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Effect of Pre-hydrolysis on Kraft Pulping of Kadam (anthocephalus Chinensis).

Dr. Daisy Biswas
Divisional Officer
Pulp and Paper Division, Bangladesh Forest Research Institute Sholashahar, P.O.- Amin Jute Mills Chittagong-4211.

Abstract/ Executive Summary:

Research has been carried out all over the world for improvement of pulping process concerning environmental aspect and economic benefits. In this study kadam (Anthocephalus chinensis) chips was hydrolysed with Na2CO₃ (3% based on OD chips) for an hour maintaining 140°C to reduce cooking chemicals and pulping time. The hydrolysate was removed and the chips were used for making kraft pulp. Three active alkali doses (14, 16 and 18%) on chips were used to obtain various levels of delignification. The pulping temperature was maintained at 170°C with the variation of pulping time for 45 min, 60 min and 90 min. It was found that with the increase of alkali doses and pulping time the kappa number reduced, simultaneously pulp yield was also lowered. Bleachable grade pulp can be obtained by pulping 45 min with 18% active alkali. At this condition pulp yield was 50%. Prehydrolysis prior pulping would save pulping time and cooking chemicals. The sheets from prehydrolysed kraft pulp were made and the physical strength properties likely tear, tensile and burst were evaluated. The pulp quality is slightly inferior compared to the untreated pulp. However this pulp could be useful for producing specialty paper-related products.Further research on the production of value added chemicals from hydrolysate and nano products from the pulp is recommended.

Keywords: Anthocephalus chinensis, Kraft pulping, Prehydrolysis, Sodium carbonate, Strength properties

Location: Bangladesh Forest Research Institute, Chittagong

Start Date: 01-07-2007

End Date: 30-06-2008

Program Area: Postharvest and Agro-processing

Commodity: Kadam

Objectives:

Pulping process improvement for increased pulp production

Methodology:

The kadam log were converted into the planks of size 7.6 cm X 7.6 cm length of the log and then chips were prepared. These were prehydrolysed by Na₂CO₃ amounting 3% based on OD chips at temperature 140°C.The liquor was drained after hydrolysis. The prehydrolysate contains a high amount of sugar. It may be valuable souece of ethanol and other valuable chemicals (Rath et. al. 2005). Such opportunities will be explored in future for maximum utilization of wood resources. The prehydrolysed chips were drained and washed with hot water for 15 minutes. The the chips were airdried.The air dried chips equivalent to 250 g oven dried were pulped in 2 liter stainless steel autoclaves in an electrically heated air bath. Analytical grades of Na2S and NaOH were used as cooking chemicals. The cooking conditions were as follows: - Liquor to wood ratio, 4:1, Cooking temperature, 170⁰C (Temperature increase from room temp. to 80⁰C in 30 minute and from 80⁰ to 170⁰C in 60 min.)- Cooking time, 45, 60 and 90 miniute- Sulphidity, 25% - Active alkali, (14, 16 and 18%) as NaOH for each cooking time. After cooking, the chips were discharged. Then the black liquor was collected. The cooked wood materials were washed overnight to make them free from residual liquor. After washing, the materials were disintegrated and screened. The screened pulp was passed on a screw press to remove the excess water, and then moisture content was determined. The pulp was then put into a sealed polythene bag and stored in a refrigerator for subsequent analysis.The yield and kappa number of pulps were determined as per SCAN Standard Methods. Selectivity is defined as a ratio between the amount of lignin removed over the amount of carbohydrate removed. To determine the selectivity ratio, the percentage of lignin and carbohydrate were determined according to TAPPI.The pulp samples were beaten in a PFI mill to different freeness values (SCAN-C 21:65) and hand sheets were made for determining strength properties. The sheets were then conditioned at 23⁰c and 50.1% relative humidity. The test samples were prepared and strength properties were determined according to SCAN-C 28:69.

Source of Information:

Article Link (Online Journal):

Funding Source:

1. Government

Budget: 300000

Total Budget (Tk.) : 300000

Achievement/Findings:

Pulp yield is higher than untreated pulp and production cost is lower.

Knowledge Management: Report/Proceedings