The common heating methods of tunnel furnaces are as follows:
Electrically heated tunnel furnaces
Resistance heating: Resistance wires or resistance bands are installed inside the tunnel furnace. When an electric current passes through them, heat is generated by resistance, and the objects inside the furnace are heated through thermal radiation and thermal conduction. This heating method has a simple structure, relatively low cost, and precise temperature control. The heating areas and temperature distribution can be flexibly set according to needs. However, its heating efficiency is relatively low, and components such as resistance wires are prone to aging and damage under long-term high temperatures.
Electromagnetic heating: Based on the principle of electromagnetic induction, eddy currents are generated inside the object to be heated, thus producing heat. The electromagnetic heating method has the advantages of fast heating speed, high efficiency, significant energy-saving effects, and it can also achieve precise temperature control and good temperature uniformity. Nevertheless, its equipment cost is relatively high, and there are certain requirements for the material of the object to be heated.
Gas-heated tunnel furnaces
Natural gas heating: Using natural gas as fuel, a burner burns the natural gas to generate heat, and the items in the tunnel furnace are heated through thermal radiation and thermal convection. Natural gas heating has the advantages of high heating power, relatively low cost, and fast heating speed. However, it requires a stable natural gas supply system, and certain exhaust gas emissions will be generated during the combustion process. Corresponding ventilation and exhaust gas treatment equipment need to be equipped to ensure safety and environmental protection requirements.
Liquefied gas heating: Similar to natural gas heating, except that the fuel used is liquefied petroleum gas. Liquefied gas heating is suitable for some places where the natural gas pipeline cannot be accessed. However, attention should be paid to the storage and supply safety of liquefied gas. Its storage capacity is limited, and it is necessary to regularly replace gas cylinders or replenish the gas.
Oil-fired tunnel furnaces: Generally, heavy oil or diesel is used as fuel. The oil is atomized and burned by an oil burner to release a large amount of heat to heat the tunnel furnace. Oil-fired heating has relatively high calorific value and heating efficiency and can meet the needs of high-temperature heating. However, oil-fired heating will produce more pollutants, such as sulfur dioxide, nitrogen oxides, etc., causing certain pollution to the environment. Moreover, a special oil storage and supply system needs to be equipped, and the equipment maintenance cost is also relatively high.
Steam-heated tunnel furnaces: Using the steam generated by the boiler as a heat medium, the steam is introduced into the heat dissipation pipes or fins and other devices in the tunnel furnace, and the objects are heated through the heat released by the condensation of steam. Steam heating has the advantages of uniform and stable temperature, easy control, and the steam can be recycled, which is relatively energy-efficient. However, it is necessary to equip boiler and other steam generation equipment. The system is relatively complex, the initial investment is large, and at the same time, higher requirements are put forward for the thermal insulation and sealing of pipelines to reduce heat loss and prevent steam leakage.
Hot air circulation heated tunnel furnaces: This heating method is usually combined with other heat sources, such as electric heating, gas heating, etc. Through the fan, the air in the tunnel furnace forms a circular flow, and the heat generated by the heat source is evenly transferred to all parts of the furnace. Hot air circulation heating can improve the heating efficiency, make the temperature more uniform, and avoid local overheating or undercooling situations. However, it is necessary to reasonably design the air duct and fan layout to ensure the effect and energy efficiency of hot air circulation.
Henjiu Jinye in China specializes in the production of tunnel furnaces, and all kinds of tunnel furnaces can be customized according to non-standard requiremets
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