474
T H E J O U R N A L OF I i V D U S T R I A L A N D ENGINEERIA1;G C H E M I S T R Y
tion between F, T a n d S, which would be t h e most economical for producing a desirable clinker. S L-MMA R Y
I n attacking a problem such as t h e question of t h e constituents of P o r t l a n d cement clinker one must proceed in a systematic manner. After ascertaining which are t h e essential components, one must determine b y experiment just how these components combine under t h e particular conditions, a n d t h e n a t u r e a n d m u t u a l relations of t h e several compounds formed; this involves t h e investigation of t h e composition, t h e number a n d relation of t h e various crystalline forms of t h e several compounds, a n d their optical characteristics, as well as t h e s t u d y of t h e s t a t e of equilibrium reached b y mixtures of all compositions throughout t h e range of temperatures. One is t h e n able t o s t a t e precisely what will happen when a n y mixt u r e of t h e above three oxides is heated or cooled slowly (so t h a t equilibrium is continuously a t t a i n e d ) a n d t o indicate t h e course a n d final products of reaction when equilibrium is approached b u t not completely a t t a i n e d . T h e essential chemical components of P o r t l a n d cement clinker are lime, alumina, a n d silica, from a mixture of which i n t h e proper proportions a clinker, possessing all t h e properties of a desirable P o r t l a n d cement, can be made b y proper burning. Such a clinker will consist of t h e three compounds, 3CaO.SiOz, zCaO.Si02 a n d 3CaO.Al208; if, during t h e burning, complete equilibrium has not been reached-as happens in actual practice-there will be, i n addition t o t h e above three major constituents, t w o minor ones, v i z . , CaO a n d jCa0.3A1203. It has been argued b y some t h a t not even a n approximation of equilibrium conditions obtains in t h e actual manufacture of Portland cement, a n d hence t h a t conclusions derived from a s t u d y of t h e equilibrium diagram of t h i s system would have little or n o bearing on t h e question of t h e constituents of commercial clinker. I t m a y be contended t h a t equilibrium conditions are not a t t a i n e d in t h e burning of commercial clinker, b u t t h e Lxork o n actual clinkers already published from t h e laboratory of t h e Bureau of Standards, which was based upon t h e equilibrium diagram of t h e system Ca0-h1203-Si02, has disproved this contention. I n d e e d , one must conclude t h a t t h e nearer t h e approach t o equilibrium t h e better t h e reSultant cement, judging from t h e great stress which is now laid on fine grinding of t h e raw materials a n d from t h e lengthening o u t of t h e cement kilns-factors which, b y securing more intimate contact of t h e components a n d b y increasing t h e period of heating, obviously make for a nearer approach t o equilibrium. As t o how close a n approach t o equilibrium (perfect burning) is desirable or economically possible, i t is not as yet possible t o say from t h e d a t a available; these d a t a can be obtainpd, for a given raw mix, only b y investigation. Such a n investigation would necess i t a t e careful research t o determine t h e relation between time, t e m p e r a t u r e of burning, a n d fineness of grinding, of given r a v materials, in order t o produce
1-01. 7 . S o . 6
good clinker a t t h e lowest possible cost t o t h e manufacturer. Actual cement clinker contains small quantities of MgO a n d iron oxide, which are advantageous i n t h a t their presence during burning promotes t h e a t t a i n ment of equilibrium b y lowering t h e temperature a t which liquid appears (fluxing) a n d b y increasing t h e a m o u n t of such liquid; b u t t h e y v-ould seem-to judge from t h e available reliable evidence-to have little influence on t h e final main constituents of t h e clinker. This l a t t e r s t a t e m e n t , be i t noted, refers only t o t h e clinker, a n d implies nothing as t o whether such admixtures have or have not a beneficial influence on t h e cementing qualities of t h e product when mixed with water. Now t h a t t h e constitution of t h e clinker has been definitely established, i t is practicable t o a t t a c k t h e problem of t h e hydration of Portland cement; indeed t h e results of a n investigation along t h i s line have already been published from t h e Pittsburg laboratory of t h e Bureau of Standards.‘ By ascertaining precisely what happens on t h e hydration of each possible constituent of t h e clinker separately a n d in all t h e possible permutations a n d combinations, i t should finally prove possible t o determine t h e proportions of t h e various constituents which should be present in t h e clinker i n order t o produce a cement which on setting will possess t h e most desirable qualities, e . g., t h e greatest s t r e n g t h ; a n d from a s t u d y of t h e equilibrium diagram one can learn just how t o proceed i n order t o produce a clinker of t h i s o p t i m u m composition. I n conclusion, i t m a y be remarked t h a t t h e effect of admixture of other materials can be definitely ascertained only b y t h e systematic, a n d somewhat laborious procedure described above; such a procedure, nevertheless, will lead sooner t o t h e discovery of t h e o p t i m u m composition i n various cases a n d for various purposes t h a n t h e empirical or cut a n d t r y method which hitherto has been t h e only method tried. GEOPHYSICAL LABORATORY CARNEGIE INSTITUTION OF WASHINOTON W A S H I N G T O X , D. c.
THE FUSIBJLITY OF COAL ASH I N VARIOUS ATMOSPHERES By A. C. FIELVSER A N D A.
E. HALL
(Concluded from May i s s u e ) E-MOLYBDENUM
PURXACES I AXD
2
I n order t o s t u d y t h e fusibility of ash i n a n atmosphere of hydrogen, a molybdenum-wire resistance furnace3 was built as shown in Fig. 9 . T h e maximum safe working temperature of this furnace was ample for softening a n y ash. At 17jo” t h e alundum t u b e carrying t h e molybdenum wire began t o soften perceptibly. T h e furnace was operated with alternating current from a transformer having a number of leads from t h e secondary connected t o a switchboard, SO t h a t b y a suitable manipulation of switches t h e voltage 1 “Hydration of Portland Cement,” by A . A. Klein and A. J. Phillips. No. 43, of the Technologic Papers of t h e Bureau of Standards. 2 Published by permission of t h e Director, U. S . Bureau of Mines. 3 Winne, R., and Dantsizen, C., “Small Electric Furnace with Heating Element of Ductile Tungsten or Ductile Molybdenum,” THISJOURNAL, 3 (1911). 7iO-i71.
June.
