Modelling, simulation, exergy and economic analyses of thermal cracking of propane using CO₂ and steam as diluents

Introduction of diluents can increase the yield of valuable products and reduce the coking rate during thermal cracking of propane. Use of captured CO₂ as diluent for the ethylene manufacturing is preferred to avoid high cost of CO₂ transport and storage. A 1-dimentional pseudo-dynamic model of plug flow reactor (PFR) was developed and implemented in gPROMS ModelBuilder®. The model was validated with industrial data. Economic and exergy analyses of the PFR using steam or CO₂ as diluent were then carried out. The results indicate that using CO₂ as diluent can increase the run length of PFR by 13.0% and annual profit by 10.20%. When operating at the ratio achieving highest annual profit, using CO₂ as diluent can reduce exergy destruction by 20.53%. The key findings from this study indicate that using CO₂ as alternative diluent has high potential to increase the profit and reduce energy consumption for ethylene manufacturing. Further study will focus on the effects of diluent-to-propane ratio using different diluents and the potential of using mixed diluents.