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Патент USA US2403976

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July 1, 3946.
J. L HARVEY
'
2,403,976
SYSTEM OF PULVERIZING, FEEDING, AND TRANSPORTING OF MATERIAL
Filed May 22,.1943
‘
INVENTOR.
JamesL Harvey
BY
ATTORNEY
Patented July 16, 1946
2,403,976
UNITED STATES PATENT OFFICE
2,403,976
SYSTEM OF PULVERIZING, FEEDING, AND
TRANSPORTING OF MATERIAL
James L. Harvey, Wadsworth, Ohio, assignor to
The Babcock ‘& Wilcox Company, Rockleigh,
N. J ., a corporation of New Jersey
Application May 22, 1943, Serial No. 488,013
12 Claims.
(01. 241--34)
1
2
system providing for the pulverization of a solid
material capable of being transported in a ?nely
been found that the quantity of pulverized coal
discharged from the pulverizer is substantially
proportional to the rate of ?ow of primary air
divided state by means of a current of air or other
therethrough so long as a proportional amount
gaseous medium. The material may suitably be
a fuel such as coal, although other fuels, or other
istic of air-swept pulverizer operation is utilized
The invention disclosed herein pertains to a
of coal is maintained therein.
This character
in U. S. Patent 1,965,643 to R. M. Hardgrove
whereby the feed of material to the pulverizer is
materials of a non-combustible character, are
equally within the scope of the invention. The
invention further contemplates transportation of
controlled to maintain a certain level or reserve
the pulverized product to one or more points of 10 quantity of material in the pulverizer for the
use.
A speci?c application of the invention is to an
air-swept pulverizing and distributing system
wherein a current of air or other gaseous medium
is maintained throughout the system for remov
ing pulverized fuel from a pulverizer and for
transporting the pulverized fuel direct to one or
more burners in the manner commonly referred
to as “direct-?ring.” Nevertheless certain fea
tures of the invention may be found useful in 20
other known systems employing such additional
apparatus as cyclones, storage bins, and feeders
incident to the transportation of the pulverized
material from the pulverizer to the ultimate point
of use.
-
r
In a direct-?red system employing a plurality
of burners in one or more furnaces, it may often
be found desirable to utilize a single pulverizer
for supplying the entire fuel requirements of
several burners operating simultaneously. Where
a number of small furnaces are involved, it may
also be found both convenient and economical to
distribute fuel to the burners of several furnaces
from a single continuous main conduit system
existing rate of ?ow of primary air.
According to the present invention, an air
swept pulverizer and transport system is proposed
wherein any desired proportion of the pulverizer
output may be withdrawn, and any remaining
proportion circulated by being returned to the
pulverizer, or in part to the pulverizer and in
part to some other point in the system in ad
vance of a point of withdrawal, the proportions
of the mixture so withdrawn and returned being
varied as desired for a given value of pulverizer
output, or for different values.
As an accompaniment to such an objective, it
is proposed to maintain under all conditions a
proper relation between fuel and air in the mix
ture available for withdrawal.
An additional object concerns the supply of raw
material to the system and the maintenance of a
proper reserve of material in the process of pul
verization within the pulverizer, each in relation
to varying demands on the System.
Another object contemplates controlling the
rate at which raw material is fed to the pulverizer
in accordance with ?uid flow conditions within
the system, including for example, the rate at
having both ends connected‘ to the pulverizer to
which a portion of the pulverizer output is re
turned for recycling.
the ?uent. fuel mixture; individual burners being
A further object is to correlate indications of
supplied through individual branch lines con
fluid pressure conditions existing at different
nected to the conduit at intervals along its length,
and any surplus quantity of the mixture above 40 points in the systemfor the purpose of controlling
pulverizer operation.
that required by the burner or burners in opera
These and other related objects of the inven
tion being returned in whole or‘in part to the
tion may be achieved in the manner about to be
pulverizer or other advance point in the system
provide a closed circulating path or circuit for
for recycling,
described, an arrangement of apparatus suitable
'
If one or more burners should be operated at if for the purposes of the invention being diagram
matically indicated in the accompanying draw
varying capacities, or if the cycles of operation
of individual burners should be different, the re
mg.
sulting changes in overall fuel consumption make
it necessary to provide suitable adjustment of the
rate at which material is fed to the pulverizer.
