N o v . . I913
T H E JOC‘R-VAL O F I N D C S T R I A L A N D E - V G I N E E R I N G C H E M I S T R Y
Improvements of Boiler a n d Other Metal Tubes. 11,981. 1900. A. E. Beck and G. Townsend. Manufacture of Steel Ingots Plated with Copper. 16,993. 1902. S. Vanstone. Improvements in Manufacture of H o t Water Tanks, Etc. 15,383. 1903. D. P. Menzies. Process of Uniting Metals. 18,454. 1903. J. D. Prince. Production of Metallic Protective Depo-its on hletals. 9,836. 1904. A. LPvy. Manufacture of Bimetallic Ingots. 12,000. 1904. H. Harmet. Uniting Iron a n d Steel with other Metals. 17,660. 1904. Davies a n d Clark. Improvement in Manufacture of Compound Metal Ingots, Etc. 8,913. 1906. Monnot. GERMAS PATESTS Method of Manufacture of Conductor Wire with Metallic Covering. 47.950. 1888. Martin a n d Martin?. Method for Coating One Metal with Another. 124,898. January 4, 1899. S. H. Thurston. Slanufacture of Sheet Steel w.ith Copper Covering. 124,387. 1900. Martin. Process for Welding Baser hletals for Purposes of Plating. 137,017. 1902. IVachwitz. Process for Uniting Steel a n d Other hletal Plates with Aluminum, Etc. 15?,04?. 1903. Wachwitz. F R E X C H I’ATEXTS Improvements in the Manufacture of Wire. 168,133. 1885. Martin. Supplement. Perfected Method of Slaking Bimetallic Wires. 168,133. 1888. Bi-Netal Sheets and Plates, Process of IIanufacture of. 206,789. 1890. 3lartin. 213,109. 1891. Perfected Process for Making Bimetallic \Vires. Slartin. Manufacture of Bimetallic Bands, Plates, Sheet Iron a n d Hoops. 216,565. 1891. Martin. BELGI.\X h-ew 171,442.
PATESTS
Process of Manufacturing 1903. Alartin.
Bimetallic
Plates
and
\Vires.
DEPARTMEST OF RESEARCH A N D CHEMICAL ENGINEERISG PITTSBURGH TESTISGLABORATORY
THE CONDENSATION OF GASOLINE F R O M NATURAL GAS’ B y GEORGE4 . BCRRELL.WD
FRANK A l . SEIBERT
I n t h i s p a p e r are given some results of work performed b y t h e Bureau of Mines having t o d o with t h e condensation of gasoline f r o m n a t u r a l gas. CHEMISTRY O F S.1TURAL
GAS
K i t h t h e growth of t h e n a t u r a l gas gasoline i n d u s t r y n a t u r a l gases h a v e been classified i n t o t\vo divisions so called “ w e t ” a n d “ d r y ” gases, depending upon whether or n o t gasoline can be commercially condensed from t h e m . T h e classification is exceedingly loose because n a t u r a l gas mixtures m a y range f r o m those containing only m e t h a n e as t h e combustible cons t i t u e n t ( a gas difficult t o liquefy) t o those i n which t h e hydrocarbon vapors predominate a n d which liquefy easily. Bet\%-eent h e t w o extremes t h e r e a r e n a t u r a l gases containing t h e different constituents, m e t h a n e , e t h a n e , propane, b u t a n e s , pentanes, etc., in m a n y different combinations. Some of these m a y not contain enough of t h e desirable gasoline constituents for commercial purposes, others m a y . N a t u r a l gases n o t f o u n d i n t i m a t e l y associated with oil a r e t h e so-called “ d r y ” gases. Those f o u n d i n t h e s a m e s t r a t a with oil a n d in i n t i m a t e contact with t h e s a m e are those f r o m which ,gasoline is obtained i n t h e n a t u r a l gas gasoline i n d u s t r y . T h e Bureau of Mines finds as t h e result of m a n y analyses t h a t n a t u r a l gases 1 Paper presented a t the 48th meeting of the American Chemical Society, Rochester, September 8-1 ? , 1913. Published by permission of t h e Director of the Bureau of 3Iines.
