Powder metallurgy processes – Forming articles by uniting randomly associated metal particles – Consolidation of powders
Patent
1995-08-07
1997-09-09
Jordan, Charles T.
Powder metallurgy processes
Forming articles by uniting randomly associated metal particles
Consolidation of powders
75751, 75758, B22F 100
Patent
active
056666381
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a method for making sponge iron briquettes from fine ore with a maximum grain size of less than 2 mm, preferably less than 0.5 mm, wherein hot fine ore is fed to a roller press having two press rolls and is briquetted by opposite briquette pockets of the press rolls in the nip to form sponge iron briquettes.
A single installation is known in the prior art for producing sponge iron briquettes by directly pressing fine ore. To achieve a pleasant appearance of the briquettes of fine ore, the installation is operated with a fixed nip. The briquette seam is here made so thin that the briquettes are discharged from the roller press substantially in isolated form. Subsequently, the briquettes fall into a rotary screening drum where they are then separated from fine ore which was compacted by one of the separating webs between the briquette pockets in the briquetting process, and from fines in dust form. This method has never been very successful in the prior art, since problems have arisen from this method time and again.
It is therefore the object of the present invention to provide an improved method for making sponge iron briquetts from fine ore.
The object is attained according to the invention in that one of the press rolls is operated as a loose roll which is substantially movable in a direction transverse to the roller axis against a supporting force, with the nip adapting to the amount of material fed to the press rolls and the nip having substantially such a mean width that a briquette strip is formed.
Although it is already known in the briquetting of pellets and/or lump ore that the briquetting material is briquetted with a loose roll and a fixed roll and that the nip is adjusted such that a briquette strip is formed, it has always been assumed in the prior art that fine ore has to be pelletized prior to the briquetting process so that the pellets stretch in the area of the briquette seam during briquetting and contribute to bridging and to the achievement of a briquette strip at all.
The present invention shows however that it is certainly possible to press fine ore directly into a briquette strip, the invention having the enormous advantage as compared with the single briquetting method in which fine ore is not compacted, that there is a considerable increase in the service life of the molding bodies of the press rolls which consist of segments or rings provided with briquette pockets, which in the final analysis will lead to reduced lower segment or ring costs. Although the appearance of the briquettes is not quite so good any more, these are after all intermediate products that are intended for further processing, so that such a drawback is of very little importance in view of the improved service life.
Furthermore, it is of special advantage when during briquetting fine ore which is compacted by one of the separating webs between the briquette pockets, and fines in dust form are produced, said materials being separated as returns from the sponge iron briquettes and directly supplied to a conveyor system, and the still hot returns are supplied by the conveyor system substantially uniformly and continuously to the hot fine ore to be still briquetted. The fine ore is then coarsened evenly by the continuously fed returns, which is of advantage to an improved briquetting capacity. In particular, this step of the method is very positive at the beginning of the briquetting process, since no additional measure has to be taken for preventing the fine ore from simply flowing through the nip, which can certainly happen with excessively loosened fine ore.
In another advantageous step, the briquette strip can be divided by a briquette strip divider into individual sponge iron briquettes and returns. The sponge iron briquettes and the returns can subsequently be conveyed to a vibrating screen, which separates sponge iron briquettes and returns from each other.
The fine ore which is mostly loosened due to transportation from the reducing system to the press roll can
REFERENCES:
patent: 3627288 (1971-12-01), MacDonald
patent: 4601728 (1986-07-01), Dungs et al.
Chi Anthony R.
Jordan Charles T.
Maschinenfabrik Koppern GmbH & Co. KG
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