Influence of short-term variations on energy-saving opportunities in a pulp mill

Significant opportunities for energy savings have been identified in the hot and warm water system of a kraft pulp mill. The energy-saving opportunities found at the mill studied, 15.7 MW of steam savings and 24.8 MW of usable excess heat, correspond to 18% of the mill's total steam use. Short-term variations in the process have been studied in order to identify and quantify the influence of these variations on the energy-saving opportunities. Daily and 10-min averages of measured data were used as varying input data in the retrofitted heat exchanger network. When the short-term variations were considered, the total energy-saving opportunities fell by 8% when daily averages are used and by 11% when 10-min averages are used. At least 65% of the influence of short-term variations was detected when seasonal variations are considered.