Transfer gas

Fig. 2. Schematic representation for the two-film theory of gas transfer = partial pressure of gas Pj = partial pressure of the gas at the interface Cj = concentration of gas at time t, Cj = initial concentration of gas at the interface Cg = initial concentration of gas at t = 0 and S = gas saturation.

An unstabilized high surface area alumina siaters severely upon exposure to temperatures over 900°C. Sintering is a process by which the small internal pores ia the particles coalesce and lose large fractions of the total surface area. This process is to be avoided because it occludes some of the precious metal catalyst sites. The network of small pores and passages for gas transfer collapses and restricts free gas exchange iato and out of the activated catalyst layer resulting ia thermal deactivation of the catalyst. 

Figure 2 Variation of the gas transfer veloeity with wind speed. The units of transfer veloeity are equivalent to the number of em of the overlying air eolumn entering the water per hour (Taken from Bigg," with permission of Cambridge University Press)...

The small pore size and the uniform distribution result in capillary forces which should allow wicking heights and thus battery heights of up to 30 cm. Due to the cavities required for gas transfer and under the effect of gravity, the electrolyte forms a filling profile, i.e., fewer cavities remain at the bottom than at the top. Therefore with absorptive glass mats a rather flat battery... 

Since the early 1980s a chemical-equipment combination technique has been available utilizing hydrazine and a catalytic carbon filter bed, and since the early 1990s gas transfer membranes have entered the market and proved to be particularly effective. 

Oxygen Removal Using Gas Transfer Membrane (GTM)Technology... 

These gas transfer membranes or membrane contactors employ microporous polypropylene hollow fiber membranes arranged in a modular design. Oxygenated water flows on the shell side of the hollow fibers, and a strip gas (such as nitrogen) or a vacuum is applied to the inside (lumenside), with the hollow fibers acting as a support medium for intimate contact between the water and gas phases. 

The aqueous stream is at higher pressure than the strip gas (or vacuum) and fast diffusive transport of dissolved gases takes place. Gas transfer membrane technology is suitable for deaeration of boiler feed, building water, and other applications, and produces water with DO levels down to 1 ppb 02. 

Kinghorn, Patrick H. Haas, William E. (Ecolochem, Inc.). Low Level Deoxygenation of Boiler Makeup Water Using Gas Transfer Membranes. Pittsburgh International Water Conference, USA, 1999. 

The piston velocity, or gas transfer velocity, is a function of wind speed. There are large differences in the relationships between piston velocity and wind speed, especially at liigher wind speeds (e.g., Liss and Merlivat, 1986 Wannin-khof, 1992). This is the limiting factor for these calculations. 

Solution Ideally, the scaleup will maintain the same inlet concentrations for the two phases, the same relative flow rates and holdups for the two phases, and the same ratio of gas transferred to liquid throughput. It is also necessary to maintain a constant residence time in the liquid phase. It is simple to set the flow rates ... 

Lincoff, A. H., Gossett, J. M. (1984) The determination of Henry s law constants for volatile organics by equilibrium partitioning in closed systems. In Gas Transfer at Water Surfaces. Brutsaert, W., Jirka, G. H., Eds., pp. 17-26, D. Reidel Publishing Co., Dordrecht, The Netherlands. 

What is the value of the overall gas transfer coefficient KGal... 

Factors involved in heat transfer, such as surface-to-volume ratio, agitation characteristics, mixing efficiency, fouling of heat transfer surfaces, scale of operations, and the resulting heat exchanged depend on the system under consideration (e.g., liquid-liquid transfer, liquid-gas transfer, free convection, or forced convection). Standard chemical engineering texts and reference books contain detailed discussions on heat transfer in process equipment. Only a brief summary follows ... 

Heat, and sometimes gas, transfer from the core of a bulk material, also influences auto-ignition and explosion. The concept of critical mass is not limited to nuclear explosives (though shape is also important). Some entries in this text, such as sodium chlorate, ammonium nitrate and ammonium perchlorate, have proved extremely destructive dining industrial storage by the tens of tonnes, but are incapable of explosion at the ten gramme scale. Many other entries are for hazards significant only beyond laboratory scale [1]. 

The concept of a transfer unit for a countercurrent mass transfer process, introduced in Volume 1, is developed further for distillation in packed columns in Section 11.11. The number of transfer units is defined as the integrated value of the ratio of the change in composition to the driving force. Thus, considering the vapour phase, the number of overall gas transfer, units Nog is given by ... 

By analogy with the derivation for film coefficients, a series of overall transfer coefficients and overall transfer units based on these overall driving forces may be defined. Thus, the number of overall gas transfer units is given by ... 

If the driving force based on the gas concentration is written as (Y — Ye) and the overall gas transfer coefficient as Kg, then the height of the tower for dilute concentrations becomes ... 

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