Boiler Basics: What Are The Different Types Of Boilers?

ICI — or industrial, commercial, and institutional — boilers create steam or heated water, providing heat for climate control and industrial processes. From hospitals and schools to factories and food production, boilers are an intrinsic piece of equipment for institutions and operations across many industries. Boilers vary in size and intensity, employing different heat sources and methods of heat exchange. The following are the types of boilers most commonly used in industrial and commercial settings, along with some terms to know when trying to differentiate between different boiler styles and figuring out their ideal uses.

A fire tube boiler setup directs heated gases into a number of tubes that run through a water-filled chamber. Steam is created by thermal induction which transfers the heat through the walls of the tubes. These types of boilers are ideal in operations where there is a large and constant steam demand. However, they are typically not suitable for high pressure applications.

Conversely, in a water tube boiler the water is inside the tubes and the heat source is on the outside. This ability for rapid heat transfer makes water-tube setups ideal for applications with variable load requirements and high pressure demands. Water tube boilers are available in significantly larger capacities than fire-tube style models.

Packaged vs Field-Erected
Smaller boilers are usually shipped right to your location, ready-made or requiring only minimal assembly. Most fire-tube and other small application boilers are installed this way. Larger water-tube boilers are usually field-erected, meaning they are constructed on-site since it would be prohibitive — and in some cases impossible — to bring the fully assembled boiler system into the room.

Boiler Fuel Types
Another way that boilers can be classified is by fuel type. The most common fuel types used in industrial boiler systems are as follows:

Most industrial coal-fired boilers run on crushed coal, which burns more efficiently than large coal clumps.

Gas and Oil
Gas-fired boilers operate using natural gas, most often a mix of methane, ethane, butane, pentane, or propane. Boilers that run gasoline, diesel, and other petroleum-based fuels are typically classified as oil-fired boilers.

Some boilers even burn combustible plant material like wood chips, wood construction debris, and corn husks.

Combustion Types
Another way to distinguish boilers is by the way they achieve combustion. The aforementioned boiler types typically fall into one of the following combustion method categories:

Stokers burn lump coal. Spreader stokers feed a continuous supply of coal onto the bed. A chain-grate stoker (sometimes called a traveling grate stoker) deposits the fuel in one area where it is then distributed by a moving grate.

Thermic Fluid
Thermic fluid heaters use a petroleum-based fuel inside a closed system. The closed system can lead to greater efficiency, although it is not ideal for certain applications.

Fluidized Bed
The most common method used for burning solid fuels in boilers today, fluidized bed technology involves a bubbling hot mixture of water and material particles (like sand) in which fuel is suspended. This allows for rapid heat transfer and cleaner, more efficient operations.

There are several different types of boilers within each category so be sure to explore different brands, models, and features when shopping.