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Патент USA US3091453

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May 28, 1933
J. H. HERZ ETAL.
KILN AUTOMATIC CONTROL METHOD AND APPARATUS
fia.IlLaVP
lo.
3,091,443
May 28, 1963
J. H. HERZ ETAL
3,091,443
KILN AUTOMATIC CONTROL METHOD AND APPARATUS
Filed April 17. 1961
2 Sheets-Shea t 2
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INVENTORS
H. HERZ
ROMIG
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f.
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ATTORNEYS
United States Patent O "ice
2
1
3,091,443
KILN AUTOMATIC CONTROL METHOD
AND APPARATUS
3,091,443
Patented May 28, 1963
pilot fuel correction values are obtained and combined
for controlling the rate of flow of pilot fuel used to sec
ondarily preheat the intake air.
Referring first to FIG. l, a rotary kiln is generally indi
Joseph H. Herz, Redlands, and John R. Romìg, Rialto, 5 cated at 10 as having elongated tubular shape and as
Calif., assignors to California Portland Cement Co.,
being inclined from the horizontal. Raw materials are
Los Angeles, Calif., a corporation of California
fed at 11 into the upstream open end 12 of the kiln which
Filed Apr. 17, 1961, Ser. No. 115,058
projects into `a housing 13. The raw materials, which
23 Claims. (Cl. 263-32)
typically contain Si02, Al203, FeZOB, CaCo3, MgCo3,
This invention relates generally to improvements in the
kiln treatment of calcareous materials, and more par
NazO and KZO in correct proportions to produce Port
land Cement, travel lengthwise downstream through the
kiln, principally in response to rotation thereof, which
ticularly concerns process and apparatus for increasing
may be etîected by any suitable means such as is gen
the efficiency of kiln operation.
erally indicated at 14. Furthermore, the kiln rotary
In our copending application entitled “Kiln Control
speed may be controlled as desired, and in the past it
Method and Apparatus,” Serial No. 95,697, ñled March
has been generally the practice to attempt to `control ma
14, 1961, we have described the control of fuel combus
terials ñow within the kiln by changing the speed of kiln
tion within a kiln, as by controlled pre-heating of intake
rotation.
air, all for the purpose of favorably modifying or elimi
After passing downstream through the kiln, the ma
nating adverse elfects upon kiln operation which might
otherwise result from uncontrolled variable preheating of 20 terials discharge as clinker shown dropping at 1S within
hood 16 into which the open downstream end `17 of the
the lair supply, or from perturbations in the llow of ma`
kiln projects. The clinker falls downwardly upon a grate
rterial being treated in the kiln, or from both of these
means 18, where the clinker is retained in heat transfer
variables. One advantageous method of controlling such
relation with intake air streams moving upwardly as indi
combustion as described in said application is to add
cated at 19 and 2G and through the clinker bed 21. It
variable amounts of heat to the intake air previously
will be understood that the clinker bed slowly travels
preheated by passage in heat transfer relation with the
along the length of the grate 18, which may be moved
clinker discharge from the kiln.
as by means of the drive generally shown at 22. The
As will -be seen, the present invention in its several
aspects goes beyond that which was described in our
grate 18 and clinlcer bed 21 are confined within a clinker
ature of the air stream, as sensed before and after sec
of the grate in response to operation of the drive means
ondary preheating, and for fluctuations in the materials
temperature within a selected region of the kiln wherein
30, a ycoupling 31, another shaft 32 for driving the crank
prior application. In one broad respect, the improved 30 cooler housing 23 having an entrance at 24 for air de
livered through duct 25, a stack 26 remote from the hood
method contemplates the steps that include secondarily
16, and a clinker discharge outlet 27. Merely for pur
preheating intake air that has been primarily preheated
poses of illustration, the grate 18 is shown as supported
as by the hot clinker, and adjusting such secondary heat
on pivoted links 28 accommodating arcuate movement
ing to compensate for fluctuations in the preheat temper
the materials have near maximum temperature, thereby
to achieve less variable heat treatment of materials in the
22.
