Operational experience with a bagasse boiler at low firing rates using multiple fuels

Harwood's main boiler is required to operate continuously throughout the year. For 60% of the year, it operates at 29% of its maximum continuous rating. A combination of bagasse, sawdust and coal is used to provide fuel during these low steaming periods. The low steaming rate results in low fuel efficiency as evidenced by an oxygen residual in flue gas of 13%. Early experience with coal firing resulted in serious damage to the boiler in 1989. Today, coal is fired quite safely. The use of furnace gas recirculation, along with the installation of an economiser, is expected to eliminate air heater tube corrosion and improve fuel efficiency. An excess in factory high pressure steam consumption over the low-pressure steam requirement was solved mainly by correcting a construction fault in the induced draft fan.