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 UNIVERSITY OF ILLINOIS 
 LIBRARY 
 
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 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN 
 
 
 
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UNIVERSITY OF ILLINOIS BULLETIN 
 
 Vol. V. AUGUST. 17, 1908 No. 39b 
 
 [Entered February 14, 1902, at Urbana, Illinois, as second-class matter 
 under Act of Congress of July 16th, 1894. 
 
 BULLETIN No. 8. DEPARTMENT OF CERAMICS 
 
 C. W. ROLFE, Director 
 
 A Study of the Heat Distribution in Four 
 Industrial Kilns. 
 
 By A. V. BLEININGER 
 
 I 907- J 908 
 
 PUBLISHED FORTNIGHTLY BY THE UNIVERSITY 
 
A STUDY OF THE HEAT DISTRIBUTION IN FOUR 
 INDUSTRIAL KILNS. 
 
 BY 
 
 A. V. Bleininger^ Champaign, Illinois. 
 
 There is a decided lack of data in regard to the con- 
 sumption of fuel in periodic ceramic kilns, expressed in 
 accurate terms, as well as with respect to the way in Avhich 
 tlie heat is distributed. It was hence thought advisable to 
 undertake the exanunation of several kilns for the purpose 
 of determining the ratio between the heat made useful and 
 that escaping as waste. The kilns studied represented sev 
 eral types and widely ditteriug conditions, one of them 
 being a sewer pipe, one a paving brick, and two, terra cotta 
 muffle kilns, entirely unlike in construction. In addition 
 a building brick kiln was examined, which has already 
 been reported upon elsewhere,* 
 
 In making a heat balance of a kilns we must determine 
 the following factors: 
 
 A. Heat introduced as fuel. 
 
 B. Heat lost by the waste gases. 
 
 C. Heat lost by the unburnt fuel in the ashes. 
 
 D. Heat used in the burning of the ware. 
 
 E. Heat taken up by the kiln and lost by I'adiation. 
 
 The last factor, important though it is, cannot be es- 
 timated by any direct means available, since the difficulties 
 opposed to its determination are too great. We must bo 
 satisfied to obtain it by difference. For, since the first 
 four items are readily obtainable by measurement, the fifth 
 is arrived at by the evident relation : 
 
 E=A— (B+C+D). 
 
 *"The Balance Sheet of a Down Draft Kiln," Clay Worker, February, 
 1908. Read before the N. B. M. A. 
 
4 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTKIAI. KILNS. 
 
 A. The heat introduced as fuel was of course readily 
 calcuhited from tlie weight of the coal used from day to 
 day. The calorific value of the latter was obtained by 
 determining the heating value of a well averaged sample 
 of the fuel in the calorimeter. This work aars done in the 
 department of industrial chemistry at the University of 
 Illinois, under the direction of Professor Parr. The weight 
 of the coal multiplied by its heating value gave the total 
 number of calories introduced. 
 
 B. The heat carried out by the waste gases was cal 
 culated from the daily coal consumption, the ultimate 
 analysis of the coal, the analysis of the stack gases, the 
 thermal capacity of the gases and the flue temperature. 
 The first factor was, of course, easily determined by weigh- 
 ing the coal, the second by the ultimate analysis of the 
 coal, this work having been carried out in the de])artinent 
 of chemistry under Professor Parr, the third by the analy- 
 sis of the flue gases, using the Orsat apparatus, the fourth 
 from known data, and the fifth by means of the Le Cliate- 
 lier thermocouple applied in the flue as close to the kiln 
 as possible. 
 
 The daily coal consumption permitted of calculating 
 the weight of coal fired per hour for a certain period, which 
 was, for the sake of convenience, taken as twelve hours. 
 This period was considered the unit in all the calculations. 
 
 From the ultimate analysis, allowing for the carbon 
 escaping Avith the ashes, the weight of the gases evolved 
 with theoretical air supply was calculated. If, for instance, 
 the coal had the following composition : 
 
 Carbon 60.15% — 3-03 (lost in ashes)=57. 12% 
 
 Hydrogen 415% 
 
 Oxygen 9-37% 
 
 Sulphur 4-34% — 1-30 (lost in ashes) = 3.04% 
 
 IMoisture 7.90% 
 
 Ash 14.09% 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. O 
 
 1 kg. of coal Avould result, on burning with just tlie requi- 
 site amount of air, in 
 
 0.5712.^1 = 2 09 kg: of carbon dioxide 
 0415.9 f 0.079 = 0.453 kg. of steam 
 
 0.0304 X 2 = 060 kg. of sulphur oxide 
 0.5712.»|X 3 35 = 5 900 kg. of nitrogen 
 
 The weight of air required for the combustion of 1 kg. 
 cf this coal would then l)e 7.66 kg. 
 
 The tiue gas analysis was simply made for the purpose 
 of determining the amount of excess air introduced into 
 tlie kiln, as this evidently changes the weight of the gases 
 resulting from 1 kg. of the coal materially. It was en- 
 deavored to take sam])lcs from the flue so that they repre- 
 sented average conditions, and from twd to three analyses 
 were made each hour. This meant the making of hundreds 
 of analyses during each burn. As the basis of the calcula- 
 tion of the excess air present tlie oxygen found was used 
 according to the relation : 
 
 Coefficient of air-admission= 
 
 100— 4.76X 9f; Oxygen. 
 
 To illustrate: Supposing the gas was found to con- 
 tain 5% of oxygen. AVe would have then : 
 
 ]Oo — 4 76 N- 5 =^-'^^, rcpi-esenting total aii- admitted. 
 
 The excess air jnust then be 1.31 — 1^0.31. 
 
 Applying this to the weights of the gases ol>tained 
 above we would have: 
 
 2.090 kg. CO2 
 0.453 kg. H2O 
 0.060 kg. SO; 
 5.900 kg. N: 
 7.66.0.31=2.370 kg. Air 
 
 It might be added that the gas samples were taken as 
 close to the kiln as possible, so as to avoid the dilution 
 caused by the leakage of air into the flue near the damper. 
 
 In calculating the heat lost by the waste gases during 
 any given period we must first obtain the ratio of the heat 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 carried out by the gases evolved from 1 kg. of eoal at the 
 flue temperature to the heating value of this weight of coal. 
 
 In this calculation there are necessary the weight of 
 waste gases, their thermal capacity and the flue tempera- 
 ture. 
 
 The specific heats of the gases, as taken from the 
 standard tables are not suitable for the.se calculations, 
 since they apply only to a temperature range between 0° 
 and 100 ^C, and if used would cause a more' or less grave 
 error. The work of Le Chatelier and Mallard* has clearly 
 shown tliat the thermal capacity of gases is exj^ressed by 
 a parabolic formula of two parameters: 
 
 T T^ 
 
 in which Qu=heat capacity. 
 
 a=a constant comon to all gases=fi.5. 
 
