US2041188A - Pulverizer - Google Patents

Description

May my 1936.

W. G. JOHNSON PULVERIZER Filed Feb. 17, 1952k 2 sheets-sheet 1y May 19, 1936.n W. G. JOHNSON 2,041,188

' A PULVERIZER Filed Feb. 17, V1952 2 sheets-sheet 2 l 4l. 4/6 l H5 INVENTOR ATTORNEY Patented ,May 19', 1936 #UNITED STATES PATENT OFFICE PULVEB'IZER William G. Johnson, Milwaukee, Wis.

AApplication February 17, 1932, Serial No. 593,430

4 Claims.

always completely satisfactory.

AOne of the defects heretofore noticed was that frequently larger particles were mixed with the pulverized coal, so that a substantiallyl uniform degree of fineness was not obtained,

A further defect was that there was substantially no 'iiexibility in operation, as the pulverizers heretofore known could not be satisfactorily varied as to their output and did not, as a rule, operate satisfactorily below their standard rating.

This invention is designed to overcome the above noted defects, and objects of this invention are to. providel a novel form of pulverizer which obtains a higher percent of the fine pulverization than has heretofore been` commercially possible, and which is extremely flexible in its operation and may be operated at full rating, overload, or at a very much reduced output far below full rating.

Further objects are to provide a self-contained unitary pulverizer in which two power driven 'centrifuges are employed, one fed tangentially means and are immediately removed from the rapidly travelling air stream.

Further objects are to provide a pulverizer in .which the speed of either or both centrifuges may be varied soA that one may be varied independently of the other, whereby the neness of pulverization may be maintained although the output may be variedeither above or below the rated output of the machine thereby providing ilexibility in output though in no way varying the quality of the delivered product.

More specically, an object of this invention is to provide a pulverizer having a horizontalr centrifuge and a vertical centrifuge' embodied in one machine as a unit.

Further objects are to provide a pulverizer having the above noted characteristics which is compact, which is of simple construction, which is easy to install, which is easy to make, and which is eminently practical in actual operation.

An embodiment of the invention is shown in the accompanying drawings, in which:-

Figure 1 is a vertical sectional view through the machine.

Figure 2 is a vertical sectional view on the line t 2.-2 of Figure 1. y

Figure 3 is a diagrammatic View showing the piping, pump, and control mechanism for the feeding motor.

Referring to the drawings it willA be seen that l0 the pulverizer is a unitary, self contained device,

and comprises a casing provided with a lower rectangular portion i which bows out laterally as indicated at 2 in- Figure 2, and merges into a cylindrical upper portion 3, surmounted by a fan 15 vided with an open central portion, for instance by means of apertures 9 and provided with pivotally mounted hammers I0. 'I'he rotor 3 is carried by a shaft Il directly connected to a driving motor i2 located exteriorly of the cas- 30 ing. The shaft Il is preferably carried byroller bearings i3, as shown in Figure 2, andis directly connected to the shaft of a small oil pump I4 for supplying pressure oil to the automatic feeding mechanism. f

The coal is fed into the pulverizer downwardly along the slanting bottom I 5, see Figure 1, and beneath the rapidly travelling hammers l0 of the hammermill. The fragments of coal are prevented from flying upwardly by the curved buffer i6 which-isv preferably indented as indicated at Il to enhance the pulverizing action in a well known manner. An apron l 8 extends downwardly in front of the rotor to arrest flying fragments of coal. The incoming'air sweeps beneath'thet5 aprcn I8 and above a pivotally mounted gaging or` control flap i9, and rushes into the hammer mill, which is rotating counterclockwise as indicated in Figure l, and it will be seen that the rotor acts in the manner of a centrifugal fan and throws the air out radially.4

From an inspection of Figures l and 2 it will be seen that the curved buffer I6 is provided with downwardly extending flanges 20 on opposite sides of, and just above, the rotor of the hammer mill. Further, from Figure 2 it will be seen that an open space is left on each side of the rotor as indicated at 2| into which the outgoing', coal dust laden air is drawn from the central portion 5 of the rotor and symmetrically from both sides thereof.

The open spaces 2| communicate with the hood 22 which is contracted upwardly as may be seen from Figure 1. If desird a butterliy valve 23 may be placed within the hood 22 to aid in controlling the output. Y The hood 22 constitutes an inner casing which is spaced from the side walls o'f the main casing and provides a dead air space whose lower portion is closed by the forwardly and downwardly slanting bottom 25. The larger particles of coal entrained by the air stream and passingupwardly through hood 22 are separated out, by means hereinafter described, and are discharged into the dead air space 24 around the hood 22, such downwardly travelling, or returning stream of coal particles finally passing beneath the manually adjustable ap valve 26 and over the apron I8, back into the hammer mill, see Figure 1. The inwardly rushing air stream aids in sweeping these returned coal particles back into the hammer mill.

