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]

The accuracy of the calculations depends directly on the reliability of the experimental data. The correlated data presented in the Appendices were taken from standard literature sources while these data are probably reliable for most fluids, it is not possible to be certain that they are reliable for all.  [c.95]

We have repeatedly observed that the slowly converging variables in liquid-liquid calculations following the isothermal flash procedure are the mole fractions of the two solvent components in the conjugate liquid phases. In addition, we have found that the mole fractions of these components, as well as those of the other components, follow roughly linear relationships with certain measures of deviation from equilibrium, such as the differences in component activities (or fugacities) in the extract and the raffinate.  [c.124]

Hgure 1.1 Synthesis is the creation of a process to transform feed streams into product streams. Simulation predicts how it would behave if it was constructed.  [c.2]

This text will attempt to develop an understanding of the concepts required at each stage during the creation of a chemical process design.  [c.3]

Given that the objective is to manufacture a certain product, there are often a number of alternative reaction paths to that product. Reaction paths which use the cheapest raw materials and produce the smallest quantities of byproducts are to be preferred. Reaction paths which produce significant quantities of unwanted byproducts should especially be avoided, since they create significant environmental problems.  [c.16]

Three idealized models are used for the design of reactors. " In the first (Fig. 2.1a), the ideal batch model, the reactants are charged at the beginning of the operation. The contents are subjected to perfect mixing for a certain period, after which the products are discharged. Concentration changes with time, but the perfect mixing ensures that at any instant the composition and temperature throughout the reactor are both uniform.  [c.28]

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]

If the mixture to be separated is homogeneous, a separation can only be performed by the addition or creation of another phase within the system. For example, if a gaseous mixture is leaving the reactor, another phase could be created by partial condensation. The vapor resulting from the partial condensation will be rich in the more volatile components and the liquid will be rich in the less volatile components, achieving a separation. Alternatively, rather than creating another phase, one can be added to the gaseous mixture, such as a solvent which would preferentially dissolve one or more of the components from the mixture. Further separation is required to separate the solvent from the process materials allowing recycle of the solvent, etc. A number of physical properties can be exploited to achieve the separation of homogeneous mixtures.If a heterogeneous or multiphase mixture leaves the reactor, then separation can be done physically by exploiting differences in density between the phases.  [c.67]

As pointed out previously, the separation of homogeneous fluid mixtures requires the creation or addition of another phase. The most common method is by repeated vaporization and condensation— distillation. The three principal advantages of distillation are  [c.74]

Given these degrees of freedom, how can an initialization be made for the design The most significant degree of freedom is the choice of number of stages. If the evaporator is operated using hot and cold utility, as the number of stages is increased, a tradeoff might be expected, as shown in Fig. 3.14. Here, starting with a single stage, it has a low capital cost but requires a large energy cost. Increasing the stages to two decreases the energy cost in return for a small increase in capital cost, and the total cost decreases. However, as the stages are increased, the increase in capital cost at some point no longer compensates for the corresponding decrease in energy cost, and the total cost increases. Hence there is an optimal number of stages. However, no attempt should be made to carry out this optimization at this point, since the design is almost certain to change significantly when heat integration is considered later (see Chap. 15).  [c.87]

Flammability limits. A flammable gas will bum in air only over a limited range of composition. Below a certain concentration of the flammable gas, the lower flammability limit, the mixture is too lean to burn, i.e., lacks fuel. Above a certain concentration, the upper flammability limit, it is too rich to burn, i.e., lacks oxygen. Concentrations between these limits constitute the flammable range.  [c.256]

High pressure. Most process plant operates at pressures below 250 bar, but certain processes, such as high-pressure polyethylene plants, operate at pressures up to about 3000 bar. The use of high pressure greatly increases the stored energy in the plant. Although high pressures in themselves do not pose serious problems in materials of construction, the use of high temperatures, low temperatures, or corrosive chemicals together with high pressure does. With high-pressure operation the problem of leaks becomes much more serious, since this increases the mass flow rate of fluid which can leak out through a given hole. This is particularly so when the fluid is a flashing liquid.  [c.267]

This is the order in which we should look to solve the problem of SO,c emissions. We should try to prevent creation of the waste, since treating the waste tends only to move the problem rather than solve it.  [c.306]

While the BOD test gives a good indication of the effect the effluent will have on the environment, it requires 5 days to carry out. The chemical oxygen demand (COD) test has been developed to give a more rapid result. In the COD test, acidic oxidation with potassium dichromate is used. COD results are generally higher than BOD results because the COD test oxidizes materials that are only slowly biodegradable. Although the COD test provides a very strong oxidizing environment, certain compounds are not oxidized.  [c.308]

The approach to heat exchanger network design discussed so far is based on the creation of an irreducible structure. No redundant features were included. Of course, when the network is optimized, some of the features might be removed by the optimization. The scope for the optimization to remove features results from the assumptions made during the creation of the initial structure. However, no attempt was made to deliberately include redundant features.  [c.394]

