Views: 1980 Author: Site Editor Publish Time: 2022-09-06 Origin: Site
NOx generation of natural gas boiler is mainly thermal NOx, which can be controlled by controlling combustion temperature. The main control methods are as follows:
A) staged combustion
Staged combustion refers to the combustion technology in which the air and fuel required for combustion are fed into different parts of the combustion stroke to participate in combustion, so as to suppress the generation of NOx. It is divided into air staging and fuel staging.
Staged combustion is a common combustion technology to achieve the 80mg / m3 emission standard. Both methods reduce the peak value of heat release in time, prolong the reaction time and reduce the chemical reaction rate, so as to reduce the flue gas temperature.
The essence of staged combustion is diffusion combustion, which mainly reduces the flame temperature by expanding the flame surface area, thus reducing NOx. Therefore, the required furnace size is large, but it is not conducive to the reduction of boiler steel consumption and is difficult to be used in condensing boilers. It can not be applied to low nitrogen retrofitted boilers with small furnace size.
B flue gas recirculation (FGR)
FGR is to directly return 5% ~ 20% of the low-temperature flue gas produced by combustion to the furnace, or send it into the furnace after mixing with air. By reintroducing the burned flue gas into the combustion area, the combustion temperature and oxide concentration are reduced, and the generation of NOx is suppressed. FGR technology limits the formation of NOx by controlling the maximum temperature of the combustion zone. FGR technology can also reduce oxygen concentration and also play a role in denitration.
C) premixed combustion
The gaseous fuel and oxygen are premixed into a uniform mixture. The process of ignition and combustion of the premixed gas in the burner is called premixed combustion. Premixed combustion can adjust the mixing ratio so that the actual combustion temperature is lower than the theoretical combustion temperature and not higher than the critical temperature point of thermal NOx generation, thereby reducing the amount of thermal NOx generation.
At present, the fully premixed micro flame combustion technology is adopted by the relatively mature boiler metal fiber burner. However, this technology also has some problems, such as: easy to cause tempering, difficult to control the mixing rate, easy to temper if it is too high, poor effect if it is too low, and short service life of the surface combustion disc.
D) flameless combustion
Flameless combustion technology refers to a technology in which air and gas are fully mixed in advance before entering the combustion chamber, and the combustion speed is extremely fast. The whole combustion process basically occurs in the burner, and the flame is very short, or even no flame can be seen. Flameless combustion is a combustion state under low oxygen conditions, which is characterized by uniform overall thermal flow field distribution, small temperature gradient in the furnace, low combustion peak temperature and small NOx generation. In the flameless combustion process, the NOx concentration is controlled at a very low level because there is no local high temperature and high oxygen area in the traditional combustion mode.
The above is the answer of Jiangsu Sifang boiler to this question. If you have any doubts about other boiler related problems, please consult the online customer service of Jiangsu Sifang boiler or call 0516-85871846 or 0516-85532705. The professional technicians of Jiangsu Sifang boiler will answer your questions in time.