A study on the applicability of non-stoichiometric thermodynamic models for the prediction of carbon black yield and off-gas composition in oil furnace process

The effect of feed composition and temperature on the carbon black yield and off-gas amount and composition was studied for oil-furnace process reactor with benzene as a model feedstock. Because of the high furnace temperature (>1200 °C), the reactions were considered as very fast and thus the products close to chemical equilibrium. The equilibrium composition was calculated by a non-stoichiometric thermodynamic model using Gibbs free energy minimization method. The equilibrium and energy balance equations were solved simultaneously to obtain the product composition and reactor temperature under different reaction conditions. The equilibrium carbon black yield increases with gas/air and oil/air ratio whereas the reactor temperature exhibits the reverse trend which are consistent with practical data. Quantitative comparison with real data showed that the product may be kinetically controlled, and thus the thermodynamic model gives the lower limit of carbon black yield. The model can be easily applied to any feedstock including bio-oil without a need for the specific properties.