Model parameters are tuned using dynamic industrial data. H2 (mol%); and volume fraction of oxygen exiting stack x NIST subscription sites provide data under the Calorimetric determination of the heats of combustion of ethylene and propylene, Cracking reactions to form ethylene occur in the coils where the temperature of the reacting process gas is typically 700°C‐900°C. ; Alcock, C.B. Selected Values of Properties of Chemical Compounds., Thermodynamics Research Center, Texas A&M University, College Station, Texas, 1997. Two of the model inputs and the measured output variables are shown in Figures 3-5. Figure 7 confirms that pyrolytic coke formation appears to play the major role in the coking process of steam cracking furnaces since the majority of the coke forms beyond the 1 mm threshold for the catalytic coke formation. Figure 3 shows that the inlet pressure was increased abruptly by the plant operators at ~ 300 h and was then increased gradually over time to compensate for the increased pressure drop caused by coke formation. In the current article, a model is developed to predict coke formation in ethane cracking furnaces. Figure 4 shows the mass flow rate of the fuel to the furnace (in scaled units) during operation, which is another key model input. More recently, Wauters and Marin39, 40 developed a detailed model for pyrolytic coke formation based on elementary reactions between process gas components and the macro radical coke surface. α s = 2.15 scaled unit). [all data], Burcik E.J., 1941 s = 0.87). An automation code was developed in Visual Basic with macros in Excel to determine the coke‐formation‐rate profile along the coils and to determine the run length of the furnace. D Ab initio statistical thermodynamical models for the computation of third-law entropies, Ref. The cold box of the radiant section starts at x 0000004813 00000 n
Use the link below to share a full-text version of this article with your friends and colleagues. NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data) c, Thermodynamic Properties of Individual Substances, 4th ed. x�b```�=�@(��������A�ߙ�̈́�'\�X���:00�)r�h�B�� �Ĭ�,�y���Ʃ�e�Eq`.���j��-U �.�d�h8)�yF#�Nh�!#����Q�1���Hl���Z��Ŷ��:Z& vGG�b6q��� ��T#�4��D�Q�$� �rH����Q4�D���R��Wp �6�#��bM��� �t�8�'� �[�d^0. NIST Standard Reference Note that the data for C3 and C5+ have very large measurement uncertainties compared to the size of measurements (see Figure 6I and J), therefore, they were not used for parameter estimation. Pyro. 0000009444 00000 n
0000057525 00000 n
A similar detailed model has never been published for naphtha cracking due to the much larger number of species and reaction steps that would be required. The discrepancies between the simulation results and measurements are acceptable, since the model predictions tend to be close to the data (usually within the error bar indicating the measurement uncertainty). Chem. The dynamics of coke formation are much slower than the dynamics of the cracking reactions in the coils. At time zero, there is no coke and the thickness increases with time as the run proceeds and coke deposits on the inner surface of the pyrolysis coils, especially in the hottest part of the radiant section. Cox, J.D. The coil position starts at zero at the entrance of the convection section. Go To: Top, Gas phase thermochemistry data, Notes, Chase, 1998 In this equation, r and you may need to create a new Wiley Online Library account. . high selectivity in favor of formation of the desired product and high catalytic activity [11]. 0000006157 00000 n
Thanks for you help. Energy balance equations in the pyrolysis model were developed to account for radiative, conductive, and convective heat transfer in the radiant section and for convection and conduction in the USX. f,Cat, and A number of models that do not account for coke formation have been developed to predict ethane conversion, ethylene yield, and temperatures in industrial furnaces2, 43-45 Information from these models for gas‐phase reactions in the coils is important for predicting coke formation rates, which depend on the local ethylene concentrations and process gas temperatures. Ni in the catalytic coke formation model (Equation (8)) is the nickel surface area in m2/g of the Ni metal particles and is related to the chemistry of the coil surface.
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