My country's boiler air pollutant emission standards have basically gone through three stages: control of smoke and dust, control of SO2, and control of NOX. With the transformation of the national energy structure and industrial upgrading, the government is vigorously promoting the use of clean energy such as natural gas. Low nitrogen emissions from gas-fired boilers have become The new requirements of the new era.
According to the main measures to control NOX emissions, they can be divided into two categories according to different control links:
The first category is to control the generation of NOX. By reducing the temperature of the combustion high-temperature zone and narrowing the distribution range of the high-temperature zone, the most effective and simple way to control nitrogen oxides in the gas boiler industry is mainly the combustion control method. Mainly by optimizing the combustion conditions in the furnace, rationally optimizing the mixture of fuel and air, controlling the flame distribution, and reducing the temperature in the furnace to reduce the production of nitrogen oxides. The common methods are as follows:
air staged combustion
The air required for combustion is mixed with fuel in stages to reduce the combustion intensity and flame temperature. The outlet velocity of the secondary air supply is very high, sweeping the surrounding flue gas, making the flue gas recirculate in the furnace. On the one hand, the graded air distribution reduces the temperature of the central flame, and on the other hand, it dilutes the oxygen concentration on the flame surface, thereby inhibiting the formation of NOX.
Flue Gas Recirculation Technology (FGR)
Flue gas recirculation technology refers to leading part of the flue gas after combustion (mainly water vapor, carbon dioxide and nitrogen) back to the burner, where it is mixed with fresh air to participate in combustion. The temperature of the recirculated flue gas is much lower than the flame temperature in the furnace, which can significantly reduce the temperature in the furnace and reduce the heat intensity of the furnace volume. At the same time, since the oxygen content of the introduced flue gas is extremely low, the oxygen concentration in the furnace can be effectively reduced and the formation of NOx can be effectively suppressed.
Water Cooled Combustion Technology
The flame of the burner is surrounded by cooling water pipes, and the cooling water passing through the cooling water pipes takes away heat and reduces the flame temperature, thereby destroying the conditions for the formation of nitrogen oxides. Usually used together with premixed combustion technology, premixed combustion can effectively reduce the length of the flame, and the shorter flame can be fully cooled by the cooling water pipe, which can effectively reduce the concentration of NOx emissions.
Fully premixed wire mesh surface combustion
Fully premixed combustion refers to the precise proportion premixing of fuel and all required combustion air before combustion. During the whole combustion process, the air-fuel ratio can be kept constant in real time. The porous metal fiber mesh made of iron-chromium-aluminum and rare metal materials is the combustion surface, the pores are evenly distributed, and the combustion intensity is high. After the gas and air are precisely mixed, short cluster flames are generated on the surface, and the combustion area is large. Combustion is uniform, there is no local high temperature zone, and the formation of NOx is effectively suppressed.
The second category is flue gas denitrification technology, that is to say, to process the NOX already produced in the flue gas. The main related technologies are: precious metal catalytic denitrification method, selective catalytic reduction method (SCR), selective non-catalytic reduction method (SNCR) ), lye absorption method, etc.
To achieve ultra-low nitrogen oxide emissions within 30mg/m3, it is difficult to achieve with a single technology, but it is often easier to achieve with two low-nitrogen combustion technologies:
1) Flue gas internal circulation (FIR), NOx emission can be as low as 19mg/Nm³
2) The original imported burner is used, and the quality is reliable
3) Adapt to multi-type boilers, and the success rate of transformation and review is 100%
4) The burner is stable in operation, safe in use and low in maintenance cost
5) Staged combustion technology, low nitrogen without reducing boiler combustion efficiency
My country's boiler air pollutant emission standards have basically gone through three stages: control of smoke and dust, control of SO2, and control of NOX. With the transformation of the national energy structure and industrial upgrading, the government is vigorously promoting the use of clean energy such as natural gas. Low nitrogen emissions from gas-fired boilers have become The new requirements of the new era.
According to the main measures to control NOX emissions, they can be divided into two categories according to different control links:
The first category is to control the generation of NOX. By reducing the temperature of the combustion high-temperature zone and narrowing the distribution range of the high-temperature zone, the most effective and simple way to control nitrogen oxides in the gas boiler industry is mainly the combustion control method. Mainly by optimizing the combustion conditions in the furnace, rationally optimizing the mixture of fuel and air, controlling the flame distribution, and reducing the temperature in the furnace to reduce the production of nitrogen oxides. The common methods are as follows:
air staged combustion
The air required for combustion is mixed with fuel in stages to reduce the combustion intensity and flame temperature. The outlet velocity of the secondary air supply is very high, sweeping the surrounding flue gas, making the flue gas recirculate in the furnace. On the one hand, the graded air distribution reduces the temperature of the central flame, and on the other hand, it dilutes the oxygen concentration on the flame surface, thereby inhibiting the formation of NOX.
Flue Gas Recirculation Technology (FGR)
Flue gas recirculation technology refers to leading part of the flue gas after combustion (mainly water vapor, carbon dioxide and nitrogen) back to the burner, where it is mixed with fresh air to participate in combustion. The temperature of the recirculated flue gas is much lower than the flame temperature in the furnace, which can significantly reduce the temperature in the furnace and reduce the heat intensity of the furnace volume. At the same time, since the oxygen content of the introduced flue gas is extremely low, the oxygen concentration in the furnace can be effectively reduced and the formation of NOx can be effectively suppressed.
Water Cooled Combustion Technology
The flame of the burner is surrounded by cooling water pipes, and the cooling water passing through the cooling water pipes takes away heat and reduces the flame temperature, thereby destroying the conditions for the formation of nitrogen oxides. Usually used together with premixed combustion technology, premixed combustion can effectively reduce the length of the flame, and the shorter flame can be fully cooled by the cooling water pipe, which can effectively reduce the concentration of NOx emissions.
Fully premixed wire mesh surface combustion
Fully premixed combustion refers to the precise proportion premixing of fuel and all required combustion air before combustion. During the whole combustion process, the air-fuel ratio can be kept constant in real time. The porous metal fiber mesh made of iron-chromium-aluminum and rare metal materials is the combustion surface, the pores are evenly distributed, and the combustion intensity is high. After the gas and air are precisely mixed, short cluster flames are generated on the surface, and the combustion area is large. Combustion is uniform, there is no local high temperature zone, and the formation of NOx is effectively suppressed.
The second category is flue gas denitrification technology, that is to say, to process the NOX already produced in the flue gas. The main related technologies are: precious metal catalytic denitrification method, selective catalytic reduction method (SCR), selective non-catalytic reduction method (SNCR) ), lye absorption method, etc.
To achieve ultra-low nitrogen oxide emissions within 30mg/m3, it is difficult to achieve with a single technology, but it is often easier to achieve with two low-nitrogen combustion technologies:
1) Flue gas internal circulation (FIR), NOx emission can be as low as 19mg/Nm³
2) The original imported burner is used, and the quality is reliable
3) Adapt to multi-type boilers, and the success rate of transformation and review is 100%
4) The burner is stable in operation, safe in use and low in maintenance cost
5) Staged combustion technology, low nitrogen without reducing boiler combustion efficiency