Modeling the Thermal Cracking of Ethane and Propane in a Non-Isothermal Vertical Pneumatic Transport Reactor

A model has been formulated for noncatalytic thermal cracking of ethane and propane in a non-isothermal, adiabatic, vertical, pneumatic transport reactor. This model takes into consideration hydrodynamic properties of the gas-solid mixture, gas-particle heat transfer, and a kinetic scheme involving 81 radical reactions among 11 molecules and 11 radicals. Simulations of ethane cracking at a fixed conversion show that the particle diameter and solid to hydrocarbon ratio have the greatest effect on reactor performance; an optimum particle diameter of 50 fim was found. Performance of a simulated heater coil reactor in a conventional pyrolysis furnace was compared with that of the transport reactor. Calculations show that the transport reactor can achieve greater ethylene yield at much shorter residence times for a given conversion. However, propylene, which is one of the main products in propane cracking, is produced at a higher yield in a conventional pyrolysis furnace.