US3231204A

US3231204A - Beneficiation means and methods for autogenous grinding systems

Info

Publication number: US3231204A
Application number: US229288A
Authority: US
Inventors: Le Roy C Ferguson; Hardinge Harlowe
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1962-10-05
Filing date: 1962-10-05
Publication date: 1966-01-25
Anticipated expiration: 1983-01-25
Also published as: BE638271A; SE310345B; GB995114A; FR1376790A

Description

1965 LE ROY c. FERGUSON ETAL 3,231,204

BENEFICIATION MEANS AND METHODS FOR AUTOGENOUS GRINDING SYSTEMS Filed Oct. 5, 1962 2 Sheets-Sheet 1 INVENTORS L E ROY C. FERGUSON HARLOWE HARD/NEE- ATTORNEY (v Q 1966 LE ROY c. FERGUSON ETAL 3,23

BENEFICIATION MEANS AND METHODS FOR AUTOGENOUS GRINDING SYSTEMS Filed 001:. 5, 1962 2 Sheets-Sheet 2 N mil I IIIJI T INVENTORS LE ROYC. FERGUSON W D! N G E United States Patent 3,231,204 BENEFICHATION MEANd AND METHQDS FOR AUTOGENOUS GRINDING SYSTEMS Le Roy C. Ferguson, Hibbing, Minn, and Harlowe Hardinge, York, Pa, assignors, by mesne assignments, to Koppers Company, Inc., Pittsburgh, Pa, a corporation of Delaware Filed Get. 5, 1962, Ser. No. 229,288 30 Claims. (Cl. 241-24) This invention pertains to improvements in an autogenous grinding system in which the means and methods of operating the same is such as to cause beneficiation of at least one component of the material which is being ground autogenously in the mill and which material, preferably, is supplied to the mill in run-of-mine condition. More particularly, the invention pertains to such a system, and method of operating the same, in which the beneficiation or treatment of the material undergoing reduction can be applied to an appreciable range of sizes of the material undergoing reduction, autogenously, in the mill.

Autogenous grinding or reduction of ore materials of .a friable nature, as the name implies, comprises the utilization of the material undergoing reduction as its own size-reducing grinding media. Run-of-rnine material, which is the form in which the raw material preferably is utilized in accordance with the present invention, includes intermixed ranges of relatively coarse, medium and fine size ranges of material. In accordance with the principles of the invention, it also is contemplated that such run-of-rnine material may have been subjected to as least limited precrushing treatment in order to produce a maximum coarse size of the range usually between 5 inches and 12 inches diameter, these sizes not being intended as restrictive but merely as somewhat illustrative. The addition of other media such as balls, usually in a small amount, is also contemplated. For a comprehensive discussion and explanation of autogenous grinding, attention is directed to co-pending application, S.N. 822,612, filed June 24, 1959, in the name of Harlowe Hardinge, now Patent No. 3,078,049, issued Feb. 19 1963. This invention is also contemplated for use in either a so-called wet or dry circuit.

When operating a tumbling mill to perform autogenous grinding of run-of-mine material, it can be appreciated that various types and conditions of raw material will be fed to the mill over extensive periods of time, especially as the mill receives material from. different locations in a mine, for example, or from different mines, pits or quarries. Under such circumstances, it can be appreciated further that the mill can contain an excessive amount of medium sizes of material, for example, over the proportion which is desired normally for most etfective autogenous grinding. For the sake of example only, and by no means to be considered as a size limitation, coarse material may be assumed to be between 6 inches and 3 inches in diameter, medium between 3 inches and /2 inch, and fine /2 inch down to 35 mesh. In practice however, this invention encompasses a range of sizes after leaving the mill in the order of approximately 5 inches down to approximately plus 35 mesh.

Variations in size ranges depend upon the characteristics of the material being treated and objectives sought. Depending upon the type of material being handled by the mill at any given time, there usually is a preferred optimum proportion of intermixed size ranges of relatively coarse, medium and fine materials. If for example the medium size fraction of the mill charge exceeds the desired proportion of said size range to any substantial extent, the eficiency of the grinding operation becomes impaired.

Not only is the etliciency of the grinding operation impaired if any of such coarse, medium or fine size ranges becomes unduly excessive, but the amount of work necessary to be performed by the mill is greater than should be necessary if the proportions of these various size ranges is such as to effect optimum grinding conditions. It can be appreciated still further, that if an excessive fraction of medium sizes, for example, exists in the mill and a substantial portion of such sizes are Waste matetrial, greater efficiency could be achieved if this waste material can be removed from the mill at a desired rate commensurate with grinding efficiency, especially to decrease the burden upon the mill. The same circumstances might pertain with respect to the coarse size ranges, as well as to the finer size ranges. The finer size ranges in this regard are those generally still coarser than material which may be classed as a finished product.

Under other autogenous grinding conditions, Where an ore is relatively rich in the values desired to be obtained and further processed in one way or another, and particularly if such medium size fractions, for example, of the material are appreciable in amount, there is no need further to reduce in size such medium size fractions and if these medium size fractions, or at least a substantial portion thereof, are removed from the mill in this condition, the power requirements of the mill can be decreased. Further, such richer and more concentrated forms of the value material frequently experience loss in recovery if reduced to too fine a size, where it is beneficial to remove such size fractions of high value material from the mill with as little grinding thereof taking place as possible.

One of the principal objects of the present invention is to provide both a mill system and methods of operating the same by which run-of-mine material is subjected to autogenous grinding in a tumbling mill and a sized portion of the load within the mill is removed therefrom and separately treated, said sized portion which is considered as being too coarse for proper beneficiation thereof is returned to the mill for further autogenous grinding, such further reduced material subsequently being discharged from the mill in a smaller size range either for further treatment within the milling system or discharged as a finished product.

Another object of the invention is to remove from the products discharged from an autogenous grinding mill a fraction thereof which is treated outside of the mill and a component, such as a desired sized fraction of the thus treated material is then returned to the mill for further reduction in size, the means employed for treating the material while outside of the mill preferably being capable of handling only a limited portion of the total amount of such size range of the material normally contained in the mill, yet eventually and effectively treating such size ranges of material as it circulates through the autogenous milling system, thereby reducing the cost and maintenance of such a treatment step.

