| Ethylene is one of the most important materials in the chemical industry.And a country’s ethylene yield is viewed as the symbol of its capability in thechemical industry. The leading role in the petroleum industry ethylene playsmakes it the hot spot for many researchers.The cracking of petroleum hydrocarbons including naphtha is the mainsource of ethylene. In the process of the steam cracking of naphtha, coking isalways a big problem. The coke on the tube wall can influence theheat-transferring ability of the tube. It can also result in the sharp decline ofthe pressure in the tube, which threatens the stability of the cracking process.The main content of this article is as follows:A kinetic model of the naphtha cracking process---the Kumar model---isused to get the product distribution of the cracking process. There are twokinds of parameters that are very important in this model: the initialselectivities and the kinetic parameters. The initial selectivities are calculatedfrom the low conversion experiment on the bench reactor. And the kineticparameters are derived from the data obtained from the normal conversionexperiments.A revised method for the molecular reconstruction of naphtha based ontwo commonly methods is proposed and the components of the sample naphtha are predicted by the method. The predicted values match theanalytical values very well.In this paper, considering the material, energy and momentum balances,mathematical models for three industrial furnaces----USC-80U, GK-V andMSF are established. A coking model established by Reyniers and Froment isthen used in the mathematical simulation. In the calculaton of the heat balance,two simplified methods are used. The product distribution and the cokedistribution are very close to the industrial data, which confirms thecorrectness of the furnace model. The predicted run lengths of the threefurnace models agree with the actual run lengths of the three furnaces, thusproving the correctness and applicability of this coking model... |
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