[stansfield-gilmore] carbonization OF LIGNITES 97 



Table III 



Calculated Composition of Residue on Carbonization 



Note: — The calorific values are taken from the curve for the regular series of tests. 



Commercial Significance of Results. 



Commercial methods for the carbonization of coal may be divided 

 into two classes, intermittent and continuous. In the intermittent 

 process coal is charged into a heated retort or oven, and the heating 

 is continued, usually from the outside, until all the charge has been 

 raised to the desired temperature and sufficiently carbonized. The 

 residue is then removed from the oven and quenched, and a fresh 

 charge inserted immediately whilst the oven is still hot. In the 

 continuous process the coal is fed into the top of a vertical or inclined 

 oven. The charge slowly passes down through the oven, becoming 

 gradually heated as it approaches and passes through a strongly 

 heated zone, then cooling off in the lower zone, and finally being 

 discharged from the bottom. The rate of charging at the top and 

 discharging from the bottom are so adjusted that the oven is always kept 

 filled. This latter process is at present responsible for only a small 

 percentage of the total world output of coke; but it appears to have 

 many advantages for the carbonization of lignite or other non-coking 

 coal. 



The portion of a charge which is adjacent to the heating walls 

 of an intermittent oven is rapidly heated to the temperature of the 

 oven, but, because coal is a poor conductor of heat, the inner portions 

 of the charge are only slowly heated. The whole charge is slowly 

 heated in the continuous process. Ease of operation calls for large 