A further object of the invention is to treat run-ofmine material having a plurality of characteristics during the reduction stage thereof in an autogenous milling system and which material containsone or more components having different grindability and hardness characteristics, such treatment comprising removing from the mill system, as soon as economically expedient during the milling process, a portion of the material respectively classifiable as tailings, concentrate, completely treated material, or material to be designated for additional treatment, and appropriately treating that material which is removed from the system according to the values therein.

Still another object of the invention, ancillary to the foregoing further object, is to provide means to select a component undergoing treatment for use as grinding media J in another grinding milling circuit, and feeding such selected treated components to such latter milling circuit.

A still further object of the invention, in conjunction with the treatment of run-of-mine material as it is being reduced autogenously in a tumbling mill, is to remove a sized component, divide the same quantitatively, return one of said divided portions to the autogenous mill for further reduction, and treat another of said divided portions to separate therefrom a component having desired characteristics, the dividing of said discharged size portions preferably being adjustable.

Still another object of the invention in conjunction with the foregoing is to provide various kinds of dividing mechanism at selected locations in the mill system, all of said dividing mechanisms preferably being of an adjustable nature and arranged to direct certain divided portions of the material to a selected treating apparatus to perform further desired operations upon the divided material before discharging the same from the mill system.

Details of the foregoing objects and of the invention, as well as other objects thereof, are set forth in the following specification and illustrated in the accompanying drawings comprising a part thereof.

In the drawings:

FIGS. 1 and 2 respectively are vertical sectional elevations respectively transverse and parallel to the axis of an autogenous tumbling mill and illustrate exemplary arrangements of run-of-mine material therein as the same undergoes reduction during tumbling in the mill, said mill having exemplary discharge means for certain size ranges of the material undergoing reduction.

FIG. 3 is a fragmentary vertical sectional elevation illustrating an embodiment of material segregating means mounted relative to the discharge end of an autogenous grinding mill.

FIG. 4 is a fragmentary illustration of an end view of a mill discharge means and showing further treating units and dividing mechanism for the mill system otherwise illustrated generally as in FIG. 3, the view in FIG. 4 at least partially being a vertical sectional end elevation of the mill discharge mechanism illustrated in FIG. 3.

FIG. 5 is a fragmentary illustration similar to the upper part of FIG. 4 and comprises the mill discharge and taken on the line 5-5 of FIG. 3 and showing another component adjacent the mill discharge end.

FIGS. 6 and 7 are fragmentary sectional elevations of two additional embodiments of mill contour according to the invention.

Inasmuch as the mill system and process comprising the present invention pertain principally to the employment of a tumbling mill of the autogenous grinding type for performing at least the initial simultaneous reduction in size of all size ranges of run-of-mine material, there is illustrated in FIGS. 1 and 2, an exemplary autogenous mill ill. For a compete description of the operation of this type of mill and the process performed thereby, attention is directed to aforementioned co-pending application, S.N. 822,612, filed June 24, 1959, now Patent No. 3,078,049, issued Feb. 19, 1963. For convenience however, the following brief description of the operation of the mill and the process performed thereby is set forth.

The autogenous mill It? comprises a drum 12 having opposite ends 14- and 16 respectively provided with trunnions 18 and Eli which are rotatably supported in suitable in suitable bearings, not shown, the mill being rotated by conventiona power means, not shown. The trunnions 18 and Zll are hollow and respectively comprise inlet and exit means for the mill. A feed chute 22, which receives run-of-mine material from an appropriate conveyor or the like, discharges into the mill through trunnion 18, while exit trunnions 29 contains discharge cone 24-. The specific shape of the mill is not a critical aspect of this invention, neither as to the feed or discharge ends nor the specific proportions of the interior dimensions thereof.

The interior of the mill is provided with suitable lining means of a conventional nature and, overlying the same, are radial lifter bars 26 which are carried by entrance end 14 of the mill, while preferably sectional type radial lifter bars 28 are connected detachably to the exit end 16 of the mill. In the preferred construction, the lifter bars 28 secure grate sections 39 of segmental shape in spaced relationship to the exit end 16 of the mill as thus shown in FIG. 2. An annular discharge space 32 is formed between the exit end 16 of the mill and the grate 3G to receive material which is capable of passing through the slots or other size-limiting opening means formed in the grate 3Q, exemplary arcuate grate slots being shown in FIG. 1. It should be understood, however, that such illustration is not to be regarded as restrictive as to size arrangement or Width of said slots. Curved, generally radial lifting vanes or scoops 34, which are circumferentially spaced from each other, are provided in annular space 32 for purposes of elevating the material discharged into the space, as the mill rotates, whereby when the elevated material rises above the axis of the mill, it will fall by gravity into discharge cone 24 for exit from the mill.

One of the principal advantages of a mill of this type is that the radial lifter bars 25 and 28, in conjunction with the transverse lifter bars 36, will elevate the material to a substantial height within the mill before the same cascades in a manner as illustrated in exemplary form in MG. 1. The exemplary position of the material in the mill will be somewhat as indicated by the irregular upper boundary line 38 thereof which is shown in FIG. 1. The mass of material undergoing reduction in the mill will consist of various size ranges of relatively coarse, medium and fine material and the cascading of the material serves to reduce all size ranges of the same simultaneously.

As illustrated in exemplary manner in MG. 2, particularly in regard to the coarse pieces 4t there is substantial transverse movement in a generally axial direction Within the mill due to various elements therein such as annular deflector rings 42, the sloping surfaces 44 of the peripheral liner of the mill as shown in FIG. '2, the convex nature of the ends 14 and 16 of the mill when such shape of mill is employed, the

radial lifter bars

26 and 28 which also act at least somewhat as deflector means. Such transverse movement of the material, comprising all size ranges thereof, further facilitates the grinding action afforded by the mill. A mill, such as shown in detail in FIG. 2, in which the diameter of the grinding zone is substantially greater than the axial length thereof, also aids in the mixing action which occurs in said zone. For further details of the reasons and benefits of this characteristic of the grinding zone, attention is directed to aforementioned Patent No. 3,078,049.

Autogenous grinding of run-of-mine material, as indicated above, varies as to optimum elliciency in accordance with the available proportion of relatively coarse, medium and fine size ranges of the material, variations in the harness of the material, variations in the values content within specific pieces or fragments of material, whether the grinding operations are under wet or dry conditions, and various other factors well known to those familiar with autogenous grinding.

