High velocity burners are mainly used in industrial furnaces. Ordinary industrial furnaces have a spacious furnace for heating materials and ensuring complete combustion of fuel. In this way, it takes a long time to heat the furnace to the operating temperature when the furnace is turned on; when the furnace is stopped, due to the large thermal inertia, there is still a considerable period of time to continue heating the workpiece, making it difficult to control the heating temperature and easily causing the workpiece to overheat. In order to prevent the workpiece from overheating, ordinary heating furnaces have to operate at a temperature slightly higher than the allowable maximum heating temperature of the workpiece, which reduces the heating speed and increases the heating time, especially when the workpiece is close to the final heating temperature. In addition, prolonging the heating time at high temperature will have various adverse effects, such as causing oxidation and decarburization of steel, making the surface of the workpiece rough and reducing the hardness. In order to save energy, eliminate the shortcomings of ordinary heating furnaces, and match modern production lines, rapid heating technology appeared in the 1960s. Rapid heating relies primarily on convective heat transfer rather than radiative heat transfer. It is characterized by small furnace body, fast heating speed, small thermal inertia, high quality of heated workpiece, high thermal efficiency and easy automatic control.
The key to achieve rapid heating is to transform the furnace body; the second is to apply high-speed burners. The high-speed burner has two functions. One is that the gas burns at a very high heat intensity; the other is that the high-temperature flue gas is ejected from the combustion chamber (fire path) at a very high flow rate (200-300m/s), thereby increasing the temperature in the furnace. The effect of convective heat transfer. Compared with ordinary burners, high-speed burners have the following main characteristics.
advantage:
① The volumetric heat intensity of the combustion chamber is very high, up to 21×104kW/m3, the furnace volume is small, the furnace body structure is simple, the operation is convenient, the safety device and the piping system in front of the furnace are simple; the combustion temperature of the combustion chamber is relatively high, close to 2000°C, It is very beneficial to the development of high-temperature kiln and fuel saving;
② The flue gas expands violently in the flue and the exit of the flue is equipped with a flue gas nozzle, so the flue gas ejection speed is very high, up to 200-300m/s;
③ The atmosphere in the furnace can be easily adjusted to be oxidative or reductive, and can work at a higher excess air coefficient;
④ The load adjustment range is large, the adjustment ratio can reach 1:50, and the ordinary burner can reach 1:20～1:30;
⑤ High temperature preheating air can be used, so high combustion temperature can be obtained with low calorific value gas;
⑥ Since the combustion reaction is completed instantaneously in the fire channel, the fire will not be extinguished in the furnace with an inert atmosphere.
shortcoming:
① Higher gas and air pressure are required, and more power consumption is required;
② The combustion chamber (fire channel) requires special high-temperature-resistant and erosion-resistant materials, otherwise the service life is very short;
③ The working noise is relatively loud, and corresponding noise reduction measures need to be taken.
The benefits received by the application of high-speed burners in industry are as follows.
① The structure of the furnace body is simplified, and the spacious combustion chamber of the ordinary heating furnace is no longer required except for the flue type combustion chamber. The management is convenient, and the arrangement of the safety device and the pipeline in front of the furnace is simple.
② The high-temperature flue gas ejected at high speed can inject a large amount of flue gas at a lower temperature in the furnace, forming a strong flue gas backflow and stirring effect, so that the temperature distribution in the furnace is even. According to different ejection speeds, the amount of backflow flue gas ejected is also different, usually within the range of 20 to 200 times.
③ Due to the large load adjustment range and convective heat transfer, the temperature in the furnace can be high or low, and the thermal inertia is small, so the range of use of the furnace is expanded.
④ Suppresses the formation of NOx. Since the concentration of oxygen in the combustion process can be controlled to the minimum required, the flue gas stays in the high-temperature area for a short time, and after the high-temperature and high-speed flue gas is injected into the lower-temperature flue gas in the furnace, it is rapidly diluted to reduce the temperature. The strong heat exchange in the furnace also makes the flue gas cool down rapidly, thus inhibiting the formation of NOx. So the high-speed burner is also a low NOx burner.
⑤ Save fuel. Due to factors such as high combustion efficiency, forced circulation of gas in the furnace and good stirring effect, no combustion chamber other than the fire channel, and easy adjustment of gas in the furnace, it saves fuel.
⑥ The number of burners can be reduced. Since the high-speed airflow can make the furnace temperature uniform, it is not necessary to use a large number of burners to ensure uniform furnace temperature as before. The small number of burners is also conducive to self-control.
The high-speed burner shown in the figure above is equivalent to a blast burner with a combustion chamber with a flue gas nozzle added at its outlet. The gas and air are strongly mixed and burned in the combustion chamber, and the high-temperature flue gas of complete combustion is sprayed into the furnace at a very high flow rate, and has a strong convective heat exchange with the workpiece. The heat load of this burner can reach 2330kW. High-speed burners are mainly used in heat treatment furnaces, glass ceramic products furnaces and metal melting furnaces.
