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3-Investigation of the power losses in gears under heavy loads and lubricated by oils.’8 Some, interesting results have been obtained by this method in England,’#which confirm the superiority of vegetable and animal over mineral oils under these conditions of Dartial lubrication. Tests with greases are not satisfactory from this standpoint because so much of the friction is in the mass of grease itself, rather than between the gear teeth. 19 Report of Lubricants an3 Lubrication Committee, Department of Scientific and Industrial Research, Advisory Council, 1920.
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ACKNOWLEDGMENT The writers desire to acknowledge the courtesy of the General Motors Research Corporation and of the Standard Oil Company of New Jersey in permitting the publication of these results; and the invaluable assirtance of Messrs. Harry Myers and Tyler Fuwa of this Laboratory, who have made all the static friction measurements and capillary clogging measurements, respectively.
Comparison of the Standard Gas Furnace and Micropyrometer Methods for Determining the Fusibility of Coal Ash1l2 By A. C. Fieldner,3W. A. Selvig and W. L. Parker FUELS CHEMICAL LABORATORY, PITTSBURGH EXPERIMENT STATION, BUREAUOB MINES,PITTSBURGH, PENNSYLVANIA
Coal ashes showing a softening temperature under 2600’ F. by the gas furnace method can in the majority of cases be checked wifhin 100’ F. by the micropyrometer method if fused in a reducing atmosphere of combustion gases similar to that employed in the gas furnace method. Some coal ashes will, howeuer. show considerably greater differences between the two methods. Very refractory ashes, showing a softening temperature above 2800” F. as determined by the gas furnace method, tend to give considerably lower results by the micropyrometer method. The great majority of ashes from American coals, however. fuse below 2800’ F. in the gas furnace. The two methods can therefore not be considered as strictly alternate methods for all ashes. I n general, the micropyrometer method shows a point in the fusion process at which the particles become rounded and coalesce. This point agrees fairly well with the “down point” of the cones in the gas furnace method for ashes of low and medium fusibility ( u p to 2600’ F.), since such ashes
form a fairly fusible slag of short softening range. Refractory ashes form triscous slags with long softening interuals; therefore the down point of the cone.may be from 100’ to 500’ F. higher than the jusing point as shown on the platinum strip. The micropyrometer method with reducing atmosphere has the advantage ouer the gas furnace in being much more rapid U f f y determinations can be made in a day of 8 hrs. as compared to fifteen on the gas furnace) and in dispensing with the special ashing of a quantity of coal. The residue of the usual ash determination is suficienf for tests; also i f is more comfortable to the operator. Some checks between different laboratories indicate that the micropyrometer method can probably check itself in the hands of different operators as closely as the gas furnace method. Further work should be done on this phase of the subject. It may be advisable to adopt both methods as fentatiw, although not alternate until such a time as experience will show which is preferable.
OAL ash is a mixture of substances and therefore does not have a definite melting .point. The fusion or softening temperature depends on a number of variables and consequently must be empirically defined in order that reproducible results may be obtained in different laboratories. At the present time the American Society for Testing Materials4 has tentatively defined the softening temperature of coal ash as the temperature a t which a triangular pyramid 0.75 in. high and 0.25 in. at each side of base, mounted vertically, has fused down to a spherical lump when heated in the reducing atmosphere of a gas furnace under definitely prescribed conditions. Recently Mr. W. H. Fulweiler, Chemical Engineer of the United Gas Improvement Company, applied to coal ash the micropyrometer method6 of determining the melting points of minute specimens. The advantages claimed for the micropyrometer over the gas furnace method are greater speed, convenience, and comfort to the operator iu making fusion tests. I n order to obtain data on the comparative
results by the two methods, fusion tests were made on B series of coal ashes of varying fusibility, ranging from 1800° to 3000’ F. by the gas furnace method. MICROPYROMETER APPARATUS The micropyrometer apparatus as used in making the tests was assembled from apparatus available in the laboratory. A diagrammatic sketch showing the arrangement of the equipment for making fusion tests in air is given in Fig. 1. The heating element consists of a platinum strip 4 cm. long X 0.5 cm. wide X 0.008 cm. thick held between the iron rods h which are connected through the spiral nichrome resistance coil t to four storage battery cells, a, connected in series. The maximum current required to attain temperatures as high as 2850’ F. is 45 amp. From 10 to 15 amp. of the total current are supplied from a direct current power line which is connected through the adjustable rheostat d in parallel with the storage batteries. Rheostat d also serves as a charging rheostat in charging the storage batteries, a. The resistance strip i is enclosed in a small dum furnace, j , which is divided into two parts, the upper half of the furnace being removable and provided with an observation hole over which is placed a microscope cover glass. The furnace rests on the stage of the microscope k. The microscope is provided With 48-mm’ Objective and a 6x ocular. The ocular contains a small, tungsten, hairpin
C
1 Received March 20, 1922. Presented before the Division of Industrial and Engineering Chemistry a t the 63rd Meeting of the American Chemical Society, Birmingham, Ala., April 8 t o 7 , 1922. 9 Published by permission of the Director, U. S . Bureau of Mines. a Superintendent, Pittsburgh Experiment Station. 4 “Tentative Method for Determination of Fusibility of Coal Ash,” Proc. A m . SOC.Test. Matnials, 80 (1920), 796. 6 G. K . Burgess, “A Micropyrometer,” Bur. Stds., Bull. 9, No. 4 (1913), 475.
