A SIMPLE metallic filter might cure one of the oil industry鈥檚 biggest
environmental headaches by cheaply removing sulphur and heavy metals from oil.
The filter could open up huge reserves of oil in South America, China and the
former Soviet Union that have previously been far too dirty to tap.
The existing method for removing sulphur is expensive. The oil has to be
heated to 700 掳C at 70 times atmospheric pressure. The metallic filter works
at room temperature and atmospheric pressure. 鈥淚nstead of spending billions of
dollars looking for more oil, you could take what鈥檚 already there and use it,鈥�
says Roger Duffield, the entrepreneur developing the technology. He has founded
Klinair Environmental Technologies of Dublin to market the filter.
鈥淭he potential for sweetening sour oil is huge,鈥� says Roger Lane-Nott of the Centre
for Marine and Petroleum Technology, a research monitoring body funded by the
oil and gas multinationals that is helping to promote the technology.
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Sulphur in fuel cuts the effectiveness of cars鈥� catalytic converters because
it poisons the catalyst. Many countries, including those of the European Union,
are considering tougher limits on the sulphur content of fuel to curb this
problem.
The filter is based on a substance called an intermetallic鈥攁 blend of
metals combined in very precise proportions. Unlike alloys, in which the metal
atoms are distributed at random, intermetallics consist of discrete crystals,
each with a highly defined combination of atoms.
Duffield is keeping the identity of the two metals secret, but he says both
are cheap. After a mixture of the metals is heated to 500 掳C, it is fired
through a nozzle to form a fine, whitish-grey powder. This powder is then
deposited onto an inert substrate such as carbon fibre to create a granular
surface that resembles a ceramic.
Emulsions of oil and water, like those typically found in crude oil, separate
on contact with the coating because it not only adsorbs sulphur and heavy metals
but also the surfactants that maintain the emulsion. Duffield found that this
stopped the intermetallic working. But he has now discovered that a small
voltage keeps the sodium and calcium surfactants in solution. This preserves the
emulsion and allows the intermetallic to carry on extracting sulphur and metals
from the oil. The contaminants can later be washed off the filter with solvents
such as alkalis or methanol.
By altering the voltage across the intermetallic, the extraction process can
be fine-tuned to pluck out individual compounds or families of compounds.
The filter is being developed by Teh Fu Yen, a specialist in the removal of
impurities from petroleum at the University of Southern California in Los
Angeles. Yen is extremely impressed by the technology. 鈥淲hen I first took this
research on, I was amazed,鈥� he says.
A pilot version of the filter is due to be tested before the end of this year
at the Irish State Refinery Company in Cork. 鈥淧resent technologies for removing
sulphur are expensive, typically around $5 per tonne of oil treated, so
there鈥檚 a big prize if anyone can do it more cheaply,鈥� says Neasan O鈥橲hea, chief
technical adviser at the Cork refinery. 鈥淭his technology is different and looks
辫谤辞尘颈蝉颈苍驳.鈥