The Problem of Fire Ironed Out
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A. It has been quite a while since man discovered fire. But it is only recently that he has learnt enough chemistry to think of improving it. Take fossil fuels, such as coal and oil, for example. They give off plenty of heat when they burn; unfortunately, they give off plenty of other things as well, including the particles that make up smog and soot, the carbon dioxide responsible for the greenhouse effect and the oxides of nitrogen and sulphur that help to make acid rain. A new fuel additive called Carbonex seems drastically to reduce emissions of particles and of nitrogen oxides. It may thus help to solve half the problems.
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B. To understand the solution, take a closer look at the problem. Fossil fuels are mostly made of carbon, which reacts with oxygen to produce carbon dioxide (in the case of coal) or carbon dioxide and water (in the case of petrol, diesel fuel and other refined oils). The combustion of fossil fuels is never quite complete. Small, unbumt particles of fuel always escape, often as black smoke. These particles contain cancer-causing chemicals and are ever more unpopular.
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C. There is a standard fix for this. To reduce the problem of incomplete burning, combustion chambers are routinely flooded with about 25% more air than they need to burn their fuel. The idea is to give the flame more oxygen and hence, increase the efficiency of burning. But there is a snag. Dry air is 21% oxygen and 78% nitrogen. Nitrogen, like carbon, reacts with oxygen at high temperature — in this case producing the nitrogen oxides (NOX) that help cause acid rain. When extra air is added to a combustion chamber, emissions of soot and smog go down but NOX emissions go up.
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D. Carbonex, invented by an academic chemist, Dr. David Farrar, at the University of Toronto, and developed by Velino Ventures of Toronto, tries to alleviate this. The active ingredient is a hydrocarbon molecule to which an iron atom is bound. The molecule acts as a carrier for the iron, letting it dissolve in organic liquids like oil and petrol. When sprayed into a flame at the same time as a carbon-based fuel, Carbonex makes it bum more efficiently. The result is fewer particles and less need for extra air.
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E. It seems to work at two points during burning. If Carbonex is sprayed into a stream of fuel entering a flame in a combustion chamber, it coats the fuel and deposits iron atoms on the surface of the fuel particles. As the particles enter the outer part of the flame, which is cooler than the core, the more volatile components in the fuel vaporize. The faster these vapours leave the fuel, the sooner oxygen can get to the surface of the fuel particle and react with the carbon. Carbonex appears to speed up the exodus. Fuel particles that survive the hot core of the flame contain several large and unhealthy molecules that do not bum well without a fuel additive. Carbonex also seems to lower the temperature at which these compounds bum, allowing them to disintegrate even while the fuel particle is cooling.
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F. Iron is not the only substance that can manage this trick; any metal should do. Barium, magnesium, manganese, cobalt, nickel and lead have all been tried as fuel additives, but all are toxic and so in disfavour. Iron was picked for Carbonex because it is non-toxic and very effective even in small doses.
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G. Over the past two years, Carbonex has been tested by an independent research group at the Battelle Memorial Institute in Columbus, Ohio. The researchers found that it reduced emissions of particles from diesel engines by 43% and increased the yield of energy from combustion by 1.5-3%. When tested in a light-fuel-oil industrial burner in Geneva, it cut emissions of particles by 67%; added to a coarsely ground bituminous coal it reduced NOX emissions by 25%. In addition to reducing NOX and virtually eliminating black smoke, Carbonex cut the amount of soot left behind in combustion chambers, and so made maintenance cheaper. The fuel additive paid for itself in increased energy efficiency.
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H. Although Carbonex could be used in petrol for cars, Dr. Farrar thinks petrol is already refined enough to make it unnecessary. The real need for his invention, he thinks, is in plants that bum coal and less refined oils such as furnace and bunker oil. Farewell to those dark satanic mills.