Design criterion

The design of single stage membrane units depends on the specific application 

There is a strong interaction between the demanded retentate concentration and the investment and operating costs of compressors, vacuum pumps and membrane modules. In any case a very low organic vapor concentration of the retentate 

For the design of the process and equipment, the following has to he considered and experimentally verified on lab and pilot scale [17]  

The above-mentioned factors not only determine the design pressures and temperatures but also the dimensions  

Besides the desired plant capacity, raw material and product specification are also necessary to get knowledge of local conditions like climate, altitude, and earthquake factor in order to design adequate building and service units, especially cooling machines and electrical drives. 

The right selection and preparation of the raw material are the determining factors for obtaining high-quality products. 

Depending on the final product requirement, processing conditions, pressure, temperature, mass flow, and pretreatment of raw materials are influenced and fractionated separation or further downstream treatment as concentration, removal of moisture, or purification may be required. 

The neutronic and thermal-hydraulic design criteria (limits for normal operations) of the Super LWR core are described next. 

Core shutdown margin greater than or equal to l%dk/k. 

The control rods are used for the normal shutdown of the Super LWR core. The shutdown margin is the negative reactivity of the core when all control rods are inserted into the core and the core is at the shutdown state. This is an important index for the core ability to be shut down. Usually, the core shutdown margin is evaluated with the assumption that the insertion of the control rod with the 

The inherent safety feature is the tendency of the system to fall to the safer side when a positive reactivity is inserted. The main contributions to the inherent safety features of the Super LWR are the positive coolant (and moderator) density reactivity coefficient (which is equivalent to the negative void reactivity coefficient of the BWR) and the negative Doppler reactivity coefficient. These inherent safeties should be maintained throughout the operation. 

1 Thermal Design Criteria (Thermal Limit for Normal Operations) 

Jenike [8, 9] and his coworkers did extensive work on gravity flow of bulk solids, both experimental and theoretical. He developed design methods and criteria for hoppers and bins with steady mass flow without disturbances. In determining various flow criteria, Jenike used a function termed flow factor . This flow factor is the ratio of the consolidating pressure a, to the stress acting on an exposed surface op 

The stress acting on an exposed surface is also the only non-zero principal stress, because the exposed surface is assumed self-supporting and traction-free (i.e., no shear stresses acting on the surface). The flow factor is determined by the geometry of the hopper and the properties of the bulk material. Another function used by Jenike is the flow function . This flow function is the ratio of the consolidating pressure CTi to the unconfined yield strength as defined in Section 6.1.2  

The flow function is a material property it gives an indication of the flowability of a bulk material  

As a general rule, solids that do not contain particles smaller than approximately 0.2 mm are free flowing thus, most granular solids are free flowing and most powders are to some extent cohesive. 

The exposed surface, whether it is an arch or a pipe, is stable when the unconfined yield strength is higher than the stress acting on the exposed surface Oj and unstable when is less than The condition for no arching or piping, therefore, is  

Fluidized Bed Coating Equipment. In reviewing the literature, it is evident that there are a great many variations in fluidized bed equipment used in coating applications (Olsen, 1989a and 1989b Jones, 1985 and Mehta, 

Nevertheless, we may categorize all the equipment into four main groups. Each group is discussed below 

For organic solvent processes, the humidity of the air can also play a role in the product quality. One particular problem which can arise is that of condensation of water in the bed. In the vicinity of the nozzle, local cooling may be experienced due to solvent evaporation (Smith and Nienow, 1982), as discussed in Sec. 2.3. Asa consequence of this local cooling, the temperature 

In addition to inlet gas filtering, it is usually necessary to use some form of filter downstream of the fluidized bed to avoid solid carryover. For fairly large particles, this is usually achieved by bag filters or screens for very fine powders, abaghouse and cyclones may be necessary. 

Recently, the use of microwave heating has also been applied successfully to coating processes. The use of internal heating surfaces is usually not practical since these would tend to clog and foul during the process. 

