Utilization of heat waste energy generated from air compressors as boiler feedwater preheating, a case study in smelter plant Sorowako

Waste heat is the heat produced by a machine, or other processes which use energy, as a product of doing works. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms, for example, a refrigerator warms the room air, an internal combustion engine generates high-temperature exhaust gases, and electronic components are warm during the operation. Instead of being wasted by release into the ambient environment, sometimes waste heat can be utilized by another processes, or a portion of heat that would otherwise be wasted can be reused in the same process. In this case, the objective of this paper is to investigate the amount of energy needed to generate 1 ton steam around 1,024.000 kkal. Heat and waste energy generated by mechanical motion of centrifugal air compressor could be utilized as boiler feedwater (bfw) preheating around 2 -2.5 % from energy needed to produce the saturated steam. In smelter plant facilities in Sorowako, there are 14 units of centrifugal compressors operated under The Utilities Thermal Section to produce pressurized air with daily production average of 28,000 - 33,000 SCFM. These compressors consume 21,000-22,000 LPM of cooling water on average. The heat is obtained from the cooling water then is used to increase the boiler feedwater temperature in the range 8 - 9 ^o C. It means there would be a possibility for fuel saving in Boiler.