Phase Phenomena

4% C2H4, 12.2% H2,3.6% CH4, and 53.4% N2. The coal used analyzes 70.0% C, 6.5% H, 16.0% O, and 7.5% ash. The entering air for combustion has a partial pressure of water equal to 2.67 kPa. The barometer reads 101 kPa, Records show that 465 kg of steam is supplied to the combustion vessel per metric ton of coal fired. Calculate the dew point of the exit gas. 

A liquid solution of pharmaceutical niaterial to be dried is sprayed into a stream of hot gas. The water evaporated from the solution leaves with the exit gases. The solid is recovered by means of cyclone separators. Operating data are  

A gas leaves a solvent recovery system saturated with benzene at 50°C and 750 mm Hg. The gas analyzes, on a benzene-free basis, 15% CO, 4% O2, and the remainder nitrogen. This mixture is compressed to 3 atm and is subsequently cooled to 20°C. Calculate the percent benzene condensed in the process. What is the relative saturation of the final gas  

A large fermentation tank fitted with a 2-in. open vent was sterlized for 30 minutes by blowing in live steam at 35 psig. After the steam supply was shut off, a cold liquid substrate was quickly added to the tank at which point the tank collapsed inward. 

Write down the phase rule, define each parameter in the phase rule, and be able to apply the phase rule to determine the degrees of freedom, or the number of components, or the phases that exist in a system. 

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AC impedance spectroscopy is widely employed for the investigation of both solid- and liquid-phase phenomena. In particular, it has developed into a powerfiil tool m corrosion teclmology and in the study of porous electrodes for batteries [, and ]. Its usage has grown to include applications ranging from... 

The understanding of isotope effects on chemical equilibria, condensed phase equilibria, isotope separation, rates of reaction, and geochemical and meteorological phenomena, share a common foundation, which is the statistical thermodynamic treatment of isotopic differences on the properties of equilibrating species. For that reason the theory of isotope effects on equilibrium constants will be explored in considerable detail in this chapter. The results will carry over to later chapters which treat kinetic isotope effects, condensed phase phenomena, isotope separation, geochemical and biological fractionation, etc. 

The thermochemical conversion of biofuels takes place in the conversion system and belongs to the science of two-phase phenomena (fluid-solid dynamics), that is, heat and mass transport processes take place inside and between a solid phase and a gas phase. This phenomenology is well illustrated by Balakrishnen and Pei [49], see Figure 40. 

SO2 uptake was measured at total system pressures in the range of 20 to 50 Torr, consisting of 17.5 Torr H2O vapor with the balance either helium or argon. The observed mass accommodation coefficients, 74, are plotted in Figure 2 as a function of the inverse of the calculated diffusion coefficient of SO2 in each H20-He and l O-Ar mixture. The diffusion coefficients are calculated as a sum of the diffusion coefficients of SO in each component. The diffusion coefficients for SO in He and in Ar are estimated from the diffusion coefficient of SO2 in H 0 (Dg p = 0.124 (101) by multiplying this value by the quantity (mH-/mH Q)V2, anti (mAr/m 2o) 2> respectively. The curves in Figure 2 are plots ofEquation 7 with three assumed values for 7 0.08,0.11 and 0.14. The best fit to the experimental values of is provided by 7 = 0.11. Since gas uptake could be further limited by liquid phase phenomena as discussed in the following section, 7502 = 0.11 is a lower limit to the true mass accommodation coefficient for SO2 on water. 

S. Springston, P. David, et al., Stationary phase phenomena in capillary supercritical fluid chromatography, Anal. Chem., 55 997-1002 (1986). 

This type of model works well at high applied heat flux levels, where the pyrolysis front is thin. Simplicity is its advantage it is not necessary to specify any parameters related to the decomposition kinetics. A large body of flame spread modeling work has applied this type of model, but there is a tendency to focus with great detail on gas-phase phenomena (i.e., full Navier-Stokes, detailed radiation models, multistep combustion reactions) and treat the condensed-phase fuel generation process in an approximate manner. 

With IR light sources like this one, a technology is available which, in terms of day-to-day reliability and long-term and short-term stability, is entirely comparable with Ti sapphire regenerative amplifiers. As shown in this article, it was possible to perform femtosecond experiments on all kinds of condensed phase phenomena involving vibrational transitions (such as energy relaxation, dephasing, spectral diffusion, coupled systems) with essentially the same facility and accuracy as can be achieved in visible and near-infrared experiments. 

The decay of the CO stretch is a single exponential when W(CO)6 has substantial interactions with a solvent. A single exponential (aside from orientational relaxation in liquids) is observed even when very fast pulses are used in the experiments (81). In the gas phase, the transition frequency of the CO stretch evolves over a range of frequencies because of its time-dependent interaction with the low-frequency modes. When a buffer gas or solvent is added, collisions cause the coherent evolution of the slow modes to be interrupted frequently, possibly averaging away the perturbation responsible for the observed fast time dependence. Thus, the fastest and slowest components of the tri-exponential decay are inherently low-pressure, gas phase phenomena. 

We have presented experimental and theoretical results for vibrational relaxation of a solute, W(CO)6, in several different polyatomic supercritical solvents (ethane, carbon dioxide, and fluoroform), in argon, and in the collisionless gas phase. The gas phase dynamics reveal an intramolecular vibrational relaxation/redistribution lifetime of 1.28 0.1 ns, as well as the presence of faster (140 ps) and slower (>100 ns) components. The slower component is attributed to a heating-induced spectral shift of the CO stretch. The fast component results from the time evolution of the superposition state created by thermally populated low-frequency vibrational modes. The slow and fast components are strictly gas phase phenomena, and both disappear upon addition of sufficiently high pressures of argon. The vibrational... 

The thermodynamic cycle (Fig. 4.2) illustrates the problems we face in transferring our knowledge of gas phase intermolecular interactions to solution phase phenomena. 

Elutriation or dilute phase phenomena Reactions in freeboard or grid region Models... 

It is beyond the scope of this short review to list every available molecular mechanics program. Only a selected few programs are mentioned here, without descriptive details of the potential functions, minimization algorithms, or comparative evaluations. Both the CHARMM and AMBER force fields use harmonic potential functions to calculate protein structures. They were developed in the laboratories of Karplus and Kollman, respectively, and work remarkably well. The CFF and force fields use more complex potential functions. Both force fields were developed in commercial settings and based extensively or exclusively on results obtained from quantum mechanics. Unlike the other molecular mechanics methods, the OPLS force field was parameterized by Jorgensen to simulate solution phase phenomena. 

In this section we discuss two categories of phase phenomena for ... 

We are now going to consider how phase phenomena can be illustrated by means of diagrams. 

Presentation of phase phenomena for mixtures that are completely miscible in the liquid state involves some rather complex reductions of three-, four-, and higher-dimensional diagrams into two dimensions. We shall restrict ourselves to two-component systems because, although the ideas discussed here are applicable to any number of components, the graphical presentation of more complex systems in an elementary text such as this is probably more confusing than helpful. 

Another way to illustrate the phase phenomena for the two-component systems we have been discussing is to use pressure-composition diagrams at constant temperature or, alternatively, to use temperature-composition diagrams at constant pressure. A temperature-composition diagram with pressure as the third parameter is illustrated in Fig. 3.24 for the ethane-heptane system. 

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