US2764287A

US2764287A - Treatments of materials in fine particles, particularly carbonaceous slimes

Info

Publication number: US2764287A
Application number: US236650A
Authority: US
Inventors: Harvengt Edmond
Original assignee: Link Belt Co
Current assignee: Link Belt Co
Priority date: 1951-07-13
Filing date: 1951-07-13
Publication date: 1956-09-25
Anticipated expiration: 1973-09-25

Description

, P 5, 1956 E. HARVENGT 2,764,287

TREATMENTS OF MATERIALS IN FINE PARTICLES, PARTICULARLY CARBONACEOUS SLIMES Filed July 13, 1951 2 Sheets-Sheet 1 g i] INVENTOR Sept. 25, 1956 E. HARVENGT 2,764,287

TREATMENTS OF MATERIALS IN FINE PARTICLES, PARTICULARLY CARBONACEOUS SLIMES Filed July 13, 1951 2 Sheets-Sheet 2 BY -MW ATTORNEY INVENTOR United States Patent TREATMENTS OF MATERIALS IN FINE PAR- gICLES, PARTICULARLY CARBONACEOUS LIMES Edmond Harvengt, Moustier sur Sambre, Belgium, assignor to Link-Belt Company, Chicago, llL, a corporation of Illinois Application July 13, 1951, Serial No. 236,650

16 Claims. (Cl. 209-18) The invention relates to the treatments of materials in fine particles and concerns particularly, although not exclusively, the treatment of carbonaceous slimes.

It is known that difficulties are encountered in treating such materials for extracting therefrom the valuable particles in view, amongst other, of the fineness of the particles rendering inaccurate or imperfect the separation by density in liquid medium, with the inconveniences resulting therefrom.

The invention aims to remedy these difliculties, and it has for object a method and apparatus adapted to provide for a more easy separation and valuable products in greater quantity and of improved quality.

In accordance with one feature of the method of the invention, subsequent to a careful removal of the argillaceous particles contained in the starting material, the latter is subjected to a conditioning process adapted to furnish a product substantially regular in composition and quantity, from which product dense particles are removed before it is subjected to a separating operation into categories.

In view of the regularity of the product, the said removal is rendered more easy and more complete and the subsequent separation may be more efficiently effected with greater yields in valuable products.

According to another feature of the method, the conditioning of the material derived from the argillaceous matter includes mechanically homogenizing the material with a control of the density thereof while, where necessary, adjusting said density by incorporation of an additional material, and controlling the discharge of the resulting product, the additional material when comprising solid particles being preferably formed by a middle product collected during the subsequent separating operation.

The removal of the dense particles is preferably effected on a straining bed, with the aid of liquid currents, preferably pulsatory currents, the pulse of which is made slowly decreasing while the subsequent separation is obtained by a grading and, or a settling operation.

For carrying into practice the method of the invention, a suitable plant essentially comprises a settling tank for the materials, or slimes to be treated, means for leading the pulp discharged at the bottom point or tip of the tank to a conditioning apparatus, a conditioning apparatus, preferably comprising a tank equipped with devices for mixing and homogenizing this pulp, as well as with devices for controlling the density and the discharge of the pulp and, as the case may be, for incorporating therein an additional material, one or several apparatus for receiving the discharge of the conditioning apparatus and remove the densest particles therefrom, and one or several troughs provided with extracting apparatus for separating the resulting mass into categories of products.

The settling tank is preferably equipped with devices adapted for extending its operative zone and moreover asymmetric in shape or provided with an asymmetric lower portion while, for eliminating the dense particles from the product discharged at the conditioning apparatus,

'ice

preferably use is made of jigs wherein the suction effects are substantially compensated or avoided.

Other features of the invention will become apparent from the following more detailed description with the aid of the annexed drawings showing diagrammatically pre ferred embodiments and wherein:

. Fig. 1 is a general view of a first plant embodying the invention;

Fig. 2 is a similar view of an alternative arrangement; Fig. 3 shows in section, at an enlarged scale, an extractmg apparatus.

