The Pan Filter

The twisting rubber hoses or o ringed elbows which connect the rotating pan necks with pipe and the wear plate to the face of the stationary valve The condition of the high impact nozzles mounted on the cloth wash manifold and, for wet cake discharge, the sluicing manifold The support rollers which take the vertical load of the entire machine and the horizontal thrust rolls that maintain the rotating frame concentric The toothed rim and sprocket which drives the pan filter... 

Figure 18.26 shows three pan filters made of mild steel with a filtration area of 62 m (pan diameter 9.2 m each). The pan filters shown are equipped with two cake wash boxes for counter current cake washing. This pan filter is executed with inclined pan bottom for discharging the filtrate (the filter deck representing the... 

Pan Filter with Tilting Cells, by Bird-Prayon The pan filter with tilting cells (Figure 18.28) has moveable filter cells. These are rotated 180" about an axis radial to the filter on completion of the filtration cycle. Then a hard jolt on the cell together with interruption of the vacuum supply ensures a complete discharge of the filter cake. The filter cloth thus becoming accessible, it can be thoroughly cleaned, which is not a the case on other pan filters. More on this in [18] and [19]. 

Tipping pan and horizontal filters are also used for leaching the modus operand of the Rotocel extractor resembles that of a tipping pan filter, although the details of its design differ slightly. 

Tipping Pan Filter. This is a nutsche filter with a small filtrate chamber, in the form of a pan built so that it can be tipped upside down to discharge the cake. A separate vessel is used to receive the filtrate this allows, segregation of the mother and wash Hquor if necessary. 

A variation on this type of filter is the double tipping pan filter, which is a semicontinuous type consisting of two rectangular pans fitted with a filter cloth and pivoted about a horizontal axis. Slurry is first fed onto one pan, which is turned over for cake discharge at the end of the cycle. The second pan is used for filtration while the first is being discharged. 

In general, pan filters are selected for freely filtering soHds and thick filter cakes. Cake washing can be introduced easily. Most appHcations are in the mining and metallurgical industries for small-scale batch filtration. 

Horizontal Rotating Pan Filters. These filters (Fig. 10) represent a further development of the tipping pan filter for continuous operation. They consist of a circular pan rotating around the central filter valve. The pan is divided into wedge-shaped sections covered with the filter medium. Vacuum is appHed from below. Each section is provided with a drainage pipe which connects to a rotary filter valve of the same type as in dmm filters. 

The Tilting Pan Filter is predominantly employed in the phosphoric acid industry and, to some extent, in the washing of phosphate rock. There was a traditional rivalry over the years between the Pan and Belt Filter which now, owing to the substantial progress in rubber technology, swings in the favor of the later. The operation of Tilting Pan Filters is based on a series of horizontal independent... 

The cycle of a Tilting Pan Filter that includes three counter-current washing stages consists of the following zones ... 

A structure that rotates over rollers, supports the pans and is fitted with a toothed rim that drives the filter. 

For distributors of any design, including the PAN, it is important to filter the feed or reflux liquid entering tlie distributor to reduce the possibilities of plugging of tlic orifice holes. Otherwise, the landom plugging will cause non-uniform distribution onto the packing below. It is important to avoid leakage around the risers because this can destroy the liquid distiibution pattern [131]. 

Experiment.—On a small hand balance, having two sheets of paper counterpoised in the pans, weigh out equal quantities (about 0-5 g.) of quinone and quinol dissolve the two substances separately in warm water and mix the solutions. Magnificent green needles of quinhydrone crystallise almost at once. After some time collect them at the pump, wash with water, and dry between filter papers over calcium chloride in a non-evacuated desiccator. Boil a few of the crystals with water and smell the vapours. 

Equipment has been developed to overcome the disadvantages of manual discharge of solids from the simple batch pan type vacuum filter, and such equipment incorporates scrapers or rakes for the removal of the solids. Other pan type vacuum filters are arranged so that the pan is tipped over, when the solids are discharged, either under their own weight or sometimes with the assistance of blow-back air admitted to the underside of the filter cloth when the pan is inverted. 

Top-feed drum filters are used for the treatment of very fast settling solids that cannot easily be kept in suspension. A drum filter may be preferable, rather than a horizontal pan or similar filter, because of its low cost, simplicity and reliability, and because of the relative ease with which it can be fitted with appropriate accessory features. A top feed drum filter incorporates multi-compartments, drainlines and a rotary valve identical to those in a conventional drum filter. The feed slurry is introduced at, or just before, top dead centre, and the cake is discharged from 90° to 180° from the feed point. The feed slurry can be distributed across the drum by sprays or a weir box, or it may be contained within a 3-sided head-box which is sealed against the moving drum at each end and across the back on the ascending filter surface. For materials which do not cake together sufficiently to be self-supporting on the drum surface, a hopper-type top feed filter may... 

Deoiled water leaves the unit via a drawoff pan leading to the outlet piping. Large drops of coalesced oil rise past the water draw-off pan, into the separation section where it accumulates, and is later drawn off Deep bed downflow separator. Another approach to oil removal using lose media is the downflow filter Oily water enters near the top of the vessel and flows downward through the coalescing media which consists of three... 

The measurement of FPN from the N03 recovered from a backup Teflon-nylon or nylon filter with the ADM is subject to some of the same potential sources of error as with the DDM. No loss of FPN passing through the annular denuder is expected on the basis of particle-loss measurements (55). Although HONO is efficiently removed ahead of the filter or filters, nearly all of the PAN would reach the nylon filter. Retention of PAN on nylon filters has been reported to be insignificant. Thus, relatively little error in FPN is expected with the ADM and CO -glycerol coated denuders. 

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