Industrial Boilers are among the most critical thermal equipment in various industries and heating systems. They operate by transforming water into steam or hot water through the use of thermal energy. Boilers are manufactured in various types based on different needs and operational conditions, each with its own advantages and specifications. This article will introduce the types of boilers and examine their various features.
What is a boiler?
A boiler is an equipment designed to heat liquids, mainly water. The steam or hot water generated is used for purposes such as heat transfer, turbine operation, industrial processes, and environmental heating. Boilers are classified into various types based on their design and application, each with its own unique features and advantages.
Types of boilers
Boilers are classified into different categories based on their structural design, operation, and the type of fluid.
1- Based on the structure and the flow of water and combustion gases
a)Fire-tube boilers
b) Water-tube boilers
2- based on the working fluid
a) Hot water boilers
b) Steam boilers
c) hot oil boilers
In the following, the types of boilers are explained in detail based on their structure and working fluid.
Fire-tube boilers
They are one of the most common types of boilers. In this type, hot combustion gases pass through tubes and heat the surrounding water, turning it into hot water or steam. Fire tube boilers are widely used Due to their simple design and affordable price.
Two-pass Fire tube boilers: This type of industrial boiler allows the combustion gases to pass through the fire-tubes twice during operation.
Three-pass fire tube boilers: In this type of boiler, the hot gases produced from fuel combustion pass through the fire tubes three times. This design maximizes heat transfer to the surrounding water, significantly improving thermal efficiency.
Four-pass fire tube boilers: In this type, hot gases pass through the fire tubes four times. This design significantly increases thermal efficiency and energy productivity. Four-pass boilers have the highest efficiency among the fire tube boilers.
Reverse Flame Boiler: In this type of boiler, the hot gases generated from combustion pass through the furnace, then return to the furnace again before entering the fire tubes. This design increases thermal efficiency and energy productivity.
Water-tube boiler
In this type of boiler, water circulates inside the tubes, and hot gases pass around them. These boilers are used to produce high-pressure steam, as water and steam flow through the tubes. While fire-tube boilers are used for generating steam at medium pressures, water-tube boilers are typically used in heavy industries such as refining, food processing, and power plants.
In water-tube boilers, combustion gases transfer their energy to the water in two to four stages, as follows:
1- combustion chamber: in this section, the majority of heat transfer occurs through radiation.
2- bundle of tubes: After the combustion products pass through the combustion chamber, they flow over the water tube bundle. At this stage, the majority of heat transfer occurs through the convection mechanism.
3- Superheater: If the boiler is equipped with a superheater, the combustion products pass over the superheater before flowing over the tube bundle, converting saturated steam into superheated steam.
4- Economizer: If the boiler is equipped with an economizer, the combustion products pass over the economizer tubes before entering the chimney, transferring their energy to the water.
Condensing boiler
It is a type of advanced boiler that operates with significantly higher efficiency than conventional boilers, using a specific technology. This high efficiency is due to the recovery of latent heat from the steam in the exhaust gases. The heat transfer surface is designed to condense the steam, turning it into liquid. In this process, the latent heat is released and transferred to the water inside the boiler. As a result, the maximum amount of heat from the fuel is transferred to the water, greatly increasing the boiler’s efficiency. In terms of structure, these boilers can have either a fire-tube or water-tube design.
Industrial boilers, including fire-tube or water-tube types, are classified into hot water boilers, steam boilers, and hot oil boilers based on the working fluid and the phase of the output fluid.
1- Hot water boiler
Hot water boilers are used to produce hot water for central heating systems in buildings and various industries. These devices are typically used for generating hot water at medium-temperature and can be applied in residential, commercial, and industrial systems.
2- Steam boiler
A steam boiler is used to generate steam and is one of the most important equipment in various industries, including food, paper, chemical, oil, and gas industries. The produced steam can be used for heat transfer, electricity generation, or in various chemical processes.
3- Hot oil boiler
The hot oil boiler is another type of industrial boiler that uses oil instead of water as the heat transfer fluid. Oil is used due to its high boiling point, allowing it to transfer heat at high temperatures (up to 300°C and beyond). These boilers are highly effective in industries that require high-temperature heat.
Industrial boilers, including fire-tube or water-tube types, are classified into hot water boilers, steam boilers, and hot oil boilers based on the working fluid and the phase of the output fluid.
The main components of a boiler
Boilers consist of various parts, each of which has an important role in its operation. The following are some of the key components of a boiler.
1- Furnace
It is the main component of a boiler where a significant amount of heat is generated through fuel combustion. The design of the furnace varies based on the type of fuel and the boiler capacity. In this section, air and fuel are mixed in the proper ratio and ignited. The heat transfer mechanism in the furnace is primarily radiative.
2- Boiler Drum
In fire-tube boilers, the boiler drum contains water that surrounds the combustion chamber and fire tubes. Water-tube boilers, on the other hand, have two or more drums that serve as tanks for collecting water and steam. This is typically the largest part of the boiler.
3- Fire tubes
These are tubes through which the hot combustion gases pass, transferring their heat to the surrounding water. These tubes are used in fire-tube boilers, with water surrounding the tubes.