191j
T H E J O L 7 R S d L OF I S D C S T R I A L A X D ESGISEERIiVG CHEMISTRI' QPPAREXT
the furnace be varied f r o m to in s t e p s of 2 volts. A field 'rheostat i n series with t h e furnace was used for closer regulation: z t o 2.3 K . lr.A. were required t o heat t h e furnace t o 1600' C. T h e front of t h e furnace was water-jacketed t o prevent overheating t h e rubber gaskets a n d insulation surrounding t h e electrodes. Hydrogen' was a d m i t t e d from a t a n k through a reducing valve a n d a wash bottle of concentrated sulfuric acid, t o t h e interior of t h e furnace a t t w o points. During operation, t h e rate of flow was just sufficient t o sustain a small flame a t t h e upper exit a t t h e rear of t h e furnace. Any water collecting in t h e furnace was drawn off a t t h e b o t t o m of t h e exit t u b e . T h e heating space (1l,'4 in diameter X 1 2 in. long) afforded a very uniformly heated portion approximately 4 in. long. Hack of t h e center t h e t u b e was closed b y 4 t h i n disks of a l u n d u m . T h e ash cone was placed in a No. j 8 I I a l u n d u m extraction thimble (~l,'g in. diameter X 3 in. long) which was t h e n pushed back t o a distance of r,l q- in. from t h e first a l u n d u m On
TEMPERATURE (CEXTIGRADE)
475
BY W A N N E R PYROMETER
Without glass , , . . . . . . , . . . , . , , . . . . . 1080 1185 1287 1380 1486 Withglass , . . , . . . . , , . , . , . . , . . , . . . . 1068 1170 1267 1360 1462 Difference . . . . . , . . , . . . . . . , . . . _ . ., -12 -15 -20 -20 -24
All results given are corrected for glass according t o t h e above table. T h e order of accuracy of t h e temperat u r e readings is shown b y t h e following a p p a r e n t melting points obtained on thin strips of Kahlbaum's pure copper a n d nickel, which were mounted i n t h e same position as t h e ash cones: COPPER(hl. P. = 1083' C ) Apparent Date meltine - Doint . 5 1 5/13 1084 9/23/13 1088 11,/ 6/13 1084 12/ 1/13 1082 1/12/14 1080 1088 5 1 5/14 1096 6/ 9/14 10/ 6/14 1088 11/ 3, 14 1080
NICKEL (>I. P = 1450' C . ) Apparent Date melting point I O / 1/13
12/ 11/
6/13 1/13 1 / 5/14 2/12/14
3/18/14 4 / 9/14 6 1 4/14 1 1 / 3/14
1451 1440 1448
I n operating t h e molybdenum furnace, a rapid curr e n t of hydrogen was a d m i t t e d until on ignition at t h e exit t u b e i t burned with a s t e a d y flame. T h e hydrogen current was t h e n reduced t o 3 bubbles per sec. through t h e sulfuric acid bottle a n d the heating current t u r n e d on. temperature of 900 O was reached in approximately I h r . ; t h e t e m perature was t h e n increased a t t h e r a t e of 10' per minute t o a point not less t h a n z o o o below t h e probable softening point, a n d thence at a predetermined r a t e of 2 , j, or 10' per min. as desired, until t h e cone was down. SERIES I , comprising all t h e softening points determined in molybdenum furnace N o . I: is given in Table V I I I . JOINTS OAI Since t h e heating space was only 4',l1 in. high, the in. X I ~ , ~in. ? cone could not be used i n this -I7 ___ furnace without cutting F I G . MOLYBDENUM FURNACE off in. at t h e base. disk a s shown i n Fig. 9. It was necessary so t o a d - This made a cone of 3,'16 in. base X I in. high which just t h e distance of t h e cone from t h e back of t h e gave slightly lower softening points t h a n t h e l / 4 in. X capsule t h a t a slight difference of temperature existed I in. cone; however, t h e average difference of 11' between t h e m , otherwise t h e cone became invisible. is quite negligible i n comparison with other factors. T h e t e m p e r a t u r e measurements were made with a S E R I E S 2-Molybdenum furnace No. 2 was built Wanner optical pyrometer. T h e correction for t h e i n t h e same manner as No. I . On repeating some of glass used i n t h e observation window was determined t h e tests t h a t h a d been made i n furnace K O . I, it was a t various t e m p e r a t u r e s between 1000 a n d 1 5 0 0 ~C. found t h a t considerably higher softening points were This was done b y observing t h e a p p a r e n t t e m p e r a t u r e being obtained, although all t h e t e s t conditions were of a n a l u n d u m disk i n a p l a t i n u m resistance furnace, a p p a r e n t l y t h e same as before. T h e entire series was, with a n d without interposing t h e glass, t h e tempera- therefore, repeated, with t h e result t h a t most of t h e t u r e of t h e disk being kept c o n s t a n t during t h e t w o samples softened a t from 50 t o 100' higher t h a n i n readings a s indicated b y a thermo-element embedded Series I ; in 4 samples of r a t h e r high iron content t h e in i t . T h e following corrections were observed: softening point was raised 2 0 0 ~ . ALL
+
99.8 per cent hydrogen and 0.2 per cent (COS by G . A . Burrell and G . G . Oberfell.
0 2
+ Nt)-Analysis
AUTOOLNOVSLY WLLOLO
TIGHT
T h e cause of t h i s variation was finally traced t o
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
476
a difference in t h e a m o u n t of water vapor present with t h e hydrogen i n t h e furnace atmosphere. Considerable trouble was experienced from water collecting i n the hydrogen exit pipe of t h e No. I furnace. Moist u r e also collected i n t h e water-cooled observation t u b e a t t h e front of t h e furnace. After rebuilding t h e furnace little or no condensation of water was noticed. T h e effect of a larger proportion of water vapor i n TABLEVIII-COMPARISON OF SOFTENIRG TEIPERATURES OBTAIKEDIN MOLYBDENUM FURNACE KO. 1, USING T W O SIZES O F CONES-SERIES 1 R a t e of heating, 2' from vertical
per minute: 100 mesh ash: cones inclined 35'
SOFTENING POINTIN
Cone 1 in. X 1 in. Ash No. Duplicates 1 1123 . . 2 . . . . . . . . . . 1430 , . 3 . . . . . . . . . . 1444 1470 4 . . . . . . . . . . 1227 . . 5 . . . . . . . . . . 1234 . . 6 . . . . . . . . . . 1350 , . 7 . . . . . . . . . . 1580 1600 8 . . . . . . . . . . 1318 . . 9 . . . . . . . . . . 1213 , . 1 0 . . . . . . . . . . 1185 , . 1 1 . . . . . . . . . . 1220 . . 1 2 . . . . . . . . . . 1068 , . 1 3 . . . . . . . . . . 1217 , . 14. . . . . . . . . . 1320 1331 1 5 . . . . . . . . . 1167 . . 1 6 . . . . . . . . . . 1241 , , 1 7 . . . . . . . . . . 1192 , . 1 8 . . . . . . . . . . 1199 , , 19. . . . . . . . . . 1562 . . '/a
..........
