Significance filters

FIGURE 10.12 Time-domain smoothing of the noisy data in Figure 10.1 with the impulse response function of Figure 10.7, processed from left to right in this spectrum. The true signal is shown as a dotted line. Note the significant filter lag in this example. 

Fibrous structural media containing GAC are used extensively as filters. Compared to a granular bed such as GAC, a non-woven fibrous structure minimizes channeling, allows significant filter design variations, and can be manufactured by low cost paper manufacture methods. 

Correlation coefficients were calculated between moisture determined by oven drying and moisture estimated by the InfraAlyzer 400 (R =. 97, tot. 0.99). Averaged SECs of 0.12% are acceptable (Table 20.7). The results obtained for the prediction sets are comparable with those of the calibration sets. The calibration procedure resulted in three to six filters giving significant information including the most significant filter for moisture absorption at 1940 nm. 

Again, we consider boreholes with significant filter cake formation due to non-lossy muds. When this is the case, we solve Equation 14-21 for porosity,... 

Figure 4.12 Spherulites of poly( 1-propylene oxide) observed through crossed Polaroid filters by optical microscopy. See text for significance of Maltese cross and banding in these images. [From J. H. MaGill, Treatise on Materials Science and Technology, Vol. lOA, J. M. Schultz (Ed.), Academic, New York, 1977, with permission.]...

Fractional crystallization may be accompHshed on a batch, continuous, or semicontkiuous basis. Oil is chilled continuously while passkig through the unit and is then passed over a continuous belt filter which separates soHd fat from the Hquid oil. The process gives poorer separation compared to solvent fractionation because oils are viscous at crystallization temperatures and are entrained to a significant extent ki the soHd fraction. The Hquid fraction, however, is relatively free of saturated material. 

The predominant cellulose ester fiber is cellulose acetate, a partially acetylated cellulose, also called acetate or secondary acetate. It is widely used in textiles because of its attractive economics, bright color, styling versatiUty, and other favorable aesthetic properties. However, its largest commercial appHcation is as the fibrous material in cigarette filters, where its smoke removal properties and contribution to taste make it the standard for the cigarette industry. Cellulose triacetate fiber, also known as primary cellulose acetate, is an almost completely acetylated cellulose. Although it has fiber properties that are different, and in many ways better than cellulose acetate, it is of lower commercial significance primarily because of environmental considerations in fiber preparation. 

There are, however, two significant drawbacks to horizontal filters, ie, such filters usually require large floor areas, and their capital cost is high. Saving in floor area as well as in installed cost can be made by using a filter with vertical or other nonhorizontal filtration surfaces but at the cost of losing most, if not all, of the advantages of horizontal filters. 

Enclosed agitated filters are useful when volatile solvents are in use or when the solvent gives off toxic vapor or fume. Another significant advantage is that their operation does not require any manual labor. Control can be manual or automatic, usually by timers or by specific measurements of the product. Most filters are made of mild steel, with the exposed surfaces protected by lead, tile, mbber lining, or by coating or spraying with other substances as necessary. Filtration areas up to 10 m are available and the maximum cake thickness is 1 m. Apphcations are mainly in the chemical industry for the recovery of solvents. 

The Sweedand filter, a significant departure from the standard end-opening design, has the cylindrical shell spHt in a horizontal plane into two parts, where the bottom half can be swung open for cake discharge. The upper half is rigidly supported and both the feed and the filtrate piping are fixed to it. 

Another significant disadvantage of the patented process is the two large mnning seals involved in the main body of the filter as the vessel rotates around a stationary central arrangement this seal is another potential source of trouble. This version has Htde chance of commercial success and has been shelved in favor of a more conventional system of stationary vessel (16). 

Addition Point. The flocculant addition point in a continuous system can also have a significant effect on flocculant performance. The turbulence as the flocculant is mixed in and the floes travel toward the point where they enter the thickener or filter causes both the formation and breakup of floes. Usually there is an optimal addition point or points which have to be determined empirically. In cases where the same polymer is being added at two or more points, the relative amounts added at each point may also affect performance. Thus providing multiple addition points in the design of new installations is recommended (56). 

Clarified lime juice, made by mixing juice with filter aid prior to passing through a filter press, is the one clarified citms juice that is a significant article of commerce. The pasteurized bottled juice is popular for drink mixes, punch bases, and fountain drinks (13). 

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