US1774786A

US1774786A - Method of and apparatus for treating ores

Info

Publication number: US1774786A
Application number: US161286A
Authority: US
Inventors: John M Callow
Original assignee: UNION CARBIDE SALES Co
Current assignee: UNION CARBIDE SALES Co
Priority date: 1927-01-15
Filing date: 1927-01-15
Publication date: 1930-09-02
Anticipated expiration: 1947-09-02

Description

Sept. 2, 1930. J. M. CALLOW METHOD OF ANDAPPARATUS FOR TREATING ORES Filed Jan. 15, 192'? 4 Sheets-Sheet 1 [[[MIIIIIIHW lNl/E/VTOR A TTOR/VEVS Sept. 2, 1930. J. M. CALLOW METHOD OF AND APPARA'TUS FORTREATING "ORES Filed Jan. 15, 192? 4 Shets-Shqet 2 J. M. C ALLOW METHOD OF AND APPARATUS FOR TREATING ORES Sept. 2, 1930.

4 Sheets-Sheet 3 Filed Jan; 15, 1927 INVENTOR:

l1 TTOR/VE VS J. M. CALLOW METHOD OF AND APPARATUS'FOR TREATING ORES Sept. 2, 1930.

Fiied Jan. 15, 1927 4 Sheets-Sheet 4 y I 3 4 m v ATTORNEYS.

Patented Sept. 2, 1930 UNITED STATES PATENT OFFICE JOHN m. CALLOW,.O F NEW YORK, N. Y., ASSIGNOB TO UNION CARBIDE SALES COMPANY, A ooRroRA'rIoN oruwEsT VIRGINIA Mari Ion or AND'APPARAT s FOR TREATING cans Application filed January 15,' 1927. Serial No. 161,286

It has been found desirable'to film certain crushed ores with acetylene during grinding and preparatory toi'roth flotation. By film ing with acetylene is meant bringing minsevere tei' means excess absor tion of acetylene by -the-water and, there ore, unnecessary exeral particles toa condition in which they are amenable to flotation. In easeof'copper ores, for example, the so-called oxid zed ores,

including carbonates *and silicates, require,

filming. These have been flotable when thus treated with acetylene. While various ways have been suggested and tried for this treatment, the most efiicientand practical method has been found to be the treatment of the ore I with gas during the'process of wet grinding. 'A common form of wet grinding mill is the conical ball mill frequently arranged in.

closed circuit with a classifier, 'in which the .discharge of the grinding mill is separated g into a finishedproduct, accompanied by a eci relatively large quantity of water, dischar ed by overflowing at one end of'the classi er, and intoasandy or coarse product, accompanied by a relatively small amount of water, discharged at the opposite end of theiclassi- :5 fier, the coarse or oversize product being returned to the mill forfurther reduction in 7 size. If the ore be treated with gaseous acetylene in the conventional installation wherein the mill is not gas-tight,- such treatment would be too expensive becauseof leakage of the acet lene and hazardous because acetye lenemixe with air is highly explosive.

It was'suggested that the'wet grinding might be done in batches-in a closed mill, but while this might be practical for the laboratory, grinding in batches is impracticable in the field because of the complications and consequent expense of introducing intermittent operations into what are.oth'erwise con- 40 tinuous. Any means for reducing the cost and'hazard of using acetylene must be simple, cheap'and adapted'for use with existing methods and apparatus. Experimental work disclosed that the oversize material to be re-.

7 turned to the grindin mill from the classifier would clog or cho e in anyform of pipe or conduitconnecting the two and adapted to maintain the mill gas-tight, as for example a U seal. A sump and pump were sug gested but the abrasive character of the materials and the small percentage of water a1- lowable rendered this apparatus impracticable; If water were added to makea freely flowing material capable of bein pumped objections would result. xcess wapense in gas required, and additional means for separating the water from the ore to be ground would be required. Alsouthe grind ing capacity of the mill isgreatly reduced when too much water is present, and if the mill is flooded the filming operation will not be as satisfactory as when gas can more read 1 ily contact with the ore, so that a small:

amount of water is desirable, the amount dea pending on the type of ore and other practical considerations, the customary density in the grinding mill varying from about 50% of water to ore down to about 30% of water to ore. Another diificulty has been in the necessity of feeding the material at varying rates as supplied from the classifier.

