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 C H E M I S T R Y
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593
pounds such as methane, ethane, ethylene, and similar hydrocarbons. (4)-Aromatic hydrocarbons. .......... (5)-The influence sf hydrogen on t h e above reacLIQUIDD I - N I T R O T O L U E N E Sample (a). . . . . . . . . . . . . . . . 1 5 . 0 1 15.14 15.01 15.13 15.40 15.45 . . . . . tions. Sample ( b ) , . . . . . . . . . . . . . . . . 15.39 TRI-NITROTOLUENE (6)-The transfer of heat in gas machines. Sample 1859.. . . . . . . . . . . . . . 1 8 . 3 6 ..... Sample 1860. .............. 1 8 . 3 0 18.38 In the work bearing on the primary decomposition of paraffin Sample I,. . . . . . . . . . . . . . . . . 1 8 . 4 1 18.48 hydrocarbons of high molecular weight the greater portion SamDle D . . ............... 18.24 18.28 LIQUIDTRI-NITROTOLUENE. ..... 16.18 16.19 16.21 16.18 of the experimental evidence points to a splitting of the carbon DI-NITROBENZENE ' chain with formation of olefin and paraffin. Conditions de(0)....................... 16.18 16.23 16.29 ( p ) , ...................... 16.39 16.39 ..... termine where the rupture takes place-low temperature and (m)....................... 16.51 16.58 16.63 high pressure tending to favor the splitting near the middle of NITROPHEWOL (.0.) ....................... 9.90 9.84 9.92 10.12 ( p ) . ...................... 9.99 10.08 . . . . . . . . . . the chain while a t lower pressures and higher temperatures the breaking off of low molecular weight hydrocarbons, such META-NITROANILINE. ................................. 20.04 19.92 MO~-O-NITRONAPHTHALEWE ........................... 8.08 8.04 as methane, ethane, and ethylene, but particularly methane DT-NITROWAPHTHALENE (1 : 5 ) ........................ 11.89 12.09 22.73 22.78 and ethane, becomes the important reaction. The members 22.70 DI-NITROANILINE (1 : 2 : 4 ) . . . . 22.63 18.31 18.28 18.24 PICRICACID .................. 18.36 of the paraffin series down to butane in all probability follow some such mode ol' reaction as this. A blank determination should be used t o correct The first problem to be considered in the study of the for nitrogen in reagents a n d i t is also advisable t o check secondary reactions, then, is the fate of the high molecular t h e method with pure picric acid or some other pure weight olefins which arise. It seems that the chief reaction nitro substitution compound. undergone by these high molecular weight olefins is a splitCooling during t h e addition of t h e zinc for reduc- ting into lower molecular weight olefins. A decomposition tion a n d t h e long standing before heating t h e acid into methane and compounds with two double bonds or one solution h a v e been found necessary i n order t o pre- triple bond also takes place. The intramolecular change of vent low results, a n d for t h e same reason t h e heating olefins into cycloparaffins is possible, but from the evidence available it is difficult to state what proportion of the should b e gradual. naphthene formation must be ascribed to this reaction.' T h e results given in t h e table indicate that the Hydrogenation of olefins takes place to some extent Polymmethod is especially applicable for picric acid a n d t h e erization of olefins to naphthenes occurs, also polymerization nitrotoluenes b u t is n o t good for tetra-nitroaniline, of the high molecular weight unsaturated compounds to tarry tetra-nitromethylaniline, and di-nitronaphthalene. compounds. The reactions which form the lower molecular weight hydroBUREAUOF MINES, W A S H I N G T O N carbons are in general more rapid in their progress than the reactions of decomposition of these lower hydrocarbons. THE DECOMPOSITION OF HYDROCARBONS AND T H E Methane, in particular, is stable under the action of heat a t those temperatures which are used in the various apparatus INFLUENCE OF HYDROGEN IN CARBURETED used in the manufacture of gas. Thus those reactions which WATER GAS MANUFACTURE' result in the formation of methane and ethylene reach a conBy M. c. m'H1TAEER AND E. H. 1 , B S L I E dition nearly corresponding to equilibrium proportions on acReceived June 1, 1916 count of the slow decomposition of ethylene and methane; Although numerous studies of hydrocarbon debut the system as a whole cannot be regarded as in equilibrium. composition have been made, no one, nor all combined, In considering the discussion of the reactions of the individual comprise a complete investigation. On account of hydrocarbons the effect of the presence of the end products t h e variety of t h e materials which h a v e been worked of a particular reaction must always be kept in mind. Also upon, t h e extreme complexity of t h e changes which the changing concentration conditions as the gas volume int a k e place i n a n y case, t h e differences in t h e types of creases with the progress of the changes involved must not be a p p a r a t u s used, a n d t h e a p p a r e n t inclination of m a n y forgotten. writers t o allow t h e reader t o do the greater p a r t of METHANE-The study of the influence of heat a t various t h e interpretation of t h e results, which i n m a n y cases temperatures on the hydrocarbon methane has usually been is well-nigh impossible, t h e presentation of t h i s ma- made with the idea in mind of finding the equilibrium proporterial i n condensed f o r m is obviously impossible i n tions of methane and hydrogen in the system carbon-hydrogena brief article, so t h a t only those points will be men- methane. The equilibrium proportions are never even approximated in experiments made after the manner of those discussed tioned t h a t a r e necessary for t h e interpretation of in the latter part of this paper, nor under the conditions maint h e results reported herein. In t h i s connection t h e tained in the technical production of coal, oil, and water gas. work previously done m a y be classified as follows: The preservation of methane is desired in all these cases, for (I)-The primary decomposition of high molecular its decomposition into carbon and hydrogen means loss of valuable carbon from the gas and the production of gases high weight paraffin a n d naphthene hydrocarbons. (2)-The various ideas in regard t o t h e mode of in hydrogen which are unsuited for distribution. Hence the reaction of t h e products of t h e primary decomposition. studies of the methane equilibrium are of interest only in so far as they indicate the tendency of methane to decompose under (3)-The thermal reactions of the simpler com- certain temperature conditions. 1 Authors' abstract of dissertation offered in p a r t fulfillment of t h e In summing up the work on methane it can be said that the requirements for t h e Ph.D. degree a t Columbia University, 1916. T h e chief reaction is the decomposition into carbon and hydrogen, dissertation itself contains detailed information as t o t h e results of t h e vaC,y, CHI --+ C f K", and that the reaction, ? C H I --+rious researches bearing on t h e subject and discusses fully their relations to each other. 3H2, takes place to a small extent only. PERCENTAGE NITROGEN FOUND BY AUTIIOR'S METHOD
MONO-NITROTOLUENE
............... 10.06 . . . . . . . . . . . 10.16 . . . . . . . . . . . . . . . 9.62
Sample ( a ) , ( b ) Redistilled., (c) C r u d e . .
