Feed volume

A single wet dmm separator is typically used in plants where the feed soHds are in the 10—15% range. Extremely dilute feeds make magnetic recovery more difficult and feed volume should be reduced by a factor of 0.5—0.75 for such dilute feed. Por soHds in the 20—25% range, either single-dmm 914-mm units or double-dmm 762-mm units are recommended. Above 25% soHds, 914 mm dia double dmms are recommended. 

Magnetic Content of Feed Solids. The magnetic content of the soHds is typically >60%. Conventional selection procedures can be used in such cases. When the magnetic content of the soHds falls below 60% the feed volume should be reduced and multidmm separators considered in order to maintain higher magnetic recovery. 

Probably Fl is a function of particle Reynolds number and concentration, but Fig. 6-33 gives Durand s empirical correlation for Fl as a function of particle diameter and the input, feed volume fraction solids, Cs = QsKQs + Ql)- The form of Eq. (6-145) may be derived from turbulence theory, as shown by Davies (Chem. Eng. Sci., 42, 1667-1670 [1987]). 

Simple, but gives relatively inefficient separation. Used for primary dewatering where the separations involve large feed volumes, and underflow drainage is not critical. 

Minimum total reflux (lbs or mols/hr) corresponding to given total feed will be greater than if only the actual total mols of heavy and light key components were present. Reflux need will be less than if the actual total mols of feed were present, but composed only of light and heavy keys. The more closely non-keyed components are clustered to volatilities of the keys, the nearer are reflux needs to that calculated for the binary and total feed volume. 

Flow Flux, Permeability, Conversion The productivity of a membrane module is described by its flux J = volumetric permeate flow rate/membrane area with units of volume per area per time. Relatively high flux rates imply that relatively small membrane areas are required. The permeate volume is usually greater than the feed volume for a given process. Flux is also the magnitude of the normal flow velocity with units of distance per time. 

Fluxes scale directly and volumes scSe proportionately with the feed volume. A safety factor will be built into the scale-up design so that process times will not be the same. 

The system area A needed for batch or fed-batch operation can be calculated by using the formulas in Table 20-19 for production rates V(/t based on feed volume Vq and average fluxes during process steps. The final retentate batch volume Vr = Vq/X or permeate batch volume Vp = Vo(l — l/X + N/X) can be used to restate the production rate on other bases. Although experience can be used to estimate solute passage and process fluxes, they should be determined e3q)erimentally for each application. 

Basic Principles of Operation Gas-separation literature often uses nomenclature derived from distillation, a practice that will generally be followed here. L is the molar feed rate, V is the molar permeate rate, R is the molar residue (L — V). Mole fractions of components i, j, in the feed-residue phase will be Xj, Xj. .. and in the permeate phase yi,yj.... Stage cut, 0, is permeate volume/feed volume, or V/L. 

Membrane Ultrafiltration Membrane ultrafiltration is often one of the favored unit operations used for the isolation and concentration of biomolecules because they can be easily scaled up to process large feed volumes at low costs. Toward the end of an ultrafiltration operation, additional water or buffer is added to facilitate the passage of... 

Fig. 12.9 Two-stage acid Thorex process for highly irradiated fuels. Numbers in the frames indicate stage number, whereas numbers on the lines indicate flow volumes relative to the feed volume (DOD and FP are dodecane and hssion products). 

The surface of the membrane is also critical in determining membrane efficacy, with more hydrophilic surfaces enabling water to permeate easily. As the surface becomes more and more hydrophobic, it also becomes less permeable to water molecules. With pathogens, studies have shown that a consideration of the volumes of water to be treated (e.g., liters per hour), concentration ratio, or volume of the permeate, which is typically 75-95% of the feed volume and the expected permeate flux (e.g., liters per hour), a reliable prediction about the efficacy of membranes can be made. Similar parameterization needs to be done to determine what works best when it comes to rejecting PPCPs since parameters that are effective for rejecting pathogens may not necessarily apply wholesale to PPCPs. 

Reverse osmosis Relies on proven technology 400,000 150,000 Generates a concentrated stream, 10 to 25% of the feed volume, which must be treated further by secondary treatment and high cost. 

Produces minimal waste (waste volumes < 1 % of the feed volume are possible). 

Characteristics of feedstock quality, recycle ratio, and drum pressure affect the coke yield. Highly aromatic feedstock contains more carbon per feed volume and typically produces a high coke yield. Heavy coker gas oil can be recycled back into the coker feedstock to help improve the coke yield. Also, increasing the coking drum pressure tends to increase the coke yield. Typically, a higher coke yield results in a reduced liquid product yield. 

For any given chromatographic system, there is a limiting charge that can be placed on a column before the resolution is impaired. Loss of resolution from column overload can arise from two causes, either excessive sample feed volume or excessive sample mass. The theory of moderate sample volume overload has already been considered in the applications of the Plate Theory. The theory of excessive sample volume overload will now be discussed. 

Recommended Feed Volumes. Both feed volume and magnetic solids discharge rate should be balanced in selecting media recovery drum size. The feed rates typically recommended for single and double wet drum separators depend on drum diameter. For a 762 mm dia single drum, the recommended feed rate is 50—55 m3/(hrn) for either a 914 mm dia single drum or a 762 mm dia double drum, 55—70 m3/(h-m) for a 914 mm dia double drum, 70—95 m3/(h-m). 

In this relationship, Vi is the initial (feed) volume of the gas. This is the case of Levenspiel s simplification where the volume of the reacting system varies linearly with conversion (Levenspiel, 1972). The last equation shows that even if we have a change in moles (sR / 0), if the conversion of the limiting reactant is veiy low, the volume of the reaction mixture could be taken as constant and eR is not involved in the solutions of the models (since eRjcA can be taken as approximately zero). 

End of Pipe" Treatment - It is possible to use reverse osmosis and ultrafiltration to concentrate or "dewater" mixed effluent streams in order to reduce the hydraulic loading to down stream treatment processes. Typically, at least 90% of the feed volume can be purified and often returned to the process, with the salts concentrated in the remaining 10%. 

One expects this system to have the efficiency of a single column arrangement. However, optimum efficiencies are not realized because of the column-to-column variations and the tendency to use excess feed volumes. 

Note the physical size differences for the cross-sectional area Ac and the liquid and gas feed volumes L and V in this example when compared to the ones of Figure 6.28. Our original quest to achieve Xe = 3 as stipulated in the above call turns out to be unreasonable. The program recognizes this and gives us the height of the tower needed for achieving the maximally possible Xe = 1.93056 instead on the title line. 

For treating water containing VOCs with separation factors of more than 500, for which concentration polarization is a serious problem, feed-and-bleed systems similar to those described in the chapter on ultrafiltration can be used. For small feed volumes a batch process as illustrated in Figure 9.16 is more suitable. In a batch system, feed solution is accumulated in a surge tank. A portion of this solution is then transferred to the feed tank and circulated at high velocity through the pervaporation modules until the VOC concentration reaches the desired level. At this time, the treated water is removed from the feed tank, the tank is loaded with a new batch of untreated solution, and the cycle is repeated. 

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