US2078933A

US2078933A - Pulverizing mineral aggregates

Info

Publication number: US2078933A
Authority: US
Publication date: 1937-05-04
Anticipated expiration: 1954-05-04

Description

` Patented May 4, `19377 UNIT-ED' STATES. N

nennen s. nemwasmngion, n. c., ma' 101m f l. i Grou,-Minneapolls,lllnn.

ll-Our invention relates in general to the treatment of inorganic materials, such as metallic ores. i

`Itrelates more in particular to a method of and means for dsintegrating such materials explosively by. internal pressure. i i

Although our invention maylbe employed for the treatment `of many types of naturally occur-l `ring inorganic materials, it has its greatest 'value inthe crushing of ores preparatoryto recovering m the metals therefrom'. if It will be explained partlcularlytherefore bycomparlson `with present crushing processes'as applied to.ores. $1 Substantially all treatment of ores involves i .""crushlng of the ore Yto relatively fine size, the eic-` 15` act sizevidepending upon thespecic metal j re-` covery'process employed. Where notation is used, f `for example, the particles must be of very4 small size; other methods of concentration may b ecarried on in which-exceptionally iine grinding or m disintegration is not` necessary. `Whatever the size ofthe particles, however, it hasbeen customary heretofore to disintegrate the ore by' externally applied pressure.

methods, particularly where ilotationis employed,

t.. is ball milling. yThis part of the processie not only '3 very expensive.' but has other disadvantages, particularly in theproductlon of arelatively large vamount of nes,` andto the presenceofrlnes can be traced much of the metal losses occurring during flotation. Another disadvantage oi all meth- `ods of disintegration by external pressure is that 4 there is always `a. greatwdeal 'of useless work done in that the gangueor non-metalliferous portion ofthe ore is crushed as thoroughly 4as the metal- `li'ferous portion, thus representing a, great loss oftime and energy. i

` The principal object of our invention is to disintegrate ore in such a way as to avoid most` of the objections to thepresent form of treatment.

Another object is the provision offan improved .process for disintegrating ores by means of in' ternal pressure.

Another object is the provision of a process which may be controlled to crush the ores differentially.

Another object isthe preparation oi'ore in more satisfactory form `for treatment by lixiviation thanis accomplished byother methods of preparatiorg V y n nother object is the provision of a method for crushing ores which lwilleffectuate a saving in time andf labor and cheapen the overall cost of i ore preparation.

'Another object is `the provision of animproyed "55 r process adapted tonproduce a surface more amen- One of the comrnon'4 lrupt the ore. is suitablycontrolled, as will be explained herebe controlled Vto insure within the pores andinterstices oi' the ore, in-

able to flotation can be produced by present processes.

Other objects and features of the `invention maybe apparentfrom a consideration of the following 'detailed description taken with the ac- 5 companying drawing, wherein a single figure illustrates novel apparatus with which the method' may be practiced. o

In accordance with the general features ofthe invention, the `material to be treated is first given 10 a preliminary crushing to reduce it to comminuted form. The' sizesv of the pieces produced in vthe preliminary step will be determined to some extent bythe ore and the yfinal treatment to be given the ore. In general, `in this preliminary 15 treatment', the pes may be reduced to a size ot from one-quarterto on ,-halfV inch. @inyof the. usual types of crushers, such as-Symons, cone, for exampla'may be employed for this preliminary treatment.

Our invention utilizes thefact heretoforeap 20 .parently little `understood that ore material contains a relatively large amount of pores, small ag gresates and fissures, which can be made to absorb liquid such' as water, so that when subjected to 25 `a 'relatively high temperature and pressure in a closed ycontainer;` and suddenly discharged from thecontainer, the sudden expansion of the water into steam will cause an explosive action and dislWe have found vthatif the process 30 inafter, this explosiveaction can beutiliaed for the purpose of disi 'tegrating the ore'more satisfactorlly and at a considerable saving over all present types of ore crushing. The process should 35 a full supply of water cluding a control of the amountof water present with4 the ore Abut not confined within the pores tl'iereohas well as a proper control of the pres. o

sure and a proper control oi the explosive treat--` ment `of the ore,by the sudden release of the pressure.v

