Solid material comminution or disintegration – Apparatus – With separation or classification of material
Patent
1982-05-20
1985-04-09
Scherbel, David A.
Solid material comminution or disintegration
Apparatus
With separation or classification of material
241 74, 209683, 209297, B02C 1706
Patent
active
045096970
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention is directed to a rotary drum screen for waste material and its method of operation, particularly for performing a pre-crushing function.
BACKGROUND ART
In raw and combustible material recovery from waste material using a processing line in a rotary screen drum, it is a known procedure to sift the waste material and to feed most of the unsifted material from the rotary screen drum into a milling unit. The milled material is then recombined with the sifted material.
DISCLOSURE OF THE INVENTION
The objective of the invention is to produce a rotary drum screen which, as far as practicable, also performs a pre-crushing function which reduces the amount of unsifted material. One of the purposes of this is to reduce the load on the mill whose operation consumes large amounts of energy. Another purpose is to primarily reduce the glass content of the mill discharge, because it is relatively costly to remove small glass shards as small as splinters from the waste stream during further processing. This objective is solved by one or preferably more baffles distributed along the length of the rotary drum screen which prevent the waste material from passing too quickly through the rotary drum screen and cause the waste material to repeatedly fall from the upper to the lower part of the drum, as well as impact plates running circumferentially around the drum in the baffle zones. In addition the rotary drum screen has a diameter adequate to impart the breakable waste material components sufficient speed when they fall from the upper to the lower part of the drum as it rotates to break the same when they impact the walls of the drum and particularly when they hit the impact plates. Drum diameters of 2 m to 4 m are generally adequate in this regard; approximately 3 m has been shown to be suitable for domestic waste.
The waste material can be brought to the upper part of the rotary sieve as it turns by carrier plates which are axially attached. However, since waste residue builds up relatively easily on these plates, which impedes further refuse transport, it is preferable to rotate the rotary drum screen at a relatively rapid speed. It has been found the drum rotation speeds at which the centrifugal acceleration at the drum surface is 50%-70% of the acceleration due to gravity, particularly in combination with the subsequently discussed polygonal cross section of the drum, produce a very steep refuse profile in the rotary drum screen and thus the greatest possible fall heights for the refuse in the drum. With the drum diameter of 3 m mentioned above the rotary drum screen can be driven, for example, at 15 R.P.M.
The erect impact plates break up brittle material such as pottery and bottles, however they should also be able to tear up trash bags and sacks which are generally made of plastic film. Therefore, the upper edge has preferable a saw tooth contour. By increasing the height of this saw tooth contour in the direction of the drum axis so that the lower part extends ahead in the direction of rotation, the forward conveying action of the impact plates is kept small so that the flanks of the teeth do not accumulate refuse residue.
The profile of the waste material in the drum should be as steep as possible so that the particulate matter is kept primarily in the state of free fall. To this end, the cross section of the drum casing is, along with the drum r.p.m. described above, of particular importance. It should be in the form of a polygon, particularly an octogon.
The baffles in the rotary drum screen should leave an opening large enough for the refuse to pass through without being overly expensive to construct but which disrupts the flow of the waste material within the casing. They can also serve as transverse supports for the drum casing. For this purpose they are made up of four rectangular plates, according to a further refinement of the invention, whose one side is equal to the octagon side (S) to which it is attached, and whose other side is equal to the cathetus length
REFERENCES:
patent: 2265642 (1941-12-01), Hamachek
patent: 3074657 (1963-01-01), Bridgewater
patent: 3224839 (1965-12-01), Pierson
patent: 4043901 (1977-08-01), Gauld
patent: 4154407 (1979-05-01), Famort
Riemann Hanns-Helmut
Skaletz Heinz
Sonnenschein Hans
Foster Glenn
Mannesmann Veba Umwelttechnik GmbH
Scherbel David A.
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