US3497142A

US3497142A - Autogenous grinding process and mill systems

Info

Publication number: US3497142A
Application number: US781670*A
Authority: US
Inventors: John E Nelson
Original assignee: Dominion Engineering Works Ltd
Current assignee: Dominion Engineering Works Ltd
Priority date: 1968-10-10
Filing date: 1968-10-10
Publication date: 1970-02-24
Anticipated expiration: 1987-02-24

Description

Feb. 24, 1970 J. E. NELSON 3,497,142

AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS 7 Original Filed Sept. 20, 1963 4 Sheets-Sheet 1 lllllllllllllllllllllll PRODUCT INVENTOR. JOHN E. NELSON TTOPNL'Y.

Feb. 24, 1970 J. E. NELSON 3,

AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS Original Filed Sept. 20, 1963 4 Sheets-Sheet 2 mlllllllll PRODUCT INVENTOR.

JOHN E. NELSON A TOPNEX Feb. 24, 1970 J. E. NELSON AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS Original Filed Sept. 20, 1963 4 Sheets-Sheet 5 llmlmlllll llllllllllll TRODUCT INVENTOR. JOHN E. NELSON GPA/E)? Feb; 24, 1970 J. E. NELSON 3,497,142

AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS Original Filed Sept. 20, 1963 4 Sheets-Sheet 4 IIIIIIIIH- PRODUCT 5 INVENTOR.

JOH N r; NELSON United States Patent 3,497,142 AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS John E. Nelson, Montreal, Quebec, Canada, assignor to Dominion Engineering Works, Limited Continuation of application Ser. No. 310,271, Sept. 20, 1963. This application Oct. 10, 1968, Ser. No. 781,670 The portion of the term of the patent subsequent to Oct. 17, 1935, has been disclaimed Int. Cl. 1502c 17/02, 7/00; B07b 13/00 US. Cl. 241-24 4 Claims ABSTRACT OF THE DTSCLOSURE Concentration of sizes of material in mill components of a grinding mill system for grinding run-of-r'nine mate- 1 This is a continuation of application Ser. No. 310,271, filed Sept. 20, 1963, now abandoned.

This invention relates to autogenous grinding mill systems or apparatus or the like and has particular reference to the provision of a new and improved autogenous grinding mill system of the type in which coarse, friable, runof-mine material is subjected to self-reduction, and of a process for the removal of material of desired size from the remainder of said coarse, friable material prior to the time that such is fed into the grinding mill.

As used herein, the term autogenous shall mean the use of a friable material undergoing reduction, either in whole or in part, as its own grinding media. The term run-of-mine material, as used herein, shall mean a mixture of friable material, which mixture normally includes coarse, intermediate, and fine sizes, the larger sizes being sufficient to effect self-reduction and reduction of the smaller sizes present in the mixture. The term ebble milling, as used herein, shall mean the use of screened fractions of the friable material in the coarse range, as media, for the grinding of the finer sizes of the same material.

conventionally, when a product much finer than about 10 mesh is required, it is, generally, not practical to produce such product in a single mill which is being fed with run-of-mine ore. Thus, conventionally, when a finer product than about 10 mesh is required, it is usually necessary to first produce an intermediate sized product from one grinding mill, and then to further grind this product in an additional mill, or additional mills as the specific case may require, using the pebble milling process.

conventionally, the pebbles necessary for this pebble milling process are obtained either from the charge within the first or primary mill, through suitable ports, or from the discharge of said first mill by means of auxiliary apparatus.

Said conventional processes for the removal of the pebbles, however, possess certain severe inherent disadvantages and deficiencies.

In the first place, should the necessary pebbles be removed from the charge within the first mill by means of suitable ports, material of sizes other than that desired for use either as pebbles or as the primary mill product 3,497,142 Patented Feb. 24, 1970 is obtained; such making the provision of auxiliary apparatus necessary for the required separation of the unwanted fractions of said material and either the returning of such to the primary mill or the separate treatment of such elsewhere. Furthermore, in the use of the port process, a further disadvantage arises from the difficulty in adjusting the port size and area to match the, generally, constantly changing requirements of the pebble mills.

Should the necessary pebbles be obtained from the discharge of the first, or primary, mill, a range of size of material even greater than that obtained through the use of the port method is obtained; said greater range of size of material leading to even greater problems in its higher demands for the separation and return of unwanted material. Thus, in brief, both of these conventional methods for obtaining the pebbles necessary for the pebble milling process are unsatisfactory in practice.

