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Vol. 22, No. 12
Natural Gasoline in California’ Plant Installed by the Foster Wheeler Corporation for the Los Nietos Producing and Refining Go., Ltd., Kettleman Hills, Calif. G. Ross Robertson UKIVERSITY OF CALIFORMA AT Los ANCELES
The largest gasoline absorption plant ever built on a valves in a beautiful apple BOUT seven years ago single order has recently been put into service in the green. In these arid hills certain renowned but new miracle oil field of Kettleman Hills, Calif. Eighty there is little rusting and no pessimistic geologists thousand gallons of absorption gasoline is the daily predicted a dire shortage of grime. output from about ninety million cubic feet of wet petroleum in the U n i t e d The well doesn’t deliver natural gas. New engineering efficiency is giving ex“crude oil” in the ordinary States wiithjn ten years. ceptional yields with strict adherence to distillation They still have three years’ sense. Rather it pours out a standards. This production is augmented by an grace in which to fulfil exmammoth stream of native, unusually high gasoline content of the accompanying ready-made raw gasoline, acDectations. Thereare, on the crude oil. bther hand, three substantial companied by vast quantities elements of doubt attached to of high-pressure gas. By that prediction. These are, respectively, Texas, Oklahoma, some remarkable provision of nature, Kettleman “oil” is comand California. Just at present the greatest of these seems to posed almost entirely of volatile hydrocarbons. I n some cases be California. At least may it be said that the Kettleman the liquid is almost Ivater-white as delivered from the casinghead. At other wells the product, while free-running as comHills were not on the oil map in 1923. The false prophets have done us no harm. They probably mercial gasoline, is colored in varying shades of brown. One enterprising Kettleman operator subjects the oil to a frightened us into a speedy development of ethyl gasoline, cracked petroleum, and various other commendable econo- slight purification, not involving distillation, and markets mies. One of these economies is the stripping of volatile it directly as motor fuel. The trade seems to be satisfied nith its Derformance, and likes the cut price. gasoline from wet natural gas. The visitor to Kettleman is The limited demand for kerosene in recent years has inyited t o hold his hand under made it desirable to throw an increased fraction of heavier the discharge valve on the hydrocarbons into motor fuel. Such heavy distillates need oil trap at the well. 4 light enrichment with a special supply of volatile material. Thus liquid pours over his hand. has arisen the modern natural-gasoline absorption plant One or two shakes of the hand which salvages the desired fuel.
A
Riches in the Desert
Time was when an absorption plant took care of forty or fifty wells in its neighborhood. Two Kettleman wells are sufficient to serve the plant described herewith. When one of these is drilled to the full projected depth, it is quite possible that it may take over the whole duty alone. The present production of over 80,000 gallons of high-grade absorption gasoline daily means that more than 500,000 gallons of motor fuel may be marketed after blending with straight distilled gasoline. The Kettleman field is a wide stretch of rolling hills far out in the midst of the barren, sun-baked valley of central California, a few miles south of Coalinga. Literally hundreds of square miles of bare clay loam surround these hills. Bny one of these square miles is a perfectly good airport. Oil magnates with private planes visit their property without much concern as to their skill in selecting a landing place. Sear the western edge of the hills the shack town of Avena1 has suddenly sprung out of nothing. The town is not substantial, but it is clean-looking. This is a new idea in oil towns, and there’s a reason. Gasoline Wells
After experiences in old-fashioned oil fields the visitor expects to find a succession of grimy derricks, ill-smelling black oil sumps, and an atmosphere soaked with crude oil mist. Not so. Instead of muck and mire, one finds at a Kettleman well a spick-and-span outfit, resplendent in aluminum paint, with gas valT-es done in vermilion and oil 1 Received
September 22, 1930.