10.11 10.19 9.61
10.20 10.14
10.06 10.20
~~
+
594
T H E J O L r R X i l L O F I Y D L ' S T R I A L A N D E,VGINEERIliG CHEATISTRY
Under the conditions oi operation of a carbureted lvater gas set very little methane is decomposed. Though the temperatures of the retort walls in coal gas manufacture are much higher than those in the interior of the carbureter and superheater of a water gas set it is obvious that the gases do not reach the temperature of the refractory surfaces. ETHANE-The work done on ethane seems to indicate that this gas is an intermediate product, passing to acetylene or ethylene. ETHYLEKE-It appears that a t t.emperatures up to 700' C. the dissociation of ethylene into acetylene and hydrogen is the most important reaction. Condensation also takes place to some extent. At higher temperatures the rate of the decomposition into carbon and methane is much greater, so this reaction plays an important part. ---At temperatures up to 700' C. acetylene undergoes a fairly rapid polyrmrization to benzene and its homologs. Decomposition into carbon and hydrogen is second in importance at these temperatures while hydrogenation to ethylene, ethane and methane is least important. $t slightly higher temperatures the importance of polymerization diminishes, while the decomposition into the elements and hydrogenation both increase. =It still higher temperatures, such as I rooo C., the decomposition into carbon and hydrogen is the important reaction. No discussion of the thermal reactions of propylene, diolefins, substituted acetylenes, propane, and high molecular weight tarry compounds wa.s found. The high molecular weight tarry compounds have been built pp by synthetic reactions. For this reason they are no doubt fairly stable compounds as regards the influence of heat, and in general pass on t,hrough the apparatus and into the tar. Haber has suggested that the chief reaction of the compounds of this class is a splitting off of hydrogen. z m O n l A T I C HYDRoCARBoss-Though the formation of aromatic hydrocarbons takes place only to a limited extent in water gas machines, and to but a slightly greater extent in coal gas retorts, the tars from these processes are important sources of the commercial aromatic hydrocarbons. The aromatic hydrocarbons contribute greatly to the illuminating value of a gas as determined in an open flame burner. Howe n x , should the calorific standard for gas service in the course of time tiecome general, the presence of the aromatic compounds in the gas would be of far less importance to the gas manufacturer than i t is to-day. These compounds contribute less to the heating value of the gas than the compounds from which they are lormed. Their chief importance would then lie in the better prices obtainable for the tars containing them. The reactions responsible for the aromatic hydrocarbons formed in the thermal decomposition of hydrocarbon oils are: iI )-Condensation of acetylenes, (2)-Dehydrogenation of naphtlienes, (j)--Decomposition of complex compouiids already containing the phenyl radical. Tolueiic, xylene, ethyl benzene, and similar compounds are rorrncd first and most easily. These by further change give rise to bemcne, naphthalene, and anthracene. With high molecular weight monocyclic compounds the general course of the reaction is toward compounds of lower molecular weight. In general, monocyclic compounds tend to go to polycyclic compounds. INFLUENCE OR HYDROGES ON THd THERXAL DECOMPOSITION O F HYDROCARBONS
The idea that an oil cracked in hydrogen or in inert gases
gave more valuable products has been prevalent for many years. In so far as the work of the several investigators allows us to draw conclusions it seems that hydrogenation of hydrocarbons such as ethylene and acetylene does take place, but that it is never a reaction of great importance. The fact, however, that hydrogen is actually absorbed when oils are cracked in
1701. 8,S o . 7
atmospheres of the gas shows that hydrogenation of some sort takes place. Possibly the higher unsaturated hydrocarbons are hydrogenated more readily. TRANSFER O F HEAT IN G 4 S MACHINES
The most striking feature of the literahre which records the result of investigations of hydrocarbon decompositions is the great differencebetween the results of various investigators who report that they have worked at the same temperature, and, iil general, under the same conditions. Irregularities too great to be attributed to the personal equation are of frequent occurrence, and these are in need of explanation. It is often suggested that these differences are caused by the catalytic effects of the materials of construction, but without doubt the catalytic effrct of contact surfaces has been overestimated. It is well known from general experience that these surfaces are always corered with a layer of hard carbon as a result of the decomposition of hydrocarbons. Hence the gases do iiot come into contact with an active material, but rather into contact with a dense layer of carbon deposit which is inactive as a catalyzer. Unquestionably many of the effects ascribed to catalysis are in reality due to the effectiveness of the heating by conduction and convection close to the surfaces of the refractory materials. The importance of radiant energy in causing hydrocarbon reactions has also been over-emphasized most consistently in the literature of the gas industry. Too little attention has bcen paid to the methods of making temperatwe mei:szi~emrnts, and also to the interpretation of temperature measurements made in certain ways. Thus it is obvious that a metal pyrod with a rnetal casing or a protective sheath of solid material such as quartz will absorb many times as much radiant energy as the gases in the heated space, and therefore indicate a temperature considerably above the true temperature of the gases. A41so the conduction of heat along the metal pyrod casing is more effective than the conduction through a gas. In general, then, it would seem that the radiation does not play as important a part in transferring heat as has been taken for granted. Conduction and convection are largely responsible for this transfer, and they are helped to some extent by the dissociation reactions of the hydrocarbons. Catalysis has been greatly overrated. The influence on reaction rates supposedly brought about in this fashion can be better understood if the true mechanism of heat transfer is kept in mind. The different results of experimental investigations are also often easily understood if the shape and size of the apparatus is considered in its relation to heat transfer. T h e recent work1 done i n connection with t h e commercial production of gasoline a n d aromatic hydrocarbons has been t h e most exhaustive ever attempted. However, these investigations haT-e not been carried out from t h e standpoint of gas production. It is scarcely necessary t o discuss t h e importance of a thorough understanding of t h e possibilities of controlling t h e decomposition of hydrocarbons for t h e obtaining of t h e particular products desired. T h e most profitable utilization of an oil is of extreme importance t o t h e water gas manufacturer. T h e control of t h e cracking of an oil is t h e thing of first importance t o t h e manufacturer of oil gas in a n y of t h e various processes. T h e effect of t h e presence of hydrogen on t h e products derived from an oil is of great importance t o t h e water gas manufacturer and t h e all-oil-water-gas maker. Also i t is generally recognized t h a t t h e carboniza1 Whitaker and associates a t Columbia University, and Rittman a n d associates, U. S. Bureau of Mines.