895
a r e mixtures i n which hydrocarbons of t h e paraffin series predominate a n d t h a t small quantities of nitrogen, carbon dioxide a n d water vapor are present. Hydrogen sulfide is sometimes p r e s e n t ; perhaps o t h e r sulfur compounds too. F. C. Phillips f o u n d n a t u r a l gases of Western Pennsylvania, which h e worked with, t o c o n t a i n paraffin hydrocarbons, carbon dioxide a n d nitrogen. Other investigators invariably report a t least small proportions of carbon monoxide, hydrogen a n d ethylene. Experimental errors i n t h e work easily accounts for these errors. T h e a u t h o r s of t h i s p a p e r believe t h e work of S. A. F o r d a s showing very large percentages of hydrogen t o be in error. His analyses h a v e been q u o t e d m a n y times i n different t e x t books. T h e y were m a d e in 1885. T h e a u t h o r s of t h i s p a p e r i n looking over t h e analyses m a d e b y t h e m of t h i r t y n a t u r a l gas samples collected from different p a r t s of t h e c o u n t r y find t h e heating value ranging from 6 8 j B. t. u. t o I j i 7 B. t. u. per cubic foot a t 60’ F . a n d 760 m m . pressure. These analyses will be incorporat e d n-ith m a n y others i n a government publication. These gases range from marsh gas issuing from t h e marsh beds, a n d containing only inethane as t h e combustible gas t o casing h e a d gases t h a t are used for lighting a n d heating towns. Only t w o of t h e gases, those of t h e highest heating value, are probably a d a p t e d for gasoline condensation. One sample contained ( a s shown b y combustion analysis) i n addition t o m e t h a n e , carbon dioxide a n d nitrogen, 7 5.16 per cent of e t h a n e . T h e n a t u r a l gas of P i t t s b u r g h has a gross heating value of a b o u t 1 1 7 7 B. t . u. per cubic foot a t o o C. a n d ;60 m m . pressure. S I G S I F I C A S C E 0 F 0 R D I S A R Y A S A L Y T I C A L R E S L-L T S
I n t h e analysis of n a t u r a l gases b y t h e slow combustion m e t h o d , t h e d a t a obtained a d m i t of t h e calculation of only t w o of t h e chief constituents. T h e mixture, however, m a y contain all of t h e gaseous paraffins a n d considerable quantities of t h e vapors of t h e liquid hydrocarbons. When t h e lower members of t h e paraffin hydrocarbons predominate, t h e results obtained are more accurate t h a n when t h e higher members predominate. N a t u r a l gases from v h i c h gasoline c a n be extracted contain appreciable q u a n t i ties of t h e liquid hydrocarbon vapors. I n t h e analyses of these mixtures t h e ordinary slow combustion analysis will give only approximate results for several reasons. First-The gas mixture often contains more t h a n tm-0 combustible constituents. Secoizd-Some of t h e gases a n d vapors deviate considerably f r o m t h e gas laws a n d their t r u e molecular volumes’ a r e unknown. Third-So small a n a m o u n t of t h e mixture must be used i n some cases t h a t experimental errors a r e greatly magnified i n calculating t o a percentage basis. Typical analyses of t w o different n a t u r a l gases follow which c o n t a i n small a m o u n t s of m e t h a n e a n d larger a m o u n t s of e t h a n e , propane a n d b u t a n e v-ith t h e vapors of t h e liquid hydrocarbons p e n t a n e , hexane, etc. These analyses serve t o show how approximate a com1 .4 government publication b y the authors which c o ~ e r sthis question is in press.
T H E J O C R i V A L O F I N D C S T R I d L - 4 Y D ENGI,VEERI,VG
896
bustion analysis m a y be even when t h e analysis is carefully performed. I n t h e analysis of gases of this t y p e t h e explosion m e t h o d is entirely o u t of t h e question. T h e analyses were m a d e b y t h e method of slow combustion. Duplicate analyses were made of each sample. SAMPLES o
1
I
I1
cc. Volume of sample taken'. . . . . . . . . . . 20,oo Oxygen a d d e d . . . . . . . . . . . . . . . . 9 5 . 7 0 Total v o l u m e . . . . . . . . . . . . . . . . . . . . 115 7 0 Volume after burning. , . . , . , , , . , , , 64.10 51 . 6 0 Contraction due to burning.. . . . . . . 22.10 Volume after COz absorption. . , , , . , 42.00 Carbon dioxide produced by burning. RESULTSOF ASALYSES Ethane. . . . . . . . . . . . . . . . . . . . . . . . . . . Propane.. . . . . . . . . . . . . . . . . . . . . . . . .
