228 CHEMICAL MANUEES. 



The Carves, the Tamaris, the Terre Noire, and Bessege ovens, 

 producing together about 300 tons of coke per day, yield 6 tons of 

 tar and 2 to 2-5 tons of sulphate of ammonia. 



The advantages of recuperation become more and more evident, 

 and in spite of the expense which the installation of such plant 

 involves, many mine proprietors have not hesitated to build similar 



ovens. 



The working of a battery of four coke ovens entails a supple- 

 mentary staff to work the gas-extractor, and to keep in order and 

 clean the recuperation appliances. The cost of the Semet-Solvay 

 furnace, refractory masonry with lining, oven discharger, discharger 

 flue, water piping, etc., is £240 sterling. The extractor, pump, and 

 recuperation appliances cost £140 sterling. Each oven takes 5 

 tons of coke ; the operation lasts about twenty-four hours. The 

 Hoffmann Otto takes a charge of 5 to 6 tons. The use of these ovens 

 has extended very rapidly in France ; there are at present several 

 hundreds of them. The Hoffmann Otto are almost exclusively used 

 in Germany and Austria. The Semet-Solvay are used in Belgium, 

 in France, Great Britain, Germany and the United States. 



Recovery of Ammonia from Blast Furnaces. — The recovery of 

 the ammonia contained in the gas from blast furnaces is only 

 carried out in Scotland at Gartsherrie. The coal used is a non- 

 caking coal, which prevents previous conversion into coke. The 

 gases escaping from the furnace mouth pass through a series of 

 pipes into apparatus similar to those used in the gas manufacture, 

 followed by a series of scrubbers, fitted with perforated plates, 

 leaving the gas to pass alternatively on each side, whilst a thin 

 stream of water, constantly flowing, dissolves the entrained ammonia. 

 The liquid is repumped and sent back to the scrubbers, until suffi- 

 ciently saturated. The yields are on an average 0*9 to 1-36 of the 

 weight of the coal, which corresponds very nearly with the 

 amount of ammonia got by the Carves coke ovens. 



Becovery of Ammonia formed in Gas Producers. — Heating by 

 the gas obtained in the semi-distillation of coal is one of the 

 best processes now known. It suppresses various drawbacks 

 incidental to a great number of fires, and enables very high tem- 

 peratures to be obtained. In this distillation, as in all similar treat- 

 ment of coal, there is given off at the same time as the combustible 

 gases a rather important amount of ammonia. To give good results 

 the production of the gas is effected by alternating the two following 

 operations : — 



1. The vapour of superheated steam is directed on to coal, heated 



is 9 metres (say 30 feet) in length, by 1-70 metres (say 5 feet 8 inches) high, and 

 of a width, varying according to the quality of the coals to be treated, of 0-36 to 

 0-42 metres (say 14 to 17 inches). The air is heated to 200° to 300° C. (392° to 

 572° F.). 



