February, 1934
INDUSTRIAL AND ENGINEERING
An accurate and practical method of designating the rank of coal, together with its heating value and impurities as produced, has been suggested. This is in effect a condensed analysis with the extraneous figures trimmed away. One important regional sales organization has just completed the classification of the several hundred mines in its group by this method. Similar work is in progress for another coal classification group. The Committee on Use Classification is now correlating the various specifications of coals for particular uses, with the classification recommended by the Committee on Scientific Classification. When a n official system of coal classification is a t last adopted, the years of hard work will not be visible in the reasonably simple and rather familiar system that is proposed. However, each boundary line or other detail will be based on exact knowledge and fact to a degree that has never before been possible. (1)
LITERATURE CITED Ashley, G. H., Pa. Topographical and Geol. Survey, Bull. 89 (1926).
CHEMISTRY
143
Bode, H., Proc. 3rd Intern. Conf. Bituminous Coal, 2, 878 (1931). Campbell, M. R., U. S. Geol. Survey, Professional Paper 100 (1917). Dowling, D. B., Can. Geol. Survey, Mem. 59 (1915). Fieldner, A. C., Proc. 2nd Intern. Conf. Bituminous Coal, 1, 632 (1928).
Frazer, P., 2nd Geol. Survey of Pa., R e p t . MM, 144 (1879). Gilmore, R. E., Trans. Am. Inst. Mining M e t . Engrs., Coal Diu., 1930, 529.
Gruner, E., and Bousquet, H., “Atlas general des houillAres,” II* Comite des Houillbes de France, Paris, 1911. Johnson, W. R., Senate Document 386, 28th Congress, 1st
Session, 1844.
Moore, E. S., “Coal,” 1st ed., p. 105, Wiley, 1922. Parr, S. W., J. IND. ENG.CHEM.,14, 919 (1922). Ralston, 0. C., Bur. Mines, Tech. Paper 93 (1915). Rose, H. J., Proc. Srd Intern. Conf. Bituminous Coal, 2, 838 (1931).
Rose, H. J., Trans. Am. Inst. Xining Met. E ~ Q T s74, . , 600 (1926); Fuel, 5 , 562 (1926), 6, 41, 84 (1927). Rose, H. J., Trans. Am. Inst. Mining M e t . Engrs., Coal Div., 1930, 541.
Seyler, C. A , , Fuel, 3, 15, 41, 79 (1924). Stansfield, E., Proc. Symposium Fuel Coal, McGill Univ., 1931,
35-72. RECEIVED September 19, 1933.
Twenty-Five Years of Natural and Refinery Gases GEORGEA. BURRELL, Burrell-Mase Engineering Company, Pittsburgh, Pa.
T
WESTY-FIVE years ago about 500 billioii cubic feet of natural gas were consumed per year. This compares with a peak production in 1930 of almost 2000 billion cubic feet, and a value of $415,000,000. Manufactured gas €or that same year amounted to about 400 billion cubic feet of a value of $450,000,000. Half of the natural gas is used at the present time for domestic and industrial use, and the other half in the oil fields and for making carbon black. Satural gas customers now number about 7 million. Ohio, New York, and Pennsylvania, in the order named, are the largest users of domestic and commercial gas-i. e., aside from oil field and carbon black uses. Texas produces the most gas, and the largest reserve in that state (the Amarillo) will last for 60 years, it is estimated, a t its present rate of production. Of particular interest has been the discovery, in recent years, of natural gas from deep strata in northern Pennsylvania and New York fields. The most active fields are in Potter and Tioga Counties, Pa. The known reserve per acre in the Tioga field is something of the order of 2 to 5 billion cubic feet, and that in the Potter field probably somewhat more. Rock pressures are as high as 2250 pounds per square inch, and wells are 4000 to 5000 feet deep. Thus it is seen that the natural gas industry is not yet a declining one, although this prediction was freely made 25 years ago. Wells now can be drilled to a depth of 7000 feet or more, and the gas is transported a distance of 1000 miles. I n 1930 there were constructed 21,000 miles of trunk lines a t a cost of $450,000,000. The total trunk line mileage is 60,000, and there are 600,000 horsepower of gas engines of 300 horsepower and over, for compressing the gas in these lines. There are now 56,000 gas wells in the United States. The amount of natural gas consumed per year is equal in heating value to about 70 million tons of bituminous coal. The peak production of coal was about 500 million tons
per year. Natural gas to the extent of 196 million cubic feet were used in 1931 to make 281,000,000 pounds of carbon black. Of this, about 100,000,000 pounds were exported. Its main use is for auto tire manufacture, although considerable quantities are utilized in pigments, inks, paints, and the like. About 1.5 billion gallons of natural gasoline are extracted from 1.5 trillion cubic feet of gas each year. This compares with almost no natural gasoline 25 years ago. Of the total amount of energy expended in the United States in 1929, aside from man power, bituminous coal furnished 50 per cent, petroleum 21 per cent, natural gas 7 per cent, and water power, anthracite, wood, and other sources, the remainder. CHEMISTRY OF NATURALGAS
F. W. Phillips, in 1900, was the first to show the composition of natural gas and characterize i t as being composed of the paraffin hydrocarbons, with no carbon monoxide, hydrogen, or unsaturates. His work was a great classical analytical research and a marvel of painstaking care and exactitude. I n 1915 the present author and his Bureau of Mines colleagues made the first fractionation analysis of natural gas, showing the exact amount of the different paraffins present. Analytical gas fractionation apparatus has reached its greatest development in the hands of W. J. Podbielnisk. With his apparatus all of the constituents up to heptane can be fractionated out of a gas mixture. Thus the field of gas analysis has been enormously extended. A diagram of a gas fractionating apparatus is shown in the first illustration. B is the fractionating column, D the reflux condenser containing gasoline into which liquid air is blown from E . H and G are the pressure gages, and J and I the vessels for measuring the fractions. The natural gas is introduced into the vessel at M ,
144
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 26, No. 2
liquefied with liquid air, and the various fractions, methane, ethane, etc., are removed by means of a vacuum pump at appropriate reflux temperatures.
