US2868462A

US2868462A - Pulverizing mill with novel outlet

Info

Publication number: US2868462A
Application number: US422107A
Authority: US
Inventors: Bogot Alexander; George E Gandsey
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1954-04-09
Filing date: 1954-04-09
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13
Also published as: FR1121823A

Description

Jam 13 1959 A. BOGOT ErAL. 2,868,462

PuLvERIzmc MILL WITH NovEL OUTLET Filed April 9, 1954 s sheets-set 1 Jan. -13, 1959I A. BoGoT'l-TAL j 2,368,462

PULVERIZING- MILL WITH NOVEL OUTLET' Filed-April 9, 19511 :5 sheets-snaai 2 l a INVENTORS j Alexander Bogot George E. Gondsey Fig. 2.. Bf 255g@ Jan- 13, 1959 A. BOGOT ET AL 2,868,462

l PULVERIZING MILL WITH NovELouTLET INVENTORS Alexander Bogo George E. Gandsey To NEY United States Patent O PULVERIZING MILL WITH NOVELOUTLET Alexander Bogot, Hastings-on-Hudson, N. Y., and George E. Gandsey, River Forrest, Ill., assignors to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Application April 9, 1954, Serial No. 422,107l s Claims. (Cl. 2415s) This invention relates to mills and particularly to pulverizing mills operated under pressure and having a plurality of outlet conduits each of which is to receive an equal distribution of the output of the mill with the loading of the pulverized medium in the transporting air passing through these conduits being uniform.

Bulverizing mills of the gas swept type Where the pulverized material is carried in a` gas carrier medium generally have cyclone classifiers which receive the ground material entrained in` a stream of gas directly from the grinding mechanism and are eifective to classify the material, returning that which is not sufficiently ground to the grinding mechanism for regrinding and convey the remainder together with the entraining air out through the outlet of the mill. `lt often happens, particularly in pulverizing systems for steam generators, that it is desirable to distribute the pulverized material substantially equally and uniformly through a plurality of conduits to predetermined points. Heretofore such pulverizing systems have been relatively cumbersome and have necessitated the use` of considerable equipment in addition to the mill to effect the proper distribution.

The present invention contemplates a pressurized mill of the gas swept type organized in a particular manner so that this substantially equaland uniform distribution is effected by the mill itself. To this end the mill is provided with a particular and unique mill outlet which is extremely compact and which has the several conduits through which the material is to be conveyed communieating directly therewith and connected directly thereto thereby reducing the cost as well as the bulkiness of the system and the required equipment.

It is a general object of this invention to provide an improved pressurized pulverizing mill having a `plurality of outlet conduits connected thereto and which substantially evenly and uniformly distributes the pulverized material to said conduits.

Additional objects and advantages will become apparentffrom the following description of illustrativeembodiments of the invention when read in conjunction with the accompanying drawings wherein:

`Figure 1 isa vertical cross section through a pressurized roller mill provided with a novel distributor outlet embodying one form ofthe invention;

Figure 2 is a horizontal cross section taken on line 2-2 of Fig. l, but to a larger scale;

Figure 3 is a vertical section of a modified form of distributor outlet;

Figure 4 is a horizontal bottom view of the embodiment of Fig, 3 taken from line 4-4 of Fig. 3.

The invention as herein disclosed is, by way of example, applied to a gas` swept pressurizedpulverizing mill of the type known as the bowl mill. By the. term pressurized mill" as used throughout this application is meant a mill wherein the carrier gas is introduced into and :forced through the mill under a pressure substantially above atmospheric asA contrasted toV a suction mill where a partial vacuum is created at the outlet of the mill thereby drawing the carrier gas into and through the mill at a subatmospheric pressure.

The mill of the present invention, generallyl designated 2,358,462 Patented Jan. 13, 1959 ICC 1 in the drawings, comprises a base 2 Within which is mounted a vertical shaft 3 supported in

bearings

4 and 5 and having secured adjacent its lower end worm wheel 6 which engages worm '7 mounted on motor driven shaft 8. `Rotation of shaft 8 accordingly rotates bowl 9 which is mounted on the upper end of shaft 3 and is equipped with a grinding ring 10 made of wear resistant material.

