1. Equipment Composition
The unit consists of feeding device, discharging device, furnace body, combustion chamber, material conveying mechanism, electric control system and other components.
2. Applied Process
Hot air drying
3. Heating Fuel
Natural gas
4. Processed Products
Internal coating of steel pipes such as petroleum drill pipes and oil tubes
Main Features
Equipped with shifting fork type material conveying mechanism, the steel pipes can roll freely at a set angle to ensure uniform heating. Combined with variable-frequency circulating fan and specially optimized air duct design, the temperature uniformity of steel pipes reaches ±5℃.
The combustion system adopts linear burner for more stable power output.
The equipment applies distributed control system with high automation degree, realizing unattended operation for the whole production process.
Main Classification Methods & Core Differences
2.1 Classified by Hot Air Cleanliness (Heat Exchange Structure)
(1) Direct-fired Hot Air Furnace
Working principle: After complete fuel combustion, high-temperature flue gas is directly mixed with fresh cold air to form output hot air.
• Advantages: No heat exchange loss, thermal efficiency 90%~95%, compact structure, fast temperature rise and low initial investment.
• Disadvantages: The hot air contains combustion soot and nitrogen oxides with pollution risks.
• Application scenarios: Building material drying, mine space heating, primary processing of agricultural and sideline products, and other occasions with no strict cleanliness requirements.
(2) Indirect Heat Exchange Hot Air Furnace
Working principle: Flue gas and fresh air are completely isolated, heat is transferred through the wall of metal heat exchangers. Flue gas is discharged separately, and clean hot air is output.
• Advantages: Dust-free and impurity-free hot air, specially used for high-cleanliness processes such as food, medicine and lithium batteries.
• Disadvantages: There is heat exchange temperature difference loss, thermal efficiency 75%~85%, heavier equipment weight and higher initial investment.
• Subtypes: Sleeve type, tube bundle type and heat pipe type heat exchangers.
(3) Regenerative Hot Air Furnace (Special for Blast Furnace)
Working principle: Periodic cycle mode: combustion heat storage → cold air heat exchange air supply. Heat is stored in checker bricks or heat storage balls, and multiple furnaces work alternately to realize continuous air supply.
• Advantages: High waste heat recovery efficiency, hot air temperature up to 1300℃, suitable for large-scale metallurgical blast furnaces.
• Disadvantages: Huge overall structure, high maintenance cost of refractory materials, requiring multiple furnaces connected in parallel.
• Main subtypes: Internal combustion type, external combustion type and top combustion type (mainstream new type).
2.2 Classified by Fuel & Heating Energy Source
Type Fuel / Heat Source Core Characteristics
Gas-fired Hot Air Furnace Natural gas, liquefied petroleum gas, blast furnace gas Clean and low nitrogen, precise temperature control, high automation
Oil-fired Hot Air Furnace Diesel oil, heavy oil No pipeline dependence, suitable for remote factory areas
Coal / Biomass Hot Air Furnace Coal, wood chips, straw pellets Low fuel cost for large-scale drying; supporting dust removal environmental protection equipment is required
Electric Heating Hot Air Furnace Resistance tube / electromagnetic induction Zero flue gas emission, temperature control accuracy ±1℃, preferred for areas with strict environmental supervision
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