Flow-system design procedure

Just as the electrical engineer selects resistors, capacitors, and transistors when designing an electric circuit, the chemical engineer selects valves, piunps, and flow meters to produce a flow system. The procedure followed in the design of a flow system is to determine ... 

This section discusses the principal causes of overpressure in refinery equipment and describes design procedures for minimizing the effects of these causes. Overpressure is the result of an unbalance or disruption of the normal flows of material and energy that cause material or energy, or both, to build up in some part of the system. Analysis of the causes and magnitudes of overpressure is, therefore a special and complex study of material and energy balances in a process system. 

The first essential step in the design of a fume control system and selection of gas-cleaning equipment is the characterization of the fume emission source. Design procedures which can be used for new and existing industrial plants follow. The characterization of fume emission sources includes parameters such as plume flow rates (mVs), plume geometry (m), source heat flux (J/s), physical and chemical characteristics of particulates, fume loadings (mg/m ), etc. 

Automation CL measurements can be performed very rapidly and with minimal human participation if the flow system is carefully designed. Several reagents can be added to the sample if multiple flow lines are used and at predetermined times to fulfill the best condition for maximum CL sensitivity. Introduction of special devices into the flow line, which allow procedures otherwise time-consuming such as solvent extraction or ion exchange, improve substantially the sensitivity and selectivity of the technique. 

In these systems, the total collection efficiencies of the dry product are 85 per cent for the drying vessel, 90 per cent for the cyclone collector and 98 per cent for the scrubber-condenser. The net efficiency of the system may be as high as 99.97 per cent if the scrubber effluent is considered as product. All the runs are based on 1.25 kg/s product and 0.75 kg/s evaporation at an elevation of 300 m above sea level. The total air flow is measured at the outlet before the stream is split into the recycle and bleed portions and, for such flows, the design of suitable fans is outlined by Jorgensen164 . The calculations outlined here may be confirmed by the use of psychometric charts, and this procedure has been considered in some detail by Cook and Demount165. ... 

Considerable interest has been generated in turbulence promoters for both RO and UF. Equations 4 and 5 show considerable improvements in the mass-transfer coefficient when operating UF in turbulent flow. Of course the penalty in pressure drop incurred in a turbulent flow system is much higher than in laminar flow. Another way to increase the mass-transfer is by introducing turbulence promoters in laminar flow. This procedure is practiced extensively in enhanced heat-exchanger design and is now exploited in membrane hardware design. 

If liquid flows are extremely small, and the system is nonfoaming, circular or envelope downcomers may be installed within the area subtended by a segmental weir (1,10). These should have twice the area calculated using the normal design procedure. 

The procedure to foUow in designing PAC-activated sludge systems for nitrification involves a modification to those for complete mix or conventional plug flow systems (39) in order to account for the effects of the addition of PAC. According to major suppliers of the technology (38 2), most PAC process systems are designed at MUSS concentrations of approx 15,000 mg/L. The mixed liquor is composed of volatile activated carbon, biomass, nonvolatile PAC ash, biomass decay components, and influent inert material. The... 

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