All of these features have an important bearing upon the the type of ore treated. The specific control, however,',to securethe bestresults, is determined to some extent by the ore.' It is also determined in part by the .resultsdesired For example, if

differential crushing is the desderatum, the control maybe somewhat different than if differential crushing is not sohighly important. In gen'- li eral, differential crushing occurs no matter how the process ils-practiced, but for particular ores modiiication of the pressure, for example, orthe results secured, independently of 5 explosions.

amount of water present will have an effect upon the amount of differential 'crushing In order to insure a. plentiful supply of water within the interstices-of the ore, preliminary soaking of the ore material should be employed. The time of soaking will differ somewhat with diiferent ores, and we have found that with some ores preliminary soaking for four or ilve days produces the best results. In most cases, soaking fora greater length of time does not improve the crushing action. The important point is to have the ore saturated with water and if the ore is of such a character that it is saturated in lesstime than four or five days, which is found to be-the case with many ores, the soaking time may be decreased. Substances which lower the surface tension of water, including the common wetting agents such as soap,'may be added to increase the penetration of the liquid into theinterstices of the ore; such additions, however, are notnecessary.

vWhen the process is carried out by a plurality of explosions it is, of course, necessary to insure that water is introduced into the ore between the This is preferably accomplished by discharging the ore from an explosion into water. In this way, water is drawn into any intersticial spacesl by the condensation of steam existing in them. As will be pointed out later, this discharge into water is advantageous from a standpoint of saving power.

The amount of water in addition to that introduced by soaking has an important bearing on the results. l It aifects the results not only from the standpoint ofthe amount of crushing obtained, but also has an effect upon thedliferential-crushing action. We have found that with some ores, and with external heating, for the best results, the additional water present during the heating period, or what `may be termed the added water. should be equal to at least half the weight of the ore, and even sometimes equal to the weight of the ore. The amount of water, however, is

` p determined in part by the manner of heating, and

also by the amount of diiferential crushing desired. In general, the amount should be kept as small as possible. When heating the container by external means, the amount vof water is greater than when heating by means of high temperature steam, which is our preferred method. To secure the best results for differential crushing, all of the water except that necessary to fill the interstices is preferably drawn oil' before the ore is released to atmospheric pressure. The exact technique here also, however, is determined in part by the manner of heating.

We believe that the best crushing effect is ob. tained when the interstices of the ore are filled with a. maximum amount of water at the time when the pressure is explosively rele'ased. When the container is heated by external means, all of the pressurewithin the container must be built up by evaporation of water inthe container.' An ample supply of water is, therefore, necessary to lproduce the requisite pressure and at the same time insure that there will be no drying out-effect on the ore. Probably the pressure has'the eiect of still further saturating the ore with moisture and the presence of water equal to from one-half the weight to the total weight of the ore always maintains an ample supply of moisture for further saturation. Before explosion, however, the l excess water is drawn oif and most of the water present will be contained within the ore itself but not externally thereof. After draining the conaovaose tainer, the ore should not be allowed to stand as this might cause some drying out before the explosion.

When the ore is heated in the container by means of high pressure steam, no excess of water in the container is necessary. Ore, after soaking, is drained and introduced in this condition into the container., Ihe presence'of the high temperature saturated steam ,apparently accomplishes everything in the way of further saturating the ore during the heating period.

The ore for most purposes is exploded with only a relatively smallv amount of water present,

except for that contained within the body thereof,

and in many cases substantially no free'water should be present for the best results. Draining olf the excess water before explosion, effects a saving since most of the cost of practicing the process is determined by the amount of water converted into steam.

The pressure within the container at the time when the ore is discharged therefrom is preferably between 150 and 200 pounds per square inch. It is between these pressure ranges that the most favorable and most complete crushing action takes place.- Below approximately 150 Pounds, the amount of crushed material gradually decreases, while vpressures greater than 200 pounds per square inch have very little increased effect on most ores. -In certain types of ores, the crushing action decreases at pressures above 200 pounds per square inch and we have instances where the greatest crushing action takes place at about 150 poundsrper square inch pressure and decreases slightlyas the pressure is raised .to 200 pounds per square inch. In certain types of ores, the greatest diiferential crushing action apparently" takes place with pressures of about 120 pounds per square inch, but usually the amount of ore crushedat this pressure is decreased so that an advantage is obtained in sacrificing some differential crushing action ,in theinterest of increased yield. f

y It should be borne in mind that the entire contents of the container should be in a state of equilibriumwhen the ore is discharged to atmosphere. This is best brought about by holding the flnal pressure for some considerable time before explosion. 'This promotes penetration of high pressure water into the interstices and assures that the temperature of such water is high and vuniform throughout.