There can be an element of maintenance costs that is fixed and an element which is variable. Fixed maintenance costs cover routine maintenance such as regular maintenance on safety valves which must be carried out irrespective of the rate of production. There also can be an element of maintenance costs which is variable. This arises from the fact that certain items of equipment can need more maintenance as the production rate increases. Also, royalties which cover the cost of purchasing another company s process technology may have different bases. Royalties may be a variable cost, since they can sometimes be paid in proportion to the rate of production. Alternatively, the royalty might be a single-sum payment at the beginning of the project. In this case, the single-sum payment will become part of the project s capital investment. As such, it will be included in the annual capital repayment, and this becomes part of the fixed cost.  [c.406]

Chemical process design starts with the selection of a series of processing steps and their interconnection into a flowsheet to transform raw materials into desired products. Whereas a great emphasis in chemical engineering traditionally has heen placed on the analysis or simulation of flowsheets, the creation or synthesis of flowsheets has received, hy comparison, little attention. Yet the decisions made during the synthesis of the flowsheet are of paramount importance in determining the economic viability, safety, and environmental impact of the flnal design. This text will concentrate on developing an understanding of the concepts required at each stage of the synthesis of process flowsheets.  [c.473]

Certain other amino-acids occur in a few proteins, and others, not necessarily a- or l-amino-acids, are found naturally in the free state or as constituents of peptides.  [c.29]

As constituents of proteins the amino-acids are important constituents of the food of animals. Certain amino-acids can be made in the body from ammonia and non-nitrogenous sources others can be made from other amino-acids, e.g. tyrosine from phenylalanine and cystine from methionine, but many are essential ingredients of the diet. The list of essential amino-acids depends partly on the species. See also peptides and proteins.  [c.29]

Bragg equation When a beam of monochromatic X-rays of wavelength / impinges on a crystal, strong scattering occurs in certain directions only this is the phenomenon of X-ray difTraction. For diffraction the path difference between waves scattered from successive planes of atoms in the crystal must equal an integral number of wavelengths, n n = 1,2,3,.. .). This condition is expressed by the equation  [c.66]

In certain crystals, e.g. in quartz, there is chirality in the crystal structure. Molecular chirality is possible in compounds which have no chiral carbon atoms and yet possess non-superimposable mirror image structures. Restricted rotation about the C=C = C bonds in an allene abC = C = Cba causes chirality and the existence of two optically active forms (i)  [c.91]

It is strictly for convenience that certain conventions have been adopted in the choice of a standard-state fugacity. These conventions, in turn, result from two important considerations (a) the necessity for an unambiguous thermodynamic treatment of noncondensable components in liquid solutions, and (b) the relation between activity coefficients given by the Gibbs-Duhem equation. The first of these considerations leads to a normalization for activity coefficients for nonoondensable components which is different from that used for condensable components, and the second leads to the definition and use of adjusted or pressure-independent activity coefficients. These considerations and their consequences are discussed in the following paragraphs.  [c.17]

When separating a three-component mixture using simple columns, there are only two possible sequences (see Fig. 5.1). Consider the first characteristic of simple columns. A single feed is split into two products. As a first alternative to two simple columns, the possibilities shown in Fig. 5.10 can be considered. Here, three products are taken from one column. The designs are in fact both feasible and cost-effective when compared with simple arrangements on a standalone basis (i.e., reboilers and condensers operating on utilities) for certain ranges of conditions. If the feed is dominated by the middle product (typically more than 50 percent of the feed) and the heaviest product is present in small quantities (typically less than 5 percent), then the arrangement shown in Fig. 5.10a can be an attractive option. The heavy product must find its way down the column past the sidestream. Unless the heavy product has a small flow and the middle product a high flow, a reasonably pure middle product cannot be achieved. In these circumstances, the sidestream is usually taken as a vapor product to obtain a reasonably pure sidestream.  [c.147]

Triaceiin is about 90% glycerol triacetate and 10% diacetate. Used as a plasticizer for lacquers and as a solvent for certain gums and resins.  [c.11]

Aerosol is also a trade name for certain wetting agents, most of which are esters of sodium sulphosuccinic acid.  [c.17]

Bafmer series Frequencies of certain lines in the spectrum of hydrogen are simply related to each other, and can be expressed by a general formula. One group of lines is termed the Balmer series. Other series were later discovered in the spectrum of hydrogen by Lyman, Paschen, Brackett and Pfund.  [c.50]

A white solid, m.p. 178 C. Primarily of interest as a brominaling agent which will replace activated hydrogen atoms in benzylic or allylic positions, and also those on a carbon atom a to a carbonyl group. Activating influences can produce nuclear substitution in a benzene ring and certain heterocyclic compounds also used in the oxidation of secondary alcohols to ketones.  [c.69]

Chloroform is a potent volatile anaesthetic, but is little used due to its potential hepato-toxicity. It is used principally for the manufacture of chlorofluorohydrocarbon refrigerants ( Arctons and Freons ) and certain polymers.  [c.94]

See pages that mention the term Crithmene : [c.26]    [c.9]    [c.14]    [c.16]    [c.21]    [c.29]    [c.35]    [c.39]    [c.43]    [c.46]    [c.50]    [c.59]    [c.71]    [c.79]    [c.79]    [c.84]    [c.88]    [c.94]    [c.101]    [c.105]    [c.110]    [c.110]   
The chemistry of essential oils and artificial perfumes Volume 2 (1922) -- [ c.75 ]