Fischer-Tropsch synthesis reactor modeling

Pratt JW. A Fischer-Tropsch Synthesis Reactor Model Framework for Liquid Biofuels Production. Sandia Report SAND2012-7848 September, 2012. Sandia National Laboratories, Albuquerque, NM and Livermore, CA. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

C. Maretto, R. Krishna, Modeling of a bubble column slurry reactor for Fischer-Tropsch synthesis, Catal. Today 52 (1999) 279-289. 

In the design of upflow, three phase bubble column reactors, it is important that the catalyst remains well distributed throughout the bed, or reactor space time yields will suffer. The solid concentration profiles of 2.5, 50 and 100 ym silica and iron oxide particles in water and organic solutions were measured in a 12.7 cm ID bubble column to determine what conditions gave satisfactory solids suspension. These results were compared against the theoretical mean solid settling velocity and the sedimentation diffusion models. Discrepancies between the data and models are discussed. The implications for the design of the reactors for the slurry phase Fischer-Tropsch synthesis are reviewed. 

Another proposal for explaining the two slope distributions is very consistent with the peculiarities of the Fischer Tropsch system The products of Fischer Tropsch synthesis do usually provide a liquid phase and a gaseous phase under reaction conditions.The gaseous compounds leave the reactor normally within a few seconds. The liquid does need a day or more until it elutes from the catalyst bed. Solubility of paraffinic hydrocarbon vapours in a paraffinic hydrocarbon liquid increases by a factor of about 2 for each carbon number of the product (ref. 27). Thus it needs only an increase of a very few carbon numbers of the product molecules to have them leaving the reactor mainly with the gas phase or with the liquid phase. With increasing residence time in the reactor the chance of readsorption increases and correspondingly the probability of chain prolongation increases. The kinetic scheme of this model is shown in Fig. 14. This model is very consistent with the experimental distributions. 

This paper discusses research efforts towards the prediction of hydrocarbon product distribution for the Fischer-Tropsch synthesis (FTS) on a cobalt-based catalyst using a micro-kinetic model taken fiom the literature. In the first part of the study, a MATLAB code has been developed which uses the Genetic Algorithm Toolbox to estimate parameter values for the kinetic model. The second part of the study describes an ongoing experimental campaign to validate the model predictions of the fixed-bed reactor FTS product distribution in both conventional (gas phase) and non-conventional (near-critical and supercritical phase) reaction media. 

Hooshyar N, Vervloet D, Kapteijn F, Hamersma PJ, Mudde RF, van Ommen JR. (2012) Intensifying the Fischer-Tropsch Synthesis by reactor structuring—a model study. Chem. Eng. J., 207-208 865-870. 

Katzschmann E. (1966) Oxidation of alkyl aromatic compounds. Chem. Ing. Tech., 38 1-10. Kenig E, Seferhs P. (2009) Modeling reactive absorption. Chem. Eng. Prog., 105(l) 65-73. Knochen J, Guttel R, Knobloch C, Turek T. (2010) Fischer-Tropsch synthesis in milli-struc-tured fixed-bed reactors experimental study and scale-up considerations. Chem. Eng. Process., 49 958-964. 

The feasibility of increasing the selectivity of the Fischer-Tropsch synthesis by periodic operation is investigated. The process is modeled in a dynamic form using a CSTR reactor. The dynamic behavior of the model corresponds with in literature reported experimental results. The simulation results show a 20% increase in selectivity to Diesel range products compared to the best steady-state solution using a blockprofile. The profile has a cycle time of 1.1 O seconds and consists of a base composition of almost pure carbon monoxide and a pulse of 95% hydrogen and 5% carbon monoxide during 10.8% of the cycle time. 

This study explores the potential of periodic operation for the Fischer-Tropsch synthesis aiming at Diesel range products. The approach followed is modeling the process in a dynamic form using a simple CSTR reactor configuration. The kinetic scheme is based on steady-state data reported in literature. The steady-state behavior is in agreement with experimental observations reported earlier by various research groups. 

