连退炉用U型辐射管内无焰燃烧的数值模拟  

Numerical simulation on flameless combustion in U-shaped radiant tube for continuous annealing furnace

作　　者：徐家强 宋中华 潘妮[1] 谭方关 许学成[1] 贺铸[1] XU Jia-qiang;SONG Zhong-hua;PAN Ni;TAN Fang-guan;XU Xue-cheng;HE Zhu(Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education,Wuhan University of Science and Technology,Wuhan 430000,Hubei,China;Wuhan Iron and Steel Group Research Institute,Wuhan 430000,Hubei,China)

机构地区：[1]武汉科技大学钢铁冶金及资源利用省部共建教育部重点实验室,湖北武汉430000 [2]武汉钢铁有限公司技术中心集团公司研究院,湖北武汉430000

出　　处：《钢铁》2022年第1期143-150,共8页Iron and Steel

基　　金：国家自然科学基金资助项目(51974211)。

摘　　要：钢铁冶金用连续退火炉中通常使用辐射管对工件进行间接加热,这不仅保证被加热工件受热均匀,还能不影响其表面质量。但同时,由于辐射管内燃烧空间有限,极易产生局部高温区,这会影响被加热产品质量,而且高温会导致NO_(x)大量生成,此外,较大的壁温差异所产生的热应力会使管壁遭到蠕变破坏,缩短其使用寿命。因此,为了优化辐射管的性能,基于烟气再循环技术提出了一种新型辐射管燃烧器,它能在提高烟气循环量的同时保证燃烧持续进行,具体为,先在辐射管内进行传统燃烧,待温度高于燃料自燃点后,再引入大量烟气,从而使U型辐射管内达到无焰燃烧状态,此时,其表面温度更为均匀,NO_(x)排放也更低。通过建立带该燃烧器的U型辐射管数学模型,并辅以试验验证,探究了U型辐射管内无焰燃烧特性,包括辐射管内燃烧状态、表面温度均匀性以及NO_(x)排放情况,且将其与现有的U型辐射管进行了对比分析,并探讨了不同烟气卷吸量对辐射管内无焰燃烧特性的影响。研究结果表明,无焰燃烧状态完全不同于传统燃烧,传统燃烧情况下,辐射管前部存在明显的局部高温区;随着卷吸烟气量的引入及进一步增大,峰值温度不断下降,且高温区有向辐射管后部转移的现象,达到无焰燃烧状态时,局部高温区消失;无焰燃烧极大提升了辐射管表面温度均匀性,辐射管壁温温差极值由110减至35 K,温度均匀系数由9%减小到2.9%,这有利于提升辐射管实际使用寿命;污染物NO_(x)的排放由初始的0.022%降至0.000 1%以下。In order to ensure that the heated workpiece is evenly heated without affecting its surface quality, the metallurgical industry generally uses radiant tubes to indirectly heat the workpiece. But at the same time, due to the limited combustion space in the radiant tube, it is easy to produce a local high temperature zone, which will affect the quality of the heated product, and the high temperature will cause a large amount of NO_(x)to be generated. In addition, the thermal stress generated by the large wall temperature difference will cause the tube wall damaged by creep, shortening its service life. Therefore, in order to optimize the performance of the radiant tube, a new type of radiant tube burner is proposed based on the flue gas recirculation technology, which can increase the flue gas circulation while ensuring continuous combustion. Specifically, the traditional combustion is first carried out in the radiant tube. After the temperature is higher than the auto-ignition point of the fuel, a large amount of flue gas is introduced, so that the U-shaped radiant tube reaches a flameless combustion state. At this time, the surface temperature is more uniform and the NO_(x)emission is lower. Through the establishment of a mathematical model of the U-shaped radiant tube with the burner, supplemented by experimental verification, the flameless combustion characteristics in the U-shaped radiant tube were explored, including the combustion state in the radiant tube, the uniformity of surface temperature and the NO_(x)emission, and the existing U-shaped radiant tube was compared and analyzed, and the influence of different smoke volume on the flameless combustion characteristics in the radiant tube was discussed. The research results show that the flameless combustion state is completely different from traditional combustion, under traditional combustion, there is an obvious local high temperature zone in the front of the radiant tube;with the introduction and further increase of the volume of cigarette smoking, the p

关 键 词：连续退火炉 辐射管 烟气再循环 无焰燃烧 NO_(x) 

分 类 号：TG155.1[金属学及工艺—热处理]