RECOVERY OF POTASH IN THE CEMENT INDUSTRY. H 



approximately to 75,000 tons annually. If, however, the dust 

 from all plants losing less than 1 pound of potash per barrel of 

 cement be considered as too low grade for use as a source of fertilizer 

 material and the figures from such plants be omitted in the calcula- 

 tions, then the value for the available recoverable potash in the ce- 

 ment industry of this country as normally operated becomes 71,000 

 tons annually. 



PERCENTAGE OF VOLATILIZATION OF POTASH IN CEMENT PLANTS. 



As shown in Table I, the proportion of the total potash (K 2 0) that is 

 volatilized varies in different plants from 24.5 to 95.9 per cent. The 

 lowest values were obtained for plants widely separated from one 

 another. In the Hudson River district the percentage volatilization 

 varies from about 30 per cent to 45 per cent, and in the Lehigh Valley 

 district from about 40 per cent to 60 per cent. In plants situated in 

 the northern Central States considerable variation was noted. The 

 highest values were found for plants located in southern California, 

 and in Colorado and Utah. 



It may be pointed out that as much variation occurs in the per- 

 centage of potash volatilized irom plants using oil as from those 

 using coal. It is also to be noted that the average percentage 

 volatilization (46 per cent) in plants using the wet process is almost 

 as great as that (47 per cent) in plants using the dry process, and 

 in fact the highest percentage volatilizations, 95.9 per cent and 

 90.7 per cent, were found for plants using the wet process. This 

 result is contrary to what seems to have been the general opinion 

 among cement manufacturers, as indicated by the following excerpts 

 from communications received from two firms using the wet process : 

 (a) "Our plant is a wet-process plant, and the amount of potash 

 which goes up in the air we figure is infinitesimal as compared with 

 plants using the dry process of manufacture." (b) "In our manu- 

 facture of Portland cement we use the wet method of grinding 

 our raw materials and in a short time I believe the entire cement 

 industry will depart from the present dry method and adopt the 

 wet method so that there will be no more precipitation of volatilized 

 potash in our smokestacks." 



That a smaller proportion of dust should be carried over mechanic- 

 ally in the wet-process plants is to be expected, and the loss of dust 

 should be particularly reduced in those plants in which the kilns 

 are provided with cross-partition plates which continuously raise the 

 wet slurry and allow it to fall again as a spray. Judging from the 

 observations that have been made in other industries, however, it is 

 not so apparent that the wet process should retard very greatly the 

 escape from the kilns of that portion of the potash which actually is 

 volatilized. 