The latter may include a motor 29 having a shaft
3‘3, »and a link 34 connected between the crank and the
More specifically, secondary preheating is typically
grate. Also, the air duct 25 is shown as supplied with
air by a suitable blower 3S through a damper 36.
ln operation, air delivered through the duct 25 passes
upwardly through the clinker bed 21 for the purpose of
adjusted by varying the amount of pilot fuel burned to
preheating the air and cooling the clinker, following
secondarily preheat the intake air, the adjustment being
which the air flows upwardly through the hood 16 and
into the downstream end of the kiln. Fuel is delivered
to the downstream end of the kiln through a nozzle 37,
the fuel becoming ignited for combustion with the air
oxygen at a point 38. The fuel which may comprise
natural gas, oil, powdered coal, or any suitable ñowable
kiln through controlling the location of fuel combustion
with preheated air in the kiln.
made in accordance with the sum of two pilot fuel cor
rection values. The first of these correction values cor
responds, or is proportionally related, to the amount of
fuel being delivered at the main burner for burning in
the kiln, and also to the difference between the primarily
preheated intake air stream temperatures sensed before
secondary preheating and a fixed or desired secondary
preheat temperature. The second of these correction
values corresponds, or is proportionally related, to the
difference between the maximum temperature of the
materials within the kiln and ya predetermined desired ma
terials maximum temperature.
In its apparatus aspects, the invention contemplates
the provision of means, including temperature and fuel
flow rate sensors, for obtaining these ñrst and second
correction values and «then for using them to control the
rate of pilot fuel delivery, as will be described.
These and other objects and advantages of the inven
combustible, is typically supplied to the nozzle 37 through
a `conduit 39. If natural gas is used, it may be supplied
through an auxiliary line 40 into which a valve 41 and
orifice meter 42 are connected. If oil or powdered coke
or coal are used, they may be supplied to line 39 through
suitable inlets, and primary air may be delivered to the
conduit 39 through a line 43 into which a valve 44 is
connected, a suitable blower 45 being shown for de
livering primary air at desired pressure and volume to
the conduit 39.
Means for secondaríly preheating the intake air, which
may take different forms, is shown in one of its forms
at 50 in the throat region of the clinker cooler so as to
be directly in the path of the preheated yair stream flow
will he more fully understood from the following detailed 65 ing to the downstream end of the kiln. While the heater
description of the drawings, in which:
may take different forms, it is shown in FIG. l merely
tion, as well as the details of an illustrative embodiment,
FIG. l is a vertical section through a kiln system show
ing the «apparatus by which the improvements may be
for purposes of illustration as a gas burner to which gas
is supplied through a line S1 in which an orifice meter
52 is connected for metering measurement purposes.
FIG. 2 is a fragmentary elevation showing a modifica 70 As shown, line 51 may be supplied by either of lines 53
and 54, line 53 delivering a side stream of gas from
tion of the apparatus; ‘and
the main conduit 39 and through a control valve 55, and
FIG. 3 is a «How diagram showing the manner in which
effected;
3,091,443
4
3
line 54 delivering an independent side stream of gas
through a control valve 56, the latter being preferred.
The purpose of the heater 50 is to controllably and
additionally heat the incoming or secondary air prior to
combustion of the main fuel stream in the kiln, thereby
to control or adjust the combustion within the kiln to
vary the regional location lengthwise of the kiln at which
the hot gas reaches temperatures in excess of the ma
terials maximum temperature. As a result, the temper
ature and the movement of the materials in the kiln may
be controlled, and particularly that movement of ma
terials associated with fluidization thereof in the critical
zone generally shown at 57 in FIG. 1.
and the heat level in the ñuidization zone 57 of the kiln
is increased, which tends to produce 'a further increase in
the rate of ñow of materials from and through the ñuid
ization zone.
lf these chain reactions are not suitably
dealt with, there results what is commonly known as the
“loss of the kiln.”
In accordance with the invention, the combustion of
the fuel with the incoming air is adjusted to vary the
heat transfer in the kiln in such manner as to counter
the ampliñed tendency for materials to move at faster or
slower rates through the critical zone, and specifically, the
combustion is ‘adjusted to effect a downstream or up
stream displacement of the ignition point 38. This ad
In accordance with the invention, it is contemplated
justment also effects a downstream or upstream displace
that equilibrium conditions may be produced and main
ment of the regional location lengthwise of the kiln at
tained to best advantage, and with least deviation from
which the hot gas reaches temperatures in excess of the
optimum, by maintaining the speed of kiln rotation sub
materials maximum temperature TSM.