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flament lamp so adjusted that the filament coincides with the image plane of the eyepiece. A piece of monochromatic red glass mounted in a removable cap is slipped over the
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to indicate the rate of flow. Samples of gas as delivered into the metal pyrometer furnace were taken at various times when the MBker furnace was operated under the conditions described, and the analyses of the gas samples showed that its composition remained very uniform. As considerable water condensed in the tubes connecting the metal pyrometer furnace to the M6ker gas furnace, the water content of the gas delivered into the pyrometer furnace was calculated by assuming the gas to be saturated with water vapor a t the temperature a t which it was collected. The analyses of the gas samples are given in Table I. TABLEI-COMPOSITION OF FURNACEATMOSPHERE USED IN MAKINQ MICROPYROMETER FUSIBILITY TESTS IN REDUCINOATMOSPHERE OF COMBUSTION GASES 7 PERCENTAGE BY VOLUME SAMPLE No. COZ 02 HzO H 2 CO CHI NZ 1 5.7 0.5 2.7 7.5 8.7 0.9 74.0 2 5.6 0.2 8.1 2.7 8.8 0.6 74.0 3 6.6 0.4 7.6 2.7 7.0 0.0 75.7 4 5.2 0.3 2.7 8.5 9.3 0.9 73.1 5 6.2 0.4 2.7 7.4 7.4 0.0 75.9 AV. 5.9 0.4 2.7 7.8 8.2 0.5 74.5 Total oxidizing gases (COz Oz HnO) = 9 . 0 per cent Total reducing gases (HI CO .-I-CHI) = 1 6 . 5 per cent Ratio of reducing gases to oxidizing gares = 65 : 35
++ +
FIG.~-MICROPYROMETER APPARATUS FOR DETERMINATION OF FUSIBILITY OF COALASH a, 4 chloride cell storage batteries (Type 6-11), Electric Storage Battery Co. b Fuses-65 amp. c; Knife switch to furnace "J" (80 am ) d. Cu&r Hammer charging rheostat (max. capacity, 20 amp.) e, Snap switch j, Fuses-25 amp. Knife switch-60 amp. i/z-in. iron rods for holding platinum strip i i,Platinum strip 4 cm. X i / z cm. X 0.003 in. thick j Alundum furnace k: Microscope, 6x ocular, 48 mm. objective
8:
E , Tungsten hairpin filament lamp 2.6 volts, 0.4 ampere (Edisod Mine Safety Lamp bulb, B . M. 10) m, Fixed resistance in parallel with pyrometer lamp (28 gage "Tarnac" wire in Economy fuse Plug)
o , Two dry cells in series
p , Slide wire resistance coil (1 ohm) a, Slide wire resistance coil (2.8
ohms) Knife switch s, Milliammeter (scale, 0 to 750 milliamperes) I , Spiral nichromeribbon resistance coil (ribbon l i / d in. wide, 29 B. and S. gage)
Experimental work done by the Bureau6 with hydrogen and water vapor mixtures, and carbon monoxide and carbon dioxide mixtures indicate that the gas mixture need only be controlled between 30 and 70 per cent reducing gas to insure the lowest softening temperature of coal ash. The ratio of reducing gases to oxidizing gases (65:35), as shown in the average analysis of the gas used in the brass micropyrometer furnace, comes within these limits.
