Showing papers in "Appita Journal in 2009"

An Experimental Study of Australian Sugarcane Bagasse Pulp Permeability

Abstract: In this experimental study the permeability of Australian bagasse chemical pulps obtained from different bagasse fractions were measured in a simple permeability cell and the results compared to one another as well as to eucalypt, Argentinean bagasse and pine pulps. The pulps were characterised in terms of the permeability parameters, the specific surface area, Sv, and the swelling factor, α. It was found that the bagasse fraction used affects these parameters. Fractionation of whole bagasse prior to pulping produced pulps that have permeability properties that compare favourably with eucalypt pulp. The values of Sv and α for bagasse pulp also depend on whether a constant or a variable Kozeny factor is used.

Adjusting Near Infrared Wood Property Calibrations for Central Brazil to Predict the Wood Properties of Samples from Southern Brazil

Abstract: Recent research has shown that accurate whole-tree wood property predictions can be made using calibrations based on near-infrared (NIR) spectra from milled increment cores. In this study, we demonstrate that whole-tree wood property calibrations for lignin and pentosan content, developed with a variety of eucalyptus species and hybrids in central Brazil, may be applied to a separate population of eucalypts in southern Brazil. We randomly selected 2 to 10 samples from southern Brazil and added these to the original calibration set. The ratios of performance to deviation (RPD) for lignin content, pentosans, and pulp yield were significantly improved using this method, but density predictions were unimproved. WinISI software was also used to select the most spectrally representative samples from southern Brazil for addition to the calibration set, but improvements were similar to the randomly selected samples. The addition of four southern samples to the original calibrations did not significantly affect their predictive performance on samples from central Brazil.

Determination of Within-tree Variation of Pinus taeda Wood Properties by Near Infrared Spectroscopy. Part 2: Whole-tree Wood Property Maps

Abstract: The application of three spatial interpolation algorithms (Akima, universal kriging, and semiparametric regression methods) to the study of within-tree variation of air-dry density and microfibril angle predicted by near-infrared models in Pinus taeda trees is presented. The theory behind each algorithm is briefly reviewed and its application to the study of the within-tree variation of wood properties is addressed. The use of predicted wood properties as control data points for spatial interpolation was successful and allowed the generation of maps showing within-tree variability at high resolution and quality. The maps obtained by the different methods showed similar features indicating that air-dry density and microfibril angle were highly predictable as a function of their positions within the trees.

Determination of within-tree variation of Pinus taeda wood properties by near infrared spectroscopy. Part 1: Development of multiple height calibrations.

Abstract: Many studies have demonstrated that several important wood properties including cellulose, density, lignin, microfibril angle, and stiffness can be estimated using near-infrared (NIR) spectra collected from the radial-longitudinal surface of intact radial strips However, a common aspect of these studies is that they have been based on breast height (14 m) samples, limiting the usefulness of these calibrations to that height only If the within-tree variation of wood properties is to be examined by NIR spectroscopy, then multiple height calibrations are required This was the primary objective of this study Wood property calibrations based on NIR diffuse reflectance spectra collected from the radial-longitudinal surface of wooden strips from several different heights were successfully obtained Calibration and prediction statistics were similar to those reported in previous studies using breast height samples

Evaluation of Cationic Polymers to Control Pitch Deposition

Abstract: A wide range of cationic polymers of varying chemical structure, charge density and molar mass were evaluated for their effectiveness to control wood resin deposition. The ability of the polymers to attach model wood resin particles to thermo-mechanical pulp fibres and to maintain the wood resin in the colloidal phase was determined over a pH range of 4.75, 6.85 and 8.06. High molar mass poly-DADMAC, copolymer poly- (AM-co-DADMAC) and guar gum were found to be the best fixatives over the pH range investigated. The performance of poly-DADMAC was found to increase with molar mass and charge density. A conceptual model was proposed to explain the behaviour of the polymers based on their ability to stabilise the wood resin colloids, to attach the wood resins to pulp fibres and to affect the wood resin particle size.

Moisture and temperature measurement of paper in the thickness direction

Abstract: In this work the z-directional moisture and temperature profile of fine paper was studied during drying. The goal of this research was to determine moisture gradients in thickness direction during drying. This information is needed to improve existing drying models as well as to help deepen the understanding of the drying phenomena and its effects on paper structure. The gradient information can be directly used in the drying models and will assist in making more accurate estimations of the capacity and quality effects of drying on paper. For this study a new method for measuring the z-directional moisture profile of paper was developed. The results show that during paper drying there exist significant gradients in z-directional moisture with profiles showing differences in moisture content of up to 25-35% across the thickness of the sheet, depending on the drying conditions. Similar magnitude moisture content differentials are observed in both measurements and numerical simulations.

