Study of Carbon Formed on Stainless Steel 304H in a Simulated Environment of the Convection Section of the Ethane Cracking Furnace System

Thursday, May 15, 2014: 16:20
Orange, Ground Level (Hilton Orlando Bonnet Creek)
F. Ramezanipour, A. Singh, S. Paulson (University of Calgary), H. Farag (NOVA Research & Technology Center (NRTC), Calgary), V. Birss, and V. Thangadurai (University of Calgary)
The stainless steel 304H (SS304H) is one of the important alloys used in petrochemical industry, such as in the convection section of the ethylene production furnaces. The exposure to carburizing gases makes this alloy susceptible to carbon formation and potential carburization. The present study focuses on understanding the coking behavior of SS304H in ethane/steam environment and the effect of H2S at 700oC. Long-term (90 hours) experiments in such environment show that the addition of ppm amounts of H2S has a pronounced effect on the morphology of the carbon formed on the SS304H surface, as shown by scanning electron microscopy. In the absence of H2S, the deposited carbon forms distinct fibers, which are distributed homogeneously on the surface. The addition of 15 ppm H2S results in the formation of carbon clusters, consisting of very thin fibers that are tightly entangled. Also, experiments in the presence of H2S showed a systematic decrease in the amount of carbon as H2S increased from 1 to 2, 5, 7, and 10 ppm. At 10 ppm H2S, no carbon was observed on the SS304H surface after 4 h of exposure to ethane/steam at 700oC. Mass spectrometry studies showed that the addition of H2S does not affect the temperature or products of ethane cracking. The effect of the SS304H coupons on the ethane cracking products was also studied by mass spectrometry, and showed that the ethane cracking process is not significantly affected by the presence of the metal coupon.