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Alkaline Pulping of Paraserianthes Falcataria with Anthraquinone as an Additive

Mr. A. R. Chowdhury
Research Assistant
Pulp and paper Division, Bangladesh Forest Research Institute, P.O. Box 273, Chittagong 4000, Bangladesh

Abstract/ Executive Summary:

Paraserianthes falcataria is a hardwood species suitable for making good quality kraft pulp with a high yield. The species is used as a raw material in one of the pulp mills in Bangladesh using soda process. Consequently, the pulp yield and quality are poor. To overcome these drawbacks this study has been conducted.The study shows that anthraquinone (AQ) has a positive effect both is soda and kraft pulping of P. falcataria. AQ addition by 0.05% can reduce the alkali charge by 5 per cent points and increase the pulp yield by about 4 per cent points is soda pulping. The yield becomes equivalent to the kraft counterpart. The use of 0.15% AQ further increases the pulp yield to surpass the kraft. But the gain in yield, but not to the extent as in soda pulping. It is also observed that the pulp quality improves by the addition of AQ both in soda and kraft pulping. The soda-AQ pulp is almost equivalent to the kraft counterpart, with only 6% lower value in tearing strength at a particular tensile strength.

Keywords: Alkaline pulping , Paraserianthes falcataria , Anthraquinone, Physical strength properties

Location: Bangladesh Forest Research Institute, Chittagong.

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Aloe Vera

Objectives:

To investigate the effect of AQ (anthraquinone) on Paraserianthes falcataria especially to note the effect on the strength properties.

Methodology:

Paraserianthes falcataria wood, about 10 years old, was collected from the experimental plantation in the Bangladesh Forest Research Institute campus. The logs were debarked and chipped in a laboratory chipper machine. The chips were air dried and hand sorted to remove the undersized and oversized chips. The accepted chips were about 25 mm x 12 mm x 3 mm in dimensions.Pulping was done by kraft and soda processes with and without AQ in a 23 litre rotating digester using indirect steam. The digester was initially heated to a temperature of 80⁰C, and then air-dried chips equivalent to 2 kg OD chips were charged with the chemicals. The effect of AQ was studied by using two doses of AQ, viz., 0.05 and 0.15% on OD wood. The different points of delignification were obtained by varying the cooking time (the points were obtained in normal soda cooking by varying the alkali charge). Other cooking conditions were maintained at 14% active alkali as Na₂O (except normal soda), 25% sulphidity (for kraft), 4 : 1 liquor to wood ratio, 90 minutes to raise the temperature from 80°C to 170°C and cooking at 170⁰C.At the end of the digestion, the cooked chips were discharged, washed overnight under running water, disintegrated and then screened. The screened pulp was pressed to remove the excess water, shredded, weighed and sampled to determine the moisture content. The screening rejects were oven-dried. The pulp yield and kappa number were then determined. The pulp was beaten in a Valley beater machine to different freeness values and handsheets were made for determining the strength properties on conditioning the sheets at 23 ±1°C and 50 ±1% relative humidity. The pulp strength properties were determined according to SCAN Test Methods.

Source of Information: Bangladesh Journal of Forest Science Vol. 20 (1&2); 49-54, 1991.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Anthraquinone (AQ) gives positive effects in increasing pulp yield, reducing cooking time or alkali charge and improving the quality of the pulp in soda and kraft pulping of Paraserianthes falcataria. The effects are dramatic in soda pulping. An addition of AQ by 0.05% is sufficient to bring the benefits.

Knowledge Management: Journal