Study On Reaction Kinetics Of Catalyst And Mathematical Simulation Of Reactor For Fischer-Tropsch Synthesis

The technology of producing liquid fuel with Fischer-Tropsch Synthesis is an important way to solve China's energy shortage and guarantee the energy safety. The study on reaction kinetics and mathematical simulation of reactors guides the scale-up design and optimal operation of Fischer-Tropsch Synthesis reactors. In this thesis based on the study on eggshell Co-based catalyst's performance the lumping kinetics model consisted of CO consumption rate and carbon chain growth factor a model was established. And the diffusion-reaction model in this catalyst particle was proposed and the effects of reaction pressure,temperature and the particle diameter on the components concentration profile and temperature profile in the particle was studied. Furthermore, the homogeneous one-dimensional model of the tube-shell fixed-bed reactor was established and the mode simulation of synthesis oil pilot test prove the model right, and the effects of the operating conditions and the device parameters on the reactor performance were discussed in detail.With the characterization methods of SEM,BET,XRD,TPR and so on, it was summarized that the surface cobalt species was Co3O4 with good dispersion, and fit calcinations temperature was 450℃. The reduction procedure was temperature programmed with different hydrogen content of the atmosphere and the maximum reduction temperature was 380℃. The experiments was conducted in the isothermal integral reactor and the effects of pressure,temperature,H2/CO and sapce velocity on the reaction results was studied. in the reaction conditions of pressure 3.5MPa, temperature 225℃, H2/CO 2.0 and space velocity l000h-1, the steady experiment was carried on for 400 hours. The results showed that CO and H2 conversation kept 0.72,0.70, the produce output of CH4,lower gydrocarbons,oil and wax kept 8.9μg/s,6.7μg/,25.3μg/s and 42.2μg/s, and C5＋yield kept 171.2g/Nm3. These proved that the catalyst's performance had good stability.The lumping kinetics model was showed as: Through statistical tests and residual analysis, this model was appropriate. With the lumping kinetics model, the effects of different reaction conditions including reaction pressure, temperature, H2/CO and space velocity to the reaction result was analyzed.The diffusion-reaction model in the eggshell Co-based catalyst particle was established. In the condition of pressure 3MPa, temperature 225℃, H2/CO 2.0 and space velocity 1000h"1, the orthogonal collocation method was used to calculate the concentration profile and the temperature profile in the catalyst particle. The simulation results showed that the temperature rised from the outer to inner in the active sites and the maximum temperature difference was 2.15℃and the mole ratio of H2/CO increased. With this diffusion-reaction model, the effects of pressure,temperature and the particle diameter on the reaction result were given. The higher pressure and temperature caused the particle temperature rise and the concentration of CH4,C3Hg,C10H22 small increase. The smaller size catalyst particle engendered the temperature decrese and the maximum temperature difference was 1.46℃. So the small particle would reduce the diffuse resistance and pomote the formation of heavy hydrocarbons.The homogeneous one-dimensional model of the tube-shell fixed-bed reactor was established and the mode simulation of synthesis oil pilot test demonstrated that the outlet flow rate of CH,C3H8,C1oH22,C22H46 was 780.16,251.77,114.14,140.80kg-h-1, C5＋weight pecentage was 80.52% and Cs＋space time yield was 119.36g-(L·h)-1, which was agreement with the pilot test reslusts. The profiles of bed temperature and pressure from the model were consistent to the practical results. The effects of different operating conditions and device parameters to the reactor performance were studied. The increase of inlet temperature,inlet pressure,boiling water temperature and tube diameter would cause the upward migration of catalyst-bed temperature cures, the increase of CO conversion, the decrease of C5＋weight selectivity and increase of C5＋space time yield. The increase of inlet space velocity would cause the downward migration of temperature cures, the increase of C5＋weight selectivity and increase of C5＋space time yield. The increase of H2/CO would cause the downward migration of temperature cures, the decrease of C5＋weight selectivity and C5＋space time yield. The increase of the catalyst-bed height would cause the downward migration of temperature cures, the increase of C5＋weight selectivity and the decrease of C5＋space time yield. The increase of would cause the upward migration of temperature cures, the decrease of C5＋weight selectivity and the increase of C5＋space time yield.