US1146624A - Method and apparatus for classifying crushed material. - Google Patents

Description

F. W. HUBER.

METHOD AND APPARATUS FOR CLASSIFYING CRUSHED MATERIAL.

APPLICATION FILED DEC. 23. I914. LIQGfiQQD Patented July 13, 1915.

2 SHEETS SHEET F. W. HUBER.

METHOD AND APPARATUS FOR CLASSIFYING CRUSHED MATERIAL.

APPLICATION FILED 050.23. 1914.

LMfiMQ Patented July 13, 1915.

2 SHEETS SHEET 2.

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METHOD AND APPARATUS FOR GLASSIFYING GBUSHED MATERIAL.

Specification of Letters Patent.

Application filed December 28, 1914. Serial No. 878,772;

To all whom it may concern:

Be it known that I, FREDERICK W. HUBER,

The object of the present invention is to produce a method and apparatus, by which greater efliciency can be secured in classifying materials, of which we have different sizes existing in the same mlxture.

My process has been found to give excellent results in the classification of various kinds of material, among which I mention particularly ground Portland cement. In the grinding of Portland cement, it is necessary to produce a product having its particles composed of extremely fine powder, since it is only the fine material which is able to chemically unite with the water, during the setting of the cement, the coarse material acting merely as a filler, and apparently having no more binding power than an equal amount of sand or crushedstone would have. Accordingly it isnecessary to grind or crush the cement, then separate the pulverulent portion from the coarse material, and return the coarse material to the grinder, and to repeat this process, until all the material has been reduced to the desired degree of fineness.

Heretoforeall attempts to remove pulverulent material as formed, by means of air currents, have been very inefficient in that they produced an over-size product (the coarse fraction) which still contained a large portion of the powder or flour. The

reason for this I have foundto be due'to the insuflicient length of time that the material is left in contact with the air currents, and to the imperfect commingling of the air currents and the material, which prevents theflour or fines from being scrubbed loose and thereby removed from the coarser grains. In my invention I use, to get the necessary contact of material. and air current,

and the proper and sufficient commingling of 1 material and aircurrent, and the scrubbing or scouring action of the air current upon the material, a tube whose cross-section is alternately expanded and constricted into a series of chambers and necks, whose crosssectlonal areas bear to one another a fixed relation that can be varied only within very narrow limits. 7 I Anapparatus in accordance with my invention is illustrated in the accompanying drawings, in which Y F gure 1, shows (partly in section and partly 1n elevation) a complete apparatus, consisting of the classifying tube, dust separator and exhauster, and Fig. 2, shows diagrammatically the course of the currents of air and material under treatment, in passing through the classifying tube shown in- F1g. 1. Flg. 3 shows a portion of the connecting tube 5, and a portion of the chamber 2, on a much largerscale than the other figures, and the arrows therein show the currents of air or other gas, the straight arrows showing the general direction or flow of the gas current and the curved arrows showing the eddy currents which are set up in the maln current, when the gas passes from'the tube 5 into the chamber 2. Fig. 4

shows the modification of the apparatus in which connecting tubes are used, which connecting tubes, as shown in this figure may be of diflerent sizes or as shown in Fig. 2

' may be of the same size. Fig. 5 shows cham-' bers of different sizes, the chamber 6 being of large diameter relative to the pipe 7 and the tube 2 being-of small diameter, relative to the pipe 5. In this figure'the pipes 4, 5

and 7 are of substantially the same size, as

in Fig. 2. In 0th Figs. 4 and 5, I have shown the ratlo of the diameter of the chamber 2 to the diameter of the pipe 5 as being the smallest ratio which I have found to give said results. Assuming that these are both round .pipes the ratio of the diameters is equal to about 1.7. In both Figs. 4 and 5 I have shown the ratio of the diameter of the chamber 6 to the diameter of the connecting pipe 7 as being about the largest ratio which I have found to give good results, assuming that these pipes are round, the diameters.

being in about the ratio of 2.5 to 1.

