Tower sizing, detailed

The absorber is essentially the same as that described for the single-pressure process. Tower size and specific design details can be optimized to the particular process conditions and may vary... 

Detailed tower sizing for diameter and height iterate on packing selection until overall design criteria are met. 

The desaiption of the apparatus has, of necessity, to be somewhat general, as these plants are made in sizes varying from 1500 to 60,000 cubic feet per hour production and consequently differ in detail thus, in large plants, the tube condenser is not employed and the hot hydrogen passes up a tower packed with coke, down... 

The costs of three sizes of a proprietary dual-phase extraction system were estimated in 1991. The costs associated with Radian International s AquaDetox/SVE system (see summary T0641) are detailed in Table 1. The system uses a moderate vacuum stripping tower and low-pressure... 

Optimum Reflux Ratio. The reflux ratio affects the cost of the tower, both in the number of trays and the diameter, as well as the cost of operation which consists of costs of heat and cooling supply and power for the reflux pump. Accordingly, the proper basis for choice of an optimum reflux ratio is an economic balance. The sizing and economic factors are considered in a later section, but reference may be made now to the results of such balances summarized in Table 13.3. The general conclusion may be drawn that the optimum reflux ratio is about 1.2 times the minimum, and also that the number of trays is about 2.0 times the minimum. Although these conclusions are based on studies of systems with nearly ideal vapor-liquid equilibria near atmospheric pressure, they often are applied more generally, sometimes as a starting basis for more detailed analysis of reflux and tray requirements. 

Chemical process equipment is of two kinds custom designed and built, or proprietary off the shelf. For example, the sizes and performance of custom equipment such as distillation towers, drums, and heat exchangers are derived by the process engineer on the basis of established principles and data, although some mechanical details remain in accordance with safe practice codes and individual fabrication practices. 

Air paths may be crossflow or counterflow. Fan placement can be ahead of the fill section (forced draft) or behind it (induced draft). Manufacturers use different criteria in sizing units. Figure 4.18 reviews one tower manufacturer s approach. Specific design details should be obtained from the tower manufacturer. 

To determine the required size of an absorption or stripping nrtl, it is necessary to know not only the equilibrium soluhility of the solute in the solvent and the material balance atound the column bas also the rate at which solute is transferred from one phase to the other within the tower. This rale directly affects the volume of packing needed in a packed tower, the degree of dispersion requited in a spray contactor, and (somewhat less directly) the number of trays required in a nay tower. The last effect occurs as a result of the influence of mass transfer rms on tray efficiency which is discussed in a later section. Because of its direct effect ou packed tower design and the importance of this type of contactor in absoiption. this discussion of mass transfer is aimed primarily at the packed tower case. A more detailed review of mass transfer theoty is given in Chapter 2. 

After the simulation file is augmented, the revised simulation is run and the results are sent to Aspen IPE. Note that the ASPEN PLUS and HYSYS.Plant simulators contain menu entries to direct the results to Aspen IPE. For details, the reader is referred to course notes prepared at the University of Pennsylvania (Nathanson and Seider, 2003), which are provided in the file. Aspen IPE Course Notes.pdf, on this CD-ROM. This section presents estimates of equipment sizes and purchase and installation costs using Aspen IPE for two examples involving (1) the depropanizer distillation tower presented on the CD-ROM (either HYSYS —> Separations —> Distillation or ASPEN PLUS Separations Distillation), and (2) the monochlorobenzene (MCB) separation process introduced in Section 4.4, with simulation results using ASPEN PLUS provided on the CD-ROM (ASPEN Principles of Flowsheet Simulation —> Interpretation of Input and Output —> Sample Problem). Just the key specifications and results are presented here. The details of using Aspen IPE for these two examples are presented in the file. Aspen IPE Course Notes.pdf... 

Another distinguishing feature of ferroelectric behavior is the polarization versus electric field P—B) hysteresis loop. The hysteresis loop results from the domain reorientation which occurs as the electric field direction is varied. The size and shape of the loop is determined by the magnitude of the dipole moment of the unit cell and the domain-switching characteristics of the material. Hysteresis loop behavior is measured using either a Sawyer—Tower circuit or a Diamant—Pepinsky bridge. Details of the construction and operation of a Sawyer—Tower circuit are given in Reference 24. Thin film properties have also been measmed with these two devices, and in addition, a commercially available measurement system has been widely used. ... 

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