Vertical filter dryer

FIGURE 21.10 Vertical filter dryer. (Courtesy of De Dietrich Process Systems, Inc., Charlotte, NC.)... 

Typical throughput of an 8 m vertical filter dryer is 1250 kg/ batch at a cake depth of about 0.4 m and an agitator speed of 6.5 rpm. Clearly, these depend on the feedstock. 

Figure 29.3 Vertical filter-dryer. (From Kudra and Mujumdar, 1995.)...

Vertical Agitated Dryers This classification includes vertical pan dryers, filter dryers, and spherical and conical dryers. 

Filter dryer The basic Nutsche filter dryer is like a vertical pan dryer, but with the bottom heated plate replaced by a filter plate. Hence, a slurry can be fed in and filtered, and the wet cake dried in situ. These units are especially popular in the pharmaceutical industry, as containment is good and a difficult wet solids transfer operation is eliminated by carrying out both filtration and drying in the same vessel. Drying times tend to be longer than for vertical pan dryers as the bottom plate is no longer heatra. Some types (e.g., Mitchell Thermovac,... 

Filter Dryers Basically this is a Nutsche filter (Sec. 18, Liquid-Solid Operations and Equipment ) followed by a batch dryer, usually of vertical pan type (see Batch Agitated and Rotating Dryers section). They are popular in the pharmaceutical and specialty chemicals industries as two unit operations are performed in the same piece of equipment without intermediate solids transfer, and containment is good. 

Pressure filters or filter presses are commonly of the batch type, and are characterized by smaller floor area, high filtration rates, and lower capital cost. Dryer cakes are produced. The chemical industry uses these filters more widely than mineral processing industries, mainly because of its batch operation. The most common types of pressure filters used are the plate and frame presses. These comprise a series of vertical, alternating parallel frames and plates, with the filter cloth being held against the plate and the formation of cake occurring in the hollow frame. 

Spray dryers are normally used for liquid and dilute slurry feeds, but can be designed to handle any material that can be pumped. The material to be dried is atomised in a nozzle, or by a disc-type atomiser, positioned at the top of a vertical cylindrical vessel. Hot air flows up the vessel (in some designs downward) and conveys and dries the droplets. The liquid vaporises rapidly from the droplet surface and open, porous particles are formed. The dried particles are removed in a cyclone separator or bag filter. 

Vertical Vacuum Pan Dryers. The agitated vertical dryer (Fig. 3.) has been designed for drying many different products which may come from centrifuges or filters. Generally, the body is formed by a vertical cylindrical casing with a flat bottom flanged to the top cover head. The unit is fully heated by an outside half-pipe jacket welded on the cylindrical wall, the bottom and the top head. 

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