| The quality of diesel oil in China is lagging behind that in developed countries. The main reason is the unreasonable arrangement of oil refining unit that the processing capacity of catalytic cracking is overdeveloped but the capacity of hydrogenation is underdeveloped. For shortening the diesel quality gap between China and developed countries as soon as possible, Sinopec Changling Branch Company proposed the new tubular liquid-phase hydrogenation technology which overcome the defect of traditional diesel oil hydrogenation technology base on the principle of chemical reaction engineering. The main innovation of this new technology includes:(1) multi-point hydrogen replenishing instead of massive hydrogen recycling; (2) tubular reactor instead of tank reactor; (3) using ceramic-membrane hydrogen mixer before the reactor for better pre-mixing of gas and liquid. The object of this study is providing theoretical support for the feasibility of new hydrogenation technology from the viewpoint of reaction engineering.The main research content of dissertation includes:1. With the support and cooperation of research institute of Sinopec Changling Branch Company, the experimental installation was built, and the experimental feed stock, catalyst and the preliminary investigating range of reaction conditions were decided. Then the experimental investigation of different technological conditions (reaction temperature, pressure, space velocity, mixing quantity of hydrogen) was carried out, and the influence of different technological conditions on experimental result was analyzed. The results showed that the experiments turned out according to the reaction law. The validity of experimental results not only proved the reliability of experimental installation, but also provided the reference for the reaction condition range of further kinetic experiments.2. The solubility of hydrogen in diesel oil must be investigated because of the distinguishing feature of liquid phase hydrogenation that diesel oil reacts with the hydrogen dissolved in the liquid phase. Based literature search, saturation method was adopted to measure the equilibrium solubility of hydrogen in different diesel oils (catalytic cracking diesel oil, straight-run diesel oil, coking diesel oil), and the influence of different conditions (temperature, pressure, composition of hydrocarbon families) on the solubility of hydrogen was analyzed. Finally the correlation equation between hydrogen solubility and hydrocarbon composition of diesel oil was established with the application of P-N-A method from literature. The validation experiments with different diesel oil, temperature and pressure showed that the relative deviation between the calculation value and experimental value of hydrogen solubility is within 5%. The established equation is reliable which can meet the calculation requirement of diesel oil liquid-phase hydrogenation. So the hydrogen equilibrium solubility in different diesel oil under any hydrogenation temperature and pressure can be predicted with the correlation equation.3. The tubular reactor used in the experiment can be regarded as plug-flow reactor since the ratio of height to diameter of reactor is 17 and the ratio of catalyst bed height to catalyst diameter of RS-2000 is 480:1.6. But the application of hydrogen mixer and tubular reactor is the main innovation of new FCC diesel hydrogenation technology, the flowing status in the tubular reactor with hydrogen mixer need to be further investigated. Because of the limitation of experimental conditions, cold mold experiment was not feasible. The trial and error method was adopted that the experiments with and without hydrogen mixer were carried out under the same feedstock and reaction conditions, and the reaction results were fitted with plug-flow model. The fitting results showed that the reaction result with hydrogen mixer was accord with plug-flow model, the reaction result without hydrogen mixer was not since the deviation of calculation result was quite big.The difference between reaction results could be attributed to the pre-mixing, which means the ceramic membrane mixer is necessary for the well nanometer-grade mixing of hydrogen and diesel oil.4. Based on the massive literature investigation, lumping method was adopted to categorize the reactants into six lumps according the kinetic similarity principle, the analysis condition, the need of product prediction, and the feather of diesel composition. The six lumps are sulfur (S), nitrogen (N), tricyclic aromatic hydrocarbon (PA), bicyclic aromatic hydrocarbon (DA), monocyclic aromatic hydrocarbon (MA) and hydrogen (H). The power-function kinetic model of the new liquid-phase hydrogenation of FCC diesel was established based on the reaction mechanism. The analysis on the obtained model parameters and the preliminary model validation showed that the fitting ability of kinetic model was good enough for the further prediction and simulation.5. The prediction calculation of two different status was carried out with the established liquid-phase hydrogenation model of FCC diesel:(1) Predicting the influence of reaction temperature and liquid hourly space velocity on the hydrodesulfurization, hydrodenitrigenation, aromatic saturation reactions during the process of FCC diesel hydrogenation, which is beneficial for the further influence quantitative analysis of technological condition on hydrogenation condition and future technological optimization. (2) Simulation of the multi-point hydrogen replenishing process which is the innovation of new tubular liquid-phase hydrogenation technology. The calculation results of two schemes with four status showed:The increase of hydrogen replenishing point and amount is beneficial for the undergoing of hydrogenation reaction; if the pre-mixing amount of hydrogen is fixed, the effect of increasing replenishing points is not as well as that of increasing replenishing amount; increasing the replenishing amount in the beginning of reaction in beneficial for the utilization of hydrogen. Further prediction of the hydrogen replenishing position and amount could be carried out with the model in the future, which is the optimization reference of multi-point hydrogen replenishing.6. Computational fluid mechanics (CFD) has been extensively applied to simulating the temperature and concentration distribution of chemical reactors. CFD was used to do the numerical simulation of liquid-phase hydrogenation of FCC diesel oil for providing reliable and visual guidance to the developing and designing of new hydrogenation technology; it is also a new application field of CFD. CFD numerical simulation not only provided clear and reliable image of temperature and reactant concentration distribution along the axial and radial direction of hydrogenation reactor, but also showed the concentration trend of reactants under different reaction conditions. According to the temperature distribution, there was a hot point in the reactor, and the position of hot point was within the 25?30% height of reaction bed with the variation of reaction conditions; in most case, the hydrogen consumption till hot point will exceed 50% which means the hot point is the ideal point of hydrogen replenishing.The research of this paper provides theoretical support and reference not only for the feasibility of new liquid-phase hydrogenation of FCC diesel oil and its three innovation points, but also for other new technology. |
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