Reactors flow-sheet calculations

For a power plant including a membrane reactor with membranes with a selectivity of 15 the efficiency of the total system has been determined through flow sheet calculations. In these calculations the requirements and the demands of the membrane reactor and the rest of the system must match, so one or more iterative calculations is necessary to optimise the total system. The results of the calculations after optimisation are presented in Table 14.11 in which three... 

Similarly a hypothetical spHtter must be defined when a stream is spHt. Furthermore, control units ate identified in calculations flow diagrams when temperatures, pressures, and flows of streams ate controlled on the basis of variables in other parts of flow sheets. Sometimes variables such as product specifications and reactor yields can be represented as hypothetical control units. 

As gaschromatography. with its discontinuous integration results (calculated by a PC-XT computer) was applied for the analysis of the reaction,a conventional control-algorithm could not be used instead a model-based algorithm had been implemented.Fig 3 shows a flow sheet of this algorithm.lt consists of the actual process and a simplified model of the reaction and reactor. The chemical reaction taking place in the reactor is perfectly described by the feed composition c0, having... 

Two semi-quantitative models describing the reactor and membrane performance were used to evaluate the overall performance. The reactor was modelled using the flow-sheeting package PRO II. A membrane model was used which describes both the transport through the membranes and transport along the membrane. These models are described in Ref. [33]. Based on the Oleflex process the following boundary conditions were chosen for the calculations ... 

Ideally you would have calculated the equilibrium in the reactor, too. Then you would have three interacting iterations, and it would be the rare problem that Excel could solve. The difficulty is that, during the iterations, the values may be physically unrealistic. Then, the equilibrium relation or the Rachford-Rice equation gives even more unrealistic values. Programs such as Aspen Plus can realize this and take precautionary steps to avoid it. As the flow sheet gets more and more complicated, and involves more and more thermodynamics, the power of Aspen Plus is welcome. See Chapters 6 and 7 for examples. 

One promising flow sheet for production of hydrogen with the help of thermal energy is given in Figure 14.11. The last step in this process, the regeneration of sulphuric acid, was studied by van der Ham and coworkers. The authors followed the procedure outlined above, and calculated first the profiles in intensive variables, as obtained from the state-of-the-art reactor design. The results for the... 

Figure 6.11.13 shows a flow sheet of a FT fixed bed reactor with recycle of unconverted syngas. To simplify the subsequent calculations, we assume that the recycle gas only consists of unconverted CO and H2. In reality, it also contains other gases like CH4 and CO2 and a purge stream is needed to limit the concentration of inerts. We also assume that the temperature is constant, which is not true, as examined in Section 6.11.1.5. 

FIGURE 9.10 (a) Flow distribution calculated in the monolith channels by CFD and (b) a simplified flow sheet of the monolith system described as parallel tube reactors and stirred mixing volume. 

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