Vol. 7, No. 6
difference being IO'. T h e average difference of duplicate determinations (24') was practically t h e s a m e a s was obtained with t h e ' 1 4 in. X 1'/2 in. cones i n t h e various furnaces previously described. SERIES 3-Here t h e test conditions were changed b y grinding t h e ash t o a n impalpable powder instead TABLEX-COMPARISON OF SOFTENINGTEMPERATURES OBTAINED IN MOLYBDENUM FURNACE N O . 2 AT T W O DIFFERENTRATESO F HCATINGSERIES 2 , in. X 1 in. cone inclined 35O f r o m vertical DifferDifference of SOFTENING POINTIN O C . ence of average 2O r a t e duplivalues cates 5' a n d Ash No. 5' r a t e Duplicates Av. 2' r a t e 2' rates 1340 . . 1340 .. 1492 1502 i6 1497 1414 , . 1440 1414 .. +26 3 1440 . . 1440 4 .. 1263 1304 .. li92 1309 . . 46 4x. . . . . . . . . 1234 1248 . . 1248 .. -14 1448 1445 . 1445 .. + 3 1402 , , 1414 1402 .. 12 1410 1380 1395 30 1520 1516 4 1518 8. . . . . . . . . . 1375 1441 .. 1421 1435 1434 66 .. 9 1248 1248 1248 0 .. 10.. . . . . . . . . .. 1294 1283 1304 21 .. 11 1335 1360 25 1348 .. 1271 12.. 1271 1271 0 12x.. . . . . . . . 1402 35 1363 1345 1380 +39 13 . . . . . . . . . . 1283 1271 1295 24 1 3 x . . . . . . . . . 1390 1380 1380 . . +io 14. . . . . . . . . . 1350 1402 1376 52 .. 1295 1300 1331 1316 31 -2 1 1271 1260 1266 11 1402 .. 22 1380 . . 1380 16.. . . . . . . . . 1322 1336 14 1330 .. 16x . . . . . . . . . 1345 .. -15 1360 . 1360 17.. . . . . . . . . 1241 1245 4 1243 1 7 x . . . . . . . . . iiko 1295 . . .. 65 1295 18.. . . . . . . . . 1279 1263 1271 16 18x. . . . . . . . . 1287 .. '8 1279 . . 1279 19.. . . . . . . . . 1521 38 1540 1502 .. - 6 1621 20. . . . . . . . . . i 6 i 5 .. 1621 21 . . . . . . . . . . 1601 1615 1615 -14 .. 2 3 , . . . . . . . . . 1520 1474 , . 1474 .. +46 2 5 , . . . . . . . . . 1173 1167 1167 .. + 6 3 0 . . . . . . . . . . 1355 1350 . .. 1350 + 5 1313 31 1258 1258 +55 1365 32 1340 . 1340 +25 1390 33 1380 1380 . 10 1463 , . 3 5 . . . . . . . . . . 1470 1463 + 7 1300 , , 1300 3 6 . . . . . . . . . . 1309 + 9 3 7 . . . . . . . . . . 1300 1295 . , 1295 + 5 38. . . . . . . . . . 1304 1291 . . 1291 13 3 9 . . , . , . , . , . 1295 1291 , , 1291 + 4 1350 , , 1350 40 . . . . . . . . . . 1360 10 1365 , , 1365 41 . . . . . . . . . . 1370 + 5 1340 , , 1340 42 . . . . . . . . . . 1345 + 5 - 6 4 3 , . . . . . . . . . 1328 1334 . . 1334 0 1328 44 . . . . . . . . . . 1328 1328 . . .. 1322 . . .. 1322 45. . . . . . . . . . 1331 + 9 1338 , . .. 1338 4 6 . . . . . . . . . 1340 + 2 - 7 1335 . . .. 1328 1335 47.. . . . - 3 .. 1353 48.. . . . 1353 . . 1350 100 mesh a s h ;
8/18
--
O C .
Cone 3 X 1 in Duolicates 1123 . . 1417 . . 1396 , , 1248 1220 1241 1220 1340 1331 1580 1580 1263 . . 1199 , . 1192 , . 1220 , . 1060 . , 1217 . . 1300 1331 1161 . . 1241 . . 1179 , , 1185 . . 1558 1558 %/E in.
..
. . . . . . . . . . .. ..........
..
..
.
+
.......... .......... ........
..
t h e hydrogen atmosphere of furnace No. I would be to r e t a r d t h e formation of metallic iron t o a greater e x t e n t t h a n in furnace No. 2 . Consequently more ferrous oxide would be available t o lower t h e softening t e m p e r a t u r e of t h e ash in t h e first series. As shown in Fig. I O , t h e large,st differences occurred in Samples 1 2 , I, 5 a n d 8 containing 36, 33, 19 a n d 18 per cent
+
+ +
.. ..
.. . ..
..
+ + +
A3 ?.r(."f
I
OF THREE SERIESOF SOFTENINGTEMPERATURES ( a ) Intrinsic ash OBTAINEDIN MOLYBDSNUM FURNACE,SHOWING EFFECT OF WATER VAPOR
FIG. 10-COMPARISON
ferric oxide, respectively. T h e smallest differences were usually found with those samples which contained 7 per cent or less of ferric oxide. T h e above deductions were further verified b y examining polished sections of t h e fused cones under t h e microscope; in general, more metallic iron was visible i n Series 2 , t h a n i n t h e corresponding cones of Series I . Also, some of t h e fused cones from b o t h series were pulverized a n d analyzed. T h e results are given in Table I X . TABLE IX-PERCENTAGES OF IRON IN CONESFROM SERIES 1 Percentages Fe-Series 1 Metallic Ferrous Ferric 1. . . . . . . . . . 13.9 10.3 1.6 7.1 None 4 .......... 1.4
Ash No.
ARD
2
Percentages Fe-Series 2 idetallic Ferrous Ferric 19.1 18.2 Trace 2.2 6.1 None
All t h e softening points determined i n Series 2 are reported i n Table X. Heating a t t h e r a t e of j' per minute t e n d s t o give somewhat, higher softening points, t h e maximum difference being 6 j ' a n d t h e average
-
Average,
24
-
+10
of IOO mesh, a n d b y mounting t h e cone i n a vertical ' . position instead of a t a n inclination of 3 j T h e softening temperatures obtained on heating a t rates of I O , 5 a n d 2' per minute are given in Table XI. T h e average difference between a j' a n d '2 r a t e of heating was 12' as compared with 10' in Series 2 . Heating at t h e r a t e of I O ' per minute caused a n average increase of 40' i n t h e softening point over t h a t obtained with a 2' rate. I n Table XI1 a n d Fig. I O is given a comparison of t h e three series of softening-temperature determinations made i n t h e molybdenum furnaces a t a 2 r a t e of h e a t ing. T h e average difference of 110' between Series I a n d 2 is a t t r i b u t e d t o t h e higher proportion of n-ater vapor i n Furnace I which retarded t h e reduction of ferrous oxide t o metallic iron. The average increase of 2 I ' of Series 3 over Series 2 is exactly t h e same as t h e average increase of t h e softening interval,' i. e . , 1
Difference in temperature of initial a n d of final deformation point.
June, 1 9 1 s
T H E J O C ' R S A L O F I S D I - S T R I A L A-TD E S G I S E E R I X G C H E M I S T R Y
the temperatures of initial deformation were the same in both series. Therefore, the 'higher results of t h e last series seem t o be largely due t o placing the cone in a vertical position, rather t h a n t o t h e finer grinding TABLEXI-COMPARISON
OF SOFTENING TEMPERATURES OBTAINEDIN MOLYBDEKUM FURNACE No. 2, A T THREE DIFFERENTRATESOF HEATING-SERIES 3 Ash ground t o a n impalpable powder; 3 i 1 6 in. X 1 in. cone placed in a vertical position Difference in ...........~ average values SOFTENING POINTIN OC. Difference IOo 5 O R a t e per minute in duplicates a n d an$ 4sh !ao 50 20 50 20 20 2 ~
1
1562
4 5
1460 1409 1502 1421 1540
6 4
10
11 12 13 14 15 16 17 18 19
39 42 33
1380 1390 Av. 1385
1365 1355 Ay.-!;66"-,1 3 L U ISUL
-
3
.
