Operating principle

Traps distinguish between steam, condensate, and noncondensables by three principles density difference, temperature differences, and phase change. These principles are used in the three major trap types mechanical, thermostatic, and thermodynamic. 

For a given operating condition, the density of condensate is considerably different from that of steam or air. The principle is used by mechanical-type traps. This density difference always exists, except at the critical pressure however, the densities of steam and air are too close for distinction. It is also important to note that any flash steam produced in the line from the calandria is regarded as live steam. The trap will dose even though condensate is foilowing the pocket of flash steam. 

Over the past three decades, there has been a growing industrial interest in using reverse osmosis for several objectives such as water purification and demineralization as well as environmental plications (e.g.. Comb, 1994 Rorech and Bond, 1993, El-Halwagi, 1992). The first step in designing the system is to understand the operating principles and modeling of RO modules. 

Typically RO systems are preceded by pretreatment units to remove suspended solids/colloidal matter and add chemicals that control biological growth and reduce scaling. Membranes are typically made of synthetic polymers coated on a backing (skin). Examples of membrane materials include polyamides, cellulose acetate and sulfonated polysulfone. 

A hollow-fiber reverse-osmosis module consists of a shell which houses the hollow fibers (Fig. 11.3). The fibers are grouped together in a bundle with one end sealed and the other open to the atmosphere. The open ends of the fibers are potted into Ml epoxy sealing head plate after which the permeate is collected. The pressurized feed solution (denoted by the shell side fluid) flows radially from a central porous tubular distributor. As the feed solution flows around the outer side of the fibers toward the shell perimeter, the permeate solution penetrates through the fiber wall into the bore side by virtue of reverse osmosis. The permeate is collected at the open ends of the fibers. The reject solution is collected at the porous wall of the shell. 

In modeling an RO unit, two aspects should be considered membrane transport equations and hydrodynamic modeling of the RO module. The membrane transport equations represent the phenomena (water permeation, solute flux, etc.) taking place at the membrane surface. On the other hand, the hydrodynamic model deals with the macroscopic transport of the various species along with the momentum and energy associated with them. In recent years, a number of mathematical 

CHAPTER ELEVEN Design of membrane-separation systems 

Typically RO systems aie preceded by pretreatment units to remove suspended 

Assuinmg diat the deiisities erf the feed, the pmmeiUe and the reject are the same, one can write the following overall material baUuice aroimd the module  

In addition to material balance, two transport equations can be used to predict tiie flux of water and solute. For instance, the following simplified model can be used (Dandavati et ah, 1975 Evangelista, 1986). 

Photo diode array (PDA) Specific Same as UV/Vis detectors, also provides UV spectra ng-pg 

Fluorescence (FI) Very specific Compounds with native fluorescence or with fluorescent tag fg-Pg 

Refractive index (RI) Universal polymers, sugars, triglycerides, organic acids, excipients not compatible with gradient analysis 0.1-10 pg 

Evaporative light scattering (ELSD) Universal nonvolatile or semivolatile compounds, compatible with gradient analysis 10 ng 

Corona-charged aerosol (CAD) Universal use nebulizer technology like ELSD and detection of charges induced by a high-voltage corona wire Low ng 

Bi(r) r.f. jMilse perpet icular to Bo- Magnetic flux densities are denoted by B, magnetic fields by and x the nuclear magnetic susceptibility. 

Assuming 0.01 and 0.6 molarity for freshwater and seawater, respectively, the resulting pressure difference is 28.7 bar at 20°C, equivalent to an hydrostatic head of 293 m. 

In reverse osmosis (RO) instead, the hydraulic pressure applied to the saltwater side is so high to exceed the osmotic pressure difference and water permeates from the high-to the low-concentration membrane side. This operating concept is largely applied in desalinization plants. 

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The basic operation principles of the AEBIL system can be translated into a sequence of elementary processing steps and summarized as follows (fjg. 1). 

Figure 1 Operating Principles of an Automated ASTM-Bulb...

The selection of the operating principle and the design of the calorimeter depends upon the nature of the process to be studied and on the experimental procedures required. Flowever, the type of calorimeter necessary to study a particular process is not unique and can depend upon subjective factors such as teclmical restrictions, resources, traditions of the laboratory and the inclinations of the researcher. 

Fig. 13. Operating principle of two-stage electrical precipitator. From Ref. 205,...

Fig. 10. Operating principle of a common design of pellet mill A, loose material is fed into pelleting chamber B, rotation of die and roller pressure forces material through die, compressing it into pellets and C, adjustable knives cut pellets to desired length. Courtesy of California Pellet Mill Co.

Alpha counting is done with an internal proportional counter or a scintiUation counter. Beta counting is carried out with an internal or external proportional gas-flow chamber or an end-window Geiger-MueUer tube. The operating principles and descriptions of various counting instmments are available, as are techniques for determining various radioelements in aqueous solution (20,44). A laboratory manual of radiochemical procedures has been compiled for analysis of specific radionucHdes in drinking water (45). Detector efficiency should be deterrnined with commercially available sources of known activity. 

Through-type separators are more effective for larger municipal and industrial treatment faciHfies. The operating principles are the same, but flow is through a trough rather than a column. 

There are a wide variety of coatiag appHcatioas processes ia use. The majority of these techniques are similar to those used ia other coatiags iadustries, and the same basic operating principles apply to these uses as to coatiag a photographic film or a coil of metal for a refrigerator. 

FIG. 18-124 Operating principles of a roll-discharge mechanism. (Schweitzer, Handbook of Separation Techniques for Chemical Engineers, p, 4-40, Copyiight 1979 hy McGraw-Hill, Inc, Used with peimission of McGraw-Hill Book Co,)... 

Another type of classifier directs an air stream across a stream of the particles to be classified. An example is the radial-flow classifier Kennedy Van Saun Corp.), which Features adjustable elements to control the flow and classification. A further development on this principle is the Vari-Mesh classifier Kennedy Van Saun Corp.), which controls classification by adjustable flow baffles. A change in direction of air flow is the operating principle of the reverse-flow Superfine classifier Hosokawa Mineral Processing Systems). 

Electromagnetic These are quickly outdated but we discuss these relays briefly below to give an idea of the basic operating principles of such relays. The same principle of application is then transformed into a static or microprocessor-based relay... 

Inadequate NPSHa causes stress, vibration and maintenance on pumps because there is not enough energy in the iluid for the pump to perform its work. As you can see from the previous pages, the problems lie in system design and proper operating principles. When the NPSHa is below the NPSHr of the pump, the conditions are favorable for the pump to go into cavitation. Cavitation is tlie next chapter. 

Operating Principles and Design Features Radial Bearings... 

This type of technology is a part of the group of air pollution controls collectively referred to as "wet scrubbers. Orifice scrubbers are also known as self-induced spray scrubbers, gas-induced spray scrubbers, and entrainment scrubbers. The operating principle is based on the removal of air pollutants by inertial and diffusional interception. 

Disk Filters Disk filters consist of a number of concentric disks mounted on a horizontal rotary shaft. The operating principle is the same as that of rotary-drum vacuum filters. The basic design is illustrated in Figure 22. The disks are formed by using V-shaped hollow sectors assembled radially about a central shaft. Each sector is covered with filter cloth and has an outlet nipple coimected to a manifold... 

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