US2662694A

US2662694A - Tempered air swept pulverizer and classifier with common fan means to transport unclassified material and pulverized oversize particles to the classifier

Info

Publication number: US2662694A
Application number: US157519A
Authority: US
Inventors: Lotz Otto
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1949-04-28
Filing date: 1950-04-22
Publication date: 1953-12-15
Anticipated expiration: 1970-12-15

Description

Dec. 15, 1953 o. LOTZ 2,662,694

TEMPERED AIR SWEPT PULVERIZER AND CLASSIFIER, WITH COMMON FAN MEANS TO TRANSPORT UNCLASSIFIED MATERIAL AND PULVERIZED OVERSIZE PARTICLES TO THE CLASSIFIER Filed April 22, 1950 5 Sheets-Sheet l INVENTOR OTTO LOTZ ATTORNEY FAN MEANS TO TRANSPORT UNCLASSIFIED MATERIAL AND PULVERIZED OVERSIZE PARTICLE Filed April 22, 1950 O. LOTZ Dec. 15, 1953 TEMPERED AIR SWEPT PULVE 5 Sheets-Sheet 2 FIG.3

LOWER T MPERATURE GAS TEMPERATURE GAS INVENTOR OTT O LOTZ ATTORNEY Dec. 15, 1953 o. LOTZ 2,662,694

' TEMPERED AIR SWEPT PULVERIZER AND CLASSIFIER, WITH COMMON FAN MEANS TO TRANSPORT UNCLASSIFIED MATERIAL AND PULVERIZED OVERSIZE PARTICLES TO THE CLASSIFIER Filed April 22, 1950 5 Sheets-Sheet s FIG.6

FIG?

FIG.8

INVENTOR OTTO LOTZ ATTORNEY Patented Dec. 15, 1953 TEMPERED AIR SWEPT PULVERIZER AND CLASSIFIER WITH COMMON FAN MEANS T TRANSPORT UNCLASSIFIED MATE- RIAL AND PULVERIZED OVERSIZE PAR- TICLES TO THE CLASSIFIER Otto Lotz, Oberhausen, Germany, assignor to The Babcock & Wilcox Company, New York, N. Y,, acorporation of New Jersey Application April 22, 1950, Serial No. 157,519

Claims priority, application Germany April 28, 1949 19 Claims. 1

This invention relates in general to pulverizing mills of the kind comprising classifying means arranged to receive gas-borne particles and to deliver oversize particles to a milling zone. More particularly, my invention is concerned with the construction and operation of a pulverizer or pulverizing mill wherein fan means are arranged to effect the flow of two streams of gaseous fluid; one of which streams is adapted to transport to the classifying means material delivered to the mill by a feeder, and the other of which streams is adapted to transport from a .mllllng zone material delivered to that zone by the classifying means.

In one form of my invention, herein illustrated as a heater mill, material to be pulverized is directed through successive milling .or heater zones in series while a gaseous material-transporting medium is directed through the same zones in parallel; the material being transported from each milling zone in a stream of the gaseous fluid and being delivered to .a classifying zone from which fine particles are discharged to a point of use, for example, while oversize particles are returned to one of the milling zones, suitably, to a milling zone other than the initial milling zone to which material is delivered by a feeder. In another form, the initial milling zone and the associated beater are omitted and preliminary pulverization is effected solely by fan means. In each form, provision is made for separately controlling both the rates of flow and the temperatures of the two streams of gaseous fluid.

An object of the invention is the provision of pulverizing mills, of the character described suitable for dealing effectively with solid fuels of low or high moisture content, and whether of soft or hard structure. The invention furthermore includes a method of grinding moisturecontaining fuel whereby the fuel, during different stages of the grinding process, is subjected to separate streams of gaseous fluid of which the temperatures and rates of flow are separately controlled to suit the operating conditions.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

Of the drawings:

Fig. '1 is a sectional elevation of a heater mill constructed in accordance with my invention;

Fig. 2 is a fragmentary sectional elevation showing a detail modification;

Fig. 3 is a diagrammatic representation of fluid supply ducts;

i ig. l is a part sectional elevation of a modification of the beater mill shown in Fig. l

Fig. .5 and Fig. 6 are side elevational views of the beater mill shown in Fig 1, as viewed from the right and left, respectively; and

Fig. 7 and Fig. 3 are side elevational views of the beater mill shown in Fig. 4. as viewed from the right and left, respectively.

In Fig. l, a coal feeder 1 comprises an endless conveyor disposed in an air-tight casing and arranged to be driven at an adjustable speed to feed the fuel to be pulverized to the inlet of a ,pulverizing milling zone containing a beater 3 and formed with a side chamber 4 for the introduction into the milling zone of hot gaseous fluid from a duct 5.