1382 1414 Av. 1398
1520 1365 1380 1402 1322 1402 1427 1300 1380 1295 1340 1540
IS20 1414 1360 1462 1402 1502 1486 1470 A ~ 1478 . 1313 1375 Av, 1344 1340 1427 1300 1350 1402 1291 1380 12il 1340 1520 1525 Av. 1523 1271 1318 1390
Av. 1511 1440 1414 Av. 1427 1355 1455 1414 1502 1478 1470 A". 1474 1313 1331 1322 1331 1322 1295 1340 1375 1283 1370 1271 1287 1520 1502 Av. 1511 1283 1313 1390 Average,
+ 25 + 9 - 13 + + 57
10
10
f38
..
18
+5l
26
f3.Z +54 +47 +7-12 +38
o
+46
-
4
i43
+ 22
16
8
62
$+27 : + +62 +
+52 +I7 +io +24 +53
5
+29
l8
. . .-. 23
16
5
++ 27108 + io + 530 2 +
iz 5
-. . _ 0 4-40
4-12
of t h e ash. A vertical cone would have a larger bending interval t h a n one inclined 35' from t h e vertical. T o obtain further information on t h e relative effect of fineness of ash a n d inclination of cone, two special series of experiments mere made in which only one of these factors was varied a t a time. T h e d a t a obtained are given in Tables XI11 a n d XIV. TABLE XII-COMPARISON OF SOFTENING TEMPERATURES OBTAINEDIX MOLYBDENUM FURNACES 1 A N D 2, SHOWING EFFECT OF WATERVAPOR ASD INCLINATION OF CONE R a t e of heating was 2' per minute SERIESI-Molybdenum furnace No. 1; 100 mesh ash; 8/18 in. X 1 in. cones inclined 35O from vertical position. W a t e r collected in exit tube of furnace. SERIES2-Molybdenum furnace No. 2; 3/18 in. X 1 in. cones inclined 35' from t h e vertical position; 100 mesh ash. No water in exit tube. SERIES 3-Molybdenum furnace N o . 2 ; ash ground t o a n impalpable powder: cones in vertical position. N o water in exit tube. SOFTEKINGPOINT IN OC. 100 mesh Difference in Average Series 1 Series 2 Powder average values softening interval Furnace S o . Series 3 between series in OC. for series Ash S o . 1 2 Furnace 2 1 & 3 2&3 1 2 3 11 . . . . . . . . . 1123 1355 -232 -15 92 1511 . . . . . . . . . 1417 - 94 -14 27 96 46 . . . . . . . . . 1396 1427 - 31 h9 13 -63 -121 . . . . . . . . . 1234 55 39 1355 28 -235 -10 . . . . . . . . . 1220 I15 1455 - 7, I6 . . . . . . . . . 1340 1.9 34 40 1414 1502 78 68 . . . . . . . . . 1580 29 +I6 1263 1474 -21 1 -53 64 29 1322 9 . . . . . . . . . . 1199 -123 24 91 -74 10. . . . . . . . . . 1 I92 1331 -37 9 -139 13 1322 1 1 . . . . . . . . . . 1220 26 50 51 -102 12. 20 147 1060 1295 -24 -235 -123 -5 7 13. . . . . . . . . . 1217 25 49 1340 54 88 1 4 . . . . . . . . . . 1316 22 -. 1375 + I 1 5 . . . . . . . . . . 1 I61 -122 -17 49 34 1283 -129 16. . . . . . . . . . 1241 -40 1370 48 33 I , , . . . . . . . . . 1179 1271 - 92 -28 12 30 -16 18. . . . . . . . . . 1185 15 28 1287 -102 19. 1511 -I- 47 26 103 1558 +IO
+
+
-
.........
-
-
Average,
-110
-21
28
42
63
E F F E C T O F F I N E X E S S O F ASH-The effect O f grinding t o a n impalpable powder was barely appreciable in a n average reduction of 6 " in t h e softening points of the series. T h e principal advantage of finer grinding was in obtaining a more plastic and intimate mixture
477
which could be molded into more substantial cones. E F F E C T O B I S C L I X A T I O X O F cosE-The effect of varying the position of the cone from vertical t o an inclination of 4 j O was more appreciable, giving in some cases a lowering of 6 4 " in t h e softening point. TABLEXIII-EFFECT OF FIKENESS OF ASH Molybdenum furnace No. 2; 3 / 1 6 in. X 1 in. cone in a vertical position R a t e of heating, 2' per minute SOFTENINGPOIXTIX "C. SOFTEKING POINTIN "C. Ash Ash No. 100 Mesh Powder Diff. No. 100 Mesh Powder Diff. 39 . . . . . . . . . . 1291 1283 6 7 . . . . . . . . . 1223 1185 4-38 8 9. . . . . . . . . . 1248 1304 -56 68 . . . . . . . . . 1216 1205 +11 42 . . . . . . . . . . 1340 1313 +27 69 . . . . . . . . . 1251 1237 +14 48 . . . . . . . . . . 1380 1390 -10 7 0 . . . . . . . . . 1259 1263 - 4 8 . . . . . . . . . . 14.35 1481 -46 71 . . . . . . . . . 1327 1300 + 2 i 19 . . . . . . . . . . 1519 1510 9 72 . . . . . . . . . 1368 13.50 + I 8 2 . . . . . . . . . . 1492 1520 -28 7 3 . . . . . . . . . 1380 1370 + I O 64 1108 1101 8 65 . . . . . . . . . . 1155 1127 +28 Average. 6 66. . . . . . . . . . 1174 1173 1
+
+
..........
+ +
+
-4 slight inclination of not t o exceed z j" gave t h e same result as a vertical cone. T h e most satisfactory indication was obtained b y mounting t h e cone with one side vertical, which usually caused t h e cone t o bend towards t h a t side. An important objection t o mounting t h e cone a t a n y considerable inclination, as 35 or 45', is t h a t certain ashes shrink before t h e y reach TABLE XIV-EFFECT OF INCLINATION OF CONES Molybdenum furnace No. 2 ; 8/18 in. X 1 in. cone; ash ground t o a n impalpable powder; r a t e of heating. 2' per minute SOFTENING POINT IN O C . Difference Inclined from vertical Vertical 45 O and 25 and Ash No. 45 25' position vertical vertical 39 . . . . . . . . . . . . . . 1287 1283 1283 4 0 1304 42 . . . . . . . . . . . . . . 1295 1313 -9 +9 9 . . . . . . . . . . . . . . . 1248 1304 1313 -65 -9 33 . . . . . . . . . . . . . . 1396 1390 6 0 1390 1478 8 . . . . . . . . . . . . . . 1414 1481 -44 +3 19 . . . . . . . . . . . . . . 1494 1510 1502 -8 +8 0 0 2 . . . . . . . . . . . . . . 1520 1520 1520
+
+
-
Average,
-19
-
+2
their softening temperature which allows the cone t o fall over t o a still larger inclination and t h u s indicate a premature down point. EFFECT OF D E X T R I S BINDER-The results O f a few experiments made t o show t h e effect of not burning o u t the dextrin binder before placing t h e ash cone in the molybdenum furnace are given in Table XV. TABLEXV-EFFECT OF DEXTRINBIKDER Molybdenum furnace KO.2; 3/10 in. X 1 in. cone inclined 35' from vertical; 100 mesh a s h ; r a t e of heating, 2' per minute SOFTENING P O I X T IN
Ash N o 2........................... 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. . . . . . . . . . . . . . . . . . . . . . . . . . . 8. . . . . . . . . . . . . . . . . . . . . . . . . . . hTo. 8 No. 8
+ I per cent d e x t r i n . , .
h'ot ianited 1492 1260 1435 1430
O
c.