CALIBRATION OF PYROMETER LAMP
Y.
top of the eyepiece. A removable cap containing a pinhole in its center is placed over the monochromatic glass on top of the eyepiece. The terminals of the lamp are connected through slide-wire resistances, p and q, through the switch r to a milliammeter, s. Current for the lamp is supplied from two dry cells, 0 . A fixed resistance, m, consisting of resistance wire mounted in an Economy fuse plug is connected in parallel with the pyrometer lamp. This resistance is so adjusted as to give the maximum deflection on the milliammeter for the temperature range for which the pyrometer lamp is calibrated. METALFURNACEFOR REDUCINU ATMOSPHERE
For obtaining a reducing atmosphere surrounding the ash an airtight cylindrical brass furnace shown in Fig. 2 was made. The inlet tube of the brass furnace was connected by means of rubber tubing through a bottle to catch condensed water, to a porcelain tube which was inserted in a small MBker muffle furnace. The muffle furnace was modified by removing the muffle and replacing it with a porous alundum tube about 1.25-in. internal diameter. The open front of the furnace around the alundum tube was closed with alundum cement. A small disk of alundum cement was inserted into the projecting end of the alundum tube and the porcelain tube inserted through a small hole in the center of the disk into the furnace. The furnace was heated by means of a MBker blast burner to a temperature of about 900" C. To insure an excess of reducing gases the furnace was operated so as to have a flame of about 3 to 5 in. issuing from the top of the chimney. The gas from the muffle furnace was aspirated through the metal pyrometer furnace by connecting to a Chapman water pump through a Mariotte flask and a flask containing water through which the gas was bubbled
The pyrometer lamp was calibrated and checked a t frequent intervals by melting small portions of pure gold, diopside, and palladium on the platinum strip of the micropyrometer furnace. The lamp filament was matched against a clean spot on the platinum adjoining the fused material.
METAL fURN4C.f f7.X R€DUC//JGATMOSPHERE FIO.
2-METAL
FURNACE
AND
REDUCINGATMOSPHERE
A. C. Fieldner, A. E. Hall and A. L. Feild, "The Fusibility of Coal Ash and the Determination of the Softening Temperature." Bur. Mines, Bull. 199 (1918). 49, 53.
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The same procedure was followed in determining the fusion point of the coal ash. A calibration curve was drawn through the three points obtained with gold, diopside, and palladium,
FIG. &-GRAPHIC REPRESENTATION O F VARIATIONS OF F U S I B ~ I TOY F COALASH AS DETERMINED BY MICROPYROMETER METHOD IN AIR AND GAS FURNACE METHOD
the temperatures required to melt these substances being taken as 1063", 1391", and 1549" C., respectively.
TESTSI N OXIDIZING METHODOF MAKINGFUSIBILITY ATMOSPHERE OF AIR The coal ash remaining from the determination of ash in the proximate analysis of the coal was ground to an impalpable powder in an agate mortar. A portion of the finely ground ash was moistened with distilled water and a small amount' transferred by means of a glass rod drawn to a point to a piece of platinum foil about 3 mm. square. One corner of the platinum foil was turned up so it could be readily picked up with a pair of forceps. The platinum foil with the ash was placed on the platinum heating strip and adjusted so as to be in the center of the field of the microscope. The upper part of the furnace was put in place and the observation hole covered with a microscope cover glass. The temperature was raised by means of the resistance t until the ash showed distinct fusion under the microscope. The temperature reading was taken by adjusting the current through the pyrometer lamp by means of the slide wire resistances p and q until the tip of the lamp filament disappeared when focused against a clean spot on the platinum foil near the fused coal ash. The temperature of the platinum heating strip could be raised by proper manipulation of rheostat t with one hand, and a t the same time the current going through the pyrometer lamp could be adjusted by manipulating the slide wire resistances p and q with the other hand. The point taken as the fusion point of the ash was that a t which the irregular-shaped aggregates of ash particles showed a well-defined rounding under the microscope. Care should be taken that the fusion point is not confused with a sintering of the ash, and in case of doubt it should be examined after the determination a t a higher magnification than that used in making the determinations. METHODOF MAKINGFUSIBILITY TESTSI N REDUCING ATMOSPHERE OF COMBUSTION GASES After the ash sample had been placed on the platinum heating strip of the brass micropyrometer furnace, the combustion gases generated in the MBker furnace were rapidly aspirated through the brass furnace for 5 min., after which the gas flow was regulated to 3 to 4 bubbles per see. and the fusibilitv determination made in the manner described.
