Drying and gas or vapor contact with solids – Apparatus – Gravity flow type
Patent
1984-11-19
1986-05-06
Schwartz, Larry I.
Drying and gas or vapor contact with solids
Apparatus
Gravity flow type
34178, 432108, 432118, F26B 1712
Patent
active
045862702
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a bed thickness levelling device for a cooling column, in which a feed material to be cooled or dried circulates on a plurality of sieve bottoms disposed one above the other and is intermittently transferred onto a respective subjacent sieve bottom.
A cooling column is an apparatus for cooling or drying a granular feed material, in which a plurality of sieve bottoms are mounted for rotation about a common axis within a substantially cylindrical upright housing. Each sieve bottom is divided into a plurality of circle-sector shaped sieve bottom sectors adapted to be tilted about an axis extending radially with respect to the common axis of rotation of the sieve bottom at a predetermined rotational position of the respective sieve bottom for transferring the feed material carried on the respective sieve bottom sector to the subjacent sieve bottom. The feed material to be treated is introduced into the cooling column adjacent the upper end thereof and proceeds along the plurality of sieve bottoms in the described manner to be finally discharged adjacent the lower end of the cooling column. Drying or cooling of the feed material is effected by means of a gas stream entering the cooling column at its lower end and leaving it at its upper end. During its flow through the cooling column, the gas stream passes through the individual sieve bottoms and the feed material carried thereon.
It has been found that a uniform bed thickness of the feed material on the individual sieve bottoms is of considerable importance. Varying bed thicknesses lead to a non-uniform pressure drop over the extent of the bed and thus to non-uniform flow velocities, resulting in a non-uniform heat exchange and thus to non-uniform cooling or drying of the granular feed material. Transfer of the feed material to a subjacent sieve bottom by tilting the sieve bottom sectors of the respective upper sieve bottom results in the formation of mounds of the feed material. A certain equalization is already brought about by a baffle plate located forward of the tilting position of the individual sieve bottom sectors with respect to the direction of rotation of the respective sieve bottom, as already proposed by the present applicant.
It is an object of the present invention to achieve a substantially uniform bed thickness of the feed material on the individual sieve bottoms of a cooling column of the type set forth in the introduction.
This object is attained according to the invention by providing a levelling rod mounted in support means for oscillating movement about a stationary pivot axis and extending substantially transversely of the direction of movement of the feed material.
A levelling rod of the type described permits in a simple manner a uniform distribution, and thus, a uniform bed thickness of the feed material to be treated on the respective sieve bottoms is achieved.
It has been found advantageous to employ a levelling rod in the form of a round bar or a tube section.
It has further been found that during conveyance on the individual sieve bottoms the feed material tends to migrate radially outwards on the respective sieve bottoms with respect to the axis of rotation thereof. In order to counteract this tendency and to thus achieve uniform distribution of the feed material in the radial direction of the sieve bottoms, it has been found advantageous to mount the levelling rod at such an orientation that in its operating position resting on said feed material, the end of the levelling rod facing towards the axis of rotation of the respective sieve bottom is offset relative to the radial direction of the sieve bottom in the direction of rotation thereof. A suitable offset angle of the levelling rod with respect to the radial direction has been found to be about 5.degree. to 8.degree..
Uniformity of the bed thickness in the radial direction may be further promoted by providing a plurality of baffles mounted at spaced locations of the levelling rod, the baffles being preferably in the shape of annul
REFERENCES:
patent: 273767 (1883-03-01), Schroeder
patent: 2000817 (1935-05-01), Bixby
patent: 2949678 (1960-08-01), Anderson
patent: 3256615 (1966-06-01), Denison et al.
patent: 3681855 (1972-08-01), Weisselberg et al.
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