What Is Horizontal Fire Tube Boiler

The horizontal fire tube boiler is the most common type of industrial boiler, which has the advantages of compact structure, small footprint, and high thermal efficiency, and is widely used in petrochemical, pharmaceutical, textile, food processing, and other industries. When you want to explore and find the right steam boilers for your specific application. You will face many problems as follows.

  • What Is A Horizontal Fire Tube Boiler?
  • What are the different types of Horizontal fire tube boiler?
  • What are the Advantages and disadvantages of Horizontal Fire Tube boilers?
  • What are the specific cases of horizontal fire tube boilers?

EPCB Boiler specializes in the design and production of industrial boilers and pressure vessels with 70+ years of experience. In this paper, the definition, working principle, structure, advantages and disadvantages, and types of horizontal fire tube boiler are introduced in detail, and its comprehensive evaluation is carried out.

1. What Is Horizontal Fire Tube Boiler

A horizontal fire tube boiler is a type of boiler commonly used to generate steam or hot water. It features a cylindrical shell that is filled with water.
The unique characteristic of this boiler is its horizontal arrangement, with the combustion chamber located in the lower part. The combustion medium, such as fuel or gas, is burned in the combustion chamber, generating hot gas. The heat is then transferred inside the boiler through the fire tube.
This design allows for efficient heat transfer and is suitable for smaller applications such as heating homes or businesses. In contrast, water-tube boilers are more commonly used for larger applications, such as generating steam for power plants.

What Is Horizontal Fire Tube Boiler

2. What Is The General Structure of Horizontal Fire Tube Boiler?

Horizontal fire tube boiler mainly consists of the following parts:

2.1 Furnace

The furnace is the combustion chamber, located in the lower part of the boiler, used to burn fuel. It is a specially designed combustion chamber where fuel, such as natural gas, oil, or coal, is burned to produce heat. The primary function of the furnace is to generate high temperatures by igniting and burning the fuel. This combustion process releases a significant amount of heat energy, which is then transferred to the boiler’s hot water or steam.
The furnace is constructed with refractory materials that can withstand the extreme temperatures generated during combustion. The furnace’s combustion chamber is designed to optimize the combustion process, ensuring maximum heat output while minimizing emissions. This is achieved by controlling the air-to-fuel ratio, maintaining proper airflow, and providing sufficient turbulence for the thorough mixing of fuel and air. Its efficient operation is essential for horizontal fire tube boilers to achieve optimal performance and ensure reliable and consistent heating.

2.2 Fire Tube

The fire tube is the core component of the horizontal fire tube boiler and is composed of multiple tubes, usually in the form of straight or curved tubes. The fire tube connects the furnace to the cylinder and is responsible for transferring heat.
In a horizontal fire tube boiler, the fire tube is where the combustion gases pass through. It is located inside the boiler shell and is surrounded by water. The combustion gases generated in the furnace travel through the fire tube, heating the water surrounding it.
The fire tube is typically made of steel and can be straight or curved, depending on the design of the boiler. Straight tubes are commonly used in smaller boilers, while curved tubes are employed in larger boilers to increase the heating surface area. As threaded smoke pipe, internal and external double threads, can increase the heating surface, produce flue gas turbulence, and improve the boiler thermal efficiency.
The fire tube is an essential component of the boiler as it maximizes the contact area between the hot gases and the water, ensuring efficient heat transfer and steam generation.

2.3 Boiler Drum

The boiler drum is the main part of the fire tube boiler, holding water and steam. It is usually located above the fire tube and connects the furnace to the flue. Water is stored in the boiler drum, where it is heated and converted into steam. The drum’s large capacity allows for a significant amount of water to be stored, ensuring a continuous supply of steam.

2.4 Flue

The flue is typically positioned at the top of the cylinder, chimney, or venting system, allowing the hot gases to rise and exit through it. It is designed to create a pathway for the gases to escape while preventing them from re-entering the living space.
In addition to removing harmful gases, the flue also helps in maintaining proper airflow for combustion. It draws in fresh air from the surrounding environment, providing oxygen for the combustion process, and expels the resulting exhaust gases.