Mounted on base 2 is superimposed cylindrical housing 11, the top of which is capped by a cover 12. An opening 13 in housing 11 admits gas (preferably air) .under pressure into the mill. Mounted within housing .11 is a bearing 14 supporting a trunnion shaft 15 about which roller assembly R may oscillate. There may be one or more roller assemblies R depending upon the size of the mill with but one of three such assemblies that make up the organization of Fig. l being shown in this figure. Each assembly R includes a roller 16 rotatably supported on roller shaft 17 which in turn is mounted on trunnion shaft 15 by member 18. An arm 19 projects from member 18 against which a spring 20 bears to urge the arm and thereby the roller 16 toward the grinding ring 10.

As the bowl rotates, the material on the bowl iiows radially onto the grinding ring 10 and is crushed thereon by the rollers 16. A chute 21 is fastened to housingxll and extends from a material feeder, not shown, into the mill to deliver raw unground material onto thecentral portion of the bowl9.

Air is delivered into the housing `11 through opening 113 by a fan, not shown, with this air flowing upwardly through the `annular opening 22 around the periphery of the bowl 9 lwhere it meets the ground material being `delivered over the edge of the bowl and carries it `up` wardly and inwardly of the mill. Some of the relatively coarse material falls back into the bowl 9 to be further ground while the remaining material is entrained by the air flowing upwardly through the mill and enters the classifier 23 disposed in the upper portion of the mill housing.

' vThe classiiier 23 contains a multiplicity of openings 24 adjacent housing cover 12 (Figs, `1 and 2) with each opening being provided with a vane 25' adjustably about a vertical axis 26. The material and air mixture rising through the mill enters the clasisfer 23 through the openings 24 and is deflected by the vanes 25 so as to whirl through the classifier. Within the `classifier 23 the material that has not been ground to a `desired degree of `iineness is separated by means of centrifugal action from the remainder of the material and reconveyed to bowl 9 through passage 28 while the remainder of the material together with the entraining air pass upwardly through outlet passage 27 formed in the center of the classifier.

Heretofore this outlet passage was in the form of an unobstructed conduit or the like which resulted in the whirling material flowing therethrough in a series of ribbons which hug the wall of the passage. When the material was to be distributed to a plurality of con-duits, such as fuel supply conduits for a steam generator, it was thus necessary to add special equipment (such as the` known venturi throat and riifie distributor combination) on top of the mill to receive the material from the outlet passage and distribute it substantially equally and with auniforrn loading to the several conduits all of which considerably increased the `head room require ment above the mill as well as the cost of the installation and the draft loss therethrough.

To overcome these objections, the mill outlet of the present invention is itself constructed in a novel manner to assure that the mixture of material and air received `by the several conduits is substantially ofthe same loading and substantially equal distribution ,is obtained.

frnaterial toward the center of the outlet passage.

In the embodiment of Fig. 1 outlet passage 27 communicates directly with four outlet or distribution conduits 29, symmetrically arranged relative to the cross section of the outlet passage and secured to the upper end .0f said outlet passage in any suitable manner. The passage 27 is of circular transverse section and forms a converging-diverging throat having an upwardly and inwardly directed surface 30 terminating `at cylindrical portion 31 from which extends the upwardly and outwardly directed surface 34 with this throat tending to direct the Extending radially inward. from surface 30 are vanes 32, equally spaced circumferentially of passage 27 and being effective to break the spin of the entraining air and the spiralling ribbons of material entering the outlet passage from classifier 23 thereby producing a parallel linear flow through throat 31. Inertia of the material particles tends to keep them moving in a straight line toward outlet conduits 29. With this mill outlet organization it is found that the spin of the material is broken and the material is re-entrained and redistributed in the carrier yair stream in such a manner that each of the outlet conduits receives a uniform loading of material in the entrainln the modified embodiment of Figs. 3 and 4 the outlet of passage of mill 1, generally designated 27a in these figures, includes depending cylindrical wall 33 within ing air and substantially an equal portion of the malterial.

