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Fuel-efficient furnace helps reduce acid rain.

Fuel-Efficient Furance Helps Reduce Acid Rain

As a step in the fight to stop acid rain, one Canadian researcher has revived an old coal-burning system and adapted it so that it |virtually eliminates' sulphur emissions (a main component of acid rain).

Henry Becker, FCIC, a chemical engineering professor at Queen's University (Kingston, Ont.), simultaneously tumbles and burns pulverized coal and limestone in order to |capture' the sulphur gases from the burning coal before they go up to the smokestack.

The technology he uses, called |atmospheric fluidized bed combustion' (AFBC), is also very fuel-efficient. An AFBC furnace is usually a steel cylinder with a porous metal |plate' mounted horizontally inside it. On the plate is a |bed' of sand or other particulate material. From below, air is blown at high velocity through the plate while pulverized fuel is fed into the furnace and burned above. Becker describes the process as "being caught in a tornado" while burning at very high temperatures - about 900 degrees C. This process maximizes the heat obtained from every ton of pulverized fuel.

But, even with a fuel-efficient AFBC, the sulphur gases go out the smokestack as pollution, so Becker introduced the limestone.

The sulphur dioxide given off by the burning coal reacts with the calcium oxide given off by the burning limestone. Taking oxygen from the air, the substances combine to produce gypsum - ordinary household plaster.

Potential uses for this plaster - as roadbed, landfill or building material - are included in a waste disposal research project by the federal department of Energy, Mines and Resources, says Becker.

However, Becker points out a disadvantage of the technology. Beneficial as it may be in terms of energy shortages and acid rain, it will ultimately add to the world-wide |greenhouse effect' because it gives off carbon dioxide.

"A halfway measure would be to burn natural gas and coal in equal proportions", he adds. "That would reduce the (carbon dioxide) emissions by 50 per cent. But we're going to have to get away from coal altogether."

The Queen's AFBC project began during the energy scare of the later 1970s, when research focused fuel efficiency and finding new sources of fuel.

In a decade of research, Becker has exhaustively surveyed the firing (burning) properties and problems of all Canadian coals, including minto coal from New Brunswick, bituminous coal from Nova Scotia and anthracite from British Columbia.

He has also experimented with the waste products of oil refineries - the all-but-worthless |syncrude' coke waste from refined tar sands, and petroleum coke.

Other alternative fuels that have been well researched especially by the Swedes, are garbage and wood wastes (bark, sawdust and wood shavings) and they already have commercial possibilities, he says.
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Title Annotation:News Briefs; coal-burning furnace which eliminates sulphur emissions
Publication:Canadian Chemical News
Date:Feb 1, 1991
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