US2351870A - Combined ball mill and drier - Google Patents

Description

June 20, 1944.

R. c. NEwHousE. Y' 2,351,870 COMBINED BALLNMILL AND DRIER Filed Defc. 2e, 1940 `:a sheetsfsheet 1 June 20, 1944.' R, c, NEwHousE COMBINED BALL MILL AND DRIER Filed Dec. '26, 1940 2 sheets-Sheet 2 e L m. M M H Vm s a L m A Vm M v s Ww ,m f M M R E 1 w .M

M ./x HT, .L M c [L Y. E a V F 6L am All A@ r M C OLLEc To@ y AM #EA TER H07' AIR HVPASS 7'0 HOUSING Patented `lune 20, 1944 stares rara erstes COMBINED naar. mi. A'Nn paisa Ray G. Newhouse, Wauwatosa,

wis., assigner te Allis-Chalmers Manufacturing Qompany, Milwaukee, Wis.,

a corporation of Delaware Application D ecember 26, 19.40, Serial No. 371,641

*.7 Claims.

This invention relates generally to the drying of moist materials and more particularly to a manner of and means for pre-drying the moist materialprior to the first or thereof.

'Ihe nature and the moisture content of the material to be ground may --be such that the ground material agglomerates and/or adheres to the grinding media employed thereby materially reducing the capacity of the mill and materially increasing its power consumption. The agglomeration and the adhesion of the ground material to the grinding media and to the other parts of a mill presents series operating diiilculties, particulariy with respect to tube mills, which in some instances has necessitated complete and frequent shutdowns. Thel known types of tube mills designed to overcome these difiiculties, such, for

example, as'that illustrated by United States Patent to Hidoux No. 1,614,364, issued January 1l. 1927, Combined drying and grinding machine for clay and other plastic materials, employ a relatively long predrying chamber through which is passed a heated gas and through which the moist material is conveyed by the inclination of the tube vand by the inclined or helical vanes or ribs disposed therein. However, the known types of tube mills are objectionable in that (1) the initial cost is excessive, (2) a large space is required for'installation and operation which materially increasesplant costs, (3) the power consumption is excessive which materially increases operating costs, and (4) the manner of predrying employed is ineiiicient which also increases operating costs and materially reduces the overall efficiency of the mill.

In accordance` with this invention, the moist material is dried or partially dried by showering the material through a stream of heated gas transversely with respect to the direction of gas iiow and mixing the showered and partially dried material with additional moist material before subjecting the additional moist material to the showering-action. Some of the material which has been mixed and then showered through the heated gas stream is then withdrawn and g'round and the remainder is retained and mixed With the preliminary grinding incoming moist material to eiect a preliminary dry ng action which precedes the further drying action effected by showering the mixture through the stream of heated gas. In other Words, once this procedure has been initiated, the incoming moist material is sequentially subjected to two drying actions, namely, (1) a preliminary drying action effected by fdirect contact between the moist particles and the previously showered and partially dried particles during the mixing operation, and (2) a further drying action effected by then passing the mixture of moist and partially dried particles through the stream of heated gas.

An important object of this invention is to provide an improved method of drying moist material which, when the dried material is to be ground, may be carried out in a'tube or other type of mill Without materially increasing the initial and operating costs thereof.

Another important object of this invention is to provide an improved mill compactly incorporating a novel combination of features operative to efficiently predry moist material inV accordance with the method herein disclosed.

Still another object of this invention is to provide an improved tube mill embodying apparatus for practicing this invention compactly arranged in a non-grinding preliminary drying chamber of relatively small axial length.

A further object of this invention is to provide an improved tube mill embodying apparatusfor practicing this invention compactly arranged in a non-grinding preliminary drying compartment of relatively small axial length intermediate the material inlet and discharge openings therein so as to interpose a curtain of showering material between said openings and thereby prevent incoming moist material from passing directly through said compartment without being subjected to the mixing and showering operations performed therein.

The invention accordingly consists of the various methods and of the various features of construction, combinations of elements and arrangements of parts as more particularly pointed out in the appended claims and in the detailed description, in which:

Fig. 1 is a longitudinal vertical section through a tube mill embodying the invention; l

Fig. 2 is a partial transverse vertical sectionthrough the mill taken on line lI-IIof Fig. 1;

Fig. 3 is a section illustrating the cone discharge member 'taken on line III-III of Fig. 1; Fig. 4 is another transverse vertical section through the mill taken on lines IV-IV of Fig.

