Separators design

In addition to discussing phase separators, it is also appropriate to consider the application of accumulators in processes. Accumulators or surge vessels are necessary to reduce fluctuations in flow rate, pressure and composition and thereby improve process control. Although accumulators are not phase separators, they are discussed here because they are sometimes contained in the same vessel as a phase separator. For example, in a gas-liquid separator, the volume of liquid at the bottom of the separator is determined by the need to dampen fluctuations in flow rate. 

Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016 

Most vessels in the process industries are thin-walled vessels, which have a wall thickness of less than about 5% of the inside diameter of a vessel. Internal pressure acting on the walls of a cylindrical vessel produces a longitudinal and radial stress, also called hoop stress. For thin-wall vessels, it may be assumed that the radial stress is approximately uniform across the wall. Rase and Borrow [1], for example, showed that the radial stress, produced by an internal pressure, P, is given by Equation 6.1. 

Vessels larger in diameter than about 30 in (0.672 m) and above are fabricated from plates, which are formed into cylinders, called shells, and welded longitudinally. Shells smaller than 30 in (0.672) may be extruded and thus will not contain a longitudinal weld. Shells may then be joined by welding circumferentially to form longer shells. After fabricating the shell, end caps, called heads, are welded to the shell to form the vessel. Because the weld may have imperfections, the radial stress will be less than its maximum value. Thus, S is multiplied by a joint or weld efficiency, e, which depends on the type of x-ray inspection of the weld. Thus, 

As pointed out in the preceding reviews of separator function and separator materials (Chapters 6 and 7, respectively) and of charging strategies (Chapter 9), the separator plays a crucial role in VRLA cells. Provision of a separator with the appropriate microstructure can constrain the rate of oxygen arrival at the negative plate and thus restrict the suppression of the plate potential caused by the oxygen-recombination reaction. 

The active material on the positive plate generally presents a surface area which is significantly greater than that of the negative plate. This manifests itself as a difference in the flux of electrons to the reaction sites on the two plates. If the surface available at the negative plate can be extended, then the influence of the unequal dependence on diffusion in negative and positive plates can be reduced. 

---

In modern separation design, a significant part of many phase-equilibrium calculations is the mathematical representation of pure-component and mixture enthalpies. Enthalpy estimates are important not only for determination of heat loads, but also for adiabatic flash and distillation computations. Further, mixture enthalpy data, when available, are useful for extending vapor-liquid equilibria to higher (or lower) temperatures, through the Gibbs-Helmholtz equation. ... 

Figure 1.3 For a given reactor and separator design, there are different possibilities for heat integration. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

Although there are many variations in separator design, certain components are common. 

Equipment Separator designs differ for the various types of materiafs to be separated. In general, magnetic separation devices can be grouped as follows ... 

The problem of efficient catalyst recovery from the flue gas has since been overcome by Shell, which has an external separator design... 

Support plate used as a vapor distributor with restricted open area. Reduced capacity in order to make separation. Design error. 

Inadequate vapor distribution to packed bed. Poor separation. Design omission. 

Coker, A. K., Computer Program Enhanees Guidelines for Gas-Liquid Separator Designs, Oil Gas Journal, May 1993. 

Note that the presented particle collection efficiencies cannot be assumed to be for the best available technology and are shown for equipment existing in industry. Dimensioning of particle removal equipment makes it possible to achieve better removal efficiencies in most cases presented in Table 13.1. All particulate and gas-cleaning equipment must be separately designed to meet specified local conditions. 

Phase equilibria The relationship be tween contaminant solubility in the gas and liquid phases at equilibrium, which must be known for absorption separator design. 

Provide separate designated areas for holding product awaiting inspection, passed inspection, and failed inspection. 

Cavoy E., Deltent M. E, Lehoucq S., Miggiano D. (1997) Laboratory-Developed Simulated Moving Bed for Chiral Drug Separations. Design of the System and Separation of Tramadol Enantiomers, J. Chrotnatogr. A 769 49-57. 

Some examples of calculated pressure gradients are shown in Figure 5.12 in which solids concentration is a parameter. Experimental points are given, with separate designations for each concentration band. The difference between experimental and predicted value does not generally exceed about 15 per cent. 

Since much of the vented material will be liquid, separators such as knockout pots or tangential entry separators can provide disengagement and possible recovery. Figure 5 is a typical vapor-liquid separator design found to be effective for these applications. Inlet design superficial vapor velocity is about 100 ft/sec, with sufficient volume provided to accumulate the entire reactor liquid contents. The lip on the outlet vapor line and the horizontal plate to separate the accumulated liquid are important features to prevent re-entrainment. 

The data reported are permeabilities, not fluxes. Flux is proportional to permeability/thickness. The separations designer must deal with real membranes, for which thickness is determined by factors outside the designer s control. It is vital that flux data are used in design. 

Besides the incorporation of a high field gradient, a magnetic separator design should have ... 

Although side-stripper arrangements have been routinely used in the petroleum industry and side-rectifiers in air separation, designers have been reluctant to use the fully thermally coupled arrangements in practical applications until recently12 15 16. 

Thomson, S.J. Data Improves Separator Design, Hydrocarbon Processing, Oct. 1973, p. 81. 

For the d-d transitions the excited states arise from the (a2 7r 52) and (on 3) configuration, but separate designations are not given since many of the levels are appreciably mixed by configuration interaction. 

A sewer network and any corresponding treatment have traditionally been separately designed and operated. Two different and separate functions have been dealt with the sewer system must collect and convey the wastewater to the treatment plant, and the treatment plant must reduce pollution load into the receiving water according to the quality standards set. Consequently, sewers are often just considered input systems at the boundaries where they are connected with wastewater treatment plants and overflow structures that discharge untreated wastewater into watercourses during rainfall. This traditional approach to sewer performance needs considerable improvement. 

FIG. 23-53 Cyclone separator design details. (Guidelines for Pressure Relief and Effluent Handling Systems, Center for Chemical Frocess Safely (CCPS) of the American Institute of Chemical Engineers (AIChE) copyright 1988 AIChE and reproduced with permission.). 

---