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COMPARISON OF MICROPYROMETER AND GAS FURNACE RESULTS In order to compare the results obtained with the micropyrometer in both oxidizing and reducing atmospheres with the fusibility as determined by the gas furnace method, representative coal ashes covering a wide range of fusibility were selected. The tentative method for the determination of fusibility of coal ash adopted by the American Society for Testing Materials4consists of heating finely ground coal ash, molded into triangular cones, 0.75 in. high and 0.25 in. a t each side of the base, a t a rate of heat increase of not less than 5" or more than 10" C. per min. in a pot furnace, with proper regulation of air and gas so as to obtain an atmosphere sufficiently reducing to reduce the ferric oxide in the coal ash principally to ferrous oxide, which conditions give the lowest temperature a t which fusion occurs. The point taken as the fusion point is designated as the "softening temperature," and is defined as the temperature at which the cone has fused down to a spherical lump. For convenience the coal ashes selected were subdivided into three groups according to the "softening temperatures" obtained with the gas furnace method: Easily fusible ashes, softening below 2200' F. Ashes of medium fusibility, softening between 2200' and 2600O F. Refractory ashes, softening above 2600' F.
The coal ashes were run by the gas furnace method and by the micropyrometer method in an oxidizing atmosphere of air and in a reducing atmosphere of combustion gases. The variations of the micropyrometer determinations in an oxidizing atmosphere of air from the gas furnace determination are given in Fig. 3. The variations of the micropyrometer determinations in a reducing atmosphere of combustion gases from the gas furnace determinations are given in Fig. 4. I n a few instances, with the very refractory ashes, sufficiently high temperatures were not attained in the gas furnace to reach the "softening temperature" of the ash samples, although these ashes were fused by the
S D F T C N N T TCMPERITYCE
DF,
n s
FYRNICE
FIG.4-GRAPIiIC
REPRESENTATION OR VARIATIONS O F FUSIBILITY OF COALASH AS D ~ T E R M I NBY E DMICROPYROMETER METHODIN REDUCING ATMOSPHERE OB COMBUSTION GASESA N D GAS FURNACE METHOD
micropyrometer method. Such ashes are indicated in the figures by a cross sign (X), and the differences between the methods is greater than that indicated. It will be noted that with easily fusible coal ashes, softening under 2200' F., the micropyrometer method with an oxidizing atmosphere of air gives much higher results than the gas furnace method, but that when the same ashes are run by the micropyrometer method in a reducing atmosphere of combustion gases much closer checks are obtained between
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the gas furnace and micropyrometer. With ashes of medium fusibility and refractory ashes there is no marked difference between the results obtained with the micropyrometer method in oxidizing or reducing atmospheres. The consistently high results obtained on easily fusible ashes when fused by the micropyrometer method in air are unquestionably due to the high iron content of such ashes, which necessitates careful consideration of the atmosphere in which the ashes are fused. An oxidizing atmosphere will oxidize the iron to the ferric state, which gives more refractory silicates than are obtained when the iron is reduced principally to the ferrous state, a condition which results in the reducing atmosphere of the gas furnace method. Fig. 4 shows that much closer checks on the easily fusible ashes are obtained between the micropyrometer and gas furnace when an atmosphere similar to that obtained in the gas furnace is used. It will be noted that with the very refractory ashes the micropyrometer method tends to give lower results than t,he
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deformation temperature” of the gas furnace method, the temperature at which the first indication of fusion is observed as indicated by the rounding or bending of the apex of the ash cones. With the majority of coal ashes the micropyrometer fusion point is higher than the “initial deformation temperature” of the gas furnace, although it will be noted that very refractory coal ashes will show distinct fusion under the microscope a t temperatures lower than the “initial deformation temperature” of the gas furnace.
