The method proposed in this monograph has a firm thermodynamic basis. For vapo/-liquid equilibria, the method may be used at low or moderate pressures commonly encountered in separation operations since vapor-phase nonidealities are taken into account. For liquid-liquid equilibria the effect of pressure is usually not important unless the pressure is very large or unless conditions are near the vapor-liquid critical region.  [c.2]

In the first, both components strongly associate with themselves and with each other. In the second, only one of the components associates strongly. For both systems, representation of the data is very good. However, the interesting quality of these systems is that whereas the fugacity coefficients are significantly remote from unity, the activity coefficients show only minor deviations from ideal-solution behavior. Figures 6 and 7 in Chapter 3 indicate that the fugacity coefficients show marked departure from ideality. In these systems, the major contribution to nonideality occurs in the vapor phase. Failure to take into account these strong vapor-phase nonidealities would result in erroneous activity-coefficient parameters, a 2 21  [c.51]

The method used here is based on a general application of the maximum-likelihood principle. A rigorous discussion is given by Bard (1974) on nonlinear-parameter estimation based on the maximum-likelihood principle. The most important feature of this method is that it attempts properly to account for all measurement errors. A discussion of the background of this method and details of its implementation are given by Anderson et al. (1978).  [c.97]



In describing reactor performance, selectivity is usually a more meaningful parameter than reactor yield. Reactor yield is based on the reactant fed to the reactor rather than on that which is consumed. Clearly, part of the reactant fed might be material that has been recycled rather than fresh feed. Because of this, reactor yield takes no account of the ability to separate and recycle unconverted raw materials. Reactor yield is only a meaningful parameter when it is not possible for one reason or another to recycle unconverted raw material to the reactor inlet. By constrast, the yield of the overall process is an extremely important parameter when describing the performance of the overall plant, as will be discussed later.  [c.25]

For batch reactors, account has to be taken of the time required to achieve a given conversion. Batch cycle time is addressed later.  [c.26]

The choice of reactor temperature, pressure, arid hence phase must, in the first instance, take account of the desired equilibrium and selectivity effects. If there is still freedom to choose between gas and liquid phase, operation in the liquid phase is preferred.  [c.46]

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]

This technique is useful not only when the mixture is impossible to separate by conventional distillation because of an azeotrope but also when the mixture is difficult to separate because of a particularly low relative volatility. Such distillation operations in which an extraneous mass-separating agent is used can be divided into two broad classes.  [c.81]

In the first class, azeotropic distillation, the extraneous mass-separating agent is relatively volatile and is known as an entrainer. This entrainer forms either a low-boiling binary azeotrope with one of the keys or, more often, a ternary azeotrope containing both keys. The latter kind of operation is feasible only if condensation of the overhead vapor results in two liquid phases, one of which contains the bulk of one of the key components and the other contains the bulk of the entrainer. A t3q)ical scheme is shown in Fig. 3.10. The mixture (A -I- B) is fed to the column, and relatively pure A is taken from the column bottoms. A ternary azeotrope distilled overhead is condensed and separated into two liquid layers in the decanter. One layer contains a mixture of A -I- entrainer which is returned as reflux. The other layer contains relatively pure B. If the B layer contains a significant amount of entrainer, then this layer may need to be fed to an additional column to separate and recycle the entrainer and produce pure B.  [c.81]

The second class of distillation operation using an extraneous mass-separating agent is extractive distillation. Here, the extraneous mass-separating agent is relatively involatile and is known as a solvent. This operation is quite different from azeotropic distillation in that the solvent is withdrawn from the column bottoms and does not form an azeotrope with any of the components. A typical extractive distillation process is shown in Fig. 3.11.  [c.82]

As with azeotropic distillation, the separation is possible in extractive distillation because the extraneous mass-separating agent interacts more strongly with one of the components than the other. This in turn alters in a favorable way the relative volatility between the key components.  [c.82]

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.  [c.82]

When separating azeotropic mixtures, if possible, changes in the azeotropic composition with pressure should be exploited rather than using an extraneous mass-separating agent. When using an extraneous mass-separating agent, there are inevitably losses from the process. Even if these losses are not significant in terms of the cost of the material, they create environmental problems somewhere later in the design. As discussed in detail in Chap. 10, the best way to solve effluent problems is to deal with them at the source. The best way to solve the effluent problems caused by loss of the extraneous mass-separating agent is to eliminate it from the design. However, clearly in many instances practical difficulties and excessive cost might force its use. Occasionally, a component that already exists in the process can be used as the entrainer or solvent, thus avoiding the introduction of extraneous materials for azeotropic and extractive distillation.  [c.83]

If an azeotropic mixture is to be separated by distillation, then use of pressure change to alter the azeotropic composition should be considered before use of an extraneous mass-separating agent. Avoiding the use of extraneous materials often can prevent environmental problems later in the design.  [c.92]

Although the flowsheet shown in Fig. 4.7a is very attractive, it is not practical. This would require careful control of the stoichiometric ratio of decane to chlorine, taking into account both the requirements of the primary and byproduct reactions. Even if it was possible to balance out the  [c.102]

