US2431746A - Bowl mill with vane means providing uniform velocity upwardly swirling air currents - Google Patents

Description

BOWL MILL WITH VANE MEANS PROVIDING UNIF ORM VELOCITY UPWARDLY SWIRLING AIRCURRENTS Filed Aug. 25, 1944 3 Sheets-Sheet 1' D.2, 1947.. G. H. FRANGQUIST K 9 2,431,746

n b A e.-H. FRANGQUIsT 2,431,746 BOWL MILL WITH VANE MEANS PROVIDING UNIFORM Dec; 2, 1%7.

VELOCITY UPWARDLY- SWIRLIN G AIR CURRENTS Filed Aug. 25, 1944 5 Sheets-Sheet 2 Dec. 2, 1947. H. FRANGQUI 2, ,7 BOWL MILL W VANE MEANS PRO ING UNIFORM VELOCITY UPWARDLY SWIRLING AIR CURRENT-S Filed Aug. 25, 1944 3 Sheets-Sheet 3 mp. U l

I 1 I I v/ I, I IN "MI! I It i v v Patented Dec. 2, 1947 FFICE BDWL MILL WITH VANE MEANS PROVIDING UNIFORM VELOCITY UPWARDLY SWIRL- ING AIR CURRENTS Gustav H. Frangquist, Chicago, Ill., assignor to Combustion Engineering Company, Inc., New York, N. Y., a corporation of Delaware Application August 25, 1944, Serial No. 551,130

4 Claims.

This invention relates to pulverizing apparatus and has for its principal object the provision of a new and improved form and arrangement of parts whereby the air currents, utilized for carrying the pulverized material out of the apparatus, may be maintained at uniform velocity at all locations within the apparatus whereby the material, when sufiiciently pulverized, will be discharged without undue suspension and consequent circulation of the heavier particles of material in the air current.

The invention as herein illustrated is designed particularly for use in connection with bowl mills, such as are illustrated in the Crites United States Patent No. 2,112,359, granted March 29, 1938, although the invention is not to be restricted to use in connection with such apparatus, except so far as the claims may be so limited.

In a pulverizing apparatus of the general class herein shown, a comparatively shallow bowl is given rotary movement about a vertical axis within a closed casing or housing. Two or more rollers are rotatably mounted and extend into the bowl so as to have a crushing effect on particles carried around on the upwardly and outwardly inclined face of the bowl. The parts are arranged so that there is an annular opening between the outer wall of the bowl and the inner wall of the housing through which air introduced in the space below the bowl moves upwardly so as to pick up and float away pulverized material forced over the edge of the bowl.

One object of the invention is to provide an improved arrangement whereby the air introduced into the housing will be so distributed about the periphery of the bowl as to avoid the formation of high and low velocity zones in the air and thereby prevent substantial quantities of insufficiently pulverized material from being suspended in the higher velocity air zones and carried upwardly through the apparatus. This result has been accomplished in the preferred construction by the use of an arrangement comprising a series of vanes in spaced relation to each other about the bowl, such vanes being in substantially radial position but disposed obliquely at a suitable angle from the horizontal, with the upper ends of the vanes in the lead with respect to the direction of rotation of the bowl. The size of the annular opening between the bowl and the wall of the casing or housing is such with respect to the size of the stream of air introduced into the housing that the distribution of the air about the entire periphery of the bowl is assured, and the angular positions of the chute 22.

vanes insure that the several portions of the stream of air between successive vanes shall be directed forwardly and upwardly with respect to the direction of rotation of the bowl and that oversized material, finding entrance between the vanes will be deflected upwardly thereby and carried in the air stream back into the bowl of the mill.

Another object of the invention is to include the provision of the improved constructions and arrangements herein shown and described in connection with one approved form of apparatus.

Fig. 1 is a central vertical sectional view through one preferred form of bowl mill, showing the improvement of the present invention incorporated therein.

