Low NOx burner and low NOx burner
Low NOx burner and low NOx burner, refers to the fuel combustion process of low NOx emissions of the burner, the use of low NOx burner can reduce the combustion process of NOx emissions.
The oxides of nitrogen produced in the combustion process are mainly NO and NO2, which are commonly referred to as NOx.A large number of experimental results show that the nox emitted by combustion devices is mainly NO, accounting for about 95% on average, while NO2 only accounts for about 5%.
The NO generated by general fuel combustion mainly comes from two aspects: one is the oxidation of nitrogen in the air used for combustion (combustion air);Second, the nitride contained in the fuel in the combustion process of thermal decomposition reoxidation.In most combustion devices, the former is the main source of NO, which is referred to as "thermal reaction NO", which is referred to as "fuel NO", and "instantaneous NO".
The formation of NO during combustion can react with nitrogen atom intermediates to reduce NO to NO2.In fact, in addition to these reactions, NO can combine with various nitrogenous compounds to form NO2.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, which can be ignored.
NOx reduction combustion technology
NOx is generated by combustion, and combustion methods and combustion conditions have a great impact on the production of NOx, so NOx can be reduced by improving combustion technology, the main way is as follows:
Choose fuel with low N content, including denitrification of fuel and conversion to low nitrogen fuel;
Reduce the excess coefficient of air, organize the over-dense combustion, to reduce the oxygen concentration around the fuel;
In the case of less surplus air, lower the peak temperature to reduce the "thermal reaction NO";
In the case of low oxygen concentration, increase the time of combustion in the front peak and reaction zone.
The specific methods commonly used to reduce the formation and emission of NOx are: fractional combustion, recombustion, low oxygen combustion, bias combustion and flue gas recycling.
Low nox burners are commonly used
Burner is an important equipment of industrial furnace, it ensures fuel stable ignition combustion and fuel complete combustion process, therefore, in order to inhibit the production of NOx must start from the burner.According to NOx reduction combustion technology, low NOx burner can be roughly divided into the following categories:
1.Stage burner
The stage burner is designed according to the principle of fractional combustion, so that the fuel and air can be mixed in different sections, because the combustion deviates from the theoretical equivalent ratio, the generation of NOx can be reduced.
2.Self recirculating burner
One is the use of combustion air pressure head, part of the smoke back into the burner, mixed with air combustion.Due to flue gas recycling, the heat capacity of combustion flue gas is large, the combustion temperature is reduced, and NOx is reduced.
Another kind of self-recirculating burner is to put part of the flue gas directly into the recirculation in the burner and add the combustion process.
3.Thick-light burner
The principle is that one part of the fuel is overburned and the other part is underburned, but the overall air volume remains the same.Because both parts are in the deviation from the chemical equivalent ratio combustion, and therefore NOx is very low, this combustion is also called deviation combustion or non-chemical equivalent combustion.
4.Split flame burner
The principle is to divide a flame into several small flames. Due to the large heat dissipation area of the small flame and the low temperature of the flame, the "thermal reaction NO" decreases.In addition, flame reduces the residence time of oxygen, nitrogen and other gases in the flame, and it has obvious inhibitory effect on "thermal reaction NO" and "fuel NO".
5.Hybrid accelerator burner
The residence time of flue gas in the high temperature area is one of the main factors affecting the production of NOx. Improving the mixing of combustion and air can reduce the thickness of the flame surface. Under the condition that the combustion load remains unchanged, the residence time of flue gas in the flame surface is shortened in the high temperature area, thus reducing the production of NOx.The hybrid accelerator burner is designed in this way.
6.Low NOx 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.
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