Utilization of Flue Gas Conditioned Fly Ashes in Cement and Construction Industries

Abstract

Fly ash is a waste generated from coal based boilers and has been used in various civil engineering
applications. The pozzolanic activity of the fly ash plays a major role in its utilization. The ageing of the
electrostatic precipitators (ESPs), variation in coal and ash properties results in higher suspended
particulate matter (SPM) emissions. Globally the SPM limits are being reduced, flue gas conditioning
(FGC), i.e. dosing of ammonia and sulphur trioxide to the flue gas alters the fly ash properties and increases
the collection efficiency of ESPs. There is a concern that due to chemicals dosed in the flue gases, there
could be an adverse effect on fly ash and its utilization. This paper presents the investigations on pozzolanic
activity (as per ASTM specification) of the conditioned fly ash samples collected from the coal based thermal
power stations in India, to conform its suitability for utilization. The pozzolanic activity and strength activity
index of ammonia dosed fly ash samples were compared with undosed fly ash samples and found no change
in the pozzolanic characteristics. Hence, the conditioned fly ash is suitable for its utilization in cement and
other civil engineering applications.
Keywords: Suspended particulate matter, Flue gas conditioning, Fly ash characterization, Utilization