RECOVERY OF POTASH IN THE BLAST-FURNACE INDUSTRY. 6 
It is thus possible to determine the potash content of the charge 
used in a cement plant .from the analysis of a single representative 
sample. 
The burdens of blast furnaces, on the other hand, may change from 
time to time and often consist of different ores from widely separated 
sources, of limestone and dolomite obtained from various localities, 
and of cokes derived from different coal beds. The potash content of 
these several constituents may vary considerably and changes in 
the relative proportions of the constituents of the charge will cause 
corresponding variations in the potash content of the burden. The 
raw materials, moreover, are not uniformly mixed and ground before 
being charged into the furnace, and it is therefore not practicable 
to collect a single sample which would be representative of the charge 
as in the case of the cement industry. It is also possible in the latter 
industry to get fairly reliable data on the ratio of raw mix to ground 
clinker, but the weight of the blast-furnace charge to the slag obtained 
is subject to change and reliable data on the ratio of slag produced 
per ton of pig iron could not always be obtained. 
It was decided, therefore, to attack the problem by obtaining from 
their principal sources representative samples of the raw materials, 
iron ores, fuels, and fluxes, that are consumed in the blast-furnace 
industry. Knowing the annual consumption of these materials in 
this industry and their average potash content as determined by 
analysis it should be possible to calculate approximately the total 
amount of potash that is annually charged into the blast furnaces of 
the country. The potash in the slag varies in different furnaces and 
in the same furnace from time to time. By analyzing a large number 
of samples an average value can be obtained for their potash content. 
This value multiplied by the yearly output of slag and deducted 
from the total potash charged in the furnaces of the country will 
give the amount of potash that is annually lost by volatilization in 
this industry. 
REACTIONS WITHIN THE BLAST FURNACE. 
The blast furnace, in which the manufacture of pig iron is con- 
ducted, is a cylindrical steel shell which varies in height from 40 to 
100 feet or more. The diameter of the shell varies from top to bottom 
with the outlines adjusted for the various changes occurring in it. 
The walls of the hearth near the bottom of the furnace are pierced 
with openings through which a strong blast of heated air is forced 
to unite with the carbon of the fuel. The entire shell is lined with 
fire brick. 
Into the top of the furnace are charged continuously the ores, 
flux, and fuel which constitute the burden. The ore supplies the 
iron for which the furnace is operated, the fuel in combustion yields 
gases that reduce the iron to a metallic state and supplies the heat 
required for the reactions occurring within the furnace and for the 
fusion of the resultant iron and slag. The flux unites with various 
compounds which would otherwise be infusible at the temperature 
prevailing in the furnace and thus removes in a liquid state as slag 
the ash of the fuel as well as the earthy impurities occurring in the 
ore. The molten iron and slag collect in the hearth of the furnace 
