Application of energy integration techniques (pinch technology) to reduce process steam consumption for raw sugar factories

This paper presents preliminary findings on the application of energy integration techniques (pinch technology) to determine the potential reductions in both the steam and the cooling water requirements for the process house of a raw sugar factory. The concept of an adjust temperature for the respective heat sinks (cold streams) is developed for the energy integration analysis of a sugar factory. The adjust temperature is defined as the actual temperature of the cold stream plus the minimum approach temperature for the particular heat exchange process less the pinch target minimum approach temperature. The adjust temperature applies to cold streams, and not to the temperatures of the hot streams. The adjust temperature allows for heat transfer processes which have significant differences in minimum approach temperatures. For example, the minimum approach temperature required for the operation of unstirred vacuum pans ranges from about 39 to 44 C and is considerably higher than the minimum approach temperatures required for plate juice heaters (5 C). The failure to recognise the significant differences in the minimum approach temperatures for different processing equipment can lead to erroneous results in the energy integration analysis and an underestimation of both the steam and cooling water requirements for factory operations. The outcomes predicted for the minimum steam and cooling water requirements from the energy integration analysis are highly dependent on the technologies employed in the process (i.e. the minimum approach temperatures for the heat exchange processes). The outputs from the pinch analysis of sugar factories can be utilised for modifying the layout of raw sugar factories to reduce the steam consumption of the process house, leading to (i) increased excess bagasse production for use in co-products; (ii) increased export of steam to co-located industries (e.g. ethanol distilleries); or (iii) increased co-generation capacity of the factory (e.g. export of power for renewable energy credits (RECs)).