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Potassium Hydroxide Pulping of Four Non-woods

S. Sutradhar
Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudrat-i-Khuda Road, Dhaka 1205, Bangladesh

M. Sarkar
China National Pulp and Paper Research Institute, Chaoyang District, Beijing, China

J. Nayeem
Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudrat-i-Khuda Road, Dhaka 1205, Bangladesh

M. Sarwar Jahan*
Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudrat-i-Khuda Road, Dhaka 1205, Bangladesh

C. Tian
China National Pulp and Paper Research Institute, Chaoyang District, Beijing, China

Abstract/ Executive Summary:

Four non-woods such as, dhaincha (Sesbania bispinosa), jute stick (Corchorus capsularis), wheat straw (Triticum aestivum) and corn stalks (Zea mays) were cooked by potassium hydroxide (KOH) at the optimum conditions of soda pulping. Dhaincha, wheat straw and corn stalks were delignified to kappa number 19.4, 13.6 and 19, respectively, while jute stick was not delignified sufficiently (kappa number 32.5). All these four raw materials maintained good yield in KOH process. Dhaincha produced the highest pulp yield (50.5%) and wheat straw had the lowest pulp yield (44.7). All pulps were bleached by D0EpD1 bleaching sequences in identical bleaching conditions. Final pulp brightness reached to above 80% ISO except jute stick pulp. Jute stick pulp reached to 74.9% brightness only after the consumption of 30 kg ClO₂/ ton of pulp. The overall bleaching yields were 92.6%, 88.4%, 90.1 and 90.8% for dhaincha, jute stick, wheat straw and corn stalks pulps, respectively. The OSR of these four non-wood bleached pulps was above 20, consequently improved paper making in the unrefined state. Beating rapidly increased paper making properties, as for example, the tensile index of dhaincha pulps increased from 49 N.m/g in the unrefined pulp to 90 N.m/g in the beaten 50 oSR. It can be seen that KOH is a good substitute to soda process for non-wood.

Keywords: Non-wood; Potassium hydroxide pulping; Bleaching; Beating; Papermaking properties

Location: Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudrat-i-Khuda Road, Dhaka 1205, Bangladesh

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Pulp

Objectives:

In this paper, four non-wood such as dhaincha, jute stick, wheat straw and corn stalks pulping was done with KOH. Pulps were bleached by D0EpD1 bleaching sequences and papermaking properties were evaluated.

Methodology:

Raw materials Four non-woods : dhaincha, jute stick, wheat straw and corn stalks were collected and cut to 2-3 cm in length. Thickness of jute stick and dhaincha was 2-3 mm in size. After determination of the moisture content of air dried raw materials equivalent to 300 gm o.d. (oven dried) was weighed separately in a polyethylene bag for subsequent cooking experiments. Pulping Pulping of dhaincha, jute stick, wheat straw and corn stalks was carried out by KOH process in an electrically heated 5 lit capacity digester. Active alkali charge was fixed at 16 % as NaOH on od raw materials. The following parameters were maintained: i) liquor to fiber ratio: 6:1 for wheat straw and corn stalk and 5:1 for jute stick and dhaincha, ii) temperature: 150 ^oC for wheat straw and corn stalk and 170 ^oC for jute stick and dhaincha, iii) Cooking time: 120 min at maximum temperature. After the desired time of cooking, pulp was filtered and black liquor was collected for subsequent experiment. Pulp was washed with tap water till the removal of all chemicals. The yield of the pulp was determined gravimetrically from the oven-dried weight of raw material. The kappa number of the resulting pulp was determined in accordance with Tappi Test Methods (T 236 om-99). D0EpD1 bleaching Pulps were bleached by D0EpD1 bleaching sequences (where D represents chlorine dioxide and Ep represents peroxide reinforced alkaline extraction). In the first stage (D0) of D0EpD1 bleaching sequences ClO2 was 2%. The temperature was 70^oC in D0 stage for 45 min. Pulp consistency was 10%. The pH was adjusted to 2.5 by adding dilute H₂SO₄. In the alkaline extraction stage, pulp was extracted with 2 % NaOH and 0.5% H₂O₂ (on od pulp) for 120 min at 70^oC. Pulp consistency was 10 %. The end pH in the D1 stage was adjusted to 4 on adding dilute NaOH. The ClO₂ charge in the D1 was 1%. The brightness was determined in accordance with Tappi Test Methods T525 om 92. Evaluation of pulps The bleached pulps obtained from dhaincha, jute stick, wheat straw, and corn stalks were beaten in a PFI mill in different revolutions and handsheets of about 60g/m² were made in a Rapid Kothen Sheet Making Machine. The papermaking properties determined were according to TAPPI Standard Test Methods. The sheets were tested for tensile (T 494 om-96), burst (T 403 om-97) and tear strength (T 414 om-98) according to TAPPI Standard Test Methods.

Source of Information: Bangladesh J. Sci. Ind. Res. 53(1), 1-6, 2018

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Dhaincha, wheat straw and corn stalks was delignified satisfactorily by KOH in the optimum cooking conditions of soda process on preserving the pulp yield. Dhaincha, wheat straw and corn stalks pulps were bleached to brightness above 80%. The overall bleaching yield of KOH pulps was 90-93%. But jute stick was not delignified as desired in applied cooking conditions, consequently showed poor bleachability and lower overall bleaching yield. A good papermaking properties were observed for these four non-wood bleached pulps. The obtained data show that potassium hydroxide (KOH) process could be considered as a promising alternative process for non-wood.

Knowledge Management: Journal