Tanasescu


The thermodynamic treatment of multicomponent phase equilibria, introduced by J. W. Gibbs, is based on the concept of the chemical potential. Two phases are in thermodynamic equilibrium when the temperature of one phase is equal to that of the other and when the chemical potential of each component present is the same in both phases. For engineering purposes, the chemical potential is an awkward quantity, devoid of any immediate sense of physical reality. G. N. Lewis showed that a physically more meaningful quantity, equivalent to the chemical potential, could be obtained by a simple transformation the result of this transformation is a quantity called the fugacity, which has units of pressure. Physically, it is convenient to think of the fugacity as a thermodynamic pressure since, in a mixture of ideal gases, the fugacity of each component is equal to its partial pressure. In real mixtures, the fugacity can be considered as a partial pressure, corrected for nonideal behavior.  [c.14]

We might think that we can find all the structural options by inspection, at least all of the significant ones. The fact that even long-established processes are still being improved bears evidence to just how difficult this is.  [c.3]

Stirred-tank reactors. Stirred-tank reactors consist simply of an  [c.53]

Stirred-tank reactors can be operated in batch, semi-batch, or  [c.53]

In fact, it is often possible with stirred-tank reactors to come close to the idealized well-stirred model in practice, providing the fluid phase is not too viscous. Such reactors should be avoided for some types of parallel reaction systems (see Fig. 2.2) and for all systems in which byproduct formation is via series reactions.  [c.53]

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]

Heat can be added to or removed from stirred-tank reactors via  [c.53]

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]

Figure 3.3 shows a simple type of classifier. In this device, a large tank is subdivided into several sections. A size range of solid particles suspended in vapor or liquid enters the tank. The larger, faster-settling particles settle to the bottom close to the entrance, and the slower-settling particles settle to the bottom close to the exit. The vertical baffles in the tank allow the collection of several fractions.  [c.70]

Clearly, the time chart shown in Fig. 4.14 indicates that individual items of equipment have a poor utilization i.e., they are in use for only a small fraction of the batch cycle time. To improve the equipment utilization, overlap batches as shown in the time-event chart in Fig. 4.15. Here, more than one batch, at difierent processing stages, resides in the process at any given time. Clearly, it is not possible to recycle directly from the separators to the reactor, since the reactor is fed at a time different from that at which the separation is carried out. A storage tank is needed to hold the recycle material. This material is then used to provide part of the feed for the next batch. The final flowsheet for batch operation is shown in Fig. 4.16. Equipment utilization might be improved further by various methods which are considered in Chap. 8 when economic tradeoffs are discussed.  [c.121]

In preliminary process design, the primary consideration is contact by inhalation. This happens either through accidental release of toxic material to the atmosphere or the fugitive emissions caused by slow leakage from pipe flanges, valve glands, and pump and compressor seals. Tank filling causes emissions when the rise in liquid level causes vapor in the tank to be released to the atmosphere.  [c.259]

Vapor Treatment. The vapors from the tank space can be sent to a treatment system (condenser, absorption, etc.) before venting. The system shown in Fig. 9.1 uses a vacuum-pressure relief valve which allows air in from the atmosphere when the liquid level falls (Fig. 9.1a) but forces the vapor through a treatment system when the tank is filled (Fig. 9.16). If inert gas blanketing is required, because of the flammable nature of the material, then a similar system can be adopted which draws inert gas rather than air when the liquid level falls.  [c.260]

Flexible membrane. Another method to stop the vapor space breathing to atmosphere is to use a tank with a flexible membrane in the roof, Fig. 9.26.  [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]

It is interesting to compare what might have been the conclusion if the inventory was in a reactor and not in a storage tank. If it is assumed, as an order of magnitude, that the reaction rate doubles for every lO C rise in temperature, then the rate of reaction at IhO C would be 32 times faster than that at 100°C. For the same reactor conversion, this would mean that the inventory would be 32 times smaller. Thus operation at higher temperatures brings increased hazard as far as the fraction of released material that vaporizes is concerned but a lower hazard as far as the inventory required to give the same reactor conversion is concerned. Overall, operation of the reactor at higher temperature would be preferred against these measures. However, other factors would need to be taken into consideration in a detailed assessment.  [c.270]

Process operations. The third source of process waste we can classify under the general category of process operations. Operations such as start-up and shutdown of continuous processes, product changeover, equipment cleaning for maintenance, tank filling, etc. all produce waste.  [c.274]

When process tanks, road tankers, or rail tank cars are filled, material in the vapor space is forced out of the tank and lost to atmosphere.  [c.289]

Reduce losses from fugitive emissions and tank breathing as discussed under safety in Chap. 9.  [c.290]

Reducing losses from fugitive emissions and tank breathing.  [c.297]

