Staging, reactor

Rtr a feed temperature of 300 K. the adiabatic equilibrium temperature is 463 K and the cone xmdtng adiabatic equilibrium conversion is only 0.42. 

If adding inerts or lowering the entering temperature is not feasible then one should consider reactor staging. 

Interstage cooling used for cxoiheraiic reversible reactions 

The first reaction step ffr,) is slow compared to the second step, and each step is highly endothermic. The allowable temperature range for which this reaction can be carried out is quite narrow Above 530 C undesirable side reaction.s occur, and below 430°C the reaction virtually does not take place. A typical feed stock might consist of 75% straight chains. 15% naphthas, and 10% aromatics. 

Fhuire 11-7 inicrsiage healing for gasoline pnKhictioa in moving-bed reactors. 

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The diagram of the IGT cold-gas recycle process includes four reactor stages in series (Figure 3). Note that the concept can be applied to any number of stages. 

Since the syrup solids increase generally stepwise while proceeding from one compartment to the next, and the contents of each compartment are boiling under constant pressure, the temperature in each succeeding compartment increases. It is claimed that the linear flow behavior provided by the reactor staging results in more favorable rubber phase morphology than would be the case if the second reactor were operated as a single CSTR. 

There are several advantages of the use of HPLC for process monitoring. First, HPLC provides both qualitative and quantitative information about a process. At the research or pilot reactor stage of development, real time monitoring increases research efficiency and provides the data for process optimization. Second, because HPLC permits continuous real-time monitoring of reactors or other process components, process upsets that might go... 

In a typical process, the conversion of isobutene in the reactor stage is 97 per cent. The product is separated from the unreacted methanol and any C4 s by distillation. The essentially pure, liquid, MTBE leaves the base of the distillation column and is sent to storage. The methanol and C4 s leave the top of the column as vapour and pass to a column where the methanol is separated by absorption in water. The C4 s leave the top of the absorption column, saturated with water, and are used as a fuel gas. The methanol is separated from the water solvent by distillation and recycled to the reactor stage. The water, which leaves the base of the column, is... 

A few words concerning the results of our analyses in Illustrations 12.8 and 12.9 are in order. Obviously, better estimates of the catalyst requirements could be obtained by using smaller conversion increments. We have not attempted to fully optimize the reactor stages in terms of catalyst minimization. Furthermore, we have again neglected pressure drop in each stage. Further calculations would remedy each of the aforementioned shortcomings of the analysis. They are readily accomplished with the aid of machine computation. 

We particularly like these three flow or reacting patterns because they are easy to treat (it is simple to find their performance equations) and because one of them often is the best pattern possible (it will give the most of whatever it is we want). Later we will consider recycle reactors, staged reactors, and other flow pattern combinations, as well as deviations of real reactors from these ideals. 

You wish to design a plant to produce 100 tons/day of ethylene glycol from ethane, air, and water. The plant has three reactor stages, ethane dehydrogenation, ethylene oxidation, and ethylene oxide hydration. 

Each arrow indicates a single reaction step (frequently with several reactors), and after every reactor stage the products are separated, reactants are recycled, and new feed is added for entry into the next reactor stage. In Table 34 we summarize each of these processes. 

For single and multiple reactor stages we sketch reactors and separation units as shown in Figure 3-20. We assume a first reactor running the reaction... 

The next simplest reactor type is a sequence of adiabatic reactors with interstage heating or cooling between reactor stages. We can thus make simple reactors with no provision for heat transfer and do the heat management in heat exchangers outside the reactors. 

Endothermic reactions can also be run with interstage heating. An example we have considered previously is the catalytic reforming of naphtha in petroleum refining, which is strongly endothermic. These reactors are adiabatic packed beds or moving beds (more on these in the next chapter) in which the reactant is preheated before each reactor stage. 

The activity of each compound ax in the reactor stage (R01) is calculated according to Equation 6 with the respective saturation pressure Ppsatx determined at the temperature of the bioreactor. 

Fig. 1.2. Schematic flow configurations of heat-integrated processes for coupling endothermic and exothermic reactions, (a) Countercurrent flow of process streams, (b) Cocurrent flow of the process streams in the reactor stages and heat recovery in separate circuits.

As indicated by this schematic representation, different configurations vary with respect to the degree of coupling between the process streams. The strongest coupling occurs in the simultaneous mode, where chemical and thermal interaction occurs between the process streams. In contrast to this, the counter-cocurrent concept features only thermal interaction between the process streams localized in the reactor stage. 

From our discussion of reactor staging in Chapter 2, we could have predicted that the senes arrangement would have given the higher conversion. 

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