Modeling Complex Multiphase Reaction System:Residuum Hydrocracking And Extractive Hydration

Ebullated-bed and fixed-bed reactor are adopted for residual oil hydrogenation process in the industry. Based on the complex multiphase reaction system of residuum hydrocracking, due to the model of residuum hydrocracking in expanded-bed reactor has not been repoted, a multiphase expanded-bed model was set up to simulate transport and reaction performances of the residuum hydrocracking process for the purpose of rendering fundamental evidences for the selection of reacting temperatures and application of heterotype catalysts in the industry. The effects of reaction temperature and catalyst particle of different shapes packed in the expanded reactor on the flow and mass transfer characteristics of the reactor bed and mass yield of middle fraction oil (180～350℃)were investigated on the basis of simulation results. The results suggest that:(1)Pe number increased with the rise of the reaction temperature. This elucidates that,the higher the reaction temperature reaches, the more close to plug flow the liquid flow in the reactor bed is.(2) Due to the changes of backmixing effect and reaction rate constant, concentration distribution of middle distillate along the reactor axial position increases with the rise of temperature.(3) The export quality yield of middle distillates under different reaction temperatures were as follows:35.62%,50.17%,61.23%and75.02%.(4) With different shapes of catalyst filled in the bed, the order of bed voidage is:4-lobe>3-lobe> cylinder> denher<dentiform<sphere. This shows that, backmixing of the reactor bed is the most serious when4-lobe catalysts were filled in the bed, but it is the most minor when sphere catalysts were filled in the bed.(5)The order of Pe number is:4-lobe<3-lobe<cylinder<denher<dentiform<sphere.(6) Because of good diffusion properties of the shaped catalyst, the effectiveness of lumps is different, the order of it is:4-lobe>3-lobe> cylinder> dentiform> sphere.(7)The order of concentration distribution of middle distillate along the reactor axial position is:4-lobe>3-lobe> cylinder> dentiform> sphere.(8) The export quality yield of middle distillates under different situations were as follows:61.23%,67.52%,70.17%,76.795and81.42%.Tert-butyl alcohol is one of petrochemical products with extensive applications, it can be made by the process of isobutene catalytic hydration. The advanced technology of tert-butyl alcohol production in industry is the counterflow catalytic hydration of isobutene in C4raffinate. Modeling liquid-liquid counter-current fixed-bed reactor has not been reported in the literature. Hence, based on this reaction-separation coupled complex reaction systems, a multiphase fixed-bed reactor model was set up to simulate mass-transport, heat-transport and reaction performances. On the basis of reactor model, the calculation of technological design and reaction performance analysis for countercurrent catalytic hydration fixed bed reactor with an annual output of50000tons of tert-butyl alcohol was carried out. The analysis of reaction performance were disscussed, which contains thermal effect of the reactor bed and effect of such process conditions as reaction temperature, the ratio of water to oil, C4hydrocarbon flow rate and mode of operation on conversion of isobutene. Conclusions were as follows:(1) For an annual output of50000tons of tert-butyl alcohol task, the design calculation results are as follows:the reactor with diameter of5.3m, the height of14m were used, oil-water two-phase inlet volume flow rate were34.92and122.57m3/h respectively, the reaction temperature is92℃, and the reaction is2.1MPa.(2) In the range of reaction temperature (60～95℃) for the simulation, the conversion of isobutene is in direct ratio to the reaction temperature.(3) The conversion of isobutene is in inverse proportion to the ratio of water to oil. But if the ratio of water to oil is too large, the processing ability of the C4raffinate will decrease, which caused additional energy consumption of the tert-butyl alcohol concentration. So, the best water to oil ratio is4-5.(4) The conversion of isobutene decreased with the increase of C4hydrocarbon flow rate.(5) With respect to the operation of cocurrent. upflow, the operation of counterflow is propitious to the conversion of isobutene.(6) When the water inlet temperature was92℃and the wall temperature was85℃, difference in temperature for the reactor is6.64℃, and heat exchange between the reactor wall and the reaction system is1.04kJ/s.