widely used in pipe joints, but oxy-acetylene welding and electric arc welding are in wide use. Some soils or some spots in soils corrode pipe rapidly. Usually methane predominates in natural gas with small To guard against this, surveys can be made of the electrical quantities of the higher paraffins, but in some rich oil well resistivity (acidity) of the soil so that pipe can be well progases the higher paraffis may predominate. Carbon di- tected a t these places. Usually the pipe is protected by tar oxide or nitrogen is usually present in small quantities but or asphalt and wrapped with felt. Lines of the Kew Orleans in rare cases may be present to the exclusion of practically high-pressure natural gas system are coated with two layers of 15-pound per square inch asbestos felt, spirally wound on all other compounds. the pipe by machine after dipping in hot asphalt. Previous to coating, the pipe is machine-cleaned and painted with asphalt primer. i17elded joints are covered with three .-. layers of felt and asphalt, the third layer overlapping the fi seams. el Electrolysis of the pipe is minimized by bonding the mains through one or more metallic connections, such as a copper cable, to the proper return circuits of an electric railway i: system. Much gas is still wasted through leakage. According to an extensive survey made by the U. S. Bureau of Mines, the gas that escapes from holes of 1/61 to l/4 inch in size, at a ? pressure of 300 pounds per square inch, amounts to $173.00 to $41,630.00 per year; the leakage rate from screwed lines that are in the best condition varying from 250,000 to 400,000 h cubic feet per year per mile of 3-inch pipe, 100,000 to 300,000 cubic feet for rubber coupled lines, and 10,000 to 166,000 cubic feet for welded lines. L.4BORATORY FRACTION.4TING APPARATUS Katural gas under enough well pressure can be piped long distances without installing compressors, but, if the well Helium may be found to the extent of several per cent in pressure is too low, or the distances too long, compressors rare cases, but is usually present only in traces. The Petrolia have to be employed. These are spaced a t such distances, gas, upon which the Bureau of Mines founded its helium in keeping with the size of the gas line and its length, as to work in 1917, contained 0.90 per cent of helium. The author provide the most economical installations. Stations are located this supply for the Government, although Cady and located on a water supply and are accessible to railroad or McFarland in 1907 were the first to show the presence of truck transportation so that construction and repairs will helium in natural gas. They worked with gas from the old not contain high haulage costs. On larger gas lines comSedalia field in Kansas. The Government has a large reserve pressors of 1000 to 1500 horsepower are employed. Direct supply of helium natural gas in the Panhandle district of driven types long ago superseded the old belt-driven models. Texas where their helium extraction plant is now located. Most natural gas varies in heating from 1000 to 1150 B. t. u. per cubic foot, although it may be much lower or a higher than this. Nitrogen and carbon dioxide are the prin?? cipal diluents. .L,
I
p
s
s:$2
TRANSMISSION OF KATURAL GAS
$\ a9
There have, of course, been great advances in the transmission of natural gas. Cast, wrought, and lap- and buttwelded iron, and seamless pipe represent the advances since the beginning of the industry; screw couplings, Dresser and similar couplings, and welded joints have followed in turn. Electric welded and seamless pipe have nearly supplanted other types of construction. Pressures which pipe will withstand have risen to meet any practical demand. Mill scale on pipe, inside and out, has practically disappeared so that abrasion of valves and regulators has been reduced and protection coatings can be applied more satisfactorily. Long welded sections are now hauled into place with tractors into trenches dug with fastmoving trenching machines. Internal corrosion of high-pressure, long-distance pipe lines has received attention in recent years. Oxygen, hydrogen sulfide, and water are the active agents. Such minute quantities of hydrogen sulfide are apparently involved that it is almost impossible to remove them. Oxygen enters mains, as air, from "vacuum" oil and gas wells. In those cases where internal corrosion is a serious factor, the method of attack is to remove the water by refrigeration methods. Rubber gasket couplings of special composition are still
%C
;:
POWER REQUIRED TO COMPRESS NATURAL GAS
I n computing power requirements for compressing natural gas, the following formula, derived by Thomas Weymouth, has long been used : I. H.P. =
