US2378357A - Method of concentrating minerals - Google Patents

Description

June l2, 1945. L.. J. ERCK METHOD OF CONCENTRATING MINERALS Filed Deo. 1943 s sheets-sheet 1 linien/Z071 /Qf Z fior/vz June 12, 1945. L. J. ERcK METHOD .OF CONGENTRATING MINERALS Filed DeC. 27, 1943 3 Sheets-Sheet 2 June 12, 1945. L J ERCK 2,378,357

METHOD OF CONCENTRATING MINERALS Filed De. 27, 1943 3 Sheets-Sheet 3 7 FEED (dal or' 0f@ 'V Pif/VARY CZiS/F/EP l ca/vcf/vrame off F//VfS ma 24205057 I) 7a 14am, 0f

wai/65125 ames/2f v i 5J/'mes 55m/maw ca/Ycf/vmame 105mm/6 fc/eff/v PUMP liz/verifier Patented June 12, 1945 ME'rnon or ooNoEN'raArING MINERALS Louis J. Erck, Cooley, Minn.,/assignor to Minerals Beneficiation, Incorporated, Joplin, Mo., a corporation of Delaware Application December 27, 1943, Serial No. 515,693sVV 'l Claims. (Cl. 209-173) It is an object of this invention to provide a novel, simple and eiilcient process for concentrating minerals, including coal, containing low density material of a wide range of particle sizes .associated with relatively high density material' containing substantial quantities of particles of substantially all size ranges up to the maximum size of the particles being treated. The invention is perticularly,although not exclusively, adapted for the treatment of such fragmentary material of minus three-eighths inch sizes which are dim- Hcult to concentrate economically by other known methods.

A further object is to provide a novel and commercially inexpensive process for separating the coarser particles of low speciiic 'gravity from fragmentary minerals of the character described.

With these objects in View, according to the present invention, .the crude mineral, after such preliminary scalping and desliming or classifying treatment as may be necessary or desirable is continuously fed to a tank wherein it is mixed with a fragmentary material or, high density. This mixture is accumulated as a dense mass through which sufficient water is percolated to keep the solids in a uniformly wet state without applying sumcient hydraulic lifting force tc cause a teetering condition and Whilemechanical agitation is applied to work the coarser particles ci' low specic gravity to the top of the mass. This mass, being too Viscous or densely crowded to per mit classification depending on particle size, may be said to be in a semi-fluid condition. From the upper surface of this mass the coarser constituents of low specic gravity are continuously discharged through an elevated outlet or overflow' while the heavier constituents are removed from another outlet.

The heavy material to be added to the cre -in the tank is preferably obtained from the ore itself. A continuous, controlled supply of the high density product may be recirculatedthrough the concentrator tank while the remainder of that product may be either used, further concentrated or wasted, depending on its value and purity. With some coals and ores it may be advantageous to netite, ferro-silicon or other solids o'f magnetic susceptibilitymay be used to increase the density of the semi-iiuid mass in the concentrator. After its removal from the concentrator, the magnetic material may be recovered from. the non-magnetic ore by magnetic attraction, according to conventional practice. If heavy, non-magnetic solids are added, they may be separated from the coal or other products by. hydraulic classification, screening and washing, or other suitable treatment.

/Referring to the accompanying drawings:

Figure 1 'is a, diagrammatic illustration of a suitable concentrator machine and auxiliary ap paratus and connections for carrying out my invention: Figs. 2 and 3 are diagrammatic cross sections taken on the lines 2-2 and 3-3 of Fig. 1 and illustrating particularly the disposition of the material in the concentrator;

Fig. 4 is a plan view illustrating a concentratcr machine ci the preferred type;

Fig. 5 is a fragmentary section through the machine taken on the line 5--5 of Fig. 1

Fig. 6 is a section taken on the line 6-6 of Fig.