 T=absolute temperature. 
 
 b=a constant, variable for diiferent gases. 
 
 The value of b for perfect gases like On, N21 H2 ^^^^^^ 
 CO is O.G, for luO 2.9, and for CO2 3.7. This formula 
 applies only to the molecular volume of each gas at abso- 
 lute temperatures. For the sake of convenience it is pre- 
 ferable to calculate the values in terms of one kg. and the 
 temperature in degrees C. This has been done in the 
 following table :t 
 
 THERMAL CAPACITY 
 
 OF I KG. GAS, IX KG. 
 
 CALS. 
 
 Temperature in 
 
 Oxygen 
 
 N'itrogen. Carbon 
 
 1 
 
 Steam 
 
 Carbon Dioxide 
 
 degrees C. 
 
 
 Monoxide 
 
 
 
 
 
 0.0 
 
 0.0 
 
 I 
 
 0.0 
 
 0.0 
 
 200 
 
 47-3 
 
 50.0 
 
 100. 
 
 43-1 
 
 400 
 
 88.0 
 
 100. 
 
 203 . 
 
 91.0 
 
 600 
 
 1.34-0 
 
 154-0 
 
 1 326.0 
 
 145.0 
 
 800 
 
 181. 
 
 207.0 
 
 ! 461.0 
 
 208.0 
 
 1000 
 
 232.0 
 
 264.0 
 
 ! 609 . 
 
 277.0 
 
 1200 
 
 284.0 
 
 3^5-0 
 
 770.0 
 
 354 
 
 1400 
 
 334 
 
 383-0 
 
 943-0 
 
 435-0 
 
 *Tndustrial Furnaces and Methods of Control. Emilio Damour, p. li. 
 Metallurgical Calculations. J. W. Richards. 
 
 tindustrial Furnaces and Methods of Control. Emilio Damour, p. 13. 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 7 
 
 By plotting a curve from these data for each gas the 
 heat capacity of 1 kg. of the gas can be read off at once 
 for any temperature. This was done in the work under 
 discussion. For the purpose of illustration let us take 
 the figures obtained above for the weights of the gases, and 
 assuming that the gases left the kiln ot 620 "C we would 
 have the following heat capacities, the atmosplieric tem- 
 perature being 20°. 
 
 2.09 X145 =303.05 kg. cals., heat capacity of CO2 
 0.453X326 =147.68 kg. cals., heat capacity of H2O 
 0.453X80+0.453X537 =279.50 kg. cals., heat of vaporization of HoO 
 5.9 X154 =908 00 kg. cals., heat capacity of Ni 
 2.37 X 149.4=354.08 kg. cals., heat capacity of air 
 
 l992.3l^total heat carried out by waste gases. 
 
 If the calorific power of the coal used is 0200, it is 
 evident that the heat lost by the waste gases must be 
 
 1992 
 
 equal to ^^^^jX 100^52.13 per cent. For every 100 pounds 
 
 of coal fired we thus lose in the waste gases 32.13 pounds. 
 
 The temperature, as has already been stated, was ob- 
 tained by means of the Le Chatelier thermocouple, inserted 
 into the flue close to the kiln. Corrections were made for 
 the atmospheric temperature. This was done by fastening 
 a thermometer to the junction between the platinum and 
 the copper wire. The correction is equal to 0.5 of the ther- 
 mometer reading where the atmospheric temperature does 
 not exceed 40°. In very hot places the correct procedure is 
 to insert the copper junction in boiling water and to cali- 
 brate the couple under these conditions. The calibration 
 is to be made by means of the melting points of zinc, silver 
 and gold or copper. 
 
 In the losses due to the waste gases must be included 
 also the loss due to the escape of combustible gases. Under 
 the conditions of the kilns examined in this work the 
 amount of carbon monoxide found in the gases was very 
 small. Immediately after firing some of this gas was 
 found, but it disappeared in a few minutes. For this rea- 
 
8 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 son it was not included in the losses incurred by the flue 
 gases. It seems that the hot mass of clay tends to promote 
 the oxidation of the combustible gases formed in the 
 furnace. 
 
 D. The heat required to raise the ware to the ulti- 
 mate temperature of the kiln w^as calculated from the 
 weight of the ware, its specific heat and the kiln tempera- 
 ture. The amount of water contained in the clay was 
 taken into consideration. Unfortunately, several import- 
 ant constants are lacking, such as the heat of dehydration 
 of clay and the heat of vaporization of the hygroscopic 
 water. Even the specific heat of clay is not known for the 
 liigher temperatures, though it is usually given in text 
 books as being 0.2. Mr. J. K. Moore, during some recent 
 work in connection with his thesis, found the average ther- 
 mal capacity of a burnt No. 2 fire clay between the limits 
 of 400-1100° C to be 0.235. At the time the calculations 
 for this work were made the specific heat of clay was taken 
 as 0.2. The heat of dehydration was assumed to be 200 gr. 
 calories per gram of water. No reliable data was obtain- 
 able on this subject. The latent heat of the hygroscopic.' 
 water which leaves in the neighborhood of 200 ' was taken 
 to be 476 according to the formula of Griffith's, 
 
 L=596.73— O.eOt. 
 
 Assuming then a clay, containing 2% of hygroscopic 
 and 7% of chemical water which is to be raised to 1120°, 
 we would have for 1 kg. of the dried clav the following 
 heat consumption, the atmospheric temperature being 20°. 
 Tlie dehydration temperature to be taken as 650°. 
 
 Hygroscopic water 0.02X180X1= 3.6 kg. calories 
 
 0.02X476 = 9.5 kg. calories 
 
 Chemical water 0.07X .02X650^ 9. 1 kg. calories 
 
 0.07X200 =14.0 kg. calories 
 Clay , 0.93X0.2X1100=204.6 kg. calories 
 
 I kg. clay thus requires .' 240.8 kg. calories 
 
 E. As has been mentioned above, the heat absorhed 
 by the kiln and lost by radiation was obtained by differ- 
 ence. 
 
A STUDY OF HEAT DISTRIBUTION IX FOUR INDUSTRIAL KILXS. U 
 
 APPARATUS. 
 
 The apparatus nsed in tliis work consisted of tlie Orsat 
 gas apparatus, two tin gas samplers, snpported by tripods 
 and painted with asphaltum paint, one Siemens-Halske 
 niilli-voltnieter and donble throw switch, two thermo- 
 couples, one for the fine, the other for the kiln, two ther- 
 mometers reading to 100 C and two to 300°, the latter 
 being nsed during the watersmoking period, and two Rich- 
 ardson-Lovejov metal draft gauges, tilled with colored pe- 
 troleum and showing a reading magnified four times. 
 
 The gas was drawn from the flue through •>4" pipes 
 l)lugged at the end and perforated around the side. The 
 pipe connected to the draft gauge was provided with an 
 elbow so that the end of the pipe was parallel to the axis 
 of the flue and pointed in the direction of the stack. This 
 was found to be important, giving more consistent readings 
 than when the pipe was inserted at right angles to the flue. 
 
