Component list reforming

The last sets of correlations we will address are composition correlations. These correlations identify chemical composition in terms of total paraffin, naphthene and aromatic (PNA) content of a particular feed based on key bulk measurements. These correlations are useful in two respects. First, we use these correlations to screen feeds to different refinery reaction units. For example, we may wish to send a more paraffinic feed to a reforming process when we want to increase the yield of aromatic components from the refinery. Secondly, these types of correlations form the basis of more detailed lumping for kinetic models that we will discuss at great length in subsequent chapters of this book. We will use these types of correlations to build extensive component lists that we can use to model refinery reaction processes. 

Figure 5.42 Initial component list for reforming process.

Originally, extractive distillation was limited to two-component problems. However, recent developments in solvent technology enabled applications of this hybrid separation in multicomponent systems as well. An example of such application is the BTX process of the GTC Technology Corp., shown in Figure 6, in which extractive distillation replaced the conventional liquid-liquid extraction to separate aromatics from catalytic reformate or pyrolysis gasoline. This led to a ca. 25% lower capital cost and a ca. 15% decrease in energy consumption (170). Some other examples of existing and potential applications of the extractive distillations are listed in Table 6. 

At start-up the catalyst is reduced and then carefully conditioned on-line, for example by sulphidation of the some part of the metal components.40 Vapourised naphtha feed, together with a source of hydrogen, is then passed into the process, and potentially all the reactions listed earlier start up. The exothermic reactions of hydrocracking and hydrogenolysis must be properly controlled, but carbon laydown is inevitable from the start, and the control of its early formation is crucial to the evolution of the reforming cycle. 

The final membrane process listed in Table 3 is facilitated transport. No commercial plants are installed or are likely to be installed in the near future. Facilitated transport usually employs liquid membranes containing a complexing or carrier agent. The carrier agent reacts with one permeating component on the feed side of the membrane and then diffuses across the membrane to release the permeant on the product side of the membrane. The carrier agent is then reformed and diffuses back to the feed side of the membrane. The carrier agent thus acts as a shuttle to selectively transport one component from the feed to the product side of the membrane. 

The industrial catalyst is exposed to severe conditions in a tubular reformer involving steam partial pressures close to 30 bar and temperatures well above 800°C. The support should be able to withstand these conditions without loosing strength. Furthermore, it should not contain volatile components. Some of the support reactions are listed in Table 4.1. The conditions in prereformers are less demanding. 

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