OP-II-3

OP-I-16DEVELOPMENT OF A CFD BASED PROCESS SIMULATIONCAPABILITY FOR A FISCHER-TROPSCH REACTORAntal S.P. 1 , Jordi R. 2 , Combes G. 31 Interphase Dynamics, Ballston Lake, USA, antals@rpi.edu2 Sasol Technology, Sasolburg, South Africa3 Johnson Matthey PLC, Middlesbrough, UKThis paper presents a computational multiphase fluid dynamics (CMFD) model ofa Gas-To-Liquid (GTL) reactor utilizing the Fischer-Tropsch conversion process. Thegoal of the CMFD model is to accurately predict both the hydrodynamic flow profilesand the local reaction kinetic rate. A typical pilot sized (1m diameter) Fischer-Tropsch(FT) process reactor demonstrates the capability of the model to better understandthe hydraulic and reaction engineering. Previous work, References [1] and [2], haveshown the hydraulic model capable to accurately simulate two-phase flow profiles ina bubble column and churn-turbulent flows. To validate the reaction chemistry in theCMFD computer code, a one dimensional model is compared to well accepted handcalculations to verify the implementation and test its accuracy.The GTL reactor is assumed to operate in either the bubbly, churn-turbulent, ormixed bubbly-churn flow regime. In each of these operating conditions the gas-liquidinterface forces, which control the gas holdup and liquid flow profiles, can be verydifferent. To accurately capture the flow physics a five field model of two-phase flowwas implemented with the NPHASE-CMFD [3] computer code. The five fields choseninclude the liquid “l”, very small bubbles “vsb” (diameter < 1 mm), small bubbles “sb”(diameter 1 to 10 mm), large cap/slug bubbles “lb” (diameter > 10mm), and thecatalyst particles “p”. The use of separate fields allow different closure model physicsto describe the interfacial forces on each field. The ensemble averaged [4]conservation equations, used as the framework for this technology, can be written as:Mass Conservation (field j)∂∂t( αjρj) + ∇ ⋅ ( αjρjuj) = mjMomentum Conservation (field j)∂∂t′′′Re( α ρ u j) + ∇ ⋅ ( α ρ u juj) = −α∇p+ ∇ ⋅α( τ + τ ) + α ρ g + M j + m′′′uijjjjjjjjjjjj66