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Show A number of uses for the reject heat exist (17). Since many of these uses are batch-type process, TES plays a vital, role. Electric furnace scrap preheating can measurably improve furnace performance. If for instance, the scrap change was preheated to 500°C, furnace energy use could be reduced by about 18%, electrode wear by 24%, and productivity increased by 20% (17). If the scrap was preheated to 930°C, a 45% energy reduction could be realized (17). In soaking pit applications TES could be used to pre--heat ingots and to supply much of the energy required to maintain the pit at its proper temperature, although auxiliary heating would still be required. Coal pre-heating for coking operation, blast furnace air preheat, and sinter/iron ore pre-heating are other identified uses that would require TES because of the intermittent nature of the heat source, or the use. Food Processing Study of the food processing industry (18) revealed a storage application in the Canned Specialties (SIC 2032) area. A schematic (19) of the proposed system is shown in Fig. 10. Waste water streams from the retorts, can and bottle washers, and continuous pasteurizing systems are collected and pumped through a plate-type heat exchanger to heat incoming fresh water. The heated fresh water is then supplied to the process through the storage tank. The circulation flow rate is controlled to satisfy the production demand for hot water during the two daytime production shifts. The excess energy is stored for later use during the third-shift clean-up operations. Using this approach fossil fuel usage can be reduced by about 3%. Cogeneration Applications With electric utilities now required to buy cogenerated power, opportunities exist in the industrial sector to alter power production schedules to take advantage of off-peak electrical rates. This is, in fact, being done at some mills in Scandanavia (20). The pulp and paper feedwater heater application previously described is an example of how thermal energy can be stored during periods of low electrical demand or during off-peak hours and then used for power production during periods of high demand or 8-11 |