Hemp Hurds as Paper-Making MaterialDewey, Lyster H. (Lyster Hoxie)
Science
Hemp Hurds as Paper-Making Material
Dewey, Lyster H. (Lyster Hoxie)
Fiber plants; Hemp; Paper industry
In comparing the method of using hurds with the method of handling
poplar wood, a difference is apparent on the delivery of raw material at
the mill. Ordinarily, poplar is received at the mill in the form of logs
about 4 feet in length, which may be stored in piles in the open. Hurds
very likely would be received baled, and it would seem advisable to
store them under cover for the following reasons: (_a_) Baled hurds
would probably absorb and retain more water during wet weather than logs
of wood, thereby causing excessive dilution of the caustic liquor; (_b_)
prolonged excessive dampness might create heating and deterioration
unless the hemp were properly retted; (_c_) wet hurds could not be
sieved free from sand and chaff. Should further work show that the first
two reasons need not be taken into consideration, the third objection
might be overcome by sieving the hurds before baling. Even then, it is
probable that baled hurds stored in the open would accumulate and retain
considerable dirt from factory chimneys, locomotives, and wind. Checked
pulp wood exposed in the open invariably suffers from these causes.
In the preparation of the raw material for the digesters there is
likewise considerable difference between hurds and poplar wood. The
former apparently requires only a moderate sieving to remove sand and
chaff, which operation doubtless would require only a small amount of
labor and the installation of some simple machinery of low power
consumption. In preparing poplar for digestion, the 4-foot logs are
chipped by a heavy, comparatively expensive chipper of high power
consumption, after which the chips are sorted by sieving, the large
pieces being rechipped. There would be a noteworthy difference in the
installation, operating, and depreciation costs of the two equipments,
and this difference would counterbalance to a considerable extent the
difference in cost of raw material storage.
It is possible that in the use of the chip loft more care would have to
be exercised in using hurds because of the tendency of the bast fiber to
cause lodgments, but this should not be considered a serious difficulty.
The weight of hurds which are capable of being charged into a rotary is
a decidedly unfavorable factor. The weight of a cubic foot of hurds
varies somewhat with the proportion of bast fiber, but averages about
5.4 pounds, which, compared with a cubic foot of poplar chips at 8.93
pounds, represents a digester charge of 60.5 per cent of the weight of
a poplar-wood charge, or, in terms of fiber capacity, the hurds charge
would yield 38.6 per cent as much fiber as the wood charge. The hurds
upon being baled for transportation may be broken and crushed to such a
degree that the weight of the charge may be increased, and it might be
found possible to increase the charge weight by steaming or by the
employment of tamping devices. This small weight of charge constitutes
one of the most serious objections to the use of hurds in paper
manufacture.
Public-domain text, read in full here on John Shaqi.
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