Water Holding Capacities of Fly Ashes: Effect of Size Fractionation

Abstract

Water holding capacities of fly ashes from different thermal power plants in Eastern India have been compared. Moreover, the effect of size fractionation (sieving) on the water holding capacities has also been determined. The desorption rate of water held by the fly ash fractions at ambient temperature (25–30°C) has been investigated. The effect of mixing various size fractions of fly ash in increasing the water holding capacities of fly ash has been studied. It is observed that the fly ash obtained from a thermal power plant working on stoker-fired combustor has the highest water holding capacity, followed by the one that works on pulverized fuel combustor. Fly ash collected from super thermal power plant has the least water holding capacity (40.7%). The coarser size fractions of fly ashes in general have higher water holding capacities than the finer ones. An attempt has been made to correlate the results obtained, with the potential use in agriculture.

Keywords:

• desorption
• fly ashes
• pulverized fuel combustor
• sieving
• stoker fired combustor
• super thermal power plant
• water holding capacities

Notes

^a Fixing of low/high values is arbitrary. To demarcate the higher WHC for the same ash/fraction, a difference of 4% has been fixed for low/high value.

F = fraction retained by Sieve No. B.S 80 (i.e., +192 μm); and G = fraction passed through Sieve No. B.S 80 and retained by Sieve No. B.S 150 (i.e., −192 μm to +104 μm).

D₁₀: 10% of the particles is smaller than this diameter (μm); D₅₀: 50% of the particles is smaller than this diameter (μm); D₉₀: 90% of the particles is smaller than this diameter (μm); and AMD: arithmetic mean diameter.

Average WHC (%) of soil: Yellow soil, 51.65%; brown soil: 58.94%.