Fig. 2 is a horizontal sectional view taken substantially at the line 22 of Fig. 1.

Fig. 3 is a perspective view of a fragmentary portion of .a horizontal plate mounted at the upper face of a duct through which air is delivered into the apparatus, showing in position one of the vanes of that portion of the series of vanes.

Fig. 4 is a perspective view of the vane structure of Fig. 3.

Fig, 5 is an enlarged detail view substantially similar to a portion of Fig. 2, being substantially a horizontal sectional view taken at the line 55 of Fig. 6, and

Fig. 6 is a vertical sectional View taken substantially at the line 6-6 of Fig. 5.

Referring now to the several figures of the drawings, in which corresponding parts are in dicated by the same reference characters, IS indicates a base plate suitably secured in position, upon which a housing or casing I6 is fixedly mounted. Within the housing l6, a bowl I! of approved type is rotatably mounted so as to be driven through the medium of a vertical shaft i8 which in turn is driven by suitable driving mechanism in the gear housing I9 below the base plate I5 so as to cause the bowl to rotate in clockwise direction in Fig. 2.

In the arrangement shown, the bowl I! is provided with a grinding ring 20, with which three rollers 2| cooperate for crushing and pulverizing material fed into the bowl through a Each of the rollers 2| is rotatably mounted in position by means comprising a sleeve assembly 22 engaging the roller and freely rotatable on a shaft 23. The shaft is fixed in an outer sleeve 24 which is pivotally mounted on a horizontal axis at 25. An arm 26 fixedly mounted on the sleeve 24 has an effective bearing on the upper end of a coiled spring 21, the lower end of which bears against a bracket 28 held rigidly in position with respect to the housing IS. The arrangement is such that the springs 21 press the rollers 2| yieldingly toward the grinding ring 20. As is best shown in Fig. 1, each of the sleeves 24 extends upwardly through a suitable opening at the top face of the housing l6 into a deep inwardly pressed groove 29 in the outer face of an extension casing member 30 secured above the casing memb'er I6, means being provided preferably about the sleeves 24 for preventing the escape of air.

As is best shown in Fig. 1 ,'the bow-l I 1 is spaced a short distance from the inner face of the housing l6 so as to provide an annular opening between the bowl and the housing, the arrangement being such that a stream of air introduced either by suction or pressure into the housing l6 below the bowl is caused to rise through the annular opening so as to pick up 'and'iloat away particles (if material which have been sufilcient'ly pulverized in the bowl of the mill and forced upwardly and outwardly therefrom during the grinding operation. The suspended particles which are insufiiciently pulverized are deflected inwardly by angular deflectors Hie, secured to the inner wall of the housing, and thereby returned to the bowl I! for further reduction.

It is the principal object of the present invention to provide an improved arrangement by which a stream of air fed into the housing I6 is caused to be distributed as desired about the periphery of the bowl, it being the object in many instances to make the distribution of the air substantially uniform throughout the entire circumference of the bowl.

The air rising through the annular opening between the bowl and the housing passes upwardly along opposite sides of the inwardly pressed portions 29 of the housing and is carried upwardly along the upwardly flared shell 3i, thence through a series of openings'32 through the upper edge portion of the shell 3!. The air is then deflected downwardly a short distance in order to gain access to the delivery pipe 33 through which the air and the particles held suspended therein are discharged from the apparatus, The force of the air is such as to hold in suspension particles of the material being pulverized which approximate a predetermined size and Weight. Any particles of material of excessive size carried by the air stream above the deflectors W will be caused to pass on downwardly when the direction of the air changes at the lower end portion of the pipe 33, 'such oversize particles being d'elivered through an opening at 34 through the shell 31 again into the bowl I directly below for further pulverizing action.

