If we vary the composition of a liquid mixture over all possible composition values at constant temperature, the equilibrium pressure does not remain constant. Therefore, if integrated forms of the Gibbs-Duhem equation [Equation (16)] are used to correlate isothermal activity coefficient data, it is necessary that all activity coefficients be evaluated at the same pressure. Unfortunately, however, experimentally obtained isothermal activity coefficients are not all at the same pressure and therefore they must be corrected from the experimental total pressure P to the same (arbitrary) reference pressure designated P. This may be done by the rigorous thermodynamic relation at constant temperature and composition  [c.20]

To illustrate the criterion for parameter estimation, let 1, 2, and 3 represent the three components in a mixture. Components 1 and 2 are only partially miscible components 1 and 3, as well as components 2 and 3 are totally miscible. The two binary parameters for the 1-2 binary are determined from mutual-solubility data and remain fixed. Initial estimates of the four binary parameters for the two completely miscible binaries, 1-3 and 2-3, are determined from sets of binary vapor-liquid equilibrium (VLE) data. The final values of these parameters are then obtained by fitting both sets of binary vapor-liquid equilibrium data simultaneously with the limited ternary tie-line data.  [c.67]

Renon, H., Prausnitz, J. M., Ind. Eng. Chem. Process Des. Dev.,  [c.80]

If the parameters were to become increasingly correlated, the confidence ellipses would approach a 45 line and it would become impossible to determine a unique set of parameters. As discussed by Fabrics and Renon (1975), strong correlation is common for nearly ideal solutions whenever the two adjustable parameters represent energy differences.  [c.104]

An apparent systematic error may be due to an erroneous value of one or both of the pure-component vapor pressures as discussed by several authors (Van Ness et al., 1973 Fabries and Renon, 1975 Abbott and Van Ness, 1977). In some cases, highly inaccurate estimates of binary parameters may occur. Fabries and Renon recommend that when no pure-component vapor-pressure data are given, or if the given values appear to be of doubtful validity, then the unknown vapor pressure should be included as one of the adjustable parameters. If, after making these corrections, the residuals again display a nonrandom pattern, then it is likely that there is systematic error present in the measurements.  [c.107]

B. Wilson Equation (Wilson, 1964 Renon and Prausnitz, 1969)  [c.214]

C. NRTL Equation (Renon and Prausnitz, 1968)  [c.214]

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 separation of suspended solid particles from a liquid by gravity settling into a clear fiuid and a slurry of higher solids content is called sedimentation. Figure 3.2 shows a sedimentation device known as a thickener, the prime function of which is to produce a more concentrated slurry. The feed slurry in Fig. 3.2 is fed at the center of the tank below the surface of the liquid. Clear liquid overflows from the top edge of the tank. A slowly revolving rake removes the thickened slurry or sludge and serves to scrape the sludge toward the center of the base for removal. It is common in such operations to add a flocculating agent to the mixture to assist the settling process. This agent has the effect of neutralizing electric charges on the particles that cause them to repel each other and remain dispersed. The effect is to form aggregates or floes which, because they are larger in size, settle more rapidly. When the prime function of the sedimentation is to remove solids from a liquid rather than to produce a more concentrated solid-liquid mixture, the device is known as a clarifier. Clarifiers are often similar in design to thickeners.  [c.69]

Rmin is calculated from the binary form of the Underwood equation applied to the key components  [c.136]

Reactors. Perhaps the worst safety problem that can occur with reactors occurs when an exothermic reaction generates heat at a faster rate than the cooling can remove it. Such runaway reactions are usually caused by coolant failure, perhaps for a temporary period, or reduced cooling capacity due to perhaps a pump failure in the cooling water circuit. The runaway happens because the rate of reaction, and hence the rate of heat generation, increases exponentially with temperature, whereas the rate of cooling increases only linearly with temperature. Once heat generation exceeds available cooling capacity, the rate of temperature rise becomes progressively faster." If the energy release is large enough, liquids will vaporize, and overpressurization of the reactor follows.  [c.262]

Clearly, the potential hazard from runaway reactions is reduced by reducing the inventory of material in the reactor. Batch operation requires a larger inventory than the corresponding continuous reactor. Thus there may be a safety incentive to change from batch to continuous operation. Alternatively, the batch operation can be  [c.262]

The use of an unnecessarily hot utility or heating medium should be avoided. This may have been a major factor that led to the runaway reaction at Seveso in Italy in 1976, which released toxic material over a wide area. The reactor was liquid phase and operated in a stirred tank (Fig. 9.3). It was left containing an uncompleted batch at around 160 C, well below the temperature at which a runaway reaction could start. The temperature required for a runaway reaction was around 230 C.  [c.264]

In this accident, the steam was isolated from the reactor containing the unfinished batch and the agitator was switched ofiF. The steam used to heat the reactor was the exhaust from a steam turbine at 190 C but which rose to about 300°C when the plant was shutdown. The reactor walls below the liquid level fell to the same temperature as the liquid, around 160°C. The reactor walls above the liquid level remained hotter because of the high-temperature steam at shutdown (but now isolated). Heat then passed by conduction and radiation from the walls to the top layer of the stagnant liquid, which became hot enough for a runaway reaction to start (see Fig. 9.3). Once started in the upper layer, the reaction then propagated throughout the reactor. If the steam had been cooler, say, 180 C, the runaway could not have occurred.  [c.264]