Also withball mills incontinuous operation the device must allow the introduction of new ballsto replace those worn out, without breaking the seal and allowing air to enter the mill or gas. to escape.

The art remained in this situation for some time, the advantages of filming ,with acetylene were realized but because of the practical difliculty of makingthe' operation economical and safe it was suggested that the:

application of filming with acetylene to the existing practice in mills be dropped. Under this invention these .difliculties have been overcome and a simple, safe, inexpensive means devised which is adaptable to existing apparatus.

According to this invention, the feedin of wet crushed ore into a substantially gas-tight enclosure is accomplished by shortening the feed passage because of the clogging tend-. ency and then making use of theclogging character of the material to form a substanthe same is advanced into the enclosure. pe-

cifically the means for doing this is located between discharge end of a classifier and an enclosing casing around the usual scoop on the feed end of a ball mill and comprises 'somemeans such as a feed screw capable of exerting pressure upon a gas-tight plugof this material formed in a short passage between the end ofthe screw and the gas-tight enclosure, the mill being made as-tight around'its bearings, etc. and the disc arge of the mill being arranged to take place below the water level in the classifier; To conserve acetylene, the overflow of the classifier may be subjected to a vacuum or any other separating treatment by which the absorbed gas or a portion-or all of the accompanying wa ter may be' removed from the ore and returned to the grinding mill for use overof the device in'Fig. 1;

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be ground, from a'crusher.

Fig- 3 is a right end view partly .in section of the device in Fig. 1; and

Fig. 4 shows a modified construction of the discharge from the screw feed.

Fig. 5 is a modified construction with the feed screw arranged at an angle.

Fig. 6 is another constructionwith the feed screw vertically disposed.

For purposes of illustration, the invention is shown in connection with a conical ball mill 10 in closed circuit with an inclined type classifier 11 as is common. For the sake of clearness, the mechanism for moving the material up the incline in the classifier has not been shown. The feed end of the mill is provided with a gas-tight casing 12 in which is located a eonventional feed scoop 13. A

feed screw 14 pushes the wet crushed material into the casing 12. above the feed screw receives, the coarse material discharged at the upper end of the classifier. Material is supplied to this closed circuit preferably to the portion'that is not gas-tight, as for example into the hopper 15 from the chute 29, receiving the material to The discharge from the mill is through the pipe 16 extending to below water level in the classifier. As illustrated, a convenient manner of attaching the discharge pipe .16, is a sheet metal housing 17 secured to onebearing and extended around the discharge from the mill, the pipe 16 being fixed to the 'end of the housing 17 by a gas-tight connection.

The water and fine material overflowing from the classifier maybe passed through a pipe 32, a thickener 33 or other separator and the excess water in whole or in part is preferably returned through a pump 34 and the

pipes

18, 19, 20 and 21 f0r use again in the mill 10 for addingsufiicient water to the ore at the entrance of passage 25 to submerge the A hopper 15 located ore and form the gas-ti ht plug, for c0nveying the crushed ore to t e classifier through the pipe 16, andfor adding water for other.

' 19, the hopper 15 and the screw 14 or through the pipe 20 to the housing 12 because enough water may not enter with .the feed, and again through the pipe 21 at the discharge end of the mill to prevent the discharged material clogging in the pipe 16 and at the same-time furnish the necessary dilution of the pulp as required for the proper operation of the classifier. A pipe 22 supplies'fresh water at the beginning of the operation, and the valves indicated enable this to be cut off and the water containing absorbed gas to be used Instead of rerunning the water sep'alater. rated from the finely ground finished product, all or a portion of it may be passed through the vacuum apparatus 23 in a spray or over the customarv baflies so that the acetylene may be drawn off through the pipe 35, compressed and returned through the pipe 24 for use in the mill. The acetylene is preferably supplied from the pipe 24 to the casing 12, the portion of the circuit between the feed screw 14 and the end of the discharge pipe 16 being substantially gas-tight. This may require that all bolts and packing be'carefully gone over to make the entiremill and easing substantially gas-tight. Instead of supplying acetylene in gaseous form, it may be generated within the apparatus by. feeding calcium carbide into the grinding chamber or enclosure as for example, with crushed ore through the hopper 15, but other suitable gastight supply means may be usedfor introducing the carbide, The use of carbide has an advantage over the introduction of gaseous acetylene in that the calcium hydroxide formed facilitates filming. This hydroxide or some other alkaline substance may be introduced with the ore to insure filming in the presence of alkaline material.

