| Hydrogenation technology refers to a process technology that makes the raw oil react with hydrogen through the catalytic action of a catalyst under a certain temperature and pressure to improve the quality of the oil or obtain the target product.The fixed bed hydrogenation reactor is one of its most commonly used equipment.The better structure of the hydrogenation reactor can make the gas-liquid two-phase flow distribution in the catalyst bed evenly,thereby improving the efficiency of the reactor.In this thesis,the CFD numerical simulation method is used to study the internal flow field characteristics of the hydrogenation reactor,including:First,a CFD analysis model of a cold-flow model reactor with a diameter of 2 m was established.Comparing the numerical simulation results with the cold model visualization test results,the two flow regimes and pressure drop are in good agreement,which verifies the accuracy of the VOF model and the Realizable k-? turbulence model.Secondly,the CFD analysis model of an industrial 5.8 m hydrogenation reactor under the condition of oil and hydrogen materials was established.The model includes the reactor model of the initial design and the reactor model after the internal structure improvement,each with a scale of 650 million nodes.The holographic transient simulation inside the reactor was realized by the 512-core supercomputing platform,and the distribution characteristics of the flow field inside the reactor were obtained.The comparative analysis of the flow field distribution of the two reactor models shows that the impact of the inlet on the first layer of liquid surface is weakened after the structure improvement,the increase of the sieve plate structure in the hydrogenation chamber improves the uniformity of flow distribution,and the improved cyclone structure has a good mixing and crushing effect.And the space on the height of the reactor is saved.Finally,the CFD simulation technology is used to simulate the influence mechanism of the structuzsral parameters of distribution pipe and the cyclone in the hydrogenation reactor on the flow characteristics: According to the structural parameters such as porosity,throat diameter,distribution pipe height,pipe inner diameter,overflow hole diameter and other structural parameters,17 groups of single distribution pipe CFD analysis models were established.The effects of these structural parameters on the twophase mixing characteristics and flow distribution characteristics of the cyclone are obtained.Through the comparative analysis of CFD results,it is found that the size of the distribution pipe injection angle is the result of the combined effect of the distribution pipe opening rate and the ratio of the distribution pipe inner diameter to the throat diameter.And a new method for the design of distribution pipe based on the ratio of throat opening ratio and inner diameter throat diameter is proposed.In terms of cyclone simulation research: 8 groups of single cyclone CFD analysis models were established for structural parameters such as the cyclone inlet height,outlet height,entryway shape,outlet baffle shape and internal inverted cone,and the counter-rotation of these structural parameters was obtained.The effects of these structural parameters on the two-phase mixing characteristics and flow distribution characteristics of the cyclone are obtained.Through the comparative analysis of CFD results,it is found that the tapered inlet can increase the swirl velocity and strengthen the two-phase mixing;the inverted cone structure increases the flow instability and increases the pressure drop by an order of magnitude;the reduction in the height of the inlet and outlet is conducive to the two-phase mixing and can improve space utilization,etc.These conclusions provide an important reference for the improved design of the cyclone structure size. |
PDF Full Text Request