Pulp Consistency Research Articles

Cellulase binding to cellulose fibers in high shear fields

Cellulase binding onto cellulose fiber was investigated in a turbulent mixing environment created by an axial flow impeller. The binding of the enzyme was found to be associated with various process variables studied, e.g., intensity of agitation, reaction time, pulp consistency, pH, temperature, and concentration of enzyme. The similarity between trends in enzyme binding and enzyme activity confirmed that the reduction of binding with increasing intensity of agitation over time was due to denaturation of the enzyme by shear. Physical forces like shear can disrupt the structure of the enzyme resulting in the loss of binding ability and activity. It also appeared that mild mixing did not denature the enzyme, but rather the enzyme dispersed better into the pulp slurry, resulting in a higher percentage of enzyme bound to fiber. However, increasing shear resulted in a reduction in binding and activity. At a low rpm, the binding increased initially with time, reached a peak at about 3 to 5 min, and then decreased gradually. With respect to time and shear rate, the reduction in binding and activity was much more significant at 10 min of mixing. It is concluded that a high shear and/or a prolonged exposure to a low shear can disrupt the structure of enzyme resulting in the loss of binding ability and activity. At low enzyme concentrations, the binding of enzyme onto fiber increases with increasing concentration of enzyme. Similarly, the percentage of enzyme bound increased with increasing pulp consistency. Since cellulase needs mild temperatures and acidic environments to maintain its activity, high temperature and pH caused a reduction in binding. A pH of 4 and a temperature of 30°C yielded the highest percent binding among the conditions studied.

中濃度パルプのオゾン漂白

In Order to improve delignification and reduce viscosity drop on medium consistency ozone bleaching, bleaching conditions and bleaching methods were investigated.The results may be summarized as follows : (1) The lower pH conditions on ozone bleaching made better delignification until lower kappa number and the bleached pulp had better resistance against alkali. (2) It was confirmed that manganese inside pulp could be strikingly washed out by sulfuric acid solution.(3) With removal of ozone oxidation products on multistage ozone bleaching, delignification was improved.(4) By sequential changing of pulp consistency (in this experiment, pulp was bleached at 15% pulp consistency initially and at 8% pulp consistency finally), we obtained a bleachability that pulp could be bleached with higher bleaching velocity initially and lower viscosity drop finally.And in order to find alkaline decomposition and the color reversion properties, OZEP, OZD and OZ-bleached pulp were compared.The results may be summarized as follows : (1) OZ-pulp has declined resistance against alkali. The viscosity drop of OZEP pulp bleached under alkaline conditions was much higher than that of OZD pulp bleached under weak acidic conditions.(2) The color reversion of OZEP-bleached pulp and OZD-bleached pulp was lower than that of OZ-bleached pulp. The color reversion of OZEP-bleached pulp was lowest.

酸素漂白の特性

In 1961, we developed the alkali-oxygen bleaching method and commercialized it to minimize envilomental pollution. The characteristics of the method were in high pulp consistency to perform delignification under minimum degradation of cellulose. In the method oxygen was supplied to a pulp through a thin alkali solution layer on the pulp. And reactions were controlled by the supplying rate of oxygen. The condition protected cellulose which was less oxidizable than lignin. The idea was supported by the results that additions of glucose and water soluble lignin brought protect effect to cellulose in the high pulp consistency as the result of their preferential consumption of the oxygen. In the low pulp consistency (1.2%) the addition of them accelerated the degradation of cellulose. The substances showed the two opposite effects. protection and degradation. Their balance was depended on their situation. When they were on the pulp surface they most protected cellulose. The characteristics allowed continuous operation of kraft cooking and oxygen bleaching using a simmple and imperfect washing, once replacement washing with hot water. The delignification reaction by oxygen was influenced remarkably by structure of lignin in the pulp. And the structures were depened on cooking condition, especially on cooking temperature. The lignin in the kraft pulp cooked at 180°C was easily removed regardless of the residual amount in the pulp. That at 160'C was hardly removed for even the pulp of lower K No.The delignification reaction was the first order reaction of the amount of lignin under excess oxygen.

