What is FLY ASH ?

 
  • FLY ASH: THE MODERN POZZOLAN
    Power plants fueled by coal produce more than half of the electricity we consume in the India today. But in addition to electricity, these plants produce a material that is fast becoming a vital ingredient for improving the performance of a wide range of concrete products.
    That material is Fly ash.

  • Fly ash is comprised of the non combustible mineral portion of coal. When coal is consumed in a power plant, it is first ground to the fineness of powder. Blown into the power plant’s boiler, the carbon is consumed—leaving molten particles rich in silica, alumina & calcium. These particles solidify as microscopic, glassy spheres that are collected from the power plant’s exhaust before they can “fly” away---hence the product’s name: Fly Ash.

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Several new and important technologies are being commercialized in the areas of fly ash beneficiation and utilization to bring fly ash into conformance with current  ASTM,IS & other world standard specifications for use in concrete. As the fly ash utilization industry has matured, quality control, quality assurance, and improved product performance have increasingly become important. Technologies have been commercialized to improve and assure fly ash quality for conventional concrete applications.Also, fly ash utilization technologies have been developed to produce high performance concrete products.
Changes in boiler operations or alteration of air emissions control systems at power plants will alter the quality of fly ash produced. Factors that may impact fly ash quality in this way include:
  • A reduction in the pozzolanic reactivity caused by increased proportion of coarse particles.
  • The presence in the fly ash of excessive unburned carbon (UBC)
  • Chemical residuals from post-combustion emission control
There are two standard processes to achieve consistent PARTICLE SIZE CONTROL.
  1. Screening: - In mineral processing, it is common practice to use screens to remove coarse particles from powdered products. In general, dry screening of powders is not economically feasible at below 45 micron (325 screen mesh size).Typical fly ash has a large proportion of the particles (typically more than 50 percent) finer than 45 micron. The use of coarse screens (100 or 80 mesh), might be effective for the removal of most of the coarse particles, many of which comprise UBC.The ability to remove carbon by this method depends on the degree to which the carbon-rich particles are discrete (liberated), and the size and shape of the carbon particles. As such, screening may be effective as part of a general ash processing scheme to reduce coarse particle content, reduce carbon content, reduce variability and improve concrete workability.
  2. Air classification:-Classification systems that use air to separate particles by size and weight are also used to retain the finer ash proportion. Air classification may be performed on ash for the removal of coarse particles or the selective concentration of fine particles. By using air classification system separation of fine particles from coarse particles is achieved very efficiently, & it is a practically & economically viable solution.
  Thus, we have selected air classification system for processing classified Fly ash, by the name “Techpozzo”.
 

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