Human settlements

Renewable energy

Biomass 08: Bulk bagasse dewatering station at Racecourse Mill

Renewable Energy Commercialisation in Australia, Australian Greenhouse Office, 2003
NOTE: The status of these projects will have changed since the time of publication, and project contacts may also have changed.

Mackay Sugar is installing a dewatering station that will increase the efficiency of the conversion of bagasse to renewable electricity.

Under the Renewable Energy Commercialisation Program, Mackay Sugar Cooperative has received a $1 million grant towards the installation of a bagasse 'dewatering' station that will reduce the moisture content of bagasse fuel.

All Australian sugar mills produce vast quantities of bagasse, the fibrous residue remaining after cane is crushed and the juice processed to form sugar. Bagasse contains more than 50 per cent water and is an excellent but moist renewable fuel for firing in sugar factory boilers.

High-pressure steam raised in the boilers is used to generate electricity (for factory motors) and drive machinery in the crushing train, while the turbine exhaust steam is used for juice heating and sugar processing. Typically, some surplus electricity is dispatched to the local electricity grid, but this has been limited by the low energy efficiency of the plant installed in most sugar factories.

As a result of this project, Mackay Sugar will be a partner in the installation of a de-watering station at Harwood Mill in Northern NSW. By reducing the moisture content of bagasse, boiler efficiency at Harwood will be greatly improved, resulting in excess bagasse being available for storage for off-season energy needs. At other factories, this technology will result in enhanced levels of electricity exported to the grid.

The technology for efficient sugar mill cogeneration is well established; however, the handling and storage of large quantities of bagasse year-round is unproven in Australia. Studies have shown that due to the relatively high price received for energy in the off-season, the economics of cogeneration are considerably improved if fuel can be saved and stored for year-round electricity generation.

It is intended that the development of technologies in this dewatering station program will result in the more efficient utilisation of bagasse being stored uncovered at mills each year and exposed to tropical downpours. The station at Harwood Mill will reduce the bagasse moisture to below 50 per cent, thus improving boiler and sugar recovery efficiencies and enhancing returns to the mill. The efficiency gains in bagasse utilisation may also result in the generation of surplus bagasse for use in the off-season.

In the subsequent cogeneration project planned for Mackay Sugar based on this technology, electricity despatched to the grid will be about 30MW during the crushing season and 13MW during the off-season. The 160GWh per year of renewable electricity generation will save approximately 152,000 tonnes of CO2 emissions each year, and a further 122,000 tonnes of CO2 will be saved due to coal displacement on site.

The dewatering station technology could be applied to any Australian sugar factory. The sugar industry is well placed to supply to the renewable electricity market, recently promoted by the Renewable Energy (Electricity) Act. To fully capitalise on this opportunity, the industry needs to address the problem of fuel supply and storage. If successful, this trial of dewatering technology will provide a solution.

For more information please contact

John Hodgson
Senior Project Engineer
Mackay Sugar Cooperative Association Ltd
Racecourse Mill
Mackay QLD 4741
Tel (07) 4953 8280
Fax (07) 4953 8342
Email j.hodgson@sri.org.au
Internet www.mkysugar.com.au

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