Such conditions may be found in metallurgical
plants, for example, where a different number of
In the drawing, an air-swept pulverizer I0 is
shown with its associated feeder I2 by which raw
50 unpulverized material such as coal, is fed to the
furnaces for the same or diiierent processes may
speed electric motor l6, for example, as a means
be in operation over different periods, thus caus
of providing different rates of feed.
ing abrupt and Wide variations in fuel consump- '
tion for which there must be adequate control of
pulverizer operation to suit each new condition.
In the usual direct-?red system where the
entire output of the pulverizer is utilized and none
pulverizer from a suitable bin 14 or other source
of supply, the feeder being driven by a multi
Air or other gaseous medium to provide a car
rier for the pulverized material is admitted to
the pulverizer through an inlet duct M3 by which
the carrier medium at an elevated temperature
is supplied from a source not shown, a branch
of the mixture is returned for recycling, it has 60 inlet 20 conveniently open to the atmosphere pro
2,403,976
4
3
viding a means for admitting tempering air to the
being operatively connected to the rotating spin
duct I8; regulating dampers 22 and 2:1 being
dle ~56 to which an extension casting {i8 is ?tted
suitably provided in the respective inlet connec
to provide an annular passage or throat 18 for
directing the carrier air into the grinding zone.
tions for maintaining the temperature of the car
rier medium entering the pulverizer at a desired
predetermined value.
A fan 26 connected to the pulverizer outlet by
A duct 12, formed in the base of the pulverizer
and open at its upper side to the throat 10, pro
vides a mixing chamber for fresh incoming pri
mary air entering at one end from inlet duct i8
the discharge duct 28 induces a draft through the
and for the surplus fuel-air mixture entering at
pulverizer which causes the carrier air to pass
into the pulverizer from the duct 18 and to pass it a location adjacent its opposite end from the
return line 52. The introduction of the surplus
through the pulverizer where it picks up the pin
mixture at the level indicated takes advantage
verized material to provide a ?uent mixture,
of the conical formation of the pulverizer casing
which for the purpose of this example may con
as at ‘M which serves to deflect the returning,
sist of pulverized fuel suspended in a stream of
primary combustion air, the term “air” being
used generally whether or not a portion of the
carrier medium is obtained, as is sometimes the
case, from a source of hot ?ue gases. . The mix
ture is discharged from the pulverizer through
the duct 28 as a ?uent stream, passing through ~
the fan 26 and into the fuel main 39 from which
it is delivered to one or more points of use.
The illustrated embodiment provides for de
livery of the pulverulent fuel mixture to a plu
rality of burners 32, 3'4, 36 and 38 associated with
a plurality of furnaces 4%, t2 and/ill, each burner
line 43 preferably being ?tted with a plug valve
d?egadjacent its connection to the fuel main to,
and with a second valve ‘58 of the butter?y type
intermediate the plug valve and the burner. The
plug valves are for the purpose of cutting off
and completely isolating the supply of fuel from
mixture downwardly into the duct 12 and oblique
ly against its bottom wall, thus producing a de
gree of agitation which tends to promote a re
distribution of the fuel particles within the cham
ber and a more thorough mingling of the two
streams to provide a relatively homogeneous total
mixture of fuel and primary air for admission
through the annular throat ‘It.
It is evident that in the operation of a direct
?red circulating system such as has been de
scribed, there can be wide variations in fuel
consumption due to the ability to operate a
different number of burners at different times,
and, if necessary, to operate individual burners
at varying capacities. The resulting variations
in fuel consumption impose varying demands on
the pulverizer unit so that it becomes necessary
to increase or decrease the rate at which raw
coal is fed to the pulverizer, such changes in
load requiring a change in the rate of fuel
valves serve as a means'for regulating the flow of 35 input which while satisfying the demand for a
dilferent output of pulverized fuel will also main
‘fuel to such burners as are in operation. In
individual burners so that any number of burners
maybe operated, as desired, while the butter?y
practice, the fuel main 333 may be so arranged
tain the proper level or reserve of material in
that the .greater part of its length is horizontally
the pulverizer for the particular load involved;
the level of material being preferably increased
disposed “and at a level higher than the level at
which the burners are located, thus enabling the 40 as the load is increased and decreased as the
burner lines 56 to be conveniently connected to
load is decreased.
