US2916217A

US2916217A - Pressurized pneumatic mechanical unit pulverizer

Info

Publication number: US2916217A
Application number: US481347A
Authority: US
Inventors: John I Yellott
Original assignee: Bituminous Coal Research Inc
Current assignee: Bituminous Coal Research Inc
Priority date: 1955-01-12
Filing date: 1955-01-12
Publication date: 1959-12-08
Anticipated expiration: 1976-12-08

Description

J. l. YELLOTT Dec. 8, 19-59 PRESSURIZED PNEUMATIC MECHANICAL UNIT PULVERIZER Filed Jan. l2, 1955 M @9% ATTYORNEYo N@ WJDL mm am l .vin

-PRESSURIZED PNEUMATIC MECHANICAL UNIT PULVERIZER `Iohn I. Yellott, New York, N.Y., assignor to Bituminous Coal Research, Inc., Washington, D.C., a corporation of Delaware Application January 12, 1955, Serial No. 481,347

5 Claims. (Cl. 241-101) This invention relates to pneumatic-mechanical unit pulverizers adapted for mechanical and/or pneumatic drive, as desired, as well as for either co-current or counter-current peripheral delivery of pressurized pneumatic fluid-borne streaming entrainments of particulate material radially inward against impact blading comprised of interleaved, concentric annular rows of stator .and rotor-mounted blades.

The invention relates further to pulverizing systems incorporating the novel pneumatic-mechanical unit pulverizer, such as coal-feeding units of coal-burning gas turbine power plants, wherein crushed coal is delivered to a pressurized combustor in a pressurized combustive air stream, and is pulverized and fluidized in the air stream by passage through a convergent nozzle embodied in the combustive air line immediately in advance of a combustor. Other pulverizing systems susceptible of economical improvement by the incorporation of the novel unit pulverizer herein, include the ultra-fine grinding and uidizing, as well as pneumatic classification of Vgrindable minerals. A particularly important use of the novel unit pulverizer herein is in the field of ultra fine grinding of air-floatable materials,such as talc, to produce a product suitable for cosmetic use.

The novel penumatic-mechanical unit pulverizer herein is a companion form to the unit pulverizer disclosed and claimed in my application, Serial No. 481,346, tiled January 12, 1955, for Pneumatic-Mechanical Unit Pulverizer (I), now PatentNo. 2,839,253, issued June 17, 1958, the use of this last said unit pulverizer in the coal-feeding system of pressurized combustors of coal-burning gas turbine power plants, being disclosed and claimed in my pending application Serial No. 423,978, tiled February 23, 1954, for Powdered Coal-Burning Gas Turbine Power Plant With Pneumatic Coal Conveying System Therefor.

VThe unit pulverizer herein is essentially characterized,

:inter alia, by the use of a peripheral convergent nozzle entrant, with -an axial discharge, while my said companion unit pulverizer incorporates an axial convergent nozzle entrant in one face, and an essentially axial discharge in the other face.

The novel unit pulverizer herein is characterized by a rotor disk mounted for rotation in a sealed, pressuresustaining, pill-box type housing, the disk and the housing mounting interleaved concentric, annular rows of impact members; a convergent nozzle pulverizer entrant in the periphery of the housing and in alignment with and discharging against the sequential peripheral impact members of the rotor; a shaft mounting the rotor, and an axial discharge in the face of the housing opposite the shaft. The shaft is normally coupled to the turbine shaft, through reduction gearing, or any other suitable coupling means, to rotate therewith, and under any suitable speed ratio. A special feature of this invention is the incorporation in the gearing mechanism of means for reversing (counter-rotating) the rotor shaft, or declutching it when the rotor is to be pneumatically driven. As a corollary `to both the pneumatic drive and the counter-rotation of IUnited States Patent O the rotor, the invention comprehends the use of a second, duplicate convergent nozzle entrant which is used4 tointroduce a secondary stream of clean, pressurized air, which, as will appear more fully hereinafter, can be delivered at a pressure above that of the incoming solidsbearing stream, and as a purging stream and/or a rotor driving stream, as may be required.