Liu QS, Zhang ZX, Zhou JL. Steady-state and dynamic behavior of fixed-bed catalytic reactor for Fischer-Tropsch synthesis I Mathematical model and numerical method. Journal of Natural Gas Chemistry 1999 8 137-150. 

Guillen DP, Grimmett T, Gandrik AM, Antal SP. Development of a computational multiphase flow model for Fischer Tropsch synthesis in a slurry bubble column reactor. Chem. Eng. J. 2011 176-177 83-94. 

Rados N, Al-Dahhan MH, Dudukovic MP. Modeling of the Fischer Tropsch synthesis in slurry bubble column reactors. Catal Today 2003 79-80 211-218. 

Ah6n VR, Costa JEF, Monteagudo JEP, Fontes CE, Biscaia JEC, Lage PLC. A comprehensive mathematical model for the Fischer-Tropsch synthesis in well-mixed slurry reactors. Chem. Eng. Sci. 2005 60 677-694. 

Mills PL. Turner JR. Ramachandran PA, Dudukovic MP. The Fischer-Tropsch synthesis in sltury bubble column reactors analysis of reactor performance usitrg the axial dispersion model. In Nigan FCDP, Schumpe A, editors. Three-phase Sparged Reactors. Topics in Chemical Engineermg 8. Amsterdam Gordon Breach 1996. p 339-386. 

Schweitzer JM, Viguie JC. Reactor modeling of a slurry bubble column for Fischer-Tropsch synthesis. Oil Gas Sci. Technol. Rev. 2009 64 63-77. 

Ghasemi S, Sohrabi M, Rahmani M. A comparison between two kinds of hydrodynamic models in bubble column slurry reactor during Fischer-Tropsch synthesis single-bubble and two-bubble class. Chem. Eng. Res. Des. 2009 87 1582-1588. 

Sehabiague L. Modeling, scaleup and optimization of slurry bubble column reactors for Fischer-Tropsch synthesis [Ph.D. Thesis]. University of Pittsburgh 2012. 

In Section 6.11, Fischer-Tropsch synthesis in a multitube reactor was used as an example to illustrate the differences between the one- and two-dimensional approaches for the simulation of cooled fixed bed reactors. For o-xylene oxidation to phthalic anhydride, only the two-dimensional reactor model is considered. 

Jess, A. and Kern, C. (2009) Modeling of multitubular reactors for Fischer-Tropsch synthesis. Chem. Eng. Techn. 32, 1164-1175... 

Shin, M.-S., Park, N., Park, M.-J., Jun, K.-W., and Ha, K.-S. (2013) Computational fluid dynamics model of a modular multichannel reactor for Fischer-Tropsch synthesis maximum utilization of catalytic bed by microchaimel heat exchangers. Chem. Eng. J., 234,23-32. 

On the basis of the assumptions of model <22> and <23> the Fischer-Tropsch synthesis in a slurry phase BCR has been modeled [37, 38]. As this hydrocarbon synthesis from synthesis gas (CO + H2) is accompanied by considerable volume contraction, it is clear that gas flow variations have to be accounted for. The developed models are useful to evaluate experimental data from bench scale units and to simulate the behavior of larger scale Fischer-Tropsch slurry reactors. Though only simplified kinetic laws were applied, the predictions of the model are in reasonable agreement with data reported from 1.5 m diameter demonstration plant. Fig. 12 shows computed space-time-yields (STY) as a function of the inlet gas velocity. As the Fischer-Tropsch reaction on suspended catalyst takes place in the slow reaction regime, it is understood that STY passes through a maximum in dependence of uqo- The predicted maximum is in striking agreement with experimental observations [37]. 

TI Carbon monoxide hydrogenation over cobalt catalyst in a tube-wall reactor Part II Modeling studies KW Fischer Tropsch synthesis modeling, carbon monoxide hydrogenation cobalt catalyst, tube wall reactor Fischer Tropsch reaction IT Hydrogenation catalysts... 

The model calculation for Fischer-Tropsch synthesis indicates that the exchange between small and large bubbles can be neglected for reaction-hmited systems but becomes important for mass transfer Hmited systems. The gas holdup and syngas conversion predicted by the new reactor model... 

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