Adaptive control of basis weight and moisture content for a paperboard machine

Abstract The development and industrial application of a MIMO adaptive control strategy for a paperboard machine are investigated. The control strategy incorporates a conventional regulatory control technique, multivariable k-incremental predictor and self-tuning control algorithm. The pulp consistency and flow rate, and the steam pressure are simultaneously manipulated to control the reel basis weight and moisture content. The control system demonstrates a satisfactory performance. The variations in reel basis weight and moisture content are greatly reduced.

On the selectivity of ozone delignification of softwood kraft pulps

Ozonation of kraft pulp and oxygen-delignified kraft pulp in acetic acid/water mixtures has been studied at different pulp consistencies with and without an inhibitor to obtain information about the limitations of the selectivity of the ozone treatment. The experiments have been performed according to a full factorial design and data have been analysed by stepwise regression analysis. The results show that a better delignification selectivity can be achieved when ozone is applied in acetic acid media instead of conventional aqueous media. By combining conventional oxygen delignification and ozonation in acetic acid, pulps with equal strength properties and better optical properties compared to those of conventional O(DC)E prebleached pulps can be obtained. This study has also revealed that the reagent is utilized far more efficiently in ozonation at high pulp consistency (35%) than in ozonation at low consistency (1%), and that a similar selectivity can be achieved in both types of ozonation by choosing appropriate conditions. The greater selectivity of ozonation in acetic acid than in water is interpreted in terms of different stabilities of the oxidant in these reaction media. The relation between the formation of hydroxyl radicals and the extent and selectivity of delignification during ozonation has been investigated. The final bleaching of pulps prebleached with ozone in acetic acid medium has been studied. Two final bleaching sequences are presented, by which pulps with ISO brightness levels of 79% and 90% can be produced.

Air bubble holdup in quiescent wood pulp suspensions

AbstractAir bubbles were injected into the bottom of a column filled with an aqueous suspension of wood pulp fibers to permit measurement of the probability that the bubbles escape the fiber network to reach the surface. Escape probabilities were measured as functions of bubble volume, pulp consistency (weight fraction of fibers), and pulp type. For a given consistency, larger bubbles rose through the column whereas smaller bubbles were held up in the fiber network. The higher the consistency, the greater the bubble diameter required for escape. The minimum buoyancy forces required for bubble escape were correlated with estimates of the yield stress of the fiber network.

パルプの酵素による改質 ベッセレックスによるベッセルピック対策

A new biological process for upgrading pulp is developed. Cellulase treatment on pulp before refining exhibited a remarkable effect on properties of the paper. Various cellulase were examined, the best results were obtained with VESSELEX. The vesselpick number were greatly decreased, and freeness and mechanical strength were increased without any loss of yield. To optimize the cellulase treatment, temperature, pulp consistency, contact time, and enzyme concentration were investigated. The results showed that cellulase exhibite sufficient effect at low enzyme concentration (0.02-0.03%) for only 4 hours reaction time. This enzymatic process is especially effective in case of useing the eucalyptsus cips, which have large vessels, and is simple to adapt into existing procese.

酵素による新聞古紙の再生

A new deinking method for old news paper was developed by using commercially available cellulase. About 300 g of old news paper was defibered at 4% pulp consistency by batch type pulper in the enzymeadded water in which pH was controlled at 4.7. And then the suspension was transferred to a laboratory floatation system. The following results were obtained with the deinked pulp from the above-described process.(1) Handsheet from the DIP showed a satisfactory level of brightness.(2) Defibering time was reduced significantly, compared to conventional method.(3) The Canadian standard freeness showed a reduced value for the DIP compared with that from the conventional method. Consequently, an increase in sheet strength was obtained with handsheet from the DIP.(4) During the defibering and floatating process by this enzymatic technique, no other additives than enzyme and buffer were required, such as NaOH, water glass, synthetic displector, carboxylic acid soap, hydrogen peroxide and DTPA. Therefore, the substantial reduction in operation cost and treating cost with the effluent liquor are estimated by adopting this enzymatic method.

