Investigations on Fly Ash Resistivity: Development of Empirical Relations Based on Experimental Measurement A. Chandra, Sanjeev Kumar, Subodh Kumar and P.k. Sharma

Fly ash resistivity is a single parameter which has got significant impact over sizing and performance of Electrostatic Precipitator (ESP) in coal based thermal power plants. A fly ash resistivity measurement facility has been set up at IIT Delhi with the support of National Energy Technology Laboratory (NETL), USA and USAID-India. The fly ash samples from different power plant are being collected by CenPEEP, NTPC and supplied to IIT Delhi for measurements. The experiments were conducted for the measurements of electrical resistivity over a wide range of temperatures (90-455) C as per IEEE standards. Around 250 samples obtained from different power plants in India, have been tested. Empirical relations developed by Bickelhaupt, which are based on the chemical composition of fly ash for calculating the electrical resistivity are used to calculate as theoretical value for given experimental conditions. Comparisons between fly ash resistivity obtained from experiments and theoretical values show significant differences between the two values especially at low temperatures (90-160 C), where surface conduction is important. This is due to the different chemical compositions of ash/fly ash obtained from the coals used in power plants in India and USA. New empirical relations based on chemical compositions, generated in typical Indian power plants have been developed to calculate electrical resistivity at the temperature and moisture corresponding to actual conditions to ESP. These relations provide better agreements with experimental values.