Evaluation of retrofitting of an industrial steam cracking furnace by means of CFD simulations

Abstract

Ethylene is one of the most important building blocks of current chemical industry with a global production of 150 million tonnes in 2016. Most ethylene nowadays is produced via thermal cracking with steam of fossil feedstocks in cracking furnaces. This process accounts for approximately 8% of the sector’s primary energy consumption, making it the single most energy-consuming process in the chemical industry. Therefore, an improvement of energy efficiency in cracking furnaces is both environmentally and economically driven. A CFD model of a full scale cracking furnace, including the radiative section equipped with wall burners and the convective sections, has been developed and validated with plant measurements under six different operation scenarios. Modifications of burner configuration and furnace geometry have been considered and simulated with the CFD model to study their effect on overall energy efficiency. Results show that reduction in the number of operative burners leads to higher inhomogeneity in coil temperatures in the radiant section and that a reduction of 25% in crossover length leads to a 2% increase in energy efficiency. An additional post-processing step has been applied to estimate furnace NOx emissions. The resulting outlet concentrations are slightly underestimated although in the correct order of magnitude (100 ppm).