A large number of parameters are involved in the choice of the corrosion protection system and the provision of the protection current these are described elsewhere (see Chapters 6 and 17). In particular, for new locations of fixed production platforms, a knowledge of, for example, water temperature, oxygen content, conductivity, flow rate, chemical composition, biological activity, and abrasion by sand is useful. Measurements must be carried out at the sea location over a long period, so that an increased margin of safety can be calculated. 

The protection potentials for seawater are described in Section 2.4. In pipelines and harbor installations, there is no limiting negative potential f/ for uncoated carbon steel or for steel provided with thick coatings over 1 mm, with yield points up to 800 N mm . With dynamically highly loaded structures, the protection potential ranges in Table 16-2 should be adhered to as in the regulations [1-3] because of the risk of hydrogen-induced stress corrosion (see Section 2.3.4). 

The reference potential of the Ag-AgCl electrode in brackish water must be corrected for chloride ion content (i.e., a change in chloride ion concentration by a factor of 10 shifts the reference potential by about 50 mV in the positive direction 

Marine structure Reference electrode Cu-CuS04 (V) Ag-AgCl in seawater (V) Zn (V) 

In determining the protection current required, the surfaces of the objects to be protected in the water and on the seabed, as well as those of foreign constructions that are electrically connected to the object to be protected, should be isolated. The protection current densities derived from experience and measurements for various sea areas are given in Table 16-3. In exceptional cases measurements must be carried out beforehand at the location of the installation. Such investigations, however, provide little information on the long-term development of the protection current. By using a suitable coating [4], the protection current density in the early years of service will be only about 10% of the values in Table 16-3. For a planned operational lifetime of 30 years, about 50% of these values is necessary. 

a structure is anodically protected if the metal is active-passive and shows a sufficiently large passive potential range, eq. (9.1), due to the formation of a dynamic oxide film. This implies that the current density depends on time and therefore, the power supply must provide the required potential Ex so that ix icorr [ ] Thus, anodic polarization results due to the formation of an insoluble oxide film of a few nm in thickness. The effectiveness of anodic protection depends on the quality of the oxide film in a particular environment and the applied potential. For instance, if the applied potential is Ex Ep, then the film corrodes by pitting, which is a localized electrochemical process. On the other hand, if Ex Epa the metal corrodes by general and uniform process. 

Passivation may be accomplished due to the accumulation of reacting ions forming an oxide film (metallic coating) on the anode surface. Consequently, the current flowing from the anode to the electrolyte reduces since the metallic coating has a high electric resistance. This can be defined by Ohm s law 

The potential Ex is assumed to be constant since anodic protection AP) is a potential-control technique, in which the power supply is a potentiostat capable of supplying a constant potential otherwise, a significant change in potential causes a change in the current and the stmcture may become unprotected due to film breakdown. 

Since the anodic protection technique is restricted to materials that exhibit active-passive transitions, it is important to determine the sensitiveness of the polarization behavior of metallic material exposed tosolutions containing contaminants, such as chloride ions, and temperature. 

Whether a polymerization is carried out on a small scale in the laboratory or on a commercial scale in an industrial complex, one must deal with certain issues. The viscosity of the reaction mixture and the control of temperature are the most prominent. Usually the larger the scale of production, the more difficult it becomes to maintain uniform conditions. 

Many of the problems that attend mechanical design of polymerization systems are common to ordinary organic reactions. Toxic and flammable monomers and catalysts, noxious odors, and sticky solids are dealt with routinely in chemical and petroleum plants. Some notable examples in the field of commercial polymer processes are as follows  

Toxicity. Acrylonitrile (CH2=CH—CN) has the toxicity of inorganic cyanides. A maximal concentration of 20 ppm in air is recommended for 8-h exposures. 

Flammability. Many Ziegler catalysts involve aluminum triethyl, which is pyrophoric (bursts spontaneously into flames on exposure to air). 