 KRAFT GAUGE. 
 
 The readings of the draft gauge were not necessary 
 for the determination of the heat escaping through the 
 stack, since the weight of coal actually tired was used as 
 the basis of the calculations, but they were useful in indi- 
 cating the increasing velocity of the gases in the stack. 
 The draft gauge without a Pitot tube cannot be used to 
 measure the velocity of the gases except it is calibrated 
 against an anemometer. A Pitot tube suitable for the 
 purpose was not available, since the usual metal instru- 
 ment would soon be destroyed by the high temperature of 
 the gases and the time was too short for making a clay 
 tube of this kind. 
 
 AVith the Pitot tnV)e the velocity of the gases in tlu^ 
 flue or stack is calculated from the relation. 
 
 where v=the velocity in feet or meters per second. 
 
10 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 g=i:the gravity constant, 32.14 ft. or 9.8 meters. 
 
 h=real heiglit of the petroleum column in feet or me- 
 ters, shown by the draft gauge. 
 
 clr^iirdensit}^ of petroleum, in terms of water at 4°C. 
 
 d==;density of the gases at the temperature and pres- 
 sure of the stack or flue in terms of water at 4°. 
 
 The relation between the real velocity as determined 
 by the anemometer and that calculated from the Pitot tube 
 is approximately 1.1 — 1.2, for the velocities in question in 
 ceramic stacks. The Pitot tube velocities are hence to be 
 multiplied by this factor in order to obtain the real 
 velocity.* 
 
 Some erroneous conceptions are current in regard to 
 the meaning of the draft gauge readings. The value indi- 
 cated by the gauge does not represent the total magnitude 
 or "head'' of the draft, but only that part of it which cor- 
 responds to the velocity, of the gases and which is not avail- 
 able for pulling the gases through the furnaces and kiln. 
 
 The total head of draft which may be expressed in 
 inches or millimeters of water or air at 0° is the pull ob- 
 tained by a stack, measured by the difference in the weight 
 of the hot gases occupying the chimney and the weight of 
 the same volume of air at atmospheric temperature. To 
 illustrate, assuming a stack 10 meters high and 1 square 
 meter in cross section at 273° C, with the atmospheric air 
 at 0°, we have a difference in weight as follows: The 
 weight of 10 cubic meters of air (volume of stack) at 0°C= 
 12.93 kg. The weight of the same volume of air at 273°= 
 6.465 kg. We have, then, as the measure of the total draft 
 the weight of 12.93-6.465=6.465 kg. This weight is dis- 
 tributed over the cross section of 1 sq. meter=^10000 sq. cm. 
 The pressure upon 1 sq. cm. is thus 0.65 gram. This cor- 
 responds to a height of a water column of 0.65 cm. Ex- 
 pressed in terms of air at 0° it is 0.65X772=501.8 cm., 
 water being 772 times as heavy as air at the same tempera- 
 
 *W. D. Harkins and R. E. Swain. Jour. Am. Chem. Soc, Vol. 29, 
 p. 970. 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 11 
 
 ture. This head of 5.02 meters represents the total draft. 
 But only part of it is available for forcing the air needed 
 for combustion into the furnaces and pulling out of the 
 kiln the gases produced. Part of this force is taken up by 
 the velocity of the stack gases and part of it by the friction 
 of the gases in the stack. The head available tor the kiln, 
 then, is equal to the total head minus the velocity and 
 friction heads. 
 
 The velocity head is calculated from the relation 
 
 V2 
 
 K=- . 
 2g 
 Assuming the A^elocity of the gases in the above stack 
 to be G meters per second, the velocity head, l^, becomes 
 36 
 
 h,= =1.84 m., in terms of air at 273°. 
 
 2X9.8 
 Reduced to terms of air at 0" tliis head becomes 0.02ni. 
 According to Richards the friction head, Ih,, of a stack is: 
 
 H 
 h.,=1.9-K 
 d 
 where H=lieight of stack. 
 
 d=diameter or side of chimney. 
 k=constant, whose average value=0.08. 
 Substituting, we obtain 
 10 
 ho=l . 0— . . 08=0 . 15 meters. 
 1 
 The head of the stack thus available for pulli3Jg the 
 gases through the kiln=5.02 - (1.84+0.15 »=3.03 meters 
 of air at 0°. 
 
 Experimentally, the total head of a stack may ])Q de 
 termined by suddenly dropping the damper and ol)serving 
 the draft gauge reading instantly. The common idea tliat 
 the draft of a kiln is increased greatly as the stack be 
 comes very hot is not true. It is true that the draft in- 
 
12 A STUDY OF HrlAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 creases up to a certain temperature but not beyond it, in 
 spite of the fact tbat the velocity of the gases increases. 
 But as Ave have seen, increased stack velocity means in- 
 creased loss in available head. It must be remembered 
 that the draft of a stack is not measured by the volume of 
 the gases drawn off, but by the weight of gas removed per 
 unit time. 
 
 We have thus the expression : 
 
 n„ Sd y 2ff 0.00366. L (ti-t2) , 
 
 UU^^^^ ^^ where 
 
 ^ If 0.UO366 ti 
 
 Qu=the weight of the gases removed per second. 
 S =cross section of stack, 
 d =density of the gases at 0°. 
 g =9.8 m. OT 32.14 feet. 
 L =lieiglit of stack. 
 
 ti =mean temperature of the gases in the stack in 
 degrees C 
 
 t ^temperature of the air in degrees C 
 
 Since here Sdi 2 g 0.00366 L=constant we may say 
 
 that Qu^K "i"^ u. 00366 tT 
 
 By differentiation or grajjhical determination of the 
 maximum value of Qu we find that the temperature at 
 which the greatest weight of gases is removed is at 273°C. 
 Nothing is gained, therefore, as far as the available draft 
 of a stack is concerned, by maintaining a mean stack tem- 
 perature higher than 273^ above the atmospheric tempera- 
 ture. 
 
 SEWER PIPE KILN. 
 
 The kiln in (juestion was one of the older kilns on the 
 plant and was rectangulai-, its dimensions being : Length, 
 42 feet, width, 17i(-. feet, height, 19 feet, inside measure- 
 ments. It was set with double strength 20 inch pipe, 
 nested with smaller sizes, and contained 120,460 pounds of 
 clay, all told, including rings, etc. 
 
A S1*UDy OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 13 
 
 In burning, 87,335 pounds of coal were used, which 
 had the following composition: 
 
 Carbon 59-76% 
 
 Hydrogen •. 4.08% 
 
 Oxygen and Nitrogen 10. 72% 
 
 Sulphur 2.57% 
 
 Ash 11.74% 
 
 Moisture 11.13% 
 
 The ash was found to show tlie following analysis : 
 
 Carbon 29.17% 
 
 Hydrogen 0.26% 
 
 Oxygen and Nitrogen 3 . 13% 
 
 Sulphur 3 . 16% 
 
 Ash 68.99% 
 
 Moisture 1 . 55% 
 
 The calorific power of tlie coal was 6,020 calories, or 
 10,837 B. T. U. 
 