J u l y , 1916
Y D E N GI Y E E R I N G C H E M I S T R Y T H E J O C R J A L OF I N D C S T R I A L A i
tion of coal a n d t h e combustion of coal and oil a r e allied problems, a n d t h a t t h e results of a s t u d y of hydrocarbon decomposition are of direct application i n these connections. T h e effect of t h e introduction of hydrogen i n t o t h e carbonizing retorts can also be seen b y a s t u d y of t h e d a t a given in this paper. Brief mention of t h e experimental work of a few investigators will serve t o show t h e importance of t h e subject of hydrocarbon decomposition t o t h e users of coal for gas making purposes or as a fuel. Jones a n d Wheeler’ have extracted solid paraffins f r o m several British coals b y means of pyridine a n d chloroform. Pictet a n d Ramseyer2 have isolated hexahydrofluorene from t h a t portion of a gas coal which was soluble in benzene. T h e same hydrocarbon has been identified b y t h e m in t h e t a r obtained b y t h e 1 0 ~ temperature ~’ distillation of coal in a v a c u u m . Burgess a n d Wheeler3 found t h a t paraffin hydrocarbons were predominant among t h e primary decomposition products of coal. T h e same authors4 found a considerable evolution of higher olefins when coal was distilled a t low temperatures. E , Bornstein6 discussed t h e decomposition of coal a t temperatures u p t o 450’ C. He found t h a t t h e gaseous products consisted of j t o 14 per cent heavy hydrocarbons, j j t o 76 per cent paraffins, a n d j t o 16 per cent hydrogen. Jones a n d Wheeler6 distilled coals a t temperatures u p t o 4 jo’ C . in a r a c u u m of j t o 40 m m . of mercury, a n d obtained 6.5 per cent b y weight of a t a r which consisted of 2 j per cent olefin hydrocarbons a n d a n equal proportion of naphthenes a n d paraffins. Pictet a n d Bouvier? have conducted experiments similar t o those of Jones a n d Wheeler, a n d found a large proportion of hydroaromatic or naphthene hydrocarbons in t h e tars. Porter a n d Taylor8 found t h a t t h e primary decomposition products of coal were complex easily liquefiable paraffins, hydrocarbons with smaller amounts of water, carbon dioxide a n d hydrogen. One of t h e points in t h e propaganda of t h e various recently developed low temperature carbonization schemes has been t h e high percentage of light hydrocarbon oils which might be recovered from t h e t a r s a n d used for motor spirit. T h e gases obtained in these processes are also rich in higher hydrocarbons. Lewesg gives t h e analysis of a gas which contained I O . I per cent of t h e members of t h e paraffin series higher t h a n methane. White, P a r k , a n d Dunkerley’o found t h e e t h a n e content of t h e gases of low temperature carbonization processes t o r u n from 11 per cent t o 47 per cent. P a r r a n d Olin’l have found t h a t approximately I O per cent of a light hydrocarbon oil was obtained from tars made in low t e m p e r a t u r e carbonization experiments between 400 a n d 500’ C. J . Chem. Soc., 103 (1913), 1704.
Be?‘., 44 (1911), 2486; Gas World, 66 (1911), 131. J. Chem. SOL, 99 (1911), 649-667. I b i d . , 106 (1914), 131-140. 2. angew. Chem., 17 (1904). 1520. J . Chem. Soc., 106 (1914). 140-151, 2562-2565. 7 Corn&. rend., 167 (1913). 779. 8 Proc. Am. Gas Inst., 1914, 234-288. 9 “Carbonization of Coal,” p. 164. 10 Pvoc. Michigan Gas Assoc., 17 (1908), 83. 11 “Coking of Coal at Low Temperatures,” Bull. 79, Univ. of Illinois Experiment Station, 1915. ?
3
PURPOSE O B THE
PRESENT
59 5
IWVESTXGATIOS
I t is t h e purpose of this in\-estigation in general t o show what results may be expected in t h e decomposition of a n oil if temperature, r a t e of oil feed, a n d concentration of hydrogen are t a k e n into account and carefully controlled, More specifically it is proposed t o show: I-The variation of t h e composition of t h e gases made from oil a t constant temperature a n d pressure with changing r a t e of oil feed. 2-The effect of changing t h e temperature on t h e composition of gases made f r o m oil alone at constant oil feed a n d constant pressure. 3-The variation in t h e volume of t h e various gases obtained per cc. of oil fed a t constant temperature and pressure b u t with changing r a t e of oil feed. 4-The effect of changing temperature on t h e volume of various gases obtained per cc. of oil a t constant r a t e of oil feed a n d constant pressure. ;-The extent t o which hydrogen is absorbed a t a n y particular concentiation, a n d t h e effect of changing t h e concentration. 6-The influence of hydrogen of certain concentration on t h e n u m b e r of cc. of t h e various gaseous components obtained per cc. of oil, and t h e relations between this a n d change of concentration of hydrogen, change of temperature, a n d change of oil rate. 7-The results of a s t u d y of t h e mean molecular weight of t h e olefins in t h e gases a t certain temperat u r e , and t h e influence of t h e presence of hydrogen a n d change of t h e r a t e of oil feed in this connection. 8-The proportion of aromatic hydrocarbons present in t h e gases a n d t h e influence of t h e presence of hydrogen a n d changing oil r a t e in this connection. 9-The percentages of t a r formed a t different temperatures a n d rates of oil feed, a n d t h e influence of hydrogen on t a r formation. P L A N AND SCOPE O F T H E E X P E R I I I E N T A L W O R K
T h e plan of t h e present work was t o s t u d y t h e decomposition of paraffin hydrocarbons under atmospheric pressure, and a t a number of temperatures and varying oil r a t e ; a n d under identical conditions, to investigate t h e effect of t h e presence of hydrogen of different concentrations o n t h e decompositions of t h e paraffin hydrocarbons. T h e working temperatures were 621’ C . , 7 2 3 ’ C. a n d 8 2 5 ’ C. T h e temperatures used in t h e commercial manufacture of water gas lie between 7 0 0 a n d 7 7 j ” C., a n d are t h u s well within t h e temperature range of these experiments. At 9 2 7 ’ C. t w o runs were made, b u t t h e separation of carbon in t h e furnace t u b e was SO rapid it was impossible t o keep t h e tube open while t h e adjustments for t h e hydrogen-oil gas runs were made. T h e hydrogen concentrations are discussed under t h e caption “ T h e Hydrogen Concentration.” T h e method used was t o adjust t h e furnace t o t h e proper conditions a n d t o r u n t h e oil in a t t h e desired rate. T h e oil gas so made was collected. Without stopping t h e flow of oil, hydrogen was t h e n admitted i n proper concentration a n d t h e gas produced b y cracking t h e oil in hydrogen collected in a second gasometer.
