What is a Boiler?
A boiler is an enclosed vessel that heats a fluid, such as water, to produce steam or the vaporized form of a liquid. After that, the steam or hot water is circulated through a piping system to transfer heat for various applications such as heating, power generation, and other processes. Boilers and associated systems are efficient heat exchange systems; however, if not properly maintained and operated, they can be dangerous.
How does the boiler work?
The boiler is considered the heart of a central heating system. It circulates hot water through your radiators and faucets to provide you with both heating and hot water.
Gas boilers can be connected to the gas mains and receive a continuous supply of fuel, or they can be equipped with Liquid Petroleum Gas (LPG) cylinders that must be refilled on a regular basis. During operation, a valve connected to your boiler opens, allowing gas to enter a sealed combustion chamber. An electric ignition system or a permanent pilot ignites the fuel, which is then burned.
Hot jets connected to a heat exchanger within the boiler transfer heat to the water passing through the exchanger. The hot water is then pushed through your radiators and taps by an electric pump.
Types of Boilers
1. According to the water and hot gasses position
- Fire Tube Boiler
- Water Tube Boiler
Fire Tube Boiler
It is the oldest boiler and it was very famous in the 18th century. It is mainly used in train engines. Can find this type of boiler measurement by using their external diameter. The combustion of heat and gases flows through a pipe enclosed by water in this type of boiler.
Water Tube Boiler
A water tube boiler is a type of boiler in which water is heated within tubes and hot gases surround them. This is the fundamental definition of a water tube boiler. Actually, this boiler is the polar opposite of a fire tube boiler, in which hot gases are passed through tubes surrounded by water.
2. According to Axis of Shell
- Horizontal Boiler
- Vertical Boiler
Horizontal fire tube boilers are those in which the combustion products, as well as the water surrounding them, are sent through the tubes. Horizontal water tube boilers are those in which the combustion products surround the water-flowing tubes.
A vertical boiler is a type of fire-tube or water-tube boiler in which the boiler barrel is oriented vertically rather than horizontally. Vertical boilers were used in a wide range of steam-powered vehicles and mobile machines, including early steam locomotives.
3. According to the boiler’s position
- External Fired Boiler
- Internally Fired Boiler
External Fired Boiler
In externally fired boilers, the fuel is burned in a chamber outside the boiler shell.
Internally Fired Boiler
The combustion chamber is provided inside the shell of internally fired boilers.
4. According to the pressure
- Low-Pressure Boiler
- High-Pressure Boiler
Low-pressure boilers typically maintain pressures of 10 to 15 psi and temperatures of less than 300 degrees Fahrenheit. This type of boiler is typically used in buildings where a relatively consistent temperature is required for all spaces and no rapid temperature changes are required.
These are used to boost the plant’s efficiency. These have arisen as a result of rising fuel costs and air pollution regulations. High-pressure boilers are commonly used in modern power plants. These high-pressure boilers have pressures greater than 140 bar and temperatures ranging from 540 to 610°C.
Natural and forced circulations are used in high-pressure boilers. Centrifugal pumps are used to create forced circulation. Because of the high velocity of the water, scale formation in the tubes and boiler drums is reduced when using forced circulation.
5. According to the method of circulation
- Natural Circulation Boiler
- Forced Circulation Boiler
Natural Circulation Boiler
Natural circulation is the ability of a fluid in a system to circulate continuously with the only driving force being the difference in density. Natural circulation is also caused by convection currents that occur as a result of uneven heating of water in a boiler.
Forced Circulation Boiler
A forced circulation boiler is one that uses a pump to circulate water inside the boiler. This is in contrast to a natural circulation boiler, which uses current density to circulate water within the boiler.
6. According to use of boilers
- Mobile Boiler
- Stationary Boiler
Mobile boiler rooms are trailer-mounted, highway-legal vans or containers designed and customized to house the components of a “mini” steam plant.