One purpose of the present invention is to counteract certain disadvantageous conditions or circumstances in regard to grinding autogenously run-of-mine material, especially for purposes of insuring as far as possible optimum grinding conditions within the mill, and thereby effecting maximum economy from the standpoint of minimizing wear and consumption of power, coupled with maximum percentage of desired product produced by the autogenous grinding mill and system.

Another important purpose is to increase recovery of the values in the material, as more fully described hereafter. In order to accomplish these objectives, the present invention provides an autogenous grinding mill pound type of trommel, broadly indicated 46.

circuit and system in which the material progressively is reduced in size within the mill and all of the size ranges thereof which are capable of passing through the size-limiting opening means of the grate 30 will be discharged into the space 32 and from there, through discharge cone 24, into sizing means 56 shown in FIG. 4. In addition to the material which passes through the openings of the grate 30 however, there also is provided, in accordance with the principles of the present invention, additional discharge openings 48 for permitting passage of medium size pieces which in the mineral dressing industry are referred to as pebbles or cobs, the number and placement of openings 43 preferably being variable. These pebbles or cobs are designated 59, in exemplary manner, in FIG. 2 and certain of the subsequent figures and references.

The spaces 13 through which the pebbles 51) exit from the grinding zone of the mill may comprise portions of the radial spaces between segmental edges of the grate sections 31) for example. The extent and position of the discharge openings 48 is determined, for example, by the placement of the sections of the sectional type radial lifter bars. 28 and particularly by the omission thereof at various locations within the mill. One of the preferred positions for the discharge openings 4-8 however is adjacent the periphery of the discharge end of the mill 1t and a number of such exemplary openings 48 are shown in FIG. 1. 'It will be understood further, also,

that a certain amount of intermediate size ranges of material of a lesser dimension than the maximum permitted to pass through the openings 43 also will exit therethrough and be discharged from the mill but any such sizes of material so discharged will be classified and sized appropriately by mechanisms and procedures described hereinafter. For a more complete description of this aspect of the treatment of the material, attention is directed to co-pending application, SN. 1291, filed January 8, 1960, in the name of Harlowe Hardinge, now Patent No. 3,078,050, issued February 19, 1963.

As to the extent of the discharge openings 48, it will be seen that, at least in accordance with the preferred condtions contemplated for the mill, the openings 48 will be minor in proportion to the total discharge areas adored by the openings in the grate sections 30, whereby only a limited proportion of such larger pieces or pebbles 50 will be discharged from the grinding zone of the mill in comparison with the volume of relatively fine size ranges of material discharged through the openings of the grate 39.

The pebbles or cobs 5d which are discharged from the grinding zone of the mill may, for example, be of a size range between 3 inches and 1 inch, Whereas another sized range material may, for example, be between 1 inch and 10 mesh, the fine ranges of material being, for example, minus 10 mesh and finer. It will be understood however that these designations are for purposes of illustration only, rather than being restrictive in nature and suitable variations are contemplated as herein above stated.

Several different types of material classifying and segregating means are contemplated by the present invention, the numeral 12' being used generically to designate all of such various embodiments thereof in the several figures of the drawings. While a trommel arrangement is here illustrated, the use of separate sizing devices such as a multi-deck vibrating screen capable of making a number of size separations will be a preferred arrangement under many conditions.

Referring to FIG. 3, it will be seen that the discharge cone 24 of the mill 11) has associated therewith a com- Concentric screens or bar-

type trommels

104 and 106 are connected to the exit end of mill 1% and are rotatable therewith. The inner trommel 1114 is relatively coarse, while the outer trommel 106 is relatively fine, the latter permitting the passage therethrough of relatively fine size ranges of material 1138, which discharges into a conduit 110 and may be removed from the mill system as a finished product if the nature of the material is suitable. As to an example of the size of the material 108, the maximum particles therein may be in the range of minus 10 mesh or even 35 mesh approximately. This however is subject to variation due to the character of material treated as well as product desired.

The classifying and segregating means 46, by reason of the use of coarse trommel 104, is capable of separating from the exemplary coarse pieces or pebbles 50 an intermediate size range of material 112 which passes through trommel 104 but will not pass through sieve or trommel 106. As to an example of the intermediate size material r 112, and subject to modification as stated herein, it can be,

for example, plus 10 mesh and minus 1 inch, the same discharging into an appropriate chute and conduit 114, and subject to division by splitter 116' as later explained.

The coarse fraction of material, comprising pebbles 5t}, discharges from the outer end of the inner trommel 104 into the upper end of chute 114 which contains an other pivoted splitter 116 disposed between an inner wall 118 and the outer wall 120 of the chute 114, the inner wall 118 merging with a pair of

discharge chutes

122 and 124 which are best shown in FIG. 4.

The intermediate size material 112 is handled at this point similarly to the pebble material 50 and is illustrated in FIG. 5 which is a section, viewed on the line 5-5 of FIG. 3, and in which the splitter 116' is independent of splitter 116 shown in FIG. 4, although they are in the same discharge hopper 114, but are separated by inner wall 118 into separate discharge chutes 122 and 124' as shown in FIG. 3.

The handling of materials of the type treated in the present invention is best accomplished by limiting the size range of the material to be treated. The same method of treatment does not usually apply to diiferent size ranges, or the apparatus employed for the different ranges may require different adjustment for efiiciently handling one size range from another, as is well known in the art. For this reason provision is made to divide the mill 10 product into different size ranges for delivery thereof to different apparatus. An example of this method for dividing the size ranges into three components is exemplified by the multiple trommel means of FIG 3, and is further illustrated relative to an overall mill system in FIGS. 4 and 5.

In accordance with the principles of the invention, it is principally the so-called medium and near fine size ranges comprising for example pebbles 50 and intermediate sizes 112 that are to be beneficiated or treated in mill 1t) and the system included therewith. When a wide range of sizes such as exemplified above are to be treated, it is advisable in many cases to divide the ranges into size limiting components. Two such general sizes of components are illustrated here but it is within the scope of this invention to add additional size limiting or segregating means in a similar manner, if desired, or confine the operation to one selected size range if advisable.