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The two gases were t h u s made under identical furllace conditions. T h e volumes of t h e t a r s formed were measured. T h e straight oil gas runs made in connection with this research mere a repetition of those previously made b y Dr. C. M.=Ilexander (private communication), the results of whose work have not as yet been published. T h e experimental d a t a of t h e work recorded here are in excellent agreement with those of Dr. Alexander. APPARATVS AND PROCEDURE
used in these experiments was designed a n d built b y TThitaker a n d Alexander, a n d used b y t h e m in a s t u d y of t h e time factor in t h e making of oil gas.' For a detailed description of t h e furnace construction reference must be h a d t o t h e original article. T h e heating was effected b y t h e passage of a n alternating current from a single phase, 60 cycle, 50 kilow a t t generator. T h e current passed through t h e carbon resistor t u b e of t h e furnace was readily controlled b y means of a field rheostat. T h u s a very accurate regulation of t h e temperature was obtained. Fluctuation limits of I or 2' C. v e r e attained by careful operation. A constant feed of oil was readily maintained b y means of t h e static head a n d feed regulator. T h e oil was vaporized in t h e prevaporizer. T h e hydrogen gas was introduced into t h e sight feed just belovr t h e oil feed valve where it mixed with t h e oil vapors coming from t h e prevaporizer. and passed on i n t o t h e heated tube of t h e furnace. T h e gas velocity in t h e t u b e could be calculated from its dimensions ( I in. I. D. X 38.5 in. long), a n d t h e t o t a l gas rate. Certain features of t h e design of t h e furnace, other t h a n t h e fact t h a t it was susceptible t o exact control, which made it particularly suitable for t h e s t u d y of t h e reactions of hydrocarbon decomposition both from a theoretical standpoint a n d from a n operating standpoint, must be pointed out. I t is evident t h a t t h e gas in passing through t h e carbon t u b e is subjected t o a set of conditions similar t o those existent in t h e interior of t h e water gas carbureter and superheater; i. e., heated b y carbon-coated passageway malls. Though t h e size of t h e furnace t u b e is less t h a n t h e voids in t h e checker bricking in t h e gas machine. t h e general conditions are t h e same. Both from a theoretical standpoint a n d practical standpoint t h e s t u d y of t h e kinetics of these various hydrocarbon reactions is greatly t o be desired as has been pointed o u t elsewhere i n this paper. T h e furnace was designed in such manner as t o avoid catalytic effects as completely as possible, a n d is therefore suitable f o r a s t u d y of t h e kinetics of such relations. I I E A S U R E N E N T O F G A S i70Lmms-The gases from t h e runs were collected in j - C U . ft. holders. T h e dimensions of these t a n k s were carefully t a k e n a n d the vo!umes computed. A stationary millimeter scale mas attached t o t h e t a n k s t a n d a r d , a n d a rigid pointer to t h e movable heil so t h a t readings could be taken a t given time intervals, a n d t h e gas rates and t o t a l volumes calculated. X wet meter was used for t h e measurement of t h e THE FURNACE
1
T a ~ JOURNAL, s 7 (1915), 484-495.
Vol. 8, No. 7
volume and r a t e of t h e hydrogen flowing into t h e m a chine. This meter was filled with kerosene t o avoid t h e aspiration of water vapor m t o t h e furnace. T h e oil level in t h e meter mas adjusted carefully a t all tlmes, a n d t h e meter kept perfectly level. T h e meter was calibrated against t h e t a n k which was used for t h e collection of t h e mixed oil-hydrogen gases. T h e hydrogen was allowed t o flow i n l o the meter, through t h e furnace heated t o 800' C. a n d into t h e receiving t a n k , readings being t a k e n , a t short intervals, of t h e meter r a t e a n d t a n k rate. This calibratlon was checked from time t o time and f o u n d not t o v a r y appreciably. T H E P Y R O D A N D ITS CALIBRATION-The temperature measurements were made with a base metal thermocouple attached t o a direct reading Wilson-hIaeulen instrument. The thermocouple was calibrated by checking it against t h e boiling point of sulfur (444.6" C.) a n d against t h e melting point of sodium chloride (800' C.). T h e readings of t h e thermocouple a t these points were 4 2 5 a n d 77j' C., respectively. Using these d a t a a c u r e \vas plotted from which t h e t r u e temperature could be read corresponding t o temperatures as read from t h e instrument. T h e temperatures a t which runs mere made were those observed when t h e pyrod projected through a suitable stuffing box into t h e lo\yest of t h e sight tubes. A hole the size of t h e e n d of t h e pyrod was made in t h e carbon resistor t u b e , a n d t h e pyrod allowed t o project about in. into the interior of t h e resistor t u b e . T h e upper portion of t h e resistor t u b e was about 25-30' C. colder t h a n t h a t p a r t of t h e t u b e where t h e pyrod was inserted, due, n o d o u b t , t o t h e cooling effect of t h e incoming gases and t o t h e endothermic reactions taking place in t h a t p a r t of t h e t u b e . T H E H Y D R O G E K used in these experiments was a very high-grade electrolytic gas. A4nalyses showed it t o contain 99.9 t o 100.0 per cent hydrogen. T H E OIL used was a water-white oil (0.8000 sp. gr.), which boiled between 150 a n d 265' C. METHOD OF OPERATION-The furnace T i & S first heated u p well a n d t h e jacket cooling water adjusted properly. When a constant temperature I O t o 30' above t h e temperature a t which t h e r u n was t o be made h a d been established, t h e oil valve was opened a n d adjusted t o t h e proper r a t e of flow. T h e temperature of t h e furnace was t h e n regulated till i t remained constant a t t h e desired point. T h e gases formed during thi5 preliminary operation were r u n t o a waste t a n k , a n d t h e t a r discarded. 4 s soon as all t h e proper operating conditions h a d been established, t h e gases were run i n t o a gas holder a n d readings of t h e oil r a t e , gas r a t e a n d t e m perature were t a k e n a t suitable short intervals. T h e pressure was always atmospheric. T h e temperature was noted a t frequent intervals. a n d a n y necessary regu!ations of t h e field rheostat mere made. When t h e proper a m o u n t of gas h a d been collected, t h e gas was again sent t o t h e waste gas holder, a n d t h e t a r removed f r o m t h e t a r drip. Hydrogen was t h e n a d m i t t e d , flowing from t h e compressed hydrogen t a n k through t h e reducing valve a n d meter a n d i n t o t h e admixer a t t h e t o p of t h e furnace tube. When t h e
July, 1916
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
Methods of temperature measurement must n o t be neglected. Above all it must not be assumed t h a t a particular temperature as measured will produce t h e same results in two different machines. T h e experiments recorded in this paper merely show t h e possibilities in t h e decomposition of a hydrocarbon oil. T o obtain particylar results on a commercial scale would necessitate a great deal of thought as t o t h e proper design for t h e machine t o be used.