stantially constant during the adjustment of flaming com~
More specifically, the combustion is adjusted by effect
bustion, ‘by maintaining the llowage of the main stream
ing an increase or decrease in the temperature of air
of fuel into the kiln substantially constant while the flow 20 passing into the kiln, as by controlling the amount of
age of th-e side stream of fuel through line 51 is in
fuel passing to line 51 and delivered to the auxiliary
creased or decreased as required, by maintaining the
burner 50. To accomplish this, the means for elïecting
same ñow rate of raw materials into the kiln at 11, and
a displacement of the combustion ignition point typically
by maintaining essentially the same volumetric flow of
includes temperature sensing apparatus for sensing
air into the clinker cooler through the conduit 25, for 25 changes in the nature of fluctuations or excursions,
preheating and ultimate iiow to the kiln. Such primary
in the downstream materials temperature conditions in
preheating of the air by the clinker is such as to raise
the kiln causatively related to the ampliñed tendency for
the temperature of the air above 1000“ F. prior to the
materials to move within the zone 57. Such temperature
increased or decreased secondary preheating elïect ac
sensing apparatus may include a temperature sensing
complished by operation of the auxiliary burner S0. 30 device 64, `as for example a pyrometer, or Rayotube, or
Furthermore, under equilibrium conditions it is desirable
light pipe -directed to receive rays 65 emanating from area
that the primary preheating of the air by the clinker be
157 at or near the maximum solids temperature TSM.
stabilized as respects the temperature of the ai1- tiowing
The variable signal from the sensor l64 is conducted
upwardly from the clinker bed, whereby the auxiliary or
by line 67 to a device 68 also having a constant signal
secondary heater S0 may be operated in part as a fine 35 input at 69 representing a predetermined desired maxi
`temperature control to smooth out any tiuctuations in air
mum materials temperature T'SM. The output 170 of
temperature.
the device 68 represents the difference between the tIwo
For purposes of achieving primary stabilization of the
inputs, or ATSM which is indicated on a suitable meter
air preheat temperature, the movement of grate 18 may 40 66. Thus, the device 68 functions to compare or alge
be varied in response to pressure changes of secondary
braically add the two inputs, and it may take many dif
air, as for example as shown in FIG. 1.
Thus, a pres
sure sensing device 58 may be located beneath the grate
18 and the pressure conditions may be viewed on a meter
or instrument 59. Also, the speed of grate movement
may be controlled by a magnetic clutch 31 in the drive
22, or an equivalent device, the energization of the clutch
being controlled electrically as by the rheostat 60. Ac
cordingly, the operator may control the rheostat and thus
the drive to decrease or increase the speed of grate move
ment in response to a decrease or increase respectively
in the secondary air pressure, ias measured before the air
passes through the clinker received on the grate. In this
connection, it will be understood that a stable preheat
`temperature of the air passing through the clinker bed is
associated with a stable thickness. lf for any reason
there should occur an increased discharge of clinker from
the kiln, this change will result in a changed pressure as
measured by the device 58 so that the operator may then
adjust the grate drive in such manner as to adjust the
bed thickness to reestablish the desired pressure, to which
the desired stabilized preheat temperatures are related.
It will be understood that local changes in the down
stream movement of materials in the kiln in response to
ñuidization within the ‘critical zone shown lat 57 in FIG.
ferent physical forms, depending on the mechanical, hy
dnaulic, pneumatic, electrical, o1' optical nature of the
inputs and output desired. For example, in the case of
electrical inputs, the device may comprise a Wheatstone
bridge or a potentiometer; and in the case of pneumatic
or gas pressure inputs varying with temperature, the de
vice 68 may comprise a pair of Bourdon gauges, one for
each input, and interconnected in opposition.
The means for elfecting a displacement of the com
bustion ignition point also includes temperature sensor
70 located in the intake air stream to measure changes,
in the nature of ñuctuations or excursions, in the tem
perature T’As. The latter represents the temperature of
the air after it has been primarily preheated as by the
clinker bed, but before secondary preheating as by com
bustion of pilot fuel at 50. A temperature T’AS on the
other hand is the desired temperature of the air stream
after secondary preheating, when ATSM is equal to zero.
An adjustable signal generator is shown at 7l for gener
ating a signal representing TAS.
The variable signal from the sensor 70, and the fixed
signal from manual input 71 are conducted by input lines
72 and 73 to a device 74 having an output at 75 repre
senting `the difference `between the two inputs, or ATAS
l, tend to disturb the heat transfer conditions within the
which is indicated on a suitable meter. Thus, the device
kiln in such manner as to amplify the tendency for ma
74 functions to compare or algebraically add the two
terials to so move. For example, an observed increase
inputs, and it may take many different physical forms
in the rate of movement of materials through the Huid
depending on the mechanical, hydraulic, pneumatic, elec
ization zone and toward the downstream end of `the kiln
70 tric, or optical nature of the inputs and outputs desired,
results in the lowering of the total heat level in the exo
in the same manner as discussed above in connection
thermic area 157, which thereby causes a later fuel ig
with device 68.
