Turbulent mixing enhancement of thermal cracking coil by Hollow Cross Disk internal

The Hollow Cross Disk (HCD) internal is designed to enhance the meso- and micro-mixing performance of thermal cracking process to suppress coking as well as optimize product distribution. Combined research methods of cracking experiment and computational fluid dynamics (CFD) are used to investigate the strengthening effect of the novel internal. The naphtha cracking experiment result shows that HCD internal can improve the overall olefin yield by 0.95% and reduce the production of coke by 4.67% comparing with bare coil. Contrast CFD simulations of propane pyrolysis in industrial scale cracking coil are conducted to reveal the specific enhancing character of the designed internal. Comparing with bare coil (Case A), coil with HCD internal (Case B) can improve the Nu and Sh by 4.59% and 0.82% respectively, reducing the skin temperature of the cracking coil by 21.76k. As HCD internal can induce radial velocity component to enhance radial mixing in the coil wall vicinity, intensifying turbulence to accelerate fluid in the near wall region to reduce the average residence time, which is beneficial to relieve coking. In addition, the intensified turbulence leads the overall characteristic micro-mixing time of Case B reduced to 1.96% of the bare coil. The enhanced micro-mixing can improve the overall olefin yield by 2.97% as the molecular scale uniform reactive region is expanded by 0.58% for Case B.