Numerical simulation of catalytic upgrading of biomass pyrolysis vapours in a FCC riser

Panneerselvam Ranganathan,Sai Gu

doi:10.1016/j.fuproc.2017.11.008

Abstract

Catalytic upgrading of biomass pyrolysis vapours is a potential method for the production of hydrocarbon fuel intermediates. This work attempts to study the catalytic upgrading of pyrolysis vapours in a pilot scale FCC riser in terms of hydrodynamics, residence time distribution (RTD) and chemical reactions by CFD simulation. NREL's Davison Circulating Riser (DCR) reactor was used for this investigation. CFD simulation was performed using 2-D Eulerian–Eulerian method which is computationally less demanding than the alternative Euler-Lagrangian method. First, the hydrodynamic model of the riser reactor was validated with the experimental results. A single study of time-averaged solid volume fraction and pressure drop data was used for the validation. The validated hydrodynamic model was extended to simulate hydrodynamic behaviours and catalyst RTD in the Davison Circulating Riser (DCR) reactor. Furthermore, the effects on catalyst RTD were investigated for optimising catalyst performance by varying gas and catalyst flow rates. Finally, the catalytic upgrading of pyrolysis vapours in the DCR riser was attempted for the first time by coupling CFD model with kinetics. A kinetic model for pyrolysis vapours upgrading using a lumping kinetic approach was implemented to quantify the yields of products. Five lumping components, including aromatic hydrocarbons, coke, non–condensable gas, aqueous fraction, and non–volatile heavy compounds (residue) were considered. It was found that the yield of lumping components obtained from the present kinetic model is very low. Thus, the further research needs to be carried out in the area of the kinetic model development to improve the yield prediction.

Highlights

Fast pyrolysis, the rapid heating of biomass in the oxygen–free atmosphere, has been considered as a promising technology for the production of transportation fuels, speciality and fine chemicals, and furnace and boiler fuel [1]
National Renewable Energy Laboratory (NREL)'s Davison Circulating Riser (DCR) reactor was used for this investigation
For catalytic cracking of pyrolysis vapours, multiphase flow CFD model with five lumping pseudo–components based kinetic model was attempted for the first time

Summary

Introduction

The rapid heating of biomass in the oxygen–free atmosphere, has been considered as a promising technology for the production of transportation fuels, speciality and fine chemicals, and furnace and boiler fuel [1]. Catalytic fast pyrolysis (CFP) has a potential option for improving the quality of organic products from fast pyrolysis of biomass [3] This process can be operated by either in–situ where the catalyst and biomass are mixed in the same reactor or ex–situ where the vapours from the biomass pyrolysis reactor react with the catalyst in a separate reactor system [4,5]. Ex–situ catalytic fast pyrolysis process or pyrolysis vapours upgrading can be considered a potential method for the production of hydrocarbon fuel intermediates such as carboxylic acids, aldehydes, ketones, furans and phenolic compounds [6]. In comparison with fixed bed reactor, fluidised bed operations could be preferred because it produces relatively lesser coke and reduces catalyst deactivation [14] It has the advantages of continuous and quick catalyst regeneration [6]. The pyrolysis vapours upgrading in fluidised bed follows a similar procedure in the

Methods

Results

Conclusion