Solid material comminution or disintegration – Apparatus – With separation or classification of material
Patent
1992-08-24
1994-01-11
Watts, Douglas D.
Solid material comminution or disintegration
Apparatus
With separation or classification of material
241 19, 241225, B02C 2308, B07B 7083
Patent
active
052773701
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for comminuting and classifying bulk materials, the device including a vertical impact mill equipped with an associated material charging device, a screening device charged with air, a finished material discharging device as well as a conveying device for returning the insufficiently comminuted fraction of the bulk material into the comminution region.
German Patent 576,895 discloses a mill charging device that includes a comminuting device equipped with a centrifuging plate that is surrounded by an impact wall. Below the plane of the impact ring, a blower wheel is provided that is driven together with the impact ring and generates a stream of air that crosses the stream of material dropping down from the impact ring. The fine material fraction is transported to a cyclone by the rising air where the fine fraction is discharged at the bottom and the exhaust air is made available again to the blower. The coarse fraction is fed to a grinding system provided below the vertical impact mill. The drawbacks of this device are essentially that the screening air is able to also penetrate into the region of the vertical impact mill which might, under certain circumstances, create undesirable flow conditions that could adversely affect the comminution process. Additionally, a further grinding device must be provided in order to further comminute the insufficiently comminuted bulk material fraction. This measure makes the device more complicated and also more expensive.
European Patent 118,782 discloses a comminuting apparatus and a screening device which are each equipped with a vertical shaft, with the comminuting device being provided in the lower region of the system and being charged with material by means of a worm-shaped feeder. The material introduced through the worm encounters an upwardly directed stream of air which is supplied below the comminuting apparatus and is intended to bring the material into the region of the comminuting device formed by at least one rotating impeller wheel. The stream of air should then carry the comminuted and any not yet sufficiently comminuted bulk material further upward into the region of a rotating screening device where a further classification takes place. The fine fraction is discharged above the screening device through a collecting pipe while coarser material, on the one hand, is reintroduced into the feeder and, on the other hand, is to be conducted to the comminuting device through corresponding recesses outside of the air stream. Between the comminuting device and the screening device, a further gas intake is provided and a type of perforated metal sheet is disposed above the gas conduit through which the gas entering from the gas intake flows upwardly. The drawback of such a structure is that a relatively large amount of air is required to ensure an upwardly directed flow over the entire interior cross section of the comminuting device. The vane or vanes provided with striking tools produces a flow component in the circumferential direction which must be overcome by the upwardly directed stream of air. This is particularly applicable for a stream of air charged with the coarse fraction. The same also applies for the second externally supplied gas source whose direction of flow is essentially radial and must first be converted into an axial component. In addition to the relatively complicated structure of the device, flow conditions are disclosed here which are hardly realizable in practice and thus make the overall operation of the system questionable.
Applicant's German Patent Application P 3,844,178.0, now published as DE-OS 3844178A1 on Jul. 5th, 1990, relates to a method and a device for comminuting bulk materials in which the material is charged vertically from the top into a comminuting device and is discharged subsequent to the comminution process. The material is introduced into a first acceleration device and is conducted by it onto a first material pile, with the fine-grained comminution products from this first comminutio
REFERENCES:
patent: 2350737 (1944-06-01), Eiben
patent: 5114131 (1992-05-01), Strasser et al.
patent: 5203511 (1993-04-01), Ohdush et al.
patent: 5215262 (1993-06-01), Binder
O&K Orenstein & Koppel AG
Watts Douglas D.
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