4; and

Figs. 'l and 8 are flow sheet diagrams indicating, by way of example, specific applications of my process to the concentration of ores and separation of coal from some of its common impuri-n ties.

add to the mineral in the concentrator tank a i foreign substance having the desired relatively high specic gravity. In the cleaning of coal, for

-examplathe main product has considerably lower specific gravity than the materials to be separated therefrom and the added material may be sand or other comminuted solids of substantially higher specific gravity than the coal. Where a non-magnetic ore is to be concentrated, magscreen I0 will ordinarily have openings of sizes within the range 1A; to of an inch.

The undersize from the screen Iiil contains, ordinarily, substantial quantities of particles of substantially Iall size ranges up to the maximum size of the material to be treated and of both high density and low density. With most minerals it 1 is desirable to separate, as the next operation, the bulk of the finer low density constituents. A classifier of any of a number of common types may be used for this purpose. For example.- a hydrau.ic classifier Il having an inclined trough and a conveyor of the reciprocating rake type may be used and the undersize mineral from the screen l 0 may be delivered continuously to a feed tice. Where the mineral to be concentrated is coal, the fine low density product which overflows the Weir I4 usually consists of slimes and finev coal, together with some fine high density constituents, such as slate and sand. The fine par-l ticles of coal may be recovered by froth flotation or other suitable treatment.

From an outlet I5 at the upper end of the machine I I the bulk of the high density material and coarse low density material is discharged into the conduit I5 extending to the feed box I1 of a concentrator machine, indicated generally by the numeral I8. This machine has a long narrow tank, the bottom I9 of which is inclined and the several products are discharged over an elevated overflow or Weir at the lower end of the trough and through an outlet 2l at its upper end.

A rotary conveyor having spiral nights. 22 is mounted within the tank, extending substantially from end to end thereof. Supporting the flights 22 is an axial shaft 23 having at its upper end a bearing supported on a horizontal pivot shaft 24. A motor 25 is provided to drive the shaft 23 .through suitable speed reducing gearing, both the motor and gearing being pivoted on the shaft 24. Provision is made for raising the lower end portion of the conveyor and shaft 23 above the material in the tank and for gradually lowering the assembly when the machine is started with an accumulation of material in the tank. For this purpose a substantially vertical screw shaft 2S is connected to a vertically adjustable, lower end bearing for the shaft 23 and a nut 21 is threaded on the shaft 26 and pivotally supported on a bracket 28. A manually operable crank 28 projects from the nut` 21 to be rotated to move the lower end of the shaft and conveyor nights to and from the mass of .material in the concentrator. This supporting and operating mechanism for the screw type conveyor is of the conventional Akins type, the details of construction 'and operation of which are matters of common knowledge in this art.' l,

A multiplicity of perforations 38 are formed in the bottom I 9 of the machine to communicate v with hutch water tanks 3I. 'I'hese tanks are divided longitudinally and transversely into small compartments and each compartment is supplied with water under pressure by a pipe 32 having a control valve 33. The hutch tanks extend along the bottom of the machine continuouslyggfor the greater part of its length, terminating only a short distance above the lower end and below the upper end outlet 2|. Fixed on the spiral flights 29 at their outer peripheries are a series of lifting bars 34 which extend'along the conveyor substantially from the lower end of the tank to the upper extremity of a dense mass 3l of solid particles which is maintained within the machine according to my invention. As indicated in Figs. 2 and 3, the mass 35 of fragmentary solid material is maintained within the lower portion of the machine with the upper surface of the mass approximately at the level of .the weir 20. Water from theV hutch boxes finds its way through the mass and ows on the surface toward the weir, as indicated at 36 (Fig. 3).

In operation, the shaft 23, carrying the flights the screw flights 22.