A second beater d is disposed within a line milling zone formed with a side chamber l for the introduction into the milling zone of hot gaseous fluid from a duct 8 and between the two zones is disposed afan Shaving inlets at its sides for the axial flow of gaseous fluid from the respective zones. The

heaters

3 and 6 and the fan 9 are mounted one. common shaft to coupled to a driving motor H. llhe fan .8 is arranged to deliver the streams of gaseous fluid and solid particles to a classifier l2 disposed on the top of a common casing for the fan and heaters.

The classifier l2 includes a casing of circular cross-section, coaxial with and within which are an impact cone l3 and a whirl chamber Hi, the lower end of which terminates short of the cone l3 and is provided with gas sealing means in the form of horizontally pivoted hanging dampers or gates It; the term cone, as applied to part l3, being used broadly and thus denoting a structure of pyramidal formation, for example, whereby fiat peripheral surfaces are provided for cooperation respectively with flat gate members i5. A fine material outlet sleeve it extends downwardly within the whirl chamber to a point below an annular inlet ll at the top of the whirl chamber, which inlet is provided with a set of circumferentially spaced adjustable vanes or dampers Ila of which two only are indicated. A chute It! for oversize particles discharged from the classifier leads to the fuel inlet it to the fine milling zone, the inlet l9 being provided with a damper 20.

During service, the beater 6 is required to do more pulverizing work than the beater 3 and is provided with a greater number of beater heads than the beater 3. As shown, the heater 3 is provided with a single circular row of beater heads, whilst the beater S is provided with two rows of beater heads. The beater heads of both beaters are renewable and in order to minimize wear in the beaters e the heads thereof are of hardened material. Such heads, if fitted to the beater 3 might be damaged by tramp iron and the heads of the beater 3 are of softer material, whilst a centrifugal tramp iron separator, not shown, of suitable known construction, is arranged to remove from the fuel tramp iron before it reaches the fine milling zone. Suitably the separator is asociated with the beater 3.

If desired, the fan 9, as shown in Fig. 2, is formed with a hub having a radially extending disc portion 25, with vanes 23 on opposite sides thereof, for severally effecting flow of the two streams of gaseous fluid, the arrangement being such as to provide flow areas at the two sides of the hub suited to the respective rates of flow of the two streams.

Suitably, means shown in Fig. 3 are provided for separately controlling the rates of flow of gaseous fluids from the ducts and 8 and the temperatures of the two streams of gaseous fluid, the arrangement being such that fluid may be supplied at higher temperature from the duct 5 than from the duct 8. As indicated in Fig. 3, a conduit system is provided whereby duct 5 and duct 8 are connected through

branch ducts

25 and 26 to separate sources of hot air and hot gases, respectively, the sources not being shown. Dampers 21 and 28 are provided in the respective branch ducts for regulating the proportions of the two gaseous fluids admitted, or for admitting one fluid, either hot air or hot gases, to the exclusion of the other. Suitably,

ducts

5 and 8 are provided with dampers 3i and 32 adjacent their connections to the pulverizer side chambers 4 and i respectively. Duct 8 is provided with a tempering fluid connection 34, having a damper 35 therein, and leading from atmosphere, or other source of low temperature gaseous fluid, for the purpose of reducing the temperature of gaseous fluid supplied from duct 8 to a temperature lower than that of the fluid supplied from duct 5. An additional damper 36, if necessary, may be provided in duct 8, in advance of the tempering fluid connection 3 3, to assure inward flow of fluid through connection 36.

In operation, the feeder I delivers fuel to the pulverizing milling zone containing the beater 3 which is rotated together with the fan 9 and beater 6 and the fan draws furnace gases or hot air or a mixture of furnace gases and hot air from the duct '5 and discharges such gaseous fluid together with the preliminarily pulverized fuel, partly dried by the gaseous fluid, to the classifier l2. The fan 9 also draws hot air from the duct 3 through the fine milling zone and discharges the air together with fuel particles from that zone to the classifier.

The coarser particles discharged by the fan fall from the cone l3 onto the chute l8 and the finer particles are carried by the gaseous fluid into the whirl chamber it. In passing the vanes Ha the fluid is given a whirling movement, with the result that oversize particles are separated in the whirl chamber and are discharged past the dampers is to the chute l8, whilst the fine particle pass with the fluid through the outlet 4 sleeve IS. The particles delivered to the chute I8 pass through the fuel inlet is to the fine milling zone. It will be seen that the milling zones are arranged in parallel as regards the flow of gaseous fluid and in series as regards fuel to be milled.

