Tower packings characteristics

Relative Performance Characteristics of Tower Packing and Column Trays ... 

Determination of Packing Characteristics The packing characteristics are normally obtained from the tower manufacturer. Figure 8 illustrates the relationship between the height of a transfer unit for ammonia stripping and the GIL ratio for one type of packing... 

Packing characteristics. We have shown that the optimum steam rate that leads to minimum tower volume and minimum power is that of the ideal cascade (13.14). The optimum typ>e of packing, optimum pressure, and optimum vapor velocity is that which makes the expression in braces (1327) a minimum. We shall not attempt to evaluate a number of types of packing, but shall use Spraypak no. 37 packing as an example of the selection of optimum vapor velocity and pressure. This is the type of packing recommended by McWilliams and co-workers [M4] for a water distillation plant. 

At a different point in the packed distillation column of Example 3.6, the methanol content of the bulk of the gas phase is 76.2 mol% that of the bulk of the liquid phase is 60 mol%. The temperature at that point in the tower is around 343 K. The packing characteristics and flow rates at that point are such that Fg = 1.542 x 10-3 kmol/m2-s and Fr = 8.650 x 10-3 kmol/m2-s. Calculate the interfacial compositions and the local methanol flux. To calculate the latent heat of vaporization at the new temperature, modify the values given in Example 3.6 using Watson s method (Smith et al., 1996) ... 

This flow parameter is the square root of the ratio of liquid kinetic energy to gas kinetic energy. The ordinate of this correlation includes the gas flow rate, the gas and liquid densities, the a/e ratio (which is characteristic of the particular tower packing shape and size), and a liquid viscosity term. Lobo et al proposed the use of a packing factor to characterize a particular packing shape and size [17]. They determined that the a/e ratio did not adequately predict packing hydraulic performance. Eckert further modified this correlation and calculated the packing factors from experimentally determined pressure drops [18]. 

In liquid-film-controlled systems the value of Koa primarily is a function of the liquid flow rate. For most random dumped tower packings the value of the exponent b in Equation 3-13 lies between 0.22 and 0.34 the exact value is characteristic of the type of packing employed. If data on the particular packing are not readily available, it is suggested that this exponent be assumed as 0.30 for preliminary designs. In such liquid-film-controlled systems there is a very small effect of gas rate. The value of the exponent c in Equation 3-13 normally is only 0.06 to 0.08. Thus, if a standard Koa value for such a system is determined to be 6.0 Ib-mol/h... 

Modern tower packings provide a much lower pressure drop per theoretical stage than trays thus packed columns have been accepted readily for vacuum separations. As the operating pressure is increased, pressure drop becomes less important as a basis for selection of the fractionation device. Therefore, we will examine the other characteristics of both packings and trays to ascertain the potential applications for tower packings in high-pressure distillations. 

The tower packing, or fill, should offer the following characteristics ... 

In these expressions, B = ZJd, Nps = dVp/EE, Np r = dVn/Eii, where d = some characteristic length such as dp for packed towers or T for spray towers. Ep and Er are the longitudinal dispersion coefficients, which must ultimately be deter-... 

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