Kshudiram Bhowmick,
Assistant Chemist (R&D).
Karnaphuly Paper Mills, Rangamati
A.J. Mian,
Professor
Chemistry Department,University of Dhaka
A.F.M. Akhtaruzzaman,
Divisional Officer
Pulp and Paper Division, Bangladesh Forest Research Institute, Chittagong, Bangladesh.
Melocanna baccifera, Anthraquinone, Kraft pulping, Pulp yield and strength properties.
Pulp and paper Division, Bangladesh Forest Research Institute
Postharvest and Agro-processing
Handling of Chips
Mill-cut muli-bamboo chips were collected from the Karnaphuli Paper Mills. They were washed with water to remove external adhering dirts. The chips were then air-dried for 15 days and hand sorted to remove the undersized and oversized chips as well as decayed bamboo. The chips passing 32 mm round hole screens, but retained on 6 mm round hole screens were the accepted. The chips were then bagged in air tight polythene container and the moisture content determined. Then the chips were stored in a cold storage at a temperature of 4°C for use in the experiments. The dry matter content of the chips was about 87 per cent.
Cooking
The pulping experiments were carried out in 2 litre stainless steel autoclaves with 6 autoclaves at a time in an assembly rotating in an air bath, the air being electrically heated. 300 g OD chips were added to each autoclaves. The cooking liquor was prepared from technical grades of sodium hydroxide and sodium sulphide. The white liquor was analyzed according to SCAN-N2: 63 Testing Method.
Pulping was done by kraft process with and without AQ. The effect of AQ on normal kraft pulping was studied by adding two doses of AQ, viz., 0.05 per cent and 0.10 per cent on OD chips. Other cooking conditions were:
Active alkali as NaOH, 18 per cent
Liquor to bamboo ratio, 4:1
Cooking temperature, 1700C
Rise of temperature from room temperature to 700C by 15 minutes and from 700C to 1700C by 90 minutes.
Total cooking time (excluding 15 min, for the rise to temperature to 700C), varying,
Sulphidity, 25 per cent.
Post cooking treatments
After cooking, the autoclaves were cooled rapidly with running water. Black liquor samples were then collected and cooked chips were washed overnight under running water. After washing the cooked chips were disintegrated in high speed laboratory disintegrator. The pulp was screened on a flat vibrating screen with 0.508 mm stots. The screened pulp was transferred into a thick cloth bag and dewatered by pressing in a screw press. The dewatered pulp was then well mixed mechanically. The screening rejects and a portion of screened pulp were dried to a constant weight (SCAN-C3:78) and the yield was determined. The pulp was stored in the cold storage in a sealed polythene bag for subsequent analysis.
Analyses
The black liquor was analyzed according to the Swedish method for the determination of residual alkali. The kappa number of the pulp was determined according to SCAN-C 1:59 and the viscosity of unbleached pulp with CED solution according to SCAN-C 15:62. The pulps were beaten in a Jakro mill beater to different Schopper-Riegler freeness (°SR) values. The(°SR) values were determined according to SCAN-C 19:65. The paper making properties of the hand sheets made from the pulps were evaluated using SCAN-C 28:69 Standard Test Methods after conditioning the sheets at 50 ±2% relative humidity and 23 ±1°C temperature. The strength properties of unbleached screened pulp were evaluated at 30 and 40 °SR by interpolation.
Four P News 3(5):10-14, 1991
Journal