The lower acrylates can have odors that are penetrating and disagreeable even in low concentrations. Special catalytic systans may be installed to destroy traces of monomer in effluent gas streams. 

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The pinch design method developed earlier followed several rules and guidelines to allow design for minimum utility (or maximum energy recovery) in the minimum number of units. Occasionally, it appears not to be possible to create the appropriate matches because one or other of the design criteria cannot be satisfied. 

The requirements of the analysis determine the best method. In choosing a method, consideration is given to some or all the following design criteria accuracy, precision, sensitivity, selectivity, robustness, ruggedness, scale of operation, analysis time, availability of equipment, and cost. Each of these criteria is considered in more detail in the following sections. 

When designing and evaluating an analytical method, we usually make three separate considerations of experimental error. First, before beginning an analysis, errors associated with each measurement are evaluated to ensure that their cumulative effect will not limit the utility of the analysis. Errors known or believed to affect the result can then be minimized. Second, during the analysis the measurement process is monitored, ensuring that it remains under control. Finally, at the end of the analysis the quality of the measurements and the result are evaluated and compared with the original design criteria. This chapter is an introduction to the sources and evaluation of errors in analytical measurements, the effect of measurement error on the result of an analysis, and the statistical analysis of data. 

T ablation temperature No general trend. Depends on interaction with other parameters and design criteria. None except as an indicator of whether or not ablation will occur. 

Solid Propellant Selection and Characterisation, Space Vehicle Design Criteria, Monograph no. SP 8064, NASA, Airport, Md., 1971. 

Scale-up and performance of a 1.47-m Scheibel column have been reported (98,154,155), as have detailed description and design criteria for the Scheibel column (156) and scale-up procedures (157). The same stage efficiency can be maintained on scale-up, and total throughput can be increased by three and one-half times at the expense of higher HETS. As of this writing, Scheibel columns up to 2.75 m in diameter are in service. 

The rotating-disk contactor (RDC), developed in the Netherlands (158) in 1951, uses the shearing action of a rapidly rotating disk to interdisperse the phases (Eig. 15b). These contactors have been used widely throughout the world, particularly in the petrochemical industry for furfural [98-01-1] and SO2 extraction, propane deasphalting, sulfolane [126-33-0] extraction for separation of aromatics, and caprolactam (qv) [105-60-2] purification. Columns up to 4.27 m in diameter are in service. An extensive study (159) has provided an excellent theoretical framework for scale-up. A design manual has also been compiled (160). Detailed descriptions and design criteria for the RDC may also be found (161). 

The Oldshue-Rushton column (Eig. 15d) was developed (162) in the early 1950s and has been widely used in the chemical industry. It consists essentially of a number of compartments separated by horizontal stator-ring baffles, each fitted with vertical baffles and a turbine-type impeller mounted on a central shaft. Columns up to 2.74 m in diameter have been reported in service (162—167). Scale-up is reported to be reliably predictable (168) although only limited performance data are available (169). A detailed description and review of design criteria are available (170). 

Kuhni contacters (Eig. 15e) have gained considerable commercial application. The principal features are the use of a shrouded impeller to promote radial discharge within the compartments, and a variable hole arrangement to allow flexibility of design for different process applications. Columns up to 5 m in diameter have been constmcted (176). Description and design criteria for Kuhni extraction columns have been reported (177,178). 

Due to thek similarity to a-c furnaces, d-c furnaces can be substituted for neatly any a-c furnace including the open-arc, submerged-arc, and arc-resistance furnaces, provided that design criteria, particularly electrical parameters, are properly chosen. Currently, steel and ferrochrome is being made commercially in d-c furnaces and a siUcon metal pilot plant is being built. 

Eig. 11. Liquid-cooled cold plates or heat sinks have been developed as thermal management solutions to cool components for Hquid-cooled computer systems and other electronic systems where heat removal becomes one of the important design criteria. 

