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This paper examines several cost-effective steam conservation and boiler plant efficiency advancements that were implemented during a recently completed central steam boiler plant replacement project at a very large semiconductor manufacturing complex. They were:

  1. Reheating of dehumidified clean room makeup air with heat extracted during precooling.
  2. Preheating of deionization feedwater with refrigerant heat of condensation.
  3. Preheating of boiler combustion air with heat extracted from boiler flue gas.
  4. Preheating of boiler feedwater with heat extracted from gas turbine exhaust.
  5. Variable-speed operation of boiler feedwater pumps and forced-draft fans.
  6. Preheating of boiler makeup water with heat extracted from boiler surface blow-down.

The first two advancements (steam conservation measures) saved about $1,010,000 per year by using recovered waste heat rather than steam-derived heat at selected heating loads. The last four advancements (boiler plant efficiency measures) reduced the cost of steam produced by about 13%,or $293,500 per year, by reducing use of natural gas and electricity at the steam boiler plant. These 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.

Units: Dual

Citation: ASHRAE Transactions, vol. 105, pt. 1