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I Pi D U S T R I A L A N D E N G I N E E K I N G C H E %I I S T R Y
to the difference in painting practice as regards the exposed surface.
VOl. 27, No. 2
RECEIVED September 21, 1934. Presented before the Division of Paint and Varnish Chemistry at t h e 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 t o 14, 1934.
Spontaneous Ignition of Petroleum Fractions P. J. WIEZEVICH, J. M. WHITELEY,AND L. B. TURNER, Standard Oil Development Company, Elizabeth, N. J.
V
A R I 0 US investigators (510" C.) none of the oils could Spontaneous ignition temperatures of various have published data on be made to i g n i t e e i t h e r on fractions f r o m different crudes were determined. the spontaneous ignition the bare open plate, or when A minimum value is noted in the kerosene and temperatures (or auto-ignition dropped on a thin mat of asbesfuel oil range, while a rapid rise takes place in temperatures) of a number of tos. L i g h t fractions such as the lubricating oil range. W h e n compared acpure compounds and petroleum gasoline would immediately form a ball, similar to that of a drop products. These observations cording to boiling point, both Pennsylvania and are of value in determining the of water on a hot stove, and Colombian crude fractions show similar sponexplosion and fire hazards inthen g r a d u a l l y distill away. taneous ignition temperature curves. volved in the numerous comHeavier oils volatilized off (probExperiments with heated open plates and closed mercial processes e m p l o y i n g ably with simultaneous crackcontainers heated with oxygen under pressure ing) , the vapors being diluted such products. with the air so quickly that no Hersey ( I S ) reported some are described. Oxygen is exceedingly dangerous i n t e r e s t i n g results on the exexplosive mixture resulted. in many cases, leading to detonations as well as F r o m t h e s e observations it plosive effects of mineral and the burning of metal lines. The presence of can be concluded that hot survegetable oils when subjected to nitrogen, steam, or other similar diluents greatly faces up to 950" F., open to the oxygen pressure, stating that the reduces the explosion hazard. air, do n o t p r e s e n t a serious critical temperature for linseed fire hazard when sprayed with oil lies between 60" and 120" C. The spontaneous ignition temperature is a s m a l l a m o u n t s of oil. The a t 2500 pounds per square inch relaticely simple melhod f o r indicating the strucdangerous conditions would exist (170 atmospheres) oxygen presof hydrocarbons. For the same number of ture where the surfaces were enclosed sure. Bridgeman and Marvin carbon atoms, the decrease in spontaneous ignior partly enclosed, or where they (6),a s well as M a s s o n a n d tion temperature falls roughly in the order: arowere contacted with considerable Hamilton ( l 7 ) ,have given sponamounts of oil, sufficient to form taneous ignition of various pure matics, alkylated aromatics, naphthenes, alkylated inflammable mixtures. Temcompounds and fuels ( 9 , 9 A , 16, naphthenes, straight-chain parafins, branchedperatures above red heat might 21,22). The effect of pressure on chain parufins, and unsaturated aliphatics. c a u s e i g n i t i o n of even small this property has been discussed quantities of oil. by various investigators (7, 15, 1;). A number ofvalues for petroleum products have been EXPERIMENTS IN CLOSEDIGNITIOK APPARATUS determined by the A. S. T. M. method and a standard apparatus has been devised ( 2 ) . In this connection, it might be emphasized that the results Araki and Otsu (3) have recently shown that the spon- with various methods described in the literature are only of a taneous ignition of gasoline is somewhat lowered by the addi- relative nature, comparison between them often being very tion of lubricating oils and even more so than when castor difficult. oil is added. The apparatus employed in the closed chamber runs was a The effect of knock suppressors and inducers has also been gas-heated Thompson bomb (21) and a somewhat modified studied (4,11, $0). Comparative data between air and oxy- Moore apparatus (18). The device is shown in Figure 1: gen are likewise available (8, 10, 14, 25). A represents a container cut from 4-inch (10.2-cm.) steel shafting. B, the ignition block, is also of mild steel and is made reEXPERIMENTS WITH OPEN HEATED PLATES movable to facilitate cleaning; if s. I. T. (spontaneous ignition During the study of auto-ignition temperatures of petro- temperature) is to be determined on othermaterials, this block may be inexpensively replaced by a similar piece of the desired maleum fractions, a few tests were made with a heated plate. terial. The temperature of the igniting surface is recorded by a Oil was dropped on a n open heated plate upon which a ther- thermocouple placed in well C. For most purposes an iron-constantan couple will suffice. A hole IS provided in cover D (made mocouple was welded. At temperatures up to 950" F.