The control of the mill is very flexible, since both the rates of flow and the temperatures of the'two streams of gaseous fluid may be separately controlled. The temperature of the fluid supplied to the reliminary milling zone may be substantially higher than that of the air supplied to the fine milling zone and a variation in the volume rate of flow in the preliminary milling zone as a result of temperature variations or/and variation of the mass rate of flow of gaseous fiuid can be made without a corresponding change in the fine milling zone.

Fig. 4 shows a mill in which the preliminary milling zone and the associated beater are omitted and preliminary pulverization is effected solely by the fan 9 with which is associated a tramp iron separator, not shown. The feeder l is arranged to discharge fuel into a box or side chamber 2| connected to a duct 5 for hot gaseous fluid and arranged to deliver the gaseous fluid and fuel to one of the axial inlets of the fan. A duct 8 is arranged to discharge hot air tangentially to the fine milling zone containing the beater 6. Otherwise the mill is similar to that illustrated by Fig. l, with fan 9 modified, if desired, as shown in Fig. 2. Similarly, provision may be made, in accordance with Fig. 3, for separately controlling the temperatures and rates of flow of the respective streams of gaseous fluid to which the fuel is subjected.

While in accordance with the provision of the statutes I have illustrated and described herein the best form of my invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. A pulverizing mill to which material is delivered by a feeder and comprising classifying means arranged to receive gas-borne particles and to discharge oversize particles therefrom, said mill having a milling zone to which said oversize particles are delivered, fan means arranged to effect the flow of two streams of gaseous fluid, stationary wall means defining a chamber for said fan means separate from said zone, means forming an outlet from said chamber for directing the first of said streams to said classifying means together with particles of said feeder delivered material, and means for directing the second of said streams through said milling zone and thence through said chamber to said classifying means together with material delivered to said zone by said classifying means, said milling zone being arranged to receive particles of material delivered thereto only from said classifying means.

2. A pulverizing mill as defined in claim 1 wherein a. separate milling zone is interposed in the path of said first stream and between said fan means and the location at which material is fed to the mill.

3. A pulverizing mill comprising classifying means arranged to receive gas-borne particles and to deliver oversize particles to a milling zone,

said mill having separate gaseous fluid inlets opening respectively to said milling zone and to a material inlet chamber adapted to receive incoming raw material, fan means arranged to effect the flow of separate streams of gaseous fluid inwardly through said inlets, stationary wall means separating said milling zone from said material inlet chamber and defining an intermediate chamber for said fan means, and means including an outlet connecting said fan means chamber to said classifying means for directing said streams through said milling zone and said inlet chamber and thence through said fan means chamber to said classifying means, said milling zone being arranged to receive particles of material delivered thereto only from said classifying means.

i. A pulverizing mill as defined in claim 3 wherein the milling zone includes beater means rotatable in a common direction with said fan means.

5. A pulverizin mill comprising classifying means arranged to receive gas-borne particles and to discharge oversize particles therefrom, means defining a milling zone arranged to receive said oversize particles and having a gaseous fluid inlet, said mill having a raw material inlet and a gaseous fluid inlet each opening to a chamber adapted to receive incomin raw material, ran means arranged to effect the flow of separate streams of gaseous fluid inwardly through said gaseous fiuid inlets, stationary wall means defining a compartment for said fan means separate from said milling zone, and means directing said streams in parallel through said milling zone and said chamber and thence through said fan means compartment to said classifying means, said milling zone being ar ranged to receive particles of material delivered thereto only from said classifying means.

6. A pulverizing mill as defined in claim 5 wherein the milling zone and said chamber respectively contain beater means arranged for rotation about a common axis, and means for rotating said fan means and said beater means in a common direction about said axis.

7. A pulverizing mill having two separate chambers each having a gaseous fluid inlet, stationary walls defining a compartment separating said chambers, beater means in a single one of said chambers so as to form a milling zone, the other of said chambers being arranged to receive raw material delivered to the mill by a feeder, fan means operable within said compartment and inducing the flow of separate streams of gaseous fluid in paralle1 through said chambers, classifying means arranged to receive gas-borne particles and to discharge oversize particles therefrom, outlet duct means arranged to receive from said fan means and to direct to said classifying means the total discharge of gaseous fluid and entrained particles received from said chambers including said milling zone, and means for directing to said milling zone oversize particles discharged from said classifying means.

