Zapped crude oil flows faster through pipes -

Zapping thick crude oil with a magnetic or electric field could make it flow more smoothly through pipes. The technique, which reduces the viscosity of the liquid, could make transporting crude through cold underwater pipes easier and cheaper, researchers claim.
The cost of transporting oil is a major factor in the energy economy, although the type of oil being moved is changing. "More heavy oil is being pumped. Lighter crude is being found less and less," says Rongjia Tao, a physicist at Temple University in Philadelphia, US.
Since heavy crude is more viscous, it flows more slowly through the pipes, reducing the volume of oil that can be pumped. If it flows too slowly, oil companies try diluting it with gasoline or other solvents, or sometimes heating the oil. But those techniques can be expensive and hard to implement on ocean-based oil rigs.
Tao says the viscosity of a suspension is partly the result of the size of the suspended particles. Smaller particles create a fluid that is more viscous than large particles.
The two researchers reasoned that if they could get the small particles to clump together, or aggregate, viscosity would go down. First they tested the theory with a suspension of iron nanoparticles in silicon oil. They applied a magnetic field to the suspension, and did indeed observe a reduction in viscosity.
Ongoing effect
Tao says that the magnetic field apparently caused the iron particles to stick together into larger clumps. Once the field was turned off they continued to stick together for several hours, only gradually breaking apart.
Tao and his colleague Xiaojun Xu then decided to see what affect magnetic and electric fields would have on the viscosity of crude oil.
Crude oil can contain either paraffin, asphalt, or both. The researchers found that a magnetic field reduced the viscosity of paraffin-based crude oil by about 15% when applied at 1.33 Tesla for 50 seconds. The reduction in viscosity lasted for several hours, gradually returning to normal. Tao says the magnetic field seems to have polarised the paraffin particles, causing them to clump together in the same way as the iron particles.
The magnetic field did not work on asphalt-based crude oil, however. So Tao and Xu decided to try applying an electric field to this mixture. They applied a powerful electric field to the oil and again saw a reduction in viscosity. Tao believes the particles were similarly polarised. Whatever the process, the particles clumped together before gradually breaking apart over several hours.
Cost sensitive
Tao says that the technique could eventually be useful in oil pipelines. Powerful magnets could be positioned at regular intervals along the pipeline, or electrified grids could run on the inside.
But Ross Chow of the Alberta Research Council in Edmonton, Canada, says that the researchers had to apply large amounts of electrical energy for fairly small decreases in viscosity. He also says it is not clear whether Tao and Xu's theoretical explanation of what is happening is correct.
On the other hand, Chow says the effect seems to be real, and agrees that further research might lead to an economic way of using magnetic and electric fields in pipelines.
Journal reference: Energy Fuels (DOI: 10.1021/ef060072x)
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