r a t e of t h e hydrogen flow a n d all t h e other conditions h a d been adjusted, t h e gas passing was run into a second gas holder. Readings of t h e oil rate, hydrogen rate, total gas rate, a n d temperature were again t a k e n a t suitable intervals. T h u s a n oil gas a n d a hydrogen-oil gas were made under exactly t h e same operating conditions. These gases were analyzed 18 t o 2 0 hrs. after making. Analyses were made on low temperature, fast oil rate, gases a t periods of one t o two hours after making t o see if t h e standing for longer periods caused a n y difference i n t h e analytical results. N o appreciable difference was found. RELtlTION
BETWEEN
THE
EXPERIMENTAL
T H E H Y D R 0 G E K C 0 N C E N T RAT1 0 X
APPARATUS
A K D T H E CORIYERCIAL A P P L I A N C E
Frequently i t is a difficult m a t t e r t o reproduce experimental results in technical operation. It is with t h e object of calling attention t o salient points which must be kept in mind in order t h a t t h e results recorded here m a y be reproduced in a commercial appliance t h a t t h e paragraphs which follow are written. Experimental results show t h a t t h e time factor is all important. B u t it must be remembered t h a t t h e furnace t u b e used in these experiments was only 3 0 in. long, whereas t h e column of checkerbrick in t h e car-, bureter a n d superheater of t h e water gas set is m a n y times t h a t length. Hence even though a pyrometer m a y record t h e same temperature in this furnace a n d in t h e checkerbrick of a commercial machine it would not be expected t h a t t h e gases would have t h e same composition. The diameter of t h e furnace t u b e used in these experiments was I in. This, however, was soon carbonized so t h a t i t mas more nearly 3//4 in. T h e interstices in t h e checkering of commercial machines are of greater sectional area t h a n a circle of 3//4 in. diameter. Hence t h e opportunity for heat transfer i n t h e checkerbrick is not so good as in this experimental furnace a n d i t would be expected t h a t a longer column of checkerbrick t h a n was necessary in this furnace would be necessary t o produce a given result, all conditions being t h e same. T h e actual time of contact of t h e gases with heated surfaces is all i m p o r t a n t , b u t it is a very complicated function of t h e r a t e of oil feed, t h e amount of blue gas introduced, t h e volume of t h e checkerbrick voids, a n d t h e temperature. Commercial operation demands t h a t a n apparatus have a reasonable gas making capacity, a n d for this reason t h e higher oil rates are most desirable. On t h e other hand, with high oil rates more t a r is always produced t h a n a t low oil rates, which makes t h e use of the oil uneconomical. It is not improbable t h a t t h e best results could be obtained b y designing one apparatus with proper control suitable t o t h e production of certain gaseous products, a n d a second a p p a r a t u s which would use t h e t a r from this first machine as t h e carbureting oil. An examination of t h e t a r s formed in t h e experimental apparatus a t medium t o high rates of oil feed have led t o t h e belief t h a t this would not be impracticable.
597
T h e introduction of hydrogen in certain concentration is a question which must be regarded from a t least two standpoints; i. e . , t h e experimental a n d t h e technical or operating standpoints. I n t h e manufacture of carbureted water gas t h e oil is cracked in a n atmosphere of carbon monoxide a n d hydrogen. T h e final gas is roughly hydrocarbons, hydrogen a n d carbon monoxide. The hydrogen a n d hydrocarbons are t h u s present in t h e approximate ratio of I volume t o I volume in t h e final gas. I n addition there is present I volume of carbon monoxide, t h e influence of which has never been exactly determined b y a comprehensive study. I n these experiments i t was thought desirable t o s t u d y two concentrations of hydrogen: (I)- I Volume Hydrogen : z Volumes (oil gas tar gas) (2)z Volumes Hydrogen : I Volume (oil gas tar gas) The experimental difficulties were such, however, t h a t t h e introduction of hydrogen in exactly these proportions was practically impossible, for, with change in temperature, t h e a m o u n t of gas produced from a given quantity of oil a t a particular rate changes, while with change in oil r a t e a t constant temperature t h e amount of gas produced from a given quantity of oil changes. Also t h e gas formed from a certain amount of oil is different when t h e oil is d6composed alone or in a n atmosphere of hydrogen. Furthermore, t h e concentration of hydrogen in t h e upper part of t h e furnace t u b e is much greater a t a n y time t h a n i t is in t h e lower p a r t of t h e tube, for as t h e oil vapors pass through t h e t u b e a progressive decomposition takes place with formation of a greater volume of hydrocarbon gases. It would therefore be necessary t o make several trial runs a t each oil r a t e at each temperature t o determine t h e proper hydrogen rate. When it is considered t h a t each r u n of t h a t sort would consume several hours' time, t h e impracticability of this method of procedure is apparent. Furthermore, in commercial operation t h e two factors ,which would be susceptible t o control would be t h e r a t e of introduction of blue gas and the rate of introduction of t h e oil. So i t was decided t o base t h e hydrogen concentration arbitrarily on t h e oil rate. After some trials a t 7 2 3 ' C., t h e following equations relating t o t h e hydrogen rate a n d t h e oil r a t e were decided upon: ( I ) To approximate I Vol. Hydrogen : z Vols. (oil gas tar gas) Oil rate in cc. per minute Hydrogen rate in liters 5.28 __ = ) per minute. tar gas) (2) To approximate 2 Vols. Hydrogen : I Vol. (oil gas Oil rate in cc. per minute Hydrogen rate in liters
+ +
~
+
+
I .76
=)
per minute.
T H E J O U R N A L O F 1 - V D I ‘ S T R I A L A,VD E Y G I N E E R I X G C H E M I S T R Y
5 98
One set of runs only was made a t 621’ C. and this a t t h e supposed ratio I Vol. H y d r o g e n : 2 l’ols. Gas. T h e lower curve in Fig. j is plotted from t h e equation given under (I) above. T h e points represent t h e actual hydrogen rates a n d show how closely it was possible t o adjust t h e hydrogen r a t e t o t h a t desired as calculated from t h e oil rate. T h e upper curve in Fig. j shows t h e actual ratio of hydrogen t o (oil gas t a r gas). I n t h e furnace t h e hydrocarbons which compose t h e t a r are of course gaseous a n d t h e x-olume of this gas is calculated on t h e assumption t h a t t h e specific gravities of t h e liquid t a r s are 0.80 (water = I ) a n d t h a t t h e mean molecular weight oE t h e hydrocarbons contained in t h e t a r is 1 4 2 ; i. e., t h a t t h e as-erage’molecule contains I O carbon atoms. T h e straight line a t ordinate 0 . ; is t h e theoretical curve for t h e value of t h e ratio of hydrogen t o (oil gas t a r gas). It can be seen t h a t t h e value of this ratio more nearly approximated unity t h a n it did 0.5 in ihese runs. B second series of runs with t h e value 2 for t h e ratio of hydrogen t o (oil gas t a r gas), was not made for t h e reason t h a t from t h e results a t higher temperatures it was judged t h a t t h e chief effect of more hydrogen a t 621’ C. would be t o blow t h e vapors through t h e heated t u b e faster n-ithout producing extensire chemical change. Since there \vas approximately I volume t a r gas), in these of hydrogen t o I volume of (oil gas runs a t 621’ C.? t h a t is, practically t h e relations existent i n t h e carbureter a n d superheater of t h e water gas set, it was thought t h a t this series of runs sufficed t o show t h e possibilities of a temperature in t h e neighborhood of 6 2 1 ’ C. for purposes of gas manufacture. Curves A in Figs. 6 a n d 7 are t h e plots of t h e e q u a tion under ( 2 ) given above a t 7 2 3 a n d 825’ C., respectively, a n d curves B in Figs. 6 a n d 7 t h e plots of equation (I) above a t those temperatures. T h e points show how closely t h e actual hydrogen rates approximated those calculated b y these equations. T h e lower curye in t h e upper half of Fig. 6 shows t h a t t h e actual value of t h e ratio of hydrogen t o (oil gas t a r gas) approximated very closely t o t h e value 0 . j drawn horizontally on t h e ordinate 0 . j . T h e upper curve i n t h e upper half of Fig. 6 shows t h a t a t low oil rates too little hydrogen was introduced t o make t h e value of t h e ratio hydrogen t o (oil gas t a r gas) equal t o 2.0, and a t high oil rates t h a t too much hydrogen was introduced. T h e actual values of t h e ratio hydrogen t o (oil gas t a r gas) in t h e second series of runs a t 825’ C.are shown in t h e curves in t h e upper half of Fig. 7. I n the first series of runs t h e value of t h e ratio lies between 1.0 a n d 2.0, whereas it was intended t h a t i t should be 2 . 0 . I n t h e second series t h e desired value 0 . j is Yery closely approximated a t all oil rates.