Referring to FIG. 4, a picking belt 64 is shown in the mill system to receive the coarse size range of material comprising pebbles 50 and the like, the same having been discharged thereonto from suitable, diagrammatically illustrated adjustably positionable guide mechanism 125, or the like, to render the material suitable either for hand picking, or to transmit the same to a magnetic separator 66 of a pulley type, for example, well known in the art. A pair of chutes or hoppers 126 and 128 are shown in side-by-side relationship therein, each of the same having a

splitter

130 and 132 respectively, for purposes to be described.

The guide mechanism may be positioned, for example, to direct the coarse fraction of material by appropriate means such as conduit 80, to a heavy media separator 82. One example of this type of separator is illustrated in prior Patent No. 2,753,998, in the name of Harlowe Hardinge. Briefly, such seperator comprises a slowly rotating cylinder 82 containing liquid 86 which usually is fortified by fine, heavy solids floating therein, of such a consistency that the specific gravity of the liquid approximates that of the material to be separated, whereby the lighter portions of said material tend to float and are discharged at outlet 88, while the heavier portions sink and are delivered to the opposite end it? by spiral flights 92 within the cylinder. Suitable buckets are provided within the end 9G which discharge into exit chute 94.

An auxiliary divider or splitter 132 is shown adjacent the exit chute 94 of the separator 82, and is operable to direct the heavy media material into any one of a number of conduits or the like, to be described hereinafter. The guide mechanism 125 also may be set to direct the coarse range of material to the exemplary unit 36 comprising supplementary beneficiating or treating means of any one of a number of different types and from which the products may exit to one of several different possibilities to be described hereinafter.

Regarding discharge conduit 124, it preferably discharges into a dividing or splitter mechanism 134 capable of directing the material from conduit 124 into one of several channels, respectively for the following exemplary purposes. The material discharged into

conduits

122 or 124 may, either with or without further beneficiation, be discharged as finished products or they may, as required, either be returned to the autogenous mill 1t), directing to appropriate treating means in regard to conduit 122, or used, for example, as grinding media in an auxiliary or supplemental size reduction device 136 of any appropriate type. In this latter regard, a tumbling type mill can be used in which the sized pebbles 59 are suitable to serve as grinding media for reduction of other material fed thereto which usually is considerably smaller in size range than said pebbles 50. If the size reduction device 136 is other than as described above, it may be, for example, a secondary crushing or coarse grinding device useful for further beneficiation or treatment such as directly reducing the size of the pebbles or coarser size fractions either to render the values therein more readily accessibleto beneficiation or for tine grinding thereof or to producea productof smaller usable size for return to mill 10 or other means.

In the exemplary mill system shown in FIG. 4, there also is an exemplary return line 138 indicated as being directed to the entrance of the mill .10, even though such entrance is not shown in said figure. There also is an exemplary conduit, feed belt or the like, 14% diagrammatically illustrated as leading to the entrance of the supplementary or auxiliary crushing or grinding device 136. With these various return and conducting lines thus identified, a description of the further handling of the products discharging from the various additional beneficiating or treating means briefly referred to hereinabove, now will be set forth.

Considering first the material which is received from the classifying and segregating means 46 and particularly the portion thereof which is divided by splitter 116 so as to be directed into conduit 7124, the divider or splitter 134 in the latter can be positioned either to direct the coarse fraction of material back to the mill 10, or to the auxiliary or supplemental crushing or grinding device 136, or both, simultaneouslyv Appropriate positioning of splitter 134 may be a desirable procedure particularly when regulation of the quantity delivered to crushing or grinding device 136 is desired. Said device 135 may either be a tumbling mill, as above described, or a secondary crushing or grinding unit for direct reduction of the pebbles t delivered thereto. The product therefrom may either leave the mill system at 14th or may be returned to the mill for further reduction in size by conveyor line 138 through appropriate positioning of guide aechanism 136. By this procedure, any excess accumulation of an intermediate size range in mill 1% can be eliminated and the capacity of the mill increased.

The material which is discharged into conduit 122 has va wider choice of treatment than that which is illustrated :in exemplary manner as having been discharged into conduit 124. For example, the directing blade 125 may be set to discharge the material through conduit 62 onto picking belt 64 and, in the event the magnetic separator '66 is employed, some of the material, such as non-mag- :netic material for example, may be discharged into chute or conduit 126 and, depending upon the setting of the :Splitter blade 1319, some or all of the material may be discharged either as waste or desired product, as indicated by the arrow 142, while that material which is discharged along the line of the exemplary arrow 144, is

subjected to the action of an additional splitter which serves to direct the material into or divide the same between return line 138, which carries it to the entrance of :mill 10, or the conduit or feed belt Mt) which carries it fto auxiliary crushing or grinding device 13a for treat- ;ment as heretofore described. The quantity delivered to :splitter 145 is adjustable by varying the position of splitter .130.

The magnetic material is carried into conduit 128 upon :release from the magnetic separator 65, whereupon it engages the divider or splitter blade 132, whereby some or all of the material may be discharged or removed from the system, as indicated by the exemplary arrow 148, or said material may be directed to a further exemplary splitter 15%), from which location the material can be directed in the same manner as that described for the nonmagnetic material indicated by

conveyor lines

138 and 140.

Regarding the heavy media products discharged from exit chute 94 of the separator 82 and which products are subject to the splitter 132, it will be seen that, depending upon the setting of such means 132, some or all of the material may be either discharged as waste or finished product according to arrow 152, or may selectively be directed either to the line 138 for return to the entrance of mill 10 or the line 14-0 for transmission to the entrance of auxiliary crushing or grinding device 13% or both.

The lighter segments of material discharged from the heavy media separator 82, as indicated by the exemplary arrow extending from exit 38 of said separator, may be handled similarly to the heavy or sink material as to discharge into splitter 154 and exit from the system at 156, partial or total return to mill 10, or directing the same to auxiliary crushing or grind-ing device 136 via conveyor or conduit lines 138 and/or 140.

Still a third possibility for the material in conduit 122 being subjected to a particular setting of the directing blade 125 comprises setting the latter so as to direct the material along exemplary line 158 to direct it to the exemplary supplementary beneficiating or treating means 96 which can comprise any of a wide variety of means such as concentrating tables, jigs, spirals, flotation apparatus, alternate magnetic separators, as well as additional sizing and reduction means including appropriate crushers or auxiliary mills. From this auxiliary beneficiating or treating means 96, the product may be discharged, as indicated by the exemplary arrow 1%, as either a waste or finished product for example, or a portion thereof may be returned to mill 14) through line 138, or another portion may be sent to a crushing or grinding device 136, all as above described for the other beneficiation means.