. g having opposite ends of reduced diameter providing axially extendinginlet en". portions 3 and 4. The shell is mounted for rotation about its longitudinal axis on axially spaced end bearing structures 9 and 1 which coact with and support the axially extending end portions 3 and 4, respectively. The shell is rotated in said bearings by means of the ring gear 8 which is attached thereto and which in turn isadapted to be driven4 by anysuitable means such as a gear connected driving motor (not shown).

The interior of the shell 2 is provided with axially spaced means which coact and divide the interior of the shell into a preliminary' drying compartment 9, a preliminary grinding compartment II, and a final grinding compartment I2. The means separating the drying compartment 9 from-the preliminary grinding compartment II comprises an' annular plate I3 having a'central opening I4; a lifting vane assembly consisting of a cylindrical ring I5, which is preferably vremovably secured to the inner periphery of the shell 2 by any suitable means such as bolts I6 and to the inner periphery of ywhich is secured a series of circumferentially spaced inwardly extending radial vanes I1 which are generally I-shaped in cross-section, asbest shown in Fig. 3, and a pair of annular rings I6 which are secured in any suitable manner, suchas by welding or brazingv to the opposite inner side portions of the vanes I1, as best seen in Figs. 1 and 2; a hollow cone member `I9 having a flanged base portionv 29 which is preferably removably secured to a ring Il by any suitable means such as cap screws 2l; and an annular series of lifting members 22, each of which hasv an arcuate bottom wall `23, an inwardlyextending radial end wall 24, and an inwardly extending arcuate side wall 26. The inner edge of the side wall 26 is enlarged to provide an arcuate material defiecting portion 21. The-lifting members 22 which are preferably removably secured to the inner periphery of the shell ,2 by any suitable means such as the bolts 2l, coact with each other and 'with the adjacent end wall portion of the shell 2 and define an annular series of lifting compartments 29.

` Stated differently, the means defining and separating the drying compartment from the grinding compartment comprises a hollow, partition structure including in axially spaced proximate relation a grinding compartment wall I3 having a central opening I4 therethrough and a drying compartment having an annular coaxial opening 3l therethrough formed by a central portion (cone member I9) positioned opposite and in air deecting relation to the inlet opening in the reducedend portion 3 of the drum and in opposite shielding relation to the central opening. I4 and by an outer annular material retaining portion (the abutting side walls 26 of lifting members 22) spacedly surrounding the central portion,

that is the base of cone member I9. In this connection, it should be particularly noted that the inner diameter of the annular wall I3 is considerably less than'the inner diameterof the outer annular material retaining wall portion formed by the abutting side walls 26 of lifting members 22, that the central opening I4 is of nearly the same diameter as the base of cone member I9, and that the annular coaxial opening 3I is in effect defined by radially spaced inner and outer wall portions (the base of cone member I9 and the side walls 28 of members 22) which extend nearly equal distances from the longitudinal axis 76 and from the periphery of the drum, respectively.

- and the annular plate I3. The annular opening 3l defined between the inner vedges of the side walls 26 of the lifting members 22 and the'ba'se portion 29 of the cone member I9 places the interior of the drying compartment 9 in communication with the space between said side walls 26 and the annular plate'l3. When the shell 2 is rotating, material entering the space between said side walls and the said annular plate is elevated in the lifting compartments `3|) and then gravitates onto the cone member I9 which directs the gravitating material through the opening I4 in the plate I 3 and into the-preliminary grinding compartment II'. Consequently, the cone member I9 and the lifting vane assembly disposed between the annular plate I3 and the lifting members 22 provide in effect a material conveying means which is operative when the shell is rotating to conduct the material passing through the f annular opening 3| into the preliminary grinding compartment II.