T‘ol. 8, KO.7
+
Oii R a t e - c c .
iOeY
minute
--
+
+
+
s 2
30
20
4 4%
u io
ar
O//Rate - cc. per minute t le
-
i
+
+
+
ANALYTICAL P R O C E D U R E F O R GASES
During t h e early part of t h e lvork recorded in this paper t h e method of gas analysis was t h e ordinary one employing t h e Hempel burette with single a n d double pipettes for t h e absorbing reagents. T h u s
Oil
Rate
-
c c . per
minute
EFPECT OF DIFPERENT HYDROGEN CONCENTRATIONS R A T E S A T THREE TEXPERATURES
WITH V A R Y I N G 011,
D a t a for Curves Calculated on Two Bases
t h e carbon dioxide was removed b y a solution of 1 p a r t of KOH in 2 parts of water, t h e unsaturated a n d aromatic hydrocarbons b y fuming sulfuric acid with 20 per cent free S O 3 , t h e oxygen b y alkaline pyrogallol made u p in accordance vi-ith Hempel‘s directions,’ a n d t h e carbon monoxide absorption in ammoniacal cuprous chloride prepared according t o Tinkler.2 A portion of t h e residual gas was t h e n mixed with oxygen, and slowly passed back a n d forth over palladium black in a glass t u b e immersed in water at a temperature of about 8j-90’ C. After t h u s removing t h e hydrogen t h e gas mixture was exploded 1 2
Dennis’ “Cas Analysis,” p . 160. C. n’inkler, “Handbook Tech. G a s Anal.,” translated by Lunge, 13. 7.3.
July. 1916
T H E J O U R N A L O F I N D U S T R I A L ALVD E N G I N E E R I N G C H E M I S T R Y
over mercury, a n d the’ resulting carbon dioxide absorbed in potassium hydroxide. “ C A R B O N XONOXIDE”--AS t h e work progressed it became evident t h a t this method could be improved upon. I t was difficult t o understand where t h e carbon monoxide, varying from 0 . 2 per cent t o 1.9 per cent as shown b y t h e cuprous chloride absorption, could have come from. T h e furnace was t i g h t , a n d in a n y case there would be a slight positive pressure outwards, so t h a t t h e ingress of air in more t h a n small a m o u n t s was o u t of t h e question. T h e only other possible source of oxygen was t h e water in t h e oil used. However, had t h e carbon monoxide arisen t h u s from t h e reaction of s t e a m on t h e carbon it would have been present in larger a m o u n t a t 800’ C. t h a n a t 600” C. &o there should have been some relation between t h e percentages of carbon monoxide a n d carbon dioxide. B u t carbon monoxide, as indicated b y t h e absorption in ammoniacal cuprous chloride, was present in largest a m o u n t a t 600” C., in smaller amounts a t j o o O C., a n d least of all a t 800’ C. Also it was noticed t h a t at a n y particular temperature t h e carbon monoxide tended t o be highest when t h e oil r a t e was highest. However, there was no regular variation of this sort as there was with t h e other components of t h e gaseous mixtures formed. Hence i t appeared t h a t t h e “carbon monoxide” formation as shown b y t h e absorption in t h e ammoniacal cuprous chloride was not solely a function‘of t h e ftirnace conditions. F. C. Phillips’ s t a t e d t h a t cuprous chloride solution dissolved t h e higher members of t h e paraffin series t o some extent. G. A. Burrell and F. VI. Seibert2 f o u n d t h a t cuprous chloride solution caused a contract i o n of 0 . j t o 0 . 6 per cent in Pittsburgh natural gas. T h e y have also shown t h a t a two-minute contact of cuprous chloride solution with pure e t h a n e caused a loss in volume of 0.6 per cent a n d t h a t i n five minutes t h e contraction was 1.4 per cent. Our experimental work showed t h a t those gases which would be expected t o have t h e largest proportion of high molecular weight hydrocarbons, i. e., those gases made a t low temperatures a n d fast rates of oil feed, were also those which showed t h e highest percentages of “carbon monoxide.” It appeared certain, therefore, t h a t t h e contractions found on passing t h e gases i n t o t h e ammoniacal cuprous chloride solution were in reality largely due t o absorption of paraffin hydrocarbons such as ethane, propane, and b u t a n e rather t h a n t o carbon monoxide. T h e use of ammoniacal cuprous chloride was therefore abandoned, a n d t h e carbon monoxide a n d hydrogen determined b y Jaeger’s fractional combustion method somewhat as described b y H. C. Porter and G. B. T a y 1 0 r . ~ I n place of t h e vertical Xichrome resistance heater with t h e inverted U-tube t o hold t h e copper oxide, a horizontal heater with a straight copper oxide t u b e was used as shown in t h e accompanying drawing. T h e difference in temperature between t h e b o t t o m “Oil and Gas Levels,” W. Va. Geol. Survey, 1 A (1904), 5 5 2 . ” T h e Sampling and Analysis of Mine and Katural Gases,” Bur. of Mines, Bull. 42, 46-77. * Proc. Am. Gas Inst., 9 (1914), 2 5 5 ; THISJOURNAL, 6 (1914). 845-8. e
599
a n d t o p of t h e vertical heater was great enough SO t h a t when t h e oxide was a t t h e proper temperature i n one p a r t of t h e containing t u b e , it was either too hot or too cold in other parts of t h e tube. With t h e horizontal heater a n d t h e copper oxide t u b e running concentrically through it no such difficulty was experienced, nor did t h e water formed during t h e combustion cause a n y trouble. T h e fractional combustion of gaseous mixtures o r e r copper oxide consumes a little more time with gases which are low in hydrogen a n d high in paraffins t h a n does t h e method in which t h e cuprous chloride pipettes a n d t h e palladium black are used. However, as t h e average time for carefully made analyses is not over 45 mins., this cannot be considered as a serious disadvantage. I t was found t h a t a temperature of 27j-280’ C. burned t h e carbon monoxide a n d hydrogen t o carbon dioxide a n d water without affecting t h e methane and other paraffin hydrocarbons present. After passing t h e gases over t h e oxide till no further contraction took place, t h e y were allowed t o cool t o room temperature, a n d t h e volume read. T h e contraction a t this
ApparatvJ for Fiact~oncll Combustion
o t c o an4 H~ o w cuo
point equals t h e per cent of hydrogen in the gas. T h e carbon dioxide was t h e n absorbed in potassium hydroxide. This contraction is equal t o t h e per cent of carbon monoxide in t h e gas. T h e importance of allowing t h e gases t o reach room temperature can readily be seen. Otherwise t h e contact with t h e potassium hydroxide will cause a contraction due t o t h e lowering of t h e temperature of t h e gas. T h e method of burning t h e carbon monoxide and hydrogen over copper oxide has recently been discussed b y G. A . Burrell a n d G. G. 0berfell.I Their experiences with this method were apparently similar t o ours. I n t h e case of many of t h e gases obtained in t h e experimental work, t h e gas residue after t h e fractional combustion was small enough so t h a t t h e whole of it could be mixed with oxygen a n d exploded over mercury. Here again t h e method of burning over copper oxide presents a distinct advantage over t h e methods first mentioned above, for in t h e combustion with palladium black it is necessary t o mix t h e gas with oxygen previous t o t h e fractional combustion of t h e hydrogen. T h u s a much smaller proportion of t h e gas could be p u t through t h e partial combustion and explosion analysis, in consequence of which accuracy was sacrificed. Accuracy at this point was particularly desired in order t o calculate t h e mean molecular weight of t h e paraffins. 1
TXISJOURNAL. 8 (1916), 228-231.
