Cost-effective industrial boiler plant efficiency advancements

Natural gas and electricity are expensive to the extent that annual fuel and power costs can approach the initial cost or: an industrial boiler plant. Within this context, this article examines several cost-effective efficiency advancements that were implemented during a recently completed boiler plant replacement project at a large semiconductor manufacturing complex. The "new" boiler plant began service in November 1996 and consists of four 75,000 lb/hr water-tube boilers burning natural gas and producing 210 psig saturated steam for heating and humidification. Efficiency advancements include: 1) Reheating of cleanroom make-up air with heat extracted during precooling. 2) Preheating of combustion air with heat extracted from boiler flue gas. 3) Preheating of boiler feedwater with heat extracted from the exhaust of a nearby gas turbine. 4) Variable speed operation of boiler feedwater pumps and forced-draft fans. 5) Preheating of boiler make-up water with heat extracted from boiler blow-down. These efficiency advancements should prove of interest to industrial energy users faced with replacement of aging, inefficient boiler plants, rising fuel and power prices, and increasing pressures to reduce operating costs in order to enhance competitiveness.