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assumption be made that this residual gas was ethane only, then it can be calculated that 3,331.7 liters of gaseous ethane at 16° C. (60° F.) and 30 inches of mercury is equivalent to 2.7 gallons of liquid ethane. This quantity of liquid is so small as to seem insignificant, although as regards raising the vapor pressure of the condensate it is important.
LIFE OF WELLS AS REGARDS PROFITABLE GASOLINE EXTRACTION.
Some conclusion regarding the length of time that gasoline may be profitably extracted from the natural gas of a given well may be gained by referring to the history of past operations. In the East gasoline-extraction plants have been in operation for several years. An important factor is the quantity of oil present. Neither gas nor oil wells are as long lived in the Mid-Continent as in the Eastern fields. It would appear therefore that in the Mid-Continent field, gasoline operations will not have as long life as those in the Eastern fields. They will probably last longer, however, than those in the California fields. Operations for the recovery of gasoline from casing-head gas in the old Tidioute, Pa., region, where profitable yields of gasoline are obtained at very low pressures, have continued for five years. These wells have been producing gas and oil under vacuum for 40 years prior to the actual installation of gasoline plants. The authors have definite information regarding the installation of a plant at Parkersburg, W. Va., that operates on wells that have been under vacuum for 29 years. After two years' operation of the gasoline plant the quantity of gas began to decline rapidly. General conclusions can not, however, be drawn from this plant.
Around Sisterville, W. Va., there are probably more plants for the recovery of gasoline from casing-head gas than at any other place in the United States. Oil wells in that district have operated under a vacuum for 15 or 20 years. Within the town limits some wells operating under a reduced pressure of 24 inches of mercury produce 1 barrel of gasoline a day. The fact that the engines use city gas, there being no residual gas left, shows the absence of much permanent gas in the wells. Certain oil wells may produce considerable gas when gasoline recovery is started but eventually the gas ceases to flow, and a reduction of pressure withdraws no gas from the well but simply removes the gasoline fractions.
The Glenn pool in the Oklahoma fields has, the authors believe, already shown indications of having a long life. The application of reduced pressure to the wells has increased both the gasoline and the oil yield.
The authors can not predict the life of gasoline-plant operations in general in the Oklahoma fields. With reference to the Glenn pool
fields, however, they believe that it would be entirely safe to predict a life of profitable gasoline operation equal to that which can be realized with the oil itself. There are some other regions in Oklahoma that have shown particularly unreliable indications as to casing-head gas, there having been a considerable volume of gas in new wells, which later dwindled rapidly. This tendency seems to be common with the shallow sands, a possible exception being a pool known as the Childer's pool in the Delaware region. When gas escapes freely from wells that have been producing oil for two or three years, they may be expected to produce gas enough to assure the return of the initial investment with profit.
CONDENSATION OF GASOLINE BY REFRIGERATION. METHODS OF PLANT AT OLINDA, CAL.
In a plant at Olinda, Cal., the gasoline is condensed by refrigeration at low temperatures. Ammonia is the refrigerating agent used. Plate IV, C, shows a general view of this plant.
In a letter to the authors, the president of the company stated that in a day of 24 hours 300,000 cubic feet of gas was used, from which was extracted 1,200 gallons of condensate.
Seven condensing coils are used. They are laid side by side and connected to each other by headers. In the first two ammonia refrigeration is not used. A considerable drop of temperature is obtained in these coils, however, by causing the gas to expand into them. The temperature in No. 1 and No. 2 stills is approximately 150° F. (66° C.), in No. 3 still 65° F. (18° C.), in No. 4 still 50° F. (10° C.), in No. 5 still 40° F. (4° C.), in No. 6 still 30° F. (-1°C.), and in No. 7 still 14° F. (−10° C.) The condensate precipitated in the No. 1 still is said to have a specific gravity of about 60° B., in the No. 2 still 62° B., in the No. 3 still 70° B., in the No. 4 still 74° B., in the the No. 5 still 80° B., in the No. 6 still 84° B., and in the No. 7 still 95° B. The condensates are finally all mixed together, producing a mixture with a specific gravity of 80° B.
