Estimation of Fly ASH Availability in a Thermal Power Plant for Cement Manufacturers

Abstract

The Indian coals are having 25 to 45% ash content and huge quantity of fly ash is being generated every day in the Indianthermal power plants. The fly ash so generated are being disposed by dry or wet mode from the power plant. The fly ashdisposed in dry mode is lifted by the cement manufacturers and the fly ash disposed in wet mode is unattended. Mostof the quantity of fly ash is collected in the ESPs. The particle size of fly ash collected in ESPs is finer compared to the flyash collected in other parts of the power plant. For this reason the cement manufacturers prefer the fly ash from ESPs.The quantity of fly ash collected in the ESPs is not directly measurable on everyday basis as there are no well proveninstrumental methods. Also the quantity of fly ash collected in ESPs fluctuates every day due to the varying load factorand coal quality. However, it is important to estimate the quantity of fly ash collected by ESPs on everyday basis so thatthe proportion of fly ash lifted by the cement manufacturers and the fly ash sent to the ash pond will be known. Presentlypower plants do not have a method to estimate the exact availability of fly ash and it is being theoretically calculated fromthe design value that the 80% of the total ash is fly ash and in that a fixed proportion (about 70% of total fly ash generated)is collected in the ESPs. However, the actual generation of fly ash would be different and this is influenced by the type ofcoal used, fineness of the input coal particles, boiler operating conditions, load factor, age of the power plant, etc. Thisuncertainty leads to disputes between cement manufacturers and the utility if there is a penalty clause in the agreementfor not completely lifting the available fly ash (as theoretically calculated by the utility). In view of this it is imperative toformulate acceptable methods for determining the actual quantity of fly ash collected in the ESPs on daily basis. In thepresent work, a simple methodology was developed to quantity the average fly ash collected in ESPs in a 210 MWe coalfired power plant on every day basis through site measurements and routine power plant data. The amount of fly ashdisposed in dry and wet mode has also been estimated through this method.