HKB
until it is completely desiccated, and the arrangement is such, that air-dried peat may be thrown in at the top, and the hot-dried fuel be removed at the bottom, continuously.
In the cut, A represents the section of a wooden cylinder about 10 feet wide and 6-1/2 feet deep, which surmounts a funnel of iron plate A'. The mouth of the funnel is closed by a door n; about 20 inches above the door the pipe B, which conducts hot air, terminates in the ring a a, through the holes in which, e e, it is distributed into the funnel filled with peat. The air is driven in by a blower, and is heated by circulating through a system of pipes, which are disposed in the chimney of a steam boiler. From time to time a quantity of dried peat is drawn off into the wagon D, which runs on rails, and a similar amount of undried peat is thrown in above.
According to Welkner, a kiln of the dimensions stated, which cost, about $1800 gold, is capable of desiccating daily ten tons of peat with 20 per cent. of water, using thereby 2000 cubic feet of air of a temperature of 212 deg. F. When the air is heated by a fire kept up exclusively for that purpose, 10 per cent. of the dried peat, or its equivalent, is consumed in the operation. At the Alexis Smelting Works, near Lingen, in Hanover, this peat kiln furnishes about half the fuel for a high furnace, in which bog iron ore is smelted. The drying costs but little, since half the requisite heat is obtained from the waste heat of the furnace itself.
The advantages of this drying kiln are, that it is cheap in construction and working; dries gradually and uniformly; occupies little ground, and runs without intermission.
Other drying ovens are described in Knapp's Lehrbuch der Chemischen Technologie*, 3. Aufl. Bd. 1, Theil 1, pp. 178-9; Jahrbuch der Bergakademien Schemnitz und *Leoben, 1860, p. 108, 1861, p. 55; Wagner's Jahresbericht der Chemischen Technologie, 1863, p. 748; Zerrenner's Metallurgische Gasfeuerung in Oesterreich; Tunner's Stabeisen- und Stahlbereitung, 2. Auflage, Bd. I, pp. 23-25.
When peat is charred, it yields a coal or coke which, being richer in carbon, is capable of giving an intenser heat than peat itself, in the same way that charcoal emits an intenser heat in its combustion than the wood from which it is made.
Peat coal has been and is employed to some extent in metallurgical processes, as a substitute for charcoal, and when properly prepared from good peat, is in no way inferior to the latter; is, in fact, better.
It is only, however, from peat which naturally dries to a hard and dense consistency, or which has been solidified on the principles of Challeton's and Weber's methods, that a coal can be made possessing the firmness necessary for furnace use. Fibrous peat, or that condensed by pressure, as in Exter's, Elsberg's, and the Lithuanian process, yields by coking or charring, a friable coal comparatively unsuited for heating purposes.
A peat which is dense as the result of proper mechanical treatment and slow drying, yields a very homogeneous and compact coal, superior to any wood charcoal, the best qualities weighing nearly twice as much per bushel.