Upgrading Paper-grade Softwood Kraft Pulp to Dissolving Pulp by Cold Caustic Extraction

Cold caustic extraction has potential applications in the production of dissolving-grade pulps due to its ability to selectively remove hemicellulose from lignocellulosic materials. In this study,we demonstrate the conversion of paper-grade kraft pulp into dissolving pulp by a single-stage cold caustic extraction. Under the extraction conditions of 12 wt% NaOH lye,11% pulp consistency,a temperature of 35℃,and 2 h,a paper-grade softwood kraft pulp was purified to high-grade dissolving pulp with 97. 1% α-cellulose content,1. 2% pentosane content,and narrowed molecular weight distribution. The resulting extraction filtrate was concentrated by nano-filtration to obtain the hemicellulose content of 59. 0 g / L,while the permeate was a clear Na OH solution with 10. 9 wt% concentration. A process configuration was also proposed,integrating this cold caustic extraction process with existing pulp and paper production and multi-purpose utilization of the extraction filtrate.

泥炭记录的帕米尔高原晚全新世温度变化研究

近年来,“全新世温度谜题”已经受到全球古气候学者的广泛关注,为了解决这一谜题,需要在全球不同区域进行更多的全新世温度重建。帕米尔高原位于亚洲内陆核心区域,目前有关帕米尔高原全新世气候变化的研究相对较少,且已有的研究主要集中于相对湿度(或降水)变化的研究,而涉及温度变化的成果则相对较少。论文首先研究了表土碳同位素与气候因子之间的相关关系,结果显示帕米尔高原的δ^(13)C_(org)与温度正相关;进一步在7个AMS^(14)C测年数据的支持之下,基于175个泥炭δ^(13)C_(α-cellulose)分析,重建了帕米尔高原过去约5000 a的温度变化历史。结果发现:帕米尔高原晚全新世以来整体呈现波动升温趋势,约5000~3600 cal a BP阶段处于缓慢降温期;约3600~200 cal a BP处于波动升温期;驱动机制分析显示,约3600 cal a BP之前温度下降主要是夏季太阳辐射下降导致的,约3600 cal a BP之后温度上升是由温室气体辐射强迫增强导致的。

Variation of chemical characteristics and pulpability of dhaincha(Sesbania bispinosa)on location

Dhaincha(Sesbania bispinosa(Jacq.)Wight)is a crop generally cultivated for improving soil quality.Due to the lack of forest worldwide,alternative source of raw materials for cellulose industries is the main concern today.In this investigation,dhaincha samples of 21 accessions were collected from different districts of Bangladesh in order to study the variation of chemical characteristics and its pulpability.The lignin,pentosan andα-cellulose content were varied from 21 to 23%,16 to 18%and 38 to 43%,respectively.The highest and lowestα-cellulose contents were found in two location of Mymensingh district.There was no correlation was found among the districts.Therefore,pulping of dhaincha from selected seven districts was carried out in kraft process at the conditions of 18%active alkali at 170℃ for 2 h.But the pulping properties did not show any mentionable distinction for place variation.Average pulp yield is 42.9%with kappa number 11.The highest brightness 85%was reached with D_(0)E_(p)D_(1)bleaching.The papermaking properties were very close to the conventional raw materials used in Bangladesh.Therefore,dhaincha can be used as a raw material for pulp production in Bangladesh.

Pulpwood Quality of the Second Generation Acacia auriculiformis

The physical,chemical and fibre characteristics of the 6,8 and 10 years old akashmoni(Acacia auriculiformis)wood from the second generation seed and their suitability for pulping were assessed and compared with the wood of 10 years old from the first generation seed.The A.auriculiformis of 8 years old had the highestα-cellulose and lower lignin than those of 6 and 10 years old,which are similar to the first generation wood.This study also evaluated the effect of cooking time,temperature and active alkali on kraft pulping.The most important influence factors for pulp yield and kappa number were active alkali charge and time.The highest screened rejects were observed for young tree.Delignification degree of the 1st generation was faster than that of the 2nd generation A.auriculiformis.