Holding tank feed Cold 160 260 200  [c.334]

As stated previously, the source of capital is often not known, and hence it is not known whether or not Eq. (A. 10) is appropiiate to represent the cost of capital. Equation (A. 10) is, strictly speaking, only appropriate if the money for capital expenditure is to be borrowed over a fixed period at a fixed rate of interest. Moreover, if Eq. (A. 10) is accepted, then the number of years over which the capital is to be annualized is unknown, as is the rate of interest. However, the most important thing is that even if the source of capital is not known, etc., and uncertain assumptions are necessary, Eq. (A. 10) provides a common basis for the comparison of competing projects.  [c.421]

The CFR engine has a single cylinder designed to withstand continued knocking without damage. It operates at full throttle and at low rotating speed (600 or 900 rpm, according to one of two standard procedures described below). The variable compression ratio can be adjusted during operation by moving the cylinder vertically by means of a rack-and-pinion crank. There is also a mechanism to adjust the fuel-air ratio, consisting of varying the fuel level in the carburetor tank.  [c.195]

After a few hours of flight at high altitude, an aircraft s fuel tank will reach the same temperature as the outside air, that is, around -40 to -50°C. Under these conditions, it is important that the fuel remains sufficiently fluid to assure good flow to the jet engine. This property is expressed by the temperature at which crystals disappear or the Freezing Point (ASTM D 2386). It is the temperature at which the crystals formed during cooling disappear when the jet fuel is reheated. It should be around -50°C maximum for Jet Al, with a more and more frequent waiver to -47°C. Meeting such a cold service can be hindered by the presence of small quantities of water dissolved in the jet fuel.  [c.228]

King, 1971 Naphtali and Sandholm, 1971 Newman, 1963 and Tomich, 1970). Moreover the choice of appropriate computation procedures for distillation, absorption, and extraction is highly dependent on the system being separated, the conditions of separation, and the specifications to be satisfied (Friday and Smith, 1964 Seppala and Luus, 1972). The thermodynamic methods presented in Chapters 3, 4, and 5, particularly when combined to  [c.110]

The t3rpe of equipment illustrated in Fig. 4.12 is more t3rpical of batch operation than continuous operation even though continuous is being contemplated at the moment. For example, the evaporator is a stirred tank with a heating jacket. In continuous plsmt, a more elaborate design with tubular heating of some tjq>e probably would have been used.  [c.120]

Equation (5.8) tends to predict vapor loads slightly higher than those predicted by the full multicomponent form of the Underwood equation. The important thing, however, is not the absolute value but the relative values of the alternative sequences. Porter and Momoh have demonstrated that the rank order of total vapor load follows the rank order of total cost.  [c.137]

Consider again the simple process shown in Fig. 4.4d in which FEED is reacted to PRODUCT. If the process usbs a distillation column as separator, there is a tradeofi" between refiux ratio and the number of plates if the feed and products to the distillation column are fixed, as discussed in Chap. 3 (Fig. 3.7). This, of course, assumes that the reboiler and/or condenser are not heat integrated. If the reboiler and/or condenser are heat integrated, the, tradeoff is quite different from that shown in Fig. 3.7, but we shall return to this point later in Chap. 14. The important thing to note for now is that if the reboiler and condenser are using external utilities, then the tradeoff between reflux ratio and the number of plates does not affect other operations in the flowsheet. It is a local tradeoff.  [c.239]

Figure 9.1 Storage tank fitted with a vapor treatment system. (From Smith and Petela, The Chemical Engineer, no. 517, 9 April, 1992 reproduced by permission of the Institution of Chemical Engineers.) Figure 9.1 Storage tank fitted with a vapor treatment system. (From Smith and Petela, The Chemical Engineer, no. 517, 9 April, 1992 reproduced by permission of the Institution of Chemical Engineers.)
C, b.p. 290 C. Occurs in the Tonka bean, of which it is the odorous ingredient. Prepared synthetically by heating salicylaldehyde with elhanoic anhydride and sodium elhanoate. It  [c.113]

Table 4.16a Coeff exam dents for conver pie applied to a pt ting a TBP curve Hroleum cut (Riaz into an ASTM D 86 curve and an i s method). Table 4.16a Coeff exam dents for conver pie applied to a pt ting a TBP curve Hroleum cut (Riaz into an ASTM D 86 curve and an i s method).

See pages that mention the term Tanasescu : [c.129]    [c.53]    [c.54]    [c.54]    [c.261]    [c.261]    [c.289]    [c.315]    [c.316]    [c.29]    [c.146]    [c.234]    [c.323]    [c.332]    [c.384]    [c.384]    [c.395]    [c.408]    [c.427]   
Organic syntheses based on name reactions and unnamed reactions (1994) -- [ c.228 ]