Solid material comminution or disintegration – Processes – With application of fluid or lubricant material
Patent
1988-12-27
1990-03-20
Eley, Timothy V.
Solid material comminution or disintegration
Processes
With application of fluid or lubricant material
241 69, 241 84, 241173, B02C 1710, B02C 1716
Patent
active
049094483
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method of granulating material, such as lime powder or the like, use being made of a counterflow mixing machine with scraping and mixing means, which is rotated about a vertical axis.
Methods of granulating are known in which either rotary discs or a screw conveyor system (an edge mill-principle) are used. These known methods have several drawbacks. Thus, the rotary disc principle usually entails expensive plants, and furthermore the granulating method is inexpedient as the granulates proper obtain a somewhat layered structure making their shape unstable. Consequently, the granulates tend to break or disintegrate.
In particular, it is the inclined position of the disc which makes the manufacture of a rotary disc expensive, the inclined position causing an asymmetric distribution of the goods around the axis of rotation, which calls for large and strong bearings and shafts to absorb the heavy forces.
According to the edge mill principle the raw material is subjected to moistening in a screw conveyor, grinding in a moistening edge mill, and typically passes through a vibrating screen or, via a so-called "mincing machine"-principle, through a plate with holes adapted for that purpose, whereby the kneaded material is discharged in a number of lengths and is chopped into suitable pieces. This manufacturing process also entails rather heavy costs, and additionally it necessitates extensive pre-and aftertreatment of the raw material in view of the requisite moistening and kneading prior to chopping off, the chopped off material parts subsequently having to be subjected to a certain drying. By this manufacturing procedure are obtained granulates of non-ball shaped nature, which is inexpedient when exposing the granulates to load, e.g. by storage or transportation, which easily entails a certain waste of material.
Furthermore, it is also impossible to produce small granulates of e.g. 2 mm, as the minimum size lies within the range 8-10 mm. A machine operating according to the edge mill principle is also very expensive to make, as the rollers of the edge mill have to be very heavy and the plate with holes through which the goods is pressed must have a very sturdy construction, e.g. a thickness of 50-100 mm. Additionally, the boring proper of the many holes in the thick plate is extremely work-consuming.
It is a common feature of both methods of granulating that their capacity is rather low, which of course adds to the cost of the finished product.
Use of stones in a rotating mixing vessel is known in connection with the so-called ball mills; however, their object being, as opposed to the object of the present invention, being the to obtain comminution of materials.
It is the object of the present invention in connection with granulation of particle shaped material, such as lime and the like, to devise a method adapted for that purpose, which in combination with simple plant facilities makes possible the manufacture of a stable granulate and additionally involves negligent waste, simultaneously with the operating and initial costs involved being low.
The object is achieved by a method of granulation, as stated in the characterizing portion of claim 1. The counterflow mixer used has, as opposed to the said ball mills, a vertical axis of rotation essentially causing the "mixing stones" constantly to collect at the vessel bottom in stead of being whirled about in the vessel as is the case in the ball mill process, the result here being comminution.
However, by the method according to the invention it is obtained in stead that the raw material (lime, clay and the like) sticks to the stones because of its natural or added moisture content. After a while the material layer thus built by rotary mixing will be dehydrated/dried, essentially thereby instantly stopping adhesion to the mixing stones, and the material peels off. The material collects at the bottom and is scraped out as a finished granulate through a grate situated in the vessel bottom.
It is evident that the granulation process may compri
REFERENCES:
patent: 3329348 (1967-07-01), Pootmans
patent: 3591362 (1971-07-01), Benjamine
patent: 3612419 (1971-10-01), Szequari
patent: 4249903 (1981-02-01), Smolka et al.
patent: 4811909 (1989-03-01), Inoki
Lip Ejnar
Lip Peter
Eley Timothy V.
F. L. Smidth & Co. A/S
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