Hot Corrosion Phenomenon in Super Heater Tubes & Its Impact on Life of Super Heater in Thermal Power Plants

Ashok Kumar Goyal; Dr. Sanjeev Mishra

Volume : IV, Issue : V, May - 2015

Hot Corrosion Phenomenon in Super Heater Tubes & Its Impact on Life of Super Heater in Thermal Power Plants

Ashok Kumar Goyal, Dr. Sanjeev Mishra

Abstract :

Power is the basic need of every country in development is based on the power production capacity; un–interrupted power supply is needed for various industrial processes in order to maintain the production up to optimum level. Shut down of a power plant due to failure of any component may cause a great loss of power as well as revenue; Corrosion is an unavoidable and major constraint in the effective operation of boiler of a thermal power plant. Corrosion phenomenon is a most negative parameter and by having an effective control on the formation of rust, the effectiveness of power plant can be improved significantly. Corrosion generally is defined as the process by which metals return to the form in which they occur in nature. It is due to chemicals reaction between the metal of tube & water impurities or fuel gas product at low temp, (ambient temp.) or high temperature. Here Indian coal is a complex and relatively dirty fuel that contains varying amount of sulfur commonly called ash. The coal used in Indian power stations has large amount of ash (about 50%), Due to presence of some corrosive element like sulfur in the flue gases at high temperature present in the tube material undergo sulfidation which results in the formation of sulfide/sulfate. Vanadium compounds also in the flue gases undergo fluxing reaction with oxide and/or sulfate scales on metal causing hot corrosion, and the hot corrosion can cause the rupture of the tubes. This phenomenon is usually noted on fire side of boiler tubes particularly in high temperature areas like super heater tubes, re heater tubes etc., this paper includes the case study of failure of super heater boiler tubes and study conducted, relevant data, observations, analysis, and recommendations pertaining to the tube failure, It is well established that an innovative approach to life extension through conduct various tests during the plant shut down is potential alternative to improve the overall productivity of any thermal power plant at a negligible investment. These alternatives are increasingly getting importance in developed as well as developing countries, not only because of their inherent advantages for taking steps for extending life, replacement and preventing premature failure of aged components due to corrosion, but also for optimizing the maintenance schedule. Objective of this paper is to assess the hot corrosion in super heater tubes of boiler and to locate the failure point due to hot corrosion so that action plans for next five years may be proposed. Based on the visual observations, non–destructive test results, destructive test results and their analysis, recommendations are made to run the plant at rated capacity provided these are implemented and plant is operated as per design operating regime. This study is based on the observation taken at the site during, shut down and inspection and identify the problems associated with hot corrosion in super heater tubes of boiler of unit # 4 of kota super thermal power station.