An object of the invention is to provide a new and improved process and apparatus of the type set forth which includes the removal of the desired pebbles prior to the feeding of such into the first, or primary, grinding mill.

Another object of the present invention is to provide a new and improved process for the provision of pebbles for the pebble milling process, which new and improved process is simple and economical in operation.

Another object of the invention is to provide a process and apparatus of the type set forth which includes a provision for the supply of a sufiicient quantity of suitable pebbles even should the run-of-mine material itself, not include such suificient supply.

Another object of the invention is to provide a process and apparatus of the type set forth which enables pebbles of sizes other than that desired for said pebble milling process to be removed from the run-of-mine material prior at the same time as the pebbles necessary for said process are removed from said run-of-mine material.

Another object of the invention is to provide new and improved means for the accomplishment of the foredescribed process.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings. It will be understood that changes may be made in the details of construction and arrangement of parts shown and described as the preferred forms of the invention have been given by way of illustration only.

Referring to the drawings:

FIG. 1 is a schematic view of an apparatus for the production of a ground product from run-of-mine material through the use of a primary autogenous mill and a secondary pebble mill;

FIG. 2 is a schematic view of an apparatus similar to that of FIG. 1, but which system is adapted to function when insuificient pebble sized material is present in the run of mine material;

FIG. 3 is a schematic view of an apparatus similar to those of FIGS. 1 and 2, said system being adapted to remove from the run-of-mine material, in addition to those pebbles of correct size for the pebbling process, those pebbles of a size larger; and

FIG. 4 is a schematic view of an apparatus similar to that of FIG. 3, but which system is adapted to remove pebbles of a size smaller than the desired size in addition to those of the desired size.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, and with particular reference to FIG. 1 of the drawings, such illustrates a system for producing a ground product from run-of-mine material through the use of a primary autogenous mill and a secondary pebble mill.

The apparatus employed as shown in FIG. 1 comprises a bin adapted to contain run-of-mine material or ore, feeder 11 which conveys such material to the separation devices or

screen

12 and 13.

The apparatus also includes primary mill 14, pebble mill 16 and volume or quantity control means 15.

Primary mill 14 has discharge 17 which is connected to the inlet of pebble mill 16.

In the process of the present invention and operation ot the apparatus shown in FIG. 1, run-of-mine ore from the bin 10 is transported by the feeder 11 to the dual separation devices which comprise the screens or

grisslys

12 and 13.

Said dual separation devices are chosen for any particular application of the system such that said separation devices are at the upper and lower limits of the size pebbles that are required. Thus, assuming for the purposes of example that a pebble size minus 3 inches, plus two inches has been established, the first separation device or screen 12 would be chosen such as to be operative at three inches and the second separation device or screen 13 would be chosen such as to be operative at two inches.

In the embodiment of the system illustrated in FIG. 1, the plus three inch material joins with the minus two inch material for feed to the primary mill 14. The minus three inch-plus two inch pebbles, on the other hand, are transported through the suitable volume controlling means 15 to the pebble mill 16, any excess in said minus three inchplus two inch material being fed to the primary mill 14. The primary mill discharge which is shown generally at 17 is delivered to the pebble mill 16.

The mill apparatus and process, as illustrated in FIG. 1 and foredescribed, is adapted for application where the run-of-mine material contains a sufficient quantity of pebbles of the size required for the pebble mill; and where, also, it is neither necessary nor desired to remove certain fractions of the primary mill feed in order to maintain a suitable charge equilibrium within that mill.

With reference to FIG. 2 of the drawings, such illus trates the process of the present invention and the apparatus required where insufiicient pebble size material is present in the run-of-mine ore. In such case, a second withdrawal point 18 from the bin 10 is provided in order that a quantity of the ore contained in said bin sufficient to produce the additional required material of pebble size may be provided to the system by means of the jaw, gyratory, or other suitable crushing device 20, which crushing device 20 has been set to produce pebbles of the desired s1ze.

The discharge 21 from said crushing device feeds the ore crushed by said crushing device into the mainstream of the ore passing through the

dual separation devices

12 and 13.