Structure-of-Horizontal-Fire-Tube-Boiler

3. What Is The Working Principle of Horizontal Fire Tube Boiler

The working principle of the horizontal fire tube boiler is that the high temperature flue gas generated by combustion transfers heat to the water inside the fire tube so that it becomes steam or heated water.
3.1 Fuel combustion: The fuel is burned in the furnace, producing high temperature flue gas.
3.2 Flue gas heat transfer: The flue gas passes through the fire tube and exchanges heat with the water outside the fire tube. The high temperature heat of the flue gas is transferred to the water supply through the fire tube wall, which increases the water temperature.
3.3 Steam or heated water generation: Through a series of heat transfer processes, water is heated to a certain temperature and becomes steam or heated water.
3.4 Steam or heated water utilization: Steam can be used to drive mechanical equipment or carry out industrial production processes such as heating and power generation; Heated water can be used for heating, bathing, and other fields.
3.5 Flue gas emission: The exhaust gas produced by combustion is discharged into the atmosphere through the flue.

4. What are The Different Types of Horizontal Fire Tube Boiler?

4.1 Cornish Boiler

the Cornish boiler is a type of horizontal fire tube boiler. It features a cylindrical shell with a single large flue that runs through the center. The firebox is located at one end of the boiler, and the flue gases pass through the flue and then through a series of tubes before exiting the boiler through a chimney. This design allows for efficient heat transfer and combustion.

4.2 Locomotive Boiler

The Locomotive boiler is the second type of horizontal fire tube boiler. It is specifically designed for use in locomotives and is characterized by its cylindrical shape and horizontal orientation. The firebox is located at one end of the boiler, and the flue gases pass through a series of fire tubes that run through the boiler shell before exiting through a smokebox at the other end. This design allows for efficient heat transfer and steam production.

4.3 Scotch Marine Boiler

The Scotch marine boiler is one of the most common types of boilers used in ships and industrial applications. The Scotch marine boiler is characterized by its cylindrical shell with two or more large flue tubes running through it. These flue tubes are surrounded by water, and the hot gases from the combustion process pass through them, heating the water and generating steam. The Scotch marine boiler is known for its robust construction, high efficiency, and ability to handle high pressures.

4.4 Horizontal Return Tubular Boiler

The Horizontal Return Tubular (HRT) boiler is one of the oldest and most basic types of horizontal fire tube boilers. The HRT boiler consists of a cylindrical shell, horizontally mounted with a large number of fire tubes. These fire tubes run through the boiler’s drum, which is filled with water. The hot gases from the combustion process pass through the fire tubes, heating the water surrounding them and generating steam. The steam is then collected in the steam drum at the top of the boiler. The HRT boiler is known for its simplicity, durability, and ease of maintenance.

5. What Are The Advantages And Disadvantages of Horizontal Fire Tube boilers?

5.1 The disadvantages of Horizontal Fire Tube boilers

5.1.1 Limited Steam Pressure: Horizontal fire tube boilers typically have lower steam pressure capabilities compared to water tube boilers. This may limit their suitability for high-pressure applications.
5.1.2 Lower Efficiency: Horizontal fire tube boilers generally have lower thermal efficiency compared to water tube boilers. This means that they may consume more fuel to generate the same amount of steam.
5.1.3 Prone to Scaling: Horizontal fire tube boilers can be more prone to scaling due to the accumulation of impurities in the water. Regular maintenance and water treatment are necessary to prevent scaling and maintain boiler efficiency.
5.1.4 Limited Capacity: Horizontal fire tube boilers are typically limited in terms of steam generation capacity compared to larger water tube boilers. They may not be suitable for applications that require high steam output.