It is to be noted that if gravity alone is depended upon for removing rejected particles from the extremely fine particles, that a very coarse or ineffective-separation will occur in actual practice. The air stream will entrain fairly large particles and carry them along with the finer particles, and thus a non-uniform mixture composed of fairly large particles as well as small 'ones ls delivered to the boiler. However, this invention provides means for insuring and maintaining an extremely fine separation so that very stream. This is accomplished not only by the centrifugal action of the upper centrifuge, but also by the fact that the rejected particles are immediately passed to a reduced air pressure zone, namely, the portion 24, see Figure 1. At the lower part of the portion 24, namely, at the r'educed air pressure section of the casing, a slanting -bottom is provided and this reduced air pressure zone terminates in a suction zone where the rejected particles are actually sucked outwardly from the casing.

'I'he nest of separation accomplished by this invention enables a wholly new pulverized fuel boiler practice to be followed. With this invention it is possible to operate a boiler at 25% o'f full rating to something over 200% full rating. This, as far as known, has never before been accom- .plished with-.pulverized fuel.

It is an actual fact observed from tests and extensive experimentation that when starting, if 00.,the air stream is constricted by a valve, it is almost impossible to light the burner. In fact, it is so difficult that considerable trouble is exwperienced. However, by this invention the fan speed is reduced without any constriction of they 55 air stream and under these conditions from' actually observed tests it hasbeen found that the burner can be very readily lighted. r From observed tests with this invention, it has been found to be a fact that the carbbn dioxide chart shows- 15% or better at a boiler rating vary-- ing from 25% to 200%. As far as is known, this has not heretofore been accomplished with any 1 pulverized fuel fired boilers.

" The coal 21 is fed from the hopper 5 into the pulverizer by means of an automatic feeding small particles only are carried out by the airY mechanism having a reciprocating portion 28 operated by means of a reciprocatory motor indicated at 29. It is preferable to carry the member 28 upon rollers 30 to reduce friction.

The motor 29 is supplied from the pump I4 through the inlet pipe 3|, see Figure 3.- It is preferable to provide a valve 32 in the inlet pipe 3| and automatically control such valve by means of the pivoted flap I9, previously described so that as the layer of coal fed along the slanting bottom I5 decreases the feed motor 29 will be speeded up and as the coal piles up upon the bottom I5, see Figure l, the motor 29 will be slowed down. This automatic control is easily secured by operatively coupling the rocking ap I9 to the lever 33 of the valve 32, as shown, for instance, in

` Figure 3.

It may be desirable to have different speeds for the inward and outward motions of the feed member 28. This is readily secured by providing separate valves 34 and 35 in the return pipes or exhaust 36 and 31 which lead from oppositeends of the cylinder of the feed motor 29 and discharge into the oil reservoir or tank 38. The pump I4 draws oil from the tank 38 and supplies the motor 29. It is preferable to provide a by-pass valve 39, see Figure 3, in the supply pipe 3| from the pump I4 so that any desired proportion of the oil supplied by the pump may be by-passed to the tank 38, thereby providing a manual control for the speed of the feed motor 29.

A suction fan 40 is provided in the upper compartment 4 and is carried upon the vertical shaft 4I directly driven by an electric motor 42 mounted upon the top wall 43 of the fan-chamber or casing.

The shaft 4| extends downwardly and carries a centrifuge 44 which is located directly above and overhangs the mouth of the' hood or'i'nner casing 22. A division wall 45 is located between the centrifuge and the fan 40 and is provided with a central opening 46 preferably slightly smaller than the diameter ofthe centrifuge 44.

A perforated screen 41 surrounds the centrifuge 44 `and is spaced from the wall or outer casing 3` to provide a dead air space 48 into which the 4larger particles of coal may pass after being thrown outwardly 'by the centrifuge 44 through ythe apertures in the screen 41. The lower end ofthe screen 41 is unattached so that the space 48 communicates with the space 24, thus allowing the heavier and larger particles of coal to immediately pass from the rapidly travelling stream of coal laden air into 'a dead air space and thereafter return to the pulverizing mill or hammer mill.