which is symmetrically arranged the lower ends of Outl `let conduits 29a with the lower ends of these conduits extending downward to substantially the lower edge of the wall 33 and being chamfered at an angle sloping upwardly toward the center of the passage as shown. This arrangement in effect forms an inward sloping wall corresponding to the constricting slope of passage 27 of the Figs. 1 and 2 embodiment and is effective to direct the material flowing through passage 27a toward the center of this passage. Extendingl downwardly from cover `12a to a point upstream of the lowermost ends of conduits 29a are equally spaced radial vanes 32a with these vanes being placed between conduits 29a and diametrically across the openings of the conduits as shown in Figs. 3 and 4, these vanes acting to break up the spin of the entraining air and spiralling ribbons of material entering the outlet 27a from the classifier 23 to produce a substantially parallel linear 110W into the outlet conduits 29a. This modified organization, as in the case of the embodiment of Figs. 1 and 2, is thus effective to break up the spin of the material and air and re-entrain and redistribute the material in the carrier in a manner which has been found to substantially equally and uniformly distribute the material to the several outlet conduits 29a.

While preferred embodiments of the invention have been shown and described, itis to be understood that such showing is merely illustrative and not restrictive land that variations and modifications may be made therein without departing from the spirit and scope of the invention.

We claim:

1. A gas swept pulverizing mill comprising an upright housing having an outlet adjacent its upper end, said housing having a gas carrier medium passed upwardly therethrough toward said outlet, means in said housing below said outlet to receive and pulverize material, the pulverized material becoming entrained in said upwardly passing gas, a cyclone classifier in the upper portion of said housing coaxial with said outlet and operative to receive the gas and material mixture and classify the pulverized material with the sufficiently fine material and entraining gas passing upwardly through the central portion of the classifier and through the mill outlet, said outlet having a plurality of symmetrically arranged outlet conduits leading directly therefrom, the walls of the outlet converging inwardly and diverging outwardly in the direction of ow through the outlet and a plurality of radial equally spaced vanes disposed in said outlet.

CII

said means and toward one'end of the housing, said carrier gas picking up pulverized material during its passage of said means, a cyclone classifier disposed in said one end of the housing and operative to receive the mixture of gas and material and separate the coarse material from the sufficiently fine material, the outlet of the mill being coaxial of said classifier and disposed to receive said sufficiently fine material and the carrier gas from the classifier, said outlet being of circular transverse section and having convergining-diverging wall portions serially arranged with respect to the flow therethrough, a plurality of equally spaced radial vanes extending inwardly from the converging wall portion, and a plurality of outlet conduits communicating directly with the mill outlet and symmetrically arranged about the axis of said outlet.

3. A gas swept pulverizing mill comprising a hous- Ving having means for receiving and pulverizing material and having a stream of carrier gas passed therethrough past said means and toward one end of the housing, said section and having a plurality of outlet conduits symmetrically arranged with ,respect to the axis of the outlet and extending into the outlet, the inner ends of said conduits being chamfered inwardly toward the center of the outlet, and -a plurality of radial equally spaced'directing vanes in said outlet upstream of the inner ends of said conduits.

4. A gas swept pulverizing mill comprising a housing having means for receiving and pulverizing material and having a stream of carrier gas passed therethrough past said means and toward one end of the housing, said carrier gas picking up pulverized material during its passage of said means, a cyclone classifier disposed in said one end of the housing and operative to receive the mixture of gas and material and separate the coarse material from the suficientlyfine material, the outlet of the millbeing coaxial of said classifier and disposed to receive said sufficiently fine material and the carrier gas from the classifier, said outlet comprising a coaxial circular member, a plurality of outlet conduits symmetrically arranged with respect to the axis of the outlet and having their inner end extending into the outlet within said circular member to a point adjacent a plane containing the inner edge of said circular member, the inner ends of said conduits v arranged so that each of the conduits has a vane extending diametrically across its inlet end.

kReferences Cited in the file of this patent UNITED STATES PATENTS 398,788 Mundy Feb. 26, 1889 970,530 Miller Sept..20, 1910 1,541,337 Feix June 9,1925 1,766,237 Whitmore June 24, 1930 1,814,395 `Lykken July 14, 1931 2,092,310 Hardgrove Sept. 7, 1937 2,100,734 Crites Nov. 30, 1937 2,237,021 Wood Apr. 1, 1941 `2,698,142 Crites Dec. 28, 1954 FOREIGN PATENTS 644,696 Germany May 11, r19317