minion, i.e. a shifting of the ignition point 38 further from
Referring to FIG. 3, the correction to be applied to
the pilot fuel valve 56 may be represented by the symbol
in the physical lengthening of the tip of the ñame 62, 75 MN? which is the sum of first and second correction
the downstream end 17 of the kiln. This in turn results
3,091,443
values M'NP and AMNP respectively. The iirst correction
references being publications of the McGraw Hill Book
value M’NP may be considered as compensating for varia
tions or ñuctuations in the temperature difference ATAS
Company.
according to the equation:
combustion B.t.u. addition to the air outside the kiln to
be used, is substantially less than 50% of the rate of main
fuel combustion B.t.u. addition to the air. Thus, the
Generally speaking, the maximum rate of pilot fuel
where
temperature of air already heated by clinker outside the
kiln need be increased or decreased typically but not
M’Np=pound mols/second of fuel to be used for T'As
necessarily by less than 200° F. to achieve desired com
correction.
K1=expcrimentally determined constant for any particu 10 bustion control in the kiln, wherein gas temperatures will
exceed 3000° F. following main fuel combustion in the
kiln.
Kiln operators may themselves become skilled in ad
perature of the air stream, and the primarily preheated
justing the pilot fuel valve 56 in response to observation
air stream temperatures as sensed (ATAS=T'AS-T'AS
15 of the meters 66 and 90, the former recording the tem
in ° R or ° F.)
lar kiln process
ATAs=difference between a predetermined desired tem
perature difference ATMs and the latter recording the
temperature difference ATAS for the purpose of varying
MNB=pound mois/second of fuel being delivered at the
main burner for burning in the kiln
the pilot fuel to achieve less variable heat treatment of
Accordingly, if the fuel delivery to the main burner
the materials in the kiln, and particuiarly in the region
MNB remains constant, then M'Np varies directly as 20 57. For example, if both of the temperature differences
ATSM and ATAS are increasing, the operator will open
ATAB.
The second correction value AMNp may be considered
the valve ‘56 to admit more pilot fuel to burner 50, for
eiîecting increased heating of the intake air.
as compensating for variations or perturbations in the
temperature difference ATSM yaccording to the equation:
where
AMNP=K2XATSM
(2)
Actual operation of a cement kiln according to these
25 principles has been found to bc entirely successful and
to eliminate for all practical purposes conditions other
wise leading to the “loss of the kiln.”
FIG. 2 shows an alternative placement of the pilot
MNp=pound mals/second of fuel to be added or sub
burner 9S within a duct 96 conveying a side stream of
tracted for TSM correction.
30 air into the hood 16 to mix with the main intake air
K2=-experimentally determined constant for any partic
stream flowing upwardly toward the downstream end
ular kiln process
of the kiln.
ATsM=diiïerence between a predetermined desired ma
The more generalized correction values M 'NP andAMNp
terials maximum temperature, and the maximum tem
perature of the materials Within the kiln as sensed 35 are defined according to the following equations, which
hold for any kiln and cooler system using natural gas as
(ATSM=TISM-TSM in o R 0I' o F.)
fuel.
The constants K1 and K2 in the above two equations
@sigan-@iw
11-01 (Tis-56mm#
may be obtained experimentally by operating any given
kiln by trial `and error to achieve equilibrium, and noting
40
the correspondence between -the value MNP or the amount
of correction fuel to the pilot burner needed to reestab
AS
where
lish equilibrium of TSM and the values ATAS and ATSM.
M'Np--pound mols/second of fuel to be used for T'AS
Once these constants are determined with acceptable ac
correction.
curacy, they may be combined in multiplying relation
with the other values on the right hand sides of Equations 45 ÑGOzaverage pound mois/second of fuel plus air de
l and 2, as by suitable devices indicated at 76, 77 and
78 in FIG. 3, to obtain the pilot fuel correction values
livered to kiln system, and comprising the sum
Ñorl‘îoß
ïïspzaverage pound mols/second of pilot burner fuel
flow plus equivalent air for its complete combustion
76, 77 and 78 are Well known, and they are shown in
block form as indicative of any mechanical, hydraulic, 50 EÍGB=average pound mols/second of main fuel flow
pneumatic, electric or optical device of this ‘type which
pius equivalent air to the kiln
will perform the desired multiplying functions. Device
T’A5=average desired air temperature in degrees Rankine,
76 multiplies inputs K2 and ATSM to produce output
when ATSM=zero
AMNP; and device 77 multiplies inputs K1 and ATAS to 55 T’AS=average temperature in degrees Rankine of said
produce an output which is in turn multiplied by input
primarily preheated air
MNB in device 718 to produce output M'NP.
