Investigation of cracks and damages at the bends of soot blower tubes

At the SASOL power generating station in Secunda, South Africa, the ash producing fuels used to fire the boilers cause build-up of combustion by-products on the surfaces of the boiler, including soot, ash and slag on the walls of the economisers, re-heaters and super-heaters. The need to clean up those by-products is identified and the equipment used to reduce this effect at SASOL is the soot blower. During the operation of the equipment, it is realized that the tubes of the soot blowers develop cracks that hinders their function. This paper investigates the causes of cracks and damages at the bends of Soot Blower tubes. A Computational Fluid Dynamics model of the lance tube is presented in this the paper. The section of the tube where the steam and flue gases pass were modelled to obtain detailed distributions. The results of temperature and pressure distributions on the lance tube body is presented. Actual temperature and pressure ranges of the boiler were kept at 800-1000 degrees Celsius and 800-1000 kPa respectively. The results revealed high temperature at the tip of the lance tube near the nozzle. The intrusion of flue gases results in harmful chemical reactions that cause corrosion to the tubes.