Since the pulverized fuel is maintained
the under side of the fuel main 3!] and to extend
vertically downward therefrom for connection to
throughout the system in a ?uent state, that is,
individual burners. A secondary supply of air
in suspension in a current of primary air or other
may be admitted to the burners or to the fur 45 gaseous carrier medium, an indication may be
naces for combustion purposes, but the details of
obtained of the rate of flow of the ?uent fuel
such secondary supply do not enter into the sub
mixture through a given portion of the system
ject of the present invention and are therefore
by measuring the pressure differential across that
omitted from the drawing.
particular portion. A similar measure may be
The fuel main 3.9 is continued beyond the last 50 obtained of the rate at which air is supplied to
burner to be served, here indicated as burner 38
the system. These are factors which enter into
for furnace 134, to provide a conduit length 52 for
the control of pulverizer operation in the present
returning to the pulverizer any surplus quantity
of the fuel-air mixture which is not delivered to
the-burners, the return length 52, as shown, be
ing connected to the pulverizer ill at a location
opposite to the location at which the primary air
is admitted through duct l8, and at a somewhat
higher level. There is thus provided a single
continuous main conduit system consisting of the
.disohargeduct 28, fan 25 and fuel main 38 in
cluding its return length 52, having both ends
connected to the pulverizer iii and thereby form
ing a closed path or circuit’ over which at least
a portion of the mixture initially discharged from
thev pulverizer maybe circulated. The fuel main
30 may be formed of different sizes of conduit
with reductions in cross section at intervals as
at 56, 56 and 58 to maintain a sumciently high
velocity of ?uid flow throughout to prevent fuel 70
from settling out of the ?owing mixture.
The pulverizer shown is of a known type utiliz
ing a circular series of steel balls 63 operating
between a stationary lower grinding ring '52 and
a revolving upper grinding ring 64, the latter
system.
Referring again to the drawing, a measure of
air flow to the pulverizer is conveniently ob
tained by employing an ori?ce 16 in the inlet
duct l8, the resulting differential pressure across
the ori?ce being transmitted by tubes 18 and 8D
to the pressure sensitive diaphragm 82 suitably
mounted for movement within a stationary
casing 84. The pressure differential resulting
from the ?ow of air and coal in suspension
through a selected portion of the pulverizer, in
cluding particularly the grinding zone thereof,
is transmitted by tubes 86 and 88 to the pres
sure sensitive diaphragm 9!] within the casing
92, the tube 86 being connected to a pressure
point in advance of the grinding zone, for con
venience to the downstream side of the ori?ce
16 as in the case of tube 86 for diaphragm 82,
and tube 88 being connected to a pressure point
following the grinding zone, for convenience to a
point adjacent the pulverizer outlet.
The rate
at which surplus fuel and air are returned to
the
pulverizer under
varying
conditions is
2,403,976
5
6
tance from a ?xed fulcrum point II2, the lever
arm distances in both instances being suitably
at a predetermined “high.” rate to restore the nor
mal operating level for the required rate of pul
verizer output. If the level or reserve quantity of
increase or decrease of the pressure differential
measured in terms of the pressure differential
across the pulverizer.
across a selected portion of the return conduit
Therefore, with return flow through conduit 52
52, tubes 94 and 06 being connected to the con
practically zero, the entire control of pulverizer
duit at relatively widely separated locations and
operation is subject to the relative forces exerted
the existing pressure differential transmitted
by diaphragms 82 and 90 on lever I02, whereby
thereby to the pressure sensitive diaphragm 98
motor IE will be operated at intervals at the
within the casing I 00.
proper speeds to provide a fuel-air mixture of a
The relative pressures acting upon diaphragm
predetermined fuel-air ratio at the required pul_
82, 90 and 98 are coordinately utilized to effect
movement of the lever I02 which is pivoted about 10 verizer output; the term “fuel-air ratio” being de
?ned as the cubic feet of air at pulverizer outlet
a point I04 ?xed in relation to the casing 84
temperature per pound of fuel.
at one side. The lever I02 carries a contactor
When the opposing forces exerted on lever I02
element I05 whereby upon movement of the
by the diaphragms 82 and 90 are balanced, the
lever I02 abouts it pivot point I04 certain electri
cal circuits to be later described are selective 15 contactor I06 is held clear of all upper and lower
contacts I48, I42, I44 and I46, and feeder, I2 is
ly energized to control the operation of the
operated tov feed material to the pulverizer at a
feeder motor I ii and thereby the rate at which
predetermined “low” rate. If the level or reserve
coal is fed to the pulverizer.
quantity of material within the pulverizer should
The force exerted by diaphragm 82 is‘ trans
mitted to the lever I02 by means of a pin I03 20 decrease, ,thus decreasing differential pressure
across the pulverizer, the force exerted by dia
movable with the diaphragm 82 and extending
phragm 02 overcomes the force exerted by diae
through opposite walls of the casing 84, one end
phragm 90, and lever I02 is moved counterclock
of the pin engaging the lever I02 at a prede
wise to cause contactor I06 to successively con—
termined distance from. the fulcrum point I04,
tact the upper contacts I40 and I42, and feeder
The opposite end of pin I00 engages a second
I2 is operated to feed material to the pulverizer
pivoted lever IIO also at a predetermined dis
equal as shown.