5.2 The Advantages of Horizontal Fire Tube boilers

5.2.1 Compact Design: Horizontal fire tube boilers have a compact design, making them suitable for small spaces or installations where vertical boilers may not be feasible.
5.2.2 Easy Maintenance: The horizontal arrangement of fire tubes allows for easy access and maintenance of the boiler components.
5.2.3 Quick Steam Generation: Horizontal fire tube boilers have a relatively fast startup time and can generate steam quickly, making them suitable for applications that require immediate steam supply.
5.2.4 Cost-Effective: Horizontal fire tube boilers are generally cost-effective compared to other types of boilers, making them a popular choice for small to medium-sized industries.

Vertical Horizontal Fire Tube Boiler Customer Case

6. What Is The Difference Between Vertical and Horizontal Fire Tube Boilers?

There are two main types of fire tube boilers: horizontal and vertical fire tube boilers. Horizontal fire tube boilers are the most common type and are typically used for residential and commercial applications. Vertical fire tube boilers are less common but are used in some industrial applications.

Horizontal fire tubes are otherwise more efficient than vertical. For that reason, and to avoid the problems of tube erosion with exposed vertical tubes, many of the multi-tubular vertical boilers were instead arranged with their tubes horizontal.

6.1 Layout Structure

The layout structure of the horizontal boiler is that the furnace and the combustion chamber are at both ends of the furnace body, and the flue is at the top, while the combustion chamber and the flue of the vertical boiler are separate, and the heat needs to be transferred between the pipes.

6.2 Scope of Application

The horizontal boiler is suitable for heating and washing in families and small enterprises because this boiler not only has fast heating speed and good thermal insulation performance but also can meet the gas needs of ordinary families and small enterprises. The vertical boiler is suitable for larger industrial enterprises because the output power of the vertical boiler is larger, the heat exchange efficiency is higher, and it is suitable for large industrial processing and production needs.

6.3 Thermal Efficiency

Horizontal boiler has ultra-high thermal efficiency, complete combustion, rapid heating, and high combustion efficiency, so they use more gas saving and high safety; The vertical boiler is relatively low, which needs to be adjusted during operation, and the combustion efficiency is low.

6.4 Space Occupancy

Horizontal boiler space occupation is relatively small and suitable for limited environmental occasions. Vertical boiler space occupation is relatively large, suitable for space restrictions are not high occasions.

7. What Is The Difference Between Fire Tube Boiler and Water Tube Boiler?

The main difference between a fire tube boiler and a water tube boiler is the design of the heat exchanger. In a fire tube boiler, the hot gases generated by the combustion process flow through the tubes and transfer heat to the surrounding water. The water is then heated and circulated through the boiler for steam generation. In a water tube boiler, the water flows inside the tubes and is heated by the hot gases on the outside. The heat transfer occurs through the walls of the tubes, resulting in the generation of steam inside the tubes.
3.4.1 Pressure: Fire tube boilers typically operate at lower pressures. compared to water tube boilers, which can operate at higher pressures.
3.4.2 Efficiency: Water tube boilers generally have higher efficiency due to their larger heating surface area and better heat transfer characteristics. Fire tube boilers may have lower efficiency due to the smaller heating surface area and higher heat losses through the flue gases.
3.4.3 Size and Space Requirements: Fire tube boilers are generally smaller and require less space compared to water tube boilers, making them suitable for compact installations.
3.4.4 Response to Load Changes: Water tube boilers have a faster response time to load changes compared to fire tube boilers. This is because the water inside the tubes can quickly absorb and transfer heat, allowing for faster steam generation.
Overall, both fire tube and water tube boilers have their advantages and disadvantages, and the choice between them depends on various factors such as the application, required steam capacity, space availability, and efficiency requirements.

Best Horizontal Fire Tube Boiler Manufacturers

8. What Are The Specific Cases of Horizontal Fire Tube Boilers?

WNS is one of the most typical horizontal fire tube boilers in EPCB boilers. Taking this as an example, the horizontal fire tube boiler is introduced in detail.

8.1 A general introduction to EPCB horizontal boiler

WNS is a kind of boiler shell wet back type horizontal fire tube boiler. It has strong adaptability to different fuels and can burn heavy oil, light oil, natural gas, and city gas. Low power consumption, large load regulation ratio. The boiler adopts fully automatic control and has good adaptability to the burner. Imported original burner, reliable performance, high degree of automation.

