【作者】 刘宇；

【导师】 薛庆国；

【作者基本信息】 北京科技大学 ， 冶金工程， 2021， 博士

【摘要】 钢铁工业煤气主要包括转炉煤气、高炉煤气和焦炉煤气,是重要的二次能源,一般主要作为钢铁厂热风炉、轧钢加热炉和电厂锅炉等工业炉的燃料燃烧。煤气的组分对其在燃烧器中的燃烧速率和尾气中污染气体的浓度有很大的影响。为研究钢铁工业煤气的燃烧行为,基于可调谐二极管激光吸收光谱(TDLAS)技术在实验室研制建立了一套煤气燃烧检测系统,利用该系统研究了不同组分煤气在工业燃烧器中的燃烧特性。首先,对TDLAS技术的激光参数进行了选择和设定。选出波长为1996.89 nm和2004.02 nm的CO2吸收曲线对气体温度和浓度进行在线实时测量。在实际测量环境中,对两条吸收线进行了校准并得到了最佳测量参数,其中波长为1996.89 nm的激光器最终设置为:温度28.14℃,电流37 mA,波长为2004.02 nm的激光器最终设置为:温度26.62℃,电流37 mA。在实验室研制了一套燃烧检测系统并对整套系统进行了调试。设计和搭建了供气气路、燃烧器、自动点火和紧急切断装置以保证不同组分煤气的安全稳定燃烧。在实际测量燃烧参数时搭建了惰性气体吹扫装置和积分球装置以提高激光信噪比。此外,利用TDLAS技术对火焰温度和组分浓度进行了测量,并与传统测量方法相对比从而验证了此光谱测量技术的可靠性。以转炉煤气(CO-CO2-H2-N2)的燃烧为背景,利用燃烧检测系统实验研究了在燃料流中的H2和N2含量对CO-CO2火焰特性和尾气中氮氧化物浓度的影响,讨论和对比了燃料流中加入体积百分比为0-24%的H2和N2对火焰结构、火焰温度分布、火焰中的CO和CO2浓度分布以及尾气中NOx浓度的影响。结果表明,在燃料流中加入H2和N2都会导致火焰长度的增加,但H2对火焰长度的影响比等量N2的影响更大。加入H2会导致火焰温度和火焰中的化学反应速率增加,加入N2会导致火焰温度和火焰中的化学反应速率降低。加入H2之后火焰中的最高CO浓度增加,加入N2之后火焰中的最高CO浓度降低。H2和N2百分比的增加都会导致火焰中的CO2浓度降低。在燃料流中加入加入H2不利于NOx减排,而加入N2有利于NOx减排。以高炉煤气(CO-H2-CO2-N2)的燃烧为背景,利用燃烧检测系统实验研究了在CO与H2不同配比的条件下,火焰的结构、火焰温度分布、火焰中CO和CO2浓度分布以及尾气中NOx浓度的变化。研究了燃料流中加入体积百分比为0-32%的CO2和N2对火焰结构、火焰温度分布、火焰中CO和CO2浓度分布以及尾气中氮氧化物浓度的影响。结果表明,在CO与H2的混合煤气中,H2所占的百分比越大,火焰长度越短,火焰温度越高,燃烧速率越高;CO所占的百分比越大,越有利于NOx减排。在CO-H2燃料流中加入CO2和N2都会导致火焰长度增加,相同加入量条件下,CO2比N2对火焰长度的影响更大。在CO-H2燃料流中加入CO2和N2都会降低火焰温度和火焰中的化学反应速率,但CO2的影响大于等量N2的影响。在CO-H2燃料流中加入CO2会导致火焰中的CO浓度增加,而增加N2会导致火焰中的CO2浓度降低。加入CO2对火焰中CO浓度的影响小于加入等量N2的影响。加入CO2对火焰中CO2浓度的影响大于加入等量N2的影响。在CO-H2燃料流中加入CO2、N2和CO2-N2(50%-50%)都有利于减少NOx排放,但加入CO2更有利于NOx减排。以焦炉煤气和焦炉煤气与高炉煤气的混合煤气(H2-CH4-CO和H2-CH4-CO-CO2-N2)的燃烧为背景,实验研究了用CO部分取代燃料流中加入体积百分比为0-20%的H2或CH4以及在燃料流中加入体积百分比为0-32%的CO2、N2和CO2-N2(50%-50%)对混合煤气的火焰结构、火焰温度分布、火焰中的CH4、CO和CO2浓度分布以及尾气中的NOx浓度的影响。结果表明,CO部分取代CH4之后,火焰长度减小,火焰温度降低,火焰中的最高CO浓度随着CO百分比的增加而增加。CO部分取代H2之后,火焰长度增加,火焰温度降低,火焰中CH4的消耗速率随着CO百分比的增加而增加。CO部分取代CH4或H2都有利于NOx减排,相对而言CO部分取代CH4更有利于NOx减排。在H2-CH4-CO燃料流中加入CO2和N2都会增加火焰的长度,相同加入量条件下,CO2比N2对火焰长度的影响更大。加入CO2和N2都降低了 H2-CH4-CO火焰的温度和火焰中的化学反应速率和强度,相同加入量条件下,CO2的影响比N2的影响更大。火焰中的CO浓度会随着CO2百分比的增加先增后降,会随着CO2-N2百分比的增加先降后增。加入N2对火焰中CO氧化反应速率的影响高于加入等量的CO2。火焰中的CH4浓度会随着CO2-N2百分比的增加先降后增。CO2浓度最高位置会随着CO2和N2百分比的增加向燃烧器喷口处靠近,加入CO2比加入等量的N2更接近燃烧器喷口处。在燃料流中加入CO2和N2都降低了尾气中的NOx浓度,但加入CO2比加入等量的N2更有利于NOx减排。更多还原

【Abstract】 Iron and steel industrial gas mainly includes converter gas,blast furnace gas and coke oven gas,which is an important secondary energy and is usually used as fuel for industrial furnaces such as reheating furnaces for steel rolling,hot blast stoves and boilers in power plants.Converter gas is a kind of medium calorific value gas,which can be used as industrial fuel to burn alone or mixed with coke oven gas.The components of iron and steel industrial gas have great influence on the combustion rate in actual industrial burners and the concentration of pollutant gas in the exhaust.In this study,for the purpose of investigating the combustion behaviour,a combustion detection system based on tunable diode laser absorption spectroscopy(TDLAS)technology is developed to simulate the combustion of metallurgical gas in industrial burners and investigate its combustion characteristics.First of all,the laser