where
r
4.44 - 106.6 log T 0.97 - 0.03067
= ratio of absolute discharge pressure to absolute
suction pressure
P. M. Biddison gives the indicated horsepower as:
I. H. P.
=
TO"'
284.75 o.97
- o.03r 0.98 -
The Biddison formula will give slightly higher values for the I. H. P. than the Weymouth. This is apparently due to the fact that the Biddison formula was obtained from data on large sized compressors of the order of 1000 to 1500 horsepower, where the compression more nearly approaches the true adiabatic, and consequently a greater amount of energy is required.
February, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
The earlier compressor stations were equipped with steamdriven compressors. Other types of prime movers had not been developed and steam was, therefore, the only reliable source of power. Gas was burned under boilers to generate steam. The compressors were usually connected to the heat end of the steam cylinder and were driven by the steam cylinder piston rods which extended into the compressor cylinders. But steam plants use 30 to 60 cubic feet of gas of 1000 B. t. u. per horsepower hour, while modern fourcycle gas engines use 10 or less cubic feet. Therefore, the gas engine has largely superseded the steam engine. Biddison estimates the cost of large compressor stations, under conditions he had in mind, a t about S l l 5 per installed horsepower. This included real estate, residences, railway siding, and water supply. His operating cost amounts to 610,000 per year plus $7.75 per horsepower. This includes labor, supplies, gas at 7 cents per thousand cubic feet (for 60 per cent load factor), and maintenance, but excludes taxes and fixed charges.
COUBUSTIOS OF NATU~ZAL GAS The efficient combustion of natural gas revolvec;, of course, around the efficiency of combustion appliances. Furnaces and their auxiliaries that are efficient for other fuels are also efficient for natural gas, although combustion is always a simpler process for gaseous fuels than for solid ones (except possibly pulverized coal). Radiant sections, water-cooled walls and floors, preheaters, economizers, high-pressure boiler drums, tubes, refractories, and the like have all undergone an amazing advance in 25 years. I n general, household kitchen appliances extract heat from natural gas with an efficiency of 20 to 35 per cent, hot water heaters 40 to 60 per cent, and steam boilers up to 85 per cent, or better. It is interesting that in the millions of kitchens using gaseous fuels, utilization of the fuel should be so poorly accomplished. Of course, stoves are fine examples of the designers' art, ovens are insulated, temperature is controlled, and burners are more efficient than ever, but kitchen pots and pans have shown little improvement over 25 years ago in their ability to extract heat from a burner flame, even though the pots and kettles do not get as black as was once the case. So-called radiant room-heating stoves found their way into the market during the past 25 years. I n these stoves, of course, conduction, convection, and radiation of heat all come into play. The stove itself is heated by conduction, air convection currents carry the heat throughout the room, and energy is also projected by radiation. The advantage of the latter is that radiant energy is transmitted in straight lines so that from an open-front radiant room heater, for example, the radiant heat is projected horizontally, whereas hot convection currents largely ascend to the top of a room. Another advantage of a radiant heater is that the white-hot radiant grids present a pleasing appearance to the eye. Of course, the radiant grids first have to be heated hy convection and they can transmit no more heat than they receive. I n other words, transmission of heat by radiation, per se, is not a particularly efficient method of transmitting heat, but for certain purposes, as in a radiant stove heater, it possesses the advantages stated. Efficiently used in furnaces, the latter can be made smaller. GAS As new sources of natural gas were discovered during the past 25 years, consumption of the gas jumped from 500 billion to 2000 billion cubic feet per year. Lines were extended to a maximum of 1000 miles. Thus many communities that once used manufactured gas changed to natural gas, or augmented their supply with the latter. SUBSTITUTION O F NATURAL FOR MAICUF.4CTURED
145
Manufactured gas differs from natural in that the heating value of the latter is about twice as high, more air is required for complete combustion, the specific gravity is usually higher, the flame is softer, the rate of flame propagation slower, and the flame temperature about 100" F. lower. These differences hare to be considered in the adjustment of burners and pressure regulators; but, where the tTvo gases are efficiently utilized, the usefulness of the gases to the consumer has been found to be in direct ratio to their heating values. Since natural gas is cheaper to produce, domestic
FLOWDIAGRMOF T Y P I C ~HOT L -4CTIFIC4TIOY PLAUT
consumers frequently enough pay 65 cents for 1000 cubic feet of natural gas of 1050 B. t. u. heating value, where before they paid perhaps $1.50 or more for manufactured gas of 540 B. t. u. value. As regards fuel oil and natural gas, a rough but useful comparison is that fuel oil at $1.00 per barrel is equivalent to natural gas at $0.16 per 1000 cubic feet. PcRIFIC.4TION
O F NATURAL G A S
The amount of natural gas that is purified or treated in any way to remove objectionable compounds is negligible compared to the untreated quantity. Coal is mined, frequently purified by washing, coked, transported, and gasified, and the gases are purified before the latter are suitable for use to the consumer. Natural gas is only mined and transported. It is true that there is more financial hazard in locating gas deposits, but even so, natural gas enjoys a great advantage over manufactured because of the comparative simplicity of methods of handling it. However, some natural gas has to be treated to remove hydrogen sulfide, and water in the gas is troublesome because it causes corrosion and deposits in pipe lines, and reduces the carrying capacity of the lines a t some point where conditions of temperature and pressure are suitable for its deposition. I n a few instances much of the water is removed by refrigerating the gas. Lime was one of the first agencies used to purify gas of hydrogen sulfide: Ca(OH)?