 The weights of tlie gases from 1 kg. of coal were: 
 
 CO;=2.070 kg. 
 
 H-0=o.478 kg. 
 
 N==5.76S kg. 
 
 assuming perfect combustion. The weight of air re((uired 
 per kg. of coal is 7.48 kg. ; 3.42 per cent of carbon were lost 
 in the ashes. 
 
 The length of the burn was 129 hours. This was di- 
 vided into 10 periods of 12 hours and one of 9 hours. All 
 the analyses and other data were averaged on the basis of 
 the 12 hour period, care having been taken to make the 
 analyses representative of the average conditions. 
 
 In Fig. 1 we have represented the average coal con- 
 sumption per hour during the burn. Fig. 2 shows the 
 time-temperature curves of the kiln and flue. In Fig. 3 
 there are shown the average carbon dioxide and air per- 
 centages for each period throughout the burn. 
 
 HEAT LOST BY WASTE GASES. 
 
 In calculating the heat passing off with the waste 
 gases from the data represented by the above curves, the 
 mean flue temperature from the beginning to the end of 
 each period was taken and the atmospheric temperature 
 
14 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 TRANS. AM CER 5nc. VOL X 
 
 FIGl. 
 SEWER PIPE KILN. 
 
 FUEL CONSUMPTION PER HOUR. 
 
 BLtlMINCiER. 
 
 14-00 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 1000 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 \ 
 
 
 / 
 
 
 
 800 
 
 
 
 
 
 
 
 \ 
 
 \^ 
 
 / 
 
 
 
 
 
 
 
 
 
 
 N 
 
 I 
 
 
 
 oc 
 
 ^ 600 
 oc 
 
 UJ 
 
 Q- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 < 
 
 o 
 o 
 
 o 400 
 
 in 
 
 o 
 Z 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 o 
 
 200 
 
 
 
 / 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 k 
 
 
 
 
 
 
 
 
 
 n i' 
 
 A 
 
 r 
 
 
 
 
 
 
 
 
 
 
 24 
 
 HOURS 
 
 7i 
 
 96 
 
 120 
 
 (lediictecl. The heat carried out by the gases correspondiiiij; 
 to 1 kg. of coal was then calculated, as shown in th(^ first 
 part of this paper. In the case of the sewer-pipe kiln the 
 waste heat of each period is given in the folloAving table : 
 
A SlUDV or HKAT IMSTRlIiUTlON IN FOUR INDUSTRIAL KILNS. 
 
 16 
 
 00 
 
 ON 
 
 00 
 
 
 ^ 
 
 1-4 
 00 
 
 HH 
 
 
 H4 
 
 
 fO 
 
 
 J^ 
 
 
 CO 
 
 
 fO 
 
 O 
 
 IN 
 
 01 
 
 l^ 
 
 
 
 
 CO 
 
 VO 
 
 r:: 
 
 
 N 
 
 00 
 
 N 
 
 HH 
 
 
 
 n 
 
 bo 
 
 Ah 
 
 
 ^ 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 16 
 
 T«ANS AM CER- 50C. VOLX 
 
 BLEININGER 
 
 FIG Z. 
 SEWER PIPE KILN. 
 
 TIME-TEMPERATURE CURVE. 
 
 1100 
 
 
 
 
 
 / 
 
 ^ 
 
 900 
 
 
 
 
 
 J^ 
 
 
 
 
 
 — ' 
 
 
 
 
 
 
 
 y 
 
 
 
 
 
 
 i /tio 
 
 
 / 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 5 
 
 
 
 1 
 
 
 
 
 
 
 J 
 
 
 
 J 
 
 
 
 \^P^ 
 
 , j^ 
 
 ] 
 
 
 y 
 
 k j 
 
 
 > 
 y 
 
 /- 
 
 
 
 
 ^^ 
 
 
 ^>< 
 
 
 Y 
 
 
 
 
 „' 
 
 .^i:::!!--. 
 
 ^-J — ' 
 
 h-r 
 
 
 
 
 
 
 2 3 
 
 PAYS 
 
 TRANi AM. CER SOC VUL X 
 
 FIG5. 
 SEWER PIPE KILN. 
 
 AVERAGE CARBON DIOXIDE 
 
 Sc 
 
 AIR CONTENT OF FIRE GA6E5. 
 
A ?TUDV OK KI:AT DISTUIIiL'TION IX FOL'R INDUSTRIAL KILNS. I( 
 
 Adding up the pounds of coal wliioh express the loss 
 of heat by the ^vaste gases we obtain 16351 pounds. Since 
 tlie total coal fired was 87,330 pounds, it is evident that 
 the heat escaping through the flue is equal to 18.6 per cent. 
 Fig. 4 shows the losses for each period of the burn. 
 
 HEAT IlIXiUIUEI) TO BURN THE WARE. 
 
 Calculating the heat required to burn 120,160 pounds 
 of clay, as illustrated above, to a temperature of 1100° 
 there will be used 13,689,179 kg. calories, which equal 
 4987 pounds of the coal employed in this case. This cor- 
 responds to 5.71% of the total heat introduced into the 
 kiln. 
 
 HEAT LOST IN THE ASHES. 
 
 The carbon lost in the ashes amounts to 3.42% of the 
 coal. Since practically no available hydrogen was found 
 
 TRAN5 AM CER 50C vOl X. 
 
 B L 1 1 M I N Ci t rs 
 
 F1G4-. 
 SFWER PIPE KILN. 
 %HEAT LOST BY WASTE 
 GASES IN TERMS OF HEAT INTRODUCED. 
 
18 
 
 A STUDY OF HKAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 in the ashes, the heat lost in this way evidently is 0.0342 X 
 8080 kg. calories per kg. of coal. Calculating this loss in 
 percentage we obtain 4.58%. 
 
 HEAT TAKEN UP BY THE KILN AND LOST BY RADIATION. 
 
 The heat coming under this heading is evidently ob- 
 tained by subtracting the sum of 18.6%+o.Tl%-f-i-58% 
 from 100 which gives us 71.1%, a very high percentage, 
 approaching the similar losses of open-hearth steel fur- 
 naces and must be ascribed to the poor condition of the 
 kiln. 
 
 In Fig. 5 the draft-gauge readings are plotted, ex- 
 pressed in draft gauge divisions and inches. The gauge 
 was*frequently set to the zero point to allow for the evapor- 
 ation of the petroleum. 
 
 TRANS. AM. CER SOC. VOL X. 
 
