CA1214443A - Selective rolls crusher - Google Patents

Abstract

A B S T R A C T

A process and apparatus for selectively crushing the softer portions of a conglomerate rock so as to beneficiate the softer portions thereof while leaving the substantially barren harder portions substantially untouched is described. The rock to be treated is fed to a horizontal rotating drum containing a single cylindri-cal rod rotatable longitudinally therewith. The size of the rod is selected to provide a crushing force between 10 and 100 g/cm2, depending on the actual material to be crushed. In a preferred embodiment one or two substantially concentric cylindrical tubes are loosely spaced inter-mediate the drum and the rod and rotated relative thereto so as to provide additional crushing surfaces.

Description

FIELD OF INVENTION
This invention relates to a process and apparatus for selective crushing of conglomerate rocks. More particularly this invention relates to a selective roll crusher for use in material upgrading o-f nickel bearing lateritic rocks in which the soft weathered lateritic rock generally contains a much higher concentration of nickel than the harder protore-type rocks.
BACKGR~UND OF INVENTION
Heretofore at-tempts have been made to upgrade minexal contents by crushing and screening lateritic rocks using conventional equipment but with only marginal success.
OBJECT OF INVENTION
It is, therefore, an object of the present invention to provide an apparatus which will provide sufficient crushing force to break relatively soft weathered rock but insufficient force to break rela-tively harder, nickel barren, rock.
Another object of the invention is to provide a pxocess for selectively crushing conglomerate rock so as to effect mineral upgrading of a portion thereof.
Thus, by one aspect of the invention there is provided a rotary xoll crusher for selective crushing of conglomerate type rocks, comprising:
(a) an imperforate cylindrical shell having material feed means at one end thereof and material ~r discharge means at the other end thereof, arranged for rotation about a horizontal axis; and (b) a single cylindrical rod loosely arranged longitudinally within said cylindrical shell for axial rotation relative thereto as said shell is rotated so as to provide a crushing force in the range 10 - 100 g/cm2, between said rod and said shell and thereby effect selective crushing of said conglomerate rock.
By another aspect of the invention there is ~o provided a process for selectively crushing a relatively softer portion of a conglomerate ore so as to upgrade the mineral content of the crushed portion thereof, comprising feeding the ore into a drum rotating about a horizontal axis and containing a longitudinally extending cylindrical means loosely arranged for an axial rotation with the rotating drum so as to provide a crushing force of between 10 and 100 g/cm2,continuing rotation for sufficient time to produce a beneficiated product which passes a ~" screen, and separating the beneficiated product from hard over size material.
BRIEF DESCRIPTION OF DRAWINGS

_ The invention will be described hereinafter with reference to the drawings in which:
Figure 1 is a longitudinal cross-sectional view of a roll crusher accord.ing to one embodiment of the invention;
Figure 2 is a perspective view of the roll crusher of Figure 1 with the end cap removed; and Figure 3 is a transverse cross-section of th~
crusher of Figure 1 shown full of charge material.

DE~AIL~D DESCRIPTION OF PREFERRED EMBODI~lENTS

_ _ Beneficiation of relatively low grade lateritic nickel ores is of considerable importance in reducing the cost of extraction of nickel from such ores, however conventional mineral dressing techniques such as flotation, gravity separa-tion and magnetic separation are not readily adapted to beneficiationof laterites. Lateritic nickel ores generally comprise a mixture of relatively soft limonitic ore and substantial amounts of relatively hard, rocky serpentinic ores having a range of various nickel concentrations. The limonitic ores are usually separated from the rocky serpentinic ores by first crushing to less -than 5 cm sizes if needed and by screening. The serpentinic ores remaining do, however, comprise some rela-tively weathered, somewhat softer fractions containing approximately 1.5~3.0% Ni, as well as relatively harder, unal-tered ore fractions which generally contain less than 1.5% Ni. It is, therefore, desirable -to selectively crush the softer ser-pentinic fraction to therehy liberate the nickel bearing fraction, while leavinq the harder, barren fraction sub-stantially untouched. Preferably, the crushing operation is carried out dry, at the natural moisture level of the mine-run rock, and it is desirable to crush the softer rock rather than cause attrition thereof which generates ~ 4 a relatively high proportion of fines (-100 Mesh). The selective, multiple tube roll-type internal crusher illustrated in Figures 1, 2 and 3 has been found effective for this purpose. In Figure 1 there is shown an outer cylindrical shell 1 mounted on a pair of parallel driven rolls 2, 3. One or more axially rotatable cylinders (4, S in Figure 1) are loosely longitudinally contained inside shell 1, and a solid cylindrical rod 6 is longitudinally mounted for axial rotation within shell 5.
The diameters of shells 4, 5 and rod 6, relative to each other and to shell 1 are selected so as to provide crushing Eorce between each respective pair of contacting surfaces of between about 10 and 100 g/cm2 and preferably between about 30 g/cm2 and 70 g/cm2 depending upon the particular ore material, as described in more detail hereinafter with reference to the examples. The unit may be operated with continuous feed and discharge and by controlling these rates any desired residence time can be achieved to effect any desired degree of crushing and separation. The crushing force applied in any particular application is also related to the size of the rolls crusher selected. As the`size increases, so the crushing force increases. As crushing force increases, residence time in the crusher may be decreased. Even greater forces than the preferred 100 g/cm2 maximum may be generated intermittently as the rolls move.

