So far as actual experience goes it has been found that a brick building, with double walls to promote coolness, with high narrow slits instead of windows, with ventilating holes along the bottom of the walls, having a high-pitched roof with overhanging eaves, and holes for ventilation well sheltered under the eaves, and with ventilators along the edge of the roof, is best suited to keep the coal in the condition most nearly approaching that of the freshly mined. The floor of the building should be preferably paved with brick on edge or flagstones; the doors should be large and kept open in damp weather, and closed when the weather is hot.
Some persons recommend sprinkling the coal occasionally during the hot weather, but it is much better to wet down the paving all around the building outside, and the exposed floor of the building, as well as the walls inside and outside, and let the moisture of the evaporation have its effect upon the coal. It will be found to be amply sufficient for the purpose.
It has been found long since that it is better to have coal sheds dark, as light assists greatly in impairing the fuel.
The best arrangement for a boiler room floor is to have a coal-bin, paved with stone flags, opening into the fire-room by a door, while the fire-room itself should be paved diagonally with brick, set on edge upon a concrete foundation, well rammed to within about three feet of the boiler front, and the remaining space should be floored with iron plates.
The coal should be wheeled from the bins and dumped upon these plates, never on the brick floor. These plates should be laid on an incline of about an inch toward the boilers, and it is well to have a trough or gutter, of about six inches in width, and having a depth of about one and a half inches cast in them, at the edge lying nearest the boilers, so that the water from the gauge-cock, drip-pipes, and that from wetting down the ashes may run into it and drain into a proper sewer-pipe laid under the flooring.
CHEMISTRY OF THE FURNACE.
A careful estimate by a Broadway Chemist of the contents or constituents of a ton of coal presents some interesting facts, not familiar certainly to unscientific minds. It is found that, besides gas, a ton of ordinary gas coal will yield 3,500 pounds of coke, twenty gallons of ammonia water and 140 pounds of coal tar. Now, destructive distillation of this amount of coal tar gives about seventy pounds of pitch, seventeen pounds of creosote, fourteen pounds of heavy oils, about nine and a half pounds of naphtha yellow, six and one-third pounds of naphthaline, four and three-fourth pounds of alizarine, two and a fourth pounds of solvent naphtha, one and a fifth pound of aniline, seventy-nine hundredths of a pound of toludine, forty-six hundredths of a pound of anthracine, and nine-tenths of a pound of toluches—from the last-named substance being obtained the new product, saccharine, said to be 230 times as sweet as the best cane sugar.
From an engineer’s standpoint the main constituents of all coal are carbon and hydrogen; in the natural state of coal these two are united and solid; their respective characters and modes of entering into combustion, are however essentially different. The hydrogen is convertable into heat only in the gaseous state; the carbon, on the contrary, is combustible only in the solid condition. It must be borne in mind that neither is combustible while they are united.
There are, however, other elements existing in coal in its natural state, and new ones are formed during burning or combustion as will be noted in the succeeding paragraphs.
For raising steam the process of combustion consists in disentangling, letting loose or evolving the different elements locked up in coal; the power employed in accomplishing this is heat. The chemical results of this consumption of the fuels may be divided into four stages or parts.