Coal Utilization and Recyling
  • Utilization of Coal Combustion Byproducts
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    Presently, more than 80 million tons of coal combustion byproducts (CCBs) are generated in the USA alone when coal is burned or gasified and when flue gases are scrubbed of sulfur dioxide. It is believed that the electric utility industry produces about 48 million tons of fly ash, 14 million tons of bottom ash, and 6 million tons of boiler slag. In addition to the aforementioned ashes, approximately 20 million tons of flue gas desulfurization (FGD) residues are produced in the USA every year. The Federal Clean Air Act Amendments of 1990 mandate that sulfur emissions by coal-fired industry be significantly reduced by the year 2000. This mandate has started to have and will have a serious impact on Illinois coal utilization since Illinois coal tends to be high in sulfur. If Illinois coal’s share of the market is to be maintained and expanded, then it is imperative that utilization of CCBs must be found which is not only environmentally friendly but is economically benefical for coal producers and users. In my laboratory, we are conducting research in which we have found and are finding these byproducts to be excellent raw materials for brake shoe composites and table top and decorative tile composite materials.
    BRAKE SHOE PADS: Our recent research has exhibited the potential of forming high-value materials from coal combustion byproducts (CCBs), especially PCC fly ash and FBC spent bed ash particles. The scanning electron microscopy (SEM) characterization measurements, on various Illinois CCBs and Illinois flue gas desulfurization (FGD) residue (scrubber sludge), reveal that the PCC fly ash particles are highly spherical in nature, while the FBC spent bed ash particles have irregular geometrical shapes with distinct asperities. The particle size of PCC fly ash varies from 0.2 mm to 15 mm, and this variation facilitates optimal particle packing when spherical particles are combined with irregularly shaped FBC spent bed ash particles under pressure. The combination of fly ash and spent bed ash particles, with different shapes and sizes, ensures that the finer grains will pack within the interstices of the larger particles. We have successfully harnessed these characteristics into our brake composites and have designed brake materials which have superior mechanical characteristics in comparison to commerically-available, high performance brake shoe pads.
    Fly Ash Frictional Composite: SEM
    Fly Ash Frictional Composite After Friction Test: SEM
    Frictional Behavior of Bottom Ash Composite: FAST
    TO SEE THE PICTURES CLICK BELOW
    SEM PICTURE OF
    FLY ASH
    SEM PICTURE OF CARBON IN
    FLY ASH
    SEM PICTURE OF
    BOTTOM ASH
    SEM PICTURES OF FGD SCRUBBER SLUDGE
    1. Sulfate-Rich
    2. Sulfite-Rich
    STRUCTURAL COMPOSITES FROM FGD SCRUBBER SLUDGE: In my laboratory we are also converting FGD (flue gas desulfurization) residues, especially sulfate-rich and sulfite-rich scrubber sludges, into structural composite materials, e.g., decorative and sound insulating tiles, chemically inert tabletops/countertops, cultured vanity tops, and laminates. We have met with considerable success in forming these composites in which we altered the crystal growth behavior of sulfate-rich and sulfite-rich sludge so that they will grow in an interlocked configuration. We have observed that depending upon the mode of admixture of ingredients the formed composite is machineable, can be cut by an ordinary saw, can be nailed, and can be formed into different shapes. It is worthwhile to point out that our structural composite materials, depending on their end use, will have a concentration of scrubber sludge from 65% to 95% of the material’s weight.

     

     

    TO SEE THE PICTURES CLICK BELOW
    Effects of Pressure and
    Temperature on Sulfate-Rich
    Scrubber Sludge: SEM
    Pictures    		 Pictures of Composite Formed
    from Sulfate- and Sulfite-Rich
    Scrubber Sludge:
    Figure 1
    Figure 2
    Storage Modulus of FGD Sludge Composites Picture of Composites formed
    from Sulfate and Sulfite
    Scrubber Sludges: 3
    Flexural Strength of FGD Sludge
    Composite
    Picture of Composites formed
    from Sulfate and Sulfite
    Scrubber Sludges: 4
     
    Picture of Composites formed
    from Sulfate and Sulfite
    Scrubber Sludges: 5

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