parameters of TDLAS technology were set,and CO2 absorption curves with wavelengths of 1996.89 nm and 2004.02 nm were selected for the online measurement of flame temperature and species’ concentration.In the complex measurement environment,the two absorption lines were calibrated and the best measurement parameters were obtained.The wavelength of 1996.89 nm was finally set as temperature 28.14℃ and current 37mA,while the wavelength of 2004.02 nm was set as temperature 26.62℃ and current 37 mA.Then,a combustion diagnosis system was designed and develpoed.According to the combustion of iron and steel industry gas in industrial burners,the burner and gas supply circuit were designed,built and adjusted to ensure stable combustion.Automatic ignition and emergency cut-off devices were designed and built to ensure the safety of the experiment.When measuring combustion parameters,an inert gas purging device and an integrating sphere device are built to improve the signal-to-noise ratio of laser.The TDLAS measurement was compared to traditional measurement methods to verify the reliability of TDLAS measurement.Based on the combustion of converter gas(CO-CO2-H2-N2),the effects of H2 and N2 on the CO-CO2 flame characteristics and the concentration of NOx in the exhaust were experimentally studied by using the combustion detection system.The effects of 0-24%by volume of H2 and N2 in fuel flow on the flame structure,flame temperature,CO and CO2 concentration distribution in flames and the concentration of NOx in the exhaust were discussed and compared.It is found that the increase of H2 and N2 percentage will lead to the increase of flame length,but the increase of flame length and flame length after increasing H2 is greater than that after increasing equal percentage N2.The addition of H2 leads to an increase of flame temperature and chemical reaction rate in the flame,while the addition of N2 leads to a decrease of flame temperature and chemical reaction rate.The highest CO concentration in the flame increases with H2 addition.The highest CO concentration in flame decreases with N2 addition.The increase of H2 and N2 lead to the decrease of CO2 concentration in flame.The position of the highest CO2 concentration in the flame is far away from the burner nozzle with H2 addition,which remains unchange with N2 addition.The increase of H2 percentage in gas is not conducive to NOx emission reduction,while the increase of N2 percentage is beneficial to NOx emission reduction.Based on the combustion of blast furnace gas(CO-H2-CO2-N2),the flame structure,flame temperature distribution,CO and CO2 concentration distribution in flames and the NOx concentration in the exhaust were experimentally studied by using combustion detection system.The effects of 0-32%pure CO2,pure N2 and CO2-N2(50%-50%)in fuel flow on flame structure,flame temperature distribution,concentration distribution of CO and C02 in flame and concentration of nitrogen oxides in tail gas were studied.The results show that the addition of H2 in the mixed gas leads to