When used in a combustion system of the character described, the pressurized combustive or primary air circuit can be cooled, and the combustive air delivered to the combustor at a pressure which, desirably, Will exceed the secondary air pressure in the combustor by not over 20 p.s.i. In such combustion systems, when used in locomotives, Where space limitations are critically restrictive, the unit pulverizer must function as a once-through device, because, obviously, there is no room available for the equipment required for classifying, separating and recycling oversize particles to thecombustive air line and the unit pulverizer. Space limitations in stationary power plants are not so restrictive, and unit pulverizers can be adapted to function with recycling, or` pulverizer trains, where two or more pulverizers, in series, can be used. The unit pulverizer of the present invention permits a once-through passage of material to be ground,with any desired degree of ne grinding, and with a minimal dwell or residence time in the unit pulverizer. `With a combustive air feed of c.f.m. through a 2-'inch feed line having a 1inch convergent nozzle entrant into a unit pulverizer casing 24 inches in diameter, and 6 inches deep, the inwardly spiraling traverse of the solids-bearing air-stream will require about 0.65 second. This relatively small time period is substantially equivalent to instantaneous grinding. l

With the device of the present invention incorporated in a precooled combustive air feed line, superheating of the combustive, primary air stream to a temperature above the threshold ignition temperature of the entrained fuel particles is avoided. Additionally, by utilizing the centrifugal effect of the improved pneumatic-mechanical unit pulverizer of the present invention for effecting the reductionof the fuel particles to a desired particle size, the carrier stream of combustive air is no longer required to be maintained at the high pressure necessary to insure adequate impacting of entrained solids against impact surfaces of non-rotating or fixed impact surfaces, as used hitherto. When the rotor of the unit pulverizer is counter-rotated with respect to the'linear direction of travel of the incoming solids-bearing air stream, the impact to which each particle is subjected is the resultant of the air speed of the particle, plus the tip speed of the peripheral row of counter-rotating rotor blades. The expenditure of the extra power required for effecting counter-rotation may be justified when the type of material being ground, or the exigencies of the situation require.

In gas turbine power plants the improvements of the present invention have been found to give optimum results When the rate of flow or feed of the primary airborne fuel to the combustor is directly controlled as a function of the load on the turbine in response to the controller, as in a locomotive or marine installation, as well-as in stationary power plants. In such plants the fluidizing air for the pneumatic coal-feeding system can be supplied independently, or taken as a small side stream of about 4% of the cooled combustive air stream (140 R). Where pulsators are used with the uidizing equipment, pressure air can be supplied from the combustive air source. l

The air supply for the unit pulverizer herein, when used in pure grinding or pulverizing installations, as opposed to combustion apparatus, may be derived from any suitable source, and may comprise a single supply, with differential pressures for one or more side streams being effected by the use of reduction valves. When the rotor is to be pneumatically driven, the driving air may be at top pressure, and the combustive air, pulsating air, and fluidizing air, taken off that supply line at decreasing pressure levels,.as required. A single piping system for primary air may be suitably valved with reducing valves, and eachsaid valve by-passed by a valved line, whereby any combination of air supplies can be obtained in a single unit pulverizer installation of the type described herein. y

It is, therefore, among the features kof novelty and advantage of the present invention to provide a novel, pneumatic-mechanical unit pulverizer.

It is a further feature of novelty and advantage of this invention to provide a pill-box type, hermetic cased pneumatic-mechanical unit pulverizer incorporating at least one peripherally disposed convergent nozzle entrant and a substantially axial discharge outlet.

Yet another feature of novelty and advantageV of this invention is the provision of a hermetic, pi'l-box 'type pneumatic-mechanical unit pulverizer embodied in a pressurized conveying air line, characterized by the fact that the entrant of the line into the periphery of the pulverizer is not over one-half of the diameter of the line, and its axial discharge is substantially the same diameter as the line.

An-additional feature of novelty and advantage of the present invention is a unit pulverizer of the pill-box casing type embodying a rotor mounted for rotation on a shaft, the pulverizer casing and the rotor respectively mounting intermeshing, concentric annular rows of irnpact members, a peripheral entrant adapted to direct a pressurized solids-bearing air stream against the peripheral row of. impact members on the rotor, and an axial discharge opening in the casing.

Another feature of novelty and advantage of this invention is the provision of pill-box type, hermetic, pneumatic-mechanical unit pulverizer embodying impactbladed rotors having at least an annular row of peripheral blades, a convergent nozzle entrant in the wall of the pulverizer axially discharging against said peripheral blades, and an axial discharge in a cover of the pulverizer.

A further feature of novelty and advantage of this invention is the provision of hermetic, pill-box type pneumatic-mechanical unit pulverizers embodying bladed rotors having at least one peripheral annular row of impact blades, a convergent nozzle entrant in a cover of the pulverizer axially discharging against said peripheral blades, and an axial discharge in the same cover of the pulverizer.

It is also a feature of novelty and advantage of this invention to provide a hermetic, pill-box type pneumaticmechanical unit pulverizer embodying a bladed rotor having at least one peripheral annular row of impact blades, a convergent nozzle entrant in a cover of the pulverizer axially discharging against said peripheral blades, and an axial discharge in the opposite cover of the pulverizer.

