Modeling a Pilot Fixed-Bed Hydrocracking Reactor via a Kinetic Base and Neuro-Fuzzy Method (original) (raw)
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Kinetic Study on a Commercial Amorphous Hydrocracking Catalyst by Weighted Lumping Strategy
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A suitable model for predicting the product quality of vacuum gas oil (VGO) catalytic hydrocracking is developed. Data were obtained using an experimental catalytic hydrocracking reactor loaded with the Ni-Mo/Al2O3-SiO2 catalyst. A set of experimental runs was conducted under various operating temperatures from 380 to 450 ℃. Three distribution models were used to develop the predictive model. By the discrete lumping model, distillation curves of the cracked products (naphtha, kerosene, diesel, and gas) were obtained using the simulated distillation test. Model validation results showed that the proposed models are capable of predicting the distillation curves of the hydrocracked products accurately. Accuracy and simplicity of the developed model make it suitable to estimate the conversion and also the product distribution of hydrocracking units in refineries.
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The main objective of this work is to develop a predictive model for predicting the product quality of vacuum gas oil (VGO) hydrocracking process. Experimental data were obtained using a pilot plant hydrocracking catalytic reactor loaded with the same catalyst type used in a local refinery. Two sets of experimental runs were conducted under various operating conditions. The first one consisted of 18 runs and was used for parameter estimation, while the second set consisted of 29 runs and was used for model validation. Distillation curves of the cracked products were obtained using the simulated distillation (SimDist) test. A distribution model based on probability density function was used to develop the predictive model. The distribution model presents the boiling point as a function of the distilled weight fraction. Model parameters were estimated and related to the specific gravity of the cracked product. Model validation results showed that the proposed model is capable of predicting the distillation curves of the hydrocracked products accurately, especially at high operating severity. Simplicity and accuracy of the developed model makes it suitable for online analysis, to estimate the conversion as well as the product distribution of hydrocracking units in refineries.
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A 6-lump kinetic model, including a catalyst decay function for hydrocracking of vacuum gas oil in a commercial plant, is proposed. The model considers vacuum gas oil (VGO) and unconverted oil, having boiling point higher than 380-• C (380+ • C) as one lump. Other lumps are diesel (260-380-• C), kerosene (150-260-• C), heavy naphtha (90-150-• C), light naphtha (40-90-• C) and gases (40-• C) as products. Initially, a kinetic network with thirty coefficients is considered, but following an evaluation using measured data and order of magnitude analysis, mainly the route passes of converting middle distillates to naphtha lumps are omitted; thus the number of kinetic coefficients is reduced to eighteen. This result is consistent with the reported characteristics of amorphous catalyst, which has the tendency to produce more distillates than naphtha. By using catalyst decay function in the kinetic model and replacing days on stream with a noble term, called accumulated feed, the prediction of the final approach during 1.5 years is in good agreement with the actual commercial data. The average absolute deviation (AAD%) of the model is less than 5% for all main products. If the residue or unconverted VGO is considered, the error only increases to 6.94% which is still acceptable for a commercial model. The results also confirm that the hydrocracking of VGO to upgraded products is represented better by a second order reaction.
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