Shape Optimal Design For Vanadium Catalyst

It is well known that the shape and size of catalyst can affect the fluid flow and reaction process in fixed bed reactor. This dissertation studied the effects of shape and size of vanadium catalysts on the flow of feed gas with CFD method. Optimal range of catalyst sizes were obtained which could be used to guide industrial catalyst design. Our study include:(1)CFD simulation method for vanadium catalysts. Single-particle models with different angles and multi-particle models of annular and quincunx particles were established. The study of mesh size proved that our models were mesh independent in the scope of our research, and reasonable mesh parameters were set. Arithmetic and models in Fluent were compared and optimized:RNG κ-ε for turbulence model, second order upwind for discretization format. Under-relaxation factors were adjusted to meet the requirements of our study. Calculation results of CFD and empirical formulas were compared to verify the effectiveness and accuracy of our proposed method.(2) Optimal design of annular catalyst particles. Pressure fields, velocity fields and pressure drops of gas flow were obtained using both single-particle models and multi-particle models. The results showed that pressure and velocity of fluid flowing in the inner-hole of annular particles gradually decrease with the increase of angle between particle axis and flow direction, which would cause the reduction of internal surface utilization ratio and hinder the reaction. Pressure drop data of annular single-particle models and multi-particle models with different inner diameter showed that pressure drop drops with the increase of inner diameter. To be specific, pressure drop decreased slowly when the inner diameter was changed from 0 to 2 mm. And it decreased more rapidly in a quasi linear mode when the inner diameter was increased from 3 to 6 mm. When the inner diameters were further changed from 7 to 8 mm, the pressure drop decreased slowly again. Optimal inner diameters of annular vanadium catalyst particles could be selected in the range of 3 to 6 mm in consideration of particle strengths and height of catalyst bed.(3) Optimal design of quincunx particles. The influences of inner diameter, petal number and petal diameter were studied. Pressure drop decreased slowly when the inner diameter was changed from 0 to 2 mm. And it decreased more rapidly in a quasi linear mode when the inner diameter was increased from 3 to 5 mm. When the inner diameters were further changed from 7 to 8 mm, the pressure drop decreased slowly again. Optimal inner diameters of quincunx vanadium catalyst particles could be selected in the range of 3 to 5 mm in consideration of particle strengths and height of catalyst bed. Less petal number and smaller petal diameter were found to be able to decrease the resistance and pressure drop. Optimal petal number was 4, and optimal petal diameter was 2 mm.(4) Calculation results of cylinder, annular and quincunx multi-particle models were compared. Pressure drop of annular multi-particle model accounted for 46.8% of cylinder model, and pressure drop of quincunx multi-particles model accounted for 45.4% of annular model and 21.2% of cylinder model. Under the same flow status, pressure drop of annular particles was more sensitive to the change of inner diameter than quincunx particles, and pressure drop of quincunx particles was always lower than that of annular particles with the same inner diameters.