cc. 19.95 95 30 115.25 64.00 51.25 22.60 41.40
PER CEST 96.00 6.00
-
Total paraffins.. . . . . . . . . . . . . . . . . 102.00
98.75 3.33
102.08
SAMPLENo. 2
Volume of sample t a k e n . . . . . . . . . . . . Oxygen added . . . . . . . . . . . . . . . . . . . . Total v o l u m e . . . . . . . . . . . . . . . . . . . . . Volume after burning. . . . . . . . . . . . . . Contraction. . . . . . . . . . . . . . . . . . . . . . Volume after COz absorption, , . . , , , Carbon dioxide produced b y burning.
RESULTSOF ANALYSES Ethane., Propane. Total paraffins.. .
-
........ ........
...............
I11
IV
cc. 20.35 96.15 116.50 60.10 56.40 10.40 49.i o
cc. 23.50 126.i5 150.25 85.30 64.95 28.20 S i . 10
PER CENT 65.85 3i.50
66.80 36.50
103.35
103.30
- _ _
T h e foregoing analyses show how a small difference i n t h e contraction d u e t o combustion a n d t h e carbon dioxide produced will, when calculated t o t h e same basis, affect t h e distribution of t h e paraffins a n d also t h e t o t a l paraffin content. T h e fact t h a t t h e gases t o t a l over I O O per cent is because t h e correct molecular volumes of all t h e gases present i n t h e mixtures are not known. F o r example, i n t h e case of analyses I a n d I 1 (duplicate analyses) t h e contraction i n I is j1.60 cc. from 20.00 cc. of t h e original sample while t h e contraction i n I 1 is j 1 . 2 j cc. This l a t t e r result, when calculated t o 20.00 cc. of sample, gives a difference of 0 . 2 2 cc. from t h e first, which is t h e experimental error. T h e carbon dioxide produced in I from 2 0 . 0 0 cc. of sample is 42.00 while t h a t produced from I 1 when calculated t o 2 0 . 0 0 cc. sample is 4 1 . j o cc. or a difference of 0 . j cc.? t h e experimental error. T h e combined difference in t h e contractions a n d carbon dioxide change t h e paraffin distribution b y 9S.7 j- 96.00 or 2 . 7 j per cent i n t h e case of e t h a n e a n d 6.00- 3 . 3 3 or 2.67 in t h e case of propane. T h e t o t a l paraffin hydrocarbon content is changed only by 102.0s1 0 2 . 0 0 or 0.08 per cent. I n a like manner in t h e case of analyses I11 a n d I T (duplicate analyses) t h e contraction produced in I11 b y t h e combustion is j6.40 cc. with 2 0 . 3 j of sample Tyhile t h e contraction produced in IV calculated t o 2 0 . 3 j cc. of sample is j6.2 j cc. or a difference of j6.40 cc. - j6.2j cc. or 0.1j cc., t h e experimental error.
