Production of Helium reau of Mines, took immediate issue with that remark, and to verify his contention read a part of a letter from William Ramsay of England in which the suggestion was made that the United States produce enough helium t o inflate lighterthan-air craft for the Allies. That suggestion was made a t a time when I was selling small quantities of helium a t the rate of $2500 a cubic foot; a t that price it would have taken more than $100,000,000 to fill a small blimp. From Dr. Cady’s paper you have learned that even in the face of such seemingly impossible odds, the scientists of this country accepted the challenge and made good. I n 1917 there were not 2 cubic feet of helium in America, certainlv n o t enough with
P. CADY can lay claim not only to the discovery of the presence of helium in natural gas, but to an active interest of more than one-third of a century in matters pertaining to that element. I have just come of age so far as my connection with helium is concerned. Twenty-one years ago this month, I read a paper a t the 54th Meeting of this SOCIETYa t Mstnsas City concerning an investigation performed under the direction of Dr. Cady. The research dealt with the presence of the rare gases in natural gas, and a t the end of the presentation I expressed regret that the work did not have a practical application. R. B. Moore, of the Bu-
H.
848
at Amarillo-
=
C. W.SEIBEL U. S. Bureau of Mines, Amarillo, Texas
-
tory, more efficient plants could be designed for the future. In due course, workers in that research laboratory, established in Washington, D. C., supplied the answers to many questions dealing with such factors as specific heats, phase equilibria, solubility of helium in the liquid components of natural gas, behavior of metals a t low temperatures, heat exchange, insulating materials, removal of carbon dioxide from the natural gas, special valves, analytical recorders, and methods of obtaining the necessary refrigeration. Another important function of the laboratory was the continuance of the investigation started in 1917 to find more de-
was to be expected. The early equipment proved, however, that the production of helium in commercial quantities was a possibility, and after the war the Government elected to continue the activity. The decision to produce helium on a large scale was reached before the Armistice was signed, and a t the end of the war the Government was preparing to construct a large plant a t Fort Worth for the extraction of helium from natural gas produced in the Petrolia, Texas, gas field. That plant was constructed under the jurisdiction of the Navy and employed the process developed by the Linde Air Products Company in the experimental program that had been conducted bv the Bureau
849
850
INDUSTRIAL AND ENGINEERING CHEMISTRY
pendable sources of helium. Even in the early days of the project, it was known that the Petrolia Field would not provide a long-time supply of helium-bearing gas. Early estimates indicated that by 1929 that field would cease to be an economical source of supply, a prediction that was borne out almost to the day. By 1925 data that had been furnished through the bureau's Cryogenic Laboratory were being applied, and bureau engineers had designed and constructed three purification plants, two for the Army and one for the Navy. It is evident that helium in a balloon or dirigible will diffuse outward through its containing envelope of specially treated cloth. It is not so apparent, but nevertheless true, that air will diffuse inward through the balloon covering and dilute the helium. The purification plants were for the purpose of treating helium that had been in use for some time and through diffusion had become contaminated with undesirable quantities of atmospheric air. The purification plants constructed by the bureau were highly successful and their operation was relatively inexpensive. In 1925, perhaps as a result of the bureau's store of engineering data on the subject of helium and the success it attained in applying them, Congress placed all of the Government's helium-production activities in the Bureau of Mines, where they have remained until the present time. The bureau, therefore, had charge of the operation of the Fort Worth helium plant from July, 1925, throughout the remainder of its productive life. By 1927 it was clearly evident that the Petrolia Field could not meet the requirements for helium production much longer. Meanwhile, however, as a result of the bureau's investigations, a desirable area for production of helium-bearing natural gas had been found in the Panhandle of Texas. This area, lying about 18 miles northwest of Amarillo and known as the Cliffside Field, produces natural gas under a pressure of 700 pounds per square inch, with a helium content of 1.75 per c mt. The gas from Petrolia Field contained approximately 1 per cent of helium. An important factor favoring the CliffsiJe Field was that little gas had been withdrawn from it, and the entire area, comprising about 50,000 acres, was owned or controlled in large blocks by four interests; therefore acquisition of gas rights was not as difficult as it would have been in a field of more diversified ownership. As the result of negotiations conducted by the Bureau of Mines, the Govern-
VOL. 30, NO. 8
ment now owns the gas rights in fee in the entire gas-bearing structure of the Cliffside Field. The purchase was made after careful examination by competent geologists, who estimated conservatively that the field contains enough helium to last the Government more than 100 years a t the average rate of withdrawal that has prevailed in the past. By reason of the complete ownership, gas is removed from the field only as needed for its helium content. By the time gas from the Cliffside Field became available for processing, satisfactory data had been developed, and money had been made available by Congress for Bureau of Mines engineers to design a new plant for the extraction of helium from natural gas. A site was chosen 7.5 miles west of Amarillo, and a welded 6-inch pipe line was laid from this site to the gas field. Construction of the plant, with buildings of a permanent type, began in August, 1928, and by April, 1929, helium was being produced.
Steps in the Process The first step in the process of helium extraction is the removal of a small quantity of carbon dioxide contained in the Cliffside gas. This carbon dioxide composes only about 0.5 per cent of the volume of the untreated gas, but the total weight of the carbon dioxide removed is more than a ton per day. It would not take a large quantity of carbon dioxide in the solid state to plug the small tubes used in parts of the equipment. The carbon dioxide is removed from the incoming gas by a scrubbing operation, which employs a solution of sodium hydroxide. The chemical reaction that removes the carbon dioxide from the natural gas changes the solution of sodium hydroxide to sodium carbonate. The sodium carbonate is reclaimed later by the addition of lime, and the resulting calcium carbonate is removed by filtration. The removal of the carbon dioxide is effected a t the pipe-line pressure of about 650 pounds per square inch. By means of countercurrent heat exchangers the natural gas, free from carbon dioxide, is cooled progressively to about - 185" C. At that temperature and under a pressure of about 300 pounds per square inch, all of the constituents of the natural gas, except the helium and a small amount of nitrogen, are liquefied. The liquids are withdrawn from the apparatus, sent back through the heat exchangers, and warmed to room temperature by the incoming gas. The residue gas is dis-
SPECIALLY DESIGNED NAVYSTEELTANKCARSFOR TRANSPORTATION OF HELIUM GAS,STANDINQ ON THE SPURTRACK OF THE IJ. S. BUREAU OF MINES AMARILLO HELIUM PLANT The helium is contained under preasure of 2000 pounds per square inch and will occupy, when expanded t o atmospheric conditions, about 200,000 cubia feet
AUGUST, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
85 1
than $200,000, the average net operating cost has been a little charged from the plant and sold to a local gas company. The less than $9 per thousand cubic feet. During several montk s helium which has remained in the gaseous state throughout of high production the cost on the net basis was below $5 per the operation, is withdrawn from the top of the equipment for thousand cubic feet, and this figure could be maintained, in all further purification. probability, if the demand for helium were large enough. T h e initial refrigeration, and that needed to continue The cost figures mentioned in this and the preceding parathe process, is produced primarily by means of an expangraph represent costs of operation and maintenance only; sion-engine cycle. Nitrogen that has been separated from that is, they do not include charges for depreciation, deplethe natural gas is compressed to about 600 pounds per square tion, or interest on invested capital. inch and expanded through the engine. This engine runs In 1927 and 1928, when the Bureau of Mines was acquiring a n electric generator which Drovides a means for the removal of
