For manufacturing wood pulp Mr. Dresel employs an apparatus such as
represented in Figs. 1 and 2, consisting of an upright cylindrical
reservoir, A, supported on a frame by means of trunnions, z. This
reservoir, which is of boiler plate, is furnished with a cover, D, which
has in its center a piece of tubing, with stop-cock, C. A series of
tubes, R, whose diameter and length are proportioned to the volume of
the boiler, A, is filled with the liquid which is contained in the
boiler, so as always to be able to rapidly produce a pressure of nine
atmospheres or more by direct heating. The flanges of the tubing are
provided with a cut-off of angle iron identical with that of the tube,
D. By means of this arrangement the cocks and the flanges, E, permit of
communication between the serpentine tubing, R, and the boiler being
interrupted; while the heat developed by the fire-place, F, causes an
active circulation in both the tubing and boiler.
[Illustration: DRESEL'S WOOD PULP APPARATUS. Fig. 1]
[Illustration: DRESEL'S WOOD PULP APPARATUS. Fig. 2]
To put the apparatus in operation the cover, D, is first unscrewed, and
there is put into the boiler a certain quantity of wood, which has been
divided up by a cutting machine of special form. Then the boiler is
filled to the proper height with the liquid necessary to dissolve the
incrusting materials, the cocks, B, being closed. Afterwards there
is fixed immediately beneath the angle-iron ring of the cover, D, a
perforated iron plate upon which the contents of the boiler rest when
the latter is turned up. Then the cover is fastened down and the boiler
is put in communication with the heating apparatus. The cocks, E and B,
are opened, so that the liquid may begin its movement in the tube, a,
the boiler, A, and the tube, n. As soon as the proper temperature
is reached for converting the wood into fiber and decomposing the
incrusting matters, the heat is shut off in case the tubing, R, is not
connected with another like boiler, and, after closing the cocks, E and
B, and shut off communication between the tubing and the boiler, the
latter is turned over and the cock, C, gradually opened in order to
allow the steam to escape. When the temperature has descended to 100°
in the boiler the cover, D, may be opened, after the liquid has been
allowed to flow out through the cock, C. Next, lixiviation is effected
by connecting the cock, C, with the steam pipe, P, and causing steam
under pressure to enter the boiler, A. The action of the steam on the
contents of the latter, which are now converted into cellulose, mixed
with a large quantity of dissolved matters and of liquid, effects a
complete washing and permits of the recovery of considerable quantities
of useful chemical products. Moreover, the steam purifies, decolorizes,
and completely separates the fibers, and renders them more easily
susceptible of being bleached. Finally, the perforated bottom, S (which
is formed of two parts), is removed and the boiler emptied.
In order to have the operations under control, and for the purpose of
safety, there is riveted into the boiler, A, a tube, T, containing a
thermometer: and there is fixed to the tube, a, a pressure-gauge, M, and
a safety-valve. The level of the liquid is ascertained by means of a
gauge-cock, H.
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