ANOTHER METHOD OF NITROGEN FIXATION
Just at the time when the Scandinavian experimenters were solving the problem of securing nitrogen from the air, other experimenters in Italy, operating along totally different lines, reached the same important result. The process employed by these investigators is known as the Frank and Caro process, and it bids fair to rival the Norwegian method as a commercial enterprise. The process is described as follows by an engineering correspondent of the London Times in the Engineering Supplement of that periodical for January 22, 1908:
"This process is based upon the absorption of nitrogen by calcium carbide, when this gas, in the pure form, is passed over the carbide heated to a temperature of 1,100 degrees centigrade in retorts of special form and design. The calcium carbide required as raw material for the cyanamide manufacture is produced in the usual manner by heating lime and coke to a temperature of 2,500 degrees centigrade in electric furnaces of the resistance type.
"The European patent rights of the Frank and Caro process have been purchased by the Societa Generale per la Cianamide of Rome, and the various subsidiary companies promoting the manufacture in Italy, France, Switzerland, Norway, and elsewhere, are working under arrangement with the parent company as regards sharing of profits.
"The first large installation of a plant for carrying out this process was erected at Piano d'Orta, in Central Italy, and was put into operation in December, 1905. The power for this factory is developed by an independent company, and is obtained by taking water from the river Pescara and leading it to a point above the generating station at Tramonti. A head of 90 feet, equivalent to 8,400 horse-power, is here made available for the industries of the district. The power of the cyanamide factory is transmitted a distance of 6-1/4 miles at 6,000 volts. An aluminum and chemical works are also dependent upon the same power station.
"The Piano d'Orta works contains six furnaces for the manufacture of cyanamide, each furnace containing five retorts for absorption of the nitrogen by the carbide. A retort is capable of working off three charges of 100 kilograms (220 pounds) of carbide per day of 24 hours, the weight of the charge increasing to 125 kilograms by the nitrogen absorbed. The present carbide consumption of the Piano d'Orta factory is, therefore, at the rate of about 3,000 tons per annum, and the output of calcium cyanamide is about 3,750 tons per annum. The company controlling the manufacture at Piano d'Orta is named the Societa Italiana per la Fabbricazione di Prodotti Azotati. Extensions of the factory at this place to a capacity of 10,000 tons per annum are already in progress. Another company is also planning the erection of similar works at Fiume and at Sebenico, on the eastern borders of the Adriatic Sea. The additional electric power required will be obtained by carrying out the second portion of the power development scheme on the river Pescara. A fall of 235 feet, equivalent to 22,000 horse-power, is available at the new power station, which is being erected at Piano d'Orta."
After stating that companies to operate the Frank and Caro process have been organized in France, in Switzerland, in Germany, in England, and in America,—the last-named plant being at Muscle Shoals, Tennessee River, in Northern Alabama—the writer continues:
"These facts prove that the manufacture of the new nitrogenous manure will soon be carried on in all the more important countries on both sides of the Atlantic. If the financial results come up to the promoter's expectations the industry in five years' time will have become one of considerable magnitude.
"A modification of the original process of some importance has been suggested by Polzeniusz. This chemist has found that the addition of fluorspar (CaF2) to the carbide reduces the temperature required for the absorption process by 400 degrees centigrade, while it also produces a less deliquescent finished material.
"As regards cost of manufacture, no very reliable figures are yet available, but the companies promoting the new manufacture are regulating their sale prices by those of the two rival artificial manures—ammonium sulphate and nitrate of soda. Calcium cyanamide is now being sold in Germany at 1s. to 1s. 6d. (25 to 37 cents) per unit of combined nitrogen cheaper than ammonium sulphate, and 3s. to 3s. 6d. (75 to 87 cents) per unit cheaper than nitrate of soda. Whether the manufacture will prove remunerative at this price of about £10 10s. ($102.50) per ton remains to be seen. It is evident that, as the raw material of the cyanamide manufacture (calcium carbide) costs at least £8 ($40) per ton to produce under the most favorable conditions, the margin of profit will not be large, and that very efficient management will be required to earn fair dividends on the capital sunk in the new industry.
"It must be noted, however, that the processes are new and are doubtless capable of improvement as experience is gained in working them; while, on the other hand, the competition of the two rival artificial manures is likely to diminish as the years pass on.
"The new industry is, therefore, likely to be a permanent addition to the list of electro-metallurgical processes. But for the present its success can only be expected in centres of very cheap water-power, as, for instance, in those localities where the electric horse-power year can be generated and transmitted to the cyanamide works at an inclusive cost of £2 ($10) or under."