E N G I NE E R I N G C H E M I ST R Y
I N D U S T R I A L A N 1)
February. 1935
of Transite board) through which the sample is introduced. This cover is held in place by screw E and pin F. The apparatus is supported on a 0.5-inch (1.27-cm.) Transite board, G, and is insulated by the asbestos pipe covering, H. After each trial, the vapors are blown from the vessel by a stream of air directed through J. An atomizer or the laboratory compressed air may be used for this purpose. The procedure involved setting up the apparatus on a ring stand over a gas burner, by means of which the temperature was raised and read by a thermocouple and potentiometer. A rough approximation of the S. I. T. was obtained by dropping a regulated size drop of the oil through the aperture in cover D unt'il ignition occurred, purging out the container after each addition. The process was then repeated carefully in order not to overheat block B. As soon as ignition occurred, the apparatus was allowed t o cool, and the temperature a t which ignition ceased was noted. The S. I. T. was then taken as the average of the tvo readings. The tests made with air in the closed ignition apparatus showed that a flameless explosion occurs about 30" F. (17'' C.) below the autoignition temperature of an oil. It is manifested by a sudden increase in pressure, probably due to oxidation after some incipient cracking, accompanied by a liberation of heat insufficient to propagate flame. It was also found that the heated surface had to be "activated," since otherwise the first reading was too high. This activation occurred after a few explosions were obtained. Spontaneous ignition runs were made on a series of West Virginia crude fractions ranging from gasoline to heavy waxy oil. The data are given in Table I. FR.4CTlOXP
FROM
415
451 474 500
522 580 604 700
...
...
...
213 233 246 260 272 304 318 371
49.0 46.1 45.4 44.3 4:i.l 41 2 40.2 36.7b
...
34.9c 32.8d 31.0
... ...
~NILIKE O
POIST F.('C.)
.... .. .. .. .. .... ....
159 (71)
....
172 (7s) 185 (85) 199 (93)
.... .... , .
,.
OF
s. I. T. O F .
550 560 555 530 505 520 520 500 490 505 480 710 750 790 810
t
FIGURE 1.
WEST VIRGINIA CRUDE
.kv. B. P. O F h . P.I. FRACTION& GRAVITY F. ' C. 125 52 6C1.4 275 135 58.1 325 163 54.3 375 191 51.3
were closely controlled, widely varying results were obtained. As an example, when the samples were introduced on the hot surface from dropping funnels giving varying drop sizes, variations of S. I. T. values as high as 100" F. (56' C.) were obtained. Also, the amount of air available for combustion had quite an effect upon the S.I. T. V i t h air, for instance, the
i
TABLE I. SPONTANEOCS IGNITIOS TEMPERATCRES (IN AIR)
C. 288 293 291 277 263 271 271 260 254 263 249 3i7 399 421 432
IGNITION APPARATUS
reading was reduced 50' F. (28" C.) by blowing in a small amount immediately after introduction of the cil. By controlling the amount of oil delivered to the cup, results could often be checked even within 5' F. (3" (2.). IGNITION TEMPERATURES (13AIR) TABLE 11. SPOXTAXEOCS FRACTIOXS FROM CRUDE OILS
OF
VISCOSITY
Av. B. P. OF FRACTION^ F. C.
A. P. I. At 100' F. At 210' F. GRAVITY ( 3 8 O c.) (99' c.) Seconds Seconds COLOMBIAX CRUDE
Reduced to atmospheric pressure. 55.5 viscosity Saybolt a t 100' F. (38' C.). C 82 viscosity Saybolt a t 100' F. d 44 viscosity Saybolt a t 210' F. (99' C.); 85 at 130' E". (54" C.).