The force exerted by diaphragm 99 is applied
BI)
to the lever I02 by means of a pin II4 extend
ing through, a side wall of casing 92, and sim
ilarly, the force exerted by diaphragm 98 is ap
plied to the lever IIO by means of a pin 'IIB
extending through a side wall of easing £60. The :
casings 92 and I00 preferably have adjustable
mountings as at H8 and I20, whereby their
positions may be varied relative to the respective
fulcrum points I04 and H2, to thus increase or
material within the pulverizer should increase be
yond the normal operating level, the differential
pressure across the pulverizer is correspondingly
increased, and the force exerted by diaphragm 90
overcomes the force exerted by diaphragm B2, and
lever W2 is moved clockwise tolcause contactor
W5 to successively contact the lower contacts I44
and MB, and operation of feeder i2 ceases.
When operation of the system is such that an
appreciable ?ow of the pulverized material and
decrease the lever arm distances at which the 40 air mixture occurs in the returnline 52, the den
sity of the ?uid admitted through the pulverizer
forces exerted by diaphragms 90 and '98 are
throat ‘I0 is increased and the same relation of
applied to the respective levers I02 and H0.
pulverizer differential to fresh air differential no
Springs I22 and I24 are provided to apply
longer holds. Furthermore the new relation may
an initial loading to the levers I02 and H0
respectively, each spring having an adjustment
45 be subject to variations due to the varying rates
at which the mixture islreturned, ‘and to the re
lation Which the proportion of the mixture re
turned bears to the total pulverizer output for a
It may be assumed that the burners shown
given load.
are of such capacities that when all are operating
Assuming one of the burners, burner 32 for
simultaneously at full ratings the total delivery 50
example, to be shut off, the proportion of the total
of- fuel and air tothe burners is practically equal
pulverizer output formerly delivered to that
to the total output of fuel and air from the
burner becomes a surplus proportion of the total
pulverizer, in which case there is a minimum of
mixture which is returned through conduit 52 to
surplus fuel and air being returned to the pul
the pulverizer I0 where it is mingled with the
verizer and the differential pressure transmitted
fresh air entering through inlet I8 for combined
through tubes 04 and 90 approaches zero. Under
flow through the pulverizer throat ‘10, the result
such conditions, virtually ‘clean air alone is ad
ant modi?ed mixture constituting in effect a mod
mitted through the pulverizer throat and, in ac
i?ed carrier medium of increased density. Tests
cordance with known characteristics of air
have indicated that when an appreciable propor
swept pulverizer operation, the‘ differential pres
tion of the mixture is returned to the pulverizer,
sure’ across the clean air ori?ce l6, as transmitted
as through the conduit 52, the relation between
.through tubes ‘I8, 80 to diaphragm 82, bears a
the differential pressure across the pulverizer and
de?nite relation to the di?erential pressure
the differential pressure across the clean air ori~
across the pulverizer I0, as transmitted through
tubes 86, 88 to diaphragm 00; this relation being 65 ?ce ‘I6 is modi?ed, as compared with the relation
for zero return flow, and that the relative re
determined by the pulverizer design and ,the
sponse of the two diaphragms 82 and 90 is also
grindability, sizing, and moisture content of the
modi?ed.
fuel being handled. As long as the fuel char
In order to compensate for the effect which re
acteristics remain the same, and air ?ow through
turn flow has on the functioning of diaphragms
the pulverizer is kept constant, the pressure dif
82 and 90, the third diaphragm 98 is made re
ferentia1 across the pulverizer cannot be in
sponsive to ?uid flow conditions in the return line
creased or decreased without an accompanying
52, as indicated by differential pressures trans
increase or decrease of the pulverizer output; and
I26 by which a desired degree of tension or
compression may be obtained.
conversely, the pulverizer ‘output cannot be in
creased or decreased without an accompanying
mitted through tubes 94, 96, the diaphragm 98
acting to oppose the operation of diaphragm
7
2,403,976
90 and to assist the operation of diaphragm 82;
the force exerted by diaphragm 98 being applied
to lever H0 and transmitted through pin I08 to
lever I02, so that the operation of diaphragm 98
is superimposed on the operation of diaphragms
B2 and 90 which normally act to control the sup
ply of raw material in relation to fresh air to
maintain a fuel-air ratio of constant value, or of
a predetermined range of values, throughout the
8
contact I40, and then additionally with contact
I42. Movement of lever I82 inv the opposite di
rection causes contact to be made ?rst with con
tact I44 and then additionally with contact I46.
