Severe Maintenance Problems as Your First Indicator of Big Potential Energy Savings

Abstract

Throughout 1994 and 1995, Algoma Steel Inc. conducted several modifications to their No.5 Reheat Furnace Combustion Air System during a major rebuild of the furnace. This involved a redesigned five pass recuperator, a replacement section of ductwork, and a new control scheme. Although the original objective of the project was to save gas energy with the new recuperator, it was also recognized that this was an ideal opportunity to deal with a serious and persistent ductwork cracking problem. Algoma Steel Inc. contracted FLOWCARE Engineering Inc. to determine the root source of the problem and design a solution. Through flow and spectrum analysis at the fan operating points, it was determined that the cause of the cracking was due to pressure pulsations resulting from a fan instability condition called rotating stall. The solution involved duct modifications, a revised control strategy that ensured fan operating stability and minor burner control modifications. The solution has not only eliminated all cracking problems, it has enhanced furnace controllability and provided immediate savings of electrical operating costs for the 1500 hp fan motor. It also identified an additional electrical savings of $156,000/yr which can be realized with fan and driver equipment modification.