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Kinetics of Jute Pulping.

Dr. M. Shafi ,
Research Officer
Pulp and paper Division, Bangladesh Forest Research Institute, P. O. Box 273, Chittagong-4000, Bangladesh.

Dr. A.F.M. Akhtaruzzaman
Divisional Officer
Pulp and paper Division, Bangladesh Forest Research Institute, P. O. Box 273, Chittagong-4000, Bangladesh.

Dr. Abdul Jabbar Mian, Professor,
Profesor
University of Dhaka, Dhaka

Abstract/ Executive Summary:

The kinetics of neutral sulphite (NS), neutral sulphite anthraquinone (NS-AQ) and kraft pulping were studied. The results showed three distinct phases of delignification for each of the processes. The delignification rate constant was in the order of kraft NS-AQ NS. The first transition point between the initial and bulk phases, and the second transition point between the bulk and residual phases shifted towards a lower lignin content on addition of AQ in NS pulping. NS-AQ process yielded the highest amount of carbohydrates with the lowest consumption of Na₂SO₃. On the contrary, kraft process yielded the lowest amount of carbohydrates with the highest consumption of alkali Thus NS-AQ process offers better selectivity in pulping.

Keywords: Jute, Kraft pulping, Neutral sulphite pulping, Neutral sulphite anthraquinone pulping, Delignification

Location: Pulp and Paper Division, Bangladesh Forest Research Institute, Chittagong.

Start Date: 00-00-0000

End Date: 00-00-0000

Program Area: Postharvest and Agro-processing

Commodity: Jute

Objectives:

To assess the extent to which the pulping to be continued in neutral sulphite anthraquinone, neutral sulphite and kraft pulping of jute.

Methodology:

Air dried jute cutting from white-B jute (Corchorus capsularis), which is not normally used in jute mills, was used as the fibrous raw material. It was heavily contaminated with unretted scales. The bottom part of jute generally shows poor retting and as such, finds little use in the jute mills. The unretted scales were allowed to remain in the raw material, because it is not possible to remove them industrially with the present day technology. The jute cutting was chopped manually to 2-3 cm in length. Pulping: Pulping was done in 2 litre stainless steel autoclaves. The amount of samples used in each cook was 250g on oven-dry (od) basis. The cooking liquor for NS and NS-AQ was prepared with analytical grades of Na₂SO₃ and Na₂CO₃, and that for kraft with the technical grades of NaOH and Na₂S.The following cooking parameters were maintained: -A total alkali charge expressed as Na₂SO₃+ Na₂CO₃expressed as NaOH of 18% for NS and NS-AQ, and an active alkali charge of 18% and sulphidity of 25% for kraft.

- Alkali ratio 0.83

-Liquor to fibre ratio, 7:1.

Rise of temperature from room temperature to 70°C in 15 minutes and from 70°C to cooking temperature in 90 minutes.

- cooking temperature 170°C.

-AQ dose, 0.1% on od jute.

At the end of the digestion the autoclaves were immersed in a water bath. The spent liquor/black liquor was collected. The cooked material was then washed thoroughly and disintegrated. Screening was done on a flat vibratory screen. The screened pulp was then pressed to remove the excess water, shredded and weighed.

Analyses

The dry matter content and the yield were calculated. Kappa and chlorine number of screened pulp were determined .Spent liquor was analysed for residual Na₂SO₃. The black liquor was analyzed for residual active alkali.

Source of Information: Holzforschung. Vol. 47(6) 491-496, 1993.

Article Link (Online Journal):

Funding Source:

1. Government

Budget: 00

Total Budget (Tk.) : 00

Achievement/Findings:

Three phases of delignificationcould be distinguished in NS, NS-AQ and kraft pulping of jute. The delignification rate constant was in the order of kraft ?NS-AQ? NS, The first transition point between the initial and bulk phases and the second transition point between the bulk and residual phases shift towards lower lignin contents on addition of AQ in NS pulping.NS-AQ leads to the highest carbohydrate yield with the lowest consumption of sodium sulphite. On the contrary, kraft showed the lowest carbohydrate yield with the highest consumption of alkali.

Knowledge Management: Journal