The explanation of discharge conduit line 122 in H6. 4 also applies to conduit 122' of FIG. 5 which illustrates a finer size range of material than that of conduit 122 in FIG. 4. While guide means 125 of the system in FIG. 4 may direct the product, in the size ranges produced in the coarser separation circuit, to one of the beneficiation or treating means, guide means 125 of the system in FIG. 5, which receives its split material from splitter '9 116', will direct its size range to another treating means as exemplified by the various means here described.

Guide means 125 or 125' preferably are not dividing or splitting means such as splitters 116 or 116' of FIGS. 4 and 5 but are of the type made to direct the entire amount received thereby to one of the appropriate beneficiation, or treating means, unless special conditions prevail. This is a different action from the divider or splitter means in the other lines from discharge conduits 124 or 124', as illustrated by

splitters

116 and 134. This different action also applies to the

other splitters

130 and 146, which are in hte magnetic separator circuit, and likewise to

splitters

132 and 150, or

splitters

132 and 154 in the heavy media circuit. As for other beneficiation or treatment units 96, the operation of splitters associated therewith for directing the products, as desired, is the same as described above, although not shown. These splitter arrangements, as above described, if desired, direct all or part of the material received thereby to one path or divide the quantity received according to the choice of the operator. Three paths generally are available; exit from the system, return to mill 10, or delivery to the crushing or grinding device 136.

Regarding the finer size ranges delivered from chute 110 of FIG. 3, these may leave the circuit entirely, or be treated therein, but ordinarily the quantity is greater than that which is capable of being handled properly by the system contemplated here. One of the principal advantages of the system comprising the present invention is the economical means of handling only portions of the various size ranges during their period of retention in the circuit and as they are being reduced in size. Thus the cost of the beneficiation apparatus is minimum and recovery of the values is increased. Such a procedure is unique by virtue of the fact that all sizes are being reduced simultaneously in the same system and such treatment is given to only relatively small amounts of a given size range at any one time, yet the objectives desired are economically achieved.

As an example of the foregoing, if the larger size fractions discharged from trommel 104 are in excess of the quantity desired to be treated by the various means employed, said fractions may be returned to the mill. By this procedure an important step is accomplished in that the beneficiation or treating devices need not be of a capacity. to handle all the product at one time. Such devices of lesser capacity can be relatively small and less costly than devices of larger capacity, yet eventually they handle the material prior to its being reduced so fine as to pass beyond the size range for which said beneficiation or treatment step serves a useful purpose. This is particularly true in an autogeno-us grinding mill circuit handling run-of-rnine material where the tendency therein is to produce a relatively large percentage of a socalled medium size range in the mill charge. It follows, then, that by treating a portion of the so-called medium size range by crushing or grinding device 136, and returning the same to autogenous mill 1d, the percentage of said so-cal led medium size range is controllable, with the resultant beneficial eifect upon the autogenous grinding mill circuit.

In the mills illustrated in section in FIGS. 2 and 3, the ends are conical or sloping. Such contour is advantageous with certain materials and under certain conditions, especially in regard to discharge characteristics inherent to a sloping grate. However, there are other contours, especially of the discharge end of the mill, including the grate attached thereto, which operate more advantageously with certain other kinds of material under other types of operating conditions. Two exemplary embodiments of such other interior contours are illustrated in exemplary manner in FIGS. 6 and 7, both of which have in common the feature of the grate being substantially perpendicular to the axis of the mill.

Referring first to the embodiment shown in FIG. 6, it

will be seen that the tumbling mill 10, which preferably is of the autogenous type, has sloping or conical opposite ends 14 and 16'. The end 14' is protected by conventional lining material and is provided with radial lifter bars 2% and an annular deflector ring 42". The periphery also is similar to that shown in FIG. 2 but the discharge end 16 is provided with a grate 162 which is substantially perpendicular to the axis of the mill and over the inner face of which preferably radial lifter bars 164 extend, the same serving to hold the grate 162 connected to the exit end of the mill, if desired. The grate 162 extends substantially from the inner periphery of the mill toward the axis a predetermined extent, the inner periphery of the grate terminating adjacent an annular deflector ring 166 which, like grate 162, is spaced in an axial direc tion from end wall 16' to provide an annular discharge space 168 of greater relative capacity than the space 32 of the embodiment of FIG. 2 when mills of comparable dimensions are compared. Suitable spacer bars 170 serve to maintain said grate 162 and ring 166 in operative spaced position relative to end 16'.

The deflector ring 1656 is spaced radially appreciably from the axis of the mill and also radially from the conical terminal member 172. An annular interior wall member 174 extends between the perimeter of member 172 and ring 166, the same preferably being made of conventional abrasing resisting lining material and positioned relative to end 16' by spacer bars 170. Formed within the grate 162 are a limited number of discharge openings 176 of substantially greater size than the normal discharge openings or slots in the grate 162, whereby a minor proportion of relative coarse size pieces 5t) and a small amount of fines and intermediate sizes of the material are discharged therethrough, said pieces 50 comprising pebbles or cobs suitable for use as grinding media in the mill 1d, if reintroduced thereto after removal, or in other auxiliary or secondary mills. Such grin-ding media is similar, for example, to the pebbles 50 discharged through openings 48 in the embodiments of FIGS. 2 and 3, but the openings 176 preferably are formed directly in the grate sections rather than being between the grate sections as in regard to openings 48.

One of the principal advantages of the perpendicular type grate 162 over the sloping grate 30 is that grate 162 is much less subject to direct impact abrasion than grate 3i) and where material is particularly abrasive, especially to the grate segments, grate 162 obviously is more advantageous than grate 30. In view of the position of the deflector ring 166 as compared with ring 42 of FIGS. 2 and 3, different deflection will occur relative to similar loads in the respective mills, whereby the lateral movement of the material within the mill likewise is affected, and depending upon the material, mill operation characteristics and the like, the position of ring 166 may offer advantages over the position of ring 42 relative to grate 30 and the mill axis in FIGS. 2 and 3, while the latter may offer advantages over the positon of ring 166 of FIG. 6 in regard to other types of material, mill operation characteristics, and the like.

