Industrial Steam Reformers and Methanators

Steam reformers are used industrially to produce syngas, i.e., synthetic gas formed of CO, CO2, 11-2, and/or hydrogen. In this section we present models for both top-fired and side-fired industrial steam reformers by using three different diffusion-reaction models for the catalyst pellet. The dusty gas model gives the simplest effective method to describe the intermediate region of diffusion and reaction in the reformer, where all modes of transport are significant. This model can predict the behavior of the catalyst pellet in difficult circumstances. Two simplified models (A) and (B) can also be used, as well as a kinetic model for both steam reforming and methanation. The results obtained for these models are compared with industrial results near the thermodynamic equilibrium as well as far from it. 

Methanators are usually used in the ammonia production line to guard the catalyst of the ammonia converters from the ill effect of carbon monoxide and carbon dioxide. This section includes precise models for different types of methanators using the dusty gas model with reliable kinetic expression and the results are compared with those of the simplified models (A) and (B). 

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Chapter 7 is the climax of the book Here the educated student is asked to apply all that he/she has learned thus far to deal with many common practical industrial units. In Chapter 7 we start with a simple illustrative example in Section 7.1 and introduce five important industrial processes, namely fluid catalytic cracking in FCC units in Section 7.2, the UNIPOL process in Section 7.3, industrial steam reformers and methanators in Section 7.4, the production of styrene in Section 7.5, and the production of bioethanol in Section 7.6. 

A rigorous dusty gas model and two simplified models have been used to simulate industrial steam reformers and methanators. The basic principles for the solution of both the nonadiabatic steam reformer and the adiabatic methanator are given. The details of developing solution algorithms from the models are left to the reader as a serious and extensive project. 

F.M. Alhabdan, M.A. Abashar, S. Elnashaie, A flexible software package for industrial steam reformers and methanators based on rigorous heterogeneous models, Mathematical and Computer Modeling, 16, 77-86, 1992... 

Industrial Steam Reformers and Methanators Using the Dusty Gas Model, Latin American Applied Research (in Press, 1993). 

Optimization of the performance of ammonia converters Concluding remarks Computer simulation package for industrial ammonia converters Precise Modelling of Industrial Steam Reformers and Methanators... 

Elnashaie SSEH, Abashar MEE (1993) Steam reforming and methanation effectiveness factors using the dusty gas model under industrial conditions. Chem Eng Proc 32 177-189... 

Elnashaie, S.S.E.H. and Abashar, M.E., Steam Reforming and Methanation Effectiveness Factors Using the Dusty Gas Model Under Industrial Conditions. Chem. Eng. and Processing (in Press, 1993). 

There are a number of major industrial problems in the operation of the steam reforming of methane. These include the formation of carbon on the surface of the catalyst, the sulphidation of the catalyst by the H2S impurity in commercial natural gas, and the decline of catalytic activity due to Ostwald ripening of the supported catalyst particles by migration of catalyst atoms from the smaller to the larger particles, as the temperature is increased. A consideration of the thermodynamics of the principal reaction alone would suggest that the reaction shifts more favourably to the completion of the reaction as the temperature is increased. 

Electropox [Electrochemical partial oxidation] Also called Pox. An electrochemical process for oxidizing methane to syngas. It combines the partial oxidation and steam reforming of methane with oxygen separation in a single stage. Invented in 1988 by T. J. Mazanec at BP Chemicals. An industrial-academic consortium to develop the process was formed in 1997. 

Of the indirect liquefaction procedures, methanol synthesis is the most straightforward and well developed [Eq. (6)]. Most methanol plants use natural gas (methane) as the feedstock and obtain the synthesis gas by the steam reforming of methane in a reaction that is the reverse of the methanation reaction in Eq. (5). However, the synthesis gas can also be obtained by coal gasification, and this has been and is practiced. In one modern low-pressure procedure developed by Imperial Chemical Industries (ICI), the synthesis gas is compressed to a pressure of from 5 to 10 MPa and, after heating, fed to the top of a fixed bed reactor containing a copper/zinc catalyst. The reactor temperature is maintained at 250 to 270°C by injecting... 

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