CHEMISTRY
T h e carbon dioxide f r o m
20.3j
Vol. j, S O .1 1
cc. of sample is
59.70 cc. i n I11 while t h e carbon dioxide in I V is 49.44
cc. when calculated t o 20.3 j cc. of sample. This is a difference of 0.26 cc., t h e experimental error. Here t h e combined difference of t h e contractions a n d t h e carbon dioxide change t h e paraffin distribution b y 66.80- 6 j.8 j or 0.9 j per cent i n t h e case of ethane a n d 37. jo- 36. j o or 1.00 per cent in t h e case of propane. T h e t o t a l paraffin content is changed only b y 103.35103.30 or o . o j per cent. Although combustion analysis shows only approximately t h e q u a n t i t y of paraffin hydrocarbons present, t h e t o t a l paraffin hydrocarbons are correct or nearly correct. T h e same can be said of t h e heating value a n d specific gravity a s calculated from t h e analyses. T h e ascertaining of t h e different hydrocarbons t h a t m a y be found i n n a t u r a l gases h a s long been a s t u m b ling block t o gas analysts. T h e ordinary eudiometer analysis offers nothing in t h e way of a complete separation. T h e t o t a l paraffin hydrocarbon content with only a n approximation of t h e individual paraffin has been t h e only e n d a t t a i n e d . T h e a u t h o r s i n working on t h e problem succeeded i n making a separation of a n a t u r a l gas i n t o i t s individual paraffin hydrocarbons b y means of fractional distillation a t low t e m p e r a t u r e s . N a t u r a l gas was first liquefied b y means of liquid air a n d t h e n b y means of a Topler p u m p , t h e methane was removed. T h e vapor pressure of liquid e t h a n e (boiling point -93 O C.) is so small a t t h e t e m p e r a t u r e of liquid air (-190' C.) t h a t t w o fractionations sufficed t o remove t h e methane, which was measured a n d analyzed. T h e residual gas was t h e n subjected t o a t e m p e r a t u r e of -130' C. a n d as much gas as could be removed was withdrawn with t h e p u m p . T h e mixture withdrawn proved t o be e t h a n e a n d propane. A t -130' C. all t h e e t h a n e (boiling point -93' C.) a n d p a r t of t h e C.) is removed. This propane (boiling point -45' fraction was measured a n d analyzed. T h e residual liquid was t h e n allowed t o volatilize a n d was f o u n d t o be propane. T h e proportions were t h e n found b y simple calculations. B u t a n e was n o t f o u n d within t h e experimental error of t h e manipulation which was perhaps 0.2 or 0.3 per cent. Traces of b u t a n e exist i n t h e gas, however, a!so of pentane a n d hexane. T h e complete analysis including t h e q u a n t i t y of each paraffin hydrocarbon found b y t h e above method follows. F o r comparison t h e ordinary eudiometric analysis of t h e n a t u r a l gas is given. T h e n a t u r a l gas is t h a t used in Pittsburgh. By liqueBy faction and eudiometric fractionation analysis Per cent Per cent CHI . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86.8 i9.2 C?H 5.i 19.6 ......................... CaHr., . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 ... SI.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 1.2
__
~
Total . . . . . . . . . . . . . . . . . . . . . . . . .
100.0
100.0
The carbon dioxide in t h e Pittsburgh n a t u r a l gas a m o u n t s t o a trace (0.03 per c e n t ) . T h e gas cannot be used f o r t h e commercial production of gasoline although i t contains sufficient of t h e hydrocarbon 7;apors t o produce some condensate (drip) i n t h e pipe
NOV.,
1913
T H E J O r R . V d L O F I J D C S T R I . - l L dAVD EAVGISEERIAVGC H E M I S T R Y
lines. This is because of t h e immense volume of gas passing. T h e gas comes f r o m W. Va. and is typical in composition of gases f r o m t h a t field t h a t are supplying many towns. T h e natural gas from t h e Hogshooter Pool of Oklahoma, some of which goes t o Kansas City, contains only methane ( 9 j . 4 per cent) as t h e combustible constituent. T h e rest is nitrogen and carbon dioxide (dry basis). T h e Bureau has t h e composition of t h e natural gases t h a t are supplying many towns' Further 'vork is being done b y t h e authors on t h e fractionation of natural gases. More difficulty is experienced in making a separation when Of the gaseous paraffins and vapors Of the liquid O n e s are present. OCCCRRENCE
O F GASOLINE I S NATCRAL
GAS
