Gysser recommends to mould the peat for charring in the form of cylinders of 3 to 4 feet long, which, when dry, may be built up into a heap like wood.
A great variety of ovens or kilns have been constructed for coking peat.
At the Gun Factory of Oberndorf, in Wirtemberg, peat is charred in the kiln represented in the accompanying figure. The chamber is 9 feet high, and 5-1/2 feet in diameter. The oven proper, _b b_, is surrounded by a mantle of brick _a a_, and the space between, _c c_, is filled with sand. Each wall, as well as the space, is 15 inches in thickness, and the walls are connected by stones _d d_, at intervals of three feet. Above the sole of the kiln, are three series of air holes, made by imbedding old gun barrels in the walls. The door, which serves to empty the kiln, is a plate of cast iron, the sides of its frame are wider than the thickness of the wall, and by means of a board _e_, a box _m_ can be made in front of the door, which is filled with sand to prevent access of air. The peat is filled in through _i_, a channel being arranged across the bottom of the kiln, from the door _f_, for kindling. When the firing begins, the lowest air-holes and _i_ are open. When, through the lower gun barrels, the peat is seen to be ignited, these are corked, and those above are opened. When the smoke ceases to escape above, all the openings are closed, _m_, is filled with sand, _i_ is covered over with it, and the whole is left to cool. It requires about 8 to 9 days to finish the charring of a charge. Several kilns are kept in operation, so that the work proceeds uninterruptedly.
[Illustration: Fig. 23.--OBERNDORFER PEAT CHARRING KILN.]
[Illustration: Fig. 24.--WEBER'S CHARRING FURNACE.--TRANSVERSE SECTION.]
[Illustration: Fig. 25.--WEBER'S CHARRING FURNACE.--LONGITUDINAL SECTION.]
At Staltach, Weber prepares peat coal in a cylinder of sheet iron, which is surrounded by masonry. Below, it rests on a grating of stout wire. Above, it has a cover, that may be raised by a pulley and on one side is attached a small furnace, figure 24, the draught of which is kept up by means of a blower, or an exhauster, and the flame and hot gases from it, _which contain no excess of oxygen_, play upon the peat and decompose it, expelling its volatile portions without burning or wasting it in the slightest degree. The construction of the furnace, see fig. 24, is such, that the sticks of wood, which are employed for fuel, are supported at their ends on shoulders in the brick-work, and the draught enters the fire above instead of below. The wood is hereby completely consumed, and by regulating the supply of air at _a_ (fig. 25) by a sliding cover, and at _b_ by a register, the flame and current of air which enters the cylinder containing the peat, is intensely hot and accomplishes a rapid carbonization of the peat, but as before stated, does not burn it. In this furnace the wood, which is cut of uniform length, is itself the grate, since iron would melt or rapidly burn out; and the coals that fall are consumed by the air admitted through c. The hot gases which enter the cylinder filled with peat near its top, are distributed by pipes, and, passing off through the grating at the bottom, enter the surrounding brick mantle. Before reaching the exhaustor, however, they pass through a cooler in which a quantity of tar and pyroligneous acid is collected.