Clean burn from Ohio

Ohio University engineers have developed technology that cleans pollutants from the exhaust of coal-fired power plants and other industrial smokestacks more efficiently and cheaply than before.

The equipment – called the membrane electrostatic precipitator – could help industries meet forthcoming US Environmental Protection Agency emissions regulations, but could make Ohio’s high-sulphur coal a more viable energy source, said Hajrudin Pasic, professor of mechanical engineering and lead researcher on the project.

Pasic and other engineering researchers in the Russ College of Engineering and Technology developed the new technology, a more efficient version of an electrostatic precipitator device that’s been in use for about 100 years.

Their design uses 1 to 3 millimetre-thick membranes woven from carbon, silicon and similar fibre-based materials to capture fine air pollutants and toxic heavy metals.

This is an improvement over the conventional models, which use heavy, expensive steel plates to attract dust particles, said Pasic.

When coal is burned for fuel, it produces exhaust thick with fly ash, which contains trace metals such as arsenic. As the fly ash moves through the power plant’s exhaust system, the newly designed membrane electrostatic precipitator collects the particles before they can be released into the air via the smokestack.

The membranes are not only more efficient than the steel plates, Pasic said, but are less expensive, not susceptible to corrosion and 10 to 20 times lighter.

Existing electrostatic precipitators, which range in size depending on the power plant, can be retrofitted with the membranes. And while the process used to clean the steel plates in conventional precipitators – a hammer strikes the metal to loosen the ash – actually sends the pollutant back into the air, the membranes in the revamped device can be washed with water.

The carbon or silicon materials comprising the membrane are commonly used in civil or aerospace engineering for such applications as reinforcement of concrete structures or construction of light aeroplanes.

The Ohio University engineers now are exploring ways to enhance the membrane to improve its performance and to allow it to capture a variety of pollutants.

The invention is aimed at making it more feasible for coal-fired power plants to use high-sulphur Ohio coal, which many US plants have been unable to burn since passage of the 1990 Clean Air Act Amendments.

But the device could have a much wider application, Pasic said, as any industry that emits fine air pollutants or trace heavy metals could use it.

Research on the device is set to continue, with the team now examining how it could capture mercury from industrial emissions.

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