BOILERS

INTRODUCTION TO BOILERS

A boiler is an enclosed vessel that provides a means for combustion and transfers heat to water until it becomes hot water or steam.

The hot water or steam under pressure is then usable for transferring the heat to a process.

Water is a useful and cheap medium for transferring heat to a process.

When water is boiled into steam its volume increases about 1,600 times, producing a force that is almost as explosive as gunpowder.

Liquid when heated up to the gaseous state this process is called evaporation.

The heating surface is any part of the boiler; hot gases of combustion are on one side and water on the other.

The source of heat for a boiler is combustion of any of several fuels, such as wood, coal, oil, or natural gas.

HISTORY

Boilers were built as early as the 1st century AD by Hero of Alexandria but were used only as toys, till 17th century.

The first boiler with a safety valve was designed by Denis Papin of France in 1679; boilers were made and used in England by the turn of the 18th century.

Early boilers were made of wrought iron; as the advantages of high pressure and temperature were realized, manufacturers turned to steel.

NEED OF BOILERS IN INDUSTRIAL AND DOMESTIC APPLICATIONS

Boilers are an essential component in many industrial and residential heating systems. Here are some of the reasons why boilers are important:

Heating: Boilers are used to generate heat, which is then transferred to water or air, and distributed throughout the building. This provides a source of warm air and hot water for the occupants of the building.

Energy efficiency: Boilers are designed to be energy-efficient and can help reduce energy costs by using energy more effectively.

Reliability: Boilers are built to last and provide reliable heating, even in the harshest weather conditions.

Safety: Modern boilers are equipped with safety features that protect against hazards such as gas leaks and overheating.

Versatility: Boilers can be used for a variety of applications, including space heating, water heating, and steam generation.

Environmental responsibility: Many boilers use renewable energy sources, such as biomass or geothermal energy, which helps reduce the carbon footprint of the building.

CLASSIFICATION OF BIOLERS

SOME OF THE MAIN CLASSIFICATIONS OF BOILERS ARE DISCUSSED BELOW

BASED ON PASSAGE THROUGH BOILER

Firetube boilers are the oldest type of boilers and are widely used in small and medium-sized industrial applications. They consist of a cylindrical shell, a firebox, and tubes that carry water from the inlet to the outlet. Hot gases from the firebox pass through the tubes and heat the water, which then produces steam.

Water tube boilers, on the other hand, have water flowing inside tubes and hot gases surrounding the tubes. The water tubes are connected to a steam drum and a mud drum at the top and bottom, respectively. The hot gases pass over the water tubes, transferring heat and producing steam. Water tube boilers are more efficient and versatile than firetube boilers, and they can be used in high-pressure and high-capacity applications.

Tubeless boilers are a type of water tube boilers that have been modified to eliminate the need for a steam drum and a mud drum. Instead, the water tubes are directly connected to the heating elements, which are surrounded by hot gases. This design reduces the size and weight of the boiler, making it more compact and easier to install.

BASED ON BOILER AXIS

Horizontal boilers: As the name suggests, horizontal boilers are boilers that are horizontally mounted. They are often used in large industrial applications as they have a larger water capacity and can handle a higher steam output. They are also suitable for use in power plants, as they can generate large amounts of steam to drive turbines.

Vertical boilers: Vertical boilers are boilers that are vertically mounted. They are usually smaller in size compared to horizontal boilers and are more suited to smaller industrial applications or domestic heating systems. They are also easier to install and maintain, and they take up less floor space.

Inclined boilers: Inclined boilers are boilers that are mounted at an angle. They are designed to provide a balance between the space requirements of horizontal boilers and the ease of use of vertical boilers. They are typically used in small-scale industrial applications and are particularly suited for use in spaces where height restrictions are in place.

BASED ON WORKING PRESSURE

A high-pressure boiler is a boiler in which steam is generated at pressures greater than 15 psi, while a low-pressure boiler is a boiler in which steam is generated at pressures less than 15 psi. High-pressure boilers are typically used in power plants and other large-scale industrial applications where high-pressure steam is required for the generation of electricity or for process heating.
Low-pressure boilers, on the other hand, are typically used in applications where low-pressure steam is required for heating or humidification. Low-pressure boilers are also used in small-scale industrial applications, such as laundries, breweries, and food processing plants.

BASED ON CIRCULATION METHOD

Natural draught boilers rely on the natural flow of air to provide the oxygen necessary for combustion. In these boilers, the hot gases from the combustion process rise naturally, creating a flow of air that draws in fresh air for combustion. The chimney of a natural draught boiler acts as a natural flue, allowing the hot gases to escape to the outside.
Forced draught boilers use a fan to provide the necessary airflow for combustion. The fan is typically located in the chimney, and it pushes the hot gases from the combustion process out of the boiler and up the chimney.

CONSTRUCTION OF A BOILER

The construction of a boiler can vary depending on the specific type of boiler, but some common components include:

Pressure Vessel: The pressure vessel of a boiler is typically made of steel or cast iron and acts as the main container for holding the fluid to be heated. It is designed to withstand the pressure and temperature of the fluid within.