The means for causing the desired distribution of the air stream about the periphery of the bowl I! will now be described. Preferably the size of the air stream fed into the housing 16 is such with relation to the size of the annular opening between the bowl and the housing as to cause necessarily more or less distribution of the air about the bowl. The air is fed into the housing I6 through a duct 31. In the embodi ment shown, the said duct 31 is located at one side of the center of the chamber and 'consequently causes the air to follow a circular path corresponding to the direction of rotation of the bowl I! and to the general path of travel of the material discharged from'the bowl.

As is best shown in Fig. 1, where a portion 75 neath' the bowl.

of the bowl l1 and grinding ring 20 are broken away for clearness of illustration, a series of vanes 38 are fixedly mounted in the annular openings between the inner face of the wall of the housing It and the outer face of the bowl. The saidvanes may be secured in position in any suitable manner, for example, welded directly to the wall of the housing. These vanes are in oblique position at an angle of about 45 degrees from the horizontal, and are of such length as to overlap vertically, the upper ends of the vane's being in advance in the direction of rotation of the bowl and in the direction of the rotational movement of the air stream. Thesaid vanes 38, as will be seen by inspection of -1, are "arranged in radial position, so as to divide the annular opening between the bowl and the wall of the housing [6 into a series of sections between the successive vanes. The vanes 38 are mounted in spaced relation to each other as described about the entire periphery of the bowl except for a short distance opposite to the duct 31 where an alternative arrangement is provided. This alternative construction includes an arrangement of varies for stratifying the air in the upper portion of duct 31 adjacent the annular passage surrounding the bowl ll.

A baflle plate 39, having a height equal to the adjacent vanes 38, is provided within the duct 31 for deflecting the entering #air, such baffle plate constituting in effect a portion of the wall of the housing l6 and having a plurality of vanes 38 mounted thereon.

Across the top face of the duct 31, a transversely positioned plate 40 is provided, having its inner "edge curved in substantially concentric relation to the periphery of the bowl. Secured to the bottom face of the transverse plate Ml are a plurality of air stratifying plates 4! in oblique position at an angle of approximately degrees from the horizontal and extending in substantially parallel relation with respect to each other and with respect to the duct 31-. These plates -41 carry vanes '42 corresponding in size and shape with the vanes 38., and extending like the vanes '38 into close proximity to the periphery' 'of the bowl I I. The vanes 12 are in radial position with respect to the bowl, and are obliquely disposed with each v-a'n'e at an angle of about 45 'degrees from the horizontal. The arrangement is such that the vanes 42 complete the series of vanes 38 so as to provide similarly function- .ing vanes about the entire periphery ofthe bo'wl.

With a stream of 'air entering the housing 16 through the duct 31,'and with such stream or air moving in clockwise direction about the chamber of said housing 'I'B as seen in Fig, 2, such air finds its way readily between the vanes which are disposed "so as to receive the air with a minimum of change of direction. The arrangement is such that the air is distributed quite evenly among the comparatively large number of openings between successive vanes, so as robe caused to rise close to the periphery of the bowl in position to pick up pulverized particles as they are forced upwardly and outwardly from the bowl.

The spaces between the several vanes 38 and between the several vanes 4'2 are such 'as 'to perini t large pieces of waste material, for example tram iron which may be present in the materialbeing pulverized but which is not readily pulverized by the rollers 2-3 to pass downwardly between adjacent vanes and into the'space be- This waste material is swept from the bottom of the chamber beneath the bowl H, by means of one or more scrapers 35, into a discharge chute 36. The oversized particles of coal, or other material being pulverized, which are relatively light in weight in relation to the trap iron waste material and which may find entrance in the spaces between the inclined vanes will be blown upwardly into the bowl, the inclined vanes serving as deflectors which cooperate with the force of the air stream to return such particles to the bowl of the mill. However, the heavier particles of foreign material will pass downwardly between the vanes into the lower chamber of the casing.

