News

1. What is an Industrial Boiler?

Boilers have been in use for over 150 years. Initially, they were designed in simple forms, resembling basic kettles. However, to meet the increasing energy demands of various industries, boilers have continuously evolved to feature higher capacities, improved thermal efficiency, and simplified installation and operation, adapting to real-world conditions.

An industrial boiler is a device that generates steam by converting heat from burning fuels such as coal, oil, gas, or biomass.

Typically constructed by welding and assembling thick steel plates with high strength, industrial boilers are capable of operating at extreme pressures, ranging from a few Barg to several hundred Barg, significantly higher than standard-pressure systems.

Today, industrial boilers are widely used across various industries, including Food & Beverage, Paper, Chemicals, Textiles, Steel, Animal Feed and more. Additionally, high-pressure steam from boilers is utilized in energy production by combining it with turbines to generate electricity for daily life.

2. Operating Principles of Industrial Boilers

Industrial boilers operate on the principle of converting thermal energy into steam energy. Much like a large pressure cooker, a boiler is a closed system containing water.

When fuels such as coal, oil, gas, or biomass are burned in the combustion chamber, they generate high-temperature hot gases. These gases heat the water (or liquid) inside the boiler, causing it to boil and produce steam.

The steam generated can reach varying pressures depending on the boiler's size and specifications. These pressure levels can be adjusted based on the production requirements.

The steam is then distributed through pipelines to various manufacturing units, power plants, and other applications.

3. Types of Boilers

There are many different types of boilers, classified based on their applications. Here are some common methods of classification:

3.1 Classification by Development History

The most basic classification includes two types of boilers: fire-tube boilers and water-tube boilers. The main difference lies in how heat is transferred to the water to generate steam.

3.1.1 Fire-Tube Boilers

In a fire-tube boiler, hot gases from the combustion process pass through a series of tubes submerged in a water-filled shell. As the temperature of the water surrounding the tubes increases, it transitions to steam, accumulating at the top of the boiler and being directed to the desired application area.

Key Feature: Combustion gases flow inside the tubes, while water and steam circulate outside the tubes.

Fire-tube boilers

Fire-tube boilers are cost-effective due to their simple design but are limited in their ability to meet high capacity and efficiency demands.

3.1.2 Water-Tube Boilers

Water-tube boilers are designed with tubes containing water, which are heated externally by hot gases produced during combustion. The heat transfers to the water inside the tubes, converting it into steam. The steam is then collected in a steam drum or manifold and delivered to the required application area.

Key Feature: Water and steam flow inside the tubes, while combustion gases circulate outside.

Water-tube boilers

Water-tube boilers offer higher thermal efficiency than fire-tube boilers but are more complex to construct and require high-quality feedwater for optimal performance. Water treatment systems such as softeners and deaerators are essential for efficient operation.

3.2 Classification by Pressure Levels

• Low-Pressure Boilers: Operating at less than 15 bar and temperatures below 350°C.
• Medium-Pressure Boilers: Operating between 15 to 60 bar and temperatures from 350°C to 450°C.
• High-Pressure Boilers: Operating above 60 bar and temperatures from 450°C to 540°C.
• Super High-Pressure Boilers: Operating at pressures above 140 bar.

For special applications, some boilers operate above the critical pressure of water (225.3 bar), referred to as supercritical boilers.

3.3 Classification by Steam Output

• Small-Capacity Boilers: D < 20 T/h.
• Medium-Capacity Boilers: 20 ≤ D < 75 T/h.
• Large-Capacity Boilers: D ≥ 75 T/h.

(D represents steam output per design specifications, measured in kg/s, kg/h, or tons/h.)

3.4 Classification by Water Circulation Method

• Natural Circulation Boilers (Drum Boilers)
• Forced Circulation Boilers
• Once-Through Boilers (No-Drum Boilers)

3.5 Classification by Fuel Combustion Method

- Grate-Fired Boilers: Solid fuels (coal, wood, bagasse, etc.) are burned on a fixed or moving grate.

- Pulverized Fuel Boilers: Liquid and gaseous fuels are sprayed, and solid fuels are pulverized into fine powder and burned in suspension.

- Special Combustion Boilers: Examples include cyclonic furnaces and fluidized bed boilers.

• Cyclonic Furnace: Cyclonic furnaces can burn raw or preliminarily ground coal. Fuel and air are introduced tangentially into the cylindrical combustion chamber at high velocity. Under the effect of centrifugal force, molten slag and larger fuel particles adhere closely to the furnace walls, forming layers that burn completely, layer by layer. Smaller coal particles, along with volatile substances, move toward the center and combust in the open space. Thus, the cyclonic furnace combines both layer combustion and spatial combustion.
• Fluidized Bed Boiler Furnace (Fluid Bed Furnace): In fluidized bed boiler furnaces, raw or preliminarily ground solid fuels are introduced and subjected to high-velocity air, causing them to oscillate within a defined space in the furnace. This process facilitates all stages of combustion. High-Temperature Fluidized Bed Furnace Operates at temperatures of 1,000°C or higher, where ash melts into slag, solidifies, and falls onto the grate for removal. Low-Temperature Fluidized Bed Furnace: Operates at approximately 800°C, effectively preventing the formation of nitrogen oxides (NOx). This type is highly efficient, avoiding ash melting by allowing ash particles to grind against each other and mix with added sand. The resulting fine dust is carried away with combustion products and captured by dedusting systems.

4. Popular Boiler Types

With over 30 years of expertise in boiler investment, operation, and maintenance, Thuan Hai proudly leads the industry in providing advanced boiler solutions for various industries. Here are some commonly applied boiler types:

4.1 Chain Grate Boiler

Chain Grate Boiler

Chain grate boilers use a moving grate system. These boilers burn fuel as it is carried along the grate. They are suitable for large-scale industrial applications requiring high heat.

4.2 Step Grate Combustion Boiler

 

Step Grate Combustion Boiler

Step grate combustion boiler is designed with interlocking step grates. These boilers provide efficient combustion and flexibility for various fuel types.

4.3 Fluidized Bed Boiler

Fluidized Bed Boiler

Fluidized bed boiler use a bed of sand, ash, or other materials for efficient fuel combustion. They maintain low combustion temperatures, reducing harmful gas emissions.

Thuan Hai customizes each boiler project to meet specific customer needs, ensuring outstanding performance and long-term sustainability.

Need boiler solutions for your business? Contact us today for expert advice and prompt support!

------------------------------------

References:

• Đặng Thành Trung. Giáo trình lò hơi. (2012). Vietnam: NXB Đại học Quốc gia TPHCM.
• PGS.TS Nguyễn Lê Dzần, TS. Nguyễn Công Hân. (2005). Công nghệ lò hơi và mạng nhiệt. Vietnam: NXB Khoa học và kỹ thuật.