US1788825A - Pulverizer - Google Patents

Description

A.C.DANKS Jan. i3, 1931.

PULVERIZER Filed Sept. 5, 1929' 2 Sheets-Sheet 2 INVENTOR Patented Jan. 1 3, 1931 ALFRED C. BANKS, OF CLEVELAND, OHIO IULVERIZER Application filed September 5, 1929. s r 390,515 I The invention relates to pulverizers, and

more particularly coal ulverizers, although the machine may be app ied to the pulverizing of rock or other-solid material which it'is desired to bring to a finely divided condition. Heretofore, two main types of machines have been used in pulverizing coal, the ball machine, and the impact mill. The ball mill. operates at a relatively low speed and at a low' pockets form in the drum, which leads to irregular burning, when the mill is used below maximum capacity. The impact mill, on the other hand, works at a high speed, as compared with the ball mill, and the impact of the arms or paddles on the fuel and the impact of particles of fuel or other particles eiiects the necessary pulverizatiom In th1s mill only a part of the air required for combustion is used to carry the fuel through the mill, and this feature permits a flexibility of operation, since the amount of carrying air may be regulated to correspond to the quantity of fuel being reduced. This form of pul-.

verizer also gives complete control ofthe fineness of the product depending on the speed at which the material is fedto and, through the mill. This form. of mill has the disad- 9 vantage that the power consumed per ton of material is high compared with the ball mill,

and the cost of maintenance is high due to the high speed operation and to the abrasive action of the coal upon the parts of the machine.

The object of the present invention is to provide an apparatus havingthe advantages of both the ball mill and the impact mill without the disadvantages of either. The apparae tus uses balls, as in the ball mill, and operates at a relatively slow speed. At the same time provision is made for controlling the fiowof coal and air through the drum in such manner that only; a small proportion of the total air required for combustion is used as carry ing air. This gives the same fle'xibilit of operation as with the impact mill and the same capability of operating at any desired'capac- 1ty without any reduction in the efiiciency of the apparatus or in'the' uniformity of fuel feed. 'One embodiment of the invention is shown in the accompanying drawings, where in: i o

Figure 1 is a longitudinalsection through V the apparatus. Fig. 21s a transverse section 00 V on the line 'IIII of Fig. 1. Fig. ,3 is a trans verse section on the line III-'-III of Fi -1. tAnd Fig. 4 is a section showing a modi caion.

Referring tothe drawings, 1. isa cylindrical steel shell, preferably a boiler plate in which are placeda series of castings 2 made. in sections so as toform a complete ring running at right angles to the axis of rotation of thepulverizer. These castings may be chilled 7 castiron, manganese steel, 'or any othermaterial made for the purpose of withstandin abrasion. They maybe placed in any desired number and of any desired diameter, and may be placed either in a straight line or they may 7 be placed inincreasing or decreasing diameters from the inlet end of the pulverizer, as seen fit. f i i In these grooves are placed ballsA of large diameter, a sufiicient number being placed in so each groove to insurepulverization of the materialthat passes from. one stage to the other,*the largeballs being placed near the inlet. Thenumber of balls in these'grooves and their size will depend upon "the size'of the unit under consideration, but the purpose of the balls and the groove is to get as lar e surface contact between the balls and tile groove as possible rather than to depend upon the line, contact that is secured in the ordinary ball mill, when the ballstouch each other in the normal process of revolving with the shell. I 1

The small amount carrying air, as it has been termed, up to possibly 10 er cent'of the total required, is admitted t rough the feedplate 3 and through the space 4, and under some conditions, arrangements may be made for adjustments at" these points to govam this air. This air, in turn, moves through the pulverizer passin between the ends of the castings 2 and t e edges of the diahragms 5 fastened to the drum 6. The eight of these diaphragms 5 may be varied to regulate the flow of air and material through the mill and thus increase or decrease the speed of material passage from one coal stage to the other. This how causes the material to leave the first stage after it has become filled. pass over the e ge of the castings through the ga 7 and fill the second stage and progress in a ike manner throughout the entire unit, until it reaches the final sta e. Here it asses the last diaphragm 5 an discharges't rough ports 9 in the drum. The shell 1 is sup orted from a second lar er shell 10, also 0 boiler plate by means of t e spreaders 11 and bolts 12, and the space thus provided between the two sheets const tutes a passageway for the main body of air required for combustion, such air flowing in through the annular openings 13 and 14' and past the fan 15 through the pipe 16 to the point of combustion. The mixture of air and powdered fuel from the ports 9 is thus mixedwith the main body of air flowing inward from the opening 14 to the end of the pipe 16. The fan 15 may be located at any point along the line of flow and is driven from a motor 17 mounted on the base 18, such base being in turn mounted on the main supporting base 19.

In the event of the speed becoming such that there becomes a tendency for the balls to leave their rooves when carried above the center line of 51c mill, additional diaphragms 8a of suitable cast material and made up in sections are bolted to the drum 6 that will prevent this action. These may be substituted, if necessary, for the discs 5 and used by their varying lengths to determine the flow of material through the mill in the same manner as referred to under the discs 5.