Lead I48 connects the contactor I08 with a con
tact I58 at the “automatic” position of switch
I38.
, Upper contact I42 is connected to one terminal
of the relay coil‘ I52 by lead I54, while upper con
entire range of pulverizer output capacities. 10 tact I40 is connected to the same terminal
Based on the known pulverizer characteristics as
through the normally-open relay switch I56. The
heretofore mentioned, such predetermined values
other terminal of relay coil I52 is connected to
of fuel-air ratios may be Obtained by suitable ad
terminal I32 of the transformer secondary by
justment of the position of diaphragm 60 relative
means of lead I58 which serves as the common
to the fulcrum I04, and by suitable adjustment of
transformer return connection for the various
the spring I22; the diaphragm adjustment being
made for maintaining either a constant or vary
ing fuel-air ratio throughout a given range of pul
verizer capacities, and the spring adjustment
transposing the value of fuel-air ratio by the
same amount for all capacities within the‘given
range. The combination of these two simple ad
justments provides a means for securing the de
sired value or values of fuel-air ratio for the par
ticular arrangement of burners. The return of
a proportion of the outgoing mixture to the pu1~
verizer adds to the amount of pulverized material
and air flowing through the pulverizer, and ac
cordingly tends to increase the differential pres
sure across the pulverizer, thereby modifying the
normally ?xed relation between the differential
pressure across the mill I0 and the di?erential
pressure across the air inlet'ori?ce 15. The dia
phragm 98 acting in opposition to the pulverizer
relay coils shown.
Lower contact I46 is connected to one terminal
of the relay coil I60 by lead I62, while lower con
tact I 44 is connected to the same terminal? through
the normally-open- relay switch I641. Theother
terminal of relay coil I??'is connected to termi
nal‘ I32 of the transformer secondary through the
commonconnection I58.
A second contact I66 at the “automatic” posi
tion of the selector switch I33 is connected by
lead I68 to one side of the normally-closed relay
switch I10, the other side of which is connected
through the normally-open relay switch Hi2 to
one terminal of relay coil I14, and through the
normally-closed relay switch I16 to one terminal
of relay coil‘ I18. The other terminals of relay
coils I14 and I18 are connected to terminal I32
of the transformer secondary through the com
mon return I58.
differential diaphragm 96 serves to cancel out 35
Switches I88 and I82 are three-pole switches,
operated respectively by the relay coils I14 and
H8, for establishing connections between the
main power supply lines “AC” and the high and
low speed windings of_ the feeder motor I6; a
fresh air as in the case where none of the mixture 40 three-wire connection I84 leading from switch
is circulated and, in consequence, fluid ?ow
I80 to the high speed winding, and a three-wire
through the return line 52 is zero. The differen
connection I86 leading from switch I82 to the
tial pressure transmitted through. tubes 94 and 98
low speed winding.
to the diaphragm 58 need not be of any speci?c
‘When the selector switch I38 is set for auto
value since a compensating adjustment‘ may be v matic operation the motor I6 will operate at low
made as at I20 to suitably position the diaphragm
speed as long as contactor I06 is held clear of all
relative to the fulcrum I I 2 for lever I It.
contacts I40, I42, I44 and I46. Under such con
Any number of burners may be cut in or out
ditions, the relay coil I18 is alone energized,
as desired, and in accordance with operations re
whereby the associated switch I82 is held closed,
ported to date, varying loads may be carried '“ and ,power is supplied only through connection
with thecontrol apparatus functioning satisfac
I86 to the low speed winding of the motor; the
tcrily throughout a range as high as 8:1 in. pul
control
circuit extending from the transformer
verizer capacities.
terminal I30, through lead I34, switch arm I36,
The manner in which movement of the lever
switch contact I66, lead I68, normally-closed re
I 02 is correlated to operation of the feeder motor "= lay switches I10, I16, relay coil I18, and return
I5 will be understood from the wiring diagram
connection I58 to the transformer terminal I32.