Referring to the drawings and first to Fig. 1, 1 designates generally a settling tank, the lower part of which is of asymmetric shape and is provided with an adjusting valve 3 as well as with an outlet pipe 4 and an obturator 5 preferably comprising a double mushroom shaped body as illustrated and shown in greater detail in Fig. 3.

In the upper portion of the tank, in addition to the usual central conical annular member 6, there is arranged a conical element of lesser conicity, extending to a more or less lower level in the tank and adapted to be more or less closed at its lower end by means of a plug 8 of which the position within the opening 9 may be adjusted by means of a suitable mechanism, such for example as the lever mechanism 10 operable from the outside, at 11.

12 designates an overflow trough to which may be associated with advantage an evacuating trough 13 located at an intermediate level of the tank, these two troughs being provided with

discharge conduits

14 and 15 respectively. At least the discharge conduit 15 is equipped with an obturating device 16 and both discharges lead to a general tank of the plant while passing, as the case may be, through pools or basins or other cleaning devices, not shown.

Within the upper opening of the central cone 7 are arranged intake means 17 for the materials, preferably equipped with a screen or grid 18 for the removal of the foreign bodies and the particles of too great a size.

When a liquid current carrying with it solid particles is supplied to such an apparatus, and introduced within the central cone 7, due to the presence of such a cone, a portion at least of the current is caused to pass into the tank through the opening 9 at the level of this opening and for escaping therefrom is held to reach either the overflow trough 12 or the trough 13 while abandoning in the interval the particles carried with it. That part of the current which is not able to pass through or reach the opening 9, will pass over the upper edge of the cone 7 into theannular space between the cones 7 and 6, and from there passes into the tank from below the lower edge of this latter cone 6 to reach the trough 12 and, as the case may be, the trough 13 while abandoning in the interval the carried particles.

It will be seen that in this way the tank portion comprised between the level of the opening 9 and that of the lower edge of the cone 6 is rendered operative or more operative as regard the settling work with a resulting improvement of the latter. It will be seen also that by suitably adjusting the position of the plug 8 one may modify, relatively to one another, the values of the parts of the current passing through the opening 9 and under the lower edge of the cone 6 respectively, and on the other hand that an adjustment of the valve 16 enables a control to be effected on the length of the paths in the tank of the said parts of the current. It is thus possible to carry on a control on the decantation or settling operation in the tank and to a certain extent on the consistency of the deposit formed therein.

Thus in the method in accordance with the invention, the slimes fed at 17 from a supply tank such as 19 by means of the pump 20 may be carefully freed from argillaceous particles and formed into a pulp of desired consistency in the lower part and the point or tip 2 of the tank 1.

From this tip the pulp is led, under the control of the valve 3, by means of the exit pipe 4, arranged as a siphon, or otherwise, to a conditioning apparatus generally indicated 21.

This apparatus comprises a tank 22 the bottom of which is formed as a simple or multiple point or tip, each point or tip comprising a discharge controlled by means of an adjustable operating device 23, for example an operating device comprising a double mushroom or shaped body, like the obturator of the tank 1. in its upper portion, the tank 22 is provided with an overflow trough 24, the discharge 25 of which is led into the supply tank 19, and with a central partition, for example a cylindrical partition, 26, in the inner space of which introduced the material to be treated in the apparatus.

Means are associated with the tank 22, permitung to render its content substantially homogeneous and retained in this state and to this end, for example, nozzles 27 have been provided, opening in the lower portion of the tank and connected by means of a pipe, not shown, to a supply of fluid, and preferably air, under pressure, not illustrated.

With the tank are also associated means for controlling and, as the case may be, modifying the density of the content thereof. These means are here formed on the one hand by means of a loaded adjustable member 25 connected by a rod 29 to a beam 36} pivoted on a fixed bracket 31, and on the other hand by a pair of

reservoirs

32 and 33 each of which contains an addition material, which material when added to the pulp contained in the tank, are adapted for oppositely modifying the mean density of this pulp. One reservoir, for example the reservoir 32 may contain a liquid having a density lesser than that of the pulp, and which may be and is with advantage the same liquid as that of the pulp especially water, and the other reservoir will contain a solid material or a comparatively dense pulp, for example the said liquid with the addition of solid particles, especially a product collected in a later stage of the treatment of the slimes, as will be pointed out later.