In the further embodiment of tumbling and preferably autogenous-type mill contour shown in FIG. 7, the end walls 14" and 16" preferably are substantially parallel and the same are lined with conventional lining material and especially the wall 14" has radial lifter bars and a deflector ring carried thereby which are similar to the corresponding elements in the embodiments shown in FIGS. 2, 3 and 6. However, the end wall 16" is the exit end wall and it carries the grate 173 which not onlyis perpendicular to the axis of the mill but also is parallel to the exit end of the mill. The grate 178 also is spaced axially from end wall 16" to provide exit space 180 into which material discharged from the grinding zone of the mill through the grate openings is received prior to being elevated and completely discharged from the mill through the exit trunnion as in regard to the mill of FIGS. 2 and 3.

It will be'seen from FIG. 7 that the mill shown therein also is provided with an annular, laterally extending expansion zone 132 between the periphery of the mill and the outer periphery of grate 178, into which falling material may move laterally to expand, while when the material is elevated during rotation of the mill and tumbles or cascades onto the load portion of the material in the lower portion of the mill, the annular deflecting ring causes further deflection over the afforded by ring 42", on the opposite end of the mill, and additional deflecting ring 1% adjacent the inner periphery of grate The latter ring and the perpendicular position of grate 178 offer advantages similar to corresponding elements in the mill of FIG. 6 with respect to different materials, mill operating conditions and the like. However, the expansion zone as well as the parallel end walls of the mill of FIG. 7 offer still other variations in operational characteristics which, especially in regard to some types of material and operating conditions will offer advantages not possible with the other mill contours illustrated and described herein. Conversely, these other contours ohcr more advantages relative to still other materials ground under possibly different mill conditions such as spec 1, wet or dry, and the like.

As in regard to the mill of FIG. 6, that in FIG. 7 also preferably has a limited number of discharge openings 138 therein of similar size and quantity, and for similar purposes, as openings 1% in the mill grate 162 of FIG. 6, to discharge pebbles or cobs Openings 188 also are in the grate per se.

For purposes of clarifying the intended meaning of certain terms used hereinabove and in the appended claims, the following general definitions are included:

Treating is intended to encompass size reduction and/or beneficiation of the material, either singly or in unison.

Size Reduction pertains to making size change only.

Beneficiation is generally considered the process of removing either part or essentially all of the value material from the waste material, depending upon the characteristics of the material such as grain structure, and usually requires size reduction at one or more size ranges of the material so as to properly cause economic liberation of most of the waste material from the value material.

Value Material is relative in that it may and usually does contain some waste material, hence the reason for size reduction of certain ores to a relatively fine degree, especially where the values are locked in so as to require fine division or grinding to render them accessible and liberate them. Other materials may be almost pure values, even in larger sized com, oncnts, and still other ones have a mixture of these characteristics.

Waste Material also is somewhat relative since it may be substantially completely waste or contain a minor amount of values. Thus it is subject to the same consideration as the above-described value material in that it may require additional treatment at times such as size reduction and/ or beneficiation, depending upon the character of the material.

From the foregoing, it will be seen that the various embodiments of mill systems, classifying and segregating means such as unit 46 in FIG. 4, together with the various directing and splitter arrangements and treating means and units, are capable of handling selected size ranges of material. The present invention affords a relatively Wide variety of various means and mechanisms, as well as processes produced thereby, for effecting max imum eliiciency in the autogenous grinding mill 1t} and system associated therewith. One of the principal advantageous features of such systems is the provision of size limiting and adjustably positionable discharge openings 48 through which a relatively wide range of sizes of materials may be discharged, in limited amounts, from the iii.

grinding zone of the mill so as to relieve the mill thereof and, in particular, to remove relatively coarse fragments of value material from the mill system as soon as liberated from the waste material associated therewith, there- :by not only reducing reduction costs but, in many instances, greatly increasing the overall recovery of the value material when the means and methods described are employed in conjunction with an autogenous mill treating a mix are of a wide range of sizes such as run-ofmill ore.

While the invention has been described and illustrated in its several preferred embodiments, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as claimed.

No claim:

1.. A method of beneficiating run-of-mine friable mineral material comprising the steps of subjecting such material including relatively coarse, medium and fine size ranges thereof to autogenous grinding Within a mill to reduce all size ranges thereof, removing a portion of se lected size ranges of said material larger than said fine size ranges from the mass of the material being reduced, subjecting said removed material to treatment while not co-mingled with said mass comprising the steps of classifying the same by screening into at least two general size ranges and beneficiating the coarsest size range'by subjecting the same to magnetic separation to effect a separa: tion of material values therein from waste material, and returning to the mass of material beingreduced any part of said separated material requiring further reduction.

2. A method of beneficiating run-of-mine friable mineral material comprising the steps of subjecting such material including relatively coarse, medium and time size ranges thereof to autogenous grinding within a mill to reduce all size ranges thereof, removing a portion of se lected size ranges of said material larger than said fine size ranges from the mass of the material beingreduced, subjecting said removed material to treatment while not co-mingled with said mass comprising dividing the same into two components and subjecting one of said components to further reduction in size and subjecting the other component to a beneficiation step to elfect a separation of Waste material from value material therein, subjecting one of the materials separated by said beneficiating step to additional size reduction, and returning to the mass of material being reduced any part of said separated material requiring further reduction.

3. A method of beneficiating run-of-mine friable mineral material comprising the steps of subjecting such material including relatively coarse, medium and fine size ranges thereof to autogenous grinding within a mill to educe all sizes ranges thereof, removing a portion of selected size ranges of said material larger than said fine size ranges from the mass of the material being reduced, and subjecting said removed material to treatment while not co-mingled with said mass comprising etfecting a plurality of size range separations, subjecting each size range portion to division and, subsequently subjecting one divided portion thereof to further reduction and subjecting the other divided portion to beneficiation to produce fractions respectively comprising value and waste material.

4s. The process according to claim 3 including the further step of subjecting said waste material fraction to further reduction in size.

5'. The process according to claim 3 including the further step of subjecting said value material fraction to further reduction in size.