It is a special feature of novelty and advantage of this rotor having at least one peripheral annular row of impact blades, a pair of peripheral convergent nozzle entrants in the pulverizer, and an axial outlet in a cover of the pulverizer. K

Other features of novelty and advantage of this invention include novel pneumatic-mechanical unit pulverizers of the pill-boxtype with multiple peripheral entrants and a single axial outlet, together with separate air supplies for said entrants, at least one of the entrants receiving and discharging air-borne particulate solids into the pulverizer.

Additional features of novelty andY advantage of this invention include the incorporation of the novel pneumatic-mechanical unit pulverizers in the pressurized combustive "air feed lines of combustors of motive iluid generators of coal-burning gas turbine power plants; the

use of constant volume air supply in the feed line; the use of pressure air for pulsating and fluidizing the crushed coal supply; gravity feed of coal into a rotary coal pump having its discharge embodied in the combustive air feed line; the use of a single source of cooled pressurized air, with suitable pressure regulating devices, for supplying primary and auxiliary air `to the power plant and its coalfeeding system; and means for optionally converting a unit pulverizer from power drive to pneumatic drive, as well as to effect counter-rotation of the driven rotor with respect to the direction of ow of the inowing solidsladen air stream.

With these and other objects in view, which may be incident to my improvements, the invention consists in the parts and combinations to be hereinafter set forth and claimed, with the understanding that the several necessary elements, comprising my invention, may be varied in construction, proportions and arrangement, without departing from the spirit and scope of the appended claims.

In order to make my invention more clearly understood, I have shown in the accompanying drawings means for carrying the same into practical effect, without limiting the improvements in their useful applications to the particular constructions, which for the purpose of explanation, have been made the subject of illustration.

In the drawings, like numerals refer to similar parts throughout the several views, of which Figure l is a schematic showing of a novel pneumaticmechanical unit pulverizer and auxiliary equipment as embodied in the pneumatic coal delivery system of a i'luidized coal-burning gas turbine power plant;

Fig. 2 is a vertical section through the axis of the unit pulverizer of Fig. l, and taken on line 2-2 of Fig. 3;

Fig. 3 is a section taken on line 3--3 of Fig. l, showing duplex entrants and concentric alternate rows of rotor and stator impact blades;

Fig. 4 is a detail showing of a peripheral entrant on the discharge cover, and

Figs. 5 and 6 are detail showings of peripheral entrants in the wall of the pulverizer casing, and the rear cover, respectively, the rear face of the rotor mounting a single peripheral annular row of impact blades, and the rear cover of the pulverizer being olfset to receive the row of blades.

Turning now to the drawings, there is shown in Fig. l, diagrammatically, a uidized coal-burning gas turbine power plant, as adapted for use in locomotives having either mechanical or electric drive. The power elements of the kplant comprise a gas turbine 1i) having a motive gas intake or pressure inlet 11, and an exhaust stack 12. The shaft 13 of the turbine is suitably coupled to and drives the shaft 14 of main, secondary air compressor 15. The compressor has an air entrant 16, a main secondary air discharge duct 17, and a side stream take-off 18, discharging through a short pipe or tubulature 19.

A main D C. generator 20 and an auxiliary D.C. generator 21 are mounted on shaft 22, which is coupled to turbine-compressor shaft 13-14, by any suitable means such as coupling 23. A gear casing 24, encasing a gear train, not shown, is provided with an input coupling member, designated generally by the numeral 25, which member is suitably secured to shaft 22, and driven thereby and therewith. A gear control housing 26 is secured on casing 24, and is provided with an actuating member 27, which is connected to the power plant control station through any suitable means, not shown. The output member of the gear train is designated generally by the numeralZS, and is coupled to a driving shaft 29, of the pneumatic-mechanical unit pulverizer 100, whose construction, assembly, function and mode of operation will be described more in detail hereinafter.

The secondary air duct 17k discharges into the burner end of combustor casing 30. The combustor casing is a generally J-shaped structure, the long leg of -which comprises an input and llame tube-mounting section 31, and

a downstream secondarycombustion and mixing cham,- ber 32, terminating in a U-turn or return bend 33, which discharges into the input side of ash separator casing 34, whose cleaned gas outlet 35 is embouched in the intake of gas turbine 10. i

The ash separator casing 34, mounts a plurality of depending pressure-sustaining reverse ilow vortical whirl separators, designated generally by the numeral 36, each separator incorporating a separated solids blowdown line 37, jointly embouched in a common separated solids discharge manifold 38, from which the solids-containing blowdown stream is led to an ash concentration and separator, not shown. The details of the ash separator as sembly are more particularly disclosed and claimed in the application of John I. Yellott and Peter R. Broadley, Serial No. 330,077, filed January 7, 1953, for Coal Burning Gas-Turbine Power Plant Incorporating Novel Self-Supporting Pressure-Sustaining Vortical Whirl Separators Together With Improved Ash Quenching and Blowdown Means, and will not be described further herein, as no invention in the present case is predicated upon the details of such assembly.