The process and apparatus of FIG. 2 is particularly adapted for applications where it is neither necessary nor desirable to control the primary mill 14 charge equilibrium by the removal of sizes of material other than that required for the operation of the pebble mill 16 before the admission of said material into the primary mill 14. However, if a moderate excess in capacity be produced by the crushing device 20, some degree of control of the larger sizes of material may be obtained through the operation of said crushing device at a larger setting and greater tonage than is required for the production of the pebble size material alone.

With regard to the process of the invention and apparatus illustrated in FIG. 3, such is particularly adapted for application where, in addition to the removal of pebbles of the proper size for the pebble mill, the removal of material of a size larger than said pebble size is necessary in order to maintain a satisfactory equilibrium within the primary mill 14.

In such case, a third separation device 22 is added to

separation devices

12 and 13 and

quantity control devices

23 and 24 are provided in order that the crushing device 20 can be fed the oversize from either or both of the

separation devices

22 and 12, any excess in such joining With the excess of pebble size material and the underflow from separation device 13 for the feeding of the primary mill 14.

By way of example, assuming that minus three inchplus two inch material is required for the pebble mill 16, and, further, that material in the size range of minus six inch-plus three inch should be reduced, the

separation devices

22, 12, and 13 would be set at six inches, three inches, and two inches, respectively.

With regard to FIG. 4 of the drawings, the process and apparatus illustrated therein is particularly adapted for application where production of pebble size material is desired and, in addition, where material a size fraction smaller than pebble size must be removed and separately treated in order that the primary mill 14 maintain optimum charge equilibrium.

In such case, a third separation device 25 is added to the screening system, said separation device 25 being set for a size smaller than those pebbles required for the operation of the pebble mill 16. The oversize material from said separation device 25 is transported by way of a suitable quantity control device 26 to a comminuting device such as a crusher, rod, ball, or other suitable type of mill 27 for reduction before return to the operative portion of the system.

In this illustrated form of the system, it is assumed that one stage of crushing will sutfice, after which crushing, the crushed product can be fed into the autogenous primary mill 14. However, in some cases, it may be preferable to treat the oversize from the separation device 25 in a rotary mill, or mills, and to deliver this product either to the primary mill feed, pebble mill feed, or finished product.

By way of specific example, assuming that minus three inch-plus two inch pebble is required for the pebble mill 16, and that pebbles less than two inches to more than one inch should be treated, the three screening or

separation devices

12, 13, and 25 would separate at three inches, two inches, and one inch, respectively.

In addition to these four processes and apparatus which have been foredescribed, it is believed to be readily apparent that many variations of said systems are possible. By way of example, the crushing device or devices, primary and secondary mill or mills can be close circuited with the appropriate screen, classifiers, cyclones, and the like as may be desired.

The operation of the process and apparatus herein provided is believed to be apparent from the foregoing description.

What I claim as new and desire to secure by Letters Patent 0f the United States is:

1. The method of operating a grinding mill system having an autogenous mill for grinding run-of-mine material and a pebble mill for providing further reduction of the material including the steps of; (1) extracting by sorting at least a portion of a predetermined range of size of pebble material from said run-of-mine material prior to entry of the material into said autogenous mill to control the size range of the input to the autogenous mill; (2) passing the residue of said run-of-mine material to the autogenous mill together with any excess of extracted pebble material, for reduction by grinding; -(3) passing at least a portion of the output of the autogenous mill to said pebble mill for further reduction therein; (4) and supplying a sutficient portion of the extracted pebble material, to said pebble mill to maintain satisfactory grinding therein, whereby operation of the system is promoted and the build-up of undue quantities of intermediate size material is controlled.

2. The method of claim 1 including the step of crushing a portion of the run-of-mine material prior to said extracting by sorting step, to provide an increased quantity of pebble size material.

3. The method as claimed in claim 1 including the steps of extracting by sorting a portion of said run-of-mine material of a size exceeding a predetermined pebbling size, reducing said portion by crushing to provide additional pebble material, and returning said portion for said sorting step, whereby material larger than pebble size is removed to maintain a desired equilibrium within said autogenous mill.

4. The method as claimed in claim 1 including the step of extracting by sorting at least a portion of material of a size less than a predetermined pebbling size, reducing said portion by comminuting apart from the residue, and returning the reduced material for further milling.

ROBERT C.

References Cited UNITED STATES PATENTS RIORDON, Primary Examiner 10 D. G. KELLY, Assistant Examiner US. Cl. X.R.