FIXATION OF ATMOSPHERIC NITROGEN 401 



A still larger water-power installation established in Southern 

 Norway derives its water supply from three lakes, Maarvand, 

 Mosvand, and Tinnsjo. The two former drain through the river 

 Maan into the upper end of Tinnsjo. The last-named lake has a 

 capacity of 168 million cubic metres, and is 190 metres above 

 the sea. The principal power houses are at Rjukan, below 

 Mosvand and above lake Tinnsjo, the water being brought in 

 ten steel tubes. Two other power houses lower down on the 

 same stream at Lienfos and Svaelgfos supply the nitrate works 

 at Notodden. When these and other factories contemplated 

 in this district are completed about 540,000 horse-power will be 

 employed. 



Nitrolime or Calcium Cyanamide 



The production of this substance depends on the combination 

 of calcium carbide with nitrogen gas under the influence of a 

 moderately high temperature, produced by an electric current 

 passing through carbon resistances embedded in the mass. 

 CaC 2 +N 2 =CaNCN+C. 



The first stage in the series of operations is the production of 

 calcium carbide. At Odda this is the business of the Alby 

 United Carbide Factories, Limited. The materials employed are 

 lime made from Norwegian limestone as free as possible from 

 impurities, and carbon in the form of Welsh anthracite. When 

 these materials, mixed together in proper proportions, are heated 

 in electric furnaces to a temperature approaching 3000 C. 

 (5432 F.), a reaction ensues in which, after expulsion of a small 

 quantity of gas given off by the anthracite, the carbon unites 

 with the oxygen of the lime forming carbonic oxide gas, and 

 with the calcium, forming calcium carbide, which, with the small 

 quantity (3 p.c.) of ash left by the coal and a small quantity of 

 coke, constitutes the solid residue : 



CaO+3C=CaC 2 +CO. 



The lime required is made in five kilns each of 30 tons capacity 

 heated by producer gas. Four of these are sufficient to supply 

 the twelve electric furnaces in which the carbide is produced, so 

 that one of the kilns is a standby. 



The separation of the requisite nitrogen from the atmosphere 

 by the Linde liquefaction process has already been described 

 (see Nitrogen, p. 251), and we may, therefore, now proceed to 

 examine the operations involved in the production of cyanamide. 



2D 