FAS-:fractional percent of total combustion air ñow orig
The tlwo outputs M’Np and AMNP are subsequently
inating as said preheated air stream ilow
AMM; and M'Np. Analog computing devices of the type
fed to device 80 which adds them and produces the cor
0.001 sie nu rm
rection value MNP which may be fed through ratio and 60
62s3+u1969TN+ 1.9686 (FASTASJVFAHTAH)
`bias devices 81 and 82 to a controller 83 for the valve
56. Such devices as 80 through 83 are well known, and
are shown in block form as indicative of iany mechanical,
(4)
where
hydraulic, pneumatic, electrical, or optical devices which
AMNP=pound mois/second of fuel to be added to or
will perform the referred-to functions.
65
subtracted for TSM correction
Conventional subtracting and adding instruments 68,
D=kiln diameter, in feet, inside the coating of zone 157
‘74 and 80, and multiplying instruments 76, 77 and 78 are
described in technical information bulletins 39-163a
ATSM=diiference between a predetermined desired ma
and 39-l64a published in 1960 by The Foxboro Com
terials maximum temperature, and the maximum tem
pany, Foxboro, Massachusetts. Ratio instrument $1 may 70
perature of the materials within the kiln as sensed
be a potentiometer, and device 82 a signal amplifier.
(ATSMIT’SM-TSM in o R 0I' n F.)
These elements are also disclosed in “Analog Method in
TN=temperature in degrees Rankine of fuel supplied to
Computations and Simulations” by Walter W. Soroka
kiln
(published 1954), and “Analog Computation” by George
Fgs=fractional percent of total combination air íiow
W. Smith and Roger C. Wood (published 1959), both 75
originating as said preheated air stream flow
3,091,443
7
temperatures, ATSM; temperature of the natural gas, TN;
T’As=average desired temperature in degrees Rankine
of said primarily preheated stream if ATSM=zero
temperature of the cooler air as it enters the kiln, "Í'As',
temperature of the ambient air as it enters the system,
FA11=fractional percent of total combustion air ñow
originating from sources other than said preheated air
TAH; fraction of total air coming from the cooler, (FAS);
and fraction of total air resulting from ambient hood
stream flow
TAHzinitial average temperature in degrees Rankine of
leakage, (FAH). The factors 0.0001946, 6283, 0.1969
combustion air originating from sources other than said
preheated air stream flow
Equation 1 is a simplified and specialized version of the
generalized Equation 3, the derivation of the latter being
predicated on the requirement of keeping the kiln inlet
air stream constant at the pre-selected temperature T'AS.
M'Np represents the necessary B.t.u. to accomplish this
purpose. Controlling factors include: total gas plus 15
and 1,9686 in Equation 4 lare constants of derivation
adjusting for units of measurement.
In a typical computation involving use of Equation 4
equivalent air, (ÑGO); main burner gas plus equivalent
4 results in
0.001946( 9) (9 ) X ATSM
6283 -I- .1969(500) -i- 1.9686[.95(1960) + .05( 540)]
air, (ÑGB); actual temperature of air from cooler before
secondary heating, (T'AS); fraction of total air coming
from cooler, (FAS); desired temperature of air from
cooler ‘after secondary heating by pilot, (T'As); and the 20
mol. ratio of natural gas plus theoretical air per mol.
natural gas, which equals 11.01 for most natural gas.
which reduces to:
AMNP:0.O00O l X ATSM
The latter is equivalent to Equation 2 where K2 is
now equal to 0.0000156 for this special application.
This manner of approximating the factor K.; has been
The factors 560 and 54,900 are constants or derivation
adjusting for units of measurement.
In `a. typical computation involving use of Equation 3
to derive K1 of Equation l, the desired average pilot
natural gas plus equivalent air flow (ÑGP) might be 1.5
percent of the total average natural gas plus equivalent
air flow (B_ÍGO). Therefore, since ÑGO=ÍIGP+ÑGB it
follows that 3761;:0985 117Go, or ZI'ÍGO=1.015 ÍLTGB.
Also, the normal average T'As equals l860° Rankine
(1400” F.), the desired average T'AS equals l960°
Rankine (1500° F.) and the estimated FAS might be
0.95. Incorporation of these values in Equation 3 results
to derive K2 of Equation 2, D might be 9 feet', TN might
be 500° Rankine (40° F.); FAS might be 0.95 (esti
mated); FAH might be 0.05 (estimated); TAH might be
540° Rankine (80° F.); and T’AS might be 1960 Rankine
(l500° F). Incorporation of these values in Equation
found sufficiently accurate to allow automatic kiln oper
ation, and values for K2 above and below the derived
value may be tried `to determine the exact value best
suited for the kiln in question.
