Sugar mill boilers generate steam by boiling water in the furnace and convection bank tubes. They depend on adequate flows of steam and water circulating through the tubes to provide the required steam output at specified temperature and pressure without overheating the tubes. Natural circulation boilers, which are exclusively used by Australian raw sugar factories, are driven by steam and water density differences. Such boilers can be difficult to design well with the consequence that circulation problems may occur under normal operating conditions or by operating the boiler above MCR. SRI has developed a boiler circulation analysis model, which allows the flow rates and steam quality in individual wall circuits and tubes to be predicted. The paper summarises the development of the model and describes its application to solve serveral operational problems.
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