| Abstract | Elemental compositions of milled-coal, bottom and fly ash, and stack flue gas were determined in order to assess the amounts of elements of environmental concern emitted from the stack at Unit No. 5,
Battle River coal-fired power station in central Alberta. The species of arsenic (As+3,+5), chromium (Cr+3,+6) and nickel (Ni0,+2) in coal and ash, and stack-emitted polyaromatic hydrocarbons were also determined. The study indicates that, at 0.05
tonnes/year, emissions of hazardous air pollutants, such as arsenic, cadmium, mercury, lead, and selenium, are low. The total emissions of other elements (Be, Ba, Co, Cr, Cu, Mn, Mo, Ni and V) are 1.0 tonnes/year, much less than the legislated total
emission level of 25 tonnes/year for all these elements, or 10 tonnes/year for any individual element. Radionuclide (thorium and uranium) emissions are 17 kg/year. The activity of the 235U series is below the detection limit for all samples analyzed.
The emissions of polyaromatic hydrocarbons (PAHs) are low. Three PAHs (phenanthrene, fluoranthrene, and pyrene) were detected at low concentrations in stack gas. Fly ash is ferrocalcsialic and contains both nonmetallic and metallic microspheres and
angular feldspar fragments. Fly ash collected from the inlet and hopper of the electrostatic precipitators contains plerospheres (spheres in spheres). There are no plerospheres in the particles emitted from the stack, indicating that some of the
microspheres are retained within the power plant.
Elements removed by ammonium acetate from milled coal are limited to As, Ba, Be, Co, Mn and Na, indicating that they are associated with exchangeable sites in an organic fraction, carboxylic group
(as chelate) and carbonates. Most elements in milled coal are leached by HCl. The ion-exchangeable elements in bottom ash and fly ash consist of Ba, Be, Co, Cr, Cu, Mn, Na, and Ni. All elements are leached by HCl from bottom and fly ashes, and most
of the elements have their highest leachate in this stage. The study on the speciation of elements suggests that arsenic in milled coal is present as arsenical pyrite (As+3) and is associated with coal macerals. Arsenic in bottom and fly ashes
predominantly consists of less toxic As+5 (arsenate) species. Chromium and nickel in milled coal, bottom and fly-ash samples are present predominantly as Cr+3 that is essential to health, and nontoxic Ni+2 in co-ordination with oxygen. |