US1999825A - Treatment of nelsonite ore - Google Patents

Description

April 30, 1935. B, D. sAKLA'urWALLA m- AL '1,999,825

TREATMENT OF NELSONITE ORE Filed Nov. 29, 1952 Patented Apr. 30, 1935 TREATMENT F NELSONTTE Byramji D. saklatwaua and Hulbert Earl Dunn, Crafton, Pa., assignors -to Southern Mineral Products Corporation, New York, N. Y.,

poration of Delaware a cor- Appucation Ntvember 29, 1932, serial No. 644,833

4 claims. (c1. zoe-2) The present invention relates to the treatment known. The grinding is carried out with steel rods which are preferably light rods about an The limited amount of water forms a thick mud with the vore being ground. This thick mud tends to cushion the impact of the rods upon each other and to cause the relaof nelsonite ore, and more particularly to the re- ?!overy of ilmenite and apatite concentrates there om. Y f v The term nelsonite is applied to ores composed principally of an aggregate of ilmenite and apatite, together with biotite, its related minerals,

and clay material in Varying proportions. Ihnenite consists essentially of iron and titanium oxides which may berepresented generally by the formula FeO.TiOz. The apatite is a uorapatite and consists principally of calcium fluorphosphate which may be represented by the formula Ca5F(PO4)s. Biotite is sometimes designated as black mica or iron-bearing mica because of its iron content. In the nelsonite ore the biotitic mica is in various stages of weathering, some of the mica being in its platey form and some in an altered powder-like condition.

The principal deposits of nelsonite ore in the United States occur in Nelson and Amherst Counties, Virginia. These deposits have been known for many years and various attempts have been made to work the ores. All attempts to work the ores have heretofore failed because of the seemingly insurmountable diiiiculty of commercially separating the various constituents of the ore. These extensive nelsonite deposits have thereforel heretofore been regarded of little, if any, value.

We' have discovered a-process1 whereby high grade concentrates of ilmenite and of apatite may be recovered from nelsonite ore. The ilmenite concentra produced is well adapted for the manufact e of titanium dioxide. The apatite concentrate is adapted for conversion into phosphoric acid or phosphoric acid products. 'Ihe steps of our process are outlined on the accompanting` drawing which is a diagrammatic iiow sheet. The process will be explained in connection with such ow sheet. x

The nelsonite ore as received inlumps from the mining operations is first put through a rock- Y crusher in which it is crushed, preferably to about 2 inch size. The crushed ore is carried to a storage bin from which it is fed to a grinding mill, preferably a rod mill. The grinding is preferably wet grinding, about 30% by Weight of water being added tothe material in the rod mill. The rod mill is of the usual construction, the details of which need not be described as they are wellinch in diameter.

tively light rods to have a` rubbing or scrubbing action upon the-particles of the 'ore rather than an impact crushing action. 'Ihis is highly desirable since the individual crystals of the ilmenite and apatite should be preserved as such as far as possible, the desirable action of the rod mill being to separate thev` crystals of ilmeniteand apatite from each other and to scrub from such crystals the adhering mica and clay. The rod mill operation is preferably a continuous operation, the crushed rock being fed in at one end and the slurry being discharged fromtlre other end. The degree of particle size reduction is so controlled that while the aggregates consisting lof ilmenite and epatite crystals are broken up to free the ilmenite and apatite crystals from each other, the individual crystals are retained as such so far as possible in an uncrushedcondition. The softer biotitic alteration products and clays are, however, pulverized to a fine semi-colloidal condition.

It is important that the degree of crushing of the ore be controlled in order to secure efficient operation in the classiiication and magnetic separation operations to follow. In order to secure separation of the apatite and ilmenite from each other and from the gangue of the ore, it is necessary. to crush to th'e point where substantially all of the ilmenite and apatite crystals are freed as such from4 the other materials. It is also important, however, that the separated crystals be retained, so far as practicable, in their original crystalline size in order to'secure separation of theprystais from the clay and other une material in the water classifier and to secure the separation of the ilmenite and apatite crystals from each other and from the undecompo'sed plate-like biotitic mica in the magnetic separator. We have found that the reduction of the material to retain the crystals of ilmenite and epatite insofar as possible without crushing the individual crystals, gives a crystal size which is well adapted for both the water ction an separation.

d the magnetic The mud-like slurry from the rod mill is delivered to a vibrating screen of 35 to 48 mesh to the inch. More water is supplied to thescreen to assist in the screening operation. All oversize material is returned Lum the screen to the rod mill.