Each of these

reservoirs

32 and 33 communicates with the tank 22 by means of a pipe provided with an obturating device, i. e., the reservoir 32 through the pipe 34 having a cock 35 and opening in the lower portion of the tank 22, and the reservoir 33 through the pipe 36 provided with a two way cock 37 and opening in the upper portion of the tank 22. The operating levers 38 and 3% for the obturating devices are both connected to the beam 3t) and the arrangement is such that the oscillatory movement of the beam causes movements in opposite directions of the obturators, i. e. a movement towards the opening of the one and a movement towards the closing of the other.

If desired, a screen ill may be arranged on the intake path of the pulp to be treated in the tank 22, which is adapted to remove the foreign bodies from this pulp. Under such conditions, the pulp coming from the tank 1 may be mechanically homogeneized, and brought to present a desired mean density by an addition coming from the

reservoirs

32 or 33, the preferred method consisting however to discharge at the point or tip of the tank 1 a pulp which is slightly denser that the desired pulp, while bringing same at the proper density by means of an addition of liquid from the reservoir 32. This homogeneized pulp of controlled density is discharged in a controlled and preferably constant quantity, from the apparatus 22 into apparatus adapted for extracting dense particles or shales contained in the pulp, the obturating devices 23 being suitably adjusted for this purpose, in principle in such a manner that a small portion of the content of the apparatus 22 steadily passes, through 24 and 25, into the tank 19.

The apparatus for extractin the shales are here formed by jigs preferably two in number, 41 and 42;, operating in series, and comprising a straining bed as well as means for attenuating or avoiding the suction effect due to the return strokes of the pistons generating the liquid pulses through the bed. Such means, which have not been illustrated for clarity, may be formed by a liquid stored in the cylinder space above the piston of the jig, and which is caused to pass in a controlled manner into the tank of the jig during the inoperative stroke of its piston.

As these jigs are supplied in a regular manner with a material having also been rendered substantially regular, they can be easily adjusted for etticiently ensuring the removal of most of the shale particles contained in the material coming from the conditioning apparatus 22, so that at the outlet of the jig 42 the starting slimes will be largely freed from the argillaceous particles on the one hand and from the shales on the other hand, this enabling a comparatively easy division into categories of products to be effected. The products from the tanks of the jigs are considered as waste products are eliminated through 43.

The aforesaid division into categories is obtained by subjecting the product coming from the jig 42 to a grading operation in a trough 44 followed by a trough section 45 equipped with extracting devices operating on the settling principle, of the kind illustrated at 46 in the figure and at an enlarged scale in Fig. 3. Such apparatus comprises (Fig. 3) a casing of generally conical shape 47, the internal space of which communicates with the trough through openings 43, to the edges of which are connected downwardly convergent walls or partitions 49, some of which may be formed by parts of the casing 47. At its lower end the casing 47 is provided with an adjusting obturator 50 including, as shown, a tapering nozzle 51 having associated therewith a shaped plug 52 the position of which is adjustabl relatively to the outlet opening of the nozzle and vertically below this first assembly is arranged a second convergent nozzle 53 and a plug 54 adjustable in position, the arrangement being such that by suitably adjusting the plug 52 the motive pressure of the outgoing fluid vein is reduced, the output being ultimately adjusted by the plug 54 cooperating with the nozzle 53, the arrangement enabling to retain for the

nozzles

51 and 53 outlet sections of sufficient size to avoid any obstruction thereof while the discharged quantities are maintained within limits compatible with the extraction of products to be effected in the trough, thus avoiding so called white discharges.

