50 CHEMICAL FERTILIZERS 



and part of the hydrogen sulphide and carbon dioxide, are 

 washed out of the gas. The ammonia liquor collected from 

 these scrubbers, together with that condensed in the 

 hydraulic main, is drained away into storage tanks, from 

 which it is withdrawn from time to time, to suit the needs 

 of the manufacture of ammonium sulphate or other ammonia 

 compounds which are described on pp. 83 and 89. 



When coal is distilled with the object of producing 

 coke, a different quality of coal is frequently used to that 

 which would be suitable for the manufacture of illuminating 

 gas. As it is very necessary that the amount of mineral 

 matter should be reduced, coals are sometimes ground up 

 in mills, and then washed. The washed coal is deposited 

 in special drums and then transferred to a stamping machine, 

 which makes a cake of suitable size for loading into the 

 ovens. The ovens are heated by flues externally. As a 

 rule the coal, whether in washed cakes or in the original 

 lumps, is fed slowly into the top of the horizontal retort, 

 the finished coke being driven out by a ram. The gases 

 evolved are drawn through scrubbers, which wash out the 

 ammonia. In coke works the methods are very similar to 

 those adopted in gas works, the chief difference being due 

 to the nature of the ultimate products. In the patent 

 recovery oven, the quantity of coal dealt with in a charge 

 is as much as 6 tons ; very much larger than that in a 

 gasworks. The temperature of carbonization is probably 

 higher in coke ovens than in gas retorts, but as the gas is of 

 less importance, the precautions needed to prevent admission 

 of air by leakage are regarded less seriously. The common 

 type of oven in general use is a rectangular chamber, which 

 is fired by gas burnt in large Bunsen burners, the gas used 

 being that produced by the ovens themselves. The gases 

 are led off by an ascension pipe into the gas main through 

 exhaust fans, drawn through air and water coolers, and 

 then forced through scrubbers as described above for 

 illuminating gas works. The gas is then returned to the 

 oven for the purpose of providing the heat necessary for 

 distillation. 



