Drying and gas or vapor contact with solids – Apparatus – Rotary drums or receptacles
Patent
1994-01-13
1997-05-13
Bennett, Henry A.
Drying and gas or vapor contact with solids
Apparatus
Rotary drums or receptacles
34135, 34137, 432105, F26B 1102
Patent
active
056281269
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of drying and to drying apparatus, in particular for drying wet materials in suspension, slurry or sludge form, for example sewage, industrial effluent and the like and also certain granular materials. The invention may also be applied to the cooling of materials.
According to the invention, apparatus for drying wet materials comprises a drum mounted for revolution about a substantially horizontal axis, the drum having inlet means for material to be dried and outlet means for dried material, characterised in that the drum includes inner deflecting wall means defining a spiral pathway having a plurality of coils between the said inlet and outlet means with concentric inner and outer oppositely-handed spirals interconnected at their ends, the drum in use containing a charge of a solid heat exchange and pulverising medium in particulate form, the drum also including means to heat the said medium and means to vent vapours from within.
The invention also includes a method for drying a wet material, the method comprising introducing the material into a revolvable drum having a substantially horizontal axis of revolution and containing a heated solid heat exchange and pulverising medium in particulate form and revolving the drum to mix the material and the heat exchange medium, the drum having inner deflecting wall means defining a spiral pathway having a plurality of coils with concentric inner and outer oppositely-handed spirals interconnected at their ends between the said inlet and outlet means, whereby the material and heat exchange medium are contained within the pathway and propelled axially of the drum while drying takes place, vapours being vented from within the drum, separating the dried and pulverised material from the heat exchange and pulverising medium and removing the said dried and pulverised material from the drum and recirculating the pulverising medium.
Throughout the remainder of this specification, including the claims, the invention will be described with reference to the drying of a wet material. However, it is to be understood that the invention may be equally applicable to cooling, with or without drying, and accordingly any references to "heating", "drying", "dried materials" and so on are to be taken as including cooling and cooled material as the context requires. In place of heated air as a heating means, a cooled gas, sublimed carbon dioxide or the gas formed from the boiling of a cryogenic liquid may be used as cooling means.
In the apparatus according to the invention, the inner deflecting wall means is preferably fixed in relation to the drum outer wall whereby the inner surface of the said wall forms the floor of the pathway. In use, the contents of the drum are caused by gravity, on rotation of the drum, to remain in the lower portion of each coil of the spiral pathway and thereby to traverse the length of the drum as rotation continues. The heat exchange and pulverising medium is preferably recirculated from the outlet to the inlet end of the drum with re-heating, following separation of the dried material, whereby the process operates continuously with each successive coil containing a discrete charge of heat exchange and pulverising medium and material undergoing drying.
The interior of the drum comprises concentric inner and outer oppositely-handed spirals in communication at their ends, whereby on rotation of the drum the charge re-circulates through the spirals, material to be dried being introduced through the inlet means at one end and dried material being discharged through the outlet means at the other end, the material or a major part thereof making a single pass through one of the spirals, preferably the outer spiral. Conveniently, the heat exchange and pulverising medium is heated and re-heated during its return passage through the other one of the spirals, preferably the inner spiral, between the outlet and inlet means for dried material and for material to be dried, respectively. At the inlet means end, a discrete charge of medi
REFERENCES:
patent: 2872386 (1959-02-01), Aspegren
patent: 4094633 (1978-06-01), Peterson et al.
patent: 4474553 (1984-10-01), Takahashi
Bennett Henry A.
Dorman Ira S.
North Stephen Manton
Ohri Siddharth
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