RESULTSOF CHECKDETERMINATIONS BY DIFFERENT LABORATORIES Five samples of coal ash covering a wide range of fusibility, from 2000’ to 3000’ F., as determined by the gas:furnace method, were sent to eight laboratories for fusibility determinations. Five laboratories determined the ash fusibility by the gas furnace method of the American Society for Testing Materials, and three laboratories determined ash fusibility by the micropyrometer method in an oxidizing atmosphere of air. The laboratories were asked to submit the first three results obtained on each ash and not to run duplicate determinations a t the same time. The individual laboratories checked themselves closely on each ash, and in this respect there is no apparent difference between the two methods, as individual operators can check within 50” F. on duplicate determinations. The average values reported by the different laboratories are given in Table 11. Further checks between different laboratories should be made with the micropyrometer method in a reducing atmosphere of combustion gases comparable to that of the gas furnace. TABLE 11-AVERAGE OF THREE FUSIBILITY TESTS BY DIFFERENTLA=ORATORIES O N FIVE STANDARD COAL ASHESBY GAS FURNACE METHOD AND MICROPYROME‘I‘ER METHOD IN OXIDIZING ATMOSPHERE OF AIR
GAS FURNACE METHOD Ash 1 Ash2 Ash 3 Ash4 LABORATORY F. F. O F. O F. FIG.S G R A P H I CREPRESENTATION OF VARIATIONS OR FUSIBILITY OB A 2060 2320 2500 2730 COALASH AS DETERMINED BY MICROPYROMETER METHODIN R E D U C I N ~ B 2050 2350 2480 +2660 c 2000 2270 2420 2610 ATMOSPHERE OF COMBUSTION GASESAND “INITIAL DEFORMATION TEMPERD 2060 2380 2550 2740 ATURB” OF GAS FURNACE METHOD E 2000 2220 2370 2580 Av 2030 2310 2460 4-2660 MICROPYROMETER METHOD,IN AIR gas furnace. This difference appears to be the greatest in A 2180 2280 2340 2500 ashes fusing above 2800” F. in the gas furnace. A number F 2260 2330 2360 2610 G 2250 2350 2440 2550 of such ashes were made into cones and heated in the gas Av. 2230 2320 2380 255D furnace just up to the temperature where fusion was evident
.
by the micropyrometer method, after which the cones were examined under a microscope. Although sufficient fusion had not resulted to cause the cones to assume a spherical shape, the ash of ’the cones had a fused appearance when examined under the microscope. In some cases the cones still retained their original shape. Owing to its complex composition coal ash has no definite, sharply defined melting point. When subjected to heat there is a distinct temperature interval in the gas furnace method between the time when the ash cone first shows an indication of fusion as evidenced by the rounding or bending of the tip and the time when the material has become sufficiently fluid to flow down to a spherical lump. With highly refractory ashes there is sufficient fusion of eutectic mixtures to give a distinctly fused appearance under the microscope, but a t such temperatures with the cone method sufficient unfused material is present to prevent any great deformation of the cone. However, the large majority of coal ashes fuse by the gas furnace method below 2800‘ F., and the extreme variations shown in Figs. 3 and 4 represent exceptionally refractory coal ashes. Fig. 5 gives the variations between the temperatures a t which fusion occurred with the micropyrometer method in a reducing atmosphere of combustion gases and the “initial
Ash 5 O
F.
+29001 +2640 2800 3000
....
+2840 2620 2750 2600 266~
News from Canada That the foundation of scientific control lies in good will and intelligent cooperation is the view of leading men in Canada’s pulp and paper industry. This was strongly evidenced a t the summer meeting of the Technical Section of the Canadian Pulp and Paper Association, held a t Iroquois Falls, Ontario, June 19 to 22, as guests of the Abitibi Power and Paper Company. The Abitibi Company employs 1125 men, makes more newsprint a day than any other mill, and operates the largest machines in the world. Twenty feet is quite a width to make a sheet of newspaper and to keep flat so that it will run smoothly on the big fast presses, but the Abitibi people are running two of this size at the rate of 650 f t . a minute, and their output would cover a six-acre field in 10 min. One of the most important parts of this plant is the Service Department, which includes the science part of the business. A t the time of our visit the laboratories were working on cymene, sulfur, and uniformity of product. This department is also the educational agent, and maintains a well-equipped classroom where night school is carried on and production records are shown by means of lantern slides. Bids for the construction of the chemical building of Loyola College, Baltimore, Md., have been received, and announcement of the awarding of the contract is expected in the near future.