The company pays 32 cents per pound for ammonia. Approximately 400 pounds was required to charge the machine in September, 1913. Up to March 5, 1914, the charge had not been renewed. The ammonia is delivered to the compressor at a pressure of approximately 15 pounds per square inch, and leaves the compressor at a pressure of 150 pounds.
DESCRIPTION OF ORDINARY AMMONIA REFRIGERATING
An ordinary ammonia refrigerating machine such as is used for cooling purposes in general consists essentially of three parts-a refrigerator or evaporator, a compression pump, and a condenser.
The refrigerator, which consists of a coil or a series of coils, is connected to the suction side of the pump, and the delivery from the pump is connected to the condenser, which is generally of a somewhat similar construction to the refrigerator. The condenser and the refrigerator are joined by a pipe in which is a valve called the regulator. Outside the refrigerating coils is the air, brine, or other substance that is to be cooled in the refrigeration system; and outside the condenser is the cooling medium, which is water. The liquid ammonia passes from the bottom of the condenser through the regulating valve into the refrigerator in a continuous stream. As the pressure in the refrigerator is reduced by the pump and maintained at such a degree as to give the desired boiling point-which is, of course, always lower than the temperature outside the coils-heat passes from the substance outside through the coil surfaces and is taken up by the entering liquid, which is converted into vapor. The vapors thus generated are drawn into the pump, compressed, and discharged into the condenser, the temperature of which is somewhat above that of the cooling water. Heat is transferred from the compressed vapor to the cooling water, and the vapor is converted into a liquid which collects at the bottom and returns by the regulating valve into the refrigerator. The compressor may be driven by a gas engine or in any other convenient manner. The pressure in the condenser varies according to the temperature of the cooling water, and that in the refrigerator is dependent upon the temperature to which the outside substance is cooled.
Anhydrous ammonia is a gas at ordinary temperatures and under atmospheric temperatures. The liquid anhydrous ammonia is commercially sold in iron drums in which it is contained under a pressure varying between 120 and 200 pounds per square inch, the pressure in the drum depending on the temperature of the liquid in it.
Some idea of the nature of the natural-gas condensate obtained can be had by considering the liquefaction points of the constituents that are found in natural gases used for gasoline condensation. The boiling point of liquid propane is -45° C. (-49° F.), and of liquid butane 1° C. (34° F.).
The lowest temperature obtained in the refrigerating coils of the Olinda plant is -10° C. (14° F.). Hence it can be accepted that no propane is liquefied, but some butane and higher paraffins are. The efficiency of the extraction of the condensible constituents from the natural gas for any given temperature will depend upon the velocity of the gas through the coils, or, what is the same thing, the area of cooling surface. Heat is of course extracted from the natural gas when it enters the cooling system. If the cooling area of the
pipes is not great enough, the residual natural gas will leave the system still containing gasoline vapors that could have been condensed by further cooling treatment. By proper experimentation the amount of cooling surface required to produce the greatest quantity of salable condensate can be ascertained. Presumably the operators of the Olinda plant have made such a determination. The authors are not closely acquainted with its operations. They believe that the refrigeration method offers much promise and that more plants of this type will be installed.
In the United States at least 85 per cent of the refrigeration plants used for various purposes use ammonia as the refrigerant. Other refrigerants that may be used are sulphur dioxide, carbon dioxide, and water vapor.
TRANSPORTATION OF NATURAL-GAS GASOLINE.
After the production of gasoline from natural gas became a commercial success, the matter of the best methods of transporting it became important. Some of the product when first drawn from the storage tanks may have a specific gravity as high as 100° B. Some condensates are even lighter than this. The exact nature of the product was not clearly understood during the inception of the industry, and in transporting it pressures developed in the containers great enough to burst some of them. Several serious accidents occurred. It was quickly recognized that the material as freshly drawn was not suitable for transportation in containers such as were used for handling ordinary gasoline. Weathering the condensate and blending it with refinery naphtha so that a liquid was obtainable that upon evaporation would not develop excessive pressures overcame the difficulty. However, compulsory rules for its transportation that could be met by the producers were recognized as necessary. Consequently B. W. Dunn, Chief of the Bureau for the Safe Transportation of Explosives, called a meeting of producers at Pittsburgh, Pa., on May 26, 1911. Recommendations were adopted indicating the method of shipping the condensate pending the drafting of final regulations.