The nelsonite ore as now obtained from one of the mines in Nelson County, Virginia, contains approximately 43% ilmenite, 20% apatite and 37% gangue, consisting of mica alteration preducts, clay, etc. The screen analysis of the material passing through a 35 mesh screen is approximately as follows:

All pass 35 mesh standard Tyler screen;

While 51% passes through 200 mesh.

The slurry which was diluted to about 20% solids by the water added onto the screen, is pumped to a deslimer for the removal of the greater part of the clay and the fine biotite alteration products. These materials are in the class known as slimes and are of a colloidal or semi-colloidal consistency. The deslimer is preferably of the type known as a Callow cone or Allen cone, the constructions of which are wellknown in the ore treating art. A deslimer of the cone type consists essentially of a cone-like receptacle of sufficient size to act as a settling tank. The coarser material settles to the bottom of the cone from which it is automatically discharged, while the slimes consisting of the colloidal or semi-colloidal finely divided clays and mica alteration products which constitute the gangue of the ore overflow at the top of the cone. 'I'he overflow is run to the dump.

The function of the deslimer to remove the greater part of the very ne material consisting principally of the colloidal or semi-colloidal clays and biotite alteration products, which would inter'fere with -the most efficient operation of the classifier, to which the material is next conveyed.

The deslimed sand from the deslimer is conveyed to the classifier where more water is added and in which the remainder of the fine'material is removed. While itsis preferred to secure the removal of the claymaterial and the biotite alteration products by a two-step separation involving an initial desliming followed by classification, such removal can be secured in a single step in a suitable classier. However, the commercial classifiers on the market operate much more efliciently if the greater part of the colloidal or semi-colloidal materials are removed by a preliminary desliming operation.' Any suitable form of ore classifier may be employed, such as the well-known Akins classifier or the Dorr classifier. The construction and operation of these classifiers is well-known in the ore-treating art and they need not be described in detail. Generally speaking, the classier, such as the Akins classifier, consists of an inclined trough having a rotating spiral conveyor therein. The material to be classified is run, together with water, into the lower end of thetrough which forms a bowl or settling basin. The screw conveyor gently agitates the material and conveys the material from the-. settling basin or bowl along the inclined trough from which it is discharged. There is a constantv overow from the settling basin', the

overflow carrying away the ne material. The sand-like material which is removed by the conveyor is substantially free of all fine material, such as the remaining clay and mica alteration products which were not removed by the deslimer. The sands as they are carried up from the settling basin by the screw conveyor are preferably subjected to water sprays to secure the thorough removal of remaining traces of such fine material.

The classification resulting from the deslimer and classifier should be equivalent to what is known as a free settling period of from 4 to 51/2 minutes in order to produce a sand sufficiently clean for magnetic separation and at the same time not to incur too high a loss of apatite mineral in the overflows.

The solid material discharged from the classifier is a fine clean sand which, as obtained from the ore ofthe mine above mentioned, consists approximately of 69% ilmenite, 21% apatite and 10% gangue consisting principally of the platey biotite. The screen analysis of this material is approximately as follows:

Percent Retained on 35 mesh standard Tyler screen- .2

The clean sand discharged from the classifier is then passed through .a drier, which is preferably of the rotary continuous type, which removes the water and delivers dry free flowing sand to a cooler where it is cooled to room temperature. The sand is then passed over a vibrating screen of preferably about 20 meshes to the inch, for the purpose of removing any relatively large particles of foreign matter, such as wood, which may have been accidentally introduced into the material, as well as any large agglomerates produced in tlie drier. Any traces of clay which may pass the classiiier tend to become agglomerated in the drier and are removed by the screen. The over-size refuse from the screen is discarded.

