REDUCING BAGASSE CONSUMPTION AT HARWOOD MILL

摘要

Bagasse is becoming increasingly valuable, both as a fuel and as a biomass source for new products. Most of the bagasse produced in a sugar factory is used by the boiler station. Typically, between 50% and 70% of the energy in the bagasse supplied to the boiler station is transferred to the steam produced; most of the remaining energy is lost as sensible and latent heat in the boiler exhaust gases. To recover heat from boiler exhaust gases and reduce the final flue gas temperature, most Australian boilers use air heaters and/or economisers. Both these heat recovery devices are major capital cost items, especially when the costs of the changes to the boiler duct work required for the installation of an air heater or economiser are taken into account. For several years, Harwood Mill has been looking at ways to reduce auxiliary fuel use and has considered options such as increasing the number of gas and air passes. During the 2005 maintenance season, Harwood Mill installed swirl inserts at the top of the air heater tubes, installed turning vanes in the air heater air inlet plenum, and replaced some plugged and leaking air heater tubes. This paper investigates the effects of these modifications and has concluded that the swirl inserts have significantly increased air heater heat transfer and have reduced bagasse consumption of the Harwood Mill boiler.