Boilers are sophisticated pieces of equipment which have evolved considerably since their first invention and implementation. Massive progress has been made in terms of efficiency, pressure and temperature capabilities, and safety. These advances have come as a result of innovation in the key systems and integral component parts of the boiler.
The Feedwater System
The feedwater system refers to the system that supplies the liquid water to the boiler so that it can turn the water into steam. The feedwater may come from condensate or condensed steam that the boiler itself recirculates, or it may come from outside of the boiler, usually in a preheated or treated form that will make it more efficient and safer for the boiler. Some key components of the feedwater system include:
- Boiler Feedwater Heaters – Feedwater heaters make boilers more efficient by preheating the feedwater so that the boiler doesn’t have to work as hard to get the temperature of the feedwater high enough to convert into steam. The heat for the feedwater heater is usually recovered and rerouted from the boiler itself.
- Deaerators – Deaerators help treat the feedwater before it enters the boiler by removing excess oxygen from it. This is done by passing a stream of steam through the feedwater, which thereby strips it of oxygen because oxygen is less and less soluble at higher temperature levels.
- Feed Pump – The feed pump is the pump which pumps the feedwater into the boiler.
- Economiser – As their name implies, economisers help make the boiler more economical to run. They accomplish this by extracting heat from the exhaust of the boiler and re-routing it to the feedwater. Not all boilers have economisers.
The Steam System
The steam system refers to the system through which the steam in the boiler passes. Steam naturally rises above liquid water because it is less dense than liquid water.
- Steam Drum – The steam drum is the upper drum of a water-tube boiler where the steam separates from the liquid water. The lower drum is referred to as the mud drum and it contains the liquid water.
- Boiler Tubes – The boiler tubes are the tubes through which the steam passes as it makes its way through the boiler. High strength carbon steel is often used in the fabrication of boiler tubes to make it more durable and to resist problems associated with corrosion or mineral deposits.
- Superheater – The superheater is used to remove excess moisture content from the steam by raising it above its saturation point. This is particularly important if the steam is being used for power generation because water droplets in the steam could damage the turbines. Because of the high temperature demands placed on superheaters, a higher alloy steel is typically used in their construction.
- Attemperator – Attemperators help control the degree of superheat and help regulate superheat temperature. To do this, they partially de-superheat the steam by injection of water into the superheat steam flow.
- Condenser – The condenser condenses the steam back into water so that it can be reused in the feedwater system. This improves the overall efficiency of the boiler.
- Condensate Pump – The condensate pump pumps the condensate back to the storage tank.
The Fuel and Combustion System
The fuel and combustion system is the system that ignites the fuel source which in turn releases the heat needed to convert the liquid water into steam.
- Burner – The burner introduces the fuel and the air needed for combustion into the furnace at the desired concentration. Maintaining the right balance of each is important because too much or too little fuel or air can reduce the efficiency of the boiler and create extra waste.
- Furnace – The furnace is the enclosed space where the combustion actually takes place.
- Firebox – In a water-tube boiler the firebox is what houses the combusted heat. It is surrounded by water and heats the water by radiant energy.
- Stack – The boiler’s stack acts as a type of chimney through which the combustion gases exit the boiler as exhaust.
- Baghouse and Bags – The baghouse acts as a filtration system for the boiler’s exhaust. The dirty gases enter the baghouse and are filtered by fabric or felt bags which capture solids such as ash and soot. This allows clean air to exhaust the entire system.
Other Component Parts
Some other important component parts of a boiler include the following:
- Drain – The drain is a valved connection at the lowest point of the boiler which allows all of the water to be drained out of it if needed.
- Safety Valve – The safety valve is designed to automatically open if the pressure within the boiler exceeds a certain threshold.
- Safety Shut-off Valve – The safety shut-off valve is a valve designed to automatically shut off the fuel source during critical safety times.
- Baffle Plate – The baffle plate is placed over the firehole. It is designed to direct secondary air into the firebed so it can be thoroughly mixed with the flames and hot gases.
- Air Preheaters – Air preheaters are used to preheat the air prior to combustion to make the combustion and the boiler itself, more energy efficient. To do this they draw heat from the hot stack gases.
There are many more parts to an industrial boiler, and different types of boilers have different features and subsequently different parts. The parts and systems listed in this article act as an overview of the integral components parts of an industrial boiler. STI Group offers a full range of boiler services including boiler maintenance, fabrication, installation, retrofits, and more.