American Petroleum Institute Research Project 42, "Properties of Hydrocarbons of High Molecular Weight," API, Division of Science and Technology, New York, 1966.  [c.7]

Hiza, M. J., A. J. Kidnay, and R. C. Miller "Equilibrium Properties of Fluid Mixtures—A Bibliography of Data on Fluids of Cryogenic Interest," NSRDS Bibliographic Series. Plenum, New York, 1975.  [c.9]

Compilation of binary experimental data reduced with the Wilson equation and, for high pressures, with a modified Redlich-Kwong equation.  [c.9]

This chapter uses an equation of state which is applicable only at low or moderate pressures. Serious error may result when the truncated virial equation is used at high pressures.  [c.38]

Since the accuracy of experimental data is frequently not high, and since experimental data are hardly ever plentiful, it is important to reduce the available data with care using a suitable statistical method and using a model for the excess Gibbs energy which contains only a minimum of binary parameters. Rarely are experimental data of sufficient quality and quantity to justify more than three binary parameters and, all too often, the data justify no more than two such parameters. When data sources (5) or (6) or (7) are used alone, it is not possible to use a three- (or more)-parameter model without making additional arbitrary assumptions. For typical engineering calculations, therefore, it is desirable to use a two-parameter model such as UNIQUAC.  [c.43]

Figure 4 shows experimental and predicted phase equilibria for the acetonitrile/benzene system at 45°C. This system exhibits moderate positive deviations from Raoult s law. The high-quality data of Brown and Smith (1955) are very well represented by the UNIQUAC equation.  [c.48]

The method described here is based on the high degree of correlation of model parameters, in this case, UNIQUAC parameters. Thus, although a certain set of binary parameters may be best for VLE data, we are able to find other sets of binary parameters for the miscible binaries which significantly improve ternary LLE prediction while only slightly decreasing accuracy of representation of the binary VLE. Fitting ternary LLE data only, may yield unrealistic parameters that predict grossly erroneous results when used in regions not identical to those employed in data reduction. By contrast, fitting ternary LLE data simultaneously with binary VLE data, effectively provides constraints on the binary parameters, preventing them from attaining arbitrary values of little physical significance. Determination of a single set of parameters which can adequately represent both VLE and LLE is particularly important in three-phase distillation.  [c.69]

Finally, Table 2 shows enthalpy calculations for the system nitrogen-water at 100 atm. in the range 313.5-584.7°K. [See also Figure (4-13).] The mole fraction of nitrogen in the liquid phase is small throughout, but that in the vapor phase varies from essentially unity at the low-temperature end to zero at the high-temperature end. In the liquid phase, the enthalpy is determined primarily by the temperature, but in the vapor phase it is determined by both temperature and composition.  [c.93]

Lemlich, R., Gottschlich, C., Hoke, R., Ind. Eng. Chem., 32 (1957).  [c.95]

The sum of the squared differences between calculated and measures pressures is minimized as a function of model parameters. This method, often called Barker s method (Barker, 1953), ignores information contained in vapor-phase mole fraction measurements such information is normally only used for consistency tests, as discussed by Van Ness et al. (1973). Nevertheless, when high-quality experimental data are available. Barker s method often gives excellent results (Abbott and Van Ness, 1975).  [c.97]

C. These values are su but are not reliable for high accuracy in molar volumes.  [c.139]

Extrapolated Data at High Temperature  [c.140]

Large errors in the low-pressure points often have little effect on phase-equilibrium calculations e.g., when the pressure is a few millitorr, it usually does not matter if we are off by 100 or even 1000%. By contrast, the high-pressure end should be reliable large errors should be avoided when the data are extrapolated beyond the critical temperature.  [c.140]

Creating and optimizing a reducible structure. In this approach, a structure known as a superstructure or hyperstructure is first created that has embedded within it all feasible process operations and all feasible interconnections that are candidates for an optimal design. Initially, redundant features are built into the structure. As an example, consider Fig. 1.7. This shows one possible structure of a process for the manufacture of benzene from the reaction between toluene and hydrogen. In Fig. 1.7, the hydrogen enters the process with a small amount of methane as an impurity. Thus in Fig. 1.7 the option is embedded of either purifying the hydrogen feed with a membrane or passing directly to the process. The hydrogen and toluene are mixed and preheated to reaction temperature. Only a furnace has been considered feasible in this case because of the high temperature required. Then two alternative reactor options, isothermal and adiabatic reactors, are embedded, and so on. Redundant features have been included in an effort to ensure that all features that could be part of an optimal solution haVe been included.  [c.9]

BYPRODUCT. If tti>a2 in Eqs. (2.16) and (2.17), the primary reaction to PRODUCT is favored by a high concentration of FEED. If ai[c.30]

Keep one of the concentrations high while maintaining the other low (this is achieved by charging one of the feeds as the reaction progresses).  [c.30]

As far as the parallel byproduct reaction is concerned, for high selectivity, if  [c.31]

If the reaction involves more than one feed, it is not necessary to operate with the same low conversion on all the feeds. Using an excess of one of the feeds enables operation with a relatively high conversion of other feed material, and still inhibits series reactions. Consider again the series reaction system from Example 2.3  [c.38]

