Height of packings

Therefore, in this case, one transfer unit corresponds to the height of packing required to effect a composition change just equal to the average driving force. 

E] Use s BoUes Fair (Ref. 75) data base to determine new effective area to use with Onda et al. (Ref. 126) correlation. Same definitions as 5-28-D. P = total pressure, atm Mq = gas, molecular weight m = local slope of equilibrium curve Lf /Gf = slope operating line Z = height of packing in feet. 

Use of HETP Data for Absorber Design Distillation design methods (see Sec. 13) normally involve determination of the number of theoretical equihbrium stages or plates N. Thus, when packed towers are employed in distillation appRcations, it is common practice to rate the efficiency of tower packings in terms of the height of packing equivalent to one theoretical plate (HETP). 

By using the series of experimentally measured rates of absorption, Eq. (14-69) can be integrated numericaUy to determine the height of packing required in the commercial tower. 

This is the gas-phase mass-transfer limited condition, which can be substituted into Eq. (14-71) to obtain the following equation for calculating the height of packing for a dilute system ... 

For fast irreversible chemical reactions, therefore, the principles of rigorous absorber design can be applied by first estabhshing the effects of the chemical reaction on /cl and then employing the appropriate material-balance and rate equations in Eq. (14-71) to perform the integration to compute the required height of packing. 

In design practice, a less rigorous parameter, HETP, is used as an index of packing efficiency. Tne HETP is the height of packed bed required to achieve a theoretical stage. The terms Hoe and HETP may be related under certain conditions ... 

A packed column is used in the desulfurization operation described in the previous problem. The overall height of transfer unit based on the gas phase is 0.7 m. WTien the flowrate of water is twice the minimum, what height of packing is needed ... 

Nql = number of transfer units, based on overall liquid film coefficients Z = height of packing, ft... 

Z = height of packed section in tower, ft Apim = log mean partial pressure of gas in inlet and exit gas streams, atm... 

The height of the transfer unit has not been satisfactorily correlated for application to a wide variety of systems. If pilot plant or other acceptable data are available to represent the system, then the height of packing can be safely scaled-up to commercial units. If such data are not available, rough approximations may be made by determining Hg and Hl as for absorption and combining to obtain an Hqg (Ref. 74, pg. 330). This is only very approximate. In fact it is because of the lack of any volume of data on commercial units that many potential applications of packed towers are designed as tray towers. 

Having selected a type and height of pack, the above equation can be plotted to intersect with the required demand curve to obtain the L/G. With the L/G and the given amount of water to be cooled, the air requirement can be calculated for ... 

Height of packing for both natural and mechanical draught towers... 

Who is the required height of packing and the condition of the exit air stream1. ... 

Temperatures Tl in and Tq in will also be known. The problem then consists of determining the height of packing required to obtain the above separation. 

Liquid temperature Mole ratio c in the liquid phase Mole fraction in the liquid phase Mole ratio in the gas phase Mole fraction in the gas phase Height of packing Exothermic heat of adsorption... 

Where the concentration of the solute is small, say less than 10 per cent, the flow of gas and liquid will be essentially constant throughout the column, and the height of packing required, Z, is given by ... 

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