Electrostatic Precipitator Performance in Indian Pulverized Coal Based Thermal Power Stations - Problems and Solutions

Coal used in Indian thermal power stations is of inferior grade having low heat value and high ash content due to drift origin. However, Indian power coal ash is specially known by its refractory in nature and low sulphur (below 0.5%) and alkalis (less than 1.5%) contents. Due to presence of low sulphur and alkalis and consequently having very high ash resistivity (10 – 10 O cm) it is difficult to achieve good E.S.P. performance. Majority of Indian thermal power stations have E.S.P. for ash collection. In the present paper various attempts have been made to analyze the causes of problems in terms of the chemical constituents of ash, resistivity, conductivity, etc. A special emphasis was given to correlate the different forms of sulphur (organic, pyretic and sulphate sulphur) on E.S.P. performance. The total sulphur can not predict the E.S.P. performance; it is the forms of sulphur that decides the performance. Organic sulphur in coal mainly improves the ash resistivity through SO3 adsorption from flue gas whereas pyretic sulphur is responsible for slag and clinker formation in the boiler and evacuated through bottom hoper as bottom ash in dry bottom furnace. In addition, the paper deals with the concept of predicting ash resistivity based on conductivity measurement of ash extract which may help to take necessary action for improvements of E.S.P. performance in thermal power stations. The paper also discusses the remedial measures to be taken in terms of use of additive (sodium / sulphur based) or biomass like horticultural waste having high alkalis (4 – 6 %) for blending in appropriate proportion with coal depending on characteristics. * Corresponding Author