Tests of coke produced in the illuminating-gas investigations before referred to, and a study of commercial coking and by-product plants, are included in these investigations.
Briquetting Investigations.—These investigations are in charge of Mr. C. L. Wright, and are conducted in Building No. 32, which is of fire-proof construction, having a steel-skeleton frame work, reinforced-concrete floors, and 2-in. cement curtain walls, plastered on expanded-metal laths. In this building two briquetting machines are installed, one an English machine of the Johnson type, and the other a German lignite machine of very powerful construction.
The investigations include the possibility of making satisfactory commercial fuels from lignite or low-grade coals which do not stand shipment well, the benefiting of culm or slack coals which are wasted or sold at unremunerative prices, and the possibility of improving the efficiency of good coals. Some of the various forms of commercial briquettes, American and foreign, are shown in Fig. 2, [Plate XX]. After undergoing chemical analysis, the coal is elevated and fed to a storage bin, whence it is drawn through a chute to a hopper on the weighing scales. There it is mixed with varying percentages of different kinds of binding material, and the tests are conducted so as to ascertain the most suitable binder for each kind of fuel, which will produce the most durable and weather-proof briquette at least cost, and the minimum quantity necessary to produce a good, firm briquette. After weighing, the materials to be tested are run through the necessary grinding and pulverizing machines and are fed into the briquetting machines, whence the manufactured briquettes are delivered for loading or storage. The materials to be used in the German machine are also dried and cooled again.
Fig. 1.—Charging Floor of Gas Producer.
Fig. 2.—European and American Briquettes.
The briquettes made at this plant are then subjected to physical tests in order to determine their weathering qualities and their resistance to abrasion; extraction tests and chemical analyses are also made. Meanwhile other briquettes from the same lots are subjected to combustion tests for comparison with the same coal not briquetted. These tests are made in stationary boilers, in house-heating boilers, on locomotives, naval vessels, etc., and the results, both of the processes of manufacture, and of the tests, are published in various bulletins issued by the Geological Survey.[27]
The equipment includes storage bins for the raw coal, scales for weighing, machines for crushing or cracking the pitch, grinders, crushers, and disintegrators for reducing the coal to the desired fineness, heating and mixing apparatus, presses and moulds for forming the briquettes, a Schulz drier, and a cooling apparatus.