which by way of example is based on a source of
Counterclockwise movement of the lever I02
three-phase alternating current supply for oper
causing contactor I05 to contact upper contact
ation of an electric motor having separate wind
I 40 results in the control circuit voltage being ap
ingsfor different speeds. A transformer I28 suit- ;,. plied to one side of the normally-open relay
ably connected to the main supply lines “AC”
switch I56. When contactor I85 is brought into
provides reduced voltage at its secondary termi
contact with upper contact I42, there is a circuit
nals I38 and I32 for the several control circuits,
established through the relay coil I52 whereby
the secondary terminal I30 being connected by
the associated relay switches I51‘, I12 and I16
that component of the pressure drop through the
pulverizer which is due to the returned pulverized
material and air, and enables the operation of
feeder I2 to be kept in step with. the incoming
lead I34 to the arm I36 of a selector switch I38,
the switch arm I35 being shown in the “off”
position.
Four adjustably ?xed contacts I40, I42, I44
and I43 are shown arranged in pairs at opposite
sides of the movable contactor element I06, the
contacts I48 and I44 being adjusted to points
nearer to the contactor I06 than the contacts I42
and I46, and the contactor I 05 being made flex
ible so that movement of the lever I62 in one
direction causes contact to be‘ made ?rst with
are actuated, and the motor I6 caused to run at
high speed. The control‘ circuit in this case is
from‘ the transformer terminal I30, through lead
I34, switch arm I36, switch contact I36, lead I68,
normally-closed relay switch I10, through nor~
mally-open relay switch I12 now closed, relay coil
I14, and return connection I58 to the transformer
terminal I32. The opening of switch I16 opens
the circuit through relay coil I‘I'8'to interrupt
the power supply to the low speed winding, while
the closing of switch I12 completes the circuit
2,403,976
,9“
through relay coil I14 to close switch I80 and
thereby transfer the power sup-ply to the high
speed winding. The motor will continue to op
erate at high speed. as long as contactor I06 re
mains in contact with upper contact I40, whether
or not contact is broken with upper contact I42.
10
2. In a system of theclass'described, an air-‘
swept pulverizer having an annular grinding
zone within the lower portion thereof in which
material in the process of pulverization is main
tained during normal operation, said pulverizer
having an outlet from its upper portion for- dis
charging a ?uent mixture comprising pulverized
Clockwise movement of lever I02 results in
material suspended in air, ‘means for withdraw-l
similar successive contacting of lower contact
ing from said system varying‘ amounts of" the
points I44 and I46 by contactor I06. When con
tact is made with point I46 the power supply to 10 total mixture discharged from said pulverizer
outlet, means for supplying air to saidpulverizer
the motor I5 is cut off and the motor stops, the
at a level below said grinding zone, means"sep—
contact with point I46 causing relay coil I60 to
arate from said air supplying means for return
be energized and the associated relay switches
ing to said pulverizer a remaining portion of said
I64 and I ‘I0 to be actuated; the opening of nor
mally-closed switch I10 interrupting the control 15 mixture at a density substantially equal to the
density of the. total mixture initially ‘discharged.
circuit through transformer I28 so that neither
relay coil I14 nor I18 is energized and both power
means for mingling the returned portion of said
mixture with said supplied air, means for direct‘
switches I80 and I82 remain open.
ing said returned portion mingled with said sup
Additional contacts I88 and I90 may be pro
vided on the selector switch I38 if it is desired 20 plied air‘ upwardly through said pulverizer inclu
to include manual control of motor operation.
sive of said grinding zone, means for feeding
For this purpose, a connection may be made from
material to be pulverized into said pulverize'r
contact I88 direct to point I92 of the circuit, and
above said grinding zone, means for regulating
another from contact I90 direct to point I94,
said feeding means comprising pressurevsensitive
whereby low- speed or high speed operation may
means responsive to a pressure differential in
be obtained by moving the switch arm I36 either
dicative of said mingled ?uid flow through said
to contact I88 or to contact I90.
pulverizer inclusive of said grinding zone, and
Certain features disclosed herein are also dis
means for rendering said regulating means op
closed and claimed in my copending application,
erative in accordance‘ with a‘ measure of the .re
30
Serial No. 531,776, ?led April 19, 1944.