The material to. be treated is introduced by means of the feed gate 1, into chamber 2 at a point near the-upper end of said chamher, but just below the air outlet 3 of said Patented July is, rare.

chamber 2, it being noted that the tube .4 projects downwardly beyond theupper end of the tube 3, a distance not less than the diameter of the tube 4. The idea of extending this tube 4 downwardly below the tube 3 is to prevent coarse material from being blown out through tube 3, by the air or gas current. From the lower end of the chamber 2 the solid material passes successively through the'neck 5, chamber 6, neck 7 to outlet trap 8, and the material is subjected throughout all this treatment to the action of an air blast.

By referring to Fig. 2, it Will be noted that as the air passes from the neck 7 to the chamber 6, and from the neck 5 into the chamber 2, there will be certain eddy currents of the air set up, which will very elfec-' tively and very thoroughly scrub the material under treatment, in order to remove from the coarse material, as much as possible of the flour or fine material, which fine material will then be carried away by the air currents, through the tube 3 to the dust settling chamber 9. From the passage 3 the gases enter tangentially into the upper part of the chamber 9 and pass downwardly through the same. Theair then passes upwardly through the chamber 10. In both the chambers 9 and 10, the air moves rather slowly, so that the greater-part of the dust settles out, and is withdrawn, continuously or intermittently through the gate 17. Introducing the air to the chamber 9 tangentially will aid the settling out of dust, to a considerable extent. The air, together with whatever dust is still carried thereby, then passes through any suitable form of dust filter 12 where the remaining dust is removed therefrom, and is then led through the pipe 13 to the inlet side of the fan or pump 14.. The pipe 13 is provided with a 'valve 15 by means of which the amount of suction at the outlet end of. the classifying tube may be regulated.

The exhauster 14 forcesinto the bottom of the pipe 7, through the outlet box 8 a-current of air with such 'a force, that the ascending air moves with suificient velocity to readily carry material finer than a certain predetermined grade, while the velocity is insuflicient to support material coarser than this desired grade. The suction at the point 3, exercised by the intake side of the fan 14, not only serves to remove the fines, as they are brought up by the ascending air in the classifying tube, but this also maintains a substantially constant velocity in the air current, and counteracts the loss of velocity head in the chambers, which naturally results from the friction between the descending solid material and the rising air. That portion of the material which stays in equi librium in this regulated current of air is displaced downward automatically as new material is fed in, at the top, so that it is only the finest material which leaves the classifying tube through the pipe 3. The over-size material from the box 8 may be allowed to accumulate in the lower part of this box if desired, and its outlet is perfectly regulated by means of a wing valve 16. I

The height of the scrubbing chamber is not a function of its diameter, but is dependent upon the velocity of the air current. The height of the scrubbing chamber in any case must be greater than the height to which a given velocity of air will raise and support material of the diameter of that to be separated from the fines, e. 'e., the oversize. The maximum height of the chamber will therefore be determined entirely by the range of grain sizes to be classified. An excess of heightover that indicated will, however, not detract from the efficiency of the classification except that the fine material will necessarily have to be lifted this additional distance, and thus cause an unnecessary consumption of energy.

While I have shown two scrubbing chambers 2 and 6, I call attention to the fact that any desired number of these may be employed, suitable connections 5 being provided between the successive scrubbing chambers. The scrubbing chambers and the Cross-sectional area of scrubbing chamber Cross-sectional area of connecting tube =6 is the largest ratio that can be economically employed, while a value of 2.8 for this ratio is the smallest that can be'used and still obtain sharp results. This ratio holds rigidly for the equivalents of tube 5 (z'. e., 4 and 7).

It will be noted that a considerable proportion of the dust like material will be removed from the coarse material in the first scrubbing chamber, and that the material so removed will be carried upwardly by the air blast, and accordingly will not come again into contact with the coarser material. It will also be noted that the coarser material from which a large portion of the fine material has been removed, will thereafter be brought into intimate contact with a current of dust-free air, in the lower scrubbing chamber, and the eddy currents in said 60 the fines passing 200 mesh, the eficiency material, t e succeeding crushing or grinding step :will bemuch more eflicient.