SAC RAM€ N TO
I ,
Figure 1-Map
Showing Location of Kettleman Hi
in the air and the liquid has evaporated, leaving only a slight smell which suggests that Kature did not refine her product quite well enough to pass a city motor-fuel ordinance. A Modern Oil Well
The following may be taken as a normal or composite picture of a mature, full-grown Kettleman oil well. It is about 8000 feet deep. It probably cost about $200,000 to drill or, if there were bad luck in the last thousand
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Fieure 2- -Kettleman Ililla from the All Showin$ Lea Kiefos Plant in the Center
feet, add a couple of hundred Cliousarid more. It pours ont daily, in a foaming and roaring stream, 5000 barrcls of volatile petrolcum, marketable at double the price of co~nmon cnide oil. The gravity of the liquid is ahout 65" A. P. 1. Wil.liout further treatment this oil is already slightly superior to some of the "bootleg" gasoline sold by miiior coiiceriis outside tlie cities. If the well has reached a particularly deep oil sa.nd, there may he a small hot important fraction of luhricatiiig oil in the crude product. Out of the foaming stream come 100 million cubic feet of wet natural gas daily, at a pressure of 1000 pounds per square inch. This gas goes througli an absorpt.ion plant, and gives up a,bout 90,000 gallons of high4est gasoline. The remainder, mostly metliane, is thrown away. The Los Nietos Plant
Rising spotless and shining in the brilliant California sunshine, tlie new absorption plant is a beautiful sight by contrast with the drab and barren clay hills round ahout. Only the offices, laboratory, and a few picccs of minor rquipment are housed. Itailis come seldom and sleet never. Everything takes the fresh air-the more air tlie better, should natural gas ehoosc to leak out a t sonie unsnspect,ed point,. At the present writing the two connected wells nearby deliver daily 92 inillion cubic feet of wet gas througli a 14iiicli main a t a regulated pressure of 450 pounds. Quite nat,urally the oil which has jnst been separated from its
equilibrioni contact u7it.h the high-prcssnre gas contains a large proportion of the much-desired iriterinediate liydrocarbons, such as the pentanes and hexanes. Accordingly a second and third quota of gas arc taken off froin the oil, each at reduced pressure. The final withdrawal of gas is made at a slight vacuum, leaving the liquid product relatively stable in tank storage. The n M e supply of wet gas is sent to the absorbers, shown to the right of Figure 4. Extraction of Gasoline
The plant consists of two absorption units, each having a capacity of 50 niillion cubic feet a day; a stabilizer taking care of both irnits; a boiler plant with four operating units and one stand-by; a cooling tower serving several devices; gasoline storage tanks, centrifugal and piston pumps, compressors, etc. Briefly summarized, it opcrates to extrap,t most of the liydrocarbon content of the gas from propane np the series; then to reject by fract,ionation some n-butane and everything below butane from the criide distillate produced. A cliernical conccpt of the absorption problem may be gained from a typical analysis of Kcttlrman wet gas. Per a n i by i.OI+LWIS
Methane
IZihnne
Pr0pa"e lrobutrnc n-8"ia"e Pe"LancS-pl"3
83.26 8.54 4.7n 1.06
Golions l i w i d *cr M 6". .ff. .L*l
0.35
1.54
0.49
1.10
0.47
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this way a high gas solubility is attained, and at the same time a low loss of oil in distillation of the gasoline from the absorbed mixture, or “fat oil.” About 675,000 gallons of oil circulate normally through the plant cycle. I n Figure 4 it will be noted that all piping enters the absorbers through side walls, leaving the flanged top covers unhampered and easily removable for repairs. The interior trays are in sections, and are easily removed without disturbance of piping. All’ the desired hydrocarbons, and many more, are now absorbed in the foaming, dripping mass of oil in the absorber columns. The “dry gas” escaping absorption is promptly diverted. A sample of this gas had the following composition:
...............................
Nlefhlne Ethane ................................. Propane................................ lsobutanr ..............................
............................. Pentmer-plur........................... n-14utane..
~
n,, .
,,”*
85.81 8.14 4.0 0.18 0.47
0
This X . t. u. v a l u ~ , ~ gas is ~ approximately b ~ of 1100 ~ and is Dracticallv identical with the fuel which is now stahdard in &mestic service a t Los Angeles. Absorption reduces the volume of the gas only about 8 per cent, so that more than 80 million cubic feet must now be disposed of.
F I ~ W 3-General ~ view or LOR ~ i e t o sPI^^^, showing ~i~~ ~ b units~ to the Left, Water Tower and Bolter Plant tu the Rear. and Storage Tanks for Finished Gasoline In Foreground
From the absorption standpoint methane and ethane are worthless. They dissolve slightly in the ahsorher oil at high pressure, hut soon escape the apparatus. Propane, b. p. -45’ C., is equally worthless, being too volatile to remain in appreciable quantity in a motor fuel as commonly stored. It is, however, sufficiently condensable to make trouble further on in the plant process. It is accordingly eliminated completely only after careful fractionation. The isobntane, b. p. -11” C . , is almost worthless, and goes largely with the propane. n-Butane, b. p. 1 “ C . , is a normal component of ahsorp tion gasoline, hut there is nearly 50 per cent more of this hydrocarbon in Kettleman gas than the final product can stand. There must accordingly be a substantial rejection of butane. “Pentanes-plus,” meaning all higher hydrocarbons, are the most desired, and the plant is designed to give practically complete recovery of such material. Undoubtedly there is a large amount of hexanes and heptanes, with dwindling percentages of a few higher members of the series and possibly cyelo compounds of unknown quantity. Practically no other gas is present. Absorption
The wet gas, at 450 pounds pressure, enters the absorbers, w h e r e the soluble components dissolve rapidly in the oil which partially fills the towers. This oil is a relatively nonvolatile r e f i n e d petroleum of the “mineral seal” type, somewhat heavier than kerosene. Io it are combined as high as p o s s i b l e a boiling range with minimum molecular weight. I n
Gas-Propelled Turbines
A portion of the dry gas is put to novel use in driving turbines which serve the necessary primps of various kinds. I n the face of dubious comments of tnrbine engineers, the huilders of this plant have succeeded in driving standard steam turbines on high-pressure gas with even less damage to interior parts than occurs with steam itself. For this purpose the gas is reduced to 185 pounds pressure, heated with exhaust steam to forestall the formation of ice in the turbines, and then put to work. The existence of casinghead pressures up to 1100 pounds has suggested the use of gas in electric power plants, in which the energy would he derived merely from the expansion of the gas, after whieh the expanded but undamaged gas would be sold as fuel. Unfortunately the gas occurs st a distance of more t,han 200 miles from the nearest industrial center, and a large part of the I100 pounds pressure would be needed to boost the fuel to its destination without allowance for electric power produetion. Kot all has been said on this s u b j e c t , howevcr. I n t h e meantime the use of gas in turbines is saving much steam in the Los Nietos plant. A small amount of thedry gasisreduced to very low pressnre and used as fuel under the boilers. The remainFlgure 4-View from West End, Showing F*acfionators and Sfabillzer to the d e r , which is n e a r l y Left, Absorbers to the Rlghf, and Water Tower t o the Rear
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the whole supply, is led out a safe distance up a hill and blown off to the atmosphere as waste.