Codes Standards approved the estabUshment of a Special Working Group for high pressure vessels under the ASME Subcommittee on Pressure Vessels (Section VIII). The main design criteria, which are likely to be incorporated in a new Division of Section VIII, have been set out (149). 

Design Criteria. Traditionally the yield pressure has been regarded as an important design criterion because it is the largest pressure to which an initially stress-free cylinder may be subjected without the cylinder suffering any permanent deformation when the pressure is removed. Customarily,... 

Exact design criteria on equipment for handling acetylene is not readily available because of the great number of factors involved. However, recommendations have been made concerning the equipment, piping, compressors, flash arresters, and proper materials (69,92—94). 

ALWRs are expected to be deployed ia the United States and ia Asian counties. However, France will use improved versions of standard reactors, considering them to be amply safe and economical. The reactors were modified after the Three-Mile Island-2 (TMI-2) accident. The company Framatome that has built most of the reactors of France is associated with Babcock Wilcox ia the United States. The new Framatome 1500 MWe N4 PWR is an extension of the successful four-loop units of 1300 MWe originally designed by Westiaghouse. Full emphasis is givea to safety, ecoaomy, and rehabiUty. More severe design criteria than those ia the former model have beea adopted. 

R. H. Herbert III, Roofing Design, Criteria, Options Selection, R. S. Means Co., Inc., Kingston, Mass., 1989. 

Design criteria for carbon adsorption include type and concentration of contaminant, hydrauhc loading, bed depth, and contact time. Typical ranges are 1.4—6.8 L/s/m for hydrauhc loading, 1.5—9.1 m for bed depth, and 10—50 minutes for contact time (1). The adsorption capacity for a particular compound or mixed waste stream can be deterrnined as an adsorption isotherm and pilot tested. The adsorption isotherm relates the observed effluent concentration to the amount of material adsorbed per mass of carbon. 

Low concentrations of oil can be removed by dissolved air flotation (DAF). In this process, an effluent recycle is pressurized in the presence of excess air, causing additional air to go into solution, in accordance with Henry s Law. When this water is discharged to the inlet chamber of the flotation unit at close to atmospheric pressure, the dissolved air comes out of solution in the form of tiny air bubbles which attach themselves to and become enmeshed in suspended solids and oil globules. The primary design criteria is the air/solids ratio, which is defined as the mass of air released divided by the mass of solids fed. Sufficient air must be released to capture the solids in the influent wastewater. The performance of DAF for the treatment of several... 

Giaphite with its exceptional strength and thermal stabiUty at high temperatures is a prime candidate material for many aerospace and nuclear appHcations. Its properties, through process modifications, are tailorable to meet an array of design criteria for survival under extremely harsh environmental operations. 

R. O. Voth, J. D. Siegworth, J. F. Welch and M. J. Hi2a, Process Design Criteria, Data and Metrology Related to Slush Hydrogen Technology, NASA Tech. Memo 1006, NASA Langley Res. Cntr.,Mar., 1987. 

Rules are cleady a usehil form of representation for knowledge-based appHcations, with their advantages of representational simplicity, wide apphcabihty, and history of past successes. However, certain important design criteria govern the proper appHcation of rules and there are shortcomings of the rule-based representation. 

Design Criteria Metallic Pipe The code uses three different approaches to design, as follows ... 

FIG. 17-69 Design curves for electrostatic precipitators for fly ash. Collection efficiency for various levels of percent sulfur in coal versus a) specific collecting surface, and (h) bus sections per 100,000 ftVmin (4.7 mVs). °C = (°F — 32) X (Ramsdell, Design Criteria for Precipitators for Modern Central Station Power Plants, Amen c m Power Conference, Chicago, III., 1968. )... 

TABLE 18-7 Typical Thickener and Clarifier Design Criteria and Operating Conditions... 

Design Criteria Jenike s criteria permit an engmeering-eeonomie analysis of storage with about the same confidence level... 

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