GAS DESORPTION

The purity of gases used should also be specified, as certain impurities can have a decisive effect on storage behavior, e. g. gas desorption from stoppers. Greiff and Rightsel [1.96] have shown that influenza viruses without CPAs keep their infectivity best when stored with 1.6 % RM in helium. In argon, the infectivity decreases approx. 10 times and in 02 20 times faster if the average of the storage temperatures is used. 

The leak rates of a freeze drying plant can be measured at the empty plant with the condenser cooled and the shelves heated by measuring the pressure rise per time multiplied by the installation volume in the dimension (mbar L/s). It should be noted, that the plant has to be evacuated for several hours, e. g. down to 10-2 mbar, before the pressure rise measurements, to avoid the influence of small amounts of ice and the desorption of gas from the surfaces. Furthermore, the pressure rise should be measured up to 0.2 or 0.4 mbar to detect possible gas desorption. Only if the pressure rise has been for some time proportional with time (Fig. 2.33.1), it represents a leak rate, which is defined as... 

While for macroporous structures the inner surface can be calculated from the geometry, meso and micro PS layers require other methods of measurement First evidence that some PS structures do approach the microporous size regime was provided by gas absorption techniques (Brunauer-Emmet-Teller gas desorption method, BET). Nitrogen desorption isotherms showed the smallest pore diameters and the largest internal surface to be present in PS grown on low doped p-type substrates. Depending on formation conditions, pore diameters close to, or in, the microporous regime are reported, while the internal surface was found to... 

In studies of trichloroethylene (TCE) vapor sorption to various porous particles at 100% relative humidity, it was reported that the slow fraction remaining after N2 gas desorption was highly concentration dependent and not well simulated by considering only equilibrium nonlinearity. 

Now, we consider gas-liquid mass transfer rates in gas absorption and its reverse operation - that is, gas desorption in packed columns. The gas entering the column from the bottom and the liquid entering from the top exchange solute while contacting each other. In case of absorption, the amount of solute transferred from the gas to the liquid per unit sectional area of the column is... 

Diels, K., and R. Jueckel (H. Adam and I. Edwards, trans.), 1966, Leybold Vacuum Handbook, Pergamon, New York. This is an English translation of the second German edition. It contains information on the gas desorption and mechanical properties of plastics and elastomers. 

The most prominent feature of the spectra in Fig. 11.3 is a dramatic difference between the compositions of the gas phase below and above 400°C. The concentration of the D2 molecules in the gas phase increased as the temperature was increased from 100°C to 400°C. In the spectra measured after heating to 500°C and 550°C, the peaks with m/z = 4 and 3 became dominant. Consequently, D2 and HD molecules were the main components of the gas phase at these temperatures. This remarkable fact shows that the main step in the manometric curves in Fig. 11.2 is actually due to evolution of molecular hydrogen whereas light hydrocarbon molecules contribute mainly at lower temperatures when the gas desorption is small. 

In addition to thermal desorption, gas desorption has been found to result from electron, ion and photon bombardment of surfaces. Therefore, simultaneous particle and photon bombardments can be expected to alter desorption rates, as well as the nature and charge distribution of the desorbed species. Furthermore, simultaneous bombardment of a surface by neutrons and ions could affect diffusion processes, e.g., by radiation-induced segregation. In turn, desorption processes can be influenced by altering the diffusion of species from the bulk to the surface. The type, energy, and angular distribution of particles expected to strike neutral beam injector dump areas (such areas can represent 1/9 of total first wall area) can cause synergistic effects on gas desorption which can be quite different from those expected from the interaction of plasma radiations with the first wall. 

The relative magnitudes of He and Kj (Table I) indicate that the removal of both PCP and TCP occurs mainly by adsorption on the air-water interface of the air bubbles while that of NAPH occurs mostly as the vapor phase inside the air bubbles. Since the volatile fraction carried inside the air bubbles is lost to the air at the top of the aqueous phase and the surface adsorbed phase is deposited at the top of the aqueous phase, bubble fractionation removal of NAPH involves simultaneous gas desorption (air stripping) and enrichment at the top. Bubble fractionation is an integral part of most operations conducted in bubble columns. 

Energy-separating agent heat input into the amine solution to accelerate the rate of gas desorption which regenerates the solution. 

Figure 3.4.12 C02 gas desorption isobar curve at ambient pressure (a), DSC curves at various C02 partial pressures (b), and the deduced crystal phase transition induced by incorporated C02 gas inside the crystal(c).

Source rock gas content This property essentially defines the quantity of gas remaining in the source rock at current conditions. It is estimated from gas desorption tests. Conversely, this measurement can also help estimate the gas expulsion efficiency. 

Further, combining equations (7) and (9) yields an equation to compute gas generated from the source rock in terms of the gas desorption parameters and expulsion efficiency as... 

Water steam sterilization at 121 °C for 20 min is a popular technique but polymers are always degraded and hydrophilic surfaces can swell. Irradiation of polymers with a y beam leads to C-C and C-O bond scissions and the formation of unstable radicals. After the recombination of these highly reactive species, oxidation and crosslinking are observed. Exposure of materials to ethylene oxide at 40-45 °C for about an hour leads to gas desorption lasting from several hours to several days. However, no chemical damage is observed. This technique is preferable for hydrophilic materials. 

Fo - coal gas desorption rate at start t = 0) desorption time, ml/min. 

ABSTRACT In order to investigate the effect of coal particle size on gas desorption and diffusion law at constant temperature, the constant temperature dynamic coal particle gas adsorption and desorption experiment with different particle sizes was conducted in the coal gas adsorption and desorption experiment system. The results suggest that gas desorption laws of different particle size of coal samples show a good consistency at different pressures, and the cumulative desorption of gas coal particle is linear with time. For the same particle, the higher the initial pressure, the more the maximum gas desorption the smaller the coal particle is, the more quickly the gas desorption rate is at the same initial pressure. Then, the gas spherical flow mathematical model is built based on Darcy law and is analysed with finite difference method. At last, the gas spherical flow mathematical model is constructed with Visual Basic. The contrast between numerical simulation and experimental results shows that the gas flow in the coal particle internal micropore accords with Darcy s law. 

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