turn flow of said remaining mixture portion. " '
The invention as herein disclosed in accord
3. In combination with an air-swept pulverizeri
ance with the provisions of the statutes will be
arranged to discharge a fluent mixture of pul
understood by persons skilled in the art to be ap
verized material and air, means for feeding ma?
plicable in arrangements other than those spe
terial to be pulverized to said pulverizer, means
ci?cally described, and to include features which
for returning a portion of said mixture to said
may be used to advantage without a correspond
pulverizer,.means for regulating the rate at which
ing use of other features, within the scope of the
said material to be pulverized is fed to said pul;
appended claims.
verizer, and means responsive to the flow of said
portion being returned for controllingtheloper;‘
I claim:
1. In combination with a pulverizer having an 40 ation of said last named means to maintain a
annular grinding zone in a lower portion thereof
predetermined ratio of air to‘ material in said
wherein a reserve of material in the process of
mixture.
;
pulverization is maintained during normal op
4. In combination with an air-swept pulverizer
eration, said pulverizer having an outlet at the
arranged to discharge a ?uent mixture of'pul
upper side of said grinding zone, means for feed
verized material and air, means for feeding ma
ing material to be pulverized into said pulverizer
terial to be pulverized to said pulverizer at vary
above said grinding zone, means forming an an—
ing rates to’ provide varying output capacities,
nular throat passage marginally of said grind
means for returning'a portion of said mixture to
ing zone, means for maintaining an upward cur
50 said pulverizer, means for regulating the rate at
rent of air through said annular throat passage
which said material to be pulverized is fed to
for discharging through said outlet a fluent mix
said pulverizer, and means responsive to the flow
ture comprising pulverized material suspended
of said portion being returnedffor' controlling the
in said air, a main conduit having one end con
operation. of said last named means , to main;
tain the ratio of air to material in said mixture
nected to said outlet and having its opposite end
open to the interior of said pulverizer at the
lower side of said grinding zone, means for with
drawing from said conduit varying proportions
of said pulverizer output mixture, said conduit
substantially constant at said varying ‘output ca
pacities of said pulverizer.
'
'
‘
5. In combination with an air—swept pulver;
izer arranged to discharge a ?uen‘tymixture of
constituting a conductor for returning a remain
pulverized material and air, means for feeding
ing proportion of said mixture to said pulverizer 60 material to be pulverized to said ‘pulverizer,
at a density substantially equal to the densityof
the total mixture initially discharged, means sep
arate from said conduit for admitting said air
to said pulverizer, means for causing said re
turned proportion of said mixture to ‘become
mingled with said air ‘at a location axially below
and adjacent said annular throat passage for
combined upward ?ow through said pulverizer,
and means for regulating said material feeding
means comprising pressure sensitive means re
sponsive simultaneously to pressure differentials
indicative respectively of said air admission to
said pulverizer and of said combined ?uid flow
through a predetermined portion of said pulver
izer inclusive of said annular throat passage.
means for delivering a portion of said mixture to
a point of use, means for returning the remain—
der of said mixture to said pulverizer, means for
measuring the rate at which said remainder is
returned to said pulverizer, and means controlled
by said last named means for regulating the op
eration. of said feeding means.
I
>
6. In a continuous conduit system including a
pulverizer, means for supplying material, to be
pulverized ,to said pulverizen'means for supply
ing carrier air to said pulverizer for transport
ing pulverized material therefrom and through
said system, means for withdrawing a portion of
said pulverized material and air from a part of
11
2,4059%
12
said system other than said pulverizer, means
tion of said pulverizer, means for measuring the
rate at which said pulverized material and air
are returned to the pulverizer, and means under
thejoint control of said three named measuring
for maintaining another portion of said pulver
ized material and air in circulation throughout
said system, means for regulating the rate at
which said material to be pulverized is supplied U! means for regulating the rate at which said ma
to said pulverizer, and means responsive to the
terial to be pulverized is supplied to said pulver
rate of circulation of said other portion of pul
men
verized material and air for controlling the op
11. In combination with a pulverizer having a
eration of said regulating means.