0
b
The readings taken on heating and cooling were averaged, the average deviation between these two readings being about 25' F. (14' (2.). These results show that in the case of a West Virginia (Pennsylvania type) crude the first fractions, being mainly in the gasoline range, have fairly constant S.I. T.'s of about 550' F. (288' C.) in the modified Thompson apparatus. When the kerosene range is entered, the S. I. T. drops off irregularly until the lowest temperature of 480" F. (249' C.) is reached. Then the 9. I. T. suddenly rises in the lubricating oil range to 710' F. (377" (2.) and increases rapidly up to the last fraction, attaining an s. I. T. of 810' F. (432' C.). Table I1 shows the results obtained with fractions from Colombian and Pennsylvania crudes. The results are shown graphically in Figures 2 and 3. It was found, in accordance with statements in the literature, that, unless the conditions
153
448 641 632 753 786 815
231 283 333 401 419 435
37.5 31.5 27.7 24.0 23.1 21.9 20.0
441 520 595 685 726 745
227 271 313 363 386 396
44.8 41.6 39.1 35.6 34.8 33.8 32.5 30.4
...
...
...
...
l74:5 287.5 451 996
,. .. .. ..
53.1
67.7
s. I. 3'. F.
C.
505 505 662 745 765 780 795
263 263 350 396 407 416 424
480 480 670 687 716 730 755 785
249 249 354 364 379 388 402 418
PENNSYLYAK'IA CRUDE
... ...
0.
...
...
60
io
90 125 278
41 51.2
Reduced to atmospheric pressure.
SPONTAXEOUS IGNITION OF OILS IN OXYGEN UI~DER PRESSURE No attempts were made t o correlate the foregoing data in the presence of oxygen. It is believed, however, that the relationship of such results with those obtained with air would be similar, although the ignition temperatures in the former case would naturally be lower. Some comparative data for
154
IN1)tiSTHIAI.
A N D
E N G I N E E 1%I N G C E E M I S T 1%Y
air and oxygen with selected samples of oils are already available for atmospheric and elevated pressures ( 5 , 8, 15). A number of experiments with oxygen under pressure were made in a bomb 2.5 em. in diameter and about 15.2 cm. in length, provided with a safety disk containing a thermocouple. About 50 ce. of C o a t a l oil (43 seconds viscosity at 210" E'. or 99' C.) in a glass tube were introduced into the bomb and subjected to an oxygen pressure of 7.8 atmospheres.
Vol. 27, No. 2
and 300" C. sudden introduction of oxygen did not causeexplosion. The previous results must therefore be attributed to the catalytic effect of the iron, with which the oil came in contact when the glass tube was broken. This result >vas verified in the following run where no glass tube was eniployed. At 324" C. and 87 atmospheres oxygen pressure, sharp clicks were heard upon introduction of the oxygen, and finally the safety disk blew out with a loud report. The effect of a large surface was then tried. The method used was similar to that employed by the Bureau of 1M'mes (7), wheretheoil wasdistributedoverasbestoscotton. I n this case, at 232" C. and asudden oxygen pressure of 13W pounds per square inch (87 atmospheres), several snaps were heard, and finally the 8000-ponnd (533-atmosphere) gage w&s k '** shattered to pieces. The disk on the bomb was bulged out h' hut not ruptured. In contact with iron alone, the oil exL.; vi - 0 ploded, rupturing the disk at 298" C. and 100 atmospheres pressure. Without iron present and at 44 atmospheres pressure, the temperature rose from 190" to 270" C., but no explosion resulted. The explosions obtained when hot oils are contacted with ffyLepR6t BCy/INa P a s , ' 6 high-pressure oxygen are of the nature of detonations, so that FIGURE 2. COMPAAISON BY BOILING Pornrr OF S~om~ivsoossafety disks are generally of little value in such eases. A IGNITION TEM~ERATW~ES IN AIR OP PETROLEUM FW.F~I~NS number of cadastrophes with gasoline and oxygen by employing too high a pressure in the Hunn-Fischer-Blackwood gum The temperatiire was then raived to 300" C. (572" I?.). S o explosion or sudden rise in temperature was noted, although the sample was oxidized considerably. The same result was obtained with a Coastal oil of 75 seconds viscosity a t 210' F. The tests were repeated at temperatures up to 350" C. and oxygen pressures up to 15.6 atmospheres without any indications of explosion. I n order to try out more hazardous conditions, a small bomb was constructed of 0.64-cm. pipe about 10.2 cm, long having a pyod through the cap at one end and a 0.16-em. steel safety disk on the other. Aboiit 1cc. of oilsample oontained in an open ghss tube could be introduced, and temperatures up to 350" C. and oxygen