ISBN : 978-602-17761-0-0
103
© 2013 Published by Center for Pulp and Paper through REPTech2012
Pulp Yield and Hexenuronic Acid Content in Pre-hydrolysis Polysulide-anthraquinone Cooking of Plantation Hardwood
Kukjin Yoon
a
, Mitsuko Homma
a
, Keishi Tanifuji
a
, Hiroshi Ohi
a 1
, Keiichi Nakamata
b 2
a
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572 Japan,
1
oi.hiroshi.gmu.tsukuba.ac.jp
b
Hokuetsu Kisyu Paper Co., Ltd.,
2
k-nakamatahokuetsu-paper.co.jp
ABSTRACT
Bioreinery of plantation hardwood has lately attracted considerable attention. A process of pre-hydrolysis of wood chips for kraft cooking has been known as an improved process of kraft pulp yield or a process which
produces dissolving pulp under alkaline cooking conditions. The process of pre-hydrolysis kraft cooking becomes now the focus of attention together with acid sulite cooking as bioreinery, which can produce many
kinds of variable organic materials and chemicals including cellulose and bio-ethanol in the industrial scale. The hydrolysates from pre-hydrolysis process can be used as materials of bio-ethanol production. However, the process
may cause a yield loss of pulp in the kraft cooking process. The irst objective of this study is to clarify the optimal conditions of polysulide PS and anthraquinone AQ addition to kraft cooking for increasing pulp yields. The
second objective is to clarify the effects of both the pre-hydrolysis and the PS-AQ cooking on hexenuronic acid contents of pulps. The third objective is to discuss about reaction products in the pre-hydrolysis process. In this
paper, we report preliminary results for the irst and the second, especially hexenuronic acid contents of pulps. Keywords: bioreinery, pre-hydrolysis, polysulide, anthraquinone, pulp yield, hexenuronic acid
1. Introduction
Polysulide PS cooking with anthraquinone AQ compounds is the most promising technology
to increase pulp yields of kraft KP cooking. When the PS concentration can be higher, the pulp yield can
be increased more, and therefore there are several methods proposed for producing PS.
In industrialized technology available today, PS liquor is produced from sodium sulide Na
2
S by air oxidation of kraft white liquor WL in the presence
of catalyst, because a sulfur balance NaS balance in the KP process can be maintained. On the other hand,
The WL electrolysis, which is investigated and given as a process trial by Watanabe and others [1-2], is one
of new technologies to produce highly concentrated PS while maintaining the Na
2
S balance. In the previous papers [3,4], two kinds of rotational
cooking digesters were developed independently for laboratory experimental methods that enabled cooking
with a low liquor to wood ratio LW ratio of 2.5 mLg to simulate alkaline conditions of cooking liquor
in a mill continuous digester. The objectives of this study are irst to clarify
the beneits of PS-AQ cooking by analyzing the relationship between cooking results and dependent
variables of the cooking conditions.
2. Materials and Methods
We used woodchips prepared from Eucalyptus globulus wood in a laboratory. The chips were air-dried,
weighed, saturated with cooking liquor under vacuum, and then cooked. Cooking liquor was prepared with
NaOH and Na
2
S solutions and distilled water, and PS liquor was prepared by dissolving solid sulfur into
the Na
2
S solution. The PS liquor was prepared on the assumption of production by oxidization of a typical
WL, which contained about 110 gL active alkali as Na
2
O. The sulidity levels of WL were 20 or 40, and
the active alkali charge was 18 on o. d. wood. In the case of AQ addition, 0.05 on o. d. wood of SAQ 1,
4-dihydro-9, 10-dihydroxyanthracene sodium salts was charged to the liquor.
The conditions for cooking were as follows: temperature: 145°C, 165°C, LW ratio: 5.0 mLg, 2.75
mLg; cooking time: cooking time: 150min.
3. Result and Discussion 3.1 Effect of Liquor to Wood Ratio on Cooking