0
We claim:
l. In the process wherein materials flowing in a kiln
are heated to high temperature necessary to production
of a desired product, the steps that include flowing an
air stream in combustion relation with main fuel to pro
duce hot gas fiowing in the kiln to heat the materials
in:
therein, effecting primary and secondary preheating of
air forming said stream and prior to use of the air for
main fuel combustion, whereby air temperature fluctu
.
40
which reduces to:
Tis-_569 + 560
Affen: HGB( 1015K,”
14,313+57,7s9
which for all practical purposes for the kiln used in the
example can be written:
juive: ÑGB( Tris _ gils)
72,102
The natural gas fuel being used requires 10.01 pound
mols of ‘air per pound mol of fuel, and thus
Therefore,
BMP:
72,102
ations result from said primary preheating, the materials
within a predetermined region of the kiln having ma
»terials temperature fluctuations, said air and materials
temperature fluctuations having an ultimately adverse
effect upon the heating of said materials to said high
temperature, said secondary preheating being effected by
combustion of auxiliary fuel for heating air flowing to
the kiln, obtaining correction values corresponding to said
`air and materials temperature fluctuations, and using said
values to control said secondary preheating to counter
said adverse effect on the heating of said materials to said
high temperature.
2. In a cement making process wherein materials flow
ing downstream in a kiln are heated to high temperature
necessary to the production of a desired quality clinker
product, the steps that include flowing an air stream in
55 combustion relation with main fuel to produce hot gas
flowing upstream in the kiln to heat the materials there
in, effecting primary and secondary preheating of air
forming said stream and prior to use of the air for main
fuel
combustion, whereby air temperature excursions re
which is equivalent to Equation l where K1=0.000153.
sult from said primary preheating, the materials within
This manner of approximating the factor K1 has been
a predetermined region of the kiln having materials tem
found sufficiently accurate to allow automatic kiln oper
perature
excursions, said air and materials temperature
ation. Values for K1 above and below this value derived
excursions having an ultimately adverse effect upon the
from Equation 3 may be tried to determine the exact
heating of said materials to said high temperature where
value of K1 most suited to the kiln in question.
65 by the clinker product deviates from desired quality, ob
Equation 2 is a simplified and specialized version of
taining first correction values corresponding to excursions
the generalized Equation 4. The derivation of the latter
in the primary preheated air temperature, obtaining sec
is predicated on the requirement of maintaining the tem
ond correction values corresponding to excursions in the
perature of the combusting gas and air stream equal to
temperature of the materials in said predetermined region
the maximum solids temperature at the exact physical
of the kiln, and using said first and second correction
position in the kiln Where the maximum solids temper
values for controlling said secondary preheating to
ature is achieved. AMNP represents the necessary B.t.u.
to accomplish this purpose. Controlling factors are:
counter said adverse eñect on the heating of said ma
terials to said high temperature.
kiln diameter inside the burning zone coating (D); dif
3. The invention as defined in claim 2 in which said
ference between desired and measured maximum solids 75
3,091,443
‘9
10
'secondary preheating is effected by combustion of aux
iliary fuel in the air stream fiowing to the kiln.
MGBzaverage pound mols/ second of main fuel fiow plus
equivalent air to the kiln
T’AS=average desired temperature in degrees Rankine
of said secondarily preheated air when ATsM=zcro
FA5=fractionfal percent of total combustion air flow
4. The invention as defined in claim 3 in which the
>rightaining of said first correction values includes sensing
the temperature of said primarily preheated air stream
before secondary preheating thereof.
originating as said preheated air stream flow
5. The invention -as defined in claim 4 in which the
obtaining of said second correction values includes sens~
ing the actual temperature of' the materials within said
predetermined region of the kiln.
T'Ag=average temperature in degrees Rankine of said
primarily preheated air
10
13. The invention as defined in claim 12 in which said
6. The invention as defined in claim 5 in which the
obtaining of said second correction values includes com
second correction value is effectively determined sub
stanti'ally in accordance with the equation:
paring the materials temperature actually sensed and a
AMNP: 6283+().1969 0.001946D2Tm
TN +1.9686(F„TÁ5+ FAHTAB
predetermined desired materials temperature.