For convenience, the process will be further discussed by first considering an approved form of apparatus with which it may be practiced. Referring to the drawing, we provide a container I0 having a loading dome I I closed by a revolvable valve I2, and an ore discharge chute I3 closed by a revolvable valve Il. Thesoaked ore is delivered by a suitable chute i6 to the valve I2. This valve, as shown, is so arrangedv as to close the chamber independently of its position so that the ore loaded into the valve, or feed chamber in which capacity it also acts. is delivered into the body of the con'- ralityof tiers i6, l1, I8 and I3, the bottom wall v 2l `ofthe container also functioning in thes'ame` manner-as the tiers., A vertical shaft 22 `carries a series of paddles or agitators 23, which pass over `the ore. supporting tiers and gradually move `the ore from an `upper tier to the next lower tier. e" e e ibut `the `cost lof ,the process is also greatly decreased.; It is obvious that the cost is principally '.l`lietiers` .are provided with lore discharge positionssfalternateiy at the outsideedge'landat the' innerV edgefin the manner shown. For example.`

the ore isdischarged fromlthe outside edgeof tier-Wto the outside edge of tiery il, whence it is graduallymoved to theinside edge of ftier` `l1V and discharged` to the inside edge of tiere/I8. In the caseuof the lowermost tier 2|; this coincides in a horizontal plane with the entrance to the `discharge chute I3, so that the ore delivered from,V

thistier dropsinto the, valve Il.`A

e eshaft 221s suitably journaled and slowly" 'rotated bymeans of a pair of beveled gears 24 and, the driving beyeled gear 28 `being con- 1 nectedto a. shaft 2l.l journaled througlithe side ofpressure.

walls ofthe container and packed to prevent loss i 1 steam iseoiitinuousiy admitted ihrough a steam pipe 28 to the interior of the container for heating theore and maintaining the requisite pressure on i the ore and inthe interstices thereof. Themove` mentlof the ore downwardly' on the tiers is timed softhat an equilibrium condition exists in the ore when it; is delivered to the valve M. The quickv rotationof the valve I4 disturbs its eduilibriu'mv condition andcauses the crushing.`

` yfllie ere delivered `intotlie feed chamber is wet,v having been previously saturated withwater by soaking a` suitable length of time. The" excess` water, however. Ahas been drained off, carefbeing* taken to` avoida drying "out, of the ore, however,

`lueftere it -isdelivered to the feed chamber. Sat- `urated steam Yis employed for heating and this m Vy be d pended upon to provide an ample "supplylof water for theexplosive action.

There are several'factors which have an effect upon the .shattering process. They may be listed e fingen'eral as follows;

` `(o) `Explosion of water inthe structure yof the minerali `trol of the the process involves `crushing only by means of i (u)` hihi.

(b) Eitplisionl of water in pores or cracks; i .,(c) shattering by impact of particles on each `other andfagainstthe walls of the explosion chamber 4or against the walls of a receiving bin; `(11) shattering e by unequal heating due to `ev'aporationof water producing" sudden cooling of surface.

, Our process is preferably `.governed by aconfactors hereinabove discussed so that.

` and (b), or at least principally by (a) and `This gives the greatestvamou'nt of differencrushing.` We have found that if there isa tialr ,largefamountof water present, a great`deal of the explosive' action isdue to the shattering of particles on each other, as described in (c) ."f Pos-l sibly Vsonrie of this` effect,when a large` amount of p water is, used, is alsok due to concussion or force 1entirely applied from without through a layer e etheamount of crushing action 75 of 1water `against the side walls of 'theparticles te "Iihis factor is best explained by ccxnparlsonto V .7; marines,` in` which `compressible acts as aram. This would beexi .pected to have the the depth` bomb method employed against sub# the water itself being noneffect of partially decreasing ii' an exceedingly large amount of water were employed, and also of sure, and

- large amount valuable when `crushing the gangue as `much as the mineral content of the ore. Experiments have shown that `this seems tothe-the case, as where a large amount lof water is used, lthe amount of crushing was `clecreased andthere was substantially no dinerential crushing action.

