Fly ash is a fine powdery material, generated due to combustion of pulverized coal in thermal power plants. It is passed through an electrostatic precipitator (ESP) and different size fractions are collected in different hoppers. Each of these size fractions have unique granulometry, different mineral phases and glass content. In practice, all these size fractions are blended together before storage or disposal, so that if it is taken by some users such as cement or bricks, all size fractions get utilized. In many cases, fly ash is classified again to different size fractions so that the advantageous properties of finer size can be utilized. However, if the different size fractions from ESP can be collected separately, you have size graded fly ash for different applications. We have prepared a holistic scheme for the fly ash utilization as shown in figure. You can see that the fine size fraction can have high value added application whereas the coarse fraction can be milled or mechanically activated and have the properties similar or better than fine fly ash. Thus we should adopt the practice of collecting different size fractions of fly ash.
wasting fly ash