Conceptual design of a cane white sugar factory offering maximum cogeneration

The increasing market demand for white sugar of high quality has led to the development of microfiltration and other techniques enabling the juice purification and sugar crystallization processes in cane sugar factories to be greatly simplified. When these techniques are applied together with high-pressure steam generators and condensing-extraction turbogenerators, wholly electrified drives and single-line continuous process stations, the resultant white sugar factory can save at least 40% of the available bagasse during a 150 day crop, while still exporting approx. 35 kWh of electrical power per t of cane. The excess amount of bagasse can be baled during the crop and be employed for firing the power station during the off-season, generating an additional 77 kWh/t electrical power. In total, approx. 112 kWh/t of cane can be generated for export to the grid on a year-round basis, without employing any additional fuel or sophisticated methods like bagasse gasification.

The paper shows the conceptual design of such a factory, including an overall layout, summary tables and schematics of the mass and heat balances, short description of the main process features and cost estimate for a plant of 24,000 t/d capacity. At current world market white sugar prices and assuming US$40 net revenue per MWh exported, the amount of export power generated will add approx 11% to the annual revenue of the factory due to sales of sugar and molasses. In a number of cane sugar producing countries this could be an attractive proposition.