Study On The Reaction Kinetics Of Fischer-Tropsch Synthesis Over A Precipitated Iron-based Catalyst And Mathematical Simulation Of A Large-scale Slurry Bubble Column Reactor

Fischer-Tropsch synthesis(FTS),a reaction process with syngas from coal,natural gas or biomass as raw materials to synthesize a wide range of products including hydrocarbons and high-valued alcohols under certain conditions,is the key step for the coal liquifacction.The reaction kinetics of Fischer-Tropsch synthesis,hydrodynamics in slurry bubble column reactor(SBCR),and the mathmaticle simulation of SBCR means a lot to the designing,scaling-up and optimization of a large-scale industrial Fischer-Tropsch synthesis slurry bubble column reactor.Based on the research of the reaction performance of low-temperature precipitated iron-based catalyst,the intrinsic CO consumption rate model and product distribution model on the basis of ASF model in a tubuler fixed-bed reactor,were established,a one-dimentional pseudo mathematical model for a lare scale industrial Fischer-Tropsch synthesis slurry bubble column reactor was established based on the two-class bubble assumption.The reactor performance under the industrial operating conditions was simulated compared with the industrial data,and the effect of operating conditions on the reactor performance was discussed.The surface and textual structure of the low-temperature iron-based catalyst was characterized by SEM,XRD,N2 adsorption-desorption and H2-TPR.The results of characterization indicated that the particle size of calcinated catalyst is around 200?m and the mean pore diameter is 9.93 nm which means that it is a meso-pore catalyst.The iron catalyst could be reduced in pure H2 atmosphere with three-step conversion which includes the reduction process at 293.7? corresponding to the reduction of Fe2O3 to Fe3O4,at 623.4?from Fe3O4 to FeO,and at 715.9? from FeO to Fe.The evaluation of reaction performance of the catalyst was carried out in a tubuler fixed-bed reactor,a higher temperature,pressure,H2/CO and lower Sv was of benefit to increasing the syngas consumption rate,while a lower pressure and higher temperature,H2/CO and Sv was benefit to the reduction of selectivity of products with high carbon number.Meanwhile the results also indicated that the product distribution deviated from ASF model,and the molar ratio of olefins to parrafins(O/P)decreased with carbon number exponentially.The increase of reaction temperature and Sv,the decrease of pressure and H2/CO would increase O/P.The experiments for testing the intrinsic CO consumption rate over the precipitated iron-based catalyst in a tubuler fixed-bed reactor were carried out under 230??260?,2?4 MPa,H2/CO 0.70-2.08 and Sv 2000h-1?3000 h-1,the model expression of intrinsic CO consumption rate was achieved.The experiments for testing the global CO consumption rate was carried out in a stirred tank reactor under 210?250?,0.5-4.0 MPa,H2/CO 1.0-2.5 and 63.6?125.2 ml/min and the global consumption rate of CO was achieved.The product distribution model was established based on the experimental data and ASF model.The formation rate of products like methane,low-carbon hydrocarbons,oil and wax was achieved by combining the CO intrinsic consumption rate and the expression of carbon chain growth probability factor.Statistical analysis proved the validity of both of the intrinsic and global CO consumption rate,and the product distribution model were also suitable for predicting the reaction performance of the precipitated iron-based catalyst.The one-dimentional pesudo mathematical model of a large-scale industrial Fischer-Tropsch slurry bubble column reactor was established based on the intrinsic CO sonsumption rate,product distribution,hydrodynamics in SBCR and two-class bubble assumption.The mathematical simulation of the industrial slurry bubble column reactor was conducted under 513.15 K,2.8 MPa,UG,0=0.30 m/s,H2/CO=1.71,CS=22%and DR=9.8 m.The comparison of simulation results including CO conversion,the selectivity and annual yields of CH4,C24=,C2-4,C5-10,C11-20,C21+ with industrial data indicates that the relative error is smaller than ±10%which means that the developed one-dimentional pseudo mathematical model is suitable for the prediction and optimization of the large-scale industrial Fischer-Tropsch slurry bubble column reactor.The effects of reaction temperature,pressure,H2/CO,superficial gas velocity and solid concentration on the reactor performance was simulated and analysed.The results show that CO conversion increases with the enhancement of temperature,pressure and H2/CO in feed gas,a lower reaction temperature and superficial gas velocity,a higher pressure and ratio of H2 and CO in feed gas is preferencial for the enhancement of the selectivity of disel and wax components while the selectivity of CH4?C2-4=,C2-4 and gasoline decrease with it.As for the annual yields,it increases with the rise of temperature,pressure,H2/CO and the reduction of the superficial gas velocity.The increase of solid concentration could increase the CO conversion,selectivities of C21+?C10-20?C5-10 and the annual yields of products.