The dry free flowing screened material then passes to a magnetic separator inwhich there is selective separation of the ilmenite, the apatite andthe biotite. Y. l

The magnetic separator should be,i one which secures the selective separation of different constituents of the ore in accordance with their relative magnetic susceptibility. There are various separators on the market which will accomplish this result. The separator is preferably of the well-known induction roll type, the construction of which is well-known in the magnetic separator art and need not be described in detail. In general, it is stated that the magnetic separation is secured by passing the granular sand-like material past a number of rolls. Each roll consists of a series of fiatl circular soft iron disks with non-magnetic spacers between them. An electromagnet is located in proximity to the face of the roll and the material passes between .Wise embodie rolls is progressively. increased fromthe iirst to the last roll, the first roll being relatively weakly magnetic.

The ilmenite which has a magnetic attractive force oi about 25 as compared .with 100 for iron particles, is separated out by the iirst three rolls. The magnetic effect of these rolls, while strong enough to remove the strongly magnetic ilmenite,

is not strong enough to remove the biotite' whichl has a magnetic attractive torce of about 3, and the apatite which has a magnetic force of about 0.2, as compared with 100 for iron particles. The last three rolls, which are more strongly magnetized than the rst three, separate the weakly magnetic biotite from the apatite.

The material separated by each roll is run into bins and the apatite, which is substantially nonmagnetic, passes through the machine and is run into an apatite storage bin. The biotite, which is a waste product, is discarded. Under properly controlled conditions it is possible to secure a recovery of from to 95% of the ilmenite content of the ore and to secure a recovery of from 70 to 75% of the apatite content of the ore. The reason for the greater percentage of thevilmenite recovery is that the-ilmenite crystalsare harder and there is less loss o! ilmenite in the-deslim ing and classifying operations than there is of the softer apatite. The ilmenite fraction is a high-gradeconcentrate containing about to 96% of ilmenite. This concentrate is suiciently p ure to furnish a good raw material for the production of titanium dioxide according to the usual methods of preparing titanium dioxide from ilmenite. 'I'he apatite fraction is also a highgrade concentrate containing about 97%` or over of apatite. In case the ore is treated for the recovery of the ilmenite fraction only, there will be no separation of the biotite from the apatite and both will be discarded together.

While we have specically described'the preferred procedure in practicing our invention, it is to be understood that the invention is not limited to its preferr d embodiment, but may be otherand practiced within the scope of the following claims. We claim:

&

1. The process of recovering ilmenite and apatite concentrates from nelsonlte ore, which comprises adding about 30% of moisture to the ore and subjecting the oretogether with its clay constituents to impact of steel rods in a rod mill to a limited extent suilicient to reduce the gangue but not to pulverize the ilmenite and apatite crystals, separating the iinely divided gangue from the ilmenite and apatite, and thereafter magnetically selectively separating the ilmenite, apatite and biotite.

2. 'I'he process of recovering ilmenite and apatite concentrates from nelsonlte ore, which comprises adding about 30% of moisture tothe ore and subjecting the ore together with its clay constituents to impact of steel rods in a rod mill to a limited 4extent sulcient to reduce the gangue and subjecting the ore together with its clay constituents to impact o f steel rods in a rod mill to a limited extent suflicient to reduce the gangue but not to pulverize the ilmenite and apatite crystals, separating the iineiy divided gangue from the lilmenite and apatite, and thereafter vmagnetically separating the ilmenite from the apatite and biotite. 1

4. 'The process of recovering ilmenite and apatite concentrates from nelsonlte ore, which comprises adding to the ore s uiiicient water to produce a thickI mud when ground, and. subjecting the ore together with its clay consituents to impact of steel rods in a rod .mill to a limited extent sulcient to reduce the gangue but not to pulverize the ilmenite and apatite -crysta1s, separating the iinely divided gangue from the ilmenite and apatite, and thereafter magnetically selectively separating the ilmenite, apatite and biotite.

BYRAMJI D. SAKLATWAILA.

HOLBERT EARL DUNN.

prises adding about 30% of moisture to the ore

Images