+ 2HnS = Cs(HS)z + 2Hz0
The author and his associates have built several limescrubbing plants in recent years to remove hydrogen sulfide from refinery gas, but lime has its disadvantages. The evil-smelling end product is difficult to dispose of in quantity. The iron oxide process is generally used in the manufactured gas industry, Fen03 3H2S = FepS3 3H20
+
+
but in recent years other processes, such as the Seaboard, the Girdler, and the Koppers hot activation, have been used. They are simpler and less expensive to install and occupy less space than the iron oxide process. I n these latter processes a weak base is used, such as sodium carbonate, diethanolamine, and sodium phenoxide,
INDUSTRIAL AND ENGINEERING CHEMISTRY
146
Vol. 26. No. 2
gas will absorb moisture and oil from the jute joints of the pipe system and cause them to dry a n d l e a k . This is done by inj e c t i n g s t e a m a n d oil vapor. Tetralin is frequently used. Costs of oil fogging are of the order of 15 cents per ~ , ~ O , O o O cubic feet of gas, and of water s a t u r a t i o n (rehydration) about 60 cents per 1,000,000 cubic feet.
that the base can be reclaimed. This is also true of iron oxide but not of a strong base like lime. The acid sulfides of the weak bases have an appreciable, but not too high vapor pressure, which enables one to sweep the hydrogen sulfide out of solution with air or steam, and thus makes the base available for use over and over again. I n the Girdler process the rea c t i o n s are p r o b a b l y of the following order: SO
SATURAL GASOLINE PLANTS
Satural gasoline plants of the compression type were first built to extract natural gasoline commercially in 1903 at Sistersville, Tt’. Va. Sutton B r o t h e r s were pioneers in t h e work. T h e Bessemer Gas Engine Company, I n the Seaboard process the hyGrove City, Pa., under the leaderdrogen sulfide is absorbed by soda ship of Frank Peterson, at once ash: interested itself in the developNa2C08 H2S ment and did much to promote NaHS NaHCOI the industry. At first, pressures of only a few pounds were used, In the hot activation LIQUIDPURIFICWION PLANT OF THE ILLINOISfor casinghead gas was utiprocess ‘Odium p h e n o x i d e ‘S h h S O U R I PIPE LINECOMPANY, W O O D RIVER,ILL. lized which was rich and easily used : (Capacity, 6 million rubic feet of gaa per day) g a v e u p i t s g a s o l i n e . Hirt, NaO” H2S NaHS H 2 0 Finley, a n d Cohen, N a t i o n a l Products Company, built an oil absorption plant in OklaREMOVAL OF WATERVAPOR FROM SATURAL G.I~ homa in 1913 on casinghead gas, simultaneously with the Drips are provided in all natural gas pipe lines for removing building of one on dry gas by the Hope Katural Gas Comwater from the gas. These are placed a t low places in the pany, a t Hastings, W. Va., although the latter company’s lines and in greatest number in proximity to a gas field or patent, by George Saybolt, was applied for in 1906. After compressor station. A reduction of temperature or an several years of litigation this patent was declared invalid increase in pressure anywhere along the line will precipitate in 1922. The court said that the oil absorption process was water. On passing through a natural gasoline plant, water merely an old process newly applied to natural gas. Particularly did they refer to a patent and operating process of will be picked up by the gas. A few plants have been built to extract water by lowering William Young, of England, granted in 1776. the temperature of the gas so that a t no time in its further In the decade beginning 1920 there was a decided swing to travel will it reach the dew point. Such plants are frequently the oil process as more and more gas became available that was too lean for extraction of its gasoline by the compression process. The efficiency of extraction of gasoline from natural gas by the compression process can be fairly well foretold, within the limits of accuracy of Raoult’s and Dalton’s laws, from the expression: HOCzHa \NH H,O -+ HOC~H,/ (C2H50)dWzOH (1) (CzH50)zNHzOH HzS C (Ci”0H)zNHzHS H,S (2)
+
++
+
+
+
+
where V , = L, = FLOWDI.4GRAM
OF
GAS DEHYDRATING PLANT
built in the neighborhood of a natural gasoline plant where propane is available as a refrigerant to cool the gas. Costs are of the order of 0.5 mill per thousand cubic feet.