The effects of pollution can be direct, such as toxic emissions providing a fatal dose of toxicant to fish, animal life, and even human beings. The effects also can be indirect. Toxic materials which are nonbiodegradable, such as waste from the manufacture of insecticides and pesticides, if released to the environment, are absorbed by bacteria and enter the food chain. These compounds can remain in the environment for long periods of time, slowly being concentrated at each stage in the food chain until ultimately they prove fatal, generally to predators at the top of the food chain such as fish or birds.  [c.273]

Plug-flow reactors have a decreasing concentration gradient from inlet to outlet, which means that toxic compounds in the feed remain undiluted during their passage along the reactor, and this may inhibit or kill many of the microorganisms within the  [c.315]

This result is useful in making the following observations Ultimately, A shells will have to be converted into an integer, and streams contributing a small fractional number of shells, much fewer than 1.0 shells, will nevertheless eventually require at least one whole shell in the design. Therefore, if many such small streams exist in a problem, they only make a small contribution to iVsHELLs but will actually require several shells between them in the design. There is thus the possibility of a significant underestimate if A shells is simply made integer. To overcome the problem, each ream i with A (i)<1.0 should have N i) reset to 1.0 in Eq. (E.4) before converting A shells to an integer.  [c.439]

Robin Smith is a Senior Lecturer in Chemical Engineering at the University of Manchester Institute of Science and Technology in the United Kingdom, as well as a consultant for major companies worldwide. He previously worked in process investigation and design with Rohm Haas, and in process modeling and the development of process integration techniques with ICI. The author of many technical papers. Dr. Smith is a Fellow of the Institution of Chemical Engineers.  [c.460]

Carbon dioxide, COj. Sublimes — 78 5 C. A colourless gas at room temperature, occurs naturally and plays an important part in animal and plant respiration. Produced by the complete combustion of carbon-containing materials (industrially from flue gases and from synthesis gas used in ammonia production) and by heating metal carbonates or by  [c.81]

Cyanogen fluoride, FCN. Colourless gas (b.p. — 46 C) prepared by pyrolysis of cyanuric fluoride. Polymerizes to (FCN), cyanuric fluoride, at room temperature.  [c.120]

However, if the liquid solution contains a noncondensable component, the normalization shown in Equation (13) cannot be applied to that component since a pure, supercritical liquid is a physical impossibility. Sometimes it is convenient to introduce the concept of a pure, hypothetical supercritical liquid and to evaluate its properties by extrapolation provided that the component in question is not excessively above its critical temperature, this concept is useful, as discussed later. We refer to those hypothetical liquids as condensable components whenever they follow the convention of Equation (13). However, for a highly supercritical component (e.g., H2 or N2 at room temperature) the concept of a hypothetical liquid is of little use since the extrapolation of pure-liquid properties in this case is so excessive as to lose physical significance.  [c.18]

Guffey and Wehe (1972) used excess Gibbs energy equations proposed by Renon (1968a, 1968b) and Blac)c (1959) to calculate multicomponent LLE. They concluded that prediction of ternary data from binary data is not reliable, but that quarternary LLE can be predicted from accurate ternary representations. Here, we carry these results a step further we outline a systematic procedure for determining binary parameters which are suitable for multicomponent LLE.  [c.73]

Renon, H., Asselineav, L., Cohen, G., Raimbault, C. "Cacul sur Ordinateur des Equilibres Liquide-Vapeur et Liquide-Liquide," Editions Technip, Paris (1971).  [c.129]

Tharmalingam, S., Assessing Runaway Reactions and Sizing Vents, Chem. Eng., No. 463, Aug. 33, 1989.  [c.272]

Cardillo, P., and Girelli, A., The Seveso Runaway Reaction A Thermoanalytical Study, IChemE Symp. Series No. 68, 3/N 1, 1981.  [c.272]

Figure 10.1 Products of combustion contribute in vanous ways to the greenhouse effect, acid rain, and smog. (From Smith and Petela, Chem. Eng., 523 32, 1992 reproduced by permission of the Institution of Chemical Engineers.) Figure 10.1 Products of combustion contribute in vanous ways to the greenhouse effect, acid rain, and smog. (From Smith and Petela, Chem. Eng., 523 32, 1992 reproduced by permission of the Institution of Chemical Engineers.)
The waste streams created by utility systems tend, on the whole, to be less environmentally harmful than process waste. Unfortunately, complacency would be njisplaced. Even though utility waste tends to be less harmful than process waste, the quantities of utility waste tend to be larger than those of process waste. This sheer volume can result in a greater environmental impact than process waste. Gaseous combustion products contribute in various ways to the greenhouse effect, acid rain, and can produce a direct health hazard due to the formation of smog (see Fig. 10.1). The aqueous waste generated by utility systems also can be a major problem if it is contaminated.  [c.291]

Carbon suboxide, C3O2, OCCCO. M.p. — 107 C, b.p. 6-8°C. A toxic gas (malonic acid plus P2O5) which polymerizes at room temperature. Reforms malonic acid with water.  [c.82]

See pages that mention the term Rhenium : [c.11]    [c.80]    [c.109]    [c.228]    [c.228]    [c.254]    [c.275]    [c.396]    [c.15]    [c.24]    [c.25]    [c.27]    [c.30]    [c.46]    [c.75]    [c.84]    [c.87]    [c.87]    [c.109]    [c.118]   
See chapters in:

Encyclopedia of chemical technology volume 11  -> Rhenium

Chemistry of the elements (1998) -- [ c.0 ]