228 



cox. 



DISCUSSION. 



Meade'^" has shown by three experiments that the changes between 

 the clinker as analyzed, when calculated without its water and carbon 

 dioxide^ and the raw material calculated to a clinker are as follows : 



Table XIV. — Lous or gain. 

 [The numbers give percentages.] 



Constituent. 



SiOo- 



TiOn. 



AloOs 



Fe»0;j 



FeO. 



MnO 



CaO. 



MgO. 



Na»0 



K.O- 



PoOo . 



SO3- 



+0.46 

 ■-0.02 

 H-0.41 

 +0.26 

 — AU. 

 —0. 01 

 -0. 20 

 +0.05 

 -0.06 

 —0.44 

 -0.02 

 -0.43 



+0.72 

 -0.03 

 +0.32 

 +0.30 



-An. 



HO. 09 

 -0.08 

 -0.12 

 — 0. ijl 

 +0.01 

 —0.72 



+0.67 

 -0. 03 



H-0.39 

 +0.32 

 -All. 

 0.00 

 -i-O. OS 

 HO. 03 

 -0.09 

 -0.51 

 -0.00 

 -0.87 



Average. 



+0.62 

 -0.03 

 HO. 37 



+0.29 



0.00 



0.00 



0.00 



-0.09 



-0.49 



0.00 



-0.67 



The results show that there is almost complete oxidation of the iron 

 present in the raw state, that over one-half of the alkalies are expelled 

 in the kiln, and especially that there is a large loss of sulphur and 

 almost complete oxidation of the remainder. The greater part of the 

 sulphur is present as iron sulphide in the coal and the original rock 

 which, when heated to the temperature of the kiln, burns to sulphur 

 dioxide and ferric oxide. It is quite probable that in the coal ash as 

 obtained in the laboratory all of the sulphur is fLxed by being roasted 

 to sulphates which do not give off sulphiiric anhydride at a gentle heat. 

 At kiln temperatures sulphuric anhydride would be partially expelled 

 from these and for this reason we would expect a loss of sulphur. As 

 regards sulphur, then, even the Philippine coals containing the highest 

 j)ercentage that I have found would be available for burning cement. 



Meade shows that the silica, ferric oxide and alumina of the clinlver 

 have been increased by approximately one-half of the coal ash. On the 

 other hand, he finds a marked loss of material in the dust, which the 

 analyses indicates to be a mixture of coal ash, partially burned raw 

 material and the volatile constituents of the latter. The figures show 

 that theoretically 354 kilos of rock should make a barrel of cement (172 

 kilos), but that few manufacturers use less than 276 kilos, showing a 

 loss of 12 kilos as dust, etc., per barrel of cement produced. Mr. Meade 

 further says : 



"Undoubtedly in the rotary kiln mucli of the ash is carried out with the gases 

 by the strong draft of tlie kiln. This we would expect to be the case when we 



■'Chem. Eng. (1905). 2, 222-223. 