~L2~ 3 Example l A selective rolls crusher, similar to that shown in Figure 1 but containing only one cylinder, was built with an outermost shell of 12 inches internal diameter and length of 20 inches. The cylindrical shell was closed at the back end, and had a removable plate at -the front end for loading. Inside the shell, was placed a 7 inch diameter, 16 inch long cylinder, with wall thickness of ~
inch, open at both ends which, in turn, housed a solid rod,

2.5 inch diameter and 16 inches long. The internal open cylinder weighed 29 Kg and the solid rod 5.7 Kg. The crusher was charged with 10.00 Kg of serpentinic rock between ~ and 3/8 inch particle size, containing 1.47%
Nickel based on its dry weight, and 6O7% free moisture.
The unit was rota-ted at 28 rpm for 10 minutes, then the contents were removed and the partially crushed rock was sorted on a ~ inch mesh screen. The -~ inch size rock fraction was analysed for fines (described as -100 Tyler mesh) and for Ni. The coarse, +~ inch size fraction was returned to the crusher for ano-ther 10 minutes rotation, then removed and screened as after the first 10 minute periodO The coarse +~ inch size fraction of the second rotation was again returned to the crusher for an additional 2S minutes, screened and both ~ractions analysed. The results of the screening and the analysis are shown in Table I overleaf.

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4~3 Thus the generated 5157 g dry product (equivalent to 5503 g of the initial feed) had a combined overall nickel content of 1.77%, while the +~ inch fraction which contained 1.10~ nickel, was rejected. Satisfactory upgrading of the serpentinic rock, having an initial overall nickel content of 1~47%, was attained. The fraction of fines generated was relatively small, indicating that selective crushing of the softer, more weathered portion of the rocks takes place in the rolls crusher of this invention.
Example 2 ~ single roll crusher with the following dimen-sions was used in this test:
Shell, closed at one end, and removable front plate length 20 inches; internal diameter, 16 inches.
Heavy walled tube closed at both ends, was the internal -roll; length: 18 inches, diameter 11 inches weight: 6Ç Kg.
Speed of rotation: 22 rpm.
It should be noted that the above single roll crusher is not to be confused with a rod mill, which usually houses numerous solid steel rods of diameters several orders of magnitude smaller than the shell.
~he object of rod milling is complete reduction in particle size, i.e. grinding; the rolls crusher of the present invention on the other hand, selectively breaks up only the softer rock portions within the harder rock pieces.

The above single roll crusher was charged with 24 Kg of serpentinic rock, having 1.47% Ni content and its particle size ranging ~ 3/8". The capped crusher was rotated for periods of 10, 20 and 30 mins., giving a total rotation time of 60 mins. After each period the contents were removed and passed through a L ~ mesh size screen.
The -3" fraction was weighed, both fractions were analysed for nickel, and the +~" frac-tion was returned to the crusher. At the end of the 3rd period both the product (-~") and the reject 1+~") were weighed and analysed.
The results of the single roll crushing test are tabulated in Table II overleaf.

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The total weight of product at the end of the 60 minutes rotation was 4186 g or 18.3 wt.% of the feed, and this material con-tained 1.89~ nickel. The reject had 1.36~ Ni content and amounted to 81.6~ of the feed;
indicating a high degree of upgrading.
Example 3 This example was carried out using a 16"
internal diameter cylindrical shell 20" long as in Example 2, but housing multiple rollsl composed of 2 cylinders and a solid rod arranged in a pseudo-concentric manner, i.e.
forming rolls within one another, as shown in Figs. 1 and 3.
The two cylinders and the rod were each 18 inches long, and had 11" (I.D.), 6" (I.D.) and 2" diameters, respectively.
Their respective weights were: 26 Kg, 13 Kg and 5.7 Kg.
The cylinders were open at both ends.
The above rolls crusher was charged with 28 Kg serpentinic rock, of 1.47~ Ni content and having particle sizes in the +~" - 3/8" range. The crusher was then capped and rotated at 22 rpm for periods of 15, 15 and 30 minutes, giving a cumulative crushing time of 60 minutes.
~ft~r each period the contents of the crusher were removed and screened on a ~" mesh size screen. The fraction passing through the screen, i.e. particles smaller than ~", were weighed and analysed for nickel.
The fraction composed of larger than ~" particles, was returned to the crusher after a sample had been taken ll for nickel analysis. At the end of the 60 minute period, both the reject (+~") and the product ~-~") were weighed and analysed for nickel. The results are summarized in Ta~le III overleaf.

