraft. Abu Dhabi may soon follow when it starts producing large amounts of sulphur as a by-product of gas production at the US$10 billion (Dh36.73bn) Shah project, which will exploit "ultra-sour" gas.

Qatar's main gas deposits in the North Field contain much lower hydrogen sulphide concentrations than Shah, but the amount of gas being produced and processed from the North Field is so large that Qatar, too, could soon accumulate substantial excess sulphur.

Analysts expect annual global sulphur production to exceed 62 million tonnes in 2015, up from 47 million tonnes in 2007.

Sulphur is currently mainly used to make sulphuric acid and fertiliser.

In addition to building materials, Shell has developed a sulphur-enhanced fertiliser that makes the growth-assisting element more accessible to plants. Trials carried out by the company suggest crop yields in potential markets such as China could be increased by as much as 14 per cent.

Sulphur is the fourth-most important mineral plant nutrient, after nitrogen, phosphorus and potassium.

tcarlisle@thenational.ae