The feed plate 3 is of the usual type comprising alternating bars and slots and is driven from the motor 20 through the gearing in the casing 21 and the speed changing means comprising the pair of stepped pulle s 22, 22, the belt 23, the worm wheel 24, t e shaft 25, which carries the plate 3, and a worm carried by .the shaft which carries the upper stepped pulley 22. The coal is fed from the hopper 26 by gravity past the plate 3 andthrough the inclined pipe therebeneath. H The shell 10 is provided with a head 27 which may be removed topermit the removal of the drum 6, such drum being carried on a separate head 28, which is removable for repalrs. The outlet pipe 16 is supported on the motor base 18 by means of brackets 29, 30, with a suitable joint at 31, which allows the head 27 to revolve while the pipe 16 is stationary, suitable means being provided to make the joint tight. The drum 6 and its discs or diaphragms 5 and 8a are attached rigidly to the shell 1 throu h the head 27 and revolve with the shell. T e diaphragms or discs 5 and 8a may be replaced by 0t ers of varyin diameters to give varying flows of air an material through the mill, epending upon the conditions encountered.

Fig. 4 shows a construction in which the discs 5 are omitted, and if desired, with the mill runnin at a speed low enough to avoid displacing t e balls from their runways, the discs 8a may be dispensed with, the discs 5 serving by themselves to give the desired restriction to the flow of material and air through the annular space between the drum 6 and the runway castings 2.

A wear plate 32 is shown at the inlet end of the mill and is fastened to the front head 33, which is removable from the shell 1 to provide access for repairs or for replacing the castings 2.

When desired, air of high tem erature or preheated air may be sup lied t rough the mlet 13, which expedient acilitates the drying of the coal, so that a more effective pulverizing action is secured in the runways carrying the balls. It will also be understood suitable dampers ma be provided when desired to control the ow of carrying air and the main body of air which is independent of the supply of carrying air.

The shell 10 and parts carried thereby are rotated from the motor 20 which drives the shaft 34 through the intermediary of suitable reduction gearin in the casing 21. The shaft 34 is provi ed with a gear 35 which enga es the s ur gear 36 secured to the shell 10. he shel 10 1s also provided with bands 37, 37 engaged by a series of rollers 38, 38 carried by shafts 39 mounted in suitable bearings 40 mounted in the base casting .19. The form of feed mechanism for supplying the coal to the drum is immaterial insofar as the present invention is concerned, and the feeder 3 may be replaced with an one of the standard commercial feeders which are available. such as a belt section to which a variable speed drive may be applied.

What I claim is:

1. In combination in a coal pulverizer, a drum mounted for rotation and provided on its interior with a series of annular ball races,

a set of balls mounted in each race, means for rotating the drum, means for supplying the coal to be pulverized to one end of the drum, a series 0 diaphragms arranged in spaced relation longitudinally of the drum with their peripheries spaced away from the walls of the drum, an air inlet to the end of the drum to which the coal is sup lied, an outlet conduit leading from the ot er end of the drum, means for causing a flow of air therethrough to conduct from the drum a mixture of pow- .dered coal and air, and an annular inlet passage around the drum extending longitudina 1y thereof and communicating with the ios let at the end of thedrum so that additional air is supplied at this point to the mixture of gowdered coal and air flowing into said con-' uit.

2. In combinationin a coal pulverizer, a drum mounted for rotation and provided on 1 its interiorwith a series of annular ball races, a set of balls mounted in each race, means for rotatin the drum, means for applying the coal to e pulverized to one end of the drum, asecond drum inside the first drum with which the first drum communicates at itsoutsaid conduit.

an; first let end, a series of diaphragms arranged in spaced relation along .the second drum with "their peripheries spaced away. from the wall fthef. first drum, an air inlet tothe end of ,tl'et leading from the other end of the drumxin opposition to the end of the second drui'ng and an annular inlet passa e aroundthe first-drum extending longitudina'lly thereof and communicating with said outlet at the end of the drum sothat addiq tional air is supplied at this point to the mixture of powdered coal and air flowing into an inlet leading from the atmosphere to the mixing chamber for supplying additional air theret In testimony whereof, I have hereunto subscribed my name this 31st day of August,

1929. a i I no ALFRED o. DANKS.

first drum to which the coal is supplied,

3. In combination in a coal pulverizer, a g

drum mounted for rotation and provided on its interior with a series of annular ball races, a set of balls mounted in each race, means for rotatin the drum, means for supplying the coal to be pulverized to one end of the drum;

a second drum inside the first drum with which the first drum communicates at its outlet end, a series of diaphragms arranged in spaced relation along the second drum with their peripheries spaced away from the wall of the first drum, a mixing chamber into which the end of the second drum discharges,

an air inletto the end of the first drum to whiclithe coal is supplied, an outlet leading rotating the drum, means for supplying the coal to be pulverized to one end of the drum,

a second drum inside the first drum with which the first drum communicates at its outlet end, a series of diaphragms arranged in' spaced relation along the second drum with their peripheries spaced away from the wall of the first drum, a mixing chamber constituting an extension of the end of the first drum into which the end of the second drum discharges, an exhaust fan located in said chamber, an air inlet to the end of the first drum to which the coal is supplied, an outlet leading from said mixing chamber in opposition to the end of the second drum, and

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