Reactor pressure. In Chap. 2 it was deduced that vapor-phase reactions involving a decrease in the number of moles should be set to as high a pressure as practicable, taking into account that the high pressure might be expensive to obtain through compressor power, mechanical construction might be expensive, and high pressure brings safety problems (see Fig. 2.9d). Reactions involving an increase in the number of moles ideally should have a pressure that is continuously decreasing as conversion increases (see Fig. 2.9d). Reduction in pressure can be brought about either by a reduction in the absolute pressure or by the introduction of an inert diluent.  [c.277]

Assessing only the local efiects of combined heat and power is misleading. Combined heat and power generation increases the local utility emissions because, besides the fuel burnt to supply the heating demand, additional fuel must be burnt to generate the power. It is only when the emissions are viewed on a global basis, and the emissions from central power generation included, that the true picture is obtained. Once these are included, on-site combined heat and power generation can make major reductions in global utility waste. The reason for this is that even the most modem central power stations have a poor efficiency of power generation compared with a combined heat and power generation system. Once the other inefficiencies associated with centralized power generation are taken into account, such as distribution losses, the gap between the efficiency of combined heat and power systems and centralized power generation widens.  [c.292]

Knowing where waste is going is the key to reducing it. When reducing waste from process operations, a steady-state mass balance is not usually comprehensive enough. A balance that takes into account start-up, shutdown, and product changeovers is required.  [c.296]

If steam is used as stripping agent, either live steam or a reboiler can be used. The use of live steam increases the effluent volume. The volatile organics are taken overhead, condensed, and recycled to the process, if possible. If recycling is not possible, then further treatment or disposal is necessary.  [c.313]

If air is used as stripping agent, further treatment of the stripped material will be necessary. The gas might be fed to an incinerator or some attempt made to recover material by use of adsorption.  [c.313]

When synthesizing a flowsheet, these criteria are applied at various stages when there is an incomplete picture. Hence it is usually not possible to account for all the fixed and variable costs listed above. Also, there is little point in calculating taxes until a complete picture of operating costs and cash flows has been established.  [c.407]

Mordant acid dyes combine simultaneously with the mordanting agent (generally Cr(OH)j) and the fibre the dyestuff generally contains ortho OH -azo or OH-OH groups.  [c.13]

It thus appears that the flow rate of the nonkey components may account for the diflerences between sequences. Essentially, nonkey components have two effects on a separation. They cause  [c.145]

Equation (7.21) uses a single cost function in conjunction with the targets for the number of units (or shells) and network area. Differences in cost can be accounted for either by introducing new cost functions or by adjusting the heat exchange area to reflect the cost differences. This can be done by weighting the stream heat transfer coefficients in the calculation of network area with a factor [c.229]

Although the plus/minus principle is the ultimate reference in guiding process changes to reduce utility costs, it takes no accoimt of capital costs. Process changes to reduce utility consumption normally will bring about a reduction in temperature driving forces, as indicated in Fig. 12.1. Thus the capital/energy tradeoff (and hence ATmin) should be readjusted after process changes.  [c.323]

Targets also can be set for total heat exchange area, number of units, and number of shells for 1-2 shell-and-tube heat exchangers. These can be combined to establish a targej for capital costs, taking into account mixed materials of construction, pressure rating, and equipment type. Furthermore, the targets for energy and capital cost can be optimized to produce an optimal setting for the capital/energy tradeoff" before any network design is carried out.  [c.401]

Time is taken into account by discounting the annual cash flow Acf with the rate of interest to obtain the anitual discounted cash flow -Adcf- Thus, at the end of year 1,  [c.423]

New York San Francisco Washington, O.C. Auckiand BogoU Caracas Lisbon London Madrid Mexico City Milan Montreal New Delhi San Juan Singapore Sydney Tokyo Toronto  [c.463]

Andrews deration An important titration for the estimation of reducing agents. The reducing agent is dissolved In concentrated hydrochloric acid and titrated with potassium iodale(V) solution. A drop of carbon tetrachloride is added to the solution and the end point is indicated by the disappearance of the iodine colour from this layer. The reducing agent is oxidized and the iodate reduced to ICl, i.e. a 4-eiectron change.  [c.34]

Antimonypentafluoride, SbFj, m.p. 7 C, b.p. 150 C is an associated liquid (Sb plus F2 or SbClj plus HF). Forms many complexes and complex ions including [ShF ]", [Sb2Fu]" and is a very powerful fluoride ion acceptor. Greatly enhances the dissociation of, e.g. HF and HSO3F by forming anionic species (magic acid, super acid). Used as a fluorinating agent (sometimes in the form of its graphite intercalation compound).  [c.39]

Arsenic lII) oxide, AS2O3 (white arsenic). Formed by burning As in air, contains AS4O6 molecules or AsOa units joined by oxygen bridges. AS2O3 is used in glass manufacture and as arsenates(III) in insecticides, weedkillers and defoliants. It is used as a standard reducing agent (with I2 solution). It gives arsenates(III) with alkalis.  [c.42]

See pages that mention the term Azosemide : [c.31]    [c.134]    [c.241]    [c.13]    [c.313]    [c.12]    [c.24]    [c.25]    [c.28]    [c.29]    [c.30]    [c.31]    [c.39]    [c.39]    [c.41]    [c.42]    [c.42]   
See chapters in:

Pharmaceutical manufacturing encyclopedia Edition 2  -> Azosemide