Mobility gas

By far the most used detector is the thermal conductivity detector (TCD). Detectors like the TCD are called bulk-property detectors, in that the response is to a property of the overall material flowing through the detector, in this case the thermal conductivity of the stream, which includes the carrier gas (mobile phase) and any material that may be traveling with it. The principle behind a TCD is that a hot body loses heat at a rate that depends on the... 

Conditioning Equilibrating a column with a flow of carrier gas (mobile phase) at the maximum expected operating temperature of the column. 

Figure 1.1 The nature of a composite, Pt/C/recast ionomer layer with a structure that enables high electronic and gas mobilities as well as sufficient proton mobility [Gasteiger, 2005].

The reason for wide-spread interest in the use of surfactants as gas mobility control agents (369) is their effectiveness at concentrations of 0.1%wt (377) or less (364). This low chemical requirement can significantly improve process economics. 

In addition to the mobility control characteristics of the surfactants, critical issues in gas mobility control processes are surfactant salinity tolerance, hydrolytic stability under reservoir conditions, and surfactant propagation. Lignosulfonate has been reported to increase foam stability and function as a sacrificial adsorption agent (392). The addition of sodium carbonate or sodium bicarbonate to the surfactant solution reduces surfactant adsorption by increasing the aqueous phase pH (393). 

It follows from Equation 8.13 that aA/B can be expressed as the product of the diffusivity selectivity, DA/DB, and the solubility selectivity, SA/SB. Diffusion (or mobility) selectivity is governed primarily by the size difference between gas molecules and always favors smaller gas molecules. Solubility selectivity is controlled by the relative condensability of the gases in the polymer and their relative affinity for the polymer. Solubility selectivity typically favors larger, more condensable molecules. From Equation 8.13, it is seen that the product of gas mobility and solubility selectivity determines the overall membrane selectivity. It is clear that for a membrane to be C02 selective, it must have high diffusivity selectivity based on the affinity for C02 but it should be flexible enough to permeate larger molecules such... 

Gas mixture, hydrogen content of, 13 790 Gas mobility control processes, issues in, 16 626... 

Figure 14.3 shows a typical capillary gas chromatograph with the major components labeled. This gas chromatograph set up includes compressed gas tanks for the carrier gas (mobile phase) and any necessary detector gases, an auto-injector that employs a micro-syringe for delivering the necessary small sample volumes and an inlet capable of the... 

Differential detector. A detector that responds to the instantaneous difference in composition between the column effluent and the carrier gas (mobile phase). 

Eluent. The gas (mobile phase) used to effect a separation by elution. 

Linear flowrate. F(v). The volumetric flowrate of the carrier gas (mobile phase) divided by the area of the cross section of the column. It is expressed as cm3cm 2/min or cm/min. 

Retention volume. VR. The product of the retention time of a sample component and the volumetric flowrate of the carrier gas (mobile phase). IUPAC recommends it be called the Total Retention Volume because it is a term used when the sample is injected into a flowing stream of the mobile phase. Thus, it includes any volume contributed by the sample injector and the detector. 

Involves a sample being vaporized and injected into the head space of the chromatographic column. The sample is transported through the column by the flow of an inert gas (mobile phase). The column itself contains a liquid stationary phase which is adsorbed onto the surface of an inert solid. Retention time with detection techniques (spectrophotometer, mass spectrometry, fluorescence) identifies the compound. 

This method is based on the fact that molecular association may lead to an efficient chiral recognition leading to enantiomeric separation when a chiral stationary phase (e.g. cyclodextrins) is used in GC. The gas (mobile phase, e.g. hydrogen, helium, nitrogen) is carrying the chiral analyte through the stationary phase. The enantiomers to be analyzed... 

Strong ability of the foam to reduce gas mobility in porous media... 

The sample is carried through the column (3) by the carrier gas/mobile phase. The column is enclosed in a thermostatically controlled oven (4). Depending on how firmly each component of the sample sticks to the stationary phase - i.e. its affinity for the stationary phase - the mobile phase carries it through the column more or less quickly. Components that stick least tightly to the stationary phase move fastest, while those that are held more firmly move through more slowly. The time taken for a component of a mixture to pass through the column is known as its retention time. The retention time of a substance depends on how its vapour is distributed between the mobile and stationary phases. 

Gas mobility depends on the permeability of the porous medium. In the presence of foam gas mobility is the mobility of the continuous gas phase through the free channels and the mobility of the confined gas along with the liquid. Formally the relative permeability of each phase (liquid or gas) can be expressed by Darcy s equation. 

Gas mobility in the presence of a foam is dominated by foam texture (bubble size) [171]. The strong fall in permeability in the presence of a foam is a result of foam trapping established not only in the macroscopic studies but by the direct observations of transparent micromodels [153,158] as well. Foam trapping is a batch process the immobile foam can become mobile with time and vice versa [158]. 

Fig. 10.18. Effect of gas fractional flow on relative gas mobility (A) porous medium - 0.6 cm glass beads L = 60 cm permeability - 270 pm2 porosity - 0.36 surfactant - 1% Siponate DS-10.

Here J denotes the Leverett J function, and is the porosity.) Khatib and co-workers used Equation 9 in their demonstration of the dependence of coalescence and gas mobility on the limiting capillary number (41). 

A study of the effect of pore geometry on foam formation mechanisms shows that snap-off" bubble formation is dominant in highly heterogeneous pore systems. The morphology of the foams formed by the two mechanisms are quite different. A comparison of two foam injection schemes, simultaneous gas/surfactant solution injection (SI) and alternate gas/surfactant solution injection (GDS), shows that the SI scheme is more efficient at controlling gas mobility on a micro-scale during a foam flood. 

High gas mobility and low sweep efficiency are typical problems encountered in oil recovery processes using gas injection. 

Effect of Injection Scheme on Foam Displacement. If the main interest in using foam is for controlling gas mobility, then it is necessary to have a criterion to judge the effectiveness of a foam... 

The present paper has provided a basis on which foam flow in porous media can be analyzed and described. The gas mobility was found to be dictated by static capillary effects (mobilization pressure), dynamic capillary effects (dynamic effects altering bubble train... 

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