Characterization and Optimization of Soda-Anthraquinone Pulping of Teff Straw for Paper Making Process
No Thumbnail Available
Date
2019-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The aim of this research was to investigate the important features of teff straw and its utilization
in the pulp and paper industry via soda-anthraquinone pulping process. Morphological
characterization indicated that the average length of teff straw fibers (1230μm), average fibers
width (15.28μm), cell wall thickness (3.83μm), lumen diameter (21.28μm) and acceptable
derived indices of slenderness ratio (80.78), Runkle ratio (0.36), flexibility coefficient (138.7)
and wall rigidity coefficient (25) which were comparable to the most non-wood plants and
Eucalyptus. The chemical composition of teff straw showed that the cellulose content (39.4%),
hemicellulose (29.6%), lignin (14%), extractives (7.2%) and ash content (6.78%). It contained
lower lignin and higher hemicellulose contents than most of non-wood plants which reflected
that teff straw requires mild cooking conditions. For experimental design, Response Surface
Methodology/Central Composite Design was used to compare the effects of cooking temperature
(130, 140 and 150℃), cooking time (60, 90, and 120 minutes) and active alkali concentration
(10, 15, and 20%) on pulp yield and Kappa number. The results indicated that sodium hydroxide
concentration had a higher significant influence on both pulp yield and Kappa number followed
by cooking time and temperature respectively. Greater interaction effects (temperature-time,
temperature-active alkali concentration and time-alkali concentration) of factors were also seen
on pulp yield and Kappa number both positively and negatively. Over cooking, extended time
pulping and high active alkali concentration gave the lower pulp yield. The optimization results
of pulping processes gave the optimal operating condition of 13.76% active alkali at 145.13℃
for 71.5 minutes and 33.15% pulp yield (based on oven dried teff straw) of 25.85 Kappa number.
The paper hand sheets of 60 g/m
were prepared from the pulps produced at optimum conditions
and tested for its mechanical properties that showed breaking length (4294 m), tensile strength
(11.6 kN/m), tensile index (42.1 Nm/g), tear index (5.2 mN.m
2
/g) and burst index (1.41
kPa.m
2
2
/g), and porosity (19.5 se/100 air). The results indicated that the tested strength properties
were acceptable and make teff straw an alternative material for pulp and paper application.
Description
Keywords
Teff Straw, Soda-Anthraquinone, Characterization, Pulping, Paper Making Process