Boiler System Major Components and Function

 

Feedwater Heaters

Feedwater heaters are energy recovery devices generally found only in large steam generating plants where all of the steam generated is not reduced to condensate by the steam user. This "waste steam" is reduced to condensate for return to the boiler in the feedwater heater. The boiler feedwater is used as a cooling medium to reduce the steam to condensate, which increases the temperature of the feedwater and, thereby, increases the thermal efficiency of the boiler.

Fuel Heater

Many boilers firing heavy fuel oil require fuel heaters to reduce the fuel viscosity, so the fuel can be atomized by the burner system for complete combustion.

Deaerators

A deaerator is a special case of feedwater heater that is designed to promote the removal of non-condensable gases from the boiler feedwater. The principal gases of concern are oxygen, carbon dioxide, and ammonia, which are major contributors to boilers, and steam and condensate piping corrosion problems.

Pumps

In most hot water systems, the system circulating pumps are electric motor-driven, end suction centrifugal pumps. In steam systems, the condensate return pumps are typically electric motor-driven, end suction, centrifugal or turbine-type pumps. Feedwater pumps are generally electric motor-driven, multiple-stage, end suction centrifugal pumps. The shutoff head of the pump must be greater than the steam or hot water system operating pressure.

Combustion Air Blowers

In many packaged boiler installations, the combustion air fan is designed and provided by the boiler manufacturer and is integral with the boiler housing. An important characteristic of the blower is the ability to maintain a relatively constant air pressure over a wide range of airflows.

Flue

Flues (boiler firebox exhaust duct or boiler discharge stack) must be large enough to conduct the products of combustion away from the boiler with a minimum of duct friction loss.

Economizer

An economizer is an energy recovery device that uses the hot exhaust gases from the boiler (waste heat) to heat combustion air or feedwater.

Steam Traps

Steam traps are installed throughout steam systems to remove condensate (spent steam), air, and non-condensable gases from the steam system. There are five types of steam traps in general use today, as described below.