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 those tests in which the most satisfactory results were obtained, the
cooking conditions were 29.5 per cent of caustic soda at a concentration
of 107 grams per liter and a causticity of 84.0 per cent acting at a
temperature of 170 deg. C. for five hours, or a total time of seven hours.
The steam condensation in the rotary used for these tests was abnormally
high, due to the fact that the steam supply pipe was uncovered for a
considerable distance and the rotary was entirely uncovered. It is
believed, therefore, that a larger amount of caustic was necessary than
would otherwise have been the case. This belief is strengthened by the
quality of the waste liquor from one of the later cooks, which gave on
analysis 16.85 grams per liter of free caustic soda and showed a
causticity of 27.75 per cent. These data show that only 67.3 per cent of
the total caustic employed was actually consumed in the cooking
operation, which percentage is lower than obtains in practice. The stock
from this cook was bleached with 11.5 per cent of bleach. But even as
the figures stand, the comparison with poplar cooking practice is as
follows: 29.5 per cent caustic soda used as against 22 to 25 per cent;
107 grams per liter as against 100 to 110; 84 per cent causticity is
little different than obtains in practice; 170 deg. C. is about commercial
practice; five hours at pressure as against four to six hours; seven
hours' total time as against possibly six to eight hours; 11.5 per cent
bleach as against 8 to 10 per cent. Thus, it is evident that the cooking
conditions employed were slightly more severe and expensive than those
in commercial use with poplar wood.
The yield of total fiber obtained from the hurds may be placed at 35 per
cent of bone-dry fiber calculated on the bone-dry weight of hurds used,
or 33.1 per cent of air-dry fiber calculated on air-dry hurds. The yield
of bleached fiber was not determined in this preliminary work, but may
be safely estimated as 30 per cent, which is low when compared with a
yield of about 47 per cent of bone-dry bleached fiber from bone-dry
poplar wood. It is believed quite possible that satisfactory cooking
conditions may be found which will give a higher yield than was obtained
during these tests. The stock should be classed as easy bleaching, and
11.4 per cent of bleach is a satisfactory figure, although a little
high.
As to beating cost, in the last two and most satisfactory tests the
total washing and beating time was three hours, which may be about an
hour more than ordinarily is used in making papers of this grade,
although the practice varies to a considerable extent.
In regard to furnish, there is such a diversity of practice that it is
difficult to make a comparison, but if the hurd stock can be produced as
cheaply as soda-poplar stock, the furnish used in these last two tests
should be regarded as satisfactory to the book and printing paper
manufacturer.
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