Polyox


Compilation of vapor-liquid equilibrium data data are correlated with Redlich-Kister equation (in Polish).  [c.10]

For a noncondensable component, therefore, it is convenient to use a normalization different from that given by Equation (13) in its place we use  [c.18]

Binary data only. ----- One tie-line plus binary data.  [c.70]

On triangular diagrams, comparisons of calculated and experimental results can be deceiving. A more realistic representation is provided by Figure 18, comparing experimental solute distributions with those calculated from the UNIQUAC equation for four ternary systems. For three of these systems, calculations were made using the parameters determined from binary data plus one ternary tie line however, for the 2,2,4-trimethylpen-tane-furfural-cyclohexane system, parameters were obtained from binary data alone. With the exception of the region very near the plait point, calculated distributions are good. Fortunately, commercial extractions are almost never conducted near the plait point since the small density difference in the plait-point region causes hydrodynamic difficulties (flooding).  [c.71]

Glossary of Principal Variable Names (plus see common storage descriptions)  [c.296]

Glossary of Principal Variable Names (plus see common storage descriptions)  [c.300]

Glossary of Principal Variable Names (plus see common storage descriptions)  [c.303]

Glossary of Principal Variable Names (plus see common storage descriptions)  [c.311]

Since process design starts with the reactor, the first decisions are those which lead to the choice of reactor. These decisions are among the most important in the whole design. Good reactor performance is of paramount importance in determining the economic viability of the overall design and fundamentally important to the environmental impact of the process. In addition to the desired products, reactors produce unwanted byproducts. These unwanted byproducts create environmental problems. As we shall discuss later in Chap. 10, the best solution to environmental problems is not elaborate treatment methods but not to produce waste in the first place.  [c.15]

In the third model (Fig. 2.1c), the plug-flow model, a steady uniform movement of the reactants is assumed, with no attempt to induce mixing along the direction of flow. Like the ideal batch reactor, the residence time in a plug-flow reactor is the same for all fluid elements. Plug-flow operation can be approached by using a number of continuous well-mixed reactors in series (Fig. 2.Id). The greater the number of well-mixed reactors in series, the closer is the approach to plug-flow operation.  [c.29]

In general terms, if the reaction to the desired product has a higher order than the byproduct reaction, use a batch or plug-flow reactor. If the reaction to the desired product has a lower order than the byproduct reaction, use a continuous well-mixed reactor.  [c.30]

Multiple reactions in series producing byproducts. Consider the series reaction system from Eq. (2.18). For a certain reactor conversion, the FEED should have a corresponding residence time in the reactor. In the continuous well-mixed reactor, FEED can leave the instant it enters or remains for an extended period. Similarly, PRODUCT can remain for an extended period or leave immediately. Substantial fractions of both FEED and PRODUCT leave before and after what should be the specific residence time for a given conversion. Thus the continuous well-mixed model would be expected to give a poorer selectivity than a batch or plug-flow reactor for a given conversion. A batch or plug-flow reactor should be used for multiple reactions in series.  [c.31]

The series byproduct reaction requires a plug-flow reactor. Thus, for the mixed parallel and series system above, if  [c.31]

But what is the correct choice a [c.31]

A plug-flow reactor with a recycle (Fig. 2.36)  [c.33]

A series combination of plug-flow and continuous well-mixed reactors (Fig. 2.3c and d)  [c.33]

Polymerization reactions. Polymers are characterized by the distribution of molecular w eight about the mean as well as by the mean itself. The breadth of this distribution depends on whether a batch or plug-flow reactor is used on the one hand or a continuous well-mixed reactor on the other. The breadth has an important influence on the mechanical and other properties of the polymer, and this is an important factor in the choice of reactor.  [c.33]

The liquid used for the direct heat transfer should be chosen such that it can be separated easily from the reactor product and so recycled with the minimum expense. Use of extraneous materials, i.e., materials that do not already exist in the process, should be avoided because it is often difficult to separate and recycle them with high efficiency. Extraneous material not recycled becomes an effluent problem. As we shall discuss later, the best way to deal with effluent problems is not to create them in the first place.  [c.43]

Catalytic gas-phase reactions play an important role in many bulk chemical processes, such as in the production of methanol, ammonia, sulfuric acid, and nitric acid. In most processes, the effective area of the catalyst is critically important. Since these reactions take place at surfaces through processes of adsorption and desorption, any alteration of surface area naturally causes a change in the rate of reaction. Industrial catalysts are usually supported on porous materials, since this results in a much larger active area per unit of reactor volume.  [c.47]

As well as depending on catalyst porosity, the reaction rate is some function of the reactant concentrations, temperature, and pressure. However, this function may not be as simple as in the case of uncatalyzed reactions. Before a reaction can take place, the reactants must diffuse through the pores to the solid surface. This results in a situation where either reaction or diffusion can be the rate-limiting process. Alternatively, it may be that reaction speed and diffusion have an almost equal effect. If reaction is rate limiting, as tends to occur in a lower temperature range, the effects of concentration and temperature are those typical of chemical reaction. On the other hand, if diffusion is rate limiting, as tends to occur in a higher temperature range, the effects of concentration and temperature are those characteristic of diffusion. In the transitional region, where both reaction and diffusion affect the overall rate, the effects of temperature and concentration are often rather complex.  [c.47]

