The radiant tube burner was modeled and analyzed by the numerical simulation method to investigate the influence factors and rules of NO_(x) emissions in a W-type radiant tube.These factors,which include air preheatin...The radiant tube burner was modeled and analyzed by the numerical simulation method to investigate the influence factors and rules of NO_(x) emissions in a W-type radiant tube.These factors,which include air preheating temperature,excess air coefficient,and fuel gas composition,were modified to study their effects on NO_(x) emissions under varying working conditions.Simulation results were compared with the theoretical calculation value based on chemical reaction equilibrium theory and the onsite experimental value to verify the simulation accuracy.The results show that NO_(x) emissions rise with increasing air preheating temperatures.NO_(x) production increases to an extreme value and then decreases during the oxygen-poor to oxygen-enriched process with the rise of the excess air coefficient.Enhancing the proportion of coke oven gas in the fuel gas raises the combustion temperature as well as the NO_(x) discharge.Both the thermal efficiency and NO_(x) emissions should be balanced.Therefore,the recommended values based on the simulation results are as follows:the air preheating temperature should not exceed 400℃,the excess air coefficient should be between 1.1 and 1.2,and the volume fraction of the coke oven gas should not exceed 30%.展开更多
An experimental study was carried out in a small-scale furnace to investigate the performance, such as NOx emission, enhancement of heat transfer, uniformity of temperature, and etc., of oscillating combustion applied...An experimental study was carried out in a small-scale furnace to investigate the performance, such as NOx emission, enhancement of heat transfer, uniformity of temperature, and etc., of oscillating combustion applied in radiant tube burner sy stem for heat treatment furnace. A premixed type burner and a solenoid type oscillating control valve were designed and used. The fuel was used commercial LPG in this study and the fuel flow was oscillated by periodically opening and shutoff of the solenoid valve. From the tests, it was found that NOx emission, compared to no oscillation, could be reduced by 32% at 2.0 Hz. However, as oscillating frequency was increased, abatement of NOx emission was gradually reduced. At the high NOx abatement of 1.0 Hz, carbon monoxide was emitted above 10,000 ppm. Although rate of NOx abatement was low, oscillation condition of 2.5 Hz and duty ratio of 10-30% was recommended for low carbon monoxide emission. From the measurement of furnace heating time from 100 ℃ to 720 ℃, it was shown that heat transfer was increased by 11.5% at 2 Hz oscillating frequency. Temperature distribution of radiant tube surface was more uniform at 2 Hz oscillating frequency with drop of the peak temperature and rise of low temperature. From these results, it was confirmed that oscillating combustion was useful in radiant tube burner system.展开更多
文摘The radiant tube burner was modeled and analyzed by the numerical simulation method to investigate the influence factors and rules of NO_(x) emissions in a W-type radiant tube.These factors,which include air preheating temperature,excess air coefficient,and fuel gas composition,were modified to study their effects on NO_(x) emissions under varying working conditions.Simulation results were compared with the theoretical calculation value based on chemical reaction equilibrium theory and the onsite experimental value to verify the simulation accuracy.The results show that NO_(x) emissions rise with increasing air preheating temperatures.NO_(x) production increases to an extreme value and then decreases during the oxygen-poor to oxygen-enriched process with the rise of the excess air coefficient.Enhancing the proportion of coke oven gas in the fuel gas raises the combustion temperature as well as the NO_(x) discharge.Both the thermal efficiency and NO_(x) emissions should be balanced.Therefore,the recommended values based on the simulation results are as follows:the air preheating temperature should not exceed 400℃,the excess air coefficient should be between 1.1 and 1.2,and the volume fraction of the coke oven gas should not exceed 30%.
文摘An experimental study was carried out in a small-scale furnace to investigate the performance, such as NOx emission, enhancement of heat transfer, uniformity of temperature, and etc., of oscillating combustion applied in radiant tube burner sy stem for heat treatment furnace. A premixed type burner and a solenoid type oscillating control valve were designed and used. The fuel was used commercial LPG in this study and the fuel flow was oscillated by periodically opening and shutoff of the solenoid valve. From the tests, it was found that NOx emission, compared to no oscillation, could be reduced by 32% at 2.0 Hz. However, as oscillating frequency was increased, abatement of NOx emission was gradually reduced. At the high NOx abatement of 1.0 Hz, carbon monoxide was emitted above 10,000 ppm. Although rate of NOx abatement was low, oscillation condition of 2.5 Hz and duty ratio of 10-30% was recommended for low carbon monoxide emission. From the measurement of furnace heating time from 100 ℃ to 720 ℃, it was shown that heat transfer was increased by 11.5% at 2 Hz oscillating frequency. Temperature distribution of radiant tube surface was more uniform at 2 Hz oscillating frequency with drop of the peak temperature and rise of low temperature. From these results, it was confirmed that oscillating combustion was useful in radiant tube burner system.