SATURATING XATURAL GAS WITH WATERAND OIL VAPOR In changing manufactured gas to natural gas distributing systems the natural gas is usually saturated with water and oil vapor a t the gates of the city; otherwise, the drier natural 1
Sodium hydroxide is the active agent i n sodium phenoxide.
x, = v =
L P
= =
VI
+=
vp
xn
+1
P (100 - V ) VPV hydrocarbon in gaseous phase, mole % ’ hydrocarbon in liquid phase, mole % hydrocarbon in both phases, mole % total remaining in vapor phase, mole % total in liquid phase, mole % total pressure, lb. per sq. in. abs. vapor pressure of hydrocarbon at temperature, T V 2 + V$.. . V, = V; hence one must assume such a value for V that the sum of all the values for V , for each hydrocarbon equals V . The correct value to assume for V can be determined only by trial. Vn
=
..
The quantity of oil needed for an oil absorption plant follows from the expression:
February, 193-1 where R E P
=
= =
1-
M0 rL
TT
= = = =
I S D U S T R I .4 L .4N D E N G I N E E R I K G C H E M I S T R Y
147
oil rate, gal. per inin. hydrocarbon removed, % vapor pressure of the pure hydrocarboil, lb. per sq. in. abs. volume of gas, cu. ft. per min. molecular weight of oil absorber pressuie, lb. per sq. in. abs. neight of oil, lh. per gal.
Where the gasoline in the oil itself constituteb an appreciable percentage of the absorption oil, this expression becomes R = ( E g - L H
here L
=
) -' r;
liquid hydroearbon absorbed per minute, in moles
Thus one can, after computing the costs involved, determine the application of each of the processes to the extraction of gasoline from natural gas. As far as the oil absorption process is concerned, the quantity of absorbent oil is the greatest single factor in fixing the cost of a plant. Frequently where extremely high pressures are not primarily used to force the gas to market, a pressure of about 35 pounds per square inch gage is adopted. Here the pressures are high enough to reduce the quantity of absorbent oil to a reasonable amount and not so high that compression costs become a major item. But in any event the proper pressure to use, bearing in mind conditions peculiar to each plant, can be calculated.
ABSORPTION PLBSTS ZO-YEARINTERVAL
1NPROVEMEh.TS I S
DURISG
Early absorption plants consisted of a battery of packed or sprag absorbers, home-made double-pipe heat c>xchangers, and a horizontal shell still with an inadequate fr:tctionating tower much like those then in use in petroleum refineries. A modern absorption plant will consist of bubble type absorbers, bubble type stills, shell and tube exchangers, and a bubble type fractionating column to remove the more volatile fractions from the wild gasoline. Thus the greatest improvement has been the introduction of bubble type columns. There appeared, about 1920-22, the bubble type stabilizer to replace inefficient and wasteful weathering methods, to remove the propane and part of the butane, and to produce a relative stable gasoline for the market. The Carbide &: Carbon Chemicals Corporation patented the use of atmospheric and low-pressure rectification of natural gasoline, and purchased from the Dutch Shell Corn-
CHARGE
PUMP
FLO\\
F/NAL COOLER
RLfLUX PUMP
DIAGRAM OF STABILIZING USIT OF N A T U R ~GASOLINE L PL4NT
pany a high-pressure rectification patent, installed some lowpressure columns, and then proceeded to sue the industry in the person of the Phillips Petroleum Colnpany and the Texas Company for infringing their patents. But four courts decided, as in the case of the oil absorptioll process, that what Tvas done was an attempt to monopolize a long-known and long-used process (rectification) by applying it to natural gasoline, and declared the patents invalid. CHARCOAL
-kBSORPTIOS PROCESS
The charcoal process of absorbing gasoline from natural gas was initiated by G. G. Oberfell and the writer in 1919. =it first it possessed some advantage over the oil process in that a more stable gasoline was made, because charcoal is more selective in its action on gas than is oil. But with the advent of the stabilizer in oil plants to fractionate out the wilder gases efficiently from the finished gasoline, the charcoal process lost this advantage. In addition, heat exchange is difficult, minute oil spray in gas deteriorates the charcoal, and the charcoal is expensive. No more charcoal abiorption plants are being built in this country to extract gasoline from natural gas, although there are a half-dozen or more that have been working well for about ten years. A few plants ha\-e recently been built in Galicia. For solvent recovery work the charcoal process still possesses advantages in that these solvents usually are high priced and the charcoal process possesses a high extraction efficiency. Further extraction can be performed efficiently a t atmospheric or lower pressures, KO compressors are needed, except to force the gas through the charcoal. There are tFTo types of adsorption due, respectively, to capillary condensation and +urfaceattraction. I n regard to the former, condensation of the vapor is believed to occur in the minute pores of the solid. dbsorption by silica gel is believed to be of this type. I n the case of active carbon, adiorption is also partly of the capillary condensation type, but in addition is attributed to iurface attraction in that a layer or layers of molecules are formed in the more active surfaces of the solid. Those vapors held by capillary attraction are believed to be the ,w first given off when the vapors are recovered, while those held by surface attraction are the
148
I N D U S TI{ I A
I.