The means separating the preliminary grinding compartment II from the final grinding compartxnent I2 comprises an annular perforated plate 32 having a central opening 33 therein', a

lifting vane assembly consisting of inner and' outer pairs of axially spaced annular rings 34 and 36, respectively, between which are secured an annular series of circumferentially spaced radlally extending spacing blades 31, and a circular plate 38 which, if desired, may be removably secured to the side surfaces of the adjacent inner and outer rings 34 and 36, respectively, in'any suitable manner such as by bolts or screws (not shown). The annular perforated plate 32 may also be removably secured to the side surfaces 'of the adjacent inner and outer rings 34 and 36,

respectively, lin a similar manner. The shell is provided with an annular series of circumferentially spaced openings or slots 39 which places the interior of a collector housing 35 in communication with thespace between the plates 32 and 38, The collector housing 35 is provided with a suitable material conveying means such as the helical screw 4I. The interior of the final grinding compartment I2 is provided with any suitable grinding media such as the steel balls 42 and withribbed or corrugated liner plates 43 which are preferably made in arcuate sections (not shown) removably secured to the inner periphery of the shell in any suitable manner, such as lby the bolts 44. A circular plate 40, which closes the opening 33 in the plate 32 to prevent the coarse materialand the grinding balls 42 from entering the space Abetween the plates 32 and 38, is removably secured to the adjacent annular ring 34 by any suitable means (not shown).

The shell is also provided with a second annular series of circumferentially spaced openings or slots 46 disposed immediately adjacent the circular plate 39 to permit the passage of the .8S bolts 53.

ground material from the preliminary grinding compartment 9 into the collector housing II. Disposed in overlying relation with respect to that portion of the shell containing the annular series of openings is a grating structure comprising a slotted filler ring 41 and a superimposed grate ring 4l. The rings l1 and Il are preferably made in arcuate sections which are removably secured to the inner periphery of the shell 2 by any suitable means such as bolts (not shown). The purpose of employing two rings'in superimposed relation isv to reduce costs as the outer ring 41 may be made of a material which is less expensive than that of the inner ring I8 which must possess 'excellent wearing properties. The interior of the preliminary grinding compartment Il is also provided' with any suitable grinding media, such as and with ribbed or--corrugatedliner plates l2 which are preferably made in arcuate sections (not shown) removably secured to the inner periphery of the shell 2 by any The reduced inlet end portions 3 and l of the shell 2 are provided with any suitable material introducing means such aslthe spouts 54 and 'Si'. respectively.h The inlet end portion 3 is also connected with a conduit 51 for conducting a heated gas, such as air, from the heater 5l shown in Fig. 5. into the drying compartment 9. The interior of the reduced inlet portion 3 is pr vided with one or more helical vanes 59 which operate when the shell is rotating to prevent the incoming moist material discharged from thel suitable means such Alo " directly through the curtain member I9 and is directed rial.

the stream of heated gas passing therethrough and to mix the showered partially dried and heated material with the incoming moist mate- In this connection, it should be particularly noted that the base of hollow cone member i9 is disposed directly opposite to the inlet-opening to the chamber 9, that the diameter of the base of said cone member is nearly equal to the diameter of said inlet opening, and that therefore the major portion of the heated gas passingv of showering material impingesl against the open base end of cone thereby outward toportion of predrying chamit should also be noted that ward the peripheral ber 9. In addition,

, said inlet opening and `the discharge opening 3| the steel balls ll ed ywith the suction fan and vent conduit or stack through a bag collector.

which extends into the housing connected with an elevator which-in turn discharges the material received from the conveyer 4| into an air-separator from which the ne ground or finished material is removed by a sult- The .conveyer 4| 35 is operatively able conveyer preferably of the helical screw type l as diagrammatically indicated. The rejects or coarse material present in the `air separator is conducted to the spout 56 through which it passes into the final. grinding compartment l2. The dustfseparated from the air in the'Sirocco collector and in the bag collector is Adelivered to the conveyer 4| from whichit passes into the air separator as previously described.