Ignited a t 850' C. Difference 1502 -10 1271 -1 1 1434 + I 1434 - 4 Average,
., - 10 per cent d e x t r i n . . . . . . . ,, ,
-6
1427 1420
T h e maximum apparent effect was a lon-ering of 1 1 " in t h e softening point. LIising I O per cent of d r y dextrin n i t h the ash caused a reduction of only 14'. HoTvever, the conclusion t h a t dextrin causes no material effect would apply only under t h e condition of determining t h e softening point in hydrogen and water-vapor mixtures as n-as done in t h e above cited experiments. EFFECT OF COMBINED j o AXD 2 '
R A T E O F HEATIXC,-
A series of tests n-as made in which t h e furnace t e m perature was increased a t t h e rate of 5' per min. until deformation began. The rate v-as t h e n reduced t o z o per min. until the cone was down. As shown by
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
478
Table X V I . t h e results approximate those obtained TABLEXVI-COMPARISONOF SOFTENIXG TEMPERATURES OBTAINED IN MOLYBDENUM FURNACE No 2, AT Two DIFFERENT RATESOF HEATIXG Ash ground t o a n impalpable powder; 8/16 in. X 1 in. cone in vertical position SOFTENING POINTI X OC. r a t e until 2O per deformation began min. until then 2' r a t e until Ash No. cone was down cone was down Difference 5 8 . . . . . . . . . . . . . . . . . 1199 1220 -2 1 50. . . . . . . . . . . . . . . . . 1220 1217 t- 3 49 . . . . . . . . . . . . . . . . . 1520 1514 + 6 _m . . . . . . . . . . . . . . . . . 1380 1370 f10 2 8 . . . . . . . . . . . . . . . . . 1390 1.394 - 4 52 . . . . . . . . . . . . . . . . . 1448 1478 -30 61 . . . . . . . . . . . . . . . . . 1365 1370 - 5 Average,
-6
with t h e usual z o rate. T h e combined r a t e has t h e advantage of shortening t h e time of a determination. F-P
LA TI K U M R E SI S T A N C E F U R 1;A C E
All t h e foregoing softening temperatures were determined i n atmospheres which h a d more or less reducing action on t h e ferric oxide in t h e ash. This reduction was probably least in t h e Meker furnace. It would have been possible t o direct a stream of air 'through t h e muffle chamber a n d t h u s remove a n y furnace gases which penetrated through t h e walls of t h e muffle. Such a procedure, however, would still leave some
/h
FIG.1I-sECTION T H R O U G H PLATINUM RESISTANCE FCRN.4CE k, Heraeus tube furnace, t y p e B ; e , porcelain tube, 2 6 s inch inside diameter, 12 inches long, wound with platinum-foil heating element; n , alundum tube, 11!2 in. inside diameter, 6 in. long, 3 1 8 in. wal!; c, 17 f t . of 3'100 in. diameter platinum wire wound on t h e inside of t u b e n , six t u r n s t o t h e i n c h in t h e middle a n d closer a t t h e ends t o partly compensate for radiation a t t h e ends; 6 , alundum extraction thimble No. 5811, 30 mm. diameter, 80 mm. long; j , i , g a n d I t , alundum disks; 0, observation hole; f, P t - P t R h thermo-element; a , ash cone.
d o u b t a s t o t h e complete removal of all traces of reducing gases. Therefore, a special platinum-Fire resistance furnace (Fig. 1 1 ) was built i n which there could be no question as t o reduction, a n d in which accurate temperature measurements could be made. T h e essential feature of t h i s furnace is t h e platinumwire resistor (c) wound on t h e inside of t h e alundum t u b e ( n ) , which is t h e n placed i n t h e heating t u b e of a s t a n d a r d I Io-volt Heraeus platinum-resistance furnace, a n d t h e t w o heaters connected i n series. By t h i s arrangement it was possible t o a t t a i n a maximum temperature of 1500' C., repeatedly, without endangering t h e heating elements. A constant current of 1 2 . 5 amperes heated t h e furnace from 30 t o 1450' in 63 minutes. During this interval t h e e. m. f . across t h e furnace terminals increased from 3 2 t o 109
Vol. 7 ,
KO.6
volts. T h e temperature of t h e space between t h e two heaters reached I 100'. T h e inner heater was built b y winding t h e platinum wire on 2 solid wood mandril 1 l / 4 in. i n diameter, with six t u r n s t o t h e inch i n t h e middle a n d closer a t t h e ends. T h e wire was t h e n covered with a smooth coating of alundum cement, a n d t h e whole inserted i n t h e alundum t u b e 71. T h e space between t h e wire and t u b e vias filled with cement. After drying slowly, t h e wood mandril was burned out i n a muffle, a n d t h e exposed platinum wire covered with a t h i n slurry of alundum cement. T h e temperature measurements in this furnace were more accurate t h a n those i n a n y of t h e others previously described, a s shown b y t h e following considerations: I-The reading error of t h e thernio-element a n d millivoltmeter is less t h a n 3' as compared with j t o I 5' in Wanner optical pyrometers. 2-Xo reducing gases being present. t h e bare h o t junction of t h e thermo-element could be placed very near t h e cone. 3-The temperature did not vary more t h a n j o for a distance of I inch on all sides of t h e cone, as was shown by exploration with t h e thermo-element. 4--.4 small crystal of pure diopside was placed on a sheet of platinum in t h e position usually occupied b y t h e cone, a n d t h e furnace heated t o 1387' as indicated b y t h e thermo-element. After I O minutes t h e crystal was removed from t h e furnace a n d found TABLEXVII-COMPARISONOF SOFTENING TEMPERATURES OBTAINED IR THE PLATINUM RESISTANCE FURNACE AT THREEDIFFERENT RATES O F HEATING-SERIES1 Atmosphere of air; 100 mesh a s h ; 3/18 in. X 1 in. cone inclined 35' from vertical Difference In averDiff. in age values SOFTENIXG POINTIN ' C dupli10' 5" IOo 5 O 2Oper min. rate cates and anod Ash No. rate . r a t e DuDlicates Av. 2Orate 2' 2 1. . . . . . . . . . . . . .. . . 1363 1367 1365 4 4(b). . . . . . . . . . .. . . 1160 1140 1150 20 1380 1385 1383 5 4. . . . . . . . . . . . . 1450 .. ii + ' 6 5 ( a ) . . . . . . . . . . 1465 1456 1450 1435 i i i o 1433 5 5. . . . . . . . . . . . . 1395 . . ti0 i6 6 ( a ) , , , . , . , , . . i 4 i 5 i 4 i i 1395 2 1435 1437 1436 .. 8. . . . . . . . . . . . . 20 .. 1405 1385 1395 9. . . . . . . . . . . . . 1300 1280 1290 20 10 . . . . . . . . . . . . . 1270 .. ;io +ii lO(a). . , . , . , , , . 1300 I302 1270 10 1385 13;s 1380 11 . . . . . . . . . . . . . 1330 1320 1325 10 1 2 . . .. . . . . . . . . . 0 1380 1380 1380 1 5 . .. . . . . . . . . . . 3 1300 1303 1302 16.. . . . . . . . . . . . 0 +'i +'i 1 6 ( a ) . . . . . . . . . . i3io i3io 1303 1303 1303 22 1335 1313 1324 17. . . . . . . . . . . . . .. 1273 +32 l i ( a ) . . . . . . . . . . l i 9 4 1365 1273 25 .. 1370 1345 1358 .. 18.. . . . . . . . . . . .