600
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
AROMATIC HYDROCARBONS-At t h e outset of this work t h e desirability of determining t h e extent of t h e formation of hydrocarbons of t h e benzene series was evident. A careful survey of t h e literature, however, showed t h a t none of t h e methods proposed had, given satisfaction in t h e hands of all who h a d worked with them. I t was not until t h e work recorded here was nearing completion t h a t t h e method proposed b y Hulett a n d developed by t h e Bureau of Mines‘ came to our attention. This method was used for t h e determination of t h e aromatics in t h e gases from one series of runs a t 8 2 j ’ C. T h e procedure in brief is t o evacuate t h e a p p a r a t u s m-ith a good p u m p , after which t h e gas is a d m i t t e d a n d t h e temperature a n d barometer readings noted. T h e gas is allowed t o s t a n d for some t i m e (in these determinations 2 t o 3 hrs.), in order t h a t t h e phosphorus pentoxide may remove t h e water vapor completely, and t h e n immersed for I O t o 1 5 mins. in a mush of carbon dioxide snow in acetone contained in a Dewar flask. A t t h e e n d of this time t h e gases are sucked off by means of t h e p u m p . T h e bulbs are t h e n removed from t h e cold b a t h and allowed t o come t o room temperature. T h e temperature is noted a n d t h e partial pressure of t h e volatilized aromatics is read on t h e short a r m manometer. F r o m this d a t a t h e volumetric percentage of these components ’in t h e gas can be calculated. A rotary oil p u m p which gave n vacuum of less t h a n I mm. of mercury, a n d t h a t in less t h a n a minute, was used in these experiments.
X E A K bIOLECULAR WEIGHT O F THE O L E P I X S
When t h e analysis a n d t h e specific gravity of a gas are known t h e mean molecular v e i g h t of t h e heavy hydrocarbons of t h e gas can be calculated. When, in addition t o t h e percentages of carbon dioxide, heavy hydrocarbons, oxygen, carbon monoxide, hydrogen, methane, ethane, a n d nitrogen, t h e percentage of aromatics is known, t h e mean molecular weight of t h e olefins a n d acetylenes can be calculated. In determining t h e specific gravity t h e temperature of t h e gas a n d t h e barometer reading should be t a k e n , a n d t h e gas should be thoroughly shaken with water in order t o s a t u r a t e i t with water vapor a t t h e temperature of the room before introducing i t i n t o t h e specific gravity a p p a r a t u s . Time should be allowed for t h e subsidence of a n y mist formed during t h e agitation with water. T h e method used for t h e determination of t h e specific gravity was t h e so-called effusion method a n d the a p p a r a t u s was similar t o t h a t described by P a n nertz.2 T h e orifice was made b y pricking a piece of t h i n platinum foil with a needle, and t h e n beating t h e foil with a small leather mallet till t h e t i n y hole was visible only when held u p t o a strong light. This foil was mounted on t h e end of a short brass t u b e fitting with a carefully t u r n e d brass screw cap luted in with litharge a n d glycerol cem-ent. Certain errors are inherent in t h e experimental methods used, I n t h e first place it is well known t h a t fuming sulfuric acid absorbs higher paraffins during 1 G. A. Burrell, F. %S. Seibert, and I. W. Robertson, “8nalysis of Xatural Gas and Illuminating Gas b y Fractional Distillation a t Low Temperatures and Pressures,” TeciznicaE Paper, 104, 26-27. 2 J . fur Gasbel.. 48 (190.5), 901.
Vol. 8, No. 7
t h e determination of t h e heavy hydrocarbons.’ I t was t h o u g h t t h a t t h e use of bromine water might obviate this difficulty, b u t analyses on 621’ C. gases made b y b o t h methods checked t o within 0.1 per cent showing t h a t t h e t w o reagents were having similar effects. F. C. Phillips2 says t h a t bromine water a b sorbs t h e higher paraffins. Disagreement between analyses made by t h e use of bromine water a n d b y fuming sulfuric acid m a y be occasioned b y t h e fact t h a t bromine water does not brominate benzene. I n t h e analyses made in these experiments there is little d o u b t b u t tha.t t h e benzene would have been completely scrubbed down on account of t h e time a n d shaking necessary t o obtain complete reaction between t h e olefins a n d t h e bromine solution. Also t h e proportion of benzene present in a 621 ’ C. gas made a t atmospheric pressure is not large. T h e absorption of higher paraffins by t h e fuming sulfuric acid can be avoided in large p a r t b y t h e use of small portions of t h e reagent in a n a p p a r a t u s of t h e t y p e described by G. B. TayIor.3 It, was thought, however, t h a t t h e time required for analyses made in this way would be too great. Another error inherent in t h e method of determining t h e mean molecular weight of’the olefins lies in t h e fact t h a t t h e method for aromatics does not diffiercntiate between benzene, toluene, or xylene. An average molecular weight must be assumed here which cvidently is not absolutely correct. I n t h e calculations all aromatics have been regarded as if t h e y were bcnzcne, since it was believed t h a t this hydrocarbon comprised t h e greatest portion of t h e aromatics present in t h e gas. A further error lies in t h e fact t h a t t h e paraffins were all assumed t o be methane a n d ethane. Higher homologs of this series are without doubt present as has been shown b y Burrell, Seibert, a n d Robertson in their analyses of carbureted water gas a n d coal gas b y t h e method of fractional distillation a t low temperature^.^ A certain proportion of naphthenes or polymethylenes are also no doubt present among t h e products of t h e pyrogenic decomposition of t h e hydrocarbons of kerosene. T o what extent these are affected b y t h e fuming sulfuric acid, a n d t o what extent t h e y are carried through t h e analysis a n d credited to‘ t h e paraffins cannot be s t a t e d . D a t a on t h e exact behavior of t h e cyclobutanes, cyclopentanes, a n d cyclohexanes when t r e a t e d with fuming sulfuric acid have not been found, if, i n fact, such information is a t all available. I n addition t o the errors already mentioned is t h e experimental error i n t h e determination of t h e specific gravity b y t h e effusion method. Check determinations were always made o n t h e time of flow, and it was f o u n d possible t o get agreements t o withinless t h a n 0.j per cent. T h e following analyses are cited t o compare t h e results obtained b y t h e usual procedure with Hempel burette a n d pi‘pettes with those obtained b y t h e use of t h e various modifications discussed above. These 1 R. P. Anderson and J. C. Engelder. THISJOURNAL, 6 (1914), 989-92: R. A. Worstall, J . A . C. S., 2 1 (18991, 245; Orndorff and Young. A m . Chem. J., 1 5 (1893), 249; Burrell and Seibert, “Sampling and Analysis of &line aqd Naturirl Gas,” Bur. of Mines, Bull. 42 (1913), 45-47. 2 “Oil and Gas Levels,” W. Va. Geol. Survey, 1A (1904), 522. a THISJ O U R N A L , 6 (19141, 845. 4 Bureau of Mines, Tech. Page?, 104 (1915); THISJOURNAL, 7 (1915). 17-21.