h
u I)
ENG I N E E N I N G
c 11 1%hi I s’r I< Y
Vol. 26, No. 2
Satural gasoline is of value mainly because of its wlatility. iiiilcs of the refinery to coiisumers. Propane imrl hut,aiie :ire by-products of naturnl gasoline It supplies the “light ends” for refinery motor fuel. Rut in or v a p r recovery plants a t refineries. Gmes rich plants recent ycnrs refirieries have been extracting a volatile gasoline from their refinery gases and have been producing a volatile in these constituentasfrom still8 and stabilizers are fractionated gasoline by their cracking operations so that tlie priricipai undcr the proper cmtlit.ions of temperature and pressure in niarkct for natural gasoline has decliiierl. Tlweforc, some two coluiriris. Thc raw product from tlic stabilizer passes natural gasoline plant operators supply a gasoline of tlic through a prcheatcr and R heat exchanger and enters the order of the more volatile refinery fuels-i. e., otic ready for butane coluinn from which butane is ex%racted a t the base. market without dilution with refiiiery gasoline, or with but a Propane is refluxed back in this column. The overhead small quantity of refinery gasoline. In fact, the volatile product, n mixturi: of propane and ethane mainly, passes to content of all natural gasoline has shown a marked decrease the higher pressure propanc coluniii in which ethane is rewhich is due to this cause. Thus the yield is sacrificed, fluxed back. Pure propane is witbdravu from the base. for not as much butane is incorporated in natural gasoline Thiis tho propane a.nd et,hanc are obtained in the pure state as was formerly the ease. A field for this excess hutanc, and can be mixed for distribution in any percentage desired. The pressure on the two columns depends upon the amount and for propane, is developing as the liquid gas industry develops, but this can take only a fraction of the excess a t the of propane passing overhead from the butane column and on the amount of ethane leaving the top of the propane present time. column. Such a pressure must be employed as to provide liquid reflux. Pressures are usually of the order of 300 to LIQUEFIEDNxrurinL Gas 400 pounds on the butme column and 400 to 500 pounds on The liquefied natural gas industry liad its beginning in the. propane column. 1910, when Frank Peterson, of the Bessemer Gas Engine One of the problems which confronts the producer of Company, interested himself in the subject. One year propane is the quantity which can be economically removed later I. C. Alleti and the author published a gorerriinent froni natural or refinery gas. The amount of absorption oil bulletin on the subject. Shortly thereafter A. S . and C. 11. needed to remove the hydrocarbons varies directly as the Kerr and W. 0. Snellirig commercialized these gases under vapor pressure of hydrocarbons-i. e., butane requires the name “Gxsol.” The former two have been engaged in mucli inore oil than pentane. Since the quantity of absorpthe business ever sirice and, with J. B. Garner, of the Hope tion oil largely fixes the cost of a plant, a high propane exNatural Gas Company, and B. Stroud, have done muell to traction of efficiency means high plant costs. perfect it. Ifowever, it received its greatest inipctiifi under In one estimate, there vould have been required only 6 the direction of the Phillips I’etroleum Company, G. C . gallons of oil per million eribic feet of gas to extract all of the Oberfell in charge. l’hilfuels, the Phillips product, has al- pentane, 33 per cent of the butane, and 10 per cent of the most a nationwide distribution. The author bas been engaged propane froin the gas, but 26 gallons of oil to extract all of the in the business in its various phases, first from a purely re- pentane, all of the butnnc, and 30 per cent of the propane. search standpoint, then with a plant, in 1922, making propane To remove all of the propane woiild have required 50 gallons of and butane, and now building plants for otlier people to make ,ail liquefied gas. In 1932 about 33,000,000 gallons of propane arid butane CAKBONBLACK were made. This is equivalent only to 2.5 billion cubic feet Coiriinercial carbon black was first made a t New Cumberof 1000 B. t. u. natural gas; hence, the industry cannot yet be considered a large one. But it is growing and the gas is land, W. Va., in 1872, hy Hanorth and Lamb. Natural used for metal cutting, cooking in outlying districts, cam- gas flames impinged upon soapstone slabs, and a scraper munity distribution in street pipe lines, enriching water gas, removed the black. The forerunner of the channel type of meeting peak load conditions of gas companies, and reforming plant was that of A. R. Blwd, who used a small rotating disk hy cracking to make a low B. t. u. gas; i t is also utilized for that moved over the gas flames. He next proceeded to a ~1.4.
