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.
The oxides of nitrogen produced in the combustion process are mainly NO and NO2, usually referred to as NOx.A large number of experimental results show that nox emissions from combustion devices are mainly NO, accounting for 95% on average, while NO2 only accounts for 5%.
The NO produced by general fuel combustion mainly comes from two aspects: first, the oxidation of nitrogen in the combustion air (combustion-supporting air);The second is the nitride in the combustion process in the thermal decomposition and reoxidation.In most combustion devices, the former is the primary source of NO, which we call "thermal reaction NO", the latter "fuel NO", and "instant NO".
NO formed during combustion can react with nitrogen-containing atomic intermediates to reduce NO to NO2.In fact, in addition to these reactions, NO can also form NO2 with various nitrogenous 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.
NOx reduction combustion technology
NOx is produced by combustion, and the combustion method and combustion conditions have a great impact on the generation of NOx. Therefore, NOx can be reduced by improving combustion technology. The main ways are as follows:
Selecting fuel with low N content, including denitrification of fuel and conversion to low-nitrogen fuel;
To reduce the excess coefficient of air and to reduce the oxygen concentration around the fuel;
In the case of less excess air, reduce the peak temperature to reduce "thermal reaction NO";
At low oxygen concentration, the duration of the fuel in the flame front peak and reaction zone is increased.
The specific methods commonly used to reduce NOx formation and emission are: fractional combustion, recombustion, low oxygen combustion, shade deviation combustion and flue gas recirculation.
General use of low nitrogen oxide burners brief
Burner is an important equipment of industrial furnace, it ensures the stable ignition combustion and complete combustion of fuel and other processes, therefore, to inhibit NOx production must be started from the burner.According to the NOx reduction combustion technology, low NOx burners can be roughly divided into the following categories:
1.Stage burner
The stage burner designed according to the principle of fractional combustion, so that fuel and air sectionally mixed combustion, due to the combustion deviation from the theoretical equivalent ratio, it can reduce NOx generation.
2.Self recirculating burner
One is the use of combustion air pressure head, part of the smoke inhalation back into the burner, and mixed with air combustion.Due to flue gas recirculation, combustion flue gas heat capacity, combustion temperature, NOx reduction.
Another kind of self-recirculating burner is to recycle part of the flue gas directly into the burner and add it into the combustion process. This burner has the dual effect of inhibiting nitrogen oxide and saving energy.
3.Shade burner
The principle is to make some fuel burn too intensely and some fuel burn too lightly, but the total amount of air above it remains the same.Since both parts burn at a deviating stoichoequivalence ratio, NOx is very low and this kind of combustion is also called deviating combustion or non-stoichoequivalence combustion.
4.Split flame burner
The principle is to divide a flame into several small flames. Due to the large heat dissipation area of small flames and the low flame temperature, the "thermal reaction NO" is somewhat reduced.In addition, small flame reduces the residence time of oxygen, nitrogen and other gases in the flame, and has an obvious inhibitory effect on both "thermal reaction NO" and "fuel NO".
5.Hybrid booster burner
Flue gas in the high temperature zone residence time is one of the main factors affecting NOx production, improve the combustion and air mixing, can make the flame surface thickness thin, in the case of the same combustion load, flue gas in the flame surface namely high temperature zone residence time is shortened, thus reducing NOx production.The hybrid booster burner is designed on this principle.
6.Low NOx precombustion chamber 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.
