Enhanced particulate collection from power plants firing fuels giving rise to ``difficult'' fly ash

The problem of particulate emission control from PC fired power plants is exacerbated by coal having a high ash coupled with low sulfur, plus ash having a low sodium oxide and high silica and alumna content. Although bag filters are now being considered as a means of particulate control for certain power plants, the ESP has to date been the traditional control method, in spite of the large specific collection area required for an emission compliance of < 50 mg/Nm{sup 3}. This emission is now demanded by many regulatory bodies and for funding through the World Bank. While new plants are being designed to satisfy this emission, a number of existing plants, even when in satisfactory electro-mechanical condition, face difficulty in meeting compliance. The paper examines the factors relating to high precipitator emissions and presents various scenarios for their reduction by: (a) facilities size increase, (b) flyash conditioning, (c) reduction in back end temperature to reduce gas volume and particle resistivity, and (d) alternative methods of energization, e.g., pulse charging, intermittent energization and high frequency derived DC. The method of enhancement finally selected is site specific and depends on the problem faced by the plant under consideration. The impact ofmore » improved combustion on ESP performance is also reviewed and finally the use of bag filters for some retrofit applications is considered as a potential cost effective solution. The improvement methods detailed in the paper should benefit many current ESP upgrading projects and also be of assistance to IPPs considering new plant.« less