6. A method of treating run-of-mine friable mineral material comprising the steps of subjecting such material including relatively coarse, medium and fine size ranges thereof'to autogenous grinding within a mill to reduce all size ranges thereof, removing a portion of selected media.

:to feed run-of-mine material to tively medium size material means to return to the tumbling mill any desired portion size ranges of said material larger than said fine size ranges from the mass of the material being reduced, subjecting said removed material to treatment while not comingled with said mass and comprising the steps of classifying said remove-d material by screening to separate it into at least two general size ranges, further treating the coarsest of said size ranges by dividin the same into two "components, subjecting one divided component of said coarsest size ranges to a further beneficiating step, and beneficiating the other divided component of said coarsest size ranges and returning one portion thereof to said mill to effect further autogenous reduction.

7. A method of treating run-of-mine friable mineral material comprising the steps of subjecting such material including relatively coarse, medium and fine size ranges thereof to autogenous grinding Within a mill to reduce all size ranges thereof, removing a portion of selected size ranges of said material larger than said fine size 'ranges from the mass of the material being reduced, di-

viding said removed material into two components, sub- "jecting one of said divided components of size ranges to be'neficiation treatment for the separation thereof into at "leasttwo products, and directing one of said products to an auxiliary grinding mill for use therein as grinding *8. A method of treating run-of-mine' friable mineral "material comprising the steps of subjecting such material including relatively coasre, medium and fine size ranges thereof to autogenous grinding within a mill to reduce all size ranges thereof, removing a portion of selected size ranges of said material larger than said fine size ranges from the mass of the material being reduced,

iary size reduction, and then subjecting the product of said auxiliary size reduction to additional autogenous grinding to produce a product of a desired size range.

' 9. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an autogenous tumbling mill having inlet and exit means therein, means said inlet means of said mill for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereofjmeans to discharge from said exit of said mill line and medium size ranges of material of predetermined maximum size, means to size the discharged material and segregate said material into relatively fine and relatively medium size ranges, means to effect a selection of a portion of said medium size ranges of material, means to treat said selected portion of said relato beneficiate the same, and

'of said beneficiated fraction of relatively medium material for further reduction in size.

10. The mill system according to claim 9 including additional means operable to return to the tumbling mill the relatively medium size ranges of material which are not beneficiated.

11. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an autogenous tumbling mill having inlet and exit means therein,

means to feed run-of-mine material to said inlet means ofs'aid mill for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereof, means to discharge from said 'exit 'of said mill fine and medium size ranges of material f predetermined maximum size, means to size the dis- -charged material and segregate said material into relatively fine and relatively medium size ranges, means to effect a selection of a portion of said medium sizeranges 'of material, means to treat 'a selected portion of said relatively medium size material to beneficiate the same,

charge from said classify said discharged size ranges of material size-reduction means, and means to deliver said non-selected portion of medium size ranges of material to said size reduction means for further reduction treatment.

12. The mill system set forth in claim 9 further characterized by said sizing means comprises screen means, and said mill system further including means to receive the sized ranges of material from said screen means, and said means to select a portion of said medium size ranges of material comprising dividing means adjustably positionable relative to said receiving means and operable to separate said desired portion of medium. size range of material from the material received by said receiving means and feed the same to said treating means for benefieiating the same.

13. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an autogenous tumbling mill having inlet and exit means therein, means to feed run-of-mine material to said inlet means of said mill for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereof, diaphragm means adjacent said exit means having openings therein to discharge therethrough from the grinding zone of said mill fine size ranges of material of predetermined maximum size, said diaphragm also having a minor number of discharge opening means of larger size than said aforementioned openings and of a total area substantially less than the total area of said aforementioned openings also to disgrinding zone a restricted amount of material of predetermined maximum size, means to classify said discharged size ranges of material discharged from said mill and segregate said material at least into relatively fine and relatively medium size ranges, adjustable means operable to receive said medium size ranges from said segregating means and divide the same, means to receive and treat a divided portion of said medium sized material to beneficiate the same, and means to effect a selection of any desired portion of said beneficiated portion of said medium sized material and return the same to the tumbling mill for further reduction in size.

14. A mill system for autogenous grinding and treatment of friable mineral material comprising an autogenous tumbling mill having inlet and exit means therein,

means to feed run-of-rnine material to said inlet means of said mill for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereof, diaphragm means adjacent said exit means having openings therein to discharge therethrough from the grinding zone of said mill fine size ranges of material of predetermined maximum size, said diaphragm also having a minor number of discharge opening means of larger size than said aforementioned openings and of a total area substantially less than the total area of said aforementioned openings also to dis charge from said grinding zone a restricted amount of material of predetermined maximum size, means to discharged from said mill and segregate said material at least into relatively fine and relatively medium size ranges, means to divide said medium size ranges into several desired portions, means independently of said autogenous mill operable to receive and further reduce the size of at least one of said desired portion of said relatively medium sized material, and means to return to said autogenous mill any desired portion of said further reduced medium sized portion for still further reduction of the size thereof.

15. The mill system set forth in claim 9 further characterized by said treating means comprising a magnetic separator, and adjustable means to receive separated fractions therefrom.

16. The mill system set forth in claim 9 further characterized by said treating means comprising a heavy assnaoa 17. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an autogenous tumbling mill having inlet and exit means therein, means to feed run-of-mine material to said inlet means of said mill for simultaneous reduction of all sizes of such material including relatively coarse, medium and line size ranges thereof, means to discharge from said exit of said mill relatively fine and a restricted amount of a relatively medium sized range of material, means to receive and classify the discharged size ranges of material from the grinding zone of the mill and segregate said material at least into relatively fine and relatively medium size ranges, means to effect a selection of a desired fraction of said classified medium size ranges of material, means to treat at least said selected fraction of said sized medium range of material to beneficiate the same, an auxiliary autogenous mill, and means to feed a desired portion of said beneficiated relatively medium size fraction of material to said auxiliary autogenous mill to serve as grinding media therefor.

18. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an auto genous tumbling mill having inlet and exit means therein, means to feed run-of-mine material to said inlet means of said mill for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereof, means to discharge from said exit of said mill time and medium size ranges of material of predetermined maximum size, means to size the discharged material and segregate said material into relatively fine and relatively medium size ranges, means to divide said medium size material into two portions, means to treat one of said divided portions of said relatively medium size material to beneficiate the same, and means to receive and further reduce in size the other divided portion of said relatively medium size material.

