Abstract:

Accurate measurement of temperature distribution of pipe surface becomes the key issue for optimization of heating process in tubular furnace. Experiment research of visualization of pipe temperature distribution was conducted on an industrial ethylene cracking furnace based on radiation image processing. Inside the furnace pipe, thermal cracking reaction of naphtha occurs, whose reaction heat is provided by eight burners located on the bottom, and the fuel is natural gas. Coking of furnace pipe was ignored in the model. In order to deal with the radiative heat transfer equation with complex boundary condition in the tubular furnace, a DRESOR method based on Monte Carlo principle was used, and the radiations from tubes, flame and furnace wall were decoupled. Sixteen CCD cameras were mounted on the furnace wall in order to capture the flame image which was transferred into boundary radiation intensity distribution by blackbody calibration. A revised Tikhonov regularization method was used to solve the morbid radiation image equation, and the distributions of pipe temperature and heat flux were measured online and their variation trends with flow direction of naphtha were also discussed. Validated by two different methods, temperature reconstruction error was less than 2% and maximum deviation was within 20K, and the major error occurred on the maximum and minimum temperature areas. This study would be useful for adjustment of combustion and heating process in tubular furnace, and would improve the uniformity of pipe surface temperature in order to extend their working life.

Key words: tubular furnace, radiation, pipe, modeling, heat flux

摘要：

准确在线检测管壁表面分布式温度是优化管式炉加热工艺的关键所在。以一台工业管式裂解炉为试验对象,结合辐射图像处理方法,开展了管式炉炉管表面温度可视化检测研究。采用基于Monte Carlo的DRESOR法求解具有复杂边界条件的管式炉辐射成像模型,实现了炉管辐射与火焰辐射、炉壁辐射的解耦计算,对炉管表面温度与热通量分布进行了在线监测,并研究了二者随工质流动方向的变化趋势。经过验证,温度测量误差小于2%,测量误差主要出现在最高和最低温区域。该项研究将有助于指导管式炉燃烧调整,改进加热工艺,提高炉管表面受热均匀性,延长炉管工作寿命。

关键词: 管式炉, 辐射, 炉管, 建模, 热通量