T h e yield of gasoline from natural gas is determined largely b y t h e q u a n t i t y of t h e liquid paraffin vapors in t h e permanent gases. Temperature and pressure conditions in t h e well, gasoline content of t h e oil, and intimateness of contact between oil a n d gas, all affect t h e yield, Such rapid expansion of a gas f r o m a casing head may occur a s t o cause a heavy condensation of vapors a t t h e casing head. hIethane (critical temperature - 9 5 . j o c.. critical pressure , 3 j pounds per square inch) is always in a well in the gaseous condition. Ethane (critical
,
temperature 3 j " C . , critical pressure 6 6 4 pounds per square inch) exists in some wells as a gas, in others, probably as a liquid. propane and the butane are easily liquefied than ethane. In gases used even for gasoline production they are present as gases. reduced pressures are usually applied In such to the m-ells, ~h~ gasoline vapors are mixed m.ith these permanent gases in t h e Same manner that moisture exists with air. I n gasoline plant operation, t h e pressure applied to condense the vapors must, of depend on the partial pressures of the vapors in the natural gas mixture. ~f butane (boiling point C.1 f o r instance constitutes t w e n t y per cent of t h e mixture. there wou1d be needed a total pressure of seventy-fi1-e pounds per to have I pounds on the butane square inch in condensation of t h e vapor to begin. vapor. and For this reason 011e gas may produce condensate lvith ; pounds, \\,bile another gas will need 2 o o to 3 o o the standal-d type of cooling a n d pounds, arrangement as used t o - d a y , methane and ethane are not liquefied b u t propane a n d butane a r e , addition the final mixture as recei\-ed at t h e collecting t a n k , will contain condensed gasoline T-apors, i. r , , pentanes. hexanes, e t ? , There \vi11 also be f o u n d a portion of t h e gases methane and ethane clissolx-ecl i n 11a7.e the liquicls, other Tl.ords se7-eral cllang,es c ) has ~ t ~ o do Tvith t h e conclensation of taken p l a c e , another lvith t h e licluefaction of g a s another J7-ith t h e solubility of t h e permanent gases in t h e licjuid prodllced. ~h~ three c h a n g e s are so intimately connected \?.ith each other t h a t one factor cannot be disturbed without affecting the others. For instance such a temperature a n d pressure could be employed as t o increase t h e condensation of t h e desirable consti:uents (the gasoline
pressure
897
vapors) b u t with increasing pressure a n d lowered temperature more of t h e undesirable gaseous constituents would liquefy. These when exposed t o atmospheric conditions of temperature and pressure would immediately volatilize. carrying with t h e m some of t h e gasoline constituents. At increasing pressures more ethane and methane would be dissolved. With release of pressure t h e y t o o would escape. T E S T I N G S A T U R A L GAS F O R G A S O L I X E V A P O R S
Before plant installations are made for t h e purpose of extracting gasoline from natural gas an investigation of the seyeral factors should be made, These include ( I ) quality of gas, ( 2 ) quantity of t h e gas, (3) disposal of product. QCALITY O F GAS
Laboratory methods in use at the present time consist chiefly of combustion tests, solubility tests a n d specific-gravity tests. T h e combustion analysis gives Only a rough approximation. The specificgravity is much used. gases may range in specific gravity f r o m about 0 . j 6 to I . j o * t o air. Some gases are used for condensing gasoline t h a t have as low a specific gravity as 0.80. All gases of this -specific gravity are n o t adapted, ho~ex7er. If t h e carbon dioxide or nitrogen content of a n a t u r a l gas is high and not known, the 'pecific gravity test may be misleading. Alcohol. claroline oil, olive oil. kerosene oil, etc., all have been used for determining t h e solubility of gases. The higher members Of t h e paraffin series are more soluble in these solvents t h a n are t h e lower members. T h e authors have used tests t h a t consist in shaking IOO cc. of t h e natural gas in j o cc. of alcohol or 3 j cc. of claroline oil, a n d noting t h e loss in gas l'olume. T h e test is arbitrary. Under these conditions i t was found t h a t natural gases soluble t o t h e extent of from 30 t o 86 per cent of their volume were used for condensing gasoline. In all these tests inconsistencies haVe been noted. so that especially a s regards t h e m i n i m u m specific-gralrity tests a n d solubility numbers herein given one would not feel sure about t h e