a short the flame length,high flame temperature and high combustion rate.The addition of CO leads to a higher NOx emission reduction.Increasing CO2 and N2 in CO-H2 fuel flow will lead to the increase of flame length,but CO2 has a greater influence on flame length than N2 under the condition of equal percentage.The addition of CO2 and N2 will reduce the flame temperature and the chemical reaction rate in the flame.The influence of CO2 on the flame temperature and chemical reaction in the flame is greater than that of N2 under the condition of equal percentage.Increasing CO2 in the CO-H2 fuel stream will lead to the increase of CO concentration in the flame,while increasing N2 will lead to the decrease of CO2 concentration in the flame.Under the condition of equal percentage,the influence of CO2 on CO concentration in flame is less than that of N2,but the influence on CO2 generation in flame is greater than that of N2.Adding CO2,N2 and CO2-N2(50%-50%)to the CO-H2 fuel stream is beneficial to reduce NOX emission,but relatively speaking,increasing CO2 is more beneficial to reduce NOx emission.Based on the combustion of coke oven gas and the mixture of coke oven gas and blast furnace gas(H2-CH4-CO and H2-CH4-CO-CO2-N2),the effects of CO replacing H2 or CH4 with 0-20%by volume and CO2,N2 and CO2-N2 with 0-32%by volume(50%-50%)on the combustion characteristics were experimentally studied.It was found that when CO replaced CH4,the flame length decreased.The temperature of the flame is lower.With the increase of CO,the highest CO concentration in the flame increases.After replacing H2 with CO,the flame length and the consumption rate of CH4 in the flame increase,but the flame temperature decreases.Replacing CH4 or H2 with CO is beneficial to NOx emission reduction,but replacing CH4 with CO is more significant.Increasing CO2 and N2 in H2-CH4-CO fuel flow will increase the flame length,but under the condition of equal percentage,CO2 has a greater influence on the flame length than N2.The increase of CO2 percentage and N2 percentage reduces the temperature of H2-CH4-CO flame and the rate and intensity of chemical reaction in flame,but CO2 has a greater influence on flame temperature and chemical reaction in flame than N2.The CO concentration first increases and then decreases with the addition of CO2,and first decreases and then increases with the addition of CO2-N2.Under the condition of equal percentage,the influence of N2 on the reaction rate of CO oxidation in flame is higher than that of CO2.The CH4 concentration first decreases and then increasse with the addition of CO2-N2.Increasing CO2 and N2 will lead to the location of the highest CO2 concentration approaching to the burner nozzle,but under the condition of equal percentage,the location of the highest CO2 concentration is closer to the burner nozzle when increasing CO2 than when increasing N2.Increasing CO2 and N2 in fuel flow can reduce the concentration of NOx in exhaust gas,but increasing CO2 is more beneficial to NOx reduction than increasing N2.更多还原