The combustor casing 30 is provided with a fluted radiator shield 40 which extends the fully length of the long leg'of the casing, in slip t therein, and provides continuous paths ,for the delivery of coolant air from secondary air duct 17 to cool the inside of the combustor casing. The U-turn 33 is provided with a conformed radiation shield 41, shown in dotted lines, which telescopes in the downstream end of radiation shield 40. The curviform tubular shield 41 is provided with louvre openings 42 through which the coolant air'from the annular space between the radiation shield andthe combustor casing is directed into the Ainterior of the U-turn 33.

A llame tube or cold wall combustion chamber 43 is mounted in the upstream end of the casing 30, in slip iit engagement with the inner fluted surface of the radiation shield 41, and is provided with secondary air from duct17.l The combustor unit 43 is of the general type shown and claimed in the companion appli-cations of F. D. Buckley, Serial No. 257,165, filed Nov. 19, 1951, for Cold Wall Combustor With Flexibly Mounted Flame Tube, now Patent No. 2,823,627, issued February 18, 1958, and Paul Rotzler, Serial No. 257,079, iiled Nov. 19, 1951, for Powdered Coal Burner for Pressurized Combustors, now Patent No. 2,858,779, issued March 4, 1958, and will not be described further herein. A burner 44 is 'spacedly received in the domed `head 45 of the ame tube and discharges a combustible streaming entrainment of uidized, pulverulent coal particles in combustive air into the flame tube where it is burned. Secondary air is fed into the llame tube through lthe burner dome and annular openingsalong its length, supplying oxygen for completing thecombustion of the gaseous products of combustion, and the initial chilling and quenching of molten combustion residues; The diluted gaseous products of combustion and suspended and entrained incandescent solid combustion residues are rectilinearly projected against the upper portion of the U-shaped segment 41 ,of the uted radiator shield.40,"and is impinged against .ipulverulent coal are carefully described in the applications hereinabove referred to, and will not be considered further, saveto note that as much as 50-60% of the pulverized fuel may be incompletely burned during the exceedingly short dwell in the combustion zones, and must be quenched before introduction into the ash separator assembly inorder to prevent destruction by after-burning in the super-oxygenated ambient motive uid (ca. 1300 F.). The use of a continuously advancing coolant air sheath, coowing with the core stream of superheated combustion gases, serves to keep the surfaces-of the exposed equipment relatively clean by sweeping ash and other combustion residues out of the way before they have a chance to deposit and build up, plugging the air and gas passages, and destroying metallic surfaces by accelerated after-combustion."

Coal-feeding system The coal-feeding system of a -gas turbine power plant,

of the type illustrated and described herein, incorporates a novel pneumatic-mechanical unit pulverizer in the combustive air feed line to the combustor. For the purpose of more clearly setting out the structure and function of such novel unit pulverizer, the coal-feeding system, of which it is the last or ultimate functional element, will be described first.

The uidized coal supply herein, so diagrammatically shown in Fig. 1, is more particularly described and claimed in my pending application, Serial No. 423,978, filed Feb. 23, 1954, for Powdered Coal-Burning Gas Turbine Power Plant With Coal Conveying System Therefor, and will be described herein only insofar as its assembly and function are necessary for an understanding of the function and operation ofthe unit pulverizer herein.

Turning now to Fig. l, the coal supply will be seen to comprise a vented tank or bunker S0, having side walls 51, a vented top 52, and a bottom 53. A filler opening or manhole 54 is provided in the top, and a discharge spout 55 is provided at the bottom of a wall and integral with the bunker 50. The bottom of the bunker may be formed with sloping sides and at such an angle as to discharge freely into the discharge spout 55. Combination air-permeable, iluidizing and pulsating mattresses, designated generally by the numeral 56, are disposed in and across the bottom of the bunker, and conformed thereto, as disclosed' and claimed in my said application Serial No. 423,978, supra, and in my application Serial No. 411,930, filed v February 23, 1954, for Improved Pneumatic Material Handling System and' Apparatus, now Patent No. 2,805,896, issued September 10, 1957. A chargeof coal 57, is disposed in the bunker, and the preferred particle size is less than 3/s in., and is uidized by low pressure uidizing air introduced into the iiuidizing aerators or mattresses 56 through fluidizing air supply line 58. High-pressure pulsating air is introduced into the pulsators 56', embodiedin the aerators, through pulsator air supply line 59. Supply lines 58, 59 are shown aS embodied in the bottom of the bunker, but it is to be understood thatthey may be'separate units, detachably in; troduced through the top of the bunker, all as disclosed and claimed in my said applications Serial No. 411,930, supra.