Effect of pulp consistency and pH in ozone bleaching

Effect of pulp consistency and pH in ozone bleaching

Effect of pulp consistency and pH in ozone bleaching

Effect of pulp consistency and pH in ozone bleaching

MEASURING CONSISTENCY OF TOMATO THIN PULP AND PUREE

Of several objective methods that were compared for their dependability in measuring the consistency of tomato thin pulp (juice before concentrating) and puree, the Bostwick Consistometer and Ottawa Texture Measuring System (back-extrusion cell, maximum force value) were found to be the most reliable. Of these two, the Bostwick is recommended for routine tests because it is simple to use, versatile and inexpensive.Key words: Tomato product, pulp, puree, consistency, objective tests

液体サイクロンによる道管分離のメカニズム Ｉ セントリクリーナーによる道管分離結果

Experimental study with Centri-Cleaner to separate vessel elements from wood fibers was carried out using several bleached kraft pulps produced from some tropical and other hardwoods. Vessel separation efficiencies of pulp were examined in detail.It became clear firstly that vessel elements having larger projected area and lower L/D ratio (ratio of longer side length (L) to shorter one (D) of projected vessel element) were separated more effectively into reject side of hydrocyclone.Secondly, separation efficiency varied with pulp species. It was considered that one of the main reasons was the differences of shape (L/D) and size (projected area) of vessel elements. The pulp containing many slender (high L/D ratio) vessel elements had low separation efficiency.Furthermore, the separation efficiency decreased with an increase in pulp consistency for Centri-Cleaner treatment. This is probably due to the development of fiber network in a Centri-Cleaner at high pulp consistency, which would hinder the settling of vessel elements.

超音波によるパルプサスペンジョンの濃度測定

Ultrasonic attenuation of suspensions prepared by various types of pulps was measured in view of developing a new technique for monitoring the consistency of pulp slurry. Desirable relationship was found between the fiber consistency and the ultrasonic attenuation by the fibers in a certain consistency range. The effects of freeness, filler and sizing agents, etc, were also studied. Compared with general methods, the technique proposed is of high accuracy, has a broad measurable range in low pulp consistency and is less affected by filler and the color of pulp, etc. Therefore, it is considered to be most suitable for measuring pulp consistency below 2-3 percent.

液体サイクロンによる道管分離のメカニズム ＩＩ パルプとモデル粒子の沈降速度

Principle of separation or classification with hydrocyclone is to make use of difference in settling volocity under centrifugal force among particles. It has been shown that Centri-Cleaner 600 is elective for the separation of vessel elements from wood fibers of various BKPs. This paper deals with experimental study of settling velocity of various pulp fibers, vessel elements and model particles. The results were used to explain mechanism of separation with hydrocyclone.With the model particles of vessel element, it was comfirmed that particles with large projected area and small L/D ratio (length to width ratio) settled faster in water. And the settling velocity of model vessel element was a function of its apparent density and thickness. The settling velocity of fiber, on the other hand, was proportional only to a diameter and apparent density of fiber.Effect of pulp consistency on vessel separation was also examined in terms of space available for vessel element to fall through the network of pulp fibers. The extremely low separation efficiency of vessel elements with high L/D ratio could be explained by the space availability.

Effect of a chromium salt on the electrochemical bleaching of sulphite pulp

Electrochemical bleaching of sulphite pulp was carried out by using NaCl solution as an electrolyte. At pH 10, a temperature of 35 °C and a pulp consistency of 2%, the rate of bleaching was found to increase with increasing current density and salt concentration. The power consumption ranged from 0.4 to 3.3 kW h per kilogram of pulp, depending on the current density or salt concentration. The addition of 0.02% K 2Cr 2O 7 increased the degree of bleaching by 6% and the current efficiency by 7% with no deterioration effect on the pulp quality.

Kinetic Models for Hydrogen Peroxide Bleaching of Mechanical Pulps

Abstract Several commercial thermomechanical pulps and stone ground-wood pulps were bleached to determine how the bleaching rate is affected by peroxide and alkali concentration, pulp consistency and temperature. The bleaching rate seems to be determined by the balance between the bleaching action of peroxide anion (HO) and color formation by alkali (OH). At a given peroxide concentration, increased alkalinity increased the bleaching rate due to the formation of peroxide anion, up to a given alkali concentration above which a further increase led to a decrease in reaction rate. This is probably due to the fact that at high alkalinity, pOH < 2.5, an increase in hydroxide ion concentration gives only a slight increase in the peroxide anion concentration, at lower alkalinity, the increase in peroxide anion concentration is approximately proportional to that of the hydroxide ion. The bleaching rate (dCk, /dt) at 15% pulp consistency could be expressed by the kinetic equation where C, is the light absorption c...