7. The invention as defined in clahn 6 in which the 15
obtaining of said primary correction values includes com
paring primarily preheated air temperatures and a pre
determined desired air temperature.
where
AMNp=pound mols/second of fuel to be added to or
subtracted for TSM correction
D=kiln diameter, in feet, inside the coating of zone 157
8. The invention as defined in claim 5 in which said
materials within said predetermined region of the kiln 20 ATSM=difference between a predetermined desired ma
have temperatures proximate the maximum materials
terials maximum temperature, and the maximum tem
temperature in the kiln.
perature of the materials within the kiln as sensed
9. The invention as defined in claim 2 in which said
TNztemperature in degrees Rankine of fuel supplied to
ûrst correction value is effectively determined substan
25
tially in accordance with the equation:
kiln
FAS=fractional percent of total combination air :Elow
originating as said preheated airstream flow
T’AS=average desired temperature in degrees Rankine
M’N-P=pound mois/second of fuel to be used for T’As
of said primarily preheated stream if ATSM=zero
correction
30 FAH=fractional percent of total combustion air flow
K1=experimentally determined constant for any paroriginating from sources other than said preheated air
ticular kiln process
stream flow
ATAszdiiïerence between a predetermined desired tern
TAH=initial average temperature in degrees Rankine of
penature of the air stream, and the primarily preheated
combustion air originating from sources other than said
air stream temperatures as sensed (ATAS=T’¿B-T'Ag 35
preheated air stream fiow
in ° R or ° F.)
14. The invention as defined in claim 11 in which the
use of said first and second correction values includes
effectively adding them to derive a resultant correction
MNB=pound mols/second of fuel being deiivered for
burning in the kiln at the main burner
10. The invention as defined in claim 9 in which said 40 value »to be used in controling said adjustment of said
second correction value is effectively determined sub
secondary preheating.
stantialiy in accordance with the equation
15. In the process wherein materials are subjected to
treatment with hot gas flowing upstream in a kiln, hot
AMNPZKg X ATSM
gas `being produced upon burning of fuel in the kiln, and
where
45 in a stream of air primarily preheated to variable pre
AMNp=pound mols/ second »of fuel to be added or sub
healt temperature outside the kiln, variation in said pri
tracted for TSM correction
mary preheat temperature being characterized as ulti
K2=experimentally determined constant for any par
mately adversely afiecting said materials treatment, the
ticular kiln process
steps that include secondarily preheating air in said stream
ATsM=difference between a predetermined desired ma 50 prior to burning of said fuel therein, obtaining certain
terials maximum temperature, and the maximum tem
correction vaines corresponding to changes «in the pri
perature of the materials within the kiln as sensed
mary preheat temperature of said stream, and using said
correction values to control `adjustment of said secondary
(ATSM2T’sM--TSM in o R Ol' o F.)
preheating to compensate for said changes so as to coun
11. The invention as defined in claim 10 in which the 55 ter said adverse effect on materials treatment, said cor
use of said first and second correction values includes
rection values being determined substantially in accord
effectively ladding them to derive a resultant correction
ance with the equation:
value to be be used in controlling said adjustment of
said secondary preheating.
l2. The invention as defined in claim 2 in which said 60 where
first correction value is effectively determined substan
tially in accordance with the equation:
M'NP=pound mals/second of fuel to be used for T’As
correction
K1=experimentally determined constant for any partic
M,NP _Uw( Tis- 560) -Ñcä Tis- 560)
11.01( Tg5-5603+@
AB
M'NP=K1XATAsXMma
65
ular kiln process
ATAS=difierence between a predetermined desired tem
where
perature of the air stream, and the primarily preheated
air stream temperatures as sensed (ATAs=T'AS-T’As
M'm=pound mole/second of fuel to be used for T’AS
in ° R or ° F.)
correction
MNB=pound mois/second of fuel being delivered for
70
burning in the kiln at the main burner.
MG0=average pound mois/second of fuel plus air de
livered to kiln system, and comprising the sum,
16. In the process wherein materials are subjected to
Eend-Mon
treatment with hot gas flowing upstream in a kiln, hot
Mgp=average pound mols/second of pilot burner fuel
gas being produced upon burning of fuel in the kiln and
flow plus equivalent air for its complete combustion 75 in a stream of air primarily preheated outside ythe kiln,
3,091,443
11
12
19. The invention as defined in claim 18 in which said
means for obtaining said lirst correction values includes
a temperature sensor for sensing the temperature of the
air stream before said secondary preheating and ap
paratus .to compare said sensed air stream temperature
with a predetermined air stream temperature desired after
said secondary preheating, and said means for obtaining
said second correction values includes another temper
ature sensor for sensing the actual maximum temper
ature of the materials undergoing exothermic reaction in
pensate for said changes so as to counter said adverse
the kiln and apparatus to compare said actual maximum
effect upon the materials treatment, said correction values
temperature of the materials with a predetermined desired
`being determined substantially in accordance with the
materials maximum temperature.
equation:
20. The invention as defined in claim 18 in which said
AMNP=K2 X ATSM
15 means for utilizing said Iirst and second correction values
where
has an output proportional to the sum of said values, and
AMNP=pound mols/second of fuel to be added or sub
including an actuator responsive to said output for con
traoted for TSM correction
trolling said secondary preheating.
