1918.] The N.Z. Journal of Science and Technology. 315 
disintegrate into fragments at a temperature below 900° C. (1,650° F.) ; 
(3) they must resist weather and water for considerable periods ; (4) they 
must resist the influence of steam at 150° C. (300° F.) ; (5) they must possess 
porosity to such a measure that after drying they absorb about 15 per 
cent, of water in twenty-five minutes’ soaking ; (6) the binding-medium, if 
any, must be relatively free of sulphur, phosphorus, arsenic, and other 
substances injurious to the quality of pig iron or steel; (7) the cost should 
be reasonable. 
Briquetting by Pressure alone. —In certain cases of iron-ore containing 
clay, notably at Kertsch (Russia) and Ilsede (Germany), briquettes are 
manufactured somewhat successfully by pressures of 4,000-5,600 lb. per 
square inch, but the process has not been successful in those cases where 
the ore contains no binding-material. By applying pressure slowly and in 
two separate stages, so that all air is driven out before the final pressure 
is applied, firm briquettes can be made from ore or flue-dust, but they are 
too dense, and will not resist heat even when pressures up to 14 tons per 
square inch have been exerted. The process offers no promise of success 
in ordinary cases. 
Briquetting by Pressure and Subsequent Fusing— The Grondal process 
is successfully used in Sweden on magnetic ore which is ground and 
concentrated. The briquettes are formed at moderate pressures* and 
heated in a highly oxidizing flame to 1,400° C.]' A hard and porous brick, 
quite suitable for the blast furnace, is produced, and it has the advantage 
that the Fe 3 0 4 has been converted to Fe 2 0 3 , which is more easily reducible, 
at any rate under blast-furnace conditions. The kiln used is of the gas- 
fired tunnel type. The cost of briquetting per ton runs to about 3s. in 
Sweden, but in recent installations in America higher costs, up to 8s. per 
ton, have resulted. The fuel used in the kiln (producer or blast-furnace 
gas is used) is equivalent to coal equal to 5 to 10 per cent, of the weight 
of briquettes produced. 
A similar process is in use in America for treating flue-dust for open- 
hearth furnace work, and is quite successful. A great point is that any 
sulphur is largely burnt out in these processes. 
Briquetting with Binding-mediums. —The hydraulic properties of flue- 
dust derived from contained lime, alumina, and soluble silica are utilized 
in the Schumacker process.J Magnesium chloride is usually added in 
small quantities (J per cent.), and a briquette formed with 10 per cent, 
of water at a pressure of about 3 tons per square inch, which is then 
air-hardened. The MgCl 2 acts merely as a catalytic agent, and other salts 
(CaCl 2 , FeS0 4 ) or acids (H 2 S0 4 , HC1) have been substituted on occasion. 
This is a satisfactory and cheap process, probably the cheapest of the true 
briquette processes, but only fresh flue-dust can be used, and great care 
is needed to produce satisfactory results. 
Schumacker has also proposed a process for briquetting ores by the 
addition of 8 per cent, of spathic ore (FeC0 3 ) and 4 per cent, of lime. 
The pressure used is 6,000 lb. per square inch, and the briquettes are then 
steamed for four to six hours at a pressure of 150 lb. The process is costly, 
and has been used for open-hearth purposes only. 
The Scoria process consists of adding 5 to 10 per cent, of granulated 
slag and 4 per cent, of lime to the ore or flue-dust. With flue-dust the 
* Probably about 3 tons per square inch.—S. H. J. 
f To enable reduction to be carried on by CO.— S. H. J. 
j The classification of the Schumacker process under this heading is dubious. 
The MgCl 2 is not a binding-medium.—S. H. J. 