19. The mill system according to claim 18 further including an auxiliary size-reduction means, and material directing means communicating with said dividing means to receive said other divided portion of said relatively medium size material and operable selectively to direct said other divided portion either to said autogenous tumbling mill or to said auxiliary size-reduction means for further reduction in size.

20. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an autogenous tumbling mill, means to feed run-of-rnine material thereto for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereof, means to discharge from said mill medium and fine sizes of a predetermined maximum size and a minor restricted proportion of coarse size range, screening means positioned to receive said material discharged from said mill, said screening means being arranged and operable to separate said fine and medium size ranges from each other and including means otherwise arranged and operable to separate said restricted proportion of coarse material from said medium size ranges, means to divide said medium sized material into separated portions, beneficiating means, means to direct one of said divided portions of medium sized material to said beneficiating means for treatment thereby, additional size-reducing means, and means selectively operable to direct the other divided portion of medium sized material to said autogenous mill or to additional size-reducing means for further reduction in size.

21. The mill system according to claim 20 further including directing means positioned to receive said one divided portion after being beneficiated and operable selectively to direct any desired portion of said beneficiated material to said autogenous mill or to said additional sizereducing means for further reduction.

22. A mill system for autogenous grinding and beneficiation of friable mineral material comprising an autogenous tumbling mill, means to feed run-of-mine material thereto for simultaneous reduction of all sizes of such material including relatively coarse, medium and fine size ranges thereof, means to discharge from said mill medium and fine sizes of a predetermined maximum size and a minor restricted proportion of coarse size range, screening means positioned to receive said material discharged from said mill, said screening means being arranged and operable to separate said fine and medium size ranges from each other and being otherwise arranged and operable to separate said restricted proportion of coarse material from said medium size ranges, means to divide said coarse material into separated portions, beneficiating means, means to direct one of said divided portions of coarse material to said beneficiating means for treatment thereby, additional size reducing means, and means selectively operable to direct the other divided portion of said coarse material to said mill or to said auxiliary size,- reducing means for further reduction in size.

23. The mill system according to claim 22 further including directing means positioned to receive said one divided portion after being beneficiated and operable selectively to direct any desired portion of said beneficiated material to said mill or to said additional auxiliary sizereducing means for further reduction in size.

24. The mill system according to claim 22 further including additional dividing means positioned to receive and divide said medium size ranges of material into separated portions, additional beneficiating means, and means to direct one of said divided portions of medium size ranges of material to said additional beneficiating means for treatment thereby.

25. The mill system according to claim 24 additionally including means selectively operable to direct the other divided portion of medium size ranges of material to said mill or to said additional size-reducing means for further reduction in size.

26. A method of treating run-of-mine friable mineral material in a size reducing system comprising the steps of subjecting such material to autogenous grinding Within a mill to reduce all size ranges thereof, removing from the system a fine size range, selecting and removing from the mill a size range of said material larger than said fine size range from the mass of the material being reduced, subjecting a controlled portion of said selected material to a size reduction step While not co-mingled with said mass in said mill, and returning said portion to said mass for further reduction thereof.

27. A mill system for autogenous grinding and treatment of friable material comprising an autogenous tumbling mill having inlet and exit means therein, means to feed run-of-mine material to said inlet means of said mill for simultaneous reduction of all sizes of such material, means to discharge from said exit of said mill fine and medium size ranges of material of predetermined maximum size, means to size the discharged material and segregate said material into relatively fine and relatively medium size ranges, adjustable means to select a portion of said medium size ranges of material, means to reduce the size of said selected portion of said relatively medium size material, and means for returning the remaining portion of said medium size ranges of material back to the grinding zone of the autogenous grinding mill.

28. The mill system set forth in claim 27 further characterized by the diameter of the internal grinding zone of the mill being substantially greater than the axial length thereof.

29. The mill system set forth in claim 27 further characterized by the sizing means being capable of varying the size of the medium size range as discharged from the grinding zone of the mill substantially independently of the fine sizes, said sizing means comprising aperture means Within said mill.

30. The mill system set forth in claim 27 further including means to vary the quantity of medium size ranges References Cited by the Examiner UNITED STATES PATENTS Spitzer et a1.

Broadley 241-80 Pontoppidan 241-79 X Weinig 241- X Ladoo et a1.

Horsfield 241-26 X Erickson 241-20 Dowesett 241-80 X Fern et a1. 241-76 X Lawver 241-79 1/1960 Hardinge 241-19 8/1960 Wales 241- 11/1960 Weston 241- X 2/1963 Hardinge 241-26 2/1963 Hardinge 241-78 X 3/1963 Heckett 241-79 X 4/1963 Lukas 241-24 References Cited by the Applicant 7/1923 Ewing et 211.

OTHER REFERENCES German application, 1,033,604, July 10, 1958.

15 ROBERT C. RIORDON, Primary Examiner. I. SPENCER OVERHOLSER, Examiner.

Claims

1. A METHOD OF BENEFICIATING RUN-OF-MINE FRIABLE MINERAL MATERIAL COMPRISING THE STEPS OF SUBJECTING SUCH MATERIAL INCLUDING RELATIVELY COARSE, MEDIUM AND FINE SIZE RANGES THEREOF TO AUTOGENOUS GRINDING WITHIN A MILL TO REDUCE ALL SIZE RANGES THERE OF, REMOVING A PORTION OF SELECTED SIZE RANGES OF SAID MATERIAL LARGER THAN SAID FINE SIZE RANGES FROM THE MASS OF THE MATERIAL BEING REDUCED, SUBJECTING SAID REMOVED MATERIAL TO TREATMENT WHILE NOT CO-MINGLED WITH SAID MASS COMPRISING THE STEPS OF CLASSIFYING THE SAME BY SCREENING INTO AT LEAST TWO GENERAL SIZE RANGES AND BENEFICIATING THE COARSEST SIZE RANGE BY SUBJECTING THE SAME TO MAGNETIC SEPARATION TO EFFECT A SEPARATION OF MATERIAL VALUES THEREIN FROM WASTE MATERIAL, AND RETURNING TO THE MASS OF MATERIAL BEING REDUCED ANY PART OF SAID SEPARATED MATERIAL REQUIRING FURTHER REDUCTION.