By the use of the improved construction, an effective control of the air current is assured so as to provide good results by the use of a minimum strength of air current and so as to enable the use of the pulverizing apparatus to advantage for pulverizing coal for feed directly to a furnace. With the air moving under control smoothly along the faces of the walls or at a sharp angle with respect thereto rather than moving with a high degree of turbulence directly toward the walls, the effectiveness of the air current for carrying away the pulverized particles by a flotation effect is greatly increased, and the efficiency of the apparatus is correspondingly increased.

While the form and arrangement of the parts as shown in the drawings and as above described are preferred, it is to be understood that the invention is not to be limited to such arrangement except so far as the claims may be so limited, changes being well made in the arrangement without departing from the spirit of the invention.

I claim:

1. A pulverizing apparatus, comprising in combination a housing, a bowl rotatably mounted in said housing with an annular opening between the bowl and the wall of the housing, means for rotating the bowl in said housing about a vertical axis, means operative in said bowl for pulverizing material fed to the bowl, a conduit for directing a stream of air into said housing in a path substantially tangent to the inner wall thereof'so as to move upwardly through said annular opening and at the same time to move about the outer face of the bowl in the same direction as that in which the bowl is rotating, and vanes extending below the upper portion of said conduit and arranged in substantially radial position in said housing in spaced relation to each other at the inner face of the housing with their inner ends in close relation to the outer surface of the bowl so that the vanes divide the stream of air into a plurality of sections between successive vanes for obtaining a predetermined distribution of the air about the bowl.

2. A pulverizing apparatus, comprising in combination a housing, a bowl rotatably mounted in said housing with an annular opening between the bowl and the wall of the housing, means operative in said bowl for pulverizing material fed to the bowl, means for rotating the bowl in said housing about a vertical axis whereby the material pulverized therein is thrown outwardly therefrom and carried in a general circular path adjacent the wall of the housing, a conduit for directing a stream of air into said housing in a path substantially tangent to the inner wall thereof so as to move upwardly through said annular opening and at the same time to move about the outer face of the bowl in the same direction as that in which the bowl and said discharged material is moving, and vanes between said bowl and said housing arranged to extend below the upper portion of said conduit and in oblique position with their upper ends in advance with respect to the direction of rotation of said bowl so as to function as deflectors for returning oversize particles of material to the bowl.

3. A pulverizing apparatus, comprising in combination a housing, a bowl rotatably mounted in said housing with an annular opening between the receptacle and the wall of the housing means for rotating the bowl in said housing about a vertical axis, means operative in said bowl for pulverizing a material fed to the bowl, a duct leading into said housing opposite to said bowl for the introduction of a stream of air into the housing so as to rise through said annular opening, vanes mounted on the inner face of the housing in oblique position at a substantial angle extend below the upper limits of the duct and arranged in oblique position corresponding to the position of said first-named vanes and serving with said first-named vanes to complete a series of vanes substantially about the periphery of the bowl.

4. A pulverizing apparatus, comprising in combination a housing, a bowl rotatably mounted in said housing with an annular opening between the bowl and the wall of the housing, means for rotating the bowl in said housing about a vertical axis, means operative in said bowl for pulverizing a material fed to the bowl, a duct leading into said housing opposite to said bowl for the introduction of a stream of air into the housing so as to rise through said annular opening, vanes mounted on the inner face of the housing in oblique position at a substantial angle from the horizontal in spaced relation to each other about the major portion of the housing, a transverse plate extending across the upper face portion of the duct adjacent to said bowl, a series of spaced apart supporting plates depending from said transverse plate opposite to said bowl, and vanes mounted on said supporting plates in oblique position corresponding to the position of said first-named vanes and serving with said firstnamed vanes to complete a series of vanes substantially about the periphery of the bowl.

GUSTAV H. FRANGQUIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,955 960 Hersch Apr. 24, 1934 2,112,359 Crites Mar. 29, 1938 2,237,021 Wood Apr. 1, 1941 1,697,704 Wood Jan. 1, 1929 1,806,980 Krentzberg May 26, 1931

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