Патент USA US3091453код для вставки
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 mniuoâv@ämwîì IO N INVENTORS H. HERZ ROMIG W ' ww f. w 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.