16 



BULLETIN 1036, U. S. DEPAETMENT OF AGRICULTUEE. 



batteries of 50 or more, side by side, there is but little chance to 

 modify the method of heating. All of the ovens in this comitry, with 

 the exception of the Semet-Solvay oven, heat the coking chamber by 

 gas burned in vertical flues at the side of the chamber. The Semet- 

 Solvay oven heats the coking chamber by gas burned in horizontal 



flues. 



WATER-GAS TAR. 



Water-gas tar is produced in the manufacture of carbureted water 

 gas. This gas is produced in a machine loiown as a ''water-gas set." 

 It consists of tkree principal parts — a generator in which the true 

 water gas is produced; a carburetor consisting principally of checker 



Fig. 8.— Cross-sectioual view of Roppers coke ovens. 



brick on which petroleum oil is sprayed in order to render the water 

 gas of value for illuminating purposes; and a superheater, also of 

 checker brick, in which the gases formed in the carburetor are fixed 

 and made permanent. In operation the generator is filled to a 

 suitable level with coke or anthracite coal. This is rendered incan- 

 descent by blowing through it air imder pressure, the products of 

 combustion passing through the carburetor, where they meet a 

 secondary air supply and are completely burned in the carburetor 

 and superheater. The gases passing from the superheater are allowed 

 to escape in the stack and are lost, as they contain no material of 

 heating value, and are used to obtain the proper temperature in the 

 set. When the superheater and the rest of the water-gas set are of 

 the proper teitiperature, the blo\^dng is interrupted momentarily 

 until the valves leading to the gas holder can be opened and the 