Catalytic degradation. The performance of most catalysts deteriorates with time. The rate at which the deterioration takes place is another important factor in the choice of catalyst and the choice of reactor conditions. Deterioration in performance lowers the rate of reaction, which, for a given reactor design, manifests itself as a lowering of the conversion. This often can be compensated by increasing the temperature of the reactor. However, significant increases in temperature can degrade selectivity considerably and often accelerate the mechanisms that cause catalyst degradation. Loss of catalyst performance can occur in a number of ways a. Physical loss. Physical loss is particularly important with homogeneous catalysts, which need to be separated from reaction products and recycled. Unless this can be done with high efficiency, it leads to physical loss (and subsequent environmental problems). However, physical loss as a problem is not restricted to homogeneous catalysts. It also can be a problem with heterogeneous catalysts. This is particularly the case when catalytic fluidized-bed reactors are employed. Attrition of the particles causes the catalyst particles to be broken down in size. Particles which are carried over from the fluidized bed are normally separated from  [c.48]

Solution We wish to avoid as much as possible the production of di- and triethanolamine, which are formed by series reactions with respect to monoethanolamine. In a continuous well-mixed reactor, part of the monoethanolamine formed in the primary reaction could stay for extended periods, thus increasing its chances of being converted to di- and triethanolamine. The ideal batch or plug-flow arrangement is preferred, to carefully control the residence time in the reactor.  [c.50]

Another possibility to improve selectivity is to reduce the concentration of monoethanolamine in the reactor by using more than one reactor with intermediate separation of the monoethanolamine. Considering the boiling points of the components given in Table 2.3, then separation by distillation is apparently possible. Unfortunately, repeated distillation operations are likely to be very expensive. Also, there is a market to sell both di- and triethanolamine, even though their value is lower than that of monoethanolamine. Thus, in this case, repeated reaction and separation are probably not justified, and the choice is a single plug-flow reactor.  [c.51]

Solution The byproduct reactions to avoid are all series in nature. This suggests that we should not use a continuous well-mixed reactor but rather use either a batch or plug-flow reactor.  [c.52]

Stirred-tank reactors become unfavorable if the reaction must take place at high pressure. Under high-pressure conditions, a small-diameter cylinder requires a thinner wall than a large-diameter cylinder. Under high-pressure conditions, use of a tubular reactor is preferred, as described in the next section, although mixing problems with heterogeneous reactions and other factors may prevent this. Another important factor to the disadvantage of the continuous stirred-tank reactor is that for a given conversion it requires a large inventory of material relative to, say, a tubular reactor. This is not desirable for safety reasons if the reactants or products are particularly hazardous.  [c.53]

Design starts at the reactor because it is likely to be the only place in the process where raw materials are converted into desired products. The reactor design dictates the separation and recycle problem. The reactor design and separation and recycle problem together dictate the heating and cooling duties for the heat exchanger network. Those duties which cannot be satisfied by heat recovery dictate the need for external utilities. This hierarchy is represented by the layers in the onion diagram (see Fig. 1.6).  [c.13]

Clearly, the highest rate of reaction is maintained by the highest concentration of feed (Cfeed> kmolm ). In the continuous well-mixed reactor, the incoming feed is instantjy diluted by the product that has already been formed. The rate of reaction is thus lower in the continuous well-stirred reactor than in the ideal batch and plug-flow reactors, since it operates at the low reaction rate corresponding with the outlet concentration of feed. Thus the continuous well-stirred model requires a greater volume than the ideal batch and plug-flow reactors. Consequently, for single Reactions, the ideal batch or plug-flow reactors are preferred.  [c.29]

Multiple reactions in parallel producing byproducts. Consider again the system of parallel reactions from Eqs. (2.16) and (2.17). A batch or plug-flow reactor maintains higher average concentrations of feed (Cfeed) than a continuous well-mixed reactor, in which the incoming feed is instantly diluted by the PRODUCT and  [c.29]

Choosing to use a continuous rather than a batch reactor, plug-flow behavior can be approached using a series of continuous well-mixed reactors. This again sdlows concentrated sulfuric acid to be added as the reaction progresses, in a similar way as suggested for some parallel systems in Fig. 2.2. Breaking the reactor down into a series of well-mixed reactors also allows good temperature control, s we shall discuss later.  [c.52]


See pages that mention the term Polyox : [c.8]    [c.70]    [c.115]    [c.122]    [c.125]    [c.207]    [c.6]    [c.28]    [c.28]    [c.30]    [c.30]    [c.31]    [c.31]    [c.32]    [c.32]    [c.32]    [c.33]    [c.33]    [c.33]    [c.34]    [c.34]    [c.47]   
Plastics materials (1999) -- [ c.547 ]