February, 1934
INDUSTRIAL
AND ENGINEERING
roller process which gave him a high-quality black. Channel beams of reciprocating action were first used by L. J . McSutt, in 1892. At the present time the channel process, developed from hIcNutt’s early work, produces 90 per cent of the black of the country. Other processes are the small rotating disk, large plate, roller, and the Thermotonic process of gas cracking developed by Brownlee and Uhlinger. The principal reaction which characterizes the formation of carbon black follows: CHI
+ heat -+-C + 2H2
(1)
Equation 1 is a simple cracking reaction and is probably the main source of the black. Reactions also occur, of course, n.hich supply the heat, as follows:
+ + + ++
+ +
CH, 2 0 2 -+ CO, 2Hz0 heat CH, O2 +CO H2 H 2 0 heat
(2) (3)
Other reactions are those which tend to destroy the carbon after it has been formed by reaction 3:
+ *2co + H20 +CO + H, c + co, +2co
2c
C
0 2
(4)
(5) (6)
CHEMISTRY
149
thereon possess different physical characteristics from those of the free molecules. REFORMING SATURAL GAS
X development of recent years has been the reforming (cracking) of natural and refinery gases to produce a gas of lower heating value and more in keeping with the manufactured gas that may already be in use in a certain district, when the supply is to be augmented by the reformed gas. For instance, where a gas of too high heating value is turned into gas appliances set for a lower heating value, thousands of burner and pressure adjustments have to be made in a gas-distributing system. Further, natural gas is sold on a cubic foot basis, regardless of its heating ralue. Hence refinery or rich casinghead gas (for example of 1400 B. t. u. value) can be reduced to 900 B. t. u., and the quantity of gas increased by perhaps 50 per cent. To reduce the heating value, various expedients have been adopted. Several companies merely burn a portion of their natural gas; the flue gas thus produced, scrubbed of impurities, is turned into the gas mains in sufficient quantity to lower the heating value of the gas. This practice, however, raises the specific gravity of the gas, as a minor objection, but the chief trouble is that consumers do not take kindly to dilution of their gas with “smoke,” as they call it. At the moment, two processes are mainly used for reforming high B. t. u. gases. I n a water gas set the rich gas is introduced alternately with the steam and coke; in the Dayton process the gas is burned in incomplete combustion. I n each case a thermal recovery of 85 to 90 per cent is obtained. The heating value is lowered, but an increased volume of gas is obtained.
Reaction 1 has to be promoted as much as possible and 4, 5, and 6 retarded. Reactions 2 and 3 are necessary, but conditions which favor them also favor 4. For, if one increases the air, the latter reaction is speeded up and reaction 3 also increases. To smother the flame to retard reactions 4, 5, and 6, flame temperatures are lowered and cracking is reduced, in reaction 1. Hence, a compromise must be effected. The bottom zone or blue portion of the flame in a carbon BY-PRODUCTS FROM NATURAL GAS black house is where tlie heat generating reactions (2 and 3) Aside from natural gasoline, liquefied gas, carbon black, and take place. I n the mid.dle luminous zone, cracking reaction 1 occurs. I n the top zone reactions 4, 5, and 6 predominate. helium, by-products or products from natural gas have been Therefore, the collecting channel is located so that its surface practically nil, except alcohols and acetates produced from is in contact with the middle zone. Thus, the cracked carbon natural gasoline by the Sharples Company, and glycols and is deposited on the channel which carries i t away so that it certain solvents from cracked natural gas, by the Carbide & Carbon Chemicals Corporation, both with plants located a t cannot reach the upper zone where it would be destroyed. As soon as the carbon is liberated in the flame, it becomes Charleston, W. Va. B. Lacey, in 1916, built a plant near Charleston to fracluminous and emits electrons, thus electrically charging itself. Hence, particles of carbon do not coagulate but are tionate methane from natural gas to produce methyl chloride attracted to the electrically neutral grounded channel, owing by chlorination, and for a time the Empire Refining Comto the latter’s induced surface charge. Thus the particles pany produced certain oxidized and chlorinated products are withdrawn from f r o m natural gas a t VAL V€ the f l a m e , c o o l e d , their Okmulgee reand protected to a finery. considerable degree M u c h work h a s from the destructive been done on highaction of the flame. temperature c r a c k Just why carbon ing, of t h e o r d e r of black makes such a 900” to 1200” c., of good filler for rubber natural gas (particuis not w e l l u n d e r larly rich gas) and stood, except that it refinery gas to proi n v o l v e s t h e hysduce aromatics, t e r e s i s effect. Not principally benzene; as much h e a t is but the heat requireevolved in the work m e n t s a r e so high, of e x p a n s i o n a n d and tubes or crackcontraction of a tire i n g c h a m b e r s dewhen it is in action. teriorate so rapidly Carbon black that, to the author’s possesses an enormous knowledge, no comsurface, and rubber mercial plants are in molecules a b s o r b ed FLOWD I A G R A M OF PROPANE-BUTANE PLANT existence.