In the operation of the mill, heated gas flows into` the rotating mill through the conduit 51. and the reducedinlet end portion 3 and then passes through the drying compartment 9, out through the annular discharge opening 3| and into the space including the lifting -vanes I1,

through the central opening in the circular platev I3 and-into the partment from which tor housing 35 the rings 41 and are in fact restricted relative to the diameter oi' the shell .or drum 2, thereby providing the predrying chamber 9 with a pair of axially spaced restricted inlet and cone member I 9 impinges against that portion of said stream tending to pass directly into the an- 'nula'r discharge quantity of moist material to a selected degree in a predrying space or chamber .of short axial length. This action continues until the lower portion of the drying compartment 9 becomes filled with material to a depth equal to the radial width of the side walls 26 of the lifting members 22 whereupon the introduction of additional causes a Vcommensurate quantity of the showered and partially dried material to the annular opening 3| and into the space containing the lifting vanes I1. The additional moist material mixes with the showered and partially dried material remaining within the compartment 9 and the mixture is then showered through the stream of heated gas, as

, previously stated. Consequently, the moist mais delivered, preferably in a continuing stream. from a suitable source (not shown), through the feed spout 54 and into the drying compartment 9. The lifting members 22 operateto shower the material within the drying compartment through showering material terial issubjected totwo drying -actions within the compartment 9, comprising 1) a preliminary drying action eiected by mixing the moist material with the showered and partially dried and heated material, and 2) a further drying action effected by showering the mixture through the stream of heated gas.

The deflecting portions 21 on the side walls 26 of the lifting members 22 operate to direct the showering material away from the annular discharge opening 3|, and since the lifting members 22 also operate to interpose a curtain of between the incoming moist material and the said annular discharge opening, moist material is prevented from passing directly through the drying compartment without first being subjected to the mixing and showering actions previously pointed out. Stated diierently, the introduction of additional moist material through the feed spout v54 causes-some of the previously mixedand Vshowered material to overflow into the space containing the lifting vanes outlet openings. Consequently, fthe portionof the entering stream of heated a L g'as directed outward by the open base end of the other opening, thereby quickly and eillciently drying a predetermined.'

il which operate to again shower the dried -or partially dried material through the stream of heated gas which passes through said space and into the preliminary grinding compartment Il. Some of the material which is reduced to dust in the preliminary grinding compartment Il is carried by the gas stream into the sirocco and bag collectors, as previously indicated in connection with the description of Fig. 5. The mixture of the coarser lparticles and dust is conducted by the conveyer Il at the elevator shown in Fig. 5 for further separation and grinding as previously described. e

Referring again -to Figs. 1, 2 and 4, it should be particularly noted that the side walls 29 of the lifting members 22 provide an annular wall which is arranged in opposed and axially spaced relation with respect to shell tube; that the predrying compartment 9 is thereby dened by a pair of opposed wall portions spaced apart a relatively short distance with respect to the diametrically opposed inner wall portions of the shell'2; that the heated gas flows through the predrying compartment in an axial direction; i. e.. in a direction approximately parthe adjacent end wall of the allel to the aforementioned remaining opposed wall portions; that the lifting members coact with said end wall and with said annular wall and form therewith an annular series of lifting compartments surrounding a generally cylindrical showering space having a distance therethrough in an axial direction which is relatively short with respect to its diameter (compare Figs. 1 and 4); `that when the shell 2 is rotating the lifting compartments shower material through said space in a direction yapproxin'iately at right angles to the direction of gas iiow and so as to form a substantially continuous and relatively thin curtain of showering material having relatively large oppositely facing side areas disposed approximately normal with respect to said direction of now; that the curtainof showering material has a distance therethrough measured in the direction of gas flow which is relatively short with respect to the maior dimension of said side areas; that the moist material is introduced into the predrying compartment on one side of the curtain of showering material and is moved substantially directly into contact and mixed with the showered material forming one side of said curtain; and that some of the showered material which forms the other side area of the curtain is removed from adjacent the bottom of the said other side of the curtain. In view of the foregoing it should be obvious that the disclosed and claimed procedure and apparatus permit a maximum' degreeof drying in a minimum space with a minimum quantity of heated gas.

The drying of moist material by (1) mixing moist material with dried and/or partially dried and heated material, (2) showering the mixture through a stream of heated gas, (3) withdraw.- ing some ofthe showered mixture, and (4) mixing the remainder of the showered mixture with additional moist material preparatory to the showering thereof is of particular importance, as it can be readily accomplished without effecting an appreciable movement of the material in the direction of gas flow during the mixing and showering operations. Consequently, this procedure can be readily carried out in a relatively small compartment; i. e., a compartment having a distance therethrough in one direction which is relatively short with respect to the distance therethrough in a direction approximately at right angles to said one direction, simply by passing a stream of heated gas through said compartment in a manner effective torsubstantially nll said compartment with heated gas and eiIecting the previouslystated mixing, showering, and withdrawing operations either manually or mechanically. The mixing operation can be readily carried out either within or outside of the drying compartment and the latter is preferred when the material is manually mixed.

