In general

Unfortunately, the ideal-gas assumption can sometimes lead to serious error. While errors in the Lewis rule are often less, that rule has inherent in it the problem of evaluating the fugacity of a fictitious substance since at least one of the condensable components cannot, in general, exist as pure vapor at the temperature and pressure of the mixture. 

Appendix C presents the best set of constants for Equation (2). Also shown are the temperature limits of the real experimental data. Users must exercise caution when using the correlation outside the range of real data such use should, in general, be avoided. 

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. 

Increasing the pressure of irreversible vapor-phase reactions increases the rate of reaction and hence decreases reactor volume both by decreasing the residence time required for a given reactor conversion and increasing the vapor density. In general, pressure has little effect on the rate of liquid-phase reactions. 

Clearly, in the liquid phase much higher concentrations of Cfeed (kmol m ) can be maintained than in the gas phase. This makes liquid-phase reactions in general more rapid and hence leads to smaller reactor volumes for liquid-phase reactors. 

In general, heterogeneous catalysts are preferred to homogeneous catalysts because the separation and recycling of homogeneous catalysts often can be very difficult. Loss of homogeneous catalyst not only creates a direct expense through loss of material but also creates an environmental problem. 

In principle, extractive distillation is more useful than azeotropic distillation because the process does not depend on the accident of azeotrope formation, and thus a greater choice of mass-separating agent is, in principle, possible. In general, the solvent should have a chemical structure similar to that of the less volatile of the two components. It will then tend to form a near-ideal mixture with the less volatile component and a nonideal mixture with the more volatile component. This has the effect of increasing the volatility of the more volatile component. 

In general terms, there are two sources of yield loss in the process ... 

In general, the flow of key components is constant and independent of the sequence, while the flow of nonkey components varies according to the choice of sequence, as illustrated in Fig. 5.8. 

In general, the final network design should be achieved in the minimum number of units to keep down the capital cost (although this is not the only consideration to keep down the capital cost). To minimize the number of imits in Eq. (7.1), L should be zero and C should be a maximum. Assuming L to be zero in the final design is a reasonable assumption. However, what should be assumed about C Consider the network in Fig. 7.16, which has two components. For there to be two components, the heat duties for streams A and B must exactly balance the duties for streams E and F. Also, the heat duties for streams C and D must exactly balance the duties for streams G and H. Such balemces are likely to be unusual and not easy to predict. The safest assumption for C thus appears to be that there will be one component only, i.e., C = 1. This leads to an important special case when the network has a single component and is loop-free. In this case, ... 

The hazard of an explosion should in general be minimized by avoiding flammable gas-air mixtures in the process. Again, this can... 

Low pressure. Low pressures are not in general as hazardous as the other extreme operating conditions. However, one particular hazard that does exist in low-pressure plants handling flammable materials is the possible ingress of air with the consequent formation of a flammable mixture. 

In general, the best way to deal with a feed impurity is to purify the feed before it enters the process. Let us return to the isopropyl alcohol process from Fig. 10.3. Propylene is fed to the process containing propane as a feed impurity. In Fig. 10.3 the propane is removed from the process using a purge. This causes waste of... 

Process waste minimization in general terms is a question of... 

The utility system also creates waste through products of combustion from boilers and furnaces and wastewater from water treatment, boiler blowdown, etc. Utility waste minimization is in general terms a question of ... 

The dominant heating and cooling duties associated with a distillation column are the reboiler and condenser duties. In general, however, there will be other duties associated with heating and cooling of feed and product streams. These sensible heat duties usually will be small in comparison with the latent heat changes in reboilers and condensers. 

The cost of off-sites ranges typically from 20 to 40 percent of the total installed cost of the plant. In general terms, the larger the plant, the larger will be the fraction of the total project cost which goes to off-sites. In other words, a small project will require typically 20 percent of the total installed cost as off-sites. For a large project, the figure will be typically up to 40 percent. 

Batteries of fuel cells have been used in spacecraft but, in general, the potentially high efficiency of the fuel cell has not been realized industrially. 

Michaelis constant An experimentally determined parameter inversely indicative of the affinity of an enzyme for its substrate. For a constant enzyme concentration, the Michaelis constant is that substrate concentration at which the rate of reaction is half its maximum rate. In general, the Michaelis constant is equivalent to the dissociation constant of the enzyme-substrate complex. 

In general, condensation takes place at the a-carbon atom, leading to simple cinnamic acids or to their a-substituted derivatives. When possible, the anhydride corresponding to the sodium sail should be the condensing agent. 

The swelling of gels is markedly affected by the presence of electrolytes, this effect being a minimum at the isoelectric point of the material. In general, sulphates, tartrates, etc. inhibit swelling, while iodides and thiocyanates promote the swelling. Thus gelatine disperses completely in iodide solution even at low temperatures. 

The hydrocarbons are in general only slightly soluble in water. The solubility depends especially on the chemical nature of the hydrocarbons. 

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