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Wheeler and Hague were the first to show that the time element is of great importance in cracking methane to produce liquid products, just as in oil cracking operations. At still higher temperatures, of the order of 1500” to 1600” C., acetylene is formed by cracking natural gas: CHa
CHz
+ HB
+ CHI C - CZHB CZHB e CzHz + 2H2 CZHz e 2C + H? CHz
Seither of these processes appears to be far from the commercial stage, in localities where natural gas is rich, cheap, and abundant. Much work has been done by many experimenters to utilize natural gas by methods other than burning, but only a negligible quantity of the gas is so consumed.
REFINERY GAS The amount of gas produced a t refineries in 1929 was 520 billion cubic feet, according to Egloff and Morrell, of which 270 billion came from cracking stills and 250 billion from straight-run refining stills. This is greater than the amount of manufactured gas in the United States-that is, gas manufactured from coal and oil in gas plants for domestic and
Vol. 26, No. 2
industrial purposes. This refinery gas is burned mainly as fuel under stills and boilers, although some is sold for outside purposes, and a small quantity is cracked (reformed) to produce a lower heating value gas of greater volume. Most of this gas is scrubbed, or compressed and cooled, to extract the gasoline, and in a few cases liquefied gases, propane, and butane are prepared from it. The first plant (called “vapor recovery plant”) to extract gasoline from the refinery gases, to the author’s knowledge, was built a t the Bayonne refinery of the Tidewater Oil Company, in 1917. Improvements in vapor recovery plants followed in natural gasoline plants (at first compression plants) ; oil absorption plants were then developed which were later equipped with stabilizers. By-products from refinery gases consist of the absorption of the unsaturates in sulfuric acid to make higher alcohols by the Standard Oil Company of New Jersey, and the Empire Refineries Company. I n cracking oil to make highly unsaturated gases for their line of solvents the Carbide & Carbon Chemicals Corporation produces ethyl alcohol from ethylene, which is sufficient for its own process needs. Ethylene is first made and absorbed in a mixture of sulfuric acid and ethyl hydrogen sulfide, and then diluted with water and distilled. Much that has been said in this review on natural gas is applicable to refinery gas. RECEIVED August 9. 1933
Progress in Coal Carbonization, Gas-Making, and By-product Recovery HORACE C. PORTER, 1833 Chestnut St., Philadelphia, Pa.
D
IFFICULTY has been The past twenty-jive years have seen much imof other Ikll-grade solid fuels, provement in and eficienciesof producthere is no commercial induceencountered in forcing the growth of coal carment for carbonization. Altion and in quality of products; volume of bythough the development of gas bonization merely on the grounds of improving the raw coal, renProduct )*ecOuerY,especially gas, has gained; but and by-product sales has gone ahead in a measure, it has of late dering i t smokeless, or providing carbonization growth as a whole is disappointing because of the competition of natural gas and oil years s l a c k e n e d and may go valuable chemical by-products. This Was m u c h t a l k e d of a Slowly in the future. as fuels, and of synthetic chemicals. Coke for Burning p r o c e s s e d c o a l i n q u a r t e r - c e n t u r y ago, and a domestic fires has gained and, together with bypower plants has not been, nor strong effort was made through government and industrial chanProduct coal gas for Public distribution where can be, p r o m o t e d w i t h o u t natural gas cannot projitably reach, offers the best demonstration of financial adnels, on these grounds, to decrease the burning of coal raw outlook for future growth. Low-temperature capvantage to the operator. Coal gas, especially as a bybonization has made no commercial progress in with attendant smoke and loss of by-products. There has been product from coke ovens, has the bTnitedStates but in England and Germany is been enjoying increasing sales, accomplished, to be sure, during the last 20 to 25 years a considercoming to the front slowly, assisted by the demand since gas in general is growing in there f o r free-burning fireplace fuel and for oils popularityas afuel. But of late able growth of carbonization with by-product recovery. The other than petroleum. years large expansion of natural gas distribution and a consideruse of nonrecovery or ‘(beehive” able growth of the use of refinery ovens in the United States has fallen to 10 per cent or less of all carbonization and is retained g a j and “bottled” petroleum gases have retarded the rate of merely as a cushion or reserve for handling at lower cost the coal gas growth. By-products, as later noted in detail, now offer little help peak requirements of industry. Beyond, however, the demands of the metallurgical indus- in the expansion of coal carbonization. Our requirements of try for coke and of the gas utilities for by-product coal gas, the coal-tar fractions necessary for the making of dyes, plasit has been difficult to carry carbonization profitably. Fuel tics, and pharmaceuticals are more than met by present home consumers in general, except to some extent the domestic, production; the ammonia market is oversupplied ; motor fuels will not pay a premium price merely for the sake of smokeless- of antiknock quality are obtained as cheaply from other sources ness. Unless therefore the gas and by-products of carboniza- as by benzene blends. This does not mean that coal by-prodtion can be sold for enough to keep the coke price to the level ucts cannot be sold in increasing quantities, but it does
