Hot Blast Furnace Industry

Sep,10 2025

Hot Blast Furnace System Introduction

A hot air boiler is a thermal energy device that transfers heat from fuel combustion to air to generate clean hot air. This system typically consists of a boiler, industrial burner, heat exchanger, fan, and control system. It is widely used in industries such as chemical, food, pharmaceutical, textile, metallurgy, and building materials, primarily for material drying, workshop heating, and process heating. Its core feature is indirect heating through a heat exchanger, ensuring clean, pollution-free hot air output. It also offers advantages such as high efficiency, energy saving, and intelligent control.

Working Principle

The hot air boiler process primarily involves three stages: fuel combustion, heat transfer, and hot air output.

Fuel Combustion

The fuel (coal, natural gas, biomass, etc.) is mixed with air in the combustion chamber and ignited, producing high-temperature flue gas (typically 800-1000°C).

During the combustion process, the air-to-coal ratio or gas supply is adjusted to ensure complete combustion and reduce pollutant emissions.

Heat Transfer

Direct Heating: High-temperature flue gas is directly mixed with air, achieving a thermal efficiency exceeding 95%. However, the hot air contains combustion exhaust gases and is only suitable for applications with low air quality requirements (such as ore drying).

Indirect Heating: The flue gas transfers heat to the air through a heat exchanger (tubular or plate). This results in highly clean hot air and is suitable for industries such as food and pharmaceuticals. The use of multi-head spiral grooved plate heat exchange technology and turbulent flow principles enhances heat transfer, with a thermal efficiency typically reaching 80%-92%. Hot Air Output

The heated air is delivered to the target device via a fan. The temperature can be adjusted via a control system, covering low (60-150°C), medium (200-300°C), and high (400-600°C).

Structural Composition

The hot air boiler is primarily composed of the following core components:

System	Key Components	Function
Combustion System	Combustion chamber, burner, fuel supply device	Achieve efficient fuel combustion and generate high-temperature flue gas
Heat Exchange System	Tubular/plate heat exchangers, finned tubes	Transfer heat to the air to ensure clean hot air
Air Supply System	Blowers, induced draft fans, air ducts	Provides cool air and delivers hot air to target equipment
Control System	PLC controller, temperature sensor, pressure monitoring device	Automatically adjust combustion parameters to maintain stable hot air temperature (±5°C)
Smoke Exhaust System	Chimney, dust collector	Emit flue gas and reduce dust pollution

Classification and Technical Characteristics

Type	Fuel	Thermal Efficiency	Advantages	Applicable Scenarios
Coal-fired hot air stove	Bituminous coal, anthracite	70%~85%	Low fuel cost, suitable for large-scale heating	Metallurgy and building materials drying
Gas hot air furnace	Natural gas, liquefied gas	90%~98%	Clean and environmentally friendly, with a high degree of automation	Food processing, pharmaceutical drying
Biomass hot air stove	Wood chips, rice husks, pellet fuel	75%~85%	Renewable energy, low carbon emissions	Agricultural drying, biomass power plants
Oil-fired hot air furnace	Diesel, heavy oil	85%~92%	High calorific value, suitable for areas without gas supply	Temporary heating, mobile heating equipment

Classification by Structural Form

Top-Fired Hot Air Furnaces

Catenary Dome Design: Utilizes multi-layered, high-swirl burners, achieving nitrogen oxide emissions below 50 ppm and air temperatures exceeding 1250°C.

Four-Stage Structure: Optimizes furnace shell stress, eliminates cracking issues associated with traditional furnace shells, and extends service life to over 20,000 hours.

Horizontal/Vertical Hot Air Furnaces

Horizontal: Offers a large footprint and a wide heat exchange area, suitable for medium- and large-scale industrial applications.

Vertical: Compact and easy to install, suitable for small- and medium-sized heating needs (e.g., the RFL series vertical cylindrical hot air furnaces).

Technical Parameters and Selection Guide

Parameter	Explanation	Typical Range
Output Thermal Power	Heat provided per unit time	0.7~100 MW
Hot Air Temperature	Outlet hot air temperature	60~600℃
Fuel Consumption	Hourly fuel consumption	Coal: 10~1500 kg/h, gas: 5~500 m³/h
Thermal Efficiency	Ratio of available heat to total heat of fuel	70%~98%
Air Volume	Hot air output per hour	500~50000 m³/h

Selection Considerations

Determine heat requirements: Calculate the required heat output and temperature based on the heating area and material moisture content.

Fuel compatibility: Prioritize local, inexpensive fuels (e.g., biomass furnaces in biomass-rich areas).

Environmental protection requirements: Select low-nitrogen burners (e.g., gas furnaces with NOx emissions <30mg/m³) in areas with high environmental protection requirements.

Automation level: For continuous production, it is recommended to equip the system with a PLC control system to enable unmanned operation.

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