Enclosed agitated vacuum filters

These filters, often called mechanized Nutsches , are circular vessels provided with a cover, through which passes a shaft carrying a stirrer. The stirrer can sweep the whole area of the filter cake and it can be lowered or raised vertically as required. During the filtration process the stirrer is in the top position, if necessary in motion in order to prevent the formation of an 

The filter cake can then be washed either by displacement or by reslurrying. Reslurrying is easily accomplished using the stirring action of the rotor blades when the rotor is lowered into the cake. The cake may also be dried in situ by the passage of hot air through it, or may be steam distilled for the recovery of solvent. 

For discharge of the cake, a discharge door is provided at the edge and the cake is moved by the rotor towards the door, the stirrer blades being gradually lowered onto the surface so that a small depth of solids is scraped away. Alternatively, the cake may be reslurried and pumped away. 

The enclosed agitated filters are especially useful when volatile solvents are in use, or when the solvent gives off toxic vapour or fumes. Another major advantage is that their operation does not require any manual labour. 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 surfaces exposed to attack protected by lead, tile or mbber lining, or by coating or spraying with 

Applications are mainly in the chemical industry for the recovery of solvents. 

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The pressure versions of the nutsche filter, which falls into this category, are either simple pressurized filter boxes or more sophisticated agitated nutsches, much the same in design as the enclosed agitated vacuum filters described eadier. These are extremely versatile, batch-operated filters, used in many industries, eg, agrochemistry, pharmaceuticals, or dyestuff production. 

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. 

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