250 



CHEMICAL MAXUEES. 



from combustion gases, which is the subject of the American patent 

 816,035 of 5 March, 1907. The hot gases from the combustion 

 products of coke ovens, etc., enter by a tube A into an apparatus con- 

 taining the tubes of a refrigerator B, and from there into a second 

 refrigerator D, by the pipe C. A pump G aspirates the cooled gas 

 from the refrigerator D by the pipe F, and propels them into the 

 tar separator H. The gases freed from tar return by the pipe I 

 into the refrigerator D, and from there by the pipe K into the re- 

 frigerator B. In the refrigerators B and D the gases are reheated 

 by the hot gases which enter by the pipe A and surround the 

 tubes. Prom there the gases pass through the pipe L into an acid 

 tower M, which is filled with coke or analogous matter, on which 

 a reservoir N delivers acid as a fine rain. The gases thus freed 

 from their ammonia pass through a pipe 0, into a refrigerator P, 

 and can then be used for different purposes. The ammonia ex- 

 tracted from the crude gas and combined with acid is absorbed in 

 the refrigerator D at the same time as the water. The liquid 

 separated in B and in D is evacuated by the pipe Q into the reser- 



Fig. 50. — American Plant for Recovery of Ammonia from Combustion Gases. 



voir B, and from there it is directed into a distilling apparatus S. 

 In that apparatus it is distilled by steam over milk of lime ; the 

 ammoniacal vapours pass by the pipe T into a saturation reseiToir 

 U, which is fed at the end of the pipe Y with liquid formed in the 

 acid tower M. The sulphate of ammonia which is deposited on the 

 bottom of the apparatus U is evacuated in a continuous manner by 

 the injector W. The residuary water from the still is conducted by 

 the pipe W, terminated in the form of a rose, into the chimney X, 

 the draught of which is stimulated by the fan Z. Sulphate of 

 ammonia obtained by the processes described is the only kind 

 used in agriculture. According to its percentage of moisture it con- 

 tains 20 to 21 per cent of ammonia, which corresponds to 77 to 93 •2 

 per cent of sulphate of ammonia, or of 16*5 to 19'8 per cent of 

 nitrogen. 



Crude Ammonia from Spent Oxide. — The material used to- 

 purify coal-gas also contains spent oxide, and furnishes a product 

 called crude ammonia {criid d' ammoniac). Although ammonia can 

 be extracted from it in the pure state by treating it like gas liquor, 

 generally it is simply concentrated 'by evaporation. A product is 