High velocity burners are mainly used in industrial furnaces. Ordinary industrial furnaces have a spacious furnace for heating materials and ensuring complete combustion of fuel. In this way, it takes a long time to heat the furnace to the operating temperature when the furnace is turned on; when the furnace is stopped, due to the large thermal inertia, there is still a considerable period of time to continue heating the workpiece, making it difficult to control the heating temperature and easily causing the workpiece to overheat. In order to prevent the workpiece from overheating, ordinary heating furnaces have to operate at a temperature slightly higher than the allowable maximum heating temperature of the workpiece, which reduces the heating speed and increases the heating time, especially when the workpiece is close to the final heating temperature. In addition, prolonging the heating time at high temperature will have various adverse effects, such as causing oxidation and decarburization of steel, making the surface of the workpiece rough and reducing the hardness. In order to save energy, eliminate the shortcomings of ordinary heating furnaces, and match modern production lines, rapid heating technology appeared in the 1960s. Rapid heating relies primarily on convective heat transfer rather than radiative heat transfer. It is characterized by small furnace body, fast heating speed, small thermal inertia, high quality of heated workpiece, high thermal efficiency and easy automatic control.
The key to achieve rapid heating is to transform the furnace body; the second is to apply high-speed burners. The high-speed burner has two functions. One is that the gas burns at a very high heat intensity; the other is that the high-temperature flue gas is ejected from the combustion chamber (fire path) at a very high flow rate (200-300m/s), thereby increasing the temperature in the furnace. The effect of convective heat transfer. Compared with ordinary burners, high-speed burners have the following main characteristics.
advantage:
① The volumetric heat intensity of the combustion chamber is very high, up to 21×104kW/m3, the furnace volume is small, the furnace body structure is simple, the operation is convenient, the safety device and the piping system in front of the furnace are simple; the combustion temperature of the combustion chamber is relatively high, close to 2000°C, It is very beneficial to the development of high-temperature kiln and fuel saving;
② The flue gas expands violently in the flue and the exit of the flue is equipped with a flue gas nozzle, so the flue gas ejection speed is very high, up to 200-300m/s;
③ The atmosphere in the furnace can be easily adjusted to be oxidative or reductive, and can work at a higher excess air coefficient;
④ The load adjustment range is large, the adjustment ratio can reach 1:50, and the ordinary burner can reach 1:20～1:30;
⑤ High temperature preheating air can be used, so high combustion temperature can be obtained with low calorific value gas;
⑥ Since the combustion reaction is completed instantaneously in the fire channel, the fire will not be extinguished in the furnace with an inert atmosphere.
shortcoming:
① Higher gas and air pressure are required, and more power consumption is required;
② The combustion chamber (fire channel) requires special high-temperature-resistant and erosion-resistant materials, otherwise the service life is very short;
③ The working noise is relatively loud, and corresponding noise reduction measures need to be taken.
The benefits received by the application of high-speed burners in industry are as follows.
① The structure of the furnace body is simplified, and the spacious combustion chamber of the ordinary heating furnace is no longer required except for the flue type combustion chamber. The management is convenient, and the arrangement of the safety device and the pipeline in front of the furnace is simple.
② The high-temperature flue gas ejected at high speed can inject a large amount of flue gas at a lower temperature in the furnace, forming a strong flue gas backflow and stirring effect, so that the temperature distribution in the furnace is even. According to different ejection speeds, the amount of backflow flue gas ejected is also different, usually within the range of 20 to 200 times.
③ Due to the large load adjustment range and convective heat transfer, the temperature in the furnace can be high or low, and the thermal inertia is small, so the range of use of the furnace is expanded.
④ Suppresses the formation of NOx. Since the concentration of oxygen in the combustion process can be controlled to the minimum required, the flue gas stays in the high-temperature area for a short time, and after the high-temperature and high-speed flue gas is injected into the lower-temperature flue gas in the furnace, it is rapidly diluted to reduce the temperature. The strong heat exchange in the furnace also makes the flue gas cool down rapidly, thus inhibiting the formation of NOx. So the high-speed burner is also a low NOx burner.
⑤ Save fuel. Due to factors such as high combustion efficiency, forced circulation of gas in the furnace and good stirring effect, no combustion chamber other than the fire channel, and easy adjustment of gas in the furnace, it saves fuel.
⑥ The number of burners can be reduced. Since the high-speed airflow can make the furnace temperature uniform, it is not necessary to use a large number of burners to ensure uniform furnace temperature as before. The small number of burners is also conducive to self-control.
The high-speed burner shown in the figure above is equivalent to a blast burner with a combustion chamber with a flue gas nozzle added at its outlet. The gas and air are strongly mixed and burned in the combustion chamber, and the high-temperature flue gas of complete combustion is sprayed into the furnace at a very high flow rate, and has a strong convective heat exchange with the workpiece. The heat load of this burner can reach 2330kW. High-speed burners are mainly used in heat treatment furnaces, glass ceramic products furnaces and metal melting furnaces.