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Low-nitrogen burners are very popular in the market today, offering many advantages. They are particularly useful for boilers that need to be upgraded urgently. What is their working principle exactly? Low-NOx burners are burners that result in low NOx emissions during the fuel combustion process; by using such burners, it is possible to reduce the emission of nitrogen oxides during combustion. The nitrogen oxides produced during combustion are mainly NO and NO2; these two nitrogen oxides are generally referred to collectively as nitrogen oxides NOx. Numerous experimental results show that the nitrogen oxides emitted by the combustion device are mainly NO, accounting for about 95 on average, while NO2 accounts for only around 5%. The NO generated during normal fuel combustion mainly comes from two sources: one is the oxidation of nitrogen in the air used for combustion (oxidizing air) ； Second, the nitrides contained in the fuel undergo thermal decomposition and then re-oxidation during combustion. In most combustion devices, the former is the main source of NO; we refer to this type of NO as \"thermally generated NO\", while the latter is called \"fuel-derived NO\". There is also \"instantaneous NO\". The NO formed during combustion can react with nitrogen-containing intermediate products to reduce NO to NO2. In fact, in addition to these reactions, NO can also react with various nitrogen-containing compounds to form NO2. In a real combustion device, when the reaction reaches chemical equilibrium, the / ratio is very small; that is, very little NO is converted to NO2, and this can be ignored. Combustion technologies for reducing NOx: NOx is generated during combustion, and the combustion methods and conditions have a significant impact on the formation of NOx; therefore, NOx can be reduced by improving combustion technologies. The main approaches include using fuels with lower nitrogen content, as well as fuel denitration and conversion into low-nitrogen fuels ； Reduce the air excess factor and organize rich combustion in order to lower the oxygen concentration around the fuel ； With less excess air, the temperature peak is reduced to minimize \"thermally induced NO\"" ； At lower oxygen concentrations, increase the time that the combustible material remains in the flame front and reaction zone. Specific methods commonly used to reduce the formation and emission of NOx include staged combustion, reburning, low-oxygen combustion, lean-rich stratified combustion, and flue gas recirculation. Introduction to commonly used low-nitrogen oxide burners: Burners are essential equipment in industrial furnaces; they ensure stable ignition of the fuel as well as its complete combustion. Therefore, to reduce the generation of NOx, it is necessary to focus on the burners themselves. Based on combustion technologies for reducing NOx, low-NOx burners can be roughly classified into the following categories: 1. Low-NOx premix chamber burners. The premix chamber is a high-efficiency, low-NOx staged combustion technology that has been developed and researched in China over the past decade. It generally consists of primary air (or secondary air) and a fuel injection system; the fuel mixes rapidly with the primary air, forming a fuel-rich mixture in the primary combustion zone within the premix chamber. Due to the lack of oxygen, only part of the fuel burns. The volatiles in the fuel are released in the primary flame zone, where the oxygen level is low and the flame temperature is low, thereby reducing the formation of NOx. 2. Staged burner: A staged burner designed based on the principle of staged combustion, which allows for the mixed combustion of fuel and air in stages; since the combustion deviates from the theoretical equivalence ratio, this helps to reduce the formation of NOx. 3. The self-recirculating burner is a type that uses the pressure of the combustion air to draw back a portion of the combustion flue gases into the burner, where they mix with the air and burn. Due to flue gas recirculation, the heat capacity of the combustion flue gas increases, the combustion temperature decreases, and NOx is reduced. Another type of self-recirculating burner is one in which a portion of the flue gas is directly recirculated within the burner and incorporated into the combustion process; such burners offer the dual benefits of reducing nitrogen oxides and saving energy. 4. The principle of the rich-lean burner is to allow part of the fuel to burn in a rich condition while another part burns in a lean condition, with the overall air volume remaining constant. Since both parts burn at a deviation from the stoichiometric ratio, the NOx levels are very low; this type of combustion is also known as deviated combustion or non-stoichiometric combustion. 5. The principle of the segmented flame burner is to divide one flame into several smaller flames. Since these smaller flames have a larger heat dissipation area, their temperature is lower, which results in a reduction in \"thermally generated NO\". Furthermore, the smaller flame length shortens the residence time of gases such as oxygen and nitrogen within the flame, exerting a significant inhibitory effect on both \"thermally generated NO\" and \"fuel-derived NO\". 6. The residence time of flue gas in the high-temperature zone in a mixed-promotion type burner is one of the main factors affecting NOx generation. Improving the mixing of fuel and air allows the flame front to become thinner; with the combustion load remaining unchanged, the residence time of the flue gas in the flame front, i.e., in the high-temperature zone, is reduced, thereby lowering NOx production. Mixed-promoting burners are designed based on this principle.