8. In a pulverizing mill, means defining a milling zone, classifying means arranged to receive gas-borne particles and to discharge oversize particles therefrom, said mill having separate gaseous fiuid inlets opening respectively to said milling zone and to a chamber arranged to receive material delivered to the mill by a feeder, stationary walls defining a compartment separating said milling zone from said chamber,

fan means disposed within said compartment and arranged to effect the flow of separate streams of gaseous fluid inwardly through said inlets, means for directing said streams separately through said milling zone and said chamber respectively and thence through said compartment to said classifying means, and means directing to said milling zone oversize particles discharged from. said classifying means.

9. In a pulverizing mill, the comb ration as defined in claim 8, and further comprising beater means arranged in said chamber and forming therewith a second milling zone interposed in the path of one of said streams and between the fan means and the location at which material is fed to the mill.

10. A pulverizing mill having separate chambers each having a gaseous fluid inlet, means associated with one of said chambers so as to form a milling zone, another of said chambers being arranged to receive raw material delivered to the mill by a feeder, stationary Walls defining a compartment separating said chambers, fan means operable within said compartment and inducing the flow of separate streams of gaseous fluid in parallel through said chambers, classifying means arranged to receive gas-borne particles and to discharge oversize particles therefrom, means associated with said fan. means for directing to said classifying means the total discharge of gaseous fluid and entrained particles received from said chambers including said milling zone, and means for directing to said milling zone oversize particles discharged from said classifying means while separately directing the remainder of the total discharge to the exterior of the mill.

11. A pulverizing mill as defined in claim 10 wherein the fan means comprise a rotor with a radially extending wall on opposite sides of which are blades for respectively effecting the flow of the separate streams of gaseous fluid.

12. A pulverizing mill as defined in claim 10 wherein said chambers and said fan means are contained within a common casing, and wherein the classifying means are arranged directly above said casing.

13. A pulverizing mill as defined in claim 10 wherein the classifying means include a whirl chamber formed with an oversize particle outlet, and means forming a gas seal for said outlet comprising hanging damper means.

14. A pulverizer mill as defined in claim 13 wherein the gas seal forming means includes an impact cone in the path of the discharge from said fan means and having its apex toward said outlet, said cone having lateral surface portions adapted to cooperate with said damper means to form said seal.

15. A pulverizing mill as defined in claim is and further comprising means for supplying the stream which first contacts the material to be pulverized at a temperature higher than that of the stream which passes through the milling zone arranged to receive oversize particles from the classifying means.

16. A pulverizing mill as defined in claim 10 wherein means are provided for separately controlling the rates of flow, and the temperatures, of the separate streams of gaseous fluid.

17. A pulverizing mill having separate milling zones each containing beater means, classifying means arranged to receive gas-borne particles and to discharge oversize particles therefrom, feeder means arranged to deliver raw material to one of said zones, means for conducting to another of said zones oversize particles discharged from said classifying means, stationary walls defining a compartment separating said milling zones, fan means operable within said compartment and efiecting the flow of separate streams of gaseous fluid in parallel through said zones for entrainment of material, and outlet duct means arranged to receive from said fan means and to direct to said classifying means the streams of gaseous fluid and entrained material discharged from said pulverizing zones.

18. A pulverizing mill as defined in claim 17 wherein each beater means comprises radially extending heads and wherein the beater means associated with the zone to which oversize particles are conducted is formed with a greater number of heads than the beater means associated with the zone to which material is delivered by feeder means.

19. A pulverizing mill comprising classifying means arranged to receive gas-borne particles and to deliver oversize particles to a milling zone while separately discharging gas-borne finer particles to a point of use exteriorly of the mill, said mill having separate gaseous fluid inlets opening respectively to said milling zone and to a material inlet chamber adapted to receive incoming raw material, stationary walls defining a compartment separating said milling zone from said material inlet chamber, fan means operable within said compartment and arranged to effect the flow of separate streams of gaseous fluid through said inlets, means including an outlet connecting said fan means compartment to said classifying means for directing said streams through said milling zone and said inlet chamber and thence through said fan means compartment to said classifying means, and means for separately controlling the temperatures and rates of flow of said separate streams of gaseous fluid whereby the temperature of fluid supplied to said material inlet chamber is normally higher than the temperature of fluid supplied to said milling zone.

O'ITO LOTZ.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,520,537 Markus Dec. 23, 1924 1,527,818 ONeill Feb. 24, 1925 1,543,556 Denis June 23, 1925 1,591,283 Charton July 6, 1926 1,955,255 Sengstaken Apr. 17, 1934 FOREIGN PATENTS Number Country Date 112,997 Switzerland Dec. 16, 1925 365,59? Great Britain Jan. 18, 1932 682,172 Germany Oct. 9, 1939