+
..
. . + ..
+ii
-
-
lo +G i-19
Average, (a) A second sample from t h e same lot of coal. ( b ) Intrinsic,ash, from coal t h a t floated on a zinc-chloride solution of 1.35 specific gravlty.
unchanged. It was t h e n replaced i n t h e furnace a s before a n d t h e temperature held a t 139zOfor I O minutes. On removal from t h e furnace t h e diopside was melted into a glassy globule. Since t h e melting point of diopside is 1391O , t h e temperature measurement was correct t o within jo. Following t h e same procedure as i n t h e molybdenumfurnace experiments, two series of tests were made in t h e platinum furnace. I n Series I , Table X V I I , t h e ash was ground t o I O O mesh a n d molded i n t o 3/16 in. X I in. cones which were inclined 35' from t h e vertical.
T H E J O C R S A L OF ISDLTSTRIAL A N D ESGISEERI-VG CHEMISTRY
J u n e , 191j
I n Series 2 , Table X V I I I , t h e ash was ground t o a n impalpable powder a n d t h e cones were niounted in
ences range from 143 t o 4 2 5 ' C. I n 13 samples which softened below I jooo in t h e platinum furnace, 8 gave
TABLEX V I I I - C O X P 4 R I S O N
OF S O f T E U I b G TEMPERATURES OBTAINED IN P L A T I ~ U V R E S I S T A h C E F L R N A C E AT THREE D I F F E R E N T RATES OF H~~TIKG-SERIES 2
Atmosphere of a i r , ash ground t o a n impalpable powder 3 i o in X 1 in cone placed 111 a ~ e r t i c a position l S O f T E N I h G POIKT I N ' C Difference between rates R a t e s per minute 100 5' 2O 1O0andZ0 5Oand2' Ash S o 1 1382 1380 1365 +17 +I? 4 1405 1405 1400 t 5 + J 5 1490 1490 0 6 1475 1470 1458 +li 12 8 1460 1460 1450 ~ 1 0 10 + 5 9 1440 1430 1425 +15 10 1320 1313 1310 +in + 3 11 1398 1400 1400 -2 0 12 1390 1375 1315 +70 +55 13 1500 15 1407 1407 1407 0 0 1330 1333 1322 8 +I1 1335 1345 1343 -8 - 2 18 T 5 + 5 1405 1405 1400
++
+
;:
-_
Alerage
~
-r 9
-12
a vertical position reported in Table X I X , the effect of grinding t o a n impalpable powder a n d mounting t h e cones vertically was t o increase t h e 1603
IS50
L t
1y13
1450
15W 6 Y
1450
8 1400
B0
$5:
1350
IO
I
I7
12
16
11
4
15
18
9
FIG.13-EFFECT
S
Of
RATE O f HEATING ON TURE I N AIR
TllE SOFTENING
TEMPERA-
their highest results in t h e strongly reducing carhonmonoxide atmosphere of t h e Northrup furnace (see Fig. 1 3 ) ;a n d five gave their highest results in t h e oxidizing atmosphere of t h e platinum furnace. TABLEX X - C O M P A R I S O N
OF
SOFIEWING
TEMPERATURES OBTAINED
IN
DIFFERENT FI:RSACES SHOWISG EFFECT OF 1-ARIOVS ATMOSPHERES R a t e of heating, 2O pcr minute SOFTEKISG POIKT IN O C . Powdered 100 mesh ash 114'' X 1 1 . 2 " ash 3 ,la'' X 1" Cones inclined 35' from vertical C o n e s Vertical position Furnace Carbon Molybdenum Muffle Meker PlatAsh C O + No. 2 No. 1 A i r f c o m - IYorthrup inum Max. XO. COnJ-5H H?+H?O bustion gases C O + K Air Diff. 1 . . . . . 1040 1360 1123 1191 .. 1131 1365 275 1645 Above 228 2 . . . . . I593 1511 1417 .. ., 1500 166 1502 Above 3 . . . . . I562 1427 1396 .. , ,
."""
i5nn
4.....
6. . . . . 7.....
1306 1356 lli9 1638
1355 1455 1414 1502
1234 1220 1340 1580
1226 1320 1318
1305 1376
S..... 9..... 10 . . . . . 11 . . . . . 12 . . . . . 13 . . . . . 14 . . . . .
1166 1249 1167 1139 1088 1322 1424
1474 1322 1331 1322 1295 1340 1375
1263 llY9 1192 1220 1060 1217 1316
1251 1284 1199 1214 1182
1343 1318
15 . . . . . 1250 16 . . . . . 1341 17 . . . . . 1220 18 . . . . . 1250
1283 1370 1271 1287
1161 1241 I179 1185
5.....
1350
..
..
_.
1.360 1645 1455 1645
1400 1490 1458 .4bove 1500 1450 142.5 1310 1400 1335 1500 Above 1500 1407 1322 1343 1400
Llm I7
6
8
ASH NUMBER
IW
t:
479
15
L8
12
II
9
10
I3
L
I
II
6
1.
1
5
e
2
7
19
*s* *UMBER
FIG 12-EFFECT
Of
R~TE O F HEATING ON
THE S O F T L N I N G
TURE I N A X ATMOSPHERE OF
TEVPERA-
HYDROGEN
average softening point of Series 2 , 19 a n d t h e average softening interval I I ' T h e largest deviation in dupliO ,
TABLEX I X - c O M P A R I S O I OBTAINCD I h
.. .. .. .. .. ..
1253 1417
I562 1440 1385 1185 1080 1520 I551
1186 1212 1182 1204
1427 1470 1390 1455
.. ..