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pense of boiler equipment, not fuel. At the Los Nietos plant the fire boxes of the boiler plant have been equipped with “water walls,” a new departure in steam engineering as applied to gasoline plants. The lining of the h box with water tubes in circulation with the boiler proper give8 phenomenal increases in steam output. In practice the water walls generate much more steam than the boiler itself. A maximum amount of cheap brick can he used in boiler installation, and the investment per unit of steam is unusually low. Fractionation de Luxe The rest of the plant is one grand elaboration of fractional distillation and condensation, whose purpose is to reject the very volatile hydrocarbons most neatly without losa of the pentanes, hexanes, and higher components. The vapors emerging from the fractionator pass in turn through a primary water..cooled condenser, a primary dehydrator, and then a secondary condenser and dehydrator. Automatic separatory devices permit a continuous flow of raw gasoline and recondensed water. The dehydratom are merely tanks with weirs, and play the role of separator). funnel.
Figure 5-Stabilizer
and Frsstlonating Unite
Recovery of Gasoline The “fat oil” from the absorbers, saturated with all the hydrocarbons, passes through tanks, where a slight relief of pressure vents a large part of the methane, ethane, and propane. It then passes to the pressure heat exchanger, an outstanding feature of the plant. Here by application of the coupercurrent principle, piped streams of f a t oil pass a distance of about GO feet counter to the returning “lean oil” from which the gasoline has been stripped. The contact is of course thermal, not an actual liquid contact. I n this way the lean oil is cooled with great saving in precious water. The fat oil in turn becomes heated, thus saving much steam. Instead of an extension of the system of countercurrent heat exchange along a single GO-foot length of piping, the whole system has been condensed into a compact unit suggestive of a small boiler, with ingenious baffle and tube arrangement for repeated criss-cross p a a g e of heating and cooling currents. So designed, the new form of heat exchanger is much more convenient to handle than the more lengthy apparatus previously used. A high heat efficiency has been attained, in that the temperature approach of lean and fat oil has been reduced, a t the cold fatoil end, to the low value of 20 Fahrenheit degrees. The fat oil is still further heated in the second or gravity heat exchanger, and thence passes to the preheater, where i t receives a temperature boost with the aid of boiler steam. The oil then passes to the fractionator, where it is subjected to steam distillation. Economy of Steam At iirst one wonders why anybody worries over heat economies in a plant which throws away 90 billion B. t. u. of gas per day. The answer is found, of course, in the ex-
Figure 6-One of Two Fractlonatine. Units for Recovering Raw Gaaoilne from Absorption OU
Return Cycle of Oil The hot oil-now lean-returns through the heat exchanger, yields a part of its heat energy, and is ready to do business once more a t the absorber. During the day some 500 or GO0 gallons of this oil are lost into the product. So small is this loss that the presence of the oil in the finished gasoline is not serious enough to interfere with a good Engler test. Raw Gasoline The raw gasoline from the dehydrator is not yet ready for shipment. In the olden time material of this sort waa sold to low-class refiners, who blithely mixed it with cheap kerosene and retailed it to the unsuspecting motoring public. Since it contained both the very light and very h e a v hydrocarbons, its gravity test struck a satisfactory average. Since i t contained plenty of n-butane, isohutane, and even
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some propane, the fuel did not fail to start the automobile motor in lively fashion. The kerosene component in part escaped through the muffler, somewhat battered in transit; in part it diluted the crankcase oil so copiously that the motorist became very enthusiastic over the wonderful lasting quality of his lubricant. Strict Gasoline Standards
The major companies which purchase absorption gasoline for blending purposes have long been enforcing strict limits in the composition of the material. They will not accept a product containing propane and excessive butanes. Their requirements necessitate the treatment of the raw gasoline in a stabilizer, which is simply an apparatus for partial evaporation under reflux, and with efficient fractionating devices. As seen in the flow sheet, much of the gasoline probably makes several round trips through the kettle, stabilizer tower, condenser, reflux receiver, and heat exchanger. At the reflux receiver the uncondensed vapors are vented. A sample of these vapors gave the following analysis: Methane., ............................ Ethane. . . . . . . . . . . . . . . . .
Per cent 2.34 21.43
n-Butane. .............................. Pentanes-plus..