 FIG 5. 
 5EWER riPE KILN. 
 DRAFT GAQE CURVE. 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 19 
 
 Collecting; the data obtained in these calculations we 
 find the heat distribution to be as follows : 
 
 Heat lost by the fire gases 18.6 % 
 
 Heat taken up by the ware 5.7 % 
 
 Heat lost by ashes 4.58% 
 
 Heat taken by kiln and lost by radiation 71 . i % 
 
 100.0% 
 In burning looo kg. of ware there were used 4378341 kg. cals. 
 In burning i ton of ware there were used 3984200 kg. cals. 
 In burning i ton of ware there were used 1456.8 lbs. of coal 
 Temperature iioo°C. 
 
 Durinji' saltinj; the fire gases were found to contain 
 15.6% COo and 2,4% O^. An interesting fact observed was 
 also that the temperature during salting rose 5° in spite 
 of the fact that the reactions involved in salting are endo- 
 thermic, thus showing that there is no diflflculty in main- 
 taining sufficient heat. 
 
 During the latter part of the burn some carbon mon- 
 oxide was found in the gases, but only for a short time and 
 in small amounts. The loss of heat due to this source was 
 hence neglected, 
 
 r.wixf; r.KicK kiln. 
 
 This kiln was a 2(1 ft. round down draft kiln and con- 
 tained 357,204 pounds of burnt clay. The amount of coal 
 used was 121,028 pounds. The maximum temperature 
 reached was 1110°O. 
 
 Analysis of coal : 
 
 Carbon 60.15% 
 
 Hydrogen 4.15% 
 
 Sulphur 4-34% 
 
 Oxygen and Nitrogen 9-37% 
 
 Ash 14.09% 
 
 Moisture 7 .90% 
 
 The calorific power was found to be 6231 or 11216 B. 
 T. U, 
 
 Analysis of ashes: 
 
 Carbon 21 . 53% 
 
 Hydrogen 0.11% 
 
 Sulphur 1.81% 
 
 Oxygen and Nitrogen 0.83% 
 
 Ash" 77.30% 
 
 Moisture ,,,.,.,,.,. o . 08% 
 
20 
 
 A STUDY OF HKAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 Thus 3.03% of carbon in the coal was lost with the 
 ashes. 
 
 From 1 kg-, of this coal there would be evolved : 
 
 2.090 kg. carbon dioxide 
 0.453 kg. steam 
 5.900 kg. nitrogen 
 
 TRANS. AM. CER. SOC. VOLX 
 
 BLElNINGER. 
 
 800 
 
 700 
 
 600 
 
 500 
 
 4-00 
 
 300 
 
 200 
 
 100 
 
 FIG 6. 
 
 PAVING BRICK KILN. 
 FUEL CONSUMPTION PER HOUR. 
 
 3 A 
 
 PA-rs. 
 
 • 5 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 21 
 
 TRANS AM. CER SOC VOlX. 
 
 
 FIG 7. 
 FAUINO BRICK tllLN. 
 
 
 TIME -TEMrER/VTURE , 
 
 
 ii. y^^''-^ V ' 
 
 
 
 DRAFT GAOE CURVE5 - / ^^IZSn : 
 
 
 
 
 
 
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 y^^^^'^^^^A' 
 
 
 
 
 
 
 
 
 
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 not eoiisiderino- the siilpliur dioxide and assuming perfett 
 conditions of combustion. For eadi kg. of uoal tired tliere 
 would have to be introduced 7.(10 leg. of air for theoretical 
 combustion. 
 
 The length of the burn was 204 hours. 
 
 The coal consumption per hour is shown in Fig, for 
 each period of 12 hours throughout the burn. Fig. 7 gives 
 the time-temperature curves for the kiln (couple intro- 
 duced on top) and the flue as well as the draft gauge read- 
 ings. The latter are taken from the stack, and it must be 
 remembered that each division equals 3,4 inch and that the 
 readings are magnified four times. Each division thus 
 corresponds to 3-16 inch of petroleum, verti-.-al height. In 
 Fig. 8 the COo and air contents of the gases are repre- 
 sented. From the air curve we observe that the shale is 
 not a difficult one to oxidize, that the air content of the 
 gases is not excessive, and the heat losses are not so much 
 due to large air excess as to the high exit temperature of 
 the waste gases. 
 
22 
 
 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 TRANS AM. CER &0C VOl X 
 
 FIGS. 
 
 PAVING - BRICK KILN. 
 
 AVERAGE CARBON DIOXIDE 
 AIR CONTENT OF FIRE GASES 
 
 BLEININaER 
 
 
 < 
 
 K 
 
 \ 
 \ 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 70 
 
 
 
 
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 i-'r- 
 
 
 
 
 /\ 
 
 { 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 T 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 n A-YS 
 
 HEAT CARRIED OUT BY WASTE GASES. 
 
 Proceeding as before we can calculate the heat carried 
 out into the flue from the weight of coal fired per period, 
 the air content of the gases and the flue temperature, so 
 that we have the followino- results : 
 
A STUDY OF HF.AT UISTKI IK'TlOX IN-POIR INDUSTRIAL KILNS. 
 
 23 
 
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24 
 
 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 Adding the pounds of coal, wbicli are equal to the heat 
 wasted by the fire gases, we obtain 36,454 pounds, which is 
 29.9% of the total amount of coal fired, or we may say that 
 the kiln shows a flue loss of 29.9%. Fig. 9 shows the heat 
 loss per period graphically. 
 
 TRANS. AM. CER SOC. VOL X 
 
 FIG 9. 
 
 rAYING-BRlCK KILN. 
 
 %HEAT LOST BY WASTE QA5E5 TER PERIOP 
 
 IN TEHMS OF HEAT INTRDPUCEf. 
 
 BLEININGER 
 
 HEAT REQUIRED IN HEATING UP THE WARE. 
 
 Calculating the amount of heat theoretically necessary 
 to raise the clays to 1110° C, as shown above, we find that 
 this heat is equal to 13,778 pounds of coal, which is 11.3% 
 of the total amount. 
 
 HEAT LOST BY UNBURNT CARBON IN THE ASHES. 
 
 Since the carbon lost by the ashes is equal to 3.03% of 
 the coal, the heat lost in this way must be equal to 
 8080X0.0303=245 calories, or 3.9% of the calorific value 
 of the coal. 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 25 
 
 HEAT TAKEN UP BY THE KILN AND LOST BY RADIATION. 
 
 This necessarily must be equal to 100 — 45.1^54.9%. 
 Suminai'izino-, we have the following heat distribution : 
 
 Heat lost by the waste gases 29.9% 
 
 Heat taken up by the brick 11 .3% 
 
 Heat lost by carbon in the ash 3-9% 
 
 Heat taken up liy the kiln and lost by racTiation 54-9% 
 
 100.0% 
 
 In this kiln and under the conditions of the test car- 
 ried on 
 
 1000 kg. burnt clay required 2056230 kg. calories. 
 I ton burnt clay required 1871169 kg. calories. 
 I ton burnt clay required 660 pounds of coal. 
 Temperature iiio''C. 
 
