Modelling and simulation of an industrial radial moving bed reactor for propane dehydrogenation process / Haniif Prasetiawan

Faculty of Chemical & Natural Resources Engineering

Thesis (Master of Engineering in Chemical Engineering) -- Universiti Malaysia Pahang – 2015

Bibliography : p. 115-122

In a business environment where the future feedstock is gradually decreasing, a petrochemical plant needs to look into innovative ways of increasing their yields with minimal increase in the feed volume and capital investment. To date, most of the propane dehydrogenation plants have been operating the reactor as a black box and optimisation was performed based on feedback from licensor as well as trial and error. An accurate model is required to optimize the propane dehydrogenation reaction carried out in the radial moving bed reactors (RMBR). In this research, modelling and simulation study of the propane dehydrogenation over platinum on alumina catalyst in RMBR was performed. Power law kinetic model was used to express the propane dehydrogenation reaction and side reactions. RMBR was discretised into axial and radial directions and the equations of the discretised bed were solved numerically. The kinetic parameters were optimised by comparing the simulation results with plant data. The optimised activation energies for the propane dehydrogenation (31.978 kJ/mol), propane cracking (141.94 kJ/mol) and ethylene hydrogenation (149.41 kJ/mol) were in good agreement with the experimental value reported in the literature. The optimised kinetic parameters were then used to perform the base case simulation to generate the component composition, reactor temperature, catalyst activity and coke content profiles in the radial and axial directions of the RMBR. Base case simulation was carried out at the weighted average inlet temperature (WAIT) of 640.68 ºC, inlet pressure for 1st, 2nd, 3rd and 4th reactor of 212, 156, 109 and 56 kPaG respectively, H2/HC molar ratio of 0.699, Us of 600 kg/hr, and hydrocarbon feed flow rate of 267m3/hr. The parametric sensitivity study was done by varying WAIT by ±5 ºC, H2/HC molar ratio by ±0.2, catalyst circulation rate (Us) by ±80 kg/hr and feed flow rate by ±3 m3/hr from the base case condition. It was found that the H2/HC molar ratio has most significant effect on the propane conversion and propylene yield. Maximum yield was obtained by increasing the inlet temperature of each reactor by 5 ºC and Us by 80 kg/hr from the base case and reducing H2/HC molar ratio by 0.2 and feed flow rate by 3 m3/hr from the base case. The propane conversion, propylene yield and coke content increase by 11.5, 11.3 and 12.2 % respectively from the base case while the propylene selectivity decreases by 0.15 %. A user friendly graphical user interface (GUI) was developed based on the validated model to ease the use of RMBR simulation by the plant personnel.