Gases environment effects

A = effective surface area for heat and mass transfer in m L = latent heat of vaporization at in kj/kg k = mass-transfer coefficient in kg/ (sm kPa) t = mean source temperature for all components of heat transfer in K t = Hquid surface temperature in K p = Hquid vapor pressure at in kPa p = partial pressure of vapor in the gas environment in kPa. It is often useful to express this relationship in terms of dry basis moisture change. For vaporization from a layer of material ... 

On the other hand, when evolved vapor is purged from the dryer environment by using a second (inert) gas, the temperature at which vaporization occurs will depend on the concentration of vapor in the surrounding gas. In effect, the liquid must be heated to a temperature at which its vapor pressure equ s or exceeds the partial pressure of vapor in the purge gas. In the reverse situation, condensation will occur. 

One of the advanced concepts for capturing CO2 is an absorption process that utilizes dry regenerable sorbents. Pure sodium bicarbonate from Dongyang Chemical Company and spray-dried sorbents were used to examine the characteristics of CO2 reaction in a flue gas environment. The chemical characteristics were investigated in a fast fluidized reactor of 0.025 m i.d., and the effects of several variables on sorbent activity, including gas velocity (1.5 to 3.5 m/s), temperature (40 to 70 °C), and solid concentration (15 to 25 kg/m /s)], were examined in a fast fluidized-bed. Spray-dried Sorb NX30 showed fast kinetics in the fluidized reactor. 

Because carbon has a natural affinity for adsorption of heavy hydrocarbon species and polar molecules, CMS membranes need to be used at a sufficiently high temperature to eliminate contribution/interference of the adsorption. In contrast, strong adsorption of heavier molecules may be used to separate those species by adsorption as discussed earlier by the SSF mechanism (Rao and Sircar, 1993b). The SSF carbon membranes typically have pore dimensions much greater than those needed for CMS membranes since the separation is based on the adsorbed species effectively blocking permeation of other components (Fuertes, 2000). Carbon membranes are resistant to contaminants such as H2S and are thermally stable and can be used at higher temperatures compared to the polymeric membranes. For the synthesis gas environment, the hydrothermal stability of carbon in the presence of steam will be a concern limiting its operation temperature. 

Finally, also in the laboratory the study of the interaction of cavities inside a uniform fermionic background is of importance (Bulgac and Wirzba., 2001). Examples are C6o buckyballs immersed in liquid mercury. The liquid metal itself serves only as free-moving shapeable neutral background which provides the Fermi gas environment by its conductance electrons, in which the buckyballs drill the voids. Another example would be buckyballs in liquid 3He as Fermi gas. Finally, in the future, boson condensate cavities immersed in dilute atomic Fermi condensates could serve as further system with which the effective interactions of cavities inside a Fermi gas can be studied in the lab. 

The main applications derive from the family s gas barrier effects and chemical resistance to fuels in a dry state. High moisture absorption in wet environments is harmful to the impermeability and protective layers of polyethylene or another thermoplastic insensitive to water are often needed. 

In situ ETEM permits direct probing of particle sintering mechanisms and the effect of gas environments on supported metal-particle catalysts under reaction conditions. Here we present some examples of metals supported on non-wetting or irreducible ceramic supports, such as alumina and silica. The experiments are important in understanding metal-support interactions on irreducibe ceramics. 

Interesting line narrowing has been observed of quadrupole-induced lines of hydrogen-rare gas mixtures. These have been explained by van Kranendonk and associates [428] in terms of the mutual diffusion coefficient of H2 in a rare-gas environment, as an effective lengthening of the interaction times of H2-atom complexes. 

Certain of the gases and particulates released to the atmosphere by the burning of fossil fuels can accumulate there. Carbon dioxide is the classic example of such a gas. Its effect on the temperature of Earth s surface environment and consequent climatic change have been known for nearly a century (Arrhenius, 1896 Chamberlain, 1898). 

The MPE study of the dielectric environment effects on the spin-spin coupling constants of acetylene [43] allowed for a comparison with experimentally measured gas-to-solution shifts for a series of solvents of varying polarity. It has been found in the experimental study that 1JCC changes considerably with the solvent, and that the changes correlate approximately with the solvent polarity. This tendency has been qualitatively reproduced by the MPE MCSCF linear response calculation, although the calculated changes constitute only approximately 30 % of the experimental shifts. 

In gas-phase for Models A and B, the free energy barriers for this step is 29 and 33 kcal/mol respectively (Table 2) which is well above the general kinetic requirements of an enzymatic catalytic process (15-20 kcaFmol). But in the presence of water and protein environment effects (Model B), the free energy barrier for this step is 19 kcal/mol (Table 2), which is kinetically plausible (Fig. 4). As discussed earlier, the Ca coordinating with only three atoms of PQQ as opposed to seven-coordination from the x-ray... 

The original motivation for studying the thermal properties of cellulosic chars came from our study on bulk cellulose pyrolysis under conditions simulating those existing in a fire. In such a situation, the flame over the surface of the solid supplies heat to the pyrolyzing solid. In our work, the radiative and conductive feedback of heat from the flame to the surface was simulated using radiant heaters. The experiments were carried out in an inert gas environment, to maintain as well-defined a heat transfer environment as possible, free from complications due to actual combustion heat sources. A convective How of the inert gas was used to sweep away volatiles from the vicinity of the surface, and the heat transfer effects of the sweep gas were also taken into account. 

Because the glow-discharge creates a cloud of sputtered atoms in a low-pressure, rare-gas environment that is an excellent quenching medium, it is an effective source for atomic fluorescence. In addition, the inert gas acting as diluent poses few chemical interferences and the elemental absorption lines are relatively narrow. It should be noted that GD-AF has not been used to the same extent as other GD techniques, however. 

A very important aspect of gas sensors in automotive exhaust-gas environments is aftertreatment of the electrodes to control a specific sensor behavior. For example, to measure nonequilibrium raw emissions, the sensor needs excellent catalytic ability. Various methods are known to improve electrodes in Zr02-based sensors. One well known method is to increase the active platinum surface area and the three-phase boundary area by partial reduction of zirconia close to the electrode. This occurs when the ceramic is exposed to a reducing atmosphere at high temperatures or when an electrical cathodic current is applied through the electrode and electrolyte. A similar effect can be achieved by chemical etching of the elec-... 

Burnham, A K. Subblefield, C. T Campbell, J. H. Effects of Gas Environment on Mineral Reactions in Colorado Oil Shale Report UCRL-81951, Lawrence Livermore National Laboratory Livermore, CA, 1978. 

The decomposition of dilute mixtures of NH3 in a PBMR using Pd-alloy membranes was studied by Collins and Way [2.322], and by Gobina et aL [2.323]. This application is of potential interest in the treatment of coal gasification streams, and the laboratory results showed promise. It would be interesting to see, whether the same membranes prove robust in the real coal-gas environment. The use of a PBMR to study the hydrodechlorination of dichloroethane was reported by Chang et al. [2.324]. The reported potential advantage of the membrane would be in preferentially removing the by-product HCl, which deactivates the catalyst. The authors attribute the observed improved performance, however, to a dilution effect. 

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