Enhancement of Collection Efficiencies of Electrostatic Precipitators: Indian Experiments

Abstract

With the rising oil price, coal is well positioned to make a valuable contribution to global energy security. The market share of coal in electricity generation in developing countries is around 45% at present and is expected to rise up to 47% in 2030. A significant amount of power generation in countries like China, India, USA, Russia, East Europe, South Africa and Australia is based on coal. At present India has got 61175 MW (58% of total installed power capacities) installed coal based power capacity which is expected to rise 115500 MW (53%) by the year 2012. Fly ash emitted by the coal based power plants is serious air pollutants in and around the power plant compared to SO x and NO x air pollutants in India. Electrostatic Precipitators are used to control fly ash emitting from the boilers of most the power plants in India. The coal burnt in most of the power plants in India are perhaps are among the most difficult ones in the world, which are characterized by low calorific value 3500 kcal/kg-4500 kcal/kg, and high ash contents 35%-45%. Besides, ashes have got large electrical resitivities because of low alkali and sulfur. As a result the size of ESPs in India is much larger compared to other places for similar electric out put. In order to meet the more stringent emissions standards several methods have been adopted in many old power plants with aged ESPs. These methods include: (i) enhancement of collection area of ESPs; (ii) Pulse and intermittent charging of ESP units; (iii) Flue gas conditioning by water fogging, ammonia conditioning; (iv) Dual conditioning with NH 3 and SO 3 , and; (v) Coal ash conditioning with sodium salt. These methods have got their respective advantages and disadvantages and have met partial success. The present paper discusses some of the points for some of the selected plants.