pressures up to the full c y i i RP / C r F V l n der pressure were employed. The apparatus was covered with sandbags and placed in a boilcr plate stall, all tubing, etc., being covered with boiler plate. The ga,ge was mounted inside the stall and a mirror m s used for indirect observation of khe dial. borrh test have been reported ( I , l a ) , showing the same feaIn the Erst test the sample (0.5 cc. of I'ennsylvania oil of tures. The resnlts are generally similar tn the effect s h o r n 75 seconds viscosity a t 210" F.) in a glass tube was heated to in Figure 4, which was obtained with high-pressure ethylene 100' C., and oxygen from an intermediate container wa6 bled and oxygen. The tubing shattered was the usual inoh in suddenly up to 500 pounds per square inch (33 atmos- (1.6 rum.) i. d. and 3/,e inch (4.8 mm.) o. d. steel capillary pheres). No result was observed, so that the sample was pressure tubing capable of withstanding a t least 20,000 heated t o 305" C. and kept at that temperature. The gas pounds per square inch (1330 atmospheres) pressure. In was bled off and fresh oxygen was suddenly introduced. At this case the steel valve caught on fire, and a portion of it t h i s p o i n t a sharp melted the oxygen click was heard, and escaped. The importhe temperature rose tance of covering all to 324' C. This was lines and fittings of repeated several t h u type is emphatimes, and a similar sized. In this type of result was observed. work it is advisable When the bomb was to employ boiler plate opened, it was found p a n e l s from which that the glass tube only the valve stems was shattered, and all p r o j e c t . Gagesare of the oil had been b e s t read indirectly consumed, leaving a by a mirror arrangedeposit of carbon on ment according to the the wall. m e t h o d already deAnother similar scribed. test was made, and it It might be noted was found that even that the effect of niFIGURE 4. DETONATION b C T WITB HIQA-PRE~SURE OXYGEN, SAOWING a t 1 0 7 atmospheros COMBUSTION OF STEELVALVE trogen in reducing the
INDUSTRIAL AND ENGINEERING
February, 1935
explosive tendencies of high-pressure oxygen is extremely marked. For instance, in all of the high-pressure oxidation work with air carried on by the miters (24), both on laboratory and plant scale, not a single instance of an explosion in the reaction system has ever been noted. On the other hand, in one series of laboratory experiments involving high-pressure oxygen, about 10 per cent of the runs were interrupted by explosions. Steam possesses the same quenching property (26). For instance, a 25 per cent aqueous emulsion of a light lubricating oil containing 20 per cent emulsifier would not ignite up to 950" F. (510" C.), while the 'kolubleJ' oil alone had an S. I. T. in air of 790" F. (421" C,). One of the best safety precautions in explosive atmospheres is the introduction of live steam. DISCIJSSION OF RESULTS The S. I. T. serves as an interesting tool in indicating the structure of hydrocarbons. Masson and Hamilton (17) have shown that the normal paraffins have a considerably lower S. I. T. than the aromatics. Although some correlation was made with regard to knock rating of fuels, it is not likely that any such relationship could be established because knock suppression is apparently dependent more upon the compactness of the molecule than upon specific structural classification. For instance, a highly branched paraffinic hydrocarbon may have the same knock-suppressing effect as benzene, while the corresponding straight-chain paraffin would have knock-inducing properties ; yet the two paraffinic hydrocarbons would have S. I. T.'s close to each other and varying widely from that of the aromatic. The data of Tanaka and Nagai (20) showed the following values of spontaneous ignition temperatures in oxygen (in " C.): Benzene Cyclohexane n-Hexsne
Above 513 318
Yiethycyclopentane Methylcyclohexane
329 312
n-Heptane Isoheptane
298 290
285
From these and other results it might be concluded that for the same number of carbon atoms the decrease in S. I. T. would fall in an order somewhat as follows: aromatics, alkylated aromatics, naphthenes, alkylated naphthenes, straight-chain paraffins, branched-chain paraffins, and unsaturated aliphatics. The following table lists the auto-ignition temperatures in air obtained in the present apparatus with a number of hydrocarbons and oils from different sources: although the differences are not as sharp as with the members of lower molecular weight, distinctions can readily be made: F.
c.
