Flooding rates

The packing parameter ( ) (m) reflects the influence of the Hquid flow rate as shown in Figure 20. reflects the influence of the gas flow rate, staying at unity below 50% of the flooding rate but beginning to decrease above this point. At 75% of the flooding velocity, = 0.6. Sc is the Schmidt number of the Hquid. 

Fig. 24. Souders load diagram for capacity limit determination for four stmctured packiags of the Sul2er-MeUapak type. The soHd lines represent the capacity limits of the respective packiags as defiaed by a pressure drop of 1.2 kPa/m (A) 125 Y (B) 250Y (C) 350Y (D) 500 Y. Flooding rates are about...

Ward and Sommerfeld [130] present an equation based on the curves shown in Figure 9-21C, D and referenced to Eckert [125] and Leva [43] for calculating the gas and liquid flooding rates. There have been numerous other equations targeted for this pmpose, but many are too awkward for easy general use. The proposed equations have been tested by the authors. 

Figure 9-38. Effect of choice of support plate on flooding rate. Used by pennission of U.S. Stoneware Co. (now, Norton Chemical Process Equipment Corp.).

Packed towers should operate near 70% of the flooding rate given by the correlation of Sherwood, Lobo, et al. 

A useful graphical correlation for flooding rates was first presented by Sherwood et a/.(60) and later developed by Lobo el al.(6l> for random-dumped packings, as shown in Figure 4.17 in which ... 

Figure 4.17. Generalised correlation for flooding rates in packed towers(6l)...

For a column operating at a given reflux ratio, L /G is constant and the only variables over the length of the column are, now, the minimum flooding rate GF and the gas density Pg In order to find the condition for a minimum or maximum value of GF, d G2F)/dpG is obtained from equation 4.53 and equated to zero. Thus ... 

Calculation of the pressure drop and flooding rate is particularly important for vacuum columns, in which the pressure may increase severalfold from the top to the bottom of the column. When a heat-sensitive liquid is distilled, the maximum temperature, and hence the pressure, at the bottom of the column is limited and hence the vapour rate must not exceed a certain value. In a vacuum column, the throughput is very low because of the high specific volume of the vapour, and the liquid reflux rate is generally so low that the liquid flow has little effect on the pressure drop. The pressure drop can be calculated by applying equation 4.15 over a differential height and integrating. Thus ... 

In the design of an absorption tower, the most important single factor is the value of the transfer coefficient or the height of the transfer unit. Whilst the total flowrates of the gas and liquid streams are fixed by the process, it is necessary to determine the most suitable flow per unit area through the column. The gas flow is limited by the fact that the flooding rate must not be exceeded and there will be a serious drop in performance if the liquid rate is very low. It is convenient to examine the effects of flowrates of the gas and liquid on the transfer coefficients, and also to investigate the influence of variables such as temperature, pressure, and diffusivity. 

Dell, F. R. and Pratt, H. R. C. Trans. Inst. Chem. Eng. 29 (1951) 89 Symposium on liquid-liquid extraction. Part I. Flooding rates for packed columns. 

Finally, the solved Y value for the extractor is used in Eq. (7.19) to solve for VCVD2 and subsequently the Vc value for the extractor, Eq. (7.20). Note that this Vc value is the 100% flood rate (ft/h) for the continuous phase in the extractor column. Please also note that the VD value is the 100% flood rate (ft/h) for the dispersed phase. 

Correlation for estimating flooding rate in packed towers. 

Figure 8-1 Correlation of Lobo for the prediction of flooding rates in fixed-bed columns.24...

Core Diameter (in.) Brine Permeability (md) Flood Rate (ft/day) Temperature (deg C) NaCl Brine (normality) ... 

Intense 10,000 Lumen Spotlight Or Flood—Rated Life 2,000 Hours, ... 

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