Comparison of axial dispersion and mixing cell models for design and simulation of fischer-tropsch slurry bubble column reactors

Abstract Two different general approaches for simulating the performance of Fischer-Tropsch slurry bubble column reactors based upon the axial dispersion model and mixing-cell models are described. Comparisons between semi-batch operation and continuous operation with either cocurrent or countercurrent flow of gas and liquid are performed to examine the effect of overall gas-liquid contacting pattern on various measures of reactor performance. For the ranges of operating conditions investigated here, the catalyst distribution is the primary intrinsic variable that is most affected by the use of cocurrent versus countercurrent gas-liquid contacting pattern for the case of continuous operation. If overall synthesis gas conversion is used as a common measure of performance, then cocurrent flow is preferred over countercurrent flow. In terms of describing the liquid-phase flow pattern, a mixing cell model represents a more realistic approach and has computational advantages when compared to the axial dispersion model. A correlation which relates the liquid-phase Peclet number to the number of mixing cells for a particular case is also given and discussed.