Methods to improve fly ash quality in Lakvijaya power station

Abstract

Fly ash is a byproduct of coal fired power generation which may cause environmental and social problems. Lakvijaya power station which is the largest power station in Sri Lanka is facing problems with fly ash dumping. Dumping of fly ash inside the power plant premises has created environmental and social issues. These issues have caused to arise objections from the society against developing new coal fired power plants in Sri Lanka. Fly ash can be sold to the cement manufactures for productive use without dumping at the power station premises. Though cement manufactures need the Loss of Ignition (LoI) value of fly ash to be less than 5% it is often higher in the Lakvijaya power station. It is observed that reducing the load gives better fly ash quality but, it has an impact on economical dispatchof power plants in the system. Therefore, the study focused on the methods to reduce fly ash LoI level by analyzing boiler operating parameters. Nine boiler related parameters were identified that would have impact on fly ash LoI level. Data were extracted from unit 1 boiler of Lakvijaya power station for one month. Factor analysis and multiple linear regression methods were used to analyze data. Factor analysis is used to identify correlated variables and suitable adjustments were made prior to conduct of multiple regression analysis. Regression model of the system was used to identify the impact of each parameter on the fly ash LoIlevel. The results show that total air flow and primary air pressure are not sufficient for the complete combustion at the higher coal rates so that, capacity enhancements for those systems are recommended. Further, boiler operators should be advised to maintain highest possible set points for primary air temperature and secondary air pressure which will contribute to reduce the LoI level in fly ash.