22 and bars 34, is continuously rotated at a low speed and in the direction indicated by arrows in Figs. 2, 3 and 5. This causes the material in the machine to be raised somewhat higher along the side where the bars 24 emerge from Ithe mass, than at the opposite side. A stream 38 of water flows on the surface of the mass, down the lower side toward the weir. As best shown in Fig. 5, the Weir 20 extends only part way across the machine and a baille 31 is provided at the opposite side in the plane of the Weir to direct the stream 3B laterally of the trough toward the weir. By thus retarding the stream I allow the heavier material carried thereby to settle and remain in the tank while the lighter material is carried over the weir and is discharged through a conduit 38.

From the outlet 2I at the upper end of the machine I8 the higher density constituents of mineral are discharged into a conduit 38 (Fig. 6) which is divided by a central partition 39 so that portions of the product may be delivered to a conduit 40 and other` portions to a branch conduit 4I. The portions of material which are discharged through the respective conduits may be regulated by operating a. movable partition member 42. This member is fixed on a hinge pin 43 having bearings in the conduit 38 and fitted with a manually operable handle 44 adapted to be held in selected positions along a toothed segment 45. Any of a number of standard types of controls for the adjustable partition member 42 may be substituted for that illustrated.

Material from the branch conduit 4I, together with suicient water from a pipe 4B to render the mixture duid, may be fed to a pump 41 adapted to return any portion or all of the high density product through a `conduit; 48 and the feed pipe I8 to the concentrator machine. The feed box I1 extends obliquely downward along the side of the concentrator tank near the central portion of the mass 35 of material in the tank. The highl density material to be recirculated enters the tank together with that fed' from the classifier outlet l5 and water may be added to the feed material from a pipe 48.

As the mixture of mineral from the primary classifier and heavier product of the concentrator enters the concentrator tank, the heavier fractions of both the fine and coarse constituents of the ore and recirculated material settle immediately to the bottom of the tank at the feed point and are started on their upward path by The intermediate grade of material, which is largely coal in coal cleaning operations and coarse silica in the concentration of iron and certain other ores, together with some of ne high density constituents, are accumulated in the lower end portion o f the tank where such material and constituents form the dense mass 35. By proper adjustment of the rate of feed of high density material from the conduit 48 relative to the feed from the primary classifier and by coordinating these controls with the speed of the operation of the conveyor shaft 23 and the distribution and quantity of water admitted from the hutch tanks 3|, the mass 35 is built up and maintained so that its upper surface is approximately at the elevation of the Weir 20 and the necessary semi-fluid condition is obtained in the mass. By the proper use of the controls hereinbefore described, I maintain in the concentrator a body of mineral which is too dense or viscous to permit classification depending on particle size and wherein the force of the upwardly percolating dicated, if the bulk of the be fed to a ooncentrator water is so limited that it does notI place the mass in teeter. Under these conditions, the rotation of the flights 22 carrying the bars 34 across and upward through the mass causes the coarser low density constituents of the material to be worked to the surface while the stream 36 of water, flowing toward and over the Weir, carries such constituents with it out of the machine.

It will be understood that some of the fine high density material as well as some of the remaining fine low density particles are also carried out in the overflow. These overflow products are collected from the weir and leave the machine through a conduit 38. From this conduit the overilow may beied to a vibrating screen 50 of such ne mesh as to recover, as the oversize, all particles of larger size than' those which can be recovered from the overflow of the primary classifier machine Il. In the cleaning of coal, the oversize from the screen 50 comprises the bulk of the coarser coal product. The undersize from the screen 50 may be conducted to a pump 5l and thence through a conduit 52 extending to the feed box I2 of the primary classifier machine Il. In this manner both the ilne low density and ilne high density constituents of the product from the weir `2l) may be recirculated and recovered after further classification.