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The total weight of the <~" sized product was 11,675 g (dry wt~), or 44 7 weight % of the feed, assuming that it initially contained 6.7% moisture. The overall grade of the product was 1.81~ Ni while the nickel content of the reject was 1.21%, showing that the upgrading was efficient. There were relatively small amounts of fines generated by the multiple rolls crusher indicating that it provides primarily selective crushing rather than grinding.
Example 4 A crushing tes~ was carried out in the multiple rolls crusher described in Example 3, which was charged with 31.8 Kg serpentinic rock, of overall nickel content of 1.50~ and particle sizes ranging from ~ to 1~ inches.
The crusher was rotated for periods of 10, 10 and 20 minutes, giving a total rotation time of 40 minutes.
After each period -the contents of the crusher were removed and screened on a ~" mesh size screen. The -41l fraction was weighed and analysed for nickel, while the particles larger than ~" size were also sampled for nickel analysis and returned to the crusher. At the end of the 40 minute period in toto, both the product ~-~") and the reject (+~") fractions were weighed and analysed for nickel.
The results of this test are shown in Table IV overleaf.

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This test indicates the high degree of upgrading that ean be achieved on a rock sample with a wide size distribution, generating a product with 2.27% average nickel content from a feed material containing 1.50~ Ni.
As shown, the bulk of the material was rejected, contain-ing 1.41~ niekel, whieh is below the eeonomieally extraet-able level.
Example 5 A sample of eopper oxide ore was subjected to erushing by the apparatus of Example 1. The ore eontained 5.11~ Cu and was of particle size distribution shown in Table V overleaf.
An 8 Kg sample of this ore was rotated in the crusher for 65 minutes at 28 rpm. At the end of this test period the contents of the crusher were screened on No. 8 Tyler mesh screen, and the fractions weighed and a alysed.
The results are shown in Table VI overleaf.
Thus the fine fraction obtained by selective crushing and eomprisin~ less than two thirds of the ore earried more than 90~ of the total eopper content, indieating good upgrading.
While emphasis has been plaeed herein on benefi-ciation of lateritie niekel ores, it will be appreeiated that the prineiples of the presen-t invention and the apparatus specifically described are equally applicable ~o the beneficiation of other ores such as bauxite, oxidic copper ores and others of similar type.

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Claims (12)

CLAIMS:

1. A rotary roll crusher for selective crushing of conglomerate type rocks, comprising:
(a) an imperforate cylindrical shell having material feed means at one end thereof and material discharge means at the other end thereof, arranged for rotation about a horizontal axis; and (b) a single cylindrical rod loosely arranged longitudinally within said cylindrical shell for axial rotation relative thereto as said shell is rotated so as to provide a crushing force in the range 10 - 100 g/cm2 between said rod and said shell and thereby effect selective crushing of said conglomerate rock.

2. A roll crusher as claimed in claim 1 including at least one open cylinder means intermediate said shell and said rod arranged longitudinally for axial rotation relative to said shell and said rod as said shell is rotated.

3. A roll crusher as claimed in claim 2 including two open cylinder means loosely arranged one within the other inside said shell.

4. A roll crusher as claimed in claim 1 wherein the rod has a diameter of at least 50% of the internal diameter of said shell.

5. A roll crusher as claimed in claim 2 wherein the rod has a diameter of at least 30% of the internal diameter of said cylinder and said cylinder has an external diameter of at least 50% of said shell.

6. A roll crusher as claimed in claim 3 wherein the rod has a diameter of at least 30% of the internal diameter of the first adjacent cylinder, the first adjacent cylinder has an external diameter of at least 50% of the internal diameter of the second adjacent cylinder and the second adjacent cylinder has an external diameter of at least 65% of the internal diameter of said shell.

7. A process for selectively crushing a relatively softer portion of a conglomerate ore so as to upgrade the mineral content of the crushed portion thereof, comprising feeding the ore into a drum rotating about a horizontal axis and containing a longitudinally extending cylindrical means loosely arranged for axial rotation with the rotating drum so as to provide a crushing force of between 10 and 100 g/cm2 continuing rotation for sufficient time to produce a beneficiated product which passes a ?" screen, and separating the beneficiated product from hard over-size material.

8. A process as claimed in claim 7 wherein said cylindrical means is a rod.

9. A process as claimed in claim 8 wherein there is provided a longitudinally extending cylindrical tube means loosely arranged intermediate said drum and said rod and rotatable relative thereto.

10. A process as claimed in claim 8 wherein there is provided a pair of longitudinally extending substan-tially coaxial cylindrical tube means loosely arranged one within the other intermediate said drum and said rod and rotatable relative thereto and to each other.

11. A process as claimed in claim 8, 9 or 10 wherein the crushing force between respective crushing surfaces is between 30 and 70 g/cm2.

12. A process as claimed in claim 8, 9 or 10 wherein said conglomerate ore is a lateritic nickel ore.