Technology for reducing NOx emissions in low nitrogen burners

　　Low NOx burners and low NOx burners refer to burners with low NOx emissions during fuel combustion. The use of low NOx burners can reduce NOx emissions during combustion.7ibBoiler Burner

　　The oxides of nitrogen produced during combustion are mainly NO and NO2, which are commonly referred to as NOx.A large number of experimental results show that the nitrogen oxides emitted by combustion devices are mainly NO, accounting for about 95% on average, while NO2 only accounts for about 5%.7ibBoiler Burner

　　The NO generated by general fuel combustion mainly comes from two aspects: one is the oxidation of nitrogen in the air used in combustion (combustion air);The other is the thermal decomposition and reoxidation of nitrogen compounds in fuel during combustion.In most combustion devices, the former is the primary source of NO, which we call "thermal reaction NO", "fuel NO", and "instant NO".7ibBoiler Burner

　　NO formed during combustion can react with nitrogen-containing intermediates to reduce NO to NO2.In fact, in addition to these reactions, NO can form NO2 with a variety of nitrogen-containing compounds.When the reaction reaches chemical equilibrium in the actual combustion device, the ratio of [NO2]/[NO] is very small, that is, the conversion of NO to NO2 is very small and can be ignored.7ibBoiler Burner

　　NOx reduction combustion technology7ibBoiler Burner

　　NOx is produced by combustion, and combustion method and combustion conditions have a great impact on the generation of NOx, so NOx can be reduced by improving combustion technology, the main ways are as follows:7ibBoiler Burner

　　Choose low N content fuel, including fuel denitrification and conversion to low nitrogen fuel;7ibBoiler Burner

　　Reduce the excess coefficient of air and reduce the concentration of oxygen around the fuel by organizing the over-dense combustion.7ibBoiler Burner

　　In the case of less excess air, lower the peak temperature to reduce the "thermal response NO";7ibBoiler Burner

　　In the case of low oxygen concentration, increase the time of the fuel in the preflame peak and reaction zone.7ibBoiler Burner

　　The specific methods commonly used to reduce the formation and emission of NOx are: fractional combustion, recombustion, hypoxic combustion, bias combustion and flue gas recirculation.7ibBoiler Burner

　　Introduction to low nitrogen oxide burners commonly used7ibBoiler Burner

　　Burners are important equipment of industrial furnaces, which ensure the stable combustion of fuel and the complete combustion of fuel. Therefore, in order to suppress the production of NOx, it is necessary to start from burners.According to the NOx reduction combustion technology, low NOx burners can be divided into the following categories:7ibBoiler Burner

　　1.Stage burner7ibBoiler Burner

　　According to the stage burner designed based on the principle of staged combustion, fuel and air are mixed in sections for combustion, which deviates from the theoretical equivalent ratio, thus reducing the generation of NOx.7ibBoiler Burner

　　2.Self recirculating burner7ibBoiler Burner

　　One is to use the pressure head of the combustion air to suck part of the combustion flue gas back into the burner and mix it with the air for combustion.Due to the recirculation of flue gas, the heat capacity of flue gas is large, the combustion temperature is reduced, and NOx is reduced.7ibBoiler Burner

　　Another kind of self-recirculating burner is to put part of the flue gas into recirculation directly in the burner and add into the combustion process.7ibBoiler Burner

　　3.Shade burner7ibBoiler Burner

　　The principle is to make one part of the fuel overburn, another part of the fuel underburn, but the overall amount of air remains the same.Since both components burn at off-stoichiometric ratios, and thus have low NOx, this combustion is also known as off-stoichiometric or non-stoichiometric combustion.7ibBoiler Burner

　　4.Split flame burner7ibBoiler Burner

　　Its principle is to divide a flame into several small flames, due to the small flame heat dissipation area is large, the flame temperature is lower, so that the "thermal reaction NO" decreased.In addition, the small flame shortens the residence time of oxygen, nitrogen and other gases in the flame, which has obvious inhibitory effect on "thermal reaction NO" and "fuel NO".7ibBoiler Burner

　　5.Hybrid accelerator burner7ibBoiler Burner

　　The residence time of flue gas in the high temperature zone is one of the main factors affecting the production of NOx. Improving the mixture of combustion and air can reduce the thickness of the flame surface. Under the condition of constant combustion load, the residence time of flue gas in the flame surface, that is, in the high temperature zone, thus reducing the production of NOx.This is the principle behind the design of the hybrid - accelerator burner.7ibBoiler Burner

　　6.Low NOx precombustion chamber burner7ibBoiler Burner

　　Precombustion chamber development research in China in recent 10 years is a kind of high efficiency and grade of low NOx combustion technology, generally speaking, a precombustion chamber of the wind or secondary air and fuel injection system, etc, the mixed fuel and a wind, in a form in the combustion zone precombustion indoor fuel mixture, due to the lack of oxygen, is only part of the fuel combustion, fuel in poor oxygen and low flame temperature of a flame volatile precipitation in the area, thereby reducing NOx formation.7ibBoiler Burner