The flowsheet diagram, Fig. 7, indicates in full lines a preferred series of steps in the treatment and by broken lines optional procedure. As infeed of the primary classifier consists of coal and slate, the overflow from this machine may be fed to a sludge screen of suitable mesh to permit separation of fine slimes and water as the undersize and recovery of a substantially clean, fine coal as the oversize material. According to conventional practice, the sludge screen preferably has a deck made up of a fine screen section (100 mesh, for example) and a coarser screen section (48 to 65 mesh) to successively receive the overflow product and to recover coal particles o'f correspondingly large sizes. Where the feed material of the primary classifier is ore other than coal the be either wasted or subjected to other treatment for the recovery of valuable fines. The underflow or rake product from the primary classifier may machine such as the machine i8 hereinbefore described. To'obtain the desired high specific gravity and pulp struc-A ture in the semi-fluid mass in the concentrator a portion of the heavy underflow product from this machine may be recirculated and returned to the concentrator while the remainder ofthe overflow material may From the primary classifier, the overflow containing particles of coal, slimes, etc. may be either wasted or delivered to a sludge screen, as indicated, or subjected to other treatment to recover the coal. The main product of the primary classiilerconsists of pyrite, slate and coal. This is fed to a concentrator machine, preferably of the inclined trough, screw conveyor type hereinbefore described. The overflow from this main concentratorv may be treated as indicated in Figs. l'and 8 by screening to recover the coarser coal as the oversize screen product and the undersize particles from the screen containing fine slate, pyrite and coal may be returned to the primary classifier. 'I he heavy product of the main concentrator is discharged from the upper end of the machine by the conveyor. All or any portion of this product may be returned to the main conf centrator to maintain the desired high density of the mass therein. To recover the pyrite from the slate contained in the remainder of the main conoentrator product, this portion may be fed to a secondary concentrator. As further indicated in Fig. 8, the overflow from lthe secondary machine heavy product is bled off through an outlet such as the outlet 40 (Figs. 1 and 6). With some ores it is advantageous to add heavy fragmentary material, which may be derived from the ore itself or consist of other finely divided solids, such as those hereinbefore described, directly to the concentrator, as indicated in broken lines, Fig. '1. It is also advantageous in the coals and ores to screen the overflow from the concentrator to recover the oversize material as v the coarser light product and in some cases to re turn the screen undersize material to the primary classifier, as indicated. In the cleaning of some coals the concentrator overflow screen should have 28 openings to the inch where the sludge screen' (Fig. 7) is of 100 to 48 mesh.

For the flowsheet shown assumed that the feed contains pyrite and slate in addition to coal and the ordinary slimes and other waste material.

l part of my application treatment of certain in Fig. 8, it may be for the primary classifier is largely slate which may be wasted and the heavier product of the secondary concentrator is largely pyrite. To raise the specific gravity and viscosity of the mass in the secondary machine, at least a portion of its heavier product may be returned to its trough and the remainder may be either subjected to further concentration or used in the production of acid or for other purposes.

In the treatment of minerals containing a preponderance of low density constituents all of the high density product ofthe concentrator machine is ordinarily returned to the machine at the start and during the early stages of the operation by appropriate operation of the branch discharge control member 42. Only after the bed has been built up to the desired high density is the control member 42 adjusted so that a portion of the heavy product is bled off through the conduit 40. The quantity of high density product. thus recovered is equal to the amount contained in the feed for the primary classifier less the small amount which is discharged with the oversize of the screen 5i) (Fig. 1) and that contained in the overflow from the primary classifier. It will thus be evident that the major portions of the coarse and fine high density constituents of the mineral are recovered as the heavy product of the concentrator and that the overflow products of the concentrators and primary classifler contain substantially all of the coarse as well as ne low density constituents. The process is a continuous one requiring relatively inexpensive machines and apparatus and an unusually small amount of skilled attention and control.