The feed screw 14; in the embodiment illustrated. is not provided with any bearing at the end adjacent the casing 12. A short substantially straight passage is left between the end of the screw 14 and the casing 12. It has been found that the tendency of the wet crushed ore to set or clog in this short straight passage is suflicient to form a substantially gas-tight plug between the screw 14 and casing 12 within the passage 25. In Fig. 4, a modified construction is shown for the passage 25, in which a tapered constriction 26 is placed in this passage for the purpose of offering a little more resistance to the movein the mill and casing may be partially withdrawn through the pipe 28, or a diluent such as nitrogen may be suppliedto 'reducethe hazard. ofoxygen presenti- With the feed screw arranged at an angle as in Fig.,5,;it"has been found that a more effective and gas-tight plug is formed with some ores. Preferably the plug seal and other details are similar to those previously mentioned; The constriction of Fig. 4 may be gsed with the feed passages arranged as in igs. 5 and 6. The vertical position for the feed screw inFig. 6 illustrates another embodiment of this invention, the other details being as described in connection with Fi s. 1;to'3.'

. mong the advantages of this invention may be enumeratedits simplicity, cheapness, and adaptability for use with existing types of apparatus, particularly to grindin mills. The use of the feed screw ermits a ditional balls to be'fed in with the material from the hopper to replace balls within the mill which have worn'out. The use of the rela-'. tive'ly short, substantially straight, passage is effective in combattin the clogging tendency of the material an yet this tendency is-present to an extent sufiicient to form the material into a substantiall gas-tight plug fitting with saidpassage. other ad vantage of this invention is that it is adapted to meet the needs of the irre lar rates of feed experienced in the field or it will be seen from Figs. 3, .5' and 6 of the drawings that even though the feed from the screw .14 be greatly reduced, the plug is still maintained within the passage 25. I

Nothing has been said about the exact size of feed material or precise amount of water to be supplied because these features have been found to be widely variable with the different types of ores treated. Of course, if the material from the-crusher is too coarse, it will not be effective in forming the plu desired in the passage 25, but experience wi soon show how small the material should be; That crushed to sizes of one-half inch hasbeen found generally suitable, although larger-sizes may, with some ores, be permissible, 1

if the coarse material of the classifier suflices to maintain an effective gas-tight plug.

What is claimed is:

1. The method of feeding crushed wet ore into a' substantially gas-tight enclosure,

.closure, feeding ore same is advanced, supplying water to the enclosure, grinding the carbide and wet ore 'which'comprises forming theore into a substantially gas-tight plug, pushing the plug into the enclosure, feeding said wet ore behind the plug, and compacting the feed to maintain the plug as the same is advanced.

2. The method of feeding crushed wet copper ore containing oxidized copper minerals into a gas-tight enclosure, which comprises compacting the ore beneath a liquid seal into a substantially gas-tight plug within a short passage, feeding the ore behind the plug, compacting the feed while building onto said plug, and pushing the same through said .passa e The method of feeding, copper ore concarbonate copper minerals into a gas-tig t enclosure, which comprises supplymgwater to the crushed ore, compacting the wet ore into a short gas-tight plug, feeding the wet ore behind said plug, compacting the feed while building'onto said plug, and pushing the plug into said enclosure.

4. The method of filming ore with acetylene which comprises grinding said ore in a substantially gas-tight enclosure in the pres 3. tainin ence of acetylene,- while feeding said ore into said enclosure in suchmanner as to preclude substantial leakage of acetylene from" or of oxygen into said enclosure.

5. The continuous method of filming oxidized copper ore that comprises feeding such ore-into a substantially gas-tight grinding chamber in such manner as topreclude substantial leakage of oxygen into said chamber or-gas therefrom; grinding such ore in said chamber in the presence of acetylene and continuously discharging ground ore from said chamber in such manner-as to preclude substantial leakage of oxygen into said chamber 'or of gas therefrom.

