A boiler is a crucial piece of equipment in most industrial, commercial facilities and power plants. Specifically, it is a closed pressure vessel that produces high or low-pressure steam or hot water for industrial or domestic use, and have a wide variety of uses. Consequently, there are several types of boilers serving every need. Here we present their classification so that you have a better idea of the kind of boiler that you need.
Classification of Boilers
Industrial Boilers
Fire Tube
They are the type of industrial boilers where heat and gases of combustion (from the furnace) pass through tubes that are enclosed on water. (1)
Water Tube
They are the type of industrial boilers where water passes through tubes while the hot combustion gas flows on the other side of the pipes. Water Tube boilers are more efficient and less dangerous than fire tube boilers. (2)
Fire Box
They are the traditional “locomotive” type of boiler. The “firebox” is the space where the heat originates, producing hot gases that pass through the tubes, heating the fluid. It is reliable but limited.
Packaged Type
The packaged type comes as a factory-assembled package with mountings, accessories, and control instruments installed on it. Either they can be of the fire tube or the water tube type. (4)
By the Type of Fuel Used by Boilers
Coal-fired
They generate thermal energy by burning pulverized coal. (21)
Oil-fired
They are used for application in low-pressure steam or hot water central heating system. (22)
Gas-fired
They, as its name indicates, are gas-fired by either natural gas or propane. (23)
Biomass
They are very similar to the conventional gas types, but instead of using gas (or oil) to produce the heat, they combust sustainably sourced wood pellets. (24)
Circulating Fluidized Bed (FBC Boiler)
CFB is a combustion technology that allows burning solid fuels in steam boilers. When air or gas passes through an inert bed of sand supported by a fine mesh, as the velocity of the air bubbles increases the bed particles, and the air attains a state of high turbulence and the bed assumes the appearance and exhibits the properties of a fluid, and hence its name. (5)
Pulverized Coal (PC Boiler)
Their use is commercial or industrial, and they generate thermal energy by burning pulverized coal or other combustible material. Specifically, compressed air blows the pulverized coal through a suitable nozzle where it burns. (6)
Waste Heat Recovery
It is an energy recovery heat exchanger that recovers heat from hot streams with potential high-energy content. In particular, hot fuel gases from a diesel generator or steam from cooling towers or even wastewater from different cooling processes such as in steel cooling. (7)
Nuclear Steam Generators
Nuclear Steam generators are heat exchangers that are used to convert water into steam from heat produced in a nuclear reactor core. Specifically, pressurized water reactors (PWR) use them in between the primary and secondary coolant loops. Then, his primary coolant is pumped through the reactor core, where it absorbs heat from the fuel rods. (8)
By the Steam Pressure of Boilers
Low-Pressure
They are of the steam or hot water types that have a maximum pressure of 15 pounds per square inch for steam and a maximum of 160 pounds per square inch for hot water. (9)
High-Pressure
A high-pressure is a boiler that generates steam or other vapor at a pressure of more than 15 PSIG or heats water to a temperature higher than 250°F and pressure greater than 160 PSIG for use external to itself. (10)
By the Boilers’ Steam Uses
Process Boilers.
They produce a heated or vaporized fluid for use in various processes or heating applications. For instance, water heating, central heating, boiler-based power generation (11)
Utility Boilers
It is a combustion unit of more than 25 megawatts that serves a generator that produces electricity for sale and fires fossil fuel. (12)
Marine Boilers
They are usually of the two-drum water-tube type with water-cooled furnaces. Likewise, heat recovery equipment of the economizer or air-heater type. The majority of ships are fitted with two units, although some large passenger ships may have three or more. (13)
By their Portability
Stationary and Portable boilers.
By the Furnace Position
Externally Fired Boilers
It has the combustion chamber outside of the shell. This type of furnaces are not surrounded by water but by brickwork (14)
Internally Fired Boilers
It is one whose furnace is wholly or partly surrounded by water. (14)
By the Axis of the Shell
Vertical (Cochran)
It is a vertical drum axis, natural circulation, natural draft, low pressure, multi-tubular, solid fuel fired, fire tube boiler with an internally fired furnace. (15)
Horizontal (Cornish, Lancashire)
Lancashire is a simple horizontal boiler which belongs to the shell and tube class. While Cornish is much like the Lancashire boiler, it is a fire-tube type of boiler that its hot gases flow in tubes and water surround these tubes in shell. (16)
By the Number of Tubes in the Boiler
Single-tube Boilers
It is a type of boiler in which hot gases pass from a fire through one tube running through a sealed container of water. (17)
Multi-tube Boilers
It is a type of boiler in which hot gases pass from a fire through many tubes running through a sealed container of water. (18)
According to the Circulation of Water and Steam in the Boiler
Natural Circulation Boilers
Inside them, the heating of water sets up convection currents that make the water flow. Consequently, as the temperature of the water in the boiler increases, the difference in density makes the water circulate. (19)
Forced Circulation Boilers
It is one where a pump circulates water inside the boiler. Notwithstanding, it differs from a natural circulation type, which relies on current density to circulate water inside the boiler. Furthermore, in some forced circulation boilers, the water flows at a speed of twenty times the rate of evaporation. (20)
Conclusion
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Sources: 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