-The present application is a continuation in Serial No. 436,419, filed March 27, 1942, and the latter is a'` continuation in part of my application Serial No. 395,809, filed May 29, 1941, for Method of concentrating minerals. The term ore as used in the appended claims is intended to include coal containing impurities or gangue material.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

l. The continuous method of concentrating an ore containing substantial quantities of coarse low density material associated with relatively high density material in the form of particles of substantially all size ranges up to the maxium size ci' the particles being treated which cornprises adding nnely divided high density lmaterial to such ore and subjecting a mixture of the ore and added material to hydraulic concentration in a tank wherein a mass of solids and Water too viscous to permit classiiication depending on particle size is subjected to upward percolation of water having forceiinsuicient to cause teetering of the mass and mechanical agitation having lifting and releasing effects throughout and extending to the top of said mass to produce two products one of which is rela* tively rich in high density material and relatively poor in coarse low density material and the other of which is relatively rich in coarse low density material associated with fine high density material.

2. The method described in claim l in which said high density material is added by recirculating to said tank at least a portion of said product which is relatively rich in 'nigh density material and relatively. poor in coarse low density material.

3. The method described in claim l in which said high density added material is foreign to the ore.

d. The continuous method of concentrating an lore containing substantial quantities of high density material in particles of substantially all size ranges up to the maximum size of the particles being treated, associated with relatively low density material in a Wide range of particle sizes which comprises adding coarse and ne high density material to such'ore and subjecting a mixture of the ore and added material to hydraulic concentration in a tank wherein a mass of solids and water too viscous to permit classification depending on particle -size is subjected to upward percolation of water having force insufncient to produce a teetering of the mixture and mechanical agitation having lifting and releasing effects throughout and extending to the top of said mass to produce two products one of which is relatively. rich in high density material and relatively poor `in coarse low density material and the other of which is relatively rich in coarse low density product a product which is rich in high density material and relatively poor in low density material.

5. The continuous method of concentrating. an ore containing fragmentary low density mate.- rial in a wide range of vsizes associated with relatively high density material in the form of particles of substantially all size ranges up to the maximum size of the particles being treated and in which the constituents of low density predominate which comprises adding high density material to such ore in particles of sizes common to a portion of the material under treatment and subjecting a mixture of the ore and added material to hydraulic concentration in a material associated with line high density material and recirculating from the first..

tank wherein -a mass of solids and water too viscous to permit classification depending on .particle size is subjected to upward percolation of water having force insuilicient to cause teeter- -ing of the mass and mechanical agitation havving lifting and releasing effects throughout and extending to the top of said mass to produce two products one of which is relatively rich in high density material and relatively poor in coarse low density material and the other of which is relatively rich in coarse low density material associated with fine high density material.

6. The continuous method of concentrating an ore containing substantial quantities of coarse low density material in a wide range of particle sizes associated with relatively high density material in the form of particles of substantially all size ranges up to the maximum size of the particles being treated which comprises adding high density material to such ore in particles of sizes common to a portion of the material under treatment and subjecting a mixture of the ore and added material to hydraulic concentration in a tanl` wherein a mass of solids and water too viscous to permit classification depending on particle size is subjected to upward percolation of water having force insuiiicient to cause teetering of theimass and mechanical agitation having lifting and releasing effects throughout and extending to the top of said mass to produce two vproducts one of which is relatively rich in high density material and relatively poor in coarse lowdensity material and the other of which is relatively rich in coarse low density material associated with fine high density material.

7. The continuous method oi concentrating an ore containing substantial quantities of high density material in particles of substantially all size ranges up to the maximum size of the par ticles being treated, associated with relatively low density material in a wide range of particle sizes which comprises adding high density material which is foreign to the ore to such ore and .subjecting a mixture of the ore in particles of sizes common to a portion of the material under treatment and added material to hydraulic concentration in a tank wherein a mass of solids and water too viscous to permit classiiication depending on particle size is subjected to upward percolation of water having force insumcient to produce a teetering of the mixture and mechanical agitation having lifting and releasing eii'ects throughout and extending to the top of said mass to produce two products one of which is relatively rich in high density material and relatively poor in coarse low density material and the other of which is relatively rich in coarse low density material associated with fine high density material, discharging said products from the tank, recovering the foreign material from said products and returning the recovered foreign material to said tank.

` LOUIS J ERCK.

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