The iuidized coal from the bunker is adapted to be discharged, in free gravity ilow, from` the chute or spout 55, into the entrant 61, of a rotary coal pump 60, mounting a close-clearance feeder wheel, not shown, and driven at any suitable speed, or at a uniform speed, as desired. In the system illustrated, the pump is driven atI constant speed, and the coal feed rate is varied byy controlling the discharge of coal from the bunker. Control means for this purpose may comprise a gate valve fitted in the spout and mounted for reciprocation therein on piston rod 67 of piston 67' slidably mounted in cylindrical casing 64, and the member 65 being normally springbiased into closed position by biasing spring 68 in the casing. A compressed air linev 68 is coupled to casing 6-4, andintroduces pressure air under the piston 67', to overcome the bias of spring` 68, and lift the valve 67, thereby opening the spout 5S to permit any desired amount andrate of discharge of coal therethrough. A control throttle 69 i'stinterlposedinithe air line 68', which 7 is also coupled to a speed-responsive device 10', controlled by andresponsive to the rotation of the turbine shaft. This demand-control feature of the coal feed to the combustor is disclosed and claimed in my application, Serial No. 423,978, supra.

Pressure air supply A novel feature of the present invention is the provision and use of special pressurized combustive or primary air and auxiliary air supply means. Again turning to Fig. 1, the pressure Vair supply is made up as follows: A side-stream of compressed air is discharged from the discharge side of secondary air compressor 15 through pipe 19, intercooler 70 and pipe 71, into the intake 72 of booster compressor 73, desirably driven at constant speed by D C. motor 74, which may be powered by auxiliary D.C. generator 21, through suitable leads, not shown. The outlet 75 of the compressor 73 is connected through tubulature 76 and T-connection 77, with

lines

78 and 79, respectively, supplying constant volume, cooled pressurized air to the coal feed side and the purge air side of unit pulverizer 100, as will appear more fully hereinafter. The line 78 supplies constant volume cooled pressurized air to the coal feeding and uidizing system in the following manner: T 80 is coupled, at line pressure, through tubulature 81, to pulsator 59. The terminal end of line 78 is coupled to fluidizing air inlet line 58, through reducing valve 82. The uidizing air will be maintained at the lowest pressure consonant with the degree of uidization necessary for the particular material being handled. This feature is of importance when the system herein is used for treatment of other grindable materials than coal, and the turbine power plant is not incorporated in the system.

The second T 83, is connected to the discharge side of pump 60 through line 84, embodying valve 85. For purposes to be described more in detail hereinafter, the valve 85 may be by-passed by line 86, embodying reducing valve 87, and unions 86. A second valved by-pass line 88- may be connected to line 78, just downstream of T 77, and a valve 89 may be fitted in line 78, in and between the couplings of by-pass 88. The by-passing of line 78, in the manner indicated, permits the maximum flexibility in the operation of the system herein, and particularly in the optimum utilization of the novel unit pulverizer 100.

The rotary coal pump 60 may be of the types disclosed and claimed in my application, Serial No. 361,802, led June 15, 1953, now Patent No. 2,750,234, issued June 12, 1956, as a division of Patenty No. 2,675,676 f April 20, 1954, (filed Nov- 17, 1950), or in my application` Serial No. 363,524, filed June 23, 1953, now Patent No. 2,750,233, issued June 12, 1956, as a division of Patent No. 2,652,687 0f Sept. 22, 1953, (led Nov. 30, 1949). The discharge side of the pump has aligned inlet and outlet openings, not shown, in the walls of the pump casing,

severally coupled to pressure air inlet pipe 84, and pressurized combustive air feed line 90. The feed line is of uniform diameter throughout, and, as shown in Fig. 3, its terminal end embodies a ow restriction comprising a lconvergent wall section 91 merging into a throat section 92, and a discharge section 93, usually of the same diameter as the throat section. The diameter of line 90 is at least double that of the throat 92. The discharge section 93 of feed line 90 is peripherally embouched in novel pneumatic-mechanical unit pulverizer 100, of generally flat, pill-box shape.

Unit pulverizer structure and operation The novel pneumatic-mechanical unit pulverizer 100 is shown in combination with the combustor of a gas turbine power plant using uidized coal as the primary fuel. The unit pulverizer of Fig. 1, is shown in section, in'Figs. 2 and 3, `and modied peripheral entrants are 8 shown in each of Figs. 4, 5, and 6, and unit pulverizers incorporating these modifications are respectively designated a, 100b,A and 100e, to distinguish them more readily from the prototype unit pulverizer 100, and from each other.

