Automatic Control of Two Low Pressure Boilers in Sugar Plant

The boilers in a sugar plant need to operate at constant pressure. Typically the sugar plant boilers have the load as: an electric power generation load; a cane preparation and milling load; and a process load. Generally, due to non-uniform cane feeding and milling process, large load oscillations can occur. This load swings can directly induce steam pressure oscillations which is produced from the boilers. In this plant two identical boilers with common feedwater tank and a common steam header for steam output are available. Before automation, these boilers are operated using a mechanical ‘single element based’ drum level control system. The plant turbo-generator have frequent trip due to pressure oscillations. With the aim of efficiency enhancement, the retrofit automation of boilers was implemented in a sugar plant. Hence, the pressure oscillations were reduced considerably. As an industrial automation application, this paper discusses the key features of the design and implementation of automatic control system for two low pressure boilers in sugar plant and the benefits achieved.