In the production process, industrial factories require various components and tools that function interdependently. The boiler is one of the vital devices in an industrial production process, producing steam or heat that is converted into electrical energy. The electrical power generated by the boiler operates the entire production equipment.
Boilers are essential devices in a variety of industries and applications. This article will discuss boilers, their functions, components, types, as well as their principles and how they work.
In this article, we will introduce you to boilers, covering their functions, components, and how they work. Here’s more information.
Definition of Boiler and Its Functions
a. What is a Boiler?
A boiler or steam boiler is a type of closed vessel used to convert water into steam. According to Sugiharto Agus (2016), a boiler is “a closed vessel made of steel and used to produce steam.” Meanwhile, according to Sutikno, D. (2011), a boiler is “a device for producing steam, consisting of two main parts: a heating furnace to generate heat from fuel combustion and the boiler proper to convert water into steam.”
b. Boiler Functions
As mentioned earlier, the function of a boiler is to convert water into steam. In the book “Pembangkit Tenaga Listrik” by Muhammad et al. (2023), it is stated that a boiler functions to heat and convert liquid into high-pressure, high-temperature steam.
The heating process occurs in the pipes that make up the boiler’s construction. These pipes form the combustion chamber and are the location for heating water.
The water in the pipes is heated using the heat generated from fuel combustion. The combustion process is carried out continuously in the combustion chamber by supplying fuel and air for combustion.
The result of this process is high-temperature, high-pressure steam exceeding 1 atm. This steam is then used for various purposes, such as driving machinery and heating.
Components of a Boiler
A boiler consists of several main components that work together to produce steam or hot water. Based on Cahyo Adi Basuki et al. (2011) and other sources, here are some main components of a boiler or steam boiler:
- Boiler Drum
- The boiler drum functions as a steam separator, purifier, and water mixer. This component contains 50% saturated water and 50% steam.
- Water Walls
- Water walls play a role in the evaporation of water.
- Superheater
- The superheater is a component that heats steam above its saturation temperature to create dry steam.
- Economizer
- Before steam is transferred through the superheater, the feedwater is first heated in the economizer. Its function is to heat water from the high-pressure heater.
- Separator
- The separator’s function is to separate water that has not yet changed state to be reheated.
- Evaporator
- The evaporator is where the conversion of water into steam occurs. This important boiler component functions to raise the water temperature to its boiling point.
- Reheater
- Dry steam exiting the high-pressure turbine is reheated through the reheater.
- Circulation Pump
- After the separator separates water that has not yet changed state, the circulation pump’s task is to pump this water to the water walls for reheating.
- Safety Valve
- If the steam pressure in the boiler exceeds the maximum limit, some steam is released through the safety valve.
- Sight Glass
- The sight glass or gauge glass is used to determine the water level in the boiler drum to easily regulate its height.
How do Boilers Work in Power Plants?
Boilers play a crucial role in power plants by converting water into steam, which is then used to generate electricity. Here’s a breakdown of how they work:
- Water Supply: The process begins with a constant supply of water, which is pumped into the boiler at high pressure using a feed water pump.
- Pre-Heating: The water is pre-heated using feed water heaters and an economizer. The economizer uses residual heat from the flue gases to raise the water temperature close to its boiling point.
- Boiling: The pre-heated water enters the boiler drum, where it is distributed to the water walls. These water-filled tubes line the furnace walls and absorb heat from the combustion process.
- Steam Generation: As the water in the water walls heats up, it turns into steam. This steam-water mixture rises back to the boiler drum, where steam is separated from the water.
- Superheating: The separated steam is then passed through superheater coils, where it is heated further to increase its temperature and pressure. This superheated steam is essential for driving the turbines efficiently.
- Turbine Operation: The high-pressure, high-temperature steam is directed to the turbines. As the steam expand through the turbine blades, it spins the turbine, converting thermal energy into mechanical energy.
- Electricity Generation: The mechanical energy from the turbine is then converted into electrical energy using a generator.
- Condensation and Recycling: After passing through the turbine, the steam is condensed back into water in a condenser. This water is then recycled back into the boiler, and the process starts again.
This cycle, known as the Rankine cycle, is fundamental to the operation of thermal power plants.
Types of Boilers
- Fire Tube Boiler
- A Fire Tube Boiler is a type of boiler where the combustion process occurs inside the tubes. This type of steam boiler produces steam with low capacity and pressure. When heat is generated through the combustion process inside the tubes, it then transfers this heat to the boiler containing water.
- Water Tube Boiler
- A Water Tube Boiler is a type of boiler where the combustion process occurs outside the tubes. This type of steam boiler produces steam with high capacity and pressure. The heat generated from the combustion process is used to heat the tubes containing water. The steam produced is then collected from the steam drum to adjust its pressure and temperature.
- Package Boiler
- This type of boiler is a complete package with a shell and tube header structure that provides good heat transfer. Package boilers have a small combustion chamber and high heat release, allowing the water evaporation process to occur more quickly.
Principles and Working of Boilers
How do boilers work? The working principle of boilers follows these guidelines:
- If water is heated at a pressure of 1 atm, its temperature will gradually rise to 100 degrees Celsius. However, if further combustion is carried out, the temperature will not increase further, and the added heat will be used to generate steam.
- If water is heated at a pressure above 1 atm, its temperature will exceed 100 degrees Celsius. Water will boil at a temperature corresponding to its pressure. Once the water boils, the temperature remains constant, and all the heat is used to produce steam.
Additionally, the boiling of water involves heat transfer mechanisms. In a boiler, there are three ways heat is transferred: conduction, convection, and radiation.
- The heat energy generated from fuel combustion will transfer by radiation to the water pipes. The pipe surfaces absorb this heat, causing heat transfer from the surface to the inside of the pipes by conduction.
- The water flowing inside the pipes then absorbs heat between water molecules by convection. Gradually, the water changes into wet steam and then into dry steam. The dry steam is then used to drive machinery.
It is evident that boilers or steam boilers are crucial components in various industries. Although their function is merely to convert water into gas, the steam produced is essential for driving machinery.