Unit pulverizer 100, as noted, is a generally fiat, pillbox or cheese-box type structure comprised of concentric front and back disk shaped covers 101, 102, of the same diameter, and an interposed, `doubly flanged, annular body member 103. The body member 103 is concentric with the covers, and the

peripheral flanges

104, 105, thereof are in register with the peripheries of

covers

101 and 102, respectively. The covers are hermetically secured in place on and over the cylindrical body section, in any suitable manner, as by bolts 106, suitable annular metallic gaskets 107, or equivalent pressure-responsive. sealing members, being disposed in and between the covers and the anges. The cover 101 is provided with an axial tubular discharge outlet 108, which, as shown, forms a downstream continuation of burner feed line 44, supra. Usually, the tube 108 and feed pipe 44, will be detachably coupled, to facilitate emplacement and replacement of the unit pulverizer. Pressure feed pipe 90 and discharge outlet pipe 108 will normally have the same internal diameter, for a purpose to be described more in detail hereinafter. The inside of cover 101, as shown, mounts an integral annular row of concentric impact members 109.

The rear cover 102 is of thicker wall section than the front cover, and embodies an integral, rearwardly extending boss 110, which is axially apertured at 111 to receive and journal drive shaft 112 of disk rotor 113 which is mounted for rotation in the chamber formed in the member 100. The disk 113 has close peripheral clearance with the inner surface of body section 103 of the casing, defining an annular gap 114 therewith, the width of which gap should be less than the average particle size of the feed. The front surface of disk rotor 113 mounts a plurality of concentric annular rows of impact members 115, the annular row of fixed impact members 109 being received in and between the annular rows of impact members on the rotor. The impact members mayv be of any suitable shape, a bladed form being preferred in the unit pulverizers of the present invention. The fixed blades 109 are longer than the rotor blades 115, and extend from the inner surface of cover 101 almost to the bladed surface of disk 113. The disk 113 has an axial boss 116 which extends to the discharge opening of the pulverizer casing and mounts a spider 117 on which are secured radial'rejector blades 118. The blades 118 are concentric with the discharge opening and extend radially inward thereof, whereby they serve to return oversize particles back into the grinding chamber, and thereby function as a classifier.

The shaft 112 is journaled in shaft housing 110, and

labyrinth packings

120, 121, with interposed spacings and bearing member 122, are fitted on and over the shaft, and tightened in place by lock nut 123, screwed up on the threaded outer end 124 of rotor shaft 112. The threaded end 124 of the rotor shaft is coupled to the driving or output member 29 of gear system 24, whereby the rotor is driven by the turbo-compressor shaft 22. The purge air line 79 is tapped into bearing member 122, as will be described more in detail hereinafter.

A special feature of the unit pulverizer of the present invention is the peripheral mounting of a convergent nozzle entrant 93 in the pulverizer casing in such a manner as to cause a pressurized stream issuing from the nozzle to impinge against the successive central face portions of suitably oriented impact blades of the peripheral annular array of blades'on rotor 113 as they are presented to the entrant. Desirably, the nozzle will be mounted at an acute angle to a tangent to the periphery of the outer row of rotor blades. As shown in Fig. 3, the tip end 94 of discharge nozzle 93 is conformed to the inner surface of the mounting member. The entrants, as noted, may be mounted in the wall of the casing, as shown in Figs. 1, 2, 3, and 5, or in either cover, as shown in Figs. 4 and 6.

Turning again to the showings of Figs. 1, 2, and 3, the mounting of an entrant in the left-hand or grinding chamber section of the casing, is shown. In this form of the invention the wall section 103 is formed with an angularly apertured boss or bosses 10311, which receive the entrant and permit the incoming pressurized airborne material to be ground to be discharged directly into the bladed grinding chamber. In this form of the invention, as in the form shown in Fig. 4, the peripheral row of rotor blades serves to effect initial impact on incoming particles, as well as subsequent pulverization.

In the form shown in Fig. 4, the front cover 101, is formed with an angularly apertured entrant-receiving boss 101a, while the body portion 103 is not apertured. In this form, as in that of Figs. 1-3, only one face of the rotor disk is bladed, and the rear cover is flat.

Among the special features of the invention is the provision of a separate input chamber in which a single peripheral row of impact blades is received, this row of blades being mounted on the rear surface of the disk rotor, and the rear cover of the pulverizer being conformed to the annular row of blades. In these forms, the gap 114, between the periphery of the disk rotor and the casing wall serves to prevent passage of oversize particles into the main fine grinding or pulverizing chamber, thereby serving as a classifier. Additionally, the purge air forced inwardly into the rear chamber of the pulverizers aids in sweeping out preliminarily ground particles from the first, coarse grinding chamber, into the second, pulverizing and iluidizing chamber.