8.2 Design concept of EPCB horizontal boiler

Abandon the traditional domestic design idea of a one-sided combustion chamber, and adopt the latest international concept – first select the burner and then design the combustion chamber according to the flame parameters of the burner, so that the flame profile and the combustion space are fully matched. Thus, the following three purposes are achieved:

  • Compared with the large combustion chamber structure, heat transfer is more carried out by heat conduction, rather than convective heat transfer with lower efficiency, which improves the heat exchange efficiency of the boiler.
  • Compared with the large combustion chamber structure, the steam and water space of the boiler is increased as much as possible without increasing the volume of the boiler. The increase in the boiler water space makes the actual evaporation of the boiler greater than the rated evaporation (overload capacity), so even if the steam demand suddenly increases, the boiler can also run stably. The increase in the steam space of the boiler makes the water in the steam can be better separated, ensuring that the dryness of the steam is more than 99%.
  • Inherited the advantages of the large combustion chamber structure, that is, the fuel combustion is full and complete, and the inner wall of the combustion chamber does not easily accumulate carbon, which not only avoids fuel waste but also ensures the stable operation of the boiler.

8.3 Characteristics of EPCB horizontal boiler

  • The classic structure of (flue gas) three-way (combustion chamber) full wet back is adopted.
  • A mixed type furnace with corrugated and straight sections is adopted. After calculation and reasonable combination of mixed furnace furnace can not only keep the advantages of pure corrugated furnace furnace furnace to enhance heat transfer but also avoid the shortcomings of non-synchronous expansion of pure corrugated furnace furnace furnace with boiler barrel and smoke pipe.
  • The second return of flue gas adopts an internal thread flue pipe. The inner wall of the threaded pipe can strongly disturb the flow state of the flue gas (from laminar flow to turbulent flow), which greatly enhances the heat transfer effect and improves the thermal efficiency of the boiler.
  • Light wall smoke pipe is used for the third return of flue gas. If the third return pipe is also used, although the heat transfer effect can be enhanced (limited), it also increases the smoke path resistance of the boiler.
  • Built-in high performance steam and water separator. The presence of steam and water separators further reduces the moisture content of the steam and ensures the output of high-quality steam.
  • The welding structure of open bevel butt welding is adopted.
  • A 120mm thick insulation layer is made of high density heat resistant fiber. Good thermal insulation performance, less heat dissipation loss, boiler body surface temperature is much lower than similar products.
  • The outer material is a stainless steel plate. Compared with the paint type outsourcing, it has the characteristics of strong corrosion resistance, beautiful appearance, no explosive paint, and enduring.
  • The front and rear smoke boxes of the boiler adopt the internationally popular double-layer sealing technology. The seamless cooperation of the two-layer sealing structure can ensure that the sealing rate of the smoke box reaches 100%.
  • The smoke box is equipped with a drainage device (domestic first). The drainage device can quickly remove the acidic liquid to avoid its corrosive effect on the tube plate.
  • The smoke box door adopts a twisted shaft structure. So that a single person can realize its free opening and closing, greatly facilitating the daily maintenance and maintenance work.
  • The smoke box door and the burner mounting cylinder are arranged in split type.
  • An inspection door equipped with a fire viewing device is provided at the rear of the boiler.
EPCB Horizontal-Fire-Tube-Boiler-Manufacturer

9. Conclusion

As an important thermal energy equipment, horizontal fire tube boiler has a wide application prospect in industrial and civil fields. However, due to its special structure, there are also some disadvantages. In practical application, it is necessary to select the appropriate type according to the specific working condition requirements. With the continuous progress of science and technology and the increase of demand, horizontal fire tube boilers will continue to develop and improve to meet the needs of different fields.
As the leading industrial boiler manufacturer and supplier, EPCB Boiler should strengthen the research and development of electric, gas, oil, coal and biomass  fired steam boilers, improve their thermal efficiency and environmental protection performance, and promote its sustainable development in the field of energy.
Any questions, please contact us.

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