ABSTRACT A comprehensive model for alkaline extraction (E) of chlorine dioxide delignified (D0) softwood kraft pulp (KP) is presented. The dynamics of the process is modeled by taking into account both irreversible and reversible chemical reactions and gas-liquid and liquid-liquid mass transfer. Equations linking molecular-scale composition (amounts of monomeric lignin and carbohydrate structures) and general engineering parameters [κ number (KN), …

ABSTRACT The influence of impregnation conditions on the phenomena involved in the impregnation of Eucalyptus grandis chips was studied with the aid of a new impregnation method. When pre-steaming was used, 30 minutes of penetration time was sufficient to achieve the final degree of penetration (over 95%) with white and black liquor. An impregnation time of 15 minutes was found …

ABSTRACT In earlier studies the degree of penetration was calculated with a method which gave a penetration degree of over 100%, if mill liquors were used, because the method ignored the diffusion of cooking chemicals and dissolution of wood material. In this paper, a new experimental research method is presented, which allows the penetration of mill liquors to be examined …

ABSTRACT The influence of impregnation conditions on the phenomena involved in impregnation was studied with the aid of a new impregnation method. The method was found to be good enough for scientific research purposes and useful for gaining new knowledge of the alkali uptake, alkali consumption and dissolution of wood material during impregnation. An impregnation time of slightly over 15 …

ABSTRACT This study investigated the effects of temperature, chlorine dioxide dosage, and filtrate circulation on various filtrate and pulp properties in chlorine dioxide prebleaching of birch kraft pulp. Also the effect of a preceding A-stage was examined. Kappa number, delignification, and hexenuronic acid removal were unaffected by the used dilution media and temperature. Increasing ClO2 charge resulted in a lower …

ABSTRACT This paper evaluates the process of liquid penetration into wood chips from the retrospective viewpoint of industrial development and research and provides a summary of currently available knowledge in this area. During the past few decades, researchers have been dealing mainly with pulping chemistry and the back-end of pulping processes, while less attention has been paid to the front-end …

ABSTRACT In earlier studies, the fundamentals of the liquor penetration process in the case of hand made, homogenous, identically shaped wooden blocks have been studied. However, the efficiency of liquor penetration into real industrial chips may differ from the efficiency of penetration into ideal handmade chips. In this paper, impregnation experiments with three industrial softwood chip grades including sawmill chips, …

ABSTRACT In this paper, the penetration of water and black liquor into overthick and pre-treated overthick chips (cracked and re-chipped according to thickness) was studied with a laboratory impregnator to investigate ways to improve penetration. Overthick chips were divided in three categories: knot-containing chips, chips without knots and original overthick chips. The results of the penetration experiments were evaluated in …

Abstract Effective separation of soap and turpentine is an important, but mill-specific aspect, regarding the entire softwood kraft process performance. This paper describes a systematic approach to evaluate and solve various extractives-related process problems. In a mill “audit”, the soap and extractives potential of the mill’s wood raw material is first estimated, the key process streams are tested and the …

ABSTRACT Pulping uniformity is critical for improving the performances of cooking and downstream operations such as bleaching and papermaking. In spite of certain success of recent modifications of batch and continuous kraft cooking systems, there is still a lot of room for improving the contemporary cooking systems in order to address problem of heterogeneous pulping. Incomplete penetration and inadequate diffusion …

ABSTRACT The important role of impregnation prior to chemical pulping has been long recognized qualitatively but not fully realized quantitatively. Cost effective production of uniform, high quality pulp can only be achieved by efficient mass transfer of pulping chemicals that must start with complete impregnation of wood chips. The present paper describes the main results of an in-depth research project …

ABSTRACT Displacement batch cooking is nowadays a common practice in the production of kraft pulp. The cook is terminated by a cool filtrate displacement, in which the temperature of the digester is brought down. The terminal displacement is the first washing stage in the pulp mill. The displacement operation is widely practiced, but knowledge of the washing effect of the …