These are stationary boilers that cannot be moved from one location to another. They cannot be transported to another location once they have been installed. It is mainly used in power plants and other industries
7. According to drums
- Single drum Boiler
- Multi drum Boiler
Single drum Boiler
Single drum boilers are primarily used to generate electricity. With the advent of supercritical pressure boilers, even the single drum is being phased out. This type of boiler has the advantage of being able to be designed for extremely high pressures, flows, and temperatures.
Multi drum Boiler
It is a type of water-tube boiler that generates steam, which is typically used to power ships. They are compact and have a high evaporative power, both of which encourage their use.
8. According to the nature of drought
- Forced drought Boiler
- Natural drought Boiler
Forced drought Boiler
A blower is installed near the base of the boiler, and the air is forced to pass through the furnace, flues, economizer, air preheater, and stack in a forced draught system.
Natural drought Boiler
When air or flue gases flow as a result of the density difference between hot flue gases and cooler ambient gases. The density difference causes a pressure differential, which forces the hotter flue gases into the cooler surroundings.
9. According to fuel firing
- Solid fuel-fired Boiler
- Liquid fuel-fired Boiler
- Natural Gas fuel-fired Boiler
Solid fuel-fired Boiler
A “Solid Fuel-Burning Appliance” is a chimney-connected device that burns solid fuel for the purpose of heating. These Solid Fuel Fired Steam Boilers run on wood, coal, agro waste, and briquettes as fuel.
Liquid fuel-fired Boiler
In comparison to other heating systems, a liquid fuel boiler ensures high efficiency. This boiler employs a liquid-fired burner to heat water or generates steam before it is routed to the property’s radiators.
Natural Gas fuel-fired Boiler
Natural gas furnace provides very high efficiency than other boilers. The natural gas fuel boilers use various natural gases like petrol, diesel, LPG, etc to heat water to produce steam before it is routed to the radiator of the machine.
Components of a Boiler Systems
Burner:- The boiler’s burner is the component that provides the heat that heats the system’s water. The fuel can be either oil or another natural gas.
Heat exchanger:- The boiler’s heat exchanger transfers heat from the burner to the water in the system. The heat exchanger’s role is to transfer heat from the burner to the water without coming into direct contact with it. It is like boiling water in a pot.
Supply lines:- The supply lines are the pipes that distribute the hot water or steam to the distributors in hydronic heating systems, and the supply lines are the pipes that deliver the heated water or steam to the distributors.
Return lines:- When the water cools or the steam cools and changes states back to the water, the return lines return it to the boiler for re-heating.
Firebox:- It is where the fuel and air meet and make a flame.
Refractory:- The return lines bring this water back to the boiler for re-heating when the water cools or the steam cools and changes states back to the water.
Circulator pumps:- The hot water or steam is pushed from the system to the heat distributors in our homes by circulator pumps.
Deaerators/Condenser:- Deaerator and condenser tanks are only used in steam boiler systems, not in hot water or hot oil boiler systems because the fluid is always in liquid form. These two types of tanks are nearly identical in construction, but as their names suggest, they are used for different purposes.
Economizer:- Economizers was previously only used in large-scale power plants. However, due to the increased demand for more efficient boilers in industry and marine, economizers are becoming more common. An economizer is a heat exchanger that is installed in the exhaust of a boiler. Pump specifications vary greatly depending on where the economizer is installed.
Superheater:-:- It is a boiler component that is placed in the path of hot flue gases from the furnace. The recovered heat from the flue gases is used to superheat the steam before it enters the turbine (i.e., prime mover). Its primary function is to raise the temperature of saturated steam without increasing its pressure.
Atmospheric burners, also known as natural draught burners, and forced draught burners, also known as power burners, are used in natural gas boilers. Low NOx burners and pre-mix burners are becoming more common, and in some cases, required, as air quality regulations become more stringent. These types of burners can reduce NOx emissions by ensuring efficient mixing of air and fuel as it enters the burner.
The burners and combustion process are housed in the combustion chamber, which is typically made of cast iron or steel. Temperatures inside the combustion chamber can quickly reach several hundred degrees.