Burner: The burner is the component of the boiler that is responsible for providing the heat energy to the fluid. The heat is generated by the combustion of fuel, such as natural gas, oil, or coal.

Heat Exchanger: The heat exchanger is the component of the boiler that transfers the heat from the burner to the fluid. The heat exchanger can be made of a variety of materials, including steel or cast iron, and is designed to withstand the high temperatures and pressure of the fluid.

Controls: The controls of a boiler are responsible for regulating the temperature, pressure, and flow rate of the fluid. They typically include a thermostat, pressure gauge, and safety valves.

Chimney: The chimney of a boiler is responsible for removing the waste gases produced by the combustion of fuel in the burner. The chimney is typically made of brick or metal and is designed to safely vent the waste gases to the atmosphere.

WORKING OF A BOILER

The working process of a boiler can be summarized as follows:
Fuel preparation: Boilers are typically powered by natural gas, coal, oil, or wood. The fuel is prepared for combustion by grinding it into small particles and drying it, if necessary.
Combustion: The prepared fuel is burned in a combustion chamber, which is usually located at the bottom of the pressure vessel. The heat generated by the combustion process heats the water or fluid in the pressure vessel.
Generation of steam: As the fluid temperature increases, the pressure in the vessel also increases. When the pressure reaches a certain level, the fluid boils and turns into steam. The steam rises to the top of the pressure vessel and is collected in the steam drum.
Steam separation: In the steam drum, the steam is separated from the fluid. The fluid is returned to the heat exchanger to be heated again, while the steam is sent to the end-use application.
Fig. Steam Separator used in boilers
Steam utilization: The steam generated by the boiler can be used for various purposes, such as powering a turbine to generate electricity, heating a building, or sterilizing equipment in a manufacturing process.
Cooling and condensation: After the steam has been used, it must be cooled and condensed back into fluid form. This is typically done by passing the steam through a condenser, where it gives up its heat to a cooling fluid, such as water. The condensed fluid is then returned to the pressure vessel to be heated again.
Fig. Steam condenser
BOILER MOUNTINGS
Boiler mountings are fittings or devices that are mounted on boilers for the safe and efficient operation of the boilers. These mountings ensure that the boiler operates within safe limits and prevent accidents that can be caused by excessive pressure, temperature or water levels. The following are some of the common boiler mountings:
Safety valve: It is a safety device that automatically releases steam in case the pressure inside the boiler exceeds the set limit.
Fig. Safety Valve in steam boilers
Feed check valve: It prevents the backflow of water from the feed pump into the boiler, ensuring that the water flows in the right direction.

Feed water regulator: It regulates the flow of feed water into the boiler, ensuring that the water level inside the boiler remains constant.
Fig. Feed water regulator in boilers
Blow off cock: It is used to discharge excess water and impurities from the boiler, which are accumulated during the boilers operation.
Fusible plug: It is a safety device that melts at a predetermined temperature, releasing water into the boiler to extinguish the fire in case of overheating.
Water level indicator: It helps to monitor the water level inside the boiler
Steam stop valve: It regulates the flow of steam from the boiler to the engine or turbine.

BOILER ACCESSORIES
Boiler accessories are additional components that are not necessarily required for the basic operation of a boiler but enhance its functionality and safety. Some of the common boiler accessories are:
Economizer: It is an accessory that increases the efficiency of a boiler by preheating the feed water before it enters the boiler.
Superheater: It is an accessory that raises the temperature of steam produced by the boiler, making it more useful for industrial applications.
Deaerator: It removes dissolved gases such as oxygen and carbon dioxide from the feed water, preventing corrosion of the boiler and its components.

Steam injector
A steam injector is a device used to feed water into a steam boiler. It works by using steam from the boiler to create a vacuum, which draws water into the injector and mixes it with the steam. The resulting mixture is then forced back into the boiler at high pressure.

In addition to these, there are many other accessories that can be added to a boiler system based on the specific requirements of the application. These accessories can improve the efficiency and safety of a boiler, as well as enhance its performance and reliability.

CONCLUSION

A steam boiler is a steam producing heating system; it produces energy by heating water to create steam.
A steam boiler burns fuel to heat water. The combination of heat and water produces steam.
Steam boilers are defined by their construction, portability, types of tubes, types of fuel, and the pressure they produce.
A steam boiler absorbs heat that is released from combustion. The three ways that the heat is transferred are radiation, convection, and conduction.
The designs and types of steam boilers widely vary depending on their construction and purpose.
PREPARED BY : GROUP 6
(28) KALE AKSHAY DATTU
(29) KALE SUPARSHVA
(30) KALE VAIBHAV DATTA
(31) KAMLAIT SUHAS MOHAN
(32) KARJULE SUYASH SUNIL

UNDER THE GUIDANCE OF : PROF. M.K.NALAVADE

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