Effect of gas velocity

P. Y. McCormick [Chem. Png. Prog., 58(6), 57 (1962)] compared all available data. The comparisons showed that flight geometry and shell speed should be accounted for in the value of K. He suggested that shell rotational speed and flight number and shape must affect the overall balance however, data for evaluating these variables separately are not available. Also, it is not beheved that the effect of gas velocity... 

This model apphes in the region belowthe loading point, and it cannot predict the flood point because it does not include the effects of gas velocity on liquici holdup. The model of Stichlmair et al. [Gas... 

FIG. 14-116 Experimental results showing effect of gas velocity and liquid load on entrainment from (a) vertical tube hanks with horizontal gas flow and (b) horizontal tnhe hanks with upflow. To convert meters per second to feet per second, multiply hy 3.281. (Calvert, Yung, and Leung, NTIS Publ PB-24S050. )... 

FIG. 20-88 Effect of gas velocity on maximiTm liquid rate for a sponted-bed seed coater. [Liu Litster, Powder Tech., 74, 259 (1993).] With laud permission from Elsevier Science SA, Lansanue, Switzerland. 

Figure 2 shows the effects of gas velocity on CO2 removal under the following conditions ... 

Fig. 6. Effects of gas velocity on the yields of oil and styrene monomer in a swirling fluidized-bed reactor (T=500°C).

Catalytic upgrading of bio-oil was carried out over Ga modified ZSM-5 for the pyrolysis of sawdust in a bubbling fluidized bed reactor. Effect of gas velocity (Uo/U ,f) on the yield of pyrolysis products was investigated. The maximum yield of oil products was found to be about 60% at the Uo/Umf of 4.0. The yield of gas was increased as catalyst added. HZSM-5 shows the larger gas yield than Ga/HZSM-5. When bio-oil was upgraded with HZSM-5 or Ga/HZSM-5, the amount of aromatics in product increased. Product yields over Ga/HZSM-5 shows higher amount of aromatic components such as benzene, toluene, xylene (BTX) than HZSM-5. 

The effect of gas velocity on the bed pressure drop (-APbed) with a uniform distributor (Fopen = 1.68 %) in the beds with decreasing and increasing Ug is shown in Fig. 5. As can be seen, -APbed maintains almost a constant value rmtil the minimum velocity of full fluidization (Unur) and then it decreases with decreasing Ug. As shown, Umfd is the maximum velocity of full defluidization, Umpf is the minimum velocity of partial fluidization, and Umu is the minimum velocity of full fluidization [6]. 

Figure 7. The effect of gas velocity on the critical capillary pressure.

Only Smith and Nienow (1983a) have reported a systematic investigation of the effects of gas velocity on granule size and on particle growth mechanisms. These authors used model materials (non-porous... 

Fig. 10. Correlation of film thickness with gas and liquid flow rates for air-water system in vertical flow, according to Zhivaikin (Zl). 1, 2 limits for onset of entrainment in downward and upward flow, respectively. 3, 3 limits for small effect of gas velocity on liquid flow (smooth wetted wall operation). 4, 4 region of film suspension. 5 limit for existence of film flow.

Figure 12. Effect of gas velocity on reaction front length...

Figure 5.2-22. Effect of gas velocity on pressure drop for different gas densities (after Wammes et al. [33]).

Zhivalkin (Z3), 1962 parabola with waves, profiles scattered about semiparabola. Entry effects also studied. Experimental work on film flow and upward and downward cocurrent gas/film flow (water and aqueous glycerol solutions). Data on onset of flooding and entrainment, effect of gas velocity. 

Effect of Gas Velocity Entrainment increases with gas velocity to a high power. Generally, smaller powers, indicative of a relatively gradual change, are typical of low-pressure systems. Higher powers, which indicate a steep change, are typical of high-pressure systems. 

Within the gas (0-10 cm/s superficial velocity) and liquid (0.6-2.5 cm/s superficial velocity) flow ranges investigated, a good liquid distribution was observed at all conditions, as manifested by uniformity factor in excess of 70%. The liquid saturation increases with increasing superficial liquid velocity as well as down the column height. Within the conditions studied, the effect of gas velocity was, in general, found to be minimal. 

Fig. 9 illustrates the effect of superficial gas and liquid velocities on the cross-sectionally averaged liquid saturation at the middle of the column (2.5D axial position). It is obvious that the effect of gas velocity on the liquid saturation is not significant within the range of flows studied. This could be due to the fact that solid and liquid holdups are very small, leaving enough space for the gas to flow upwards without significant interactions with the liquid phase flowing downward. 

The liquid saturation increases with increasing superficial liquid velocity. Moreover, the liquid saturation increases as the liquid phase moves downward. The liquid distribution was found to be fairly uniform in general as expressed by the uniformity factor which was relatively large, between 70 to 95%. Liquid distribution was better at the bottom of the bed, compared to the upper section. The effect of gas velocity, was in general, found to be very small at the conditions used in this study. 

Figure 10.7. Effects of gas velocity on the pressure drop of various system components in a CFB loop (after Rhodes and Laussmann, 1992).

Figure 12.17. Effect of gas velocity on the radial distribution of the heat transfer coefficient in a circulating fluidized bed (from Bi et at., 1989).

Figure 20 gives a typical curve for the effect of gas velocity and power level on mass transfer coefficient KGa. In a given application, knowledge of the required gas ab-... 

Figure 1. Effect of gas velocity, U , on conversion in a CO rich mixture. Numbers on curves are gas velocities (m/s). Key -----, water gas shift reaction included and--------------------, water gas shift reaction excluded.

They found that optimal conditions of the position of the stirrer exist in the range of 0.25 < HJd < 0.75 for both turbine and propeller stirrers. Their work suggests that beyond a Reynolds number of 20,000, the power number becomes constant. An increase in solid content increases the power consumption, while an increase in gas velocity reduces the power consumption. Kurten and Zehner (1979) examined the effect of gas velocity on the power consumption for suspension of solids and found that because of simultaneous aeration, a higher power input is required for suspension in the presence of gas. This is mainly due to the reduced liquid circulation velocity in the presence of gas bubbles. Most recently, Albal et al. (1983) evaluated the effect of liquid properties on power consumption for both two- and three-phase systems. They found that power consumption per unit volume increases with solid concentration. The influence of particle size on power consumption increases with the solids concentration. For an unconventional arrangement of a stirrer, they also found different Ne-Re curves for glycerine and CMC solutions. 

The effect of gas velocity on radial distribution of heat transfer coefficient is shown in Figs 9 and 10. With increasing gas velocity the heat transfer coefficients decrease. For the lower bed sections (see Fig. 10) the radial distributions are mainly affected by solids concentrations, and for the higher bed sections this trend changes significantly. 

Figure 17 shows that the effect of gas velocity on the profiles of local heat transfer coefficients is larger at the upper part of the probe than at the lower part. 

Gallery, D.J., The effect of gas velocity on fumigant action of nicotine, dichlorvos and hydrogen cyanide, ]. Stored Prod. Res., 3,17,1967. 

A review of earlier studies on gas, liquid, and solid holdups in a three-phase slurry reactor is given by Ostergaard.97 Kato54 studied the effects of gas velocity, particle size, the amount of solids and liquid in the bed, and the density of the solids on the gas holdup. The gas holdup [defined as volume of gas/(volume of gas + volume of liquid)] decreased with increasing particle size and amount of solids in the bed, and with the decreasing nominal gas velocity. 

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