前処理解繊された広葉樹ホロパルプの性質 ＩＩＩ 未こう解パルプのフリーネス

The C.s. freeness of unbeaten PFP (Pulp produced by the Pollution Free Pulping high yield process) from pilot plant was around 400 ml and extremely lower than that of commercial BKP (Bleached Kraft Pulp).The cause of the low freeness value was investigated by 3 variables, such as specific surface area, specific volume and pulp consistency of filter bed during freeness test. The excessive PFP fines, which were secondarily produced during prefiberization stage, contribute to higher specific surface area and lower freeness. But low freeness in PFP is mainly due to its hemicelluloses because alkali extracted PFP and B·KP showed almost the same freeness. PFP hemicelluloses make fibers more flexible than B·KP and such flexible fibers give very compact filter bed during freeness test. Specific volume of PFP is not so different from B·KP in spite of its higher content of dilute alkali soluble hemicelluloses.PFP gives higher consistency filter bed with lower specific surface area than B·KP of the same freeness.

光学的方向によるパルプ繊維のフィブリル化の評価

This paper describes on the new optical method for an evaluation of the state of fibrillation of paperinaking fibers. Turbidity and light absorption coefficient were defined as follows.τ=1n (I0/I), ε= (1/C) 1n (I0/I) C : pulp consistency, I, I0 : transmitting light intensity of pulp suspension and water respectivelyτ : turbidity, ε : light absorption coefficientEffects of fiber length and cross sectional area (corresponds to denier) on turbidity were investigated by rayon fibers. It was found that turbidity did'nt depend on the fiber length, but was affected by width strongly. Specific surface area calculated from light absorption coefficient under certain assumption gave nearly the same value to surface area estimated from definition of denier. For classified unbeaten pulp, light absorption coefficient of hardwood bleached kraft pulp suspension is larger than that of softwood bleached kraft pulp suspension at the same fraction. On the other hand, light absorption coefficient of short fiber fraction is larger than that of long fiber fraction for both two pulps. These facts were explained by the difference of fiber width. It was observed that the width of hardwood bleached kraft pulp fiber was smaller than that of softwood bleached kraft pulp fiber at the same fraction and that the fiber width of short fiber fraction was smaller than that of long fiber fraction. This optical method was not affected with lignin content as well as temperature of suspension.

Nitric acid leaching of molybdenite concentrates

Molybdenite (MoS 2) has been found to leach slowly in dilute (1–4 M) nitric acid at room temperature, to yield solutions of molybdic acid (H 2MoO 4) and sulphuric acid. The solutions are supersaturated with respect to MoO 3 β 1 2 H 2O , which is easily precipitated from the filtered pregnant solution as a fibrous crystalline solid having the consistency of paper pulp. A complete process, which is based on removal of sulphate as gypsum (CaSO 4 • 2H 2O) by limestone addition, and regeneration of most of the required nitric acid from gaseous nitric oxide produced during the leach, has been proposed. The process is potentially economic if relatively pure molybdic oxide has a value moderately higher than roasted calcines. This paper describes the process steps, as they performed in bench scale tests.

Pulp Consistency Measurement and Control System

The consistency measurement of the pulp is not completely solved problem in pulp and paper industry. Pult is not a newtonian fluid and thus several different problems exist. For example flow and temperature variations of the pulo disturb most measuring systems. Moreover the quality of the pulp and the range of the pulp consistency measurement have an effect to the linearity of the measuring devices.Pulp diluting is usually a control problem of a zero capacity process. There is a dead time between the supplying point of the diluting water and the measurement point of the consistency. Thus the exact and stable control of the consistency is quite a difficult task with traditional analog devices.An industrial compensated measurement and control system for pulp consistency is presented, where the effects of temperature, flow and mass quality variations are compensated. The control strategy is based on the feedforward control and on the Dahlin algorithm. Moreover an advanced system, where the consistency is estimated with a Kaiman filter, is described.