The mechanism disclosed for inherently performing the mixing, showering, and withdrawing operations within a generally cylindrical drying compartment of relatively small axial length with respect toits diameter is also of importance, as it can be readily incorporated in a tube or'other type of mill, thereby materially increasing its capacity without materially increasing the initial and operating costs. In this connection, an important feature of the mechanism is the provision of means, such as the lifting members 22, which coact with the adjacent structure to effect the mixing, the showering, and the withdrawing operations without effecting an appreciable movement of the material toward the grinding compartment thereby rendering the relatively deep lifting compartments formed within the predrying chamber 9 effective to'act on the predetermined quantity of material retained therein and pass at least a portion of same between the inlet and outlet openings a plurality of times in a relatively thin and substantially continuous curtain of showering material having relatively large side surface areas opposing said openings. Moreover, the overowlaction operating to cause material to pass from the drying compartment into the conducting means for conveying the material into the preliminary grinding compartment eliminates mounting the mill in an inclined position to effect a conveying action, thereby materially reducing bearing costs and maintenance.

The drying of moist material in the manner herein disclosed can` be carried out by apparatus other than that shown and described for purposes of illustration, and it should be understood that it is not desired to limit the invention to the exact procedure and to the exact structure herein shown and described, as various modifications wthin the scope of the appended claims may occur to persons skilled in the'art.

It is claimed and desired to secure by Letters Patent:

1. In a drying and grinding apparatus, the improvement'comprising a drum having a coaxial inlet opening in an end wall thereof, means rotatably supporting saiddrum, a hollow partition structure disposed within said drum and defining in coaxial relation a grinding compartment and a drying compartment longitudinally spaced from each other, said partition structure including in axially spaced proximate relation a grinding compartment wall having a central opening therethrough and a dyring compartment wall having an annular coaxial opening therethrough,

between and including said walls operative when said drum is rotating to act on material entering the space between said walls and discharge same through said central opening, material showering elements positioned within said drying compartment, and means for introducing material to be dried and ground and a gaseous drying medium into said drying compartmentthrough said inlet opening.

2. In a drying and grinding apparatus. the improvement comprising a drum having a coaxial inlet opening in an end wall thereof,` means rotatably supporting said drum, a hollow partition structure disposed within said drum adjacent said end wall thereof and dening in coaxial longitudinally spaced relation a grinding compartment and a drying compartment having an axial length which is short relative to the diameter oi' the drum and relative to the axial length of the grinding compartment, said partition structure including in axially spaced proximate relation a grinding compartment wall having Ia central opening therethrough and ment wall having an annular coaxial opening therethrough, said drying compartment wall enibodying a central portion positioned in opposite air deect'ing relation to said inlet opening in opposite eiective shielding relation to said central opening and an outer annular material retaining portion spacedly surrounding said central portion, means between and including said walls operative when said drum is rotating to act on material entering the space between said walls and discharge same through said central opening, material showering elements positioned within said drying compartment, and means for introducing material to be dried and ground and a gaseous drying medium into said drying compartment through said inlet opening.

3. In a drying and grinding apparatus, the improvement comprising a drum having a coaxial inlet opening in an end wall thereof, means rotatably supporting said drum, a hollow partition structure disposed within said drum adjacent said end wall thereof and defining in coaxial longitudinally spaced relation a grinding compartment and a drying compartment having an axial length which is short relative to the diameter of the drum and relative to the axial length of the grinding compartment, said partition structure including in axially spaced proximate relation an annular grinding compartment wall and a drying compartment wall comprising in radially spaced relation an outer annular material retaining portion having an inner diameter considerably greater than the inner diameter of said grinding compartment wall and an inner central portion positioned in opposite air deilecting relation to said inlet opening and in opposite effective shielding relation to the central opening defined. by said grinding compartment wall, means-between and including said walls operative when said drum is rotating to act on material entering the space between said walls through said annular opening and discharge same through said central iopening, material showering elements positioned within said drying compartment, and means for introducing material to be dried and ground and a gaseous drying medium into said drying compartment through said inlet opening.