.While I have shown and described the may be of somewhat different diameters,

if desired,-and likewise the scrubbing chambers 2 and 6 may also be of. difierent diameters if so desired. The chambers also may be substantially cylindrical (or rectangular, having uniform cross section throughout their height) or if so desired they maybe. of other shapes. g I v The classifying column is illustrated as vertical in the annexeddrawing, and'while I prefer to have this vertical, I call attention to the fact that it may be inclined without departing from the spirit of myinvenf tion.

' While I have described air as the fluid to be employed in carrying out my process, I call attention to. the fact that other gases may be used. The gas to be usedwill obviously be one that-will not injuriously affect the particular material being clas- While I have described the invention as applied particularly to the manufacture of Portland cement, it .will'be noted that various other materials composed 'of coarse and fine particles of substantially the same specific gravity .may betreated, and I do not restrict the application of the novelprinciples herein disclosed, to the treatment of cement.

While the proportions may vary more or less, as above stated, I give the following example, which istlffor illustration only and not for the purpode of limiting the invention. In' this invention Portland cement is the material treated.

In the classification; of Portland cement, the tubes 3, :t, 5 and [may have'an internal diameter of 4% inches and the scrubbing chambers an internal diameter of 10 inches, the ratio of cross sectional area of the scrubbing chamber tothat of the tube in this example being 100:20i or about 5:1. The combined height of the parts 457 and of the parts 26 may be 18 and l8 inches respectively. With these dimensions, the pressure of the air entering the box 8 will preferably be about lb. per square inch, and the suction to be appliedthrough the tube 3 will preferably be equal to lb. per

square inch, below atmospheric. In this example, the material treated for classificatlon being ball-mill product ranging from 3; 1IlCll material down to dust, and practically all of process, for an entire days run, has been as high as 98%.

It will be noted that in my method of l classification, the entire air current enters License tubes 4, 5 and 7 as being of the-same diameter, I call attention to the fact that these the lower end ofthe classifying column, and passes out at the upper end of the column, and that all the dust separated from the material passes out through the outlet 3.

What I claim is v a 1. A process of classifying a material which'comprises feeding a stream of a material consisting essentially of a mixture of coarse and fine particles of substantiallythe same specific gravity, into an ascending current of'gas, at a level locatedashort' distance below the upper end ofsaid gas current, introducing all of the gas comprising said gas current at'the lower end thereof,

and withdrawing all said gas at the upper at end of said gas current, maintaining the force 'of the. said gas current at all points in the height thereof, sufiiciently great to support the fine but not the coarse particles contained .in said mixture to be classified, causing said gas current to repeatedly material to be classified, and producing eddy currents in said gas current, at a plurality of points in its height, and thereby subjecting the material to a scrubbing action until the pure material. is detached from the coarse and carried therefrom.

2. A process of classifying a material which comprises feeding a stream of a mate rial consisting essentially of a mixture of coarse and fine particles of substantially the same specific gravity, into an ascending. cur- .rent of .gas, at a level located a short dis tance below the' upper end of said gas current, introducing all of the gas comprising said gas current at the lower end thereof points in'its height, supplying the gas to the bottom of theclassifying column, sucking off the gas and suspended fine material carried thereby from the upper portion of the classifying column at a point somewhat above that at which material to be classified enters said column, and removing the dust from said gas.

3. A classifier comprising an upwardly extending series of vertically elongated scrubbing chambers and connecting pipes of less diameter than said scrubbing chambers, a gas outlet near the top of the uppermost scrubbing chamber, a feed inlet located at a point somewhat below said gas outlet, and means for passing a current of gas upwardl through said chambers and pipes.

4. n a classifier, the combination of an alter its velocity while in contact with the upwardly extending classifying column elongated scrubbing composed of alternately arranged vertically chambers and connecting pipes of less diameter than said scrubbing chambers, dust separating means connected to the upper part of said column, and means for withdrawing the dust-laden gas from the column at ,a point located a short distance above the inlet for solid material, through said separating means.-

5. In a classifier, a classifying column composed of alternately arranged vertically elongated scrubbing chambers and connecttroducing material to be classified to said column and means for passing a current of gas through said column.

In testimony whereof I aflix my signature in presence of two witnesses.

FREDERICK W. HUBER. Witnesses:

NORMAN MACBETH, J. D. MEYER.

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