48 THE IRON ORE DISTRICT OF EAST TEXAS. 



to serve as a cement for the coal particles when under a pressure from one 

 thousand to fifteen hundred atmospheres. The bitumen already prepared 

 during the drying process is molten under this enormous pressure, and in 

 this state cements the coal particles. As the contents of bitumen and water 

 are very different in the lignites, the manufacture of briquettes requires a 

 great deal of attention, and the oven as well as the press must be adapted to 

 the physical and chemical properties of the coal in order to afford a good 

 commercial article. 



The process of the manufacture of briquettes consists of the following 

 manipulations: The lignites are crushed into small fragments and fall from 

 the crusher into the collecting room, where they are received by a slow re- 

 volving roller provided with ribs, and thrown through apertures below upon 

 a sifter placed in an oblique position. By a very simple but ingenious con- 

 trivance an upward and downward as well as a forward and backward mo- 

 tion of this apparatus is effected at the same time, and consequently the coal 

 is thrown over it with a springing motion. The smaller fragments of uni- 

 form size which have passed during this process through the meshes of the 

 sifter fall upon an elevator and are transported to the coal room above the 

 drying oven. The coal is here collected in larger quantities, so that the dry- 

 ing process can be prosecuted night and day, Sunday and holiday, without 

 interruption. Only with a continuous operation can the highest results be 

 effected. 



DRYING THE LIGNITES. 



The most difficult part in the manufacture of briquettes, as mentioned be- 

 fore, is the drying of the lignites. A "coal rich in bitumen needs less water 

 than one poor in hydro-carbons, but no rule has been laid down to fix the 

 amount of water necessary for the different varieties, though it is generally 

 considered that lignites containing from fifteen to twenty per cent of water 

 are ready for the press. The process is not alone intended to evaporate the 

 superfluous water, frequently from thirty to forty per cent, but also to equally 

 dissolve and distribute the bitumen throughout the coal. 



By a very early method the drying of brown coal to be used for smelting 

 purposes was effected in chambers placed on both sides of a long and small 

 building, leaving a passage between them. Only one of the smaller sides of 

 the building communicated with the air, where a furnace of considerable ca- 

 pacity was located, from which constantly hot vapors were conducted in tubes 

 through the passage to the chimney. The heated air of the building was then 

 forced by a fan placed on the opposite side into the chambers filled with the 

 coal. 



Improvements followed upon improvements, and in 1878 a method was 

 patented in which the introduction of drums formed an entirely new part. 



