A few years ago I read an article about the problem of recyling plastics because of the incompatibility of the different plastics found in the waste stream. It was suggested that we could use plastics for fuel by grinding them up and blowing them into the furnaces of coal-fired power plants. It seemed to me to be a good idea, as plastics are mostly nothing but polymerized petroleum anyway. Has this idea gone anywhere?
Well, not really. Plastics are still very much a “niche” fuel, for the following reasons:
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There is often not enough quantity of plastics that can be easily delivered on-site to actually justify doing it.
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Many plastics contain toxics which would require serious modifications to the power plant for installing monitoring equipment and upgrading pollution control equipment. HCl emissions are also a serious problem when burning plastics, something coal plants don’t normally have a problem with, and thus they typically don’t have the ability to remove it (unless they have a wet Flue Gas Desulfurization system, which does a decent job of removing the HCl).
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A large number of coal power plants either make money by selling their ash for conrete, or get their ash hauled away at no charge for concrete or soil stabilization. When you burn plastics, they contaminate the ash such that it becomes unsaleable.
CQ Inc developed a pellet of coal mixed with paper sludge and plastic which they marketed as “E-Fuel[sup]TM[/sup]”, and Duquesne Energy tried burning this for a while on an experimental basis.
An interesting plastic niche is what is known as “Autmobile Fluff” or Autobile Shredder Residue (ASR). This is composed of the plastics, foam rubber, and fabrics from crushed and recycled cars which are removed prior to wrecking and melting the metal. Roughly 10-12 million motor vehicles are scrapped each year, and it is estimated that the 200 or so shredding facilities generate between 2.5 to 3.0 million tons per year of fluff or ASR.
Currently, the only place in the world burning ASR is a car manufacturer in Japan, which burns it in combination with coal to provide electriciy and process steam for their plant. The properties of typical fluff and ASR are:
Heating value - from 9200 to 2900 Btu/lbm (not bad until you get less than 6000 or so)
Ash: from 72 to 25% (YIPE!)
Sulfur: from 0.5 to 0.2 % (pretty low)
Chlorine - from 16.9 to 0.7 % (YIPE! Holy waterwall corrosion, Batgirl!)
Hope this helps.
Una
This may be the article you read: American Scientist, July-August 1998. Only an abstract is available online, as far as I can tell, abstract here
A review of the article is here.
If I am not mistaken, burning plastics is already common in the Netherlands and Japan.
Burning plastics creates some extremely poisonous gasses. I do not think this is a good idea.
Wow, two posts in two days I can actually talk intelligently about. How about 3/3? 