Not only. is the differential crushingl action increased by employingl a small amount of water.

determined bythe amount of water evaporated. Preferably we employ counter-current circulation of boiler feed water in a way to further increase'the economy; theoretical calculation shows that `the processican be carried on so that the i actual Aenergy input will amount vto onlyvabout 1000 B. t. u.s pernton of ore treated.` Byemploying the crushed ore to preheat the boiler feed waterjand heating'the ore with saturated steam,.the process'canbe carried on continuousiywith;apparatus of the character described so4 i that almostall heat energy consumed is inthe actual crushing. i ,e

`When the ore is to be re-exploded, it is of con siderable value. particularly whenfacontinuous process is employed. to discharge the ore4 so that immediately afterthe explosion it is precipitated 'into water, thus faciiitating the reiimng oithe pores while the ore is still somewhat warm, and also heating the water which can be circulated to the boiler .feed pumpor injector.

Although we prefer. toheat, the ore with saturatedsteam, our process may be carried out by I the application y,of external heatto the container;

- waterand steam are in equilibrium atV this presso'me water will be distilled fromthe ore close to thepoint at which the heat is applied.

f When heating is accomplished by. means of saturated steam, however, this difficulty is obviated.

-One of the; advantages of practicing our process in themanner described resides in the substantial elimination` of slime production in the soft ores such as iron ores. This is due to eliminatlng `crushing to a great extent by means of l impact, asreferred to, under (c) and (d) above.

Another feature and advantage is that the ore prepared ,is more' susceptible'to flotation` partly one-account'of `the lack of sllmes below a critical, sze Aandrpartly due tc the fact that the surface resulting from the crushing appears to 'be more amenable to flotation.

r ,Another advantage resulting.. from the practice of` our process in the manner described resides in the production of a iarg'eamount of `free surface of valuablematerial which may be includedin a large amount of worthless material.

Thiais true because the'contact between two different kinds oflminerals isusually susceptible to penetration by.wate r so, that in the `.explosion -process the breaks' most frequently take piace at the4 surface of the included minerals. This of exposed `surface is particularly it is desired to remove the y'mineral by liiiiviation. q

: When a large production of jsmall size ore particles is desired, as for example for flotation pur- `poseaitis preferable to re-explode the ore in a continuousseries of operations. This is accomplished by screening or any suitable means for separating the ore according to size.i The separation may be carried out in such a way that the gangue constitutents can be largely eliminated. Due to the differential crushing action which we obtain, all particles over a certain size (the exact size depending upon the ore) will be found to contain very little mineral matter and can be separated out before reintroducing the uncrushed ore bearing particles to the explosion crushing treatment.v

In connection with the above, it is found that a valuable mineral will be crushed more easily than the worthless gangue. Occasionaly, how

ever, this is not thecase, and sometimes the behavior is just the reverse and the gangue will be shattered more readily, leaving the valuable ore in the form of hard particles. Separation under the latter conditions will then be on the basis of the larger particles containing the valuable ore, and any of .the usual methods of separation, classification, sizing or the like can be used. The ore may then be re-exploded, or further treated in any suitable mannen 'I'here may be times, however, in which it will be desirable to re-explode the entire ore body without intermediate screening.' I

What we claim as new and desire to protect by Letters Patent of the United States is:

1. The method of pulverizing mineral substances and aggregates which comprises soaking the mineral substance in water, draining the excess water therefrom, introducing the water soaked mineral substance into a closed container,

admitting saturated steam into the container to' heat the mineral substance, and discharging the mineral substance from the container whereby the water therein is explosively converted into steam and disrupts the substance.

2. The method of pulverizing mineral substances and aggregates which comprises soaking the mineral'substan'ces in water, introducing the water soaked mineral substance into the container, introducing saturated steam into the container, continuously progressing the material through the container and counter to the circulation of the steam, whereby the mineral substance is raised to substantially the temperature of the steam as it passes through the container, and continuously discharging a portion of the hot mineral substance from the container whereby the water therein is explosively converted into vapor and disrupts the material.