174 425 279 143 395 241 218 261 276 303 235 264 258 211 270
Of T R O S E R I E S O F S O F T E N l h G TEMPERATURES PLATIhLM R E S I S T A h C E F U R F A C E SHOWIhG E f f E C T O f I U C L ATIOV I~
R a t e of heating 2 " per minute, 3 16 in X 1 in cones SOBTEAING POINT I\ OC Series 1 100 mesh Series 2 ash cones Powdered Av softening inclined ash interval OC Diff i n a v values 35' from Cones Series Series Ash S o Iertical vertical 1 2 1and2 1 . . . . . . . . .. . . . 1365 45 65 0 4......... 30 1383 48 -17 5......... 50 .. 6. . . . . . . . . 58 -25 8. . . . . . . . . 10 -14 Y...... 55 -30 10 . . . . . . 40 -20 11. . . . . . 20 -20 12.. . . . . 80 -10 13.. . . . . . . . . . . 1500 .. 60 .. 15 . . . . . . . . . . . . . 1380 1407 45 67 -27 16 . _ , ., . , , , . , , , 1302 1.322 32 82 -20 1 7 . . . . . . . . . . . . . 1323 1343 54 63 -20 18 . . . . . . . . . . . . . 1358 1400 53 60 -42 .4verage,
-
-
41
52
-
-19
catc results was 3 0 ' ; t h e average deviation was rooa better agreement t h a n !vas obtained in m y of t h e other furnaces. Also, varying t h e rate of heating from z t o 10' per minute h a d less effect on t h e tests in air t h a n those made in hydrogen, R S shown in Figs. 1 2 an(? 13. E F F E C T O F L-ARIOUS A T M O S P H E R E S
I n Table X X is given a comparison of average softening points obtained in different atmospheres under otherwise similar conditions. T h e maximum differ-
T h e lowest results for 1 8 samples were distributed ainong t h e different furnaces as follows: Molybdenum furnace No. 1 . . 10 Korthrup f u r n a c e . . . . . . . . . . . . 1 Molybdenum furnace S o . 2 , . 1 Muffle furnace No. 2 . . . . . . . . . 1 Carbon resistance furnace.. . . 4 hleker furnace.. . . . . . . . . . . . . . 1 APPEARASCE O F COKES SOFTENED I N VARIOUS A l M O S PHERES
4TAIOSPHERE-In Fig. are shovvn t h e 1-arious mays in which cones of different ashes deform on heating in air in the platinum
(a)
P L A T I K U M l?L R S A C E , A I R
Ij
17m
Ism
.: *ci
s
lya
!
13m
&
1200
i m
PcrtrlR10,2P
FIG
I?
36
31
10
14-COMPARISON h
T
~
I.
20
9
9
I
18
70
I9
8
,
5
5
13
s
O f S O F T E N I N G T E M P E R 4 T L R E S O B T A I h E D IN
PLATINUU ~ ~ A U D~ M O ~LYB ~ D~N ~ FURNACES LN ,
furnace The manner of deformation I S somei5hat characteristic for each individual ash. No j 9 illust r a t e s t h e typical Seger cone bend, S o . 2 6 t h e type
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
480
which fuses t o a lump, No. 29 t h e intumescing type. No. 7 is an ash which did not soften a t I~OO'. The
FIG. 15
color of t h e fused cones varied from a buff, or reddish brown, t o a glossy black. T h e black cones were magnetic. YI D R 0 G E K AT ZI 0 S P H E R E ( b ) 210 L Y B D E N U 31 F C RK A CE S I € -Fig. 16 illustrates typical forms from t h e molybdenum furnace (hydrogen atmosphere). Owing t o t h e reducing atmosphere. these cones almost always developed a pronounced vesicular structure. I n some cases a s in ash No. 3, t h e swelling due t o t h e evolution of gas prevented t h e cone from bending i n t h e normal manner. This is one of t h e reasons for t h e somewhat larger variations between duplicate determinations in re-
FIG. 16
ducing atmospheres. T h e fused cones were usually light t o d a r k gray or grayish black in color; t h e y h a d a vitreous luster a n d invariably showed iron globules on examination under t h e microscope. ( 6 ) SORTHRUP
FURNACE,
CARBON
MONOXIDE
AIiD
cones fused in t h e Northrup furnace (CO atmosphere) varied from a d a r k gray t o a brownish black or metallic black color. T h e surface lacked t h e vitreous luster of t h e cones fused i n air or hydrogen. Carbon was deposited on t h e cones a n d base in increasing q u a n t i t y as t h e NITROGEK
ATMOSPHERE-The
Vol. 7, No. 6
was interrupted a n d t h e furnace allowed t o cool. ,4s shown i n Fig. 1 7 , fusible constituents appeared t o separate a n d r u n down t h e sides of t h e cone, leaving a refractory skeleton standing. However, on breaking t h e cone i t appeared t h a t t h e irregular contour was due t o t h e evolution a n d expansion of gases i n t h e interior of t h e softening slag. T h e expanded bottom was a thin-shelled bubble of slag, a s was t h e case in ashes I j , 8 a n d 1 7 . T h e first perceptible swelling of t h e lower p a r t of ash KO. 8 took place a t 392' below t h e point where it finally bent over in t h e position shown in t h e photograph. T h e earlier fusion of t h e thick p a r t of t h e cone may be due t o t h e inability of t h e carbon monoxide t o penet r a t e a n d reduce t h e iron oxide in t h e interior t o metallic iron as rapidly as in t h e t h i n upper p a r t . This phenomenon of irregular softening was noted only i n t h e Northrup a n d carbon-resistance furnaces. G-DOWN-DRAFT
CERAMIC K I L N
Several years before t h e present investigation was begun, one of t h e authors h a d occasion t o determine t h e relative softening temperatures of a number of ashes a n d clinkers. Through t h e kindness of A , V. Bleininger these tests were made i n a 6-foot downdraft kiln a t t h e Pittsburgh station of t h e Bureau of Standards. T h e ash was ground t o I O O mesh, molded in. X 2 ' / 2 in. cones a n d mounted in two rows, into one above t h e other, i n t h e middle of t h e muffle space of t h e kiln. T h e muffle space was 26 in. long X 2 6 in. wide X 30 in. high. T h e temperatures were read from two thermo-elements, one in each row of cones. T h e rate of heating such a large kiln was necessarily TABLEXXI-COMPARISONOF SOFTENING TEMPERATURES OBTAINEDIN
DOWN-DRAFT CERAMICK I L N .WITH THOSEOBTAINEDI N PLATINUM RESISTANCE FURNACE KILN: 100 mesh ash; 1/2 in. X 2112 in. cones; rate of heating, l o o o per hour; inclined 2 5 O from vertical. PLATINUM FURNACE:Ash ground to an impalpable powder; 8/18 in. X 1 in. cones placed in vertical position; rate of heating, 5 O per minute to first visible softening, then 2' per minute to softening point, SOFTENING IN ' c . INTERVAL SOFTENING POINTI N OC. Platinum Pt. Sample No. Kiln furnace Diff. Kiln furn. 63 . . . . . 1198 1173 1194 1214 Av., 1194 1270 -76 7 70 59 . . . . . 1166 1190 -24 3 30 56 ..... 1163 1210 -47 3 35 1250 -71 2 57 ..... 1179 25 1255 1300 -45 36 50 62 ..... 1256 1257 6 0 . . ... Av.. 1257 1290 -33 14 40 29 . . . . . 1347 1348 A v . , 1348 1380 -32 12 55 1420 1397 27.. ... 1342 1258 1360 A v . , 1320 13 46 AY., 1409 -89 5 60 26... .. 1356 1410 -54 54 ..... 1275 1265 25 Av., 1270 1350 -80 51 51.. . 1296 1288 50 AY., 1293 1370 -77 36 1280 -6 1 9 30 53.'. ... 1219
..
