Why Do We Continue to Burn so Much Coal?
نویسنده
چکیده
Several sugar mills in southern Africa have adverse fuel balances for various reasons, and end up burning enormous amounts of coal. Some of the reasons for this are discussed, and two in particular are analysed in detail: time efficiency and imbibition. The variables that are directly related to the energy efficiency of a sugar mill are listed and their relative effects are discussed. The effect of time efficiency is evaluated, and some guidelines are provided that may help in reducing this factor. The use of a very high rate of imbibition to achieve good extraction has almost become the norm in southern Africa. In some circumstances, the cost of this practice in increased fuel consumption can outweigh the gains achieved through high extraction. A theoretical exercise has been carried out that explores the effect of changes in imbibition on extraction and on the fuel balance. Equations are derived, using historical performance figures, for the relationship between imbibition and extraction, and allowances for other effects are discussed. A hypothetical sugar mill which relies on coal to provide sufficient steam is used as the basis of calculations. These calculations compare the relative cost of reduction in extraction with a saving in coal used, and show that in certain conditions, reduction of imbibition can result in a net saving in costs.
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