In the illustrated embodiment a first group of apparatus 46, three in number in the example, provides for the extraction of the densest particles which, through 55, are united to the shales discharged from the jigs 4i and 42, and a second group of apparatus 46 ensures the extraction from the trough of a middle or mixed product which may be conveniently used for conditioning the slimes supplied to the apparatus 22.. To this end, the discharge of this group of apparatus 46 is led through 56 in a sump or tank 57 from which the product is fed by means of a pump 58 and a pipe 59 to the reservoir 33. As indicated in the foregoing, the discharge 36 of this reservoir is equipped with a two way cock 37, one of these ways being used for supplying the product to the apparatus 22 under control of the device provided for adjusting the density of the medium in this apparatus 22, while the other way serves for returning differentially the product at an appropriate point in the cycle, conveniently at the head of the trough 44.

The end discharge of the trough section 45 is "formed with a product which is comparatively very clean and of value; the water therein is separated out on the scr 6i and 62' one of which may be provided with a device, and the product is ultimately collected at 53 on a conveyor 64 or otherwise.

The arrangement of Fig. 2 is similar to that of Fig. i; it diifers therefrom by a complementary refining treatment of the product discharged from the second group of apparatus 46 of the trough section 45, which trough section is otherwise provided with a reduced number of apparatus in the first group of extractors 46.

' For the said complementary treatment there is provided a trough section 65 at the head of which the product to be treated is supplied, its refining being ensured by means of a jig 66 similar to the jigs 41 and 42, and provided with a straining bed and suction balancing means, and where necessary by means of one or several extractors such as 67 similar to the extractors 46, the discharges from these apparatus being considered as waste products and evacuated through 68.

The product collected at the end of the trough forms a mixed product which may be used as such but which is used with advantage for conditioning the slimes in the apparatus 22 and, to this effect, conducted through 69 into the sump 57 from which it is supplied by the pump 58 to the reservoir 33.

As for the jigs 41 and 42, the marked regularity in quantity and composition of the materials supplied to the trough 4-4 and the following apparatus, enables them to be efficiently operated for securing, together with good yields, improved products. Although certain embodiments only have been described in detail, it is to be understood that the invention is not limited thereto but that it includes the alternatives, and that modifications may be made in the apparatus without exceeding the limits of the invention.

I claim:

1. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a homogeneizing zone and controllably feeding to said zone a material that is of different density than the fraction flowing to the zone, homogeneizing the first fraction and the material of different density in said zone to obtain a homogeneized pulp of a constant uniform density, withdrawing from said zone at a constant rate of fraction of the homogeneized pulp of constant uniform density, separately withdrawing the surplus from said zone as a second pulp fraction, removing from the homogeneized pulp fraction of constant uniform density the aforesaid waste fine particles of greater relative density, and separating the remaining valuable fine particles into different categories of products.

2. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a treatment zone and controllably feeding to said zone a material that is of different density than the fraction fiowing to the zone, homogeneizing the first fraction and the material of different density in said zone to obtain a pulp of constant uniform density, withdrawing from said zone at a constant rate a fraction of the homogeneized pulp of constant uniform density, separately withdrawing the surplus from said zone as a second pulp fraction and mixing it with the starting material, removing from the homogeneized pulp of constant uniform density the aforesaid waste fine particles of greater relative density, and separating the remaining valuable fine particles into different categories of products.

3. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a homogeneizing zone and controllably feeding to said zone a material that is of different density than the fraction flowing to said zone to obtain a homogeneized pulp of constant uniform density, withdrawing from said zone at a constant rate a fraction of the homogeneized pulp of constant uniform density, separately withdrawing the surplus from said zone as a second pulp fraction, removing from the homogeneized pulp fraction of constant uniform density the aforesaid waste fine particles of greater relative density, separating the remaining valuable fine particles into middlings and the final product, and utilizing the middlings in producing the said mixture of different density that is fed to said zone.

4. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a treatment zone and controllably feeding to said zone a material that is of different density than the fraction flowing to said zone, homogeneizing the first fraction and the material of different density in said zone to obtain a pulp of constant uniform density, withdrawing from said zone at a constant rate a fraction of the homogeneized pulp of constant uniform density, separately withdrawing the surplus from said zone as a second pulp fraction and mixing it with the starting material, removing from the homogeneized pulp fraction of constant uniform density the aforesaid waste fine particles of greater relative density, separating the remaining fine particles into middlings and the final product, and utilizing the middlings in producing the material of different density that is fed to said zone.

5. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and fine shale particles of greaterrelative density and a second fraction containing clay, simultaneously flowing the first fraction into a homogeneizing zone and controllably feeding to said zone a material that is of different density than the fraction fiovving to said zone, homogenizing the first fraction and the material of different density in said zone to obtain a homogeneized pulp of constant uniform density, withdrawing from said zone at a constant rate a fraction of the homogeneized pulp of constant uniform density, separately withdrawing the surplus from said zone as a second pulp fraction, separating. some of the aforesaid fine shale particles from the homogeneized pulp fraction of constant uniform density by the action of liquid impulses, and forming the remainder of said last mentioned pulp fraction into a flowing stream to separate the same by density grading into the remaining fine shale particles, a middling product and the final valuable fine product.

6. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating of the pulp into a first fraction containing a mixture of valuable fine particles and fine shale particles of greater relative density and a second fraction containing clay, simultaneously flowing the first fraction into a homogeneizing zone and controllably feeding to said zone a material that is of different density than the fraction flowing to said zone to obtain a homogeneized pulp of constant uniform density, withdrawing from said zone at a constant rate a fraction of the homogeneized pulp of constant uniform density, separately withdrawing the surplus from said zone as a second pulp fraction, separating some of the aforesaid fine shale particles from the homogeneized pulp fraction of constant uniform density by the action of liquid impulses, forming the remainder of said last mentioned pulp fraction into a flowing stream to separate the same by density grading into the remaining fine shale particles, a middling product and 7 the final valuable fine product, dewatering the said final product, and utilizing the middling product in producing a material of different density that is fed to said zone.

7. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain Waste fine particles, comprising pulping the starting material with liquid, subiecting the pulp to an accurately controlled settlins step to produce a first fraction of uniform consistency comprisin a mixture of valuable fine particlcs and waste fine particles of greater relative density and a second fraction containing argillaceous particles, sin il taneously fiowinr the first fraction into a homogeneizrng zone and feeding to said zone a controlled quantity of material that is of greater density than that of the fraction of uniform consistency flowing to said zone to ohtain a homogeneized pulp of a constant uniform dc sity which is greater than that of the fraction of unircr i consistency flowing to said zone, withdrawing from s..-d zone at a constant rate a fraction of said honiogeneized pulp of constant density and consistency, separately withdrawing the surplus from said zone as a second pulp fraction, removing from the said homogeneized pulp fraction the aforesaid Waste fine particles of greater relative density, separating tr e remaining valuable fine particles into different categories of products, and mixing one of said categories of products with pulping liquid to produce the said material of greater density that is fed to said zone.

8. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a homogeneizing zone and selectively feeding to said zone controlled quantities of two materials having densities which are greater and lesser, respectively, than the density of the fraction flowing to said zone, homogeneizing the first fraction and the two materials of greater and lesser densities in said zone to obtain a homogeneized pulp of a constant uniform density, withdrawing from said zone at a constant rate the said homogeneized pulp fraction, separately withdrawing the surplus from said zone as a second pulp fraction, removing from the said homogeneized pulp fraction the aforesaid Waste fine particles of greater relative density, and separating the remaining valuable particles into dilfercnt categories of products.

9. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material with a liquid, separating the pulp into a first fraction containing a mixture of valuable fine particles and Waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a homogeneizing zone and selectively feeding to said zone controlled quantities of two materials having densities which are greater lesser, respectively, than the density of the fraction fiowing to said zone to obtain a homogenized pulp of a constant uniform density, withdrawing from said zone at a constant rate the said homogeneized pulp fraction of a constant uni-f in density, separately withdrawing the surplus from said zone as a second pulp fraction, removing from the said homogeneized pulp fraction the aforesaid Waste fine particles of greater relative density, and separating the remaining Valuable fine particles into different categories of products, the said material of lesser density consisting of pulping liquid and the said material of greater density consisting of a mixture or" pulping liquid and one of the said categories of valuable fine particles.