4- Water tubes
These are tubes through which water flows, while hot gases pass around them. These tubes are used in water-tube boilers, where the combustion products surround the tubes.
5- Economizer
It is a device that preheats boiler feedwater using heat from the flue gas exiting the chimney. By using an economizer, the boiler’s efficiency is improved.
6- Superheater
It is a device that heats the saturated steam to a higher temperature and converts it into superheated steam.
7- Drum Separator
This device removes the excess water from the steam and sends it back to the boiler.
8- Safety valves
They are used to prevent excessive pressure buildup inside the boiler. In case of excessive pressure, the safety valves open and release the extra steam.
9- Burner
Industrial burner burns fuel and releases its thermal energy. The burner type depends on the type of fuel and the boiler design.
10- Feed pump: It is a pump that injects water into the boiler under pressure.
11- Chimney: It is used to discharge the combustion gases.
Boiler operation
Boilers operate by using the thermal energy from the fuel in the burner to convert water into steam or hot water. The operation of boiler is explained below.
1- Water inlet
Initially, water enters the boiler from a source with appropriate pressure. The inlet water should meet the standard range for dissolved particles and pH to prevent the formation of scale on the boiler tubes. If scale builds up on the tubes, heat transfer is reduced, leading to a decrease in the boiler’s efficiency.
2- Burner ignition
When the fuel (such as gas or liquid fuel) mixes with air in the boiler burner, the burner’s igniter is activated, and the fuel begins to burn. By mixing fuel (such as gas or liquid fuel) and air in the boiler burner, the igniter is triggered, and the fuel begins to burn.
3- Heat transfer to the water
The heat that is produced by the flame in the burner is transferred to the water. Depending on the type of boiler, this heat either moves through the tubes or is directly transferred to the water inside the boiler. In a fire-tube boiler, the hot gases from combustion pass through the tubes, and the water surrounding these tubes gets heated. In a water-tube boiler, water flows through the tubes, and the hot combustion gases which surround the tubes heat the water.
4- Steam or hot water production
When the water reaches the desired temperature, it either transforms into steam (in steam boilers) or is used as hot water within the system (in hot water boilers). The generated steam or hot water is then used in different applications, such as heating buildings and in power generation industries.
5- Exhaust gases discharge
The hot gases produced from combustion are directed out through the boiler’s chimney to prevent their accumulation inside the boiler.
6- Pressure and temperature control
The boiler has control systems that regulate the temperature and pressure by adjusting the burner flame intensity. If the pressure rises too high, the safety valves open to prevent potential hazards.
Wide applications of industrial boilers
Industrial boilers, due to their capability for producing steam and hot water, have extensive applications across various industries. Some of the most important applications of them include:
1- Power generation industries
These devices are used in power plants to generate steam. This high-pressure steam is used to drive steam turbines, providing the mechanical energy required for electricity generation. Water-tube boilers are typically used in this industry because they can produce steam at high pressure and temperature.
2- Food industries
Boilers are used in food manufacturing processes to produce steam for cooking, sterilizing, and processing food. The steam produced must meet hygienic standards and be free from any contamination. Therefore, specialized boilers with high sanitary standards are used in this field.
3- Oil and gas industries
Industrial boilers are used in refineries and petrochemical plants for processing and separating petroleum and chemical materials. In these processes, steam serves as a heat source for heating, evaporation, and transporting materials. These boilers must operate continuously and with high efficiency.
4- Chemical industries
In the chemical industry, boilers are used to produce steam for chemical reactions, heating materials, and producing final products. Various thermal processes in this industry require boilers capable of generating steam at high temperatures and pressures.
5- Textile industries
In the textile industry, boilers are used to produce steam for various processes such as dyeing, washing, and regulating the temperature of fibers and fabrics. The steam generated by these boilers helps improve product quality and reduce production time.
6- Pharmaceutical industries
Industrial boilers in the pharmaceutical industry are used to produce clean steam for sterilizing equipment and raw materials, regulating process temperatures, and producing pharmaceutical products. High-purity steam is crucial in this industry.
7- Pulp and paper industries
In paper manufacturing, industrial boilers are used to produce steam for evaporating the water in the pulp and regulating temperature in different processes. The steam helps with drying the paper more quickly and evenly.
8- Central heating systems
Hot water boilers are widely used in central heating systems to provide the necessary heat for large buildings, residential complexes, hospitals, and hotels.
9- Industrial car washes
In industrial car washes, boilers are applied to generate steam for cleaning and disinfecting vehicles, heavy equipment, and various surfaces.
Boiler; The key element in steam production
Industrial boilers, as one of the key equipment in various industries, are responsible for producing steam and hot water using thermal energy from fuel. The diverse design of industrial boilers, including fire-tube, water-tube, and condensing types, allows for use in a wide range of industrial applications. Boilers play a crucial role in enhancing efficiency and optimizing energy in industries such as power, food, oil and gas, chemicals, and many others. Packman Industrial Group, with the production of advanced industrial boilers and the provision of high-quality services, is recognized as one of the main suppliers in this field, offering specialized solutions to effectively meet the needs of industries.