Benzene .4bove 1030 Above 554 Diphenyl Above 955 Above513 Paraffin wax (m. p. 122O F., or 50' C.) 736 391 Cracking-coil t a r fraction 750 399 Synthetic oil (194 viscoslty a t 210° F. or 99O C.)5 850 454 800 427 Synthetic oil (86.8 viscosity a t 210° F.)" Prepared by polymerization of cracked wax.
CHEMISTRY
155
I n the light of these data, the curve in Figure 2 indicates that above 700" F. (371" C.) there is a sharp change in structure of petroleum oils, the fractions possibly consisting of polynuclear hydrocarbons which increase in complexity with boiling point. The values for both paraffinic and naphthenic fractions fall on the same curve in Figure 2, while two separate curves are necessary in Figure 3. This is because of the sharp difference between the gravities of the two types of oils for t'he same boiling ranges. With oxygen under pressure, spontaneous ignition of petroleum oils occurs so rapidly that it results in a detonation. This effect is especially catalyzed by iron and is aided by dispersion of the oil over a material having a large amount of surface. The presence of nitrogen greatly retards this detonation tendency. ACRKOWLEDGMENT The writers are indebted to P. K. Frolich who was mainly responsible for instigating the work, to W. C. Winning for valuable advice and assistance, and to H. G. Vesterdal for assisting in carrying out a number of tests described in the latter portion of the paper. LITERATURE CITED (1) Anonymous, IND.ENG. CHEM.,22, 473 (1930). (2) Anonymous, Proc. Am. SOC.Testing Materials, 28, 475, 915 (1928); 30, 788 (1930). (3) Araki and Otsu, J. I n s t . Petroleum Tech., 20, 74A (1934). (4) Aubert, Pignot, and Villey, Compt. rend., 185, 1111 (1927); Pignot, Ibid., 182, 376 (1926) ; J.usines gaz, 50, 293 (1926). (5) Bird, Proc. I n s t . Mech. Eng (London), 1926, 11, 955; 1927, 11, 1025. (6) Bridgeman and Marvin, IND. ENG.CHEM.,20, 1219 (1928). (7) Brooks, Bur. Mines, Circ. 2555 (Dec., 1923). (8) Chaloner, J. I n s t . Petroleum Tech., 18, 548 (1932). (9) Duffour, Compt. rend. congr. graissage, 1931, 471; Chem. Zen.fr., 1932,II, 2907. (9A) Dykstra and Edgar, IND.ENG.CHEM.,26, 509 (1934). (10) Edgerton and Gates, J. I n s t . Petroleum Tech., 13, 244 (1927). (11) Foord. Ibid., 18, 533 (1932). (12) Francis, IND. EXG.CHEY.,22, 896 (1930). (13) Hersey, Bur. Mines, Circ. 2507 (July, 1923). (14) Holm, Z. angew. Chem., 26, 273 (1913). (15) International Critical Tables, Vol. 11, p. 151, S e w York, McGraw-Hill Book Co., 1926. (16) Jakowsky and Butaler, Bur. Mines, Circ. 2521 (Sept., 1923). (17) Masson and Hamilton, ISD. ENG.CHEM., 19, 1335 (1927); 20, 813 (1928); 21, 544 (1929). (18) Moore, J . Inst. Petrolurn Tech., 6, 186 (1920). (19) Neumann and Estrovich, N a t u r e , 133, 105 (1934). (20) Tanaka and Nagai, J. SOC.Chem. I n d . J a p a n , 29, 266, 272 (1926). (21) Thompson, IND.ENG.CHEM.,21, 135 (1929). (22) Townend and Mandleku, Proc. Roy. Soc. (London), A143, 168 (1933). (23) Weerman, J . I n s t . Petroleum Tech., 13, 300 (1927). (24) Wiezevich and Frolich, IND. EKG.CHEM.,26, 267 (1934). (25) Wohl and von Elbe, Z . physik. Chem., B5, 241 (1929); Wohl. 2.Elektrochm., 30, 36 (1924).
RECEIVED September 20, 1934.
Dow CHEMICAL COMPANY