Turning now to Fig. 5, the unit pulverizer 100b, is `comprised of the usual front cover 101, and a double width cylindrical body section 103a, having an entrantreceiving boss 103b, at the rear flange thereof. The disk rotor 113a is provided with a peripheral annular row of impact blades'115a, on the rear face thereof, and adapted to be impacted by a solids-bearing input stream from the entrant. The rear cover is provided with a peripheral offset or flanged outer portion 102a, forming an annular input or coarse lgrinding chamber with the rear face of the disk rotor and the wall of the pulverizer.

In Fig. 6, the double width cylindrical body portion 103C is unapertured, and flange 102a of the rear cover is provided with an angularly apertured boss 102b, receiving the usual entrant 93 of the feed line.

In the ordinary use of the forms of the unit pulverizer described hereinabove, a constant volume, pressurized combustive air stream picks up iluidized coal in pump 60 and transports it, as a streaming entrainment of discrete particles, through combustive air feed line 90 and into burner 44 of combustor 40, through pneumaticmechanical unit pulverizer 100. Because of the flammability of pulverized coal in pressurized, heated air, pressurized pneumatic transport of pulverulent fuel is most dangerous If the temperature of the conveying air is maintained below the danger point, and the velocity of the conveying air is maintained above llame velocity, danger of flashback in the fuel line is eliminated. The unit pulverizers herein permit the handling of crushed coal, in uidized form, and at relatively low, and therefore, economical air pressures, and the pulverization and uidization of the coal immediately before delivery into a burner, thereby avoiding flashback, and excessive power costs.

The above recited desiderata are attained by passing a uidized coal-bearing (equal to or less than Vs in. particle size), cooled, constant volume, moderate pressure air stream through a pneumatic-mechanical unit pulverizer, wherein it is subjected to an initial accelerated velocity impact grinding followed by pneumatic and v 10 centrifugal impact pulverization and uidization in the carrier stream, and delivery, as a pulverulent, iluidized combustible, into the pressurized combustor.

With the unit pulverizers herein, the iluidized coalbearing combustive air stream is passed through a convergent nozzle wherein it undergoes an initial pneumatic pulverization of the contained particles and an increase in Velocity. The particles in the accelerated stream are impacted, while under the eiiects of the accelerated velocity, by being projected against an annular array of peripheral rotor blades, and the now-expanding air stream sweeps the particles into a hermetically closed grinding chamber wherein annular rows of impact members rotating between one or more rows of fixed impact members subject the air-borne particles to myriads of impacts and cause them to follow a multiplicity of eddy currents set up in the chamber, whereby they are conjointly pulverized and uidized, and are swept out of the pulverizer directly into the burner.

To secure maximum pulverization, where the economics of a situation permit, the disk may be counterrotated with respect to the linear direction of the inflowing air-borne particles, whereby the effective impact experienced by the particles is changed from that due solely to the input velocity of the particles, to the sum of such velocity plus the tip speed of the counter-rotating peripheral blades. Such effect can be produced at will by shifting the gears in gear box 24.

Where is is desired to function without the use of a mechanical drive for the rotor, the gear train is disconnected, and the rotor is driven by the force of the expanding incoming pressure air stream acting on the peripheral rotor blades. In this latter case, the rotor blades are so constituted and arranged as to serve as turbo-impeller elements, as well as impact members.

The invention herein contemplates the use of but a single entrant for the introduction of theuidized solidsbearing air stream into the unit pulverizer, However, improved pulverization and fluidization can be secured by introducing auxiliary streams of plain, pressurized air into the pulverizer casing through duplicate nozzles arranged in peripherally spaced relation with respect to the entrant for the solids-bearing air stream, whereby the pressurized air is directed against the peripheral row of rotor blades acted on by the incoming solids-laden air stream. To secure this desirable result, and as shown in Figs. 1, 2, and 3, the above described pulverizer can be fitted with a pressure air entrant and air supply in the following manner:

A duplicate entrant 93a of a second duplicate nozzle a is fitted in a second angularly apertured boss 103a in casing wall 103 (Fig. 3). The nozzle includes the upstream section 91a, convergent section 92a, and the reduced throat and entrant section 93a. As in the case of the main nozzle, the throat section is about one-half the diameter of the feed pipe. The duplicate nozzle may be inserted in any portion of the casing, in the same plane as the primary nozzle. As shown in Figs. l and 2, the unit 90a may comprise a stub pipe having a threaded end receiving an elbow connection 130, into which is tapped a connecting pipe 131, incorporating a union 132. The pipe 131 is connected to pressure air feed line 79 by a T-connection and pipe section, not shown, through a second elbow 133.

