Online measurement and control of pulverized coal fineness in supercritical power plants

The fineness of pulverized coal in the coal-fired thermal power plants greatly affects the stability of the produced fire and its combustion efficiency. Presently, the coal fineness in Indian power plants is measured offline and requires a minimum of 4–6 hours for manual collection of samples and laboratory analysis. Mostly, the delayed offline results of coal fineness are not effectively useful to plant operators, as the plant running conditions are transient with load and may change considerably with time. In the present work, a prototype is made, and an experimental study is performed for the online measurement of coal fineness using an automated mechanical sieving method. For comparison, offline measurement using the conventional ASTM D197–87 laboratory method is also performed. The maximum deviation between the online and offline results is within ±1.5%. A DCS logic for coal fineness control is proposed. After implementing this system, the unburned carbons in the bottom and fly ash decreased to 2.36% from 2.67% and to 0.44% from 0.59%, respectively, while the boiler efficiency increased to 86.61% from 86.42%. The industrial application of the developed novel system can enhance the plant performance by optimizing coal combustion, reducing unburned carbon losses, and increasing boiler efficiency.