 TERRA COTTA KILN. A. 
 
 This kiln was a muffle kiln, the muffle being 16 ft. in 
 diameter. The kiln was set with 42,423 pounds of green 
 terra cotta and 2t),!)C0 pounds of supports, kiln blocks, etc. 
 The coal consumed was 29,340 pounds, and the duration 
 of the burn was G7 hours. The maximum temperature 
 reached in the muffle was 1080 ^C. 
 
 Coal analysis : 
 
 Carbon 66.78% 
 
 Hydrogen 4.81% 
 
 Sulphur 0.84% 
 
 Oxygen and Nitrogen _. 9.68% 
 
 Ash 7 • 59% 
 
 Moisture 10.30% 
 
 Calorific power 6716 or 12090 B. T. U. 
 
 Analysis of ashes: 
 
 Carbon 20.92% 
 
 Hydrogen 0.06% 
 
 Sulphur 0.35% 
 
 Oxygen and Nitrogen 0.53% 
 
 Ash 77-94% 
 
 Moisture 0.20% 
 
 Assuming theoretical combustion, the weight of the 
 gases developed from 1 kg. of coal is 2.39 kg., carbon diox- 
 
26 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 rtlaNj AM CEi* 50C vClX 
 
 BLEIMNQER 
 
 &0U 
 
 500 
 
 *00 
 
 300 
 
 FIG 10. 
 
 TERRACOTTA KILN A. 
 
 COAL CONSUMPTION PER MOUR. 
 
 ' 3 
 
 TRANS AM CEfl 30C VOLX 
 
 BlCini N r, cr^ 
 
 Fia II. 
 
 TERRACOTTA KILN A. 
 
 TIME -TEMPERATURE, 
 CURVES. 
 
 HOURS 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 ide, 0.553 kg. steam, and 5.8 kg. nitrogen, the sulpliur being 
 neglected. The air introduced under the same conditions 
 would be 7.54 kg. 
 
 Fig. 10 shows the average coal consumption per hour 
 for each period of 12 hours. It is seen to differ from the 
 corresponding curve for the open kilns by the compara- 
 tively small tiuctuations in the amounts of fuel fired, as is 
 to be expected from this type of kiln. The time-tempera- 
 ture curve is given in Fig. 11. The COo and air curves of 
 
 TRANi. AM CER iOC VOLX. 
 
 BlEinin&er 
 
 Fig. 12 indicate strongly oxidizing conditions throughout 
 the burn. The draft gauge readings have been rejected 
 owing to the rather unsatisfactory place at which the gauge 
 was connected to the flues surrounding the muffle. 
 
 HEAT CARRIED OUT BY THE WASTE GASES. 
 
 Proceeding with the calculation of the flue loss we 
 can tabulate the results as follows: 
 
28 
 
 A ?TUDY OF HEAT DTSTRlBUriON IN FOUR INDUSTRIAL KILNS. 
 
 
 I 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 
 
 Kg. calories lost per kg. of coal 
 
 741 
 
 1102 
 
 1476 
 
 1 954 
 
 2622 
 
 2510 
 
 % of liear lost in terms of heating 
 
 II. 
 
 16.4 
 
 22.0 
 
 29.1 
 1830 
 
 39-0 
 2214 
 
 37-4 
 
 
 
 Pounds of coal lost by waste gases 
 
 per period 
 
 396 
 
 876 
 
 1248 
 
 1017 
 
 Addinji' up the amounts of coal we have 7581 pounds, 
 whicli is 25.8% of the total amount of fuel used, 21),:U0 
 pounds. In Fig. 13 the average heat losses per perio<l are 
 shown graphically. 
 
 HEAT REQUIRED TO BURN THE WARE. 
 
 Calculating the heat theoretically required to Imrn 
 the terra cotta and to heat up the supports, we find that 
 this amounts to 3,G88 pounds, or 12.57% of the total heat 
 introduced. 
 
 HEAT LOST BY CARBON IN THE ASHES. 
 
 The carbon lost with the ashes amounts to 1.6% of the 
 coal. Thus the heat lost in this way is (8080X0.016)-^ 
 671(5 X 100^1.9%. In this kiln the grates were in excellent 
 shape, and this explains the low loss. 
 
 HEAT TAKEN UP BY THE KILN AND LOST BY RADIATION. 
 
 It is evident, then, that the loss must be equal to 
 100- (25.8+12.57+1.9)=59.73%. 
 
 Summarizing, the heat distribution i ; ..s r;.:;ows: 
 
 Heat lost by waste gases 25 . 80% 
 
 Theoretical heat necessary to heat up charge 12.57% 
 
 Lost by carbon in the ashes i .90% 
 
 Heat taken up by kiln and lost by radiation 59-73% 
 
 100.00% 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 31) 
 
 1000 kg. terra cotta under these conditions required 
 5113775 kg. eals.=1675 pounds of coal. 
 
 1000 kg. terra cotta plus supports: o007i.M)5 kg. cals. 
 =985 pounds of coal. 
 
 1 ton terra cotta required 1521 pounds of coal. 
 
 1 ton terra cotta plus supports 896 pounds of coal. 
 Temperature=1080°C. 
 
 In taking several samples of gas from the muffle during 
 the raising of tlie heat, 3% of CO^ Avere found. 
 
 TERRA COTTA KILN. B. 
 
 This kiln was constructed entireh^ differently from 
 the preceding one. Its inside muffle diameter was 2V6'% its 
 height 17 feet high in the center and 12 feet to the spring 
 of the arch. The charge consisted of 113,280 pounds of 
 terra cotta and 75,691 ])ounds of kiln stonefs and supports. 
 The fuel used amounted to 81.420 pounds of coal. Length 
 of binii, 115 hours. The kiln was well built and in excel- 
 lent coiulition. The maxiiiniiii tcmjx'rature was 1115°C. 
 
 Analysis of coal : 
 
 Carbon 69 . 30% 
 
 Hydrogen 4.62% 
 
 Sulphur 1 . 64% 
 
 Oxvgcn and Nitrogen 9-94% 
 
 \sli 6.55% 
 
 .Moisture 7-95% 
 
 Calorific power 6961, or 12330 B. T. U. 
 
 Analysis of ash : 
 
 Carbon 20 . 53% 
 
 Hydrogen o . 22% 
 
 Sulphur 0.51% 
 
 Oxygen and Nitrogen i .03% 
 
 Ash 77.40% 
 
 Moisture 0.31% 
 
 1.34% of carbon was lost in the ashes. 1 kg. of coal 
 resulted in 2.49 kg. carbon dioxide, 0.495 kg. of steam, and 
 6.97 kg. nitrogen, assuming theoretical combustion, and 1 
 kg. of coal required under these conditions. 8.24 kg. of air 
 for combustion. 
 