grinding zone in a lower portion thereof comprise
7. In combination with an air~swept pulverizer 10 ing an annular grinding surface together with
having separate inlets for fuel and air and hav
a circular row of reliable grinding elements co
ing an outlet for pulverized fuel mingled with said ~
operating with said surface, means for feeding
air, a continuous conduit having one end con
material to be pulverized to said grinding zone
nected to said pulverizer outlet and its opposite
from above, means forming an annular throat
end connected to said inlet for air, means for
passage marginally of said grinding surface for
supplying fuel to said pulverizer, means for with
admitting air into proximity with said grinding
drawing a portion of said fuel-air mixture from
zone from below, means for maintaining an up
said conduit, means for measuring the rate at
ward current of air through said throat passage
which the remaining portion of said mixture is
for discharging from said pulverizer a ?uent mix
returned to said pulverizer air inlet through said 20 ture comprising pulverized material suspended
opposite conduit ’end, and means controlled by
in said air, a main conduit having its opposite
said last named means for regulating the rate at
ends open to the interior of said pulverizer above
which fuel is supplied to said pulverizer.
and below said annular throat passage, said con
8.. In an air-swept conduit system including a
duit forming with said pulverizer a closed cir
pulverizer, wherein a portion of the mixture of
culating path for a portion of the total mixture
pulverized material and carrier air discharged
initially discharged from said pulverizer, means
from the pulverizer is withdrawn from said sys
for regulating the rate at which said material
tem and a remaining portion of said mixture is
is fed to said grinding zone comprising means
returned to said system for recycling through
responsive to therate of air delivery to said an
said pulverizer, the method of controlling the 30 nular throat passage relative to the rate of ?uid
operation of said pulverizer at varying capacities
flow through a predetermined portion of said
which comprises feeding material to be pulver
pulverizer inclusive of said annular throat pas
ized to said pulverizer, supplying carrier air to
sage, and means for rendering said regulating
said pulverizer, each from a source outside said
system, measuring in terms of differential pres
sure the rate at which carrier air is supplied to
35
means operative in accordance with the rate at
which said portion of said output mixture is re_
turned to said pulverizer.
said pulverizer, measuring in terms of differen
12. In combination with a pulverizer having a
tial pressure the rate of fluid flow through said
grinding zone in a lower portion thereof wherein
.pulverizer, measuring in terms of differential
a reserve of material in the process of pulveriza
pressure the rate at which pulverized material 40 tion is maintained during normal operation, said
and carrier air are returned to the pulverizer, and
grinding zone being de?ned by upper and lower
regulating the rate at which material to be pul
grinding rings and a circular series of metal
verized is fed to the pulverizer in accordance with
balls operating therebetween, means for feeding
the resulting three measures of differential pres
material to be pulverized to said pulverizer above
sure.’
said grinding zone, means forming an annular
9. In a system of the class described, an air
throat passage interiorly of said lower ring for
swept ‘pulverizer arranged to discharge a ?uent
admitting air to said grinding zone from below.
mixture of pulverized fuel suspended in air,
means for maintaining an upward current of air
means for supplying fuel to said pulverizer,
through said throat passage and grinding zone
means for returning a portion of said mixture to 50 for discharging from said pulverizer a ?uent mix
said pulverizer and for mingling said portion with
ture comprising pulverized material suspended
air supplied to said pulverizer, means for measur
in said air, a main conduit having its opposite
ing the rate of air flow to the pulverizer, means
ends open to the interior of said pulverizer at the
for measuring the differential pressure across a
upper and lower sides of said grinding zone, said
conduit forming with said pulverizer a closed cir
for measuring the rate at Which said portion of
culating path for at least a portion of the total
the mixture is returned to the pulverizer, and
mixture initially discharged from said pulver
means conjointly responsive to said three named
izer, means for measuring in terms of differential
measuring meansfor regulation the rate at which
pressure the rate at which air is delivered to
60
fuel is supplied to saidpulverizer.
~
said throat passage, means for measuring in
10. In combination with an air-swept pulver
terms of di?erential pressure the rate of ?uid
izer arranged to discharge a ?uent mixture of
flow through a predetermined portion of said pul
pulverized material suspended in a stream of car
verizer including said throat passage and said
rier air, means for supplying material to be pul
grinding zone, means for measuring in terms of
verized to said ‘pulverizer, means for returning
differential pressure the rate of ?ow of the por
a mixture of pulverized material and air to said
tion of said mixture being returned to said pul
pulverizer at a rate less than the rate at which
verizer, and means rendered operative in re
predetermined ‘portion of said pulverizer, means ‘
said initial mixture of pulverizable material and
carrier air is discharged from the pulverizer,
means for measuring the rate of flow of carrier
air to said pulverizer, means for measuring the
di?erential pressure across a predetermined por
sponse to said three named measuring means
acting jointly for controlling the rate at which
material to be pulverized is fed to said pulverizer.
JAMES L. HARVEY.
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