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formed into a fine briquette without a bond. But the question of cost, of method and machinery requisite, and whether the material is briquettable in this way with profit, must be fully considered before any great expense is incurred.
After the first establishment of a manufactory for this character of fuel at St. Etienne, France, in 1842, it spread into England, Belgium, and elsewhere, and when the price of the bond was materially lessened, by the saving of the tar from the coke ovens, it gathered fresh headway, until at the present time factories are in operation in France, Belgium, Holland, England, Spain, Italy, Russia, Sweden, Germany, Austria, Hungary and the United States.
The present conditions of briquette technology are such that outside of peat, certain kinds of brown coal, and possibly caking coals, briquettes can not be manufactured without a bond of some kind, while by the use of such a bond all possible fuels may be converted into pressed coals and thus made serviceable.
QUALITIES OF BRIQUETTES.
Schwackhöfer gives the following as the qualities of good briquettes:
- a. They must be homogeneous, ringing, and nearly smokeless.
- b. The breakage in transportation must not exceed 5 per cent.
- c. The weight of each briquette should not exceed one to two and one-half pounds, so that they can be used handily and without breaking in feeding the furnace.
- d. The average specific gravity should be at least 1.15.
- e. They must not be hygroscopic. The moisture contained in them should not exceed 5 per cent, and the ash should not be more than 10 per cent.
- f. They must be easy to kindle, burn with a lively and practically smokeless flame, and must not fall to pieces in the fire.
- g. Their steaming power must be approximately equal to that of a good steam coal.
For certain purposes, however, such as use in locomotives or in ships' furnaces, larger sizes are made, reaching in the French marine to briquettes weighing twenty-two pounds each, and even a greater size. The limits of water and ash are also changed under certain conditions, but the water and ash together should never exceed the maximum here given.