K2=experimentally determined constant for any particu
21. The invention as defined in claim 20 in which said
lar kiln process
20 means for secondarily preheating air includes pilot fuel
ATSM=di?ference -‘between a predetermined desired tem
burner means for heating the air stream outside the kiln,
perature of the air stream, and the primarily preheated
and including a valve controlled by said actuator for
air stream temperature as sensed (ATA5=`T'As--T'AS
regulating fuel delivery to said pilot fuel burner means.
in ° R or ° F.).
22. The invention as defined in claim 18 in which said
17. In combination with apparatus including a kiln 25 means for obtaining said first correction values has an
output which varies directly as the quantity M’NP in thc
and wherein materials are formed into clinker by treat
equation:
ment with hot gas ñowing upstream in the kiln, the
M'NPZKiXATAsXMNB
`materials undergoing calcirration, liuidization and exo
where
thermic reaction while they move downstream through
different zones in the kiln and means for passing an air 30 M’Np=pound mols/ second of fuel to be used for T'As
stream and fuel into the -kiln for combustion therein and
correction
for upstream hot gaseous flow in heat transfer relation
Kj=experimentally determined constant for any particu
with materials in the kiln, said air being primarily pre
lar kiln process
heated 4outside the kiln, ‘the improvement comprising
between a predetermined desired tcm
means for secondarily preheating air in said stream prior 35 ATAS=diiìerence
perature of `the air stream, and the primarily preheated
to combustion with said fuel, and means for adjusting
air stream temperatures as sensed (ATAs=`T'A5-T'As
said secondary preheating to compensate for fluctuations
in ° R or ° F.)
in both the preheat temperature of the air stream and
the temperature of materials undergoing exothermic re 40 MNB=pound mols/second of fuel being delivered for
burning in the kiln at the main burner.
action in the kiln thereby to achieve less variable heat
treatment of the materials in the kiln.
23. The invention as delined in claim 18 in which said
18. In combination with apparatus including a kiln and
means for obtaining «said second correction values has
wherein materials are formed into clinker by treatment
an output 4which varies directly as the quantity AMNP
the materials within a predetermined region of the kiln
being subject to materials temperature iluctuations char
acterized as ultimately adversely affecting said materials
treatment, the steps that include secondarily preheating
fair in said stream prior to burning of said fuel therein,
obtaining correction values corresponding to changes in
the materials temperature within said predetermined
region of the kiln, and using said correction values to
control adjustment of said secondary preheating to com
with hot gas liowing upstream in the kiln, the materials 45 in the equation:
undergoing calcination, fluidization and exothermic re
action while they move downstream through different
where
AMNP=K2XATSM
zones in the kiln, and means for passing an 4air stream
AMNPzpound mols/second of fuel to be added or sub
and fuel into the kiln for combustion therein and for
tracted for TSM correction
upstream hot gaseous flow in heat transfer relation with 50
K2=experimentally determined constant for any partic
materials in the kiln, said air being primarily preheated
ular kiln process
outside the kiln, the improvement comprising means for
ATsM=dilïerence between a predetermined desired ma
secondarily prt-.heating air in said stream prior to corn
terials maximum temperature, and the maximum tem
«bustion with said fuel, means for obtaining first correc
perature of the materials within the kiln as sensed
tion values corresponding to changes in the preheat tem 55
(ATSMZT’sM-TSM in o R 0l' u 13.).
perature of said stream, `means for obtaining second cor
rection values corresponding to changes in the temper
References Cited in the file of this patent
ature of materials undergoing exothermic reaction in the
kiln, and means for utilizing said first and second cor
UNITED STATES PATENTS
rection values to control adjustment of said secondary 60 2,068,574
Smith ______________ __ Jan. 19, 1937
preheating thereby to achieve less variable heat treat
Derrom _______ __- ____ __ Aug. 6, 1940
2,210,482
ment of the materials in the kiln.
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