356 ILLINOIS STATE ACADEMY OF SCIENCE 



Let US assume, by way of illustration, that in the case 

 of an average Illinois coal, we have an amount of this 

 potential heat equal to 4 per cent of the total heat of the 

 coal, or approximately 500 B.t.u. per pound. Now, if 

 we can drop a mass of coal into a retort whose walls are 

 heated to 750 deg. C. (1382 deg. F.) and start off the 

 exothermic reactions in such a manner that they will 

 become autogenous, they will, of course, pass beyond 

 the outer zone of heat furnished from the walls of the 

 oven and proceed to the center of the mass regardless 

 of either the heat head at the surface or the insulating 

 property of the mass. 



In the illustration here shown, these conditions have 

 been secured. Note particularly that a narrow zone at 

 the outer rim shows a coke formation which has been 

 due to the direct application of heat from the walls of 

 the retort. Beyond this zone and thus soon out of reach 

 of the exterior heat, the reactions became autogenous 

 and quickly penetrate to the center. Naturally also we 

 would expect that in order to travel alone, they must 

 have at least slight surplus of heat at every stage of 

 progress inward, which would thus be cumulative in ef- 

 fect and to the end of the process would show a higher 

 temperature at the center of the mass than at any other 

 point. This correctly represents the uniform condi- 

 tion at the termination of an experiment. Incidentally, 

 it is interesting to note not only the texture and cell 

 structure peculiar to the carbonization that occurs under 

 these conditions, but also that the sample at the left is 

 from an Illinois coal with the high oxygen value as 

 already shovni in the chart, while the sample at the right 

 is from a high volatile eastern coal which would at once 

 be placed among the coking coals because of its low 

 oxygen content. The texture, strength, density, etc., of 

 the two examples seem to be very much alike. 



The question will at once arise in your minds as to 

 why this effect is not secured in the regular byproduct 

 coke oven. The wall temperature starts the coal at even 

 a higher stage, say 1000 deg. C. (1832 deg. F.), while 

 we are using from 700 to 800 deg. at the start. Why 

 do not the exothermic reactions occur and travel autog- 