-
Average, -57 FIG. 1 7
temperature exceeded I~OO', as shown b y t h e blackened base of ash KO. 8 (Fig. 1 7 ) which was heated t o 1550'. Another peculiarity in t h e Northrup series was t h e softening a n d swelling of t h e thick b o t t o m portion of some of t h e cones before t h e apex began t o soften. Ash No. 4 began swelling a t t h e base a t IZOO', heating was continued at t h e rate of z o per minute until a temperature of 1375' was reached, when t h e current
-
-
16
43
slow. Heating was begun i n t h e evening, t h e gas burners being so adjusted t h a t b y morning a temperat u r e of 800 t o gooo was reached. T h e temperature w a s - t h e n increased at t h e rate of 100' per hour until t h e last cone was down. An oxidizing atmosphere was maintained b y admitting a large excess of air around t h e gas burners. T h e results obtained in t h e kiln are given i n Table X X I , together with results obtained on t h e same samples
J u n e , 191;
T H E J O C R N A L O F I N D U S T R I A L A N D ENGINEERING CHEiMISTRY
of ash in the platinum furnace under strictly oxidizing conditions. T h e consistently lower softening points obtained in t h e kiln m a y be attributed t o t h e much slower r a t e of heating, a n d also t h e possibility of some slight reduction b y products of incomplete combustion. Considering t h e difference in test conditions t h e agreement is remarkably close. S U 1111.4 R Y A N D C 0 N C L U S I O S S
T h e effect of various factors on t h e softening temperature of a number of typical coal ashes has been studied in eight different furnaces, having atmospheres of varying degrees of oxidation and reduction. T h e influences of t h e more i m p o r t a n t factors are summarized as follows: I-SIZE ASD S H A P E O F com-Cones t h a t measured l,'~ in. X 11j2 in. gave closer duplication a n d from I O t o jo" lower average softening points t h a n '/4 in. X I in. cones; 3 , ' 1 6 in. b y I in. cones gave practically t h e same results as 1;/4 in. b y I'/~ in. cones. T h e more slender cones were more satisfactory in giving shorter a n d more definite softening intervals; t h e y also gave less trouble from intumescence due t o evolution of gases from the melting ash. In reducing-atmosphere tests. t h e surrounding gases penetrated a thin cone more uniformly t h a n one with a v-ide base. 11-FIKENESS O F ASH-Ash ground t o a n impalpable powder tended t o soften a t a slightly lower tempert u r e t h a n I O O mesh ash. T h e difference averaged 6 " and in no case exceeded 40'. Ash pulverized t o a t least zoo mesh could be molded into more substantial cones t h a n 1 0 0 mesh material. 111-XKCLINATION O F cosEs-LIounting t h e cones with a considerable inclination, 3 j or 4 j " from t h e vertical, led in some cases t o premature deformation points, which were caused b y a further bending over due t o shrinkage of t h e cone in its base, rather t h a n deformation due t o softening and flowing of t h e ash. Vertical or nearly vertical cones were free from this source of error, a n d gave t h e most concordant indications: IV-RATE O F HEATIxG-In general, slower rates of heating gave lower softening points. R a t e s slower t h a n z o per minute are too time-consuming for practical consideration. Rates faster t h a n IO' per minute led t o inaccurate temperature measurements. Varying t h e rate of heating from z t o I O " per minute caused less increase of softening temperature in oxidizing atmospheres t h a n in reducing atmospheres of hydrogen (see Figs. 1 2 a n d 13). A '2 r a t e of heating gave t h e most uniform results; however, heating j " per minute t o initial deformation a n d t h e n reducing t o 2 " per minute gave practically t h e same results a n d saved considerable time. V0 X I D I Z I N G 0 R R E D U C I S G AT 110 SPHERET h e a t rn 0Sphere in which the ash was heated proved b y far t h e most important factor in causing large variations in t h e softening temperature. A s pointed o u t in t h e introductory theoretical discussion, t h e highest softening points were obtained, either in a n atmosphere of air (platinum furnace), or in a strongly reducing a t mosphere of carbon monoxide ( N o r t h r u p furnace) which prevented t h e iron oxide from acting as a flux-
481
ing agent b y reducing i t t o metallic iron before t h e softening of t h e ash began. T h e lowest softening temperatures were obtained in those atmospheres of mixed gases in which reduction of ferric oxide proceeded mainly t o ferrous oxide, t h e most actil-e phase of iron as regards slag formation a t lower temperatures. Such a condition apparently existed in t h e muffle furnace No. 2 , t h e molybdenum furnace So. I , and in many of the carbon resistance furnace determinations. The maximum variation in softening temperatures due t o different atmospheres ranged from 143 t o 4 9 j 0 C . (see Table X X and Figs. 4, 6, 8, IO, 1 2 , 1 3 a n d 14). S T A S D A R D M E T H O D S F O R D E T E R M I S I N G T H I : SOFT1:SISC. TEIJPERATURE OF ASH
Obviously, t h e statement t h a t a n ash has a "fusing '' or softening temperature of I j o o ' means nothing unless t h e exact conditions of making t h e test are defined. The method m u s t , therefore, he carefully standardized in all its details before comparable results m a y be secured by different workers. T h e most important consideration is t h e atmosphere in which t h e test shall be made. From t h e standpoint of securing results t h a t can be duplicated in different laboratories, t h e softening temperature in air, as was determined in t h e platinum furnace, is undoubtcdly t h e most satisfactory s t a n d a r d ; b u t unfortunately, ash forming in a fuel bed is not free from the cffectsof reducing gases. Consequently, clinkering m a y take place under conditions of partial reduction similar t o those which prevailed when t h e low softening points were obtained in t h e molybdenum or gas furnaces. Therefore, t h e lowest softening temperature of a n ash under such conditions as will reduce t h e ferric oxide t o t h e ferrous form should give t h e most promising relation t o clinker formation under furnace conditions. Such a method will be described in a subsequent paper. A C K I\-0W L E D G ME S T S
The authors desire t o express their deep appreciation of t h e assistance a n d of t h e m a n y helpful suggestions received from G. A. Hulett, consulting chemist of t h e Bureau of h'fines, and from A . V. Bleininger, of t h e Pittsburgh station of the Bureau of Standards. T h e observations in t h e h-orthrup-furnace series and t h e platinum-furnace series of Table X X I were made b y Alex. L. Feild. Some of t h e molybdenumfurnace tests were made b y W. 4. Mueller. T h e chemical analyses were made b y H . H. Hill, W. A . Selvig a n d F. D. Osgood, all of this laboratory. A number of t h e coal samples used in this investigation were furnished b y hlr. E . G. Goodmin, Chief Fuel Inspector of t h e Southern R a i l v a y . C H E M I C A L L A B O R A T O R Y , u. s. BUREAU O F hIINES PITTSBURGH,
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PHYSICAL CONSTANTS OF GAS OILS AND DERIVED TARS By WALTERF. RITTMAN A N D GUSTAVEGLOFF Received January 4, 1915
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I n connection with a general s t u d y of t h e behavior hydrocarbons under different temperatures and
1 Published with the permission of the Director of the Bureau of Mines.