4. In a drying and grinding apparatus, the improvement comprising a drum having an axial inlet opening in an end wall thereof, means rotatably supporting said drum, a hollow partition structure disposed within said drum adjacent said end wall thereof and dening in coaxial longitudinally spaced relation a grinding compartment and a drying, compartment having an axial length which is short relative to the diameter of a drying 'compartv.'F' the drum and relative to the axial length of the grinding compartment. said partition structure including in axially spaced proximate relation a drying compartment wall embodying a central portion of nearly the same diameter as said inlet opening and positioned in'opposite air deflecting relation to said inlet opening and an outer annular material retaining portion spacedly surrounding and forming with said central portion an annular coaxial opening andan annular grinding compartment wall having an inner diameter considerably less than the inner diameter of said annular material retaining-portion and defining a central opening disposed oppoby said central portion, including said Walls operative when said drum is rotating to act'on material entering the space between said walls through said annular opening and discharge same through said'central opening, material liftl ing and showering elements positioned within the same size as said inner disposed opposite same, means between and in-v said drying compartment, and means for introducing material to be dried and ground and a gaseous drying medium into said .drying compartment through said inlet opening.

5. In a drying and grinding apparatus, the improvement comprising a drum having an axial inlet opening in an end wall thereof, means rotatably supporting said drum, `a hollow partition structure disposed within said drum adjacent said end wall thereof and dening in coaxial longitudinally spaced relation a grinding compartment and a drying compartment having an axial length which is short relative to the diameter ofthe drum and relative to the axial length of the grinding compartment, structure including in axially spaced proximate relation a drying compartment wall and a grinding compartment wall, said drying compartment wall embodying radially spaced inner and outer wall portions which extend nearly equal distances outward and inward from'the longitudinal axis and from the periphery of said drum, respectively, and said grinding compartment wall having a central opening therethrough of nearly Wall portion and cluding said walls operative rotating to act on material entering the space between said walls through said annular opening and discharge same through said central opening, material lifting and showering means when said drum is positioned within said drying compartment, and

means for introducing material to. be dried and ground and a gaseous drying medium into said drying compartment through said inlet opening. 6. In a drying and grinding apparatus, the improvement comprising a drum having end portions of reduced diameter rotatably supported on axially spaced bearings, one of said end portions having an inlet opening extending axially therethrough, a hollow partition structure disposed within said drum adjacent said one end portion and deiining in coaxial longitudinally spaced relation a grinding compartment and a drying compartment xhaving an axial length which 'is short relativel to the diameter of the drum and relative to the axial length of the grinding compartment, said partition structure including in axially spaced proximate relation a drying compartment wall embodying a central portion of nearly the same diameter as said inlet opening and disposed opposite same and an outer annular material retaining portion spacedly surrounding/and forming with said centralportion said partition "for introducing material an annular coaxial opening and a grinding compartment wall spaced from said drying compartment wall and having a central opening therethrough of nearly the same diameter as said centrai portion and disposed opposite same, means between and including said walls operative when said drum is rotating to act on material passing from said drying compartment through said annular opening and .into the space between said walls and discharge same through said central opening into the grinding compartment, circumferentially spaced radially extending lifting and showering eiements uniting *the outer annular spaced relation a'grinding compartment and a drying compartment having an axial length which is short relative to the diameter oi! the drumand relative to the axial length of the grinding compartment, said partition including a drying compartment wall embodying a coaxially disposed hollow cone-like member having a base of nearly the same diameter as said inlet opening and disposed opposite same and an outer annular material retaining portion spacedly surrounding and forming with the base of said cone member an annular coaxial opening and a grinding compartment wall having a central opening therethrough of nearly v the same diameter as the base of said cone member and toward which extendsthe apex thereof, spaced, radially extending lifting elements uniting the outer opposed wall portions of said partition structure, spaced radially extending lifting and showering elements uniting the annular portion of said drying compartment wall with lthe opposed end portion of said drum, and means for introducing material to be dried and ground and a gaseous drying medium into said drying compartment through said inlet O opening.

, RAY C. NleWVI-IOUSE.`

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