Tar Forming Temperatures of American Coals. 



Otto Cabtee Berry, Assistant Professor of Experimental Engineering 



The material presented in this paper is the result of a series of inves- 

 tigations started in the laboratories of the University of Wisconsin and 

 later continued at Purdue University. In form the paper is a brief of a 

 part of a bulletin of the University of Wisconsin published by the author 

 in 1914, with the addition of the results of the subsequent work. 



The nature of the volatile matter in bituminous coal is attracting con- 

 siderable attention at the present time. This is due not only to the enor- 

 mous amount of coal annually used in the United States, but also to the 

 important part volatile matter plays in determining how the coal must be 

 handled in order to obtain the best results. 



One of the most important and troublesome constituents of the vola- 

 tile matter is tar, especially when the coal must be used in boiler furnaces 

 or in power gas producers. 



The investigations to lie discussed in this paper had in view: (1) 

 the determination of the temperature limits between which tars are dis- 

 tilled from the various classes of coal; (2) the temperature limits of the 

 maximum rate of evolution of tars; (3) the relative quantities of tars 

 distilled from the various general classes of coal; and (4) the lowest tem- 

 perature at which one may be certain that the last trace of tar has been 

 driven off from the coal. 



Briefly stated, the results show that the temperature at which the first 

 trace of tar appears will range from about 20O°O. to about 385°C. usually 

 falling quite near 300°. The maximum deposit will start at a temperature 

 varying between 330° and 450°C. and will end between 430° and 530°C. 

 The last trace of tar will appear between 530° and 680°C. The amount of 

 tar produced seems to vary not so much with the amount of volatile mat- 

 ter in the coal as with the ratio of the carbon to the hydrogen as shown by 

 the ultimate analysis of the coal. 



When fresh coal is supplied to a furnace the volatile matter com- 

 mences to distill off and if properly mixed with air and burned there is no 