With this simple arrangement, pressure air can be fed directly into the pulverizer to augment the pulverizing and fluidizing action thereof, and to sweep out the grinding chamber. Where the rotor is to be driven pneumatically, the booster compressor may deliver pressure air to

lines

78 and 79, and the combustive air delivered to line 90 may be reduced to a desired lower pressure by throttling down through controls 88-89, and 85-87 in the combustive air feed line. Under such an arrangement, the air delivered through the auxiliary nozzle acts as the driving iiuid for the rotor, and the air-borne solids may be introduced into the pulverizer, counterowing to the direction Vof rotation of the rotor, whereby the advantages of optimum pulverization are secured without the expenditure of extraneous mechanical energy. The auxiliary nozzle air supply may be readily uncoupled from the pressure air feed line 79, and the nozzle capped, while the T-connection in line 79 can be plugged, thereby restoring the unit pulverizer to its original, single entrant condition. Y

The unit pulverizer herein is simple in construction, assembly, operation and maintenance. It affords a maximum flexibility in use, being adapted for incorporation in a wide variety of systems requiring pulverization and for uidization of solids as a critical operating feature.

While I have shown and described the preferred embodiment of my invention, I wish it to be understood that I do not confine myself to the precise details of construction herein set forth by way of illustration, as it is apparent that many changes and variations may be made therein, by those skilled in the art, Without departing from the spirit of the invention or exceeding the scope of the appended claims.

What is claimed is:

1. An in-line pneumatic-mechanical unit pulverizer adapted for the conjoint pulverization and iiuidization of streaming entrainments of combustive air-borne coal particles flowing in a feed line to a pressurized combustor, comprising, in combination, a hermetic, pill-box type casing deiining a grinding chamber; a disk rotor mounted for rotation in the casing, and having close clearance with the wall thereof; intermeshing concentric rows of impact blades on a face of the rotor and the apposed face of the casing, the non-bladed face of the rotor being apposed to the adjacent face of the casing with but a slight clearance, whereby when purge air is flowed in the rotor shaft housing and into the casing through the annular gap between the rotor and the casing, and into the grinding chamber, infiltration of the pulverulent material into the shaft bearings is prevented; separate driving means for the rotor; a peripheral inlet and an axial outlet in the casing'so constituted and arranged as to cause a streaming entrainment of pressurized air-borne coal particles to traverse a radial path inwardly across the bladed face ofnthe rotor, whereby the particles are reduced and fluidized; and an entrant of reduced diameter in the inlet opening.

2. An in-line pneumatic-mechanical unit pulverizer adapted for the conjoint pulverization and fluidization of streaming entrainments of combustive air-borne coal particles owing in a feed line to a pressurized combustor, comprising, in combination, a hermetic, pill-box type casing defining a grinding chamber; a disk rotor mounted for rotation in the casing, and having close clearance with the wall thereof; intermeshing concentric rows of impact blades on a face of the rotor and the apposed face Vof the casing; driving means for the rotor; a plurality of peripheral inlets and a single axial outlet in the casing so constituted and arranged as to simultaneously cause a separate streaming entrainment of pressurized air-borne coal particles and at least one separate stream of pressurized air to traverse radial paths inwardly across the bladed face of the rotor, whereby the particles are reduced and uidized and swept out of the casing; and entrants of reduced diameter in the inlet openings.

3. Unit pulverizer according to claim 2, characterized by the fact that the peripheral entrants are directed at an acute angle to the peripheral row of rotor blades, whereby the stream of coal particles is impinged against said row of blades and the particles are reduced and uidized, and the separate air stream impinges against said blades, whereby the rotor is driven and the uidized particles are further reduced by impacts between the intermeshing rows of blades.

4. Unit pulverizer according to claim 2, characterized by the fact that the driving means for the rotor consists of pressure air jets discharged against the inlet row of peripheral rotor blades from the peripheral inlets.

5. Unit pulverizer according to claim 4, characterized by the fact that one pressure air jet is comprised of the streaming entrainment of pressurized air-borne coal particles, and the remaining jet is comprised of a pressurized stream of air at a pressure above the pressure of the tirst said jet.

References Cited in the file of this patent UNITED STATES PATENTS 853,059 Bunge May 7, 1907 1,560,766 Crites Nov. 10, 1925 1,724,072 Daniels Aug. 13, 1929 1,840,380 Andrews Jan. l2, 1932 2,100,020 Andrews Nov. 23, 1937 2,155,697 Young Apr. 25, 1939 2,414,361 Cowles Ian. 14, 1947 2,491,435 Yellott Dec. 13, 1949 2,552,596 Sheldon May 15, 1951 2,583,920 Yellott Jan. 29, 1952 2,591,141 Dulait Apr. 1, 1952 2,601,390 Hague June 24, 1952 2,625,791 Yellott Ian. 20, 1953 2,699,039 Yellott Jan. 11, 1955 FOREIGN PATENTS 693,631 Germany July 16, 1940