engleski

Kinetic 4-lump model application in gas oils catalytic cracking studying

The FCC process has been one of the most important refinery unit operations for over sixty years. It converts high molecule weight petroleum fractions, such as heavy gas oils and atmospheric and vacuum residues, into more valuable products, as are gasoline, liquefied petroleum gas and light olefins. Growing environmental concerns require lowering of sulfur, aromatics and olefins content in fuels. FCC gasoline accounts for the vast majority of sulfur-containing products. Hydroprocessing of FCC feed is one of the best ways to reduce sulfur in all FCC products. In addition, it increases conversion into gasoline and lighter products, raises yields of FCC gasoline, reduces yields of light cycle and decanted oil, and of coke yields. Catalytic cracking of hydrocarbons is a very complex process because of many reactions and a rapidly changing activity of a cracking catalyst during the reaction. Gas oil used in the FCC process as feedstock and cracking products are complex mixtures of many compounds. A complex interaction between feed, process parameters and heat factor complicate the analysis of catalytic cracking kinetics. Chemical kinetics modeling of the main reactions is used to improve and predict the FCC process. Catalytic cracking of gas oils (hydrotreated and nonhydrotreated) has been studied in a standard MAT reactor. The cracking product distribution was measured as a function of temperature. Based on these experimental results, a 4-lump kinetic model was developed. Kinetic constants were estimated using sequential step optimization method. A non-isothermal pseudo steady-state model for fixed bed MAT reactor was proposed. Reactor model takes into account the temperature drop because of the heat of endothermic reactions and volume expansion owing to cracking reactions. The heats of reactions were taken from macroscopic difference of enthalpies of products and reactants. The influence of feedstocks used and reactor temperature were discussed. Reactor and kinetic model were validated with results from MAT test data. Simulation results are in a good agreement with experimental data.

kinetic model; gas oil; catalytic cracking

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