10. A method of continuously recovering valuable fine particles from carbonaceous slimes which also contain waste fine particles, comprising pulping the starting material, separating the pulp into a first fraction containing a mixture of valuable fine particles and waste fine particles of greater relative density and a second fraction containing argillaceous particles, simultaneously flowing the first fraction into a homogeneizing zone and selecli tively feeding to said zone controlled quantities of two materials having densities which are greater and lesser, respectively, than the density of the fraction flowing to said zone, homogeneizing the first fraction and the two rials or g ater and lesser densities in said zone to 'iolZQd pulp of a constant uniform density, said zone at a constant rate the said a constant uniform density, separately withdrawing the surplus from said zone as a in it with the starting mate mogeneized pulp fraction les of greater relative 1e remaining valuable fine parc ant categories of products. rod for continuously recovering valuable fine onaceous slime which also contain compr ing pulp ng the starting matefraction containing trticle and waste fine particles a second fraction conaneously flowing the first fr ng zone and selectively f to sai entities of two materials .r and lesser, respectively, th n the de: ction flowing to said zone to homogeof a constant uniform density, zone at a constant rate the said tion of constant uniform density, .ng the surplus fr in said zone as a second pulp fracti n, removing from the said homogene- 30 ized pulp fraction the aforesaid waste fine particles of great r relative den ng the remainin" fine particles into a middli D product a final product, and utilizing the m .dling product in producing the material of greater density that is fed to s id 201 40 l2. ['1 c Li of c o. 1

rial, sec

ne parfraction "eousiy flowing e and selectivees of two mater lesser, respecllcwing to said of constant uniz at a constant cuen of a constant said zoo from u mixing it with he so homogenee fine particles of he remaining fine d a final product, ct in producing the mate zone. ig valuable fine wh 0 contain settling tank in which waste the start taii'iing a separated l to said conditioning a material of greater conn cted to the conta ning a matea pulp fraction contanlt, first density than the aforconnnioning I t N rial or lesser rot nected to the conditioning tank, means for homogeneizing the pulp in the conditioning tank, automatically operative means responsive to the density of the pulp fraction being homogeneized in the conditioning tank for controlling the selective feeding of the materials from the two reservoirs into the conditioning tank to obtain a homogeneized pulp of constant uniform density, means for discharging from the conditioning tank at a constant rate a part of the homogeneized pulp of constant uniform density, means for treating the said discharged homogeneized pulp to separate therefrom the Waste fine particles, and means for treating the remaining discharged homogeneized pulp to separate the same into a middling product and the final valuable fine particle product.

14. The plant of claim 13 further characterized by the provision of means for receiving the surplus homogeneized pulp from the conditioning tank and mixing it With the starting slime, and means for feeding such mixture to the settling tank.

15. The plant of claim 13 further characterized by the provision of means for receiving the middling product that is separated from the valuable final product and conducting it to the .said first reservoir to form the material of greater density that is controllably delivered to the conditioning tank.

16. The plant of claim 13 further characterized by the provision of means for receiving the surplus homogeneized pulp from the conditioning tank and mixing it with the starting slime, means for feeding such mixture to 10 the settling tank, and means for receiving the middling product that is separated from the final valuable product and conducting it to the said first reservoir to form therein the material of greater density that is controllably delivered to the conditioning tank.

References Cited in the file of this patent UNITED STATES PATENTS 1,290,515 Conklin Jan. 7, 1919 1,476,243 France Dec. 4, 1923 2,125,663 Wuensch Aug. 2, 1938 2,205,578 Adams June 25, 1940 2,332,953 Tromp Oct. 26, 1943 2,365,734 Tromp Dec. 26, 1944 2,477,948 Allen Aug. 2, 1949 2,550,829 Le Baron May 1, 1951 2,568,063 Gilbert et al. Sept. 18, 1951 FOREIGN PATENTS 117,465 Australia Sept. 16, 1943 482,051 Great Britain Mar. 23, 1938 507,661 Great Britain June 15, 1939 OTHER REFERENCES The Preparation of Coal for the Market, by Henry Louis, published in 1928 by Methuen & Co., Ltd., London, pages 69-71.