3. A method of pulverizing mineral substances and aggregates which comprises heating the mineral substance with water in 'a closed container by means of steam introduced therein until an equilibrium condition exists in which a high steam pressure is above the mineral substance and its pores are filled with water. controlling the amount of water so that substantially all of the water present is contained in the pores of the,

mineral substance, and successively releasing amounts of the mineral substance to atmospheric pressure. l

4. The method of pulverizing mineral substances and aggregates which comprises heating the mineral substance in the presence of water in a closed container until a relatively high vapor pressure is developed therein, the amount 'of water being controlled so that substantially all that is present is contained in the pores and interstlces of saidmineral substances, discharging the mineral substance from the container whereby the liquid is explosively converted into vapor and the mineral substance pulverized, discharging the crushed ore immediately into water to cause the pores thereof to take up additional water, recharging the ore and water into the container, and again treating the ore to cause an explosive crushing thereof.

5. The method of pulverizing mineral subrium condition established' between vaporized and unvaporized water, and suddenly opening the container to discharge the substances therefrom.

6. The method of pulverizing mineral .sub-

stances and aggregates which comprises preliminarily processing the substances to produce aggregates of substantially uniform size, suitable for crushing, soaking said substances in water, charging the Water soaked substances into a sealed container, applying heat to said container by admitting saturated steam thereinto until a relatively high temperature and pressure are developed therein and an equilibrium condition established between vaporized and unvaporized water; draining the free water from said substance, and suddenly'opening the container to discharge the substances therefrom.

7. In a continuous process of pulverizing mineral substances and aggregates, the steps comprising, soaking the substance in water, succesl sively introducing portions of the water soaked substance into acontainer, continuously progressing the material thru said container and heating the same to raise the temperature thereof as it passes thru said container and to build up a high pressure in said container, and successively discharging amounts of the heated substance from said lcontainer into water whereby the water contained in said material is explosively converted into vapor, disrupting the substance and simultaneously preheating said water to condition the same for use in said continuous process.

8. In a continuous process of pulverizing min. eral substances, the steps comprising, soaking the substance in water, successively introducingamounts thereof into a container, introducing saturated steam into the container at a pressure between about and 200 pounds per square inch, continuously progressing the material thru of pulverizing mlny 2,078,983 i of the heated substance from s aid container into water whereby the water contained in said mate- `rial is explosivelyconvert'ed into vapor,` disrupting the substance and simultaneously preheatlng 5 said water to condition the same for use in said continuous process. l

10. The method of eiecting adiierential pul- 4"fveriaation of ore comprising ore mineral and assoelated gangue material which .comprises soaking l l0 the ore in subdivided form in anl aqueous medium to eiect substantial saturation of said ore with water, placing the saturatedore into a chamber,

` closing said chamber and thenintroducing there' intosteam'to build up the temperature and the `1 5 pressure in said chamber to afrelatively elevated 11. The'method o'f `effecting a differential pulverization of ore comprising ore mineral and assofciated gangue material, said ore being inthe t form `of aggregates of substantially uniform size, 25 suitableV for crushing, comprising prelimlnarily `soaking said ore in an aqueous medium to eiect a substantial saturation thereof with water, pass e ing steam into contact with said ore while disposed in a closed chamber whereby the ore is heated to an elevated temperature and a relatively high pressure is built up in said chamber, and then suddenly opening the chamber to release the pressure therein whereby the ore mineral is disrupted while the gangue material associated therewith is relatively unaffected whereby separation of the ore mineral from the gangue 'material is facilitated.

12. The process of pulverizing mineral substances which comprises soaking the substances in water, draining oli excess water to leave a predetermined amount of water in said substances,

subjecting said pretreated substances, containing vksubstantially only that amount of water which is retained in the pores and interstices of said sub# stances, in a closed container, to' direct contact with saturated steam 'at a relatively high temperature and pressure until an equilibrium is establishedbetween vaporized and unvaporized water, and then suddenly opening the container to permit sudden expansion or the superheated water whereby pulverization of the mineral substances is effected.

' REGINALD S. DEAN.

JOHN GROSS.