Col. Dunn recommended that the producers determine the vapor pressure of their product at 100° F. (38° C.), and sent inspectors to those producers who used tank cars in shipping their product. A tentative maximum vapor pressure was set at 10 pounds per square inch for a temperature of 100° F. (38° C.).
Tank cars differed widely in their construction and many were not suitable for carrying a highly volatile liquid. Consequently, it was recommended that only standard tank cars should be employed.
RULES OF THE INTERSTATE COMMERCE COMMISSION.
The final rules of the Interstate Commerce Commission regarding the shipment of natural-gas gasoline are presented below.
REGULATIONS FOR THE TRANSPORTATION ON RAILROADS OF NATURAL-GAS
Liquefied petroleum gas is a condensate from the "casing-head gas" of petroleum oil wells, whose vapor tension at 100° F. (38° C.) (90° F.-32° C.-November 1 to March 1) exceeds 10 pounds per square inch. Liquefied petroleum gas must be shipped in metal drums or barrels which comply with "Shipping-Container Specifications No. 5," or in tank cars especially constructed and approved for this service by the Master Car Builders' Association.
When the vapor tension at 100° F. (38° C.) exceeds 25 pounds per square inch, cylinders as prescribed for compressed gas must be used.
(The commission has not deemed it best at this time to prohibit the use of good wooden barrels in shipping inflammable liquids with a flash point below 20° F. (-7° C.). It is, however, expected that their use for that purpose will be gradually discontinued and that within a reasonable time metal barrels will come into general use for such shipments.)
Packages containing inflammable liquids must not be entirely filled. Sufficient interior space must be left vacant to prevent distortion by containers when heated to a temperature of 120° F. (49° C.). This vacant space must not be less than 2 per cent of the capacity of the container, including the dome capacity of tank cars.
1. The provisions of "Shipping-Container Specifications No. 5" apply to all containers specified therein that are purchased after December 31, 1911, and used for the shipment of dangerous articles other than explosives. Each such container purchased subsequently to December 31, 1911, shall have plainly stamped thereon the date of manufacture thereof.
2. An iron or steel barrel or drum with a capacity of from 50 to 55 gallons must have a minimum weight in the black, exclusive of the weight of rolling hoops, of 70 pounds, and the minimum thickness of metal in any part of the completed barrel must not be less than that of No. 16 gage United States standard.
3. An iron or steel barrel or drum with a capacity of from 100 to 110 gallons must have a minimum weight in the black, exclusive of the rolling hoops, of not less than 130 pounds, and the minimum thickness of metal in any part of the completed barrel or drum must not be less than that of full No. 14 gage United States standard.
4. Each barrel or drum must stand without leaking a manufacturers' test under water by interior compressed air at a pressure of not less than 15 pounds per square inch sustained for not less than two minutes, and the type of barrel or drum must be capable of standing without any serious permanent deformation and without leaking a hydrostatic test pressure of not less than 40 pounds per square inch, sustained for not less than five minutes.
5. When filled with water to 98 per cent of its capacity, the type of barrel or drum must also be capable of standing without leakage a test drop on its chime for a height of 4 feet upon a solid concrete foundation.
6. Bungs and other openings must be provided with secure closing devices that will not permit leakage through them. Threaded metal plugs must be close fitting. Gaskets must be made of lead, leather, or other suitable material. Wooden plugs must be covered with a suitable coating and must have a driving fit into a tapered hole.
a From "Regulations of the Interstate Commerce Commission for the Transportation of Explosives and Other Dangerous Articles by Freight and by Express, and Specifications for Shipping Containers,” published by the Bureau for the Safe Transportation of Explosives and Other Dangerous Articles, in January, 1912, pp. 72, 143, 144, and 145. Effective Mar. 31, 1912.