ABSTRACT The front-end of kraft cooking, i.e. steaming, impregnation and heating, controls the cooking performance in terms of mass transfer, delignification and cooking uniformity. Therefore, it is of vital importance to understand the process mechanisms and optimise the front-end process conditions. This article discusses the effect of applying chip presteaming and higher pressure at the front-end of kraft displacement batch …

SUMMARY Efficient removal of air from the wood chips prior to impregnation with cooking liquor is important for achieving pulping uniformity and improving the overall digester performance. Because of its effectiveness, relative simplicity and other advantages, steaming of wood chips became a primary process in pulp industry to fulfil this task. In the present article the process of chip presteaming …

ABSTRACT Importance of the chip impregnation stage is widely recognised in chemical pulping processes. However, there is limited amount of direct data on mass transfer during the impregnation stage. Most methods used for studying the liquid penetration process were based on indirect approaches. A new laboratory impregnator with a special weight sensor was developed, which allowed the direct measurements of …

ABSTRACT Presteaming of chip and applied pressure greatly influence penetration of black liquor into pine chips. Complete penetration of sapwood chips can be reached just by applying extra pressure. To achieve a high degree of penetration of the heartwood chips, air present within the wood capillaries has to be removed by presteaming. Efficient liquor penetration achieved by optimising conditions at …

ABSTRACT Studies of pulp strength delivery have shown that cooking is the most significant step causing strength losses in softwood pulp. In the early 1990s it was demonstrated that different cooking processes resulted in different strength delivery and that displacement kraft batch cooking systems resulted in a pulp strength which comes very close to the strength of the laboratory reference …

ABSTRACT Pine wood (Pinus sylvestris) was delignified using a modern displacement kraft cooking method. A series of laboratory-scale cooks (stop-cooks) was carried out to different cooking degrees representing i) the end points of warm black liquor impregnation (temperature 80°C, total yield 93.3%) and hot black liquor pretreatment (temperature 155°C, total yield 77.5%) and ii) varying chlorine numbers (1.8-7.0) in the …

ABSTRACT This study examines the effect of softwood raw-material properties on pulp quality. Logs of Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and loblolly pine (Pinus taeda) were the raw materials. Wood from Scots pine and Norway spruce was further classified by age as (a) pulpwood (mature wood and older thinnings) or (b) young wood (first thinnings and top …

Pulping and paper technical characteristics of the Sumatra tropical hardwoods. 52nd Appita Annual General Conference, Brisbane, Australia

ABSTRACT Cooking, oxygen delignification, and ECF bleaching characteristics of Scandinavian pine were studied using a recently implemented lab. scale displacement cooking system.  Cooking with white liquor was varied over a wide range in order to produce pulps of varying delignification degrees and yields with const. impregnation and hot black liquor treatment.  The pulps were then oxygen delignified and bleached with a D(EOP)​DD sequence, again varying conditions in order to evaluate delignification and brightness …

ABSTRACT Differently screened chip samples were placed in baskets and were cooked inside industrial batch digesters.  These basket pulps were analyzed with regard to yield, delignification degree, rejects, and pulp strength.  Thickness screening was shown to be advantageous to conventional batch cooking and to full displacement cooking.  In both methods, the rejects could be cut in half by using thickness– ​screened chips.  Moreover, the SuperBatch cooking process, a modified full …

ABSTRACT The title process was briefly reviewed and results for pulp prodn. with northern and middle European timber were discussed for a chlorine-​free bleaching technique in a closed system.

ABSTRACT Substituent effects on the chemical shifts of aromatic carbons in lignin model compounds have been elucidated from C NMR spectra of guaiacyl and syringyl type monomerio and β-O-4 model compounds and guaiacyl type β-5 model compounds. Evaluation of the observed values of substituent chemical shift (SCS) for the aromatic carbons leads to elucidation of a generalized SCS additivity rule, …

ABSTRACT Small and pilot plant scale expts. showed that ion-​exclusion chromatog. with Amberlite IR 140 columns is an efficient technique for the sepn. of spent sulfite liquor (SSL) components into reasonably pure and sugar-​free lignosulfonate and tech. grade sugar fractions.  The use of strongly acidic cation exchanger in the same ionic form as the SSL obviated the need for regeneration between samples, which are displaced with H2O.