Tipping pan filter

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. 

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. 

Vacuum filters include the nulschc filter, enclosed agitated vacuum fillers, the vacuum leaf filter, the tipping pan filter, horizontal rotating pan filters, horizontal belt vacuum fillers, rotary vacuum drum lilters. and rotary vacuum disk filters. 

There is hardly a human activity, industrial, commercial or domestic, that is not affected by filtration. It is a very widely used process, from the kitchen counter top water filter to the enormous wastewater treatment plants, or from the delicate membrane ultrafilter to the rugged tipping pan filter of a mineral processing works. It has a major processing role in many industries, and all service applications, such as hydraulic control systems, would literally come to a halt without it. 

Tipping pan filters are also available as multi-pan units, with the pans arranged in a horizontal circle, like a wheel, with the spokes of the wheel represented by the filtrate pipe connecting each pan to a central vacuum pipe and filtrate receiver. The pans are now trapezoidally shaped to fit together in the annular filtration zone. 

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These problems do not exist in the horizontal belt filter, of which in the last few years quite a number of very successful machines have been introduced. This filter is basically constructed as an endless belt so it does not have the same dead time factors, is not affected by differences between cake formation and drying time, and in all cases presents a far better washing surface than a rotary filter (see Figure 17.11). If one wishes to take cake washing to the ultimate efficiency then one must consider countercurrent washing, which is virtually only possible on a belt filter or any other type of filter which has a continuous horizontal filter surface such as, for instance, the rotary tipping pan (see Figure 17.12). 

A. Introduction 3B. Strainers 3C. Screens 3D. Nutsche filters 3E. Tipping pan and table filters 3F. Rotary drum filters 3G. Rotary disc filters 3H. Horizontal belt filters Centrifugal filters Pad and panel filters 3K. Bag, pocket and candle filters 3L. Cartridge filters... 

The tipping (tilting) pan filter obviously, and the rotary table filter somewhat less obviously, are developments of the simple batch vacuum filter described in the previous chapter. The single lipping pan is a batch filter, just like the Nutsche, but other versions, including the table filter, are intended to allow more or less continuous operation. 

The rotary table filter is an extension of the multi-pan filter design. The pans are replaced by segments of the annulus, which still rotates around in a circle so that each segment in turn filters and washes. The segments do not tip, however, to discharge the solid, which is instead scraped off the surface of the filter medium by a screw conveyor, over a flexible outer containing wall. 

The Nutsche, tipping pan and table filters are intended only for solids recovery from liquid suspensions. The rotary drum filter is mainly used for that purpose, but has some applications in clarification as well as solids recovery. 

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. 

Once the cycle is completed, the filter cake is discharged via a screw. Where the solids are abrasive, the screw will be fitted with replaceable tip elements. The solids remaining on the filter will be swirled up by a blowback of compressed air and mixed with the newly fed slurry. The rotation speed of the filter pan is generally... 

Feed is loaded into the pan and filtration takes place either by gravity or under vacuum, depending on the design of the unit and the filterability of the solids. Cake washing can be followed by air drying, if required, prior to removal of the cake by tipping the pan to empty out the solids. When the pans are in the inverted position, the filter fabric can then also be washed. 

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