It is preferable to provide lan 'annular flange 49 above the centrifuge 44 to prevent particles of coal thrown outwardly by the centrifugal action of the centrifuge from glancingupwardly through the opening 48. f

From actual operation of a machine constructed in accordance with this invention, it has been As a comparison it may be noted that the latestv types of ball or roller mills give approximately 60% that willV pass through a 200 mesh screen,

' while the usual `typesof hammer mills now give ,cari

will pass through a 200 be Vfully understood, it is believed that the feeding of the coal tangentially into the hammer mill and the drawing of the dust laden air from each side at the center ofthe hammer mill, coupled with the upper centrifuge and the means for directly removing the larger particles from the rapidly moving air stream and returning them to the hammer mill, both jointly and severally contribute to theunsual results obtained.

lThis machine also possesses great flexibility in the amount of fuel it can supply. For instance, actual. tests show that it is capable of satisfactory operation either at great overloads or at loads below normal, even as low as.42%. This variation is secured by making the fan motor tt a variable speed motor and by the proper adjustment of the butterfly valve 2t. In addition, the motor l2 may be made a variable speed motor, it desired. V

Thus it will be seen that a. novel form of pulverizer has been provided which will pulverize the coal to a remarkable degree of neness, which may be operated to supply overloads, and which also may be run as slowly as desired and still give perfectly satisfactory results. These features supply a demand that has long existed and provide a means whereby great flexibility of operation is obtained together with an unusually iinely powdered fuel supply. Y.

It will be seen further, that the device is selfcontained, is compact, is easy to construct, control and install, and is highly emcient in operation.

Although the invention has been described in considerable detail, it is to be understood that the description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claimzl. In a material reducing machine,'a centrfug for separating the larger particles from the finer particles, said centrifuge comprising a rotary member, means for feeding the particles entrained in an air stream centrally of said member, a casing surrounding said member and provided with an unobstructed chamber for said rotary member, said casing having a large area around and below said rotary member constituting a separating space for said particles, said casing having a bottom portieriA leading to a discharge outlet for said larger particles, an outer lip on the outer side of the discharge outlet, an inner lip on the inner side of saiddischarge outlet, an inlet air passageway for conducting incoming air past said outer lip. and means for creating a current of air past said inner lip, saidl 2. In a material reducing machine, a centrifuge for separating the larger particles from the ner particles, said centrifuge comprising a rotary member, means for feeding the particles entrained in an air stream centrally of said member, a casing surrounding said member and providing an unobstructed chamber for said rotary member, an unbroken annular baiile located within the casing and above said rotary member, said casing having a large area around and below said rotary member constituting a separating space iior said particles, said casing having a downwardly slanting bottom leading to a discharge outlet, an outer lip on the outer side of said discharge outlet, an inner lip leading from the inner side of said discharge outlet, said machine having an inlet air passageway extending past said outer lip, means for creating a current of air through said passageway outwardly past said outer lip and on the outer side of said outer lip, means for creating a current of air outwardly from said inner lip and on the inner side of said inner lip, whereby a suction is produced between said lips to suck the larger particles outwardly from between said lips.

3. In a material reducing machine, a centrifuge for separating the larger particles from the finer particles, said centrifuge comprising a rotary member, means for feeding the particles entrained in an air stream centrally of said member, a casing surrounding said member and providing an unobstructed chamber for said rotary member, said casing having a large area around and below said rotary member constituting a separating space for said particles, said casing having a substantially centrally located opening above said rotary member, the periphery of said rotary member being spacedfrom said casing to provide an area many times greater than the area of said opening, said casing having a downwardly slanting bottom provided with an outlet portion, an outer lip located on the outer side of said outlet portion, an inner lip extending from the inner side of said outlet portion, said machine having an inlet passageway extending downwardly past said outer lip, and means for producing a current of air downwardly past said outer lip and outer side of said outer lip and past said inner lip on the inner side of said inner lip, whereby suction is produced to suck the larger particles outwardly past said lips.

4. In a material reducing device comprising aV vforming a reducing chamber, means for introducing material and air into the front part of the chamber, material reducing means in said chamber, a passage formingmember located in an intermediate part of the housing and connecting the reducing chamber to the upper part of the housing, said passage forming member being spacedfrom the walls of said intermediate part of the housing and having its lower end sloping downwardly and forwardly, a gutter forming member connecting said lower end with the housing, balile means carried by said passage forming member, means for directing the material passing down the gutter forming member into the front part of the reducing chamber in front of the reducing means, the top part of the housing having an outlet passage therein, and a fan in the top part of the housing which discharges the

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