J u l y , 1916
T H E J O U R N A L O F I N D U S T R I A L A N D E N G I N E E RI NG C H E M I S T R Y
will be designated for t h e sake of brevity as t h e “Standa r d ” method a n d t h e “ C u O ” method, respectively. GAS No. 24 GAS No. 24 GAS No. 25 METHOD: Standard CuO Standard CuO Standard CuO 0.0 0.1 0.1 0.0 0.0 0.1 Carbon dioxide, ....... 0.3 49.3 50.8 50.7 Heavy hydrocarbons... 4 8 . 1 48.2 4 7 . 9 4 9 . 8 0.4 0.5 0.5 0.4 0.5 0.5 0.5 Oxvnen . . . . . . . . . . . . . . 0.1 0.9 0.1 1.1 0.2 0.2 Ca;coon monoxide., , , , 1.2 10.3 9.3 9.2 10.4 Hydrogen.. . . . . . . . . . . 1 1 . 9 1 1 . 9 1 2 . 1 38.4 37.0 37.2 Paraffins. . . . . . . . . . . . . 3 7 . 3 3 7 . 6 3 7 . 7 3 8 . 1
_ _ - _ _ _ _
Total
99.3
98.4
98.5
98.7
97.6
99.7
~
98.7
T H E GAS R A T E
The gas rates for three temperatures are plotted against t h e oil rates in Fig. 8. At 621’ C. t h e gas r a t e increases with t h e oil r a t e u p t o an oil r a t e of 2 0 cc. per minute, b u t t h e introduction of more oil per minute causes no further increase i n t h e gas rate. Apparently with a heated t u b e of t h e dimensions used here only a certain q u a n t i t y of oil can be affected in a given time b y heat a t a temperature of 621’ C. A similar limitation would be expected in a commercial machine operating a t this temperature. At 7 2 3 ’ C. t h e gas r a t e is greater with greater oil r a t e a t all oil rates studied. Judging from t h e shape of t h e curve a n d from t h e analogy of t h e 621’ C. curve i t is apparent t h a t a n increase in oil r a t e above 45 t o 50 cc. per minute would produce no increase in t h e gas rate. At 825’ C. t h e gas r a t e increases with increase in oil r a t e as can be
601
THE EFFECTS OF MOISTURE INTRODUCED INTO THE DIGESTER IN THE COOKING OF SODA PULP By S. D WELLS Received M a y 1, 1916
T h e work of t h e Forest Products Laboratory in studying t h e il;fluences of t h e various cooking conditions in t h e manufacture of soda pulp from aspen indicated t h a t in varying a n y one of t h e four variables, steam pressure, initial concentration, amount of caustic soda used per unit of wood, or duration of cooking a n d maintaining the other conditions cons t a n t , t h e amount of bleaching powder necessary t o bleach t h e pulp t o a standard white was constant for a n y given yield of pulp. Twenty-four semicommercial cooks were made in studying these four variables a n d t h e yields of pulp obtained plotted 30
l
28
l
l
l
l
l
i
OAMOUNT ff CAUSTIC SODA ODURATION OF WOKING *PRESSURE ff COOKING OCONCENTRATIOW OF CAUSTIC SODA
YIELD-TOTAL
CRUDE PULP-PER
CENT
FIG. I
EFFECT OF VARYINGGAS RATE WITH VARIOUSOIL RATES AT THREE TEMPERATURES
seen, a n d at t h e oil rates studied there is no apparent tendency for a r a t e t o be reached beyond which there is no further increase. Obviously, however, such a point would be reached. I n comparing t h e gas r a t e curves it is interesting t o note t h a t a t low oil rates t h e change in temperature from ,621 t o 7 2 3 ’ C. has a much greater effect t h a n t h e change from 7 2 3 t o 8 2 j ’ C. At low oil rates a temperature of 7 2 3 ’ C. is sufficient t o gasify permanently t h e greatest portion of t h e oil. T h e slightly greater production of gas a t 8 2 5 ’ C. is largely due t o t h e decomposition of methane into carbon a n d hydrogen. As t h e oil r a t e increases, a temperature of 7 2 3 ’ C. becomes less a n d less effective for t h e purpose of permanently gasifying t h e oil; 825’ C. is much more effective, as can be seen from t h e increasing divergence between t h e curves. ( T o be concluded in our n e x t issue) DEPARTMENT O F CHEMICALENGINEERING COLUMBIAUNIVERSITY,NEW YORK CITY
against t h e bleach consumption are shown in Fig. I obtained from Bulletin 80 of t h e United States Department of Agriculture. This curve apparently indicates t h a t a n y reduction i n t h e consumption of bleach made b y altering a n y of t h e four variables mentioned cannot be brought about without lowering t h e yield. All t h e cooks made in t h e series, however, were in a digester of only 7 0 gals. capacity a n d t h e condensation during t h e cook was about six times as great as in a commercial sized apparatus of 31/2 cords capacity. A series was, therefore, run where all t h e conditions were maintained constant except condensation a n d this factor was varied b y using a combination of direct steam a n d indirect heating b y means of a jacket in t h e lower portion of t h e digester. T h e results obtained developed t h e remarkable fact t h a t on increasing t h e amount of condensation the yields of pulp were increased and a t t h e same time t h e quality of t h e pulp was slightly improved a n d t h e bleach consumption necessary t o obtain a standard white was decreased. The curves in Fig. I1 show t h e relation of bleach consumption a n d yield t o t h e amount of condensation during t h e cook, using t h e following - conditions:
.................. 90 R. per 1.
Concentration of N a O H . . N a O H per 100 lbs. chips.. . . . . . . . . . . . . . . . . . Maximum steam.pressure.. . . . . . . . . . . . . . . . . Duration a t maximum pressure.. . . . . . . . . . . . Time necessary to reach maximum pressure.. .
25 lbs. 120 lbs. per sq. in 4 hrs. 1 hr.
