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The development of a relatively simple mechanistic model for an industrial ethylene cracking furnace is described, including the estimation of selected model parameters to improve model predictions. Energy balance equations are developed to account for radiative, conductive, and convective heat transfer in the radiant section, and for convection and conduction in the ultra-selective heat exchanger (USX) and in the transfer line exchanger (TLE). Kinetic schemes by Ranjan et al. and Sundaram and Froment are used to model the cracking reactions. [1,2] The heat transfer model is combined with mass and momentum balances to model gas composition, pressure, and temperature changes as a function of position along the reactor tubes. Initial values and uncertainty ranges are assigned to 44 model parameters based on information in the literature and our industrial sponsor. A sensitivity-based technique and a mean-squared-error (MSE) criterion are used to select the appropriate subset of 22 parameters for tuning. Parameters are estimated and model predictions are validated using industrial data. Model predictions provide a good match to data that were not used for estimation.

The influence of presulfidation and H2S cofeeding on the carbon formation on SS304 alloy in the ethane–steam cracker was investigated in a laboratory-scale quartz reactor setup. SS304H coupons and SS304L powder samples were exposed to ethane–steam and dry ethane in varying H2S content (0–50 ppm), and the SS304 samples were characterized by scanning electron microscopy. This study shows that H2S cofeeding decreases catalytic carbon formation; while it increases the pyrolytic carbon formation during ethane–steam cracking. Preoxidation, presulfidation, and addition of steam to ethane feed also reduces the amount of catalytic carbon formed on the SS304H surface in short-term experiments (4 h). Presulfidation and addition of H2S to ethane feed significantly influences the shape and size of the carbon formed on the surfaces of investigated metal alloys. Presulfidation and H2S cofeeding reduced spalling of the SS304H coupon surface during coking/decoking and thermal cycling.