6. The method of filming crushed wet ore with acetylene'which comprises forming the ore into a substantially gas-tight plug, pushing the plug into a substantially gas-tight enclosure, supplying calcium carbide tothe enbehind said plug as the within said enclosure, and discharging the ground filmed ore below the surface of a liquid seal;

lot

7. The method of filming crushed ore with I acetylene Which-comprises forming the ore into a substantially gas-tight plug, pushing the plug. into a substantially gas-tight en-.

closure, feeding ore behind the plug, compacting the feed to "maintain the plug as the same is advanced,- wetting the ore, grinding the wet ore within said gas-tight enclosure in the presence of acetylene, and discharging the ground filmed ore below the surface of a liquid seal.-

8. The methodof filming crushed wet ore with acetylene in a substantially gas-tight grinding mill", which comprises supplying 10. The method of filmingcrushe d wet ore with acetylene in a's ubstantially gas-tight grinding mill, which comprises supplying water to the mill, separating water from solid particles in the mill discharge, withdrawing absorbed acetvlenc from at least a portion of the separated water under reduced pressure, compressing the acetylene, and recycling the same through themill.

11. The combination with a substantially gas-tight enclosure, of means for feeding crushed oreinto said enclosure, which comprises a short substantially straight passage leading into the enclosure, means for wetting the ore before entering said passage, means for compacting the wet ore to form a substantially gas-tightplug within said passage, means for pushing the plug through the passage into the enclosure, means for feeding ores behind said plug, and means for compacting the feed to build onto and maintain the plug as the material is moved through said passage. v

12. The combination With-a substantially gas-tight grinding mill, of means for feed ing crushed ore into said m'ill'while maintain ing the mill gas-tight, means for supplying water to said mill, means for maintaining acetylene within the mill, discharge means for the mill, and a liquid seal on the discharge means from said mill.

13. The combination with a classifier, of means to enclose said classifier so as to prevent the escape of gases therefrom; a substantially gas-tight grinding mill'in closed cir cuit, with said classifier, means for feeding material to said circuit, a substantially gastight enclosure at the feed end of-said mill,

means for raising material within said 0l1' closure, feeding the same to said mill, and

' means for feeding thecoarse material discharged from said classifier; into said e11- closure 14. The combination with a classifier. of means to enclose said'cl'assifier so as to prevent the escape of therefrom,'assuhstantially gas-tight grinding mill in closed circuit with said classifier, 1neans for feeding crushed wct'ore into said mill. means for maintaimng acetylene 1n said mil], means for supplying water to the mill, means for dis-- charging the material from said mill below the water level in said classifier, and means for. recycling at least a portion of the water containing absorbed acetylene, through the mill.

15, The combination with a substantially gas-tight enclosure, of a screw for feedingmaterial thereinto, a short substantially straight passage between said screw and enclosure, and having a tapered constriction therein for compacting the material.

' 17. The combination with a substantially gas-tight enclosure, of a screw for feeding "material thereinto, a. short substantially straight passage between said screw and enclosure, and an agitator to break up the material at the discharge end of said passage.

18. An ore filming device which comprises agas-tightenclosure which includes a mill capable of grinding ore in the presence of a film-producing gas, a passage to introduce ore into said enclosure, means in said passage to form a seal at the feed-end of said enclosure, gas-tight means to separate ore discharged from said mill, and a gas-tight connection on said mill and separator for discharging the contents of said mill and for conducting the same to the separator.

19. An ore filming device comprising a gastight enclosure for grinding ore in the presence of a film-producing gas, feeding means to introduce ore into said enclosure, means to form a seal in said feeding means, a gas tight means to separate coarse aggregates of ore and to return the same to the feeding means, and means to separate gas-charged water from the ground ore and to return at least a part of said water to the feeding means.

520. The combination with a classifier having meansto discharge finely ground ore and means to discharge coarse aggregates of ore, of means to enclose said classifier so as to retain gases therein, a feed pipe for said classitier, an air-tight enclosure including a grinding mill and a chamber, the discharge of said mill being connected-with the feed pipe of said classifier, scoop means in said chamber to feed ore to said mill, and means between the discharge for coarse aggregates and the chamber to form a plug of ore and continuously advance the same into the chamber.

In 'testimony whereof, I allix my signaturc.

' 1 JOHN M. CALLOVV.