Packings maximum efficient capacity

Figure 9-63B. Capacity correlation of structured Intalox 2T. The capacity parameter is at the maximum efficient capacity (MEC) point defined by Rukovena and Koshy [151]. The MEC point is iowerthan thefiood point and iocated where the packing wili maintain its desired efficiency. Used by permission of Rukovena, E. and Koshy, T. D., private communication, and Ind. and Eng. Cham. Res. V. 32, No. 10 (1993) p. 2400 all rights reserved.

The maximum operational capacity or throughput (often also referred to as maximum efficient capacity) is defined (Strigle, Packed Tower Design and Applications, 2d ed., Gulf Publishing, Houston, Tex., 1994) as the Maximum vapor rate that provides normal efficiency of a packing (i.e., point B in Fig. 14-54). The MOC is clear-cut in Fig. 14-54. On the other hand, locating the MOC in other cases is difficult and leaves a lot of room for subjectivity. 

For calculating the maximum efficient capacity fector ich determines the value of the gas velocity at maximal nms transfer efficiency of die column for the packing IMTP, Rukovena and Kodiy [291] presented figure 15. Here the value of Co for packings with different dimensions is presented as a fimction of the flow parameter... 

Rukovena and Koshy [291] present also the value of the maximum efficient capacity factor C,c (see Eq. (248) and Fig. 11 in Chapter 1) as a function of the flow parameter X for diifoent hi y effective corrugated packings. The data are given in Fig. 131. 

Packings Cg at Maximum Efficiency, ft/sec AP at Maximum Efficiency, H20/ft Cg at Maximum Capacity, ft/sec AP at Maximum Capacity, H20/ft... 

Thus, the column should completely resolve about 14 equally spaced peaks. It is seen from figure 1 that a peak capacity of 14 is not realized although most of the components are separated. This means that the column may not have been packed particularly well and/or the flow rate used was significantly above the optimum velocity that would provide the maximum efficiency. The mobile phase that was used was tetrahydrofuran which was sufficiently polar to deactivate the silica gel with a layer (or perhaps bilayer) of adsorbed solvent molecules yet was sufficiently dispersive to provide adequate sample... 

The maximum operational capacity or throughput is defined (15) as the Maximum vapor rate that provides normal efficiency of a packing (i.e., point F in Fig. 8.16a). 

Therefore, any column that is packed well for ultrahlgh resolution LC separations does not lose its maximum efficiency in SFC separations. However, the linear velocity (u) must be significantly higher, by a factor of at least three, to obtain the most efficient operation. Again, this is expected since the optimum linear velocity is inversely proportional to the particle diameter and directly proportional to the mobile phase/solute binary diffusivity (D12) and the solute capacity factor (k ) ... 

In distillation, maximum operational capacity (sometimes called efficient capacity because of the nature of the definition) is determined by the amount of liquid entrainment required to reduce separation efficiency (see Chapter 7). Data of Strigle and Rukovena for IMTP, metal Pall Ring, and ceramic Intalox saddle packings indicate that the pressure drop at maximum operational capacity is [11] ... 

The use of maximum operational capacity produces a design that provides the desired efficiency, and the packed bed does not operate in an unstable region near its hydraulic capacity limit. 

From Figure 7-6, the Cq value for 40 IMTP packing is 0.313 ft/s. Here the trayed column operating at a Cs of 0.225 ft/s is at 75% of the maximum operational capacity of 40 IMTP packing, after adjustment for system properties. Thus, a revamp with this packing can increase the trayed column capacity by 15%, even if the efficiency is no greater. 

The maximum operational is the greatest vapor flow rate attained before loss of normal separation efficiency of the packing (see Chapter 7). In vacuum distillations, massive entrainment of liquid upward in the vapor phase throughout the packed bed will limit the maximum operational capacity (maximum C ) because it reduces the separation efficiency. However, if liquid entrainment only occurs at the top of the bed, as long as the entrained liquid carried into the condenser is of the same composition as the reflux liquid, the separation is not impaired. Thus, some entrainment in the operation of the column is acceptable and simply constitutes a recycle of liquid in addition to the usual reflux. 

Maximum operational capacity—Maximum vapor rate that provides normal efficiency of a packing. 

The column can operate actually up to the flooding point F. But it is easy to see, that die maximal efficient capacity (MEC or C ) is reached in point G. That is why the detenninadon of this point is very important. The rate in it provides perfectly stable operation because it has been determined from the sepmation efficiency. This appro h to packed column capacity has been verified the investigation of Kunesh et al. [49]. The maximum hydraulic capacity of the packing is about 20% higher than dus in point G [3, p. 145]. 

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