Innovation of industrial furnace combustion technology

Industrial furnaces are mainly divided into smelting casting and heat treatment furnace two types. The former is used for refining and smelting casting, while the latter is used for heating and heat treatment of billets before processing. Most of the fuel used for metal heating is natural gas or city gas, which must be fed into the air by air blower to support combustion. 

As we all know, the air is composed of nitrogen, which accounts for 78%, and oxygen, which accounts for 21% (and about 1% of the noble gases). Nitrogen, which has no combustion effect, becomes a drag, which not only delays the heating speed, but also takes away the heat in the flue gas, adding to the environmental problems. After years of research and development, The Linde Group of Germany has invented The low-temperature pure oxygen combustion technology (LTOF), which is suitable for smelting, melting casting and heat treatment of non-ferrous metals such as steel, copper and aluminum.

1. Introduction of low temperature pure oxygen combustion technology (LTOF) in industrial furnace

The main effects of pure oxygen combustion technology are:

(1) No nitrogen enters the furnace;

(2) No nitrogen removes heat in the flue gas;

(3) Iincrease the efficiency of radiation heat transfer;

(4) The flue gas stays longer in the furnace, so as to improve the heat transfer effect;

(5) Since there is no nitrogen in combustion supporting gas, it has little impact on environmental protection when discharged;

(6) The combustion supporting effect of pure oxygen reaches 77%, while the atmospheric combustion supporting rate is only 23%.

2. Advantages of low temperature pure oxygen burner (LTOF) flame in industrial furnace

The objective of low temperature pure oxygen combustion (LTOF) technology development is to improve the melting capacity and efficiency of reflector. The unique LTOF burner allows the flue gas from the entrainment furnace to enter the burner mixing zone, diluting the oxygen concentration at the front of the burner and slowing down the rate of combustion reaction, resulting in a lower flame temperature that is close to the flame of air-fuel combustion. 

This LTOF pure oxygen combustion flame characteristics make the temperature in the furnace more uniform, eliminate local hot spots, reduce fuel consumption, reduce flue gas emissions and improve metal recovery rate. Comparison between air combustion and low-temperature pure oxygen combustion, among which, air combustion, burner power is 311kW, water cooling is 231kW, the average constantly measured in molten aluminum is 1131℃, and heat flux is 79kW/m2.Low-temperature pure oxygen combustion, burner power 257kW, water cooling 66kW, continuous measurement of aluminum in the average value of 1152℃, heat flux 79kW/m2.

3. Flame form of LTOF low-temperature pure oxygen burner in industrial furnace, flame free combustion is the most effective

(1) Can reduce NOx emission by 90%;

(2) Compared with regenerative or ordinary pure oxygen combustion, flameless combustion is the least sensitive to air leakage, and there is no significant change in NOx production. The average energy consumption and thermal balance of LTOF pure oxygen combustion technology in 28t aluminum alloy melting reflector.