The secondary reactions are series with respect to the chloromethane but parallel with respect to chlorine. A very large excess of methane (mole ratio of methane to chlorine on the order of 10 1) is used to suppress selectivity losses. The excess of methane has two effects. First, because it is only involved in the primary reaction, it encourages the primary reaction. Second, by diluting the product, chloromethane, it discourages the secondary reactions, which prefer a high concentration of chloromethane.  [c.40]

If Ail increases faster than k, operate at high temperature (but beware of safety and materials-of-construction constraints).  [c.42]

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]

This is an endothermic reaction accompanied by an increase in the number of moles. High conversion is favored by high temperature and low pressure. The reduction in pressure is achieved in practice by the use of superheated steam as a diluent and by operating the reactor below atmospheric pressure. The steam in this case fulfills a dual purpose by also providing heat for the reaction.  [c.44]

Very often the choice is not available. For example, if reactor temperature is above the critical temperature of the chemical species, then the reactor must be gas phase. Even if the temperature can be lowered below critical, an extremely high pressure may be required to operate in the liquid phase.  [c.45]

More often than not, solid-catalyzed reactions are multiple reactions. For reactions in parallel, the key to high selectivity is to maintain the appropriate high or low concentration levels of reactants at the catalyst surface, to encourage the desired reaction, and to discourage the byproduct reactions. For reactions in series, the key is to avoid the mixing of fluids of different compositions. These arguments for the gross flow pattern of fluid through any reactor have already been developed.  [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]

An initial guess for the reactor conversion is very difficult to make. A high conversion increases the concentration of monoethanolamine and increases the rates of the secondary reactions. As we shall see later, a low conversion has the effect of decreasing the reactor capital cost but increasing the capital cost of many other items of equipment in the flowsheet. Thus an initial value of 50 percent conversion is probably as good as a guess as can be made at this stage.  [c.51]

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]

Tubular reactors. Although tubular reactors often take the actual form of a tube, they can be any reactor in which there is steady movement in one direction only. The tubes may be arranged in parallel, in a construction similar to a shell-and-tube heat exchanger. This design is used when external heating or cooling is required. In high-temperature reactions, the tubes are constructed inside a furnace.  [c.54]

Because the characteristic of tubular reactors approximates plug-flow, they are used if careful control of residence time is important, as in the case where there are multiple reactions in series. High surface area to volume ratios are possible, which is an advantage if high rates of heat transfer are required. It is sometimes possible to approach isothermal conditions or a predetermined temperature profile by careful design of the heat transfer arrangements.  [c.54]

Tubular reactors, as previously stated, are also advantageous for high-pressure reactions where smaller-diameter cylindrical vessels can be used to allow thinner vessel walls. Tubular reactors should be avoided when carrying out multiphase reactions, since it is often difficult to achieve good mixing between phases.  [c.55]

However, if high rates of heat transfer are required or the catalyst requires frequent regeneration, then fixed beds are not suitable, and under these circumstances, a fluidized bed is preferred, as we shall discuss later.  [c.56]

In addition to the advantage of high heat transfer rates, fluidized beds are also useful in situations where catalyst particles need frequent regeneration. Under these circumstances, particles can be removed continuously from the bed, regenerated, and recycled back to the bed. In exothermic reactions, the recycling of catalyst can be  [c.58]

The solid particles are fluidized by air and fuel, which are fed to the bed and burnt to produce the high temperatures necessary for the reaction.  [c.60]

Kilns. Reactions involving free-flowing solid, paste, and slurry materials can be carried out in kilns. In a rotary kiln, a cylindrical shell is mounted with its axis making a small angle to horizontal and rotated slowly. The material to be reacted is fed to the elevated end of the kiln and tumbles down the kiln as a result of the rotation. The behavior of the reactor usually approximates plug flow. High-temperature reactions demand refractory lined steel shells and are usually heated by direct firing. An example of a reaction carried out in such a device is the production of hydrogen fluoride  [c.60]

A high degree of correlation may be beneficial. When the parameters are strongly related, some linear combination of the two parameters may represent the data as well as do the individual parameters. In that case a method similar to that of Bruin and Praus-  [c.104]

Maximum selectivity requires a minimum ratio rjr in Eq. (2.17). A high conversion in the reactor tends to decrease Cfeed- Thus  [c.26]

Fixed-bed catalytic reactors. Tubular reactors are also used extensively for catal3dic reactions. Here the reactor is packed with particles of solid catalyst. Most designs approximate to plug-flow behavior. Figure 2.6 shows four possible arrangements for flxed-bed reactors. The first (Fig. 2.6a) is similar to a shell-and-tube exchanger in which the tubes are packed with catalyst. The second (Fig. 2.66) has the tubes constructed inside a furnace for high temperatures. The third (Fig. 2.6c) is a series of adiabatic beds with intermediate cooling or heating to maintain temperature control. The heating or cooling can be effected by internal or external exchangers. The fourth (Fig. 2.6rf) uses direct injection of a fluid to perform heat transfer. The injected fluid might typically be cold fresh feed or cooled recycled product to control the temperature rise in an exothermic reaction. This is known as cold-shot cooling. Many other arrangements are possible.  [c.55]

See pages that mention the term Hassager : [c.69]    [c.140]    [c.141]    [c.178]    [c.205]    [c.20]    [c.20]    [c.30]    [c.41]    [c.41]    [c.44]    [c.44]    [c.49]    [c.69]   
Practical aspects of finite element modelling of polymer processing (2002) -- [ c.15 , c.16 , c.139 , c.188 ]