Filter handling

Figure 7.20. String discharge mechanism on a filter handling silica gel...

Finally, the concentrations of all constituents were summated and compared with the gravimetric ally measured mass to establish the unaccounted mass denoted unknown. The assumption here is that the various data sets accurately describe the PM characteristics. The filtration devices employed at the sites were all equivalent to the reference method. However, corresponding studies use different procedures with respect to filter handling, data treatment and selection, analytical techniques, etc. In addition, temporal variation, local site characteristics, artefacts like volatilisation and particle-bound water as well as varying distances from major sources will affect... 

The need to process large numbers of samples at sea and in the laboratory required substantial improvement over previous filter-handling techniques. Furthermore, techniques had to be developed to allow fresh subsamples to be taken from the filters for organic analyses while allowing the remaining sample to be processed in normal fashion (5). All filter handling was performed with plastic or stainless steel tweezers and polyethylene gloves. 

A bypass circuit allows a large portion of the total pump flow to bypass the filter. In such a circuit, the filter handles only the amount of flow necessary to maintain the contamination level required by the system components. This lower flow specification allows the use of a smaller, less costly filter, but can still provide maximum component life. In the bypass circuit, the ingestion point can be after the work components, but before the bypass line, or at the reservoir. 

Whatman No. i filter-paper, and handled as little and as cleanly as possible. 

The technique of the filtration of hot solutions has already been described in Section 11,28. The filtration of cold solutions will now be considered this operation is usually carried out when it is desired to separate a crystalline solid from the mother liquor in which it is suspended. When substantial quantities of a solid are to be handled, a Buchner funnel of convenient size is employed. The ordinary Buchner fimnel (Fig. 11,1, 7, a) consists of a cylindrical porcelain funnel carrying a fixed, flat, perforated porcelain plate. It is fitted by means of a rubber stopper or a good cork into the neck of a thick-walled filtering flask (also termed filter flask, Buchner flask or suction flask) (Fig. 11,1, 7, c), which is connected by means of thick-walled rubber tubing (rubber pressure tubing) to a similar flask or safety bottle, and the latter is attached by rubber pressure tubing to a filter pump the safety bottle or trap is essential since a sudden fall in water pressure may result in the water sucking back. The use of suction renders rapid filtration possihle... 

Reflux 0-5 g. of the amine with 5 ml. of 90 per cent, formic acid (CAUTION in handling) for 10 minutes, and dilute the hot solution with 10 ml. of cold water. Cool in ice and, in some cases, saturate with salt if the derivative does not separate immediately. Filter, wash with cold water, and recrystallise from water, alcohol or light petroleum (b.p. 60-80°). 

The presence of crimp in the tow is necessary to ensure that the tow can be packaged, processed, and handled easily and to impart bulk to the finished filter. To achieve the latter in the production of the filters, it is necessary to open the tow band (Fig. 12b) to the desired bulk so that the fibers completely fill the paper wrap without voids and soft spots. 

Pressure filters can treat feeds with concentrations up to and in excess of 10% sohds by weight and having large proportions of difficult-to-handle fine particles. Typically, slurries in which the sohd particles contain 10% greater than 10 ]lni may require pressure filtration, but increasing the proportion greater than 10 ]lni may make vacuum filtration possible. The range of typical filtration velocities in pressure filters is from 0.025 to 5 m/h and dry sohds rates from 25 to 250 kg nY/h. The use of pressure filters may also in some cases, such as in filtration of coal flotation concentrates, eliminate the need for flocculation. 

The primary advantages of this filter are its simple design and low maintenance costs. The main disadvantage is the difficulty of handling very fast-filtering materials on a large scale. Areas up to 93 m are available. 

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