feasibility of plant installation. S a t u r a l gases differ much in composition. T h e socalled wet gases, for instance. might contain a v e r y large proportion of methane. with b u t little ethane. propane and butane. but enough of the gasoline T-apors t o Karrant plant installation. -Inother gas n-ith t h e Same specific gral-ity might contain a comparntively small proportion of methane a n d ethane. a large pron o t enough Of the portion of b u t a n e a n d propane gasoline constituents t o ITarrant plant installation. The safest recourse is t o be h a d t o s o m e t y p e of laboratory compressor or better still t o a portahle outfit consisting of gas meter. g a s engine, compressor, cooling coils and receii-er. Such a n outfit r a n lie hauled from well t o well on a wagon. Tests conducted b y such ?. method must also h e i n t h e h a n d s Of competent persons. Q C A S T I T I O F THE
G-AS
l l a n y plants are in operation norking on as litt!e as 1 z j . 0 0 0 cubic feet of gas per 24 hours. Some ::re
T H E J O U R N A L OF INDC’STRIAL A N D E N G I N E E R I S G C H E M I S T R Y
8 98
working on as little as 40,000 cubic feet. These latter are largely experimental. A fair sized plant t o handle 12j,000 cubic feet costs about $10,000. There are probably 2 0 0 plants in t h e United States making gasoline from natural gas. VALUE O F RESIDUAL
GASES
Residual gases left after plant operation are of high heating value, unless contaminated with air. Air may leak into t h e pipes due t o reduced pressure on the pipe lines (as much as 2 j inches of mercury). I n one case t h e authors found t h a t a residual gas h a d a heating value almost twice as high as t h e heating value of t h e Pittsburgh natural gas. According t o t h e facts already presented t h e residual gas is bound t o be a
v01. j, KO. I I
Table I gives t h e results of t h e analysis of t h e natural gas used b y a plant near Follansbee, K. T’a. T h e analysis, specific gravity and claroline absorption show this t o be a rich gas. I t will be seen t h a t b u t little difference exists between t h e composition of the crude gas before a n d after it has been compressed t o 5 0 pounds per square inch. I t is only after compression t o 2 j 0 pounds per square inch a n d cooling, t h a t t h e composition of t h e gas mixture changes appreciably. T h e high heating value of the residual gas is apparent. Table I1 shows t h e results obtained from a small plant near RIcDonald, P a . This is not a very “wet” gas. I t s claroline absorption number is rather low. It is probably near t h e lower limit of a gas adapted for t h e condensation of gasoline. The composition
TABLEI
2281 2284 2286
Natural gas from Follansbee, IX‘. \’a ... . Residual gas after 50 Ibs. compression. Product has beenremoved.. . . , . , , . . . . Residual gas a f t e r 250 lbs. compression. Product h a s b e e n r e m o v e d . . . . . . . , . . . .
..
2339
1.41
83.6
,,
2295
1.38
82.0
.,.,
1913
1.15
63.6
.. . .
. ,..
21.4
78.2
....
0.4
(a)
100.0
...
26.6
72.8
.,
,,
0.6
(a)
100.0
....
-- . 3
22.0
....
0.7
(a)
100.0 T h e gasoline is
,
ii
( a ) Trace of Cor present.
Gas is from.75 producing wells and is withdrawn under a reduced pressure of 20 inches of mercury. blended with low-grade refinery naphtha and then marketed.
rich gas, because t h e methane a n d t h e ethane are not liquefied, and only a portion of t h e propane a n d butane. Neither are all t h e gasoline vapors condensed. Air m a y appreciably lower t h e value of the gas, horvever. Some residual gases contain 40 t o j o per cent of air. D E P L E T I O N O F T H E R E S I D U A L GAS
A S REGARDS
QUANTITY
T o give exact figures for t h e quantity of gas a n d vapor t h a t disappear from t h e raw gas in plant operations is impossible. If four gallons of condensate are produced from each 1,000cubic feet of natural gas. about 140 cubic feet of gas per 1000may disappear.
of t h e gas does not change t o a very marked degree after it has been compressed t o 80 pounds per square inch. NOTE The foregoing is abstracted from a bulletin covering in greater detail t h e condensation of gasoline from natural gas. This bulletin is in press. I t treats of the waste of natural gas, status of t h e natural gas gasoline industry, future of it, utilization of cazing head gas, occurrence of gas and oil, use of gas from flow tanks, value of plant equipment, chemistry of natural gas, occurrence of gasoline in casing head gas, gasoline
TABLEI1
i 2
