Forced-Draft Equipment

a group of mechanisms and structures that feeds air into the combustion chamber of a boiler unit or furnace and removes flue gases from the chamber. Forced-draft fans suck air in and direct it into the combustion chamber at pressures up to 5 kilonewtons per sq m (kN/m²). Forced-draft equipment, usually consisting of exhaust fans and a chimney, creates rarefactions of up to 3–4 kN/m² in the flues, which causes discharge of the gases into the atmosphere. In supercharged boiler units, the forced-draft equipment includes only fans that supply air at a pressure of about 10 kN/m². The exhaust fans and fans used as draft equipment are usually driven by electric motors, but steam turbines may be used in large boiler units. The forced-draft equipment of steam power plants consumes 1–2 percent of the energy produced by such a plant.