30 
 
 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 O 
 tu lU 
 h- o 
 
 • S o 
 
 z <" ^ 
 
 -J Q = 
 
 
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 h- _j uj 
 
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 lO 
 
 ■«iNi 1V3M do svNygi ni ison iv3h % 
 
A STUDY OF HEAT DISTKIBUTION ]N FOUR INDUSTRIAL KILNS. 31 
 
 TRANS AM. CtR 50C VOL X- BLtlNINOER 
 
 1000 
 
 900 
 
 Soo 
 
 700 
 
 600 
 
 500 
 
 ° 400 
 
 300 — 
 
 ZOO 
 
 100 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 , 
 
 
 
 
 
 
 
 
 
 
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 / 
 
 k 
 
 
 • 
 
 
 
 L J . 
 
 
 
 \ 
 
 / 
 
 
 
 
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 / 
 
 
 
 
 
 
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 Y 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 FIG I+. 
 TERRACOTTA KILN B. 
 FUEL CONSUMPTION PER HOUR. 
 
 
 
 
 
 
 
 
 
 2+ 
 
 48 
 HOURS 
 
 7Z 
 
 9b 
 
 120 
 
 Fiji'. IJr shows the coal coiisiiinptioii per hour as the 
 average for each period of 12 hours. lu Fig. 15 Ave have 
 the tiuie-temperature curves for the kiln and the flue as 
 well as the draft gauge readings. It is sIioaau here that 
 the fire gases leave at a very high temperature and that 
 hence a large flue loss is to be expected. The difference 
 
32 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 TRANS AM CER SOC. VOLX. 
 
 FIG16. TERRA COTTA KILN B. 
 
 TIME - TEMPERATURE 
 
 BLEININOER 
 
 TRANS AM CEH SOC VOLX. 
 
 BLEININOER 
 
 
 
 
 ^ 
 
 > ^ 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 / 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 / 
 
 
 
 
 
 
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 \ 1 
 
 ' — -~4. ^ 
 
 
 < 
 
 k 
 
 / 
 
 
 
 
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 rx;. 
 
 ^ 
 
 
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 FIG 16. 
 
 
 
 — 
 
 
 
 
 TERfiA COTTA KILN B. 
 
 AVeRAQE CARBON DIOXIDE k 
 
 AIR CONTENT Of FIRE GASES. 
 
 
 
 — 
 
 r 
 
 
 
 
 
 1 
 
 1 
 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 33 
 
 in construction between kilns A and B is brought out 
 clearly by these curves. Fig. 16 illustrates the average 
 carbon dioxide and air contents of the fire gases represent- 
 ing for each period. It is observed that in this kiln also 
 the conditions are decidedly oxidizing. 
 
 HEAT LOSSES DUE TO THE FLUE GASES. 
 
 The results of the calculations ai-e again indicated in a 
 
 table, viz : 
 
 in 
 
34 
 
 A ?TUDY OF HEAT DISTRIBUTIOX TN FOUR INDUSTRIAL KILNS. 
 
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A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 35 
 
 Fig. 17 slioAvs the percentage of heat lost during each 
 period. 
 
 Adding up these amounts of coal we find that the 
 pounds of coal lost bj the waste gases are e(iual to 40,478 
 pounds, or 57.1% of the total amount of coal, 81,420 
 pounds. 
 
 HEAT REQUIRED TO BURN THE WARE. 
 
 By calculation the theoretical amount of heat rerjuired 
 to burn the terra cotta and heat up the supports was equal 
 to 6514 pounds, or 8% of the total amount of coal. 
 
 HEAT LOST BY UNBURNT CARBON IN THE ASHES. 
 
 Since the carbon lost to the ashes amounts to 1.34%, 
 the percentage heat loss due to this cause is [(8080X 
 0.0134)-^696i]Xl00=1.6%. 
 
 HEAT TAKEN VV I5Y THE KILN ANI> LOST BY RADIATION. 
 
 This is equal to 100— (57.1+8.0+1.6)=33.3%. This 
 item, therefore, is very small for this kiln, which speaks 
 well for its construction. 
 
 Summarizing, we have : 
 
 Heat lost by the waste gases 57 • i % 
 
 Theoretical heat required for charge 8.0% 
 
 Heal lost by unburnt carbon i .6% 
 
 Heat lost to kiln and radiation 33-3% 
 
 1000 kg. terra cotta required 5002518 kg. calories. 
 1000 kg. terra cotta and supports 307242^ kg. calories. 
 I ton terra cotta required 1439 pounds of coal. 
 I ton terra cotta and supports 884 pounds of coal. 
 Temperature iii5°C. 
 
 It will be observed that in spite of the large flue loss 
 in kiln B and the higher muffle temperature the efficiency 
 is about the same as that of A, this being due to the larger 
 size and hence greater tonnage of B. 
 
 For the sake of completeness the writer desires to 
 quote the results obtained for a brick kiln,* burning hard 
 
 ♦The Clay Worker, February, 1908. 
 
36 A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 shale building and sewer brick. This kiln was of the down 
 draft type, 28 feet inside diameter, and contained 66,190 
 brick, each weighino- 6% pounds. The amount of coal con- 
 sumed was 1)5,045 pounds, the B. T. U. value being 11162. 
 The summary of the heat distribution of this kiln was as 
 follows : 
 
 Heat lost by the flue gases 27.33% 
 
 Theoretical heat required to burn bricks 19-55% 
 
 Heat lost by unburnt carbon 3-51% 
 
 Heat taken up by kiln and lost by radiation 49.61% 
 
 100.00% 
 
 1000 kg. of brick recpiired 1,119,171 kg. calories, or for 
 eadi ton of ware 168 pounds of coal were fired. The tem- 
 perature was 1100° C. 
 
 Comment on the work of this article is hardly neces- 
 sary since the figures themselves are the conclusions to be 
 drawn. It might facilitate comparison to arrange the ab- 
 solute quantities of heat required in each case. 
 
 1000 kg. sewer-pipe 4378341 kg. calories 
 
 1000 kg. paving brick 2056230 kg. calories 
 
 IQOO kg. terra cotta, A 4640756 kg. calories 
 
 1000 kg. terra cotta plus supports 3007205 kg. calories 
 
 1000 kg. terra -cotta, B 5002518 kg. calories 
 
 1000 kg. terra cotta plus supports 307242;^ kg. calories 
 
 1000 kg. hard building brick I449I74 kg. calories 
 
 Expressing these values in pounds of coal per ton w(i 
 have : 
 
 I ton sewer pipe 1457 pounds coal 
 
 I ton paving brick 660 pounds coal 
 
 T ton terra cotta, .A.* 1524 pounds coal 
 
 I ton terra cotta and supports 896 pounds coal 
 
 I ton terra cotta, B I439 pounds coal 
 
 I ton terra cotta and supports 884 pounds coal 
 
 I ton building brick 468 pounds coal 
 
 In conclusion the writer wishes to acknowledge his 
 indebtedness to Professor C. W. Rolfe for having granted 
 the use of the funds and apparatus which made the work 
 possible. He also desires to express his appreciation of tlie 
 conscientious services and faithful cooperation of Mr. C. 
 
 *The coal used in \ is inferior in heating value to that in B. 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 0( 
 
 E. Merry, of the departmeut of ceramics, Uui\ersit3' of 
 Illinois. He wishes to thank especially the firms whose 
 kind ooperatiou was enjoyed in every case. 
 
 DISCUSSION. 
 
 Mr. Laufjcnbrch- : I wish to ask about the percent loss 
 of waste gases — I presume by that the speaker means both 
 the lost heat of the gases during the combustion of the 
 kiln and tlie lieat loss by radiation, not only from the out- 
 side during the burning, but also during the cooling of the 
 ware through the stack. Did you attempt in any waj^ tak- 
 ing the temperature on the outside of the kiln at the var- 
 ious points and times to determine what the percent of this 
 loss was, this radiation of the kiln shell during the com- 
 bustion? 
 
 Mr. Bliiniiif/rr: I have made no attemjtt to do this 
 since this is a very difficult matter, no reliable data being 
 at hand to serve as the starting point of such calculations. 
 The German Government is endeavoring to obtain the 
 necessary facts by experimental researches. There is ab- 
 solutely no reliance to be ])laced on any data found in 
 handbooks concerning radiation. There are any number 
 of theoretical calculations on this subject, but tiiey do nor 
 agree in their deductions. 
 
 Mr. Laiifjcnhrck : 1 am gla<l the German (lovernment 
 is investigating thi.s for it is a matter of vital imj)ortan( e. 
 Firing a kiln is i)iling up heat in its shell, and we usually 
 thnk only that the infiow must be greater than the outflow. 
 At the same time a large and increasing amount of heat 
 is being radiated on the outside; and while, relatively, fire 
 brick work is a poorly conducting substance, yet it is by 
 no means as poor as it ought to be; and this is one of the 
 gross defects of our kilns. We simply go on building ivilns 
 of fire brick instead of more effective insulating material, 
 instead of using hollow brick. The saving, entirely, aside 
 from the possible saving in fuel, is in the steadier accumu- 
 lation of heat in the kiln by a lessened radiation from the 
 
3S A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 outside. The 011I3' larger practical work I have attempted 
 aloug this line was iu building a kiln at the Mosiac Tile 
 Co., in Zanesville, Ohio, where I left an air space between 
 the fire brick lining and red brick outside, and 1 held the 
 fire brick lining in place by a header brick which extended 
 an inch or an inch and a half beyond the red brick. But I 
 was not able to follow it up properly and cannot give you 
 any data, because the question is too difficult, as IMr. Blein- 
 inger says, and it was a very insignificant trial to make. 
 But I believe if pottery companies will make up their minds 
 to pay a little more for hollow fire brick and put up their 
 kilns of them, it will be worth while. 
 
 Another question I wish to ask. In pointing out the 
 loss of fuel in firing, in the beginning, Mr. Bleininger says 
 that it is necessarily much greater than in a boiler. Is 
 that your idea? 
 
 Mi\ Blcimngcr: Yes, sir, not in the b(\iiinning so 
 much as later on. 
 
 Mr. Lajigcnhccl-. I can understand that the greatei' 
 the temperatures the greater the loss by radiation and 
 gases might be, but your statement might be subject to the 
 misinterpretation, as that a high temperature apparatus 
 like a kiln is more wasteful in its work than a low temper- 
 ature apparatus like a boiler. When we introduced gas at 
 the Mosaic Tile Co., it proved more economical to fire our 
 kilns with gas than with coal but not our boilers, and we 
 returned to coal for firing the boilers. The kiln as an 
 apparatus is much more economical of fuel, in my exper- 
 ience, measured by dollars and cents, than boilers, because 
 the latter in its work chills the fire gases below the com- 
 bustion temperature, the former does not. 
 
 Mr. Blewiiiger: I was referring to the effect pro- 
 duced. In the boiler you are getting effect measured by 
 water evaporation ; in the kiln, by the burning of the ware 
 to a certain temperature. From this standpoint it is more 
 economical than the kiln. 
 
 Mr. Langeuhecl-. I wanted to bring out what might 
 be misinterpreted in that point. 
 
A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 39 
 
 Mr. Wlieelcr: We certainly are deeply indebted to 
 Mr. I^leininger for this ver^^ valuable contribution, show- 
 ing what we do not knoAv. lie has put a magniticent 
 amount of work there, and the facts are very clearly and 
 concisely stated. 
 
 I will ask one ([ucstion to bring out one point more 
 clearly. Were those kilns selected under normal condi- 
 tions, with the common, everyday firing, «>r were they 
 s]){^cially tired by expert workmen, and vras there any 
 handling of the kilns? I will also ask Mr. Bleininger, in 
 that loss which he ascribes to radiation and kiln loss, 
 whether he attempted to r(Highly differentiate between the 
 external shell loss and what might be safely deducted as 
 not external radiation? If he could give us a hint on that 
 it wouhl be greatly appreciated. 
 
 J//". Blciniiu/cr: I have not attempted to do this. 
 r>ut in one case where the conditions were favorable, where 
 tlie air was being drawn out of the kiln by a fan, we at- 
 tempted to measure the heat retained in the kiln. We in- 
 serted a pyrometer and later on thermometers into the 
 goose-neck, and knowing the ])ressure exerted by the fan 
 we were able to roughly <alculate the velocity. I have not 
 finished the work, but we shall be able to calculate the 
 weight of the air and the temperature, and therefore 
 roughly the heat taken by the fan from the kiln. In other 
 plants the conditions have not been favorable. 
 
 Answering the first ([uestion, I will say that tlie con- 
 ditions were the ordinary ciuiditions, no expert help being- 
 employed. I asked the superintendents to take no special 
 precautions, but to let things go on in their usual way. 
 ^Ir. Merry can tell us how he found conditions. 
 
 Mr. Merry : As to whether the kilns were the average 
 or not, I think the sewer pipe kiln was the worst on the 
 yard. The others were about the average kiln. 
 
 Mr. Atihrey : I will ask Mr. Bleininger what he cal- 
 culates the heat retained by the ware? Is that heat taken 
 to perform the mechanical action in the clay ware? 
 
 Mr. Bleiningei^: The calculated heat includes that 
 
4'> A STUDY OF HEAT DISTRIBUTION IN FOUR INDUSTRIAL KILNS. 
 
 required for the expulsion of the mechanical water, the 
 raising of the heat of the clay itself from the atmospheric 
 temperature to the final temperature, and that taken by 
 the expulsion of the chemical water. We have no accurate 
 figures in regard to the heat of decomposition of the hy- 
 drous clay substances. I have assunied it to be 200 calories 
 per gram of such water. 
 
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