Wood Pitch Fixative Evaluation by Laser Particle Size Analysis

Abstract: Wood pitch deposition onto the surface of papermaking machinery continues to be a costly problem. Fixatives - substances said to attach wood resin to wood fibre - have been used to alleviate wood pitch deposition to varying degrees of success. This paper aims to evaluate to what degree fixatives alter the colloidal wood pitch particle size. We were able to show how different wood resin fixatives alter the colloidal wood pitch particle size at three different pH values (4.75, 6.85 and 8.06). The fixatives can be divided into two categories, colloid disrupting and colloid stabilising, according to how they change pitch particle size.

Alkaline sulphite/anthraquinone (AS/AQ) pulping of rice straw and TCF bleaching of pulps

Abstract: Alkaline sulphite-anthraquinone (AS/AQ) pulping of rice straw from North eastern Iran and totally chlorine free (TCF) bleaching of resulting pulps was investigated. In the AS/AQ pulping experiments, the active alkali charge was chosen between 14 and 18% on oven dry rice straw and the alkali ratio, Na{2}SO{3}/NaOH, was varied from 60/40 to 30/70. While a constant cooking time at maximum temperature of 60 minutes was applied, the maximum temperature was varied between 155 and 160 C. AQ dose and liquor to straw ratio were kept constant at 0.1% on o.d. straw and 4:1, respectively. Reference soda and soda/AQ pulps were produced using different chemical charges. AS/AQ pulps with kappa numbers below 7 were easily produced while Soda/AQ and soda cooks carried out under similar conditions yielded kappa numbers of around 10. The AS/AQ process gave higher yield and the pulps had higher brightness than soda and soda/AQ pulps. The soda pulps had higher tensile strength but the AS/AQ pulps had higher tear strength. TCF bleaching of AS/AQ pulp was performed in two sequences, OQ(OP) and OQ(OP)P . Delignification degree of over 50% was obtained and after the (OP) stage a brightness of 80% ISO was achieved. The sequence OQ(OP)P, with 2 or 4% H{2}O{2} in the final P stage improved brightness to 85.5 and 87% ISO, respectively. These results confirm that rice straw AS/AQ pulp is easy to bleach compared to soda/AQ and soda pulps which require OQ(OP)QP or even an OQ(OP)QQP sequence in order to reach target brightness of 80% ISO. Bleaching led to only small losses in tensile and burst strength but enhanced tear strength. The results of this study indicate that AS/AQ pulping together with TCF bleaching is able to produce high quality pulp from rice straw for writing and printing paper.

Changes in viscosity and boiling point elevation of black liquor when a fraction of lignin is removed - consequences in the evaporation stage

Abstract: Removing lignin from kraft black liquor affects the physico-chemical properties of the liquor. The viscosity and boiling point elevation of black liquor are of crucial importance to the design as well as the operation of the black liquor evaporation plant. Since these properties are strongly influenced by the composition of the black liquor, it is of great interest to understand how they are influenced by the removal of lignin from black liquor. The viscosity and boiling point of black liquor samples taken both before and after lignin removal runs, and a mixture thereof, have therefore been measured in this work. Six different original black liquors (softwood and hardwood) were used as the source for lignin removal runs; a total of 18 liquors of different lignin concentration were studied. It was found that the property of black liquor that was most affected by the removal of lignin was viscosity, at most it was reduced by an order of magnitude (depending on the dry content, mill and wood species). A decrease in boiling point elevation was also found at dry contents above 40-50 % when a fraction of the lignin was removed from the black liquor.

Recycling of lignin: A new methodology for production of water reducing agent with paper mill sludge

Abstract: SUMMARY Disposal of paper mill sludge (PMS) is a major solid waste problem for the pulp and paper manufacturing industry. In this paper, an innovative way to recycle PMS is presented as follows: lignin is extracted from PMS, and then it is modified by using sodium sulfite and formaldehyde in sequence. The modified lignin is used as an additive for concrete. The water reducing rate reaches 25.2% and the compression strength and reinforcement corrosion of the concrete all conform to the Chinese National Standards. Thus, it results in an innovative method of recycling organic by-products and reducing environmental pollution.

Mechanism of pitch adsorption on carboxy methyl dextran surfaces

Abstract: The direct adsorption of pitch particles onto pulp fibres was investigated as a pitch control strategy. The affinity of colloidal pitch for carboxyl methyl dextran (CMD) surfaces was studied by surface plasmon resonance (SPR) spectroscopy and optical microscopy. CMD was selected as model surface representing the cellulose and hemicellulose fractions of the pulp fibres. The dynamics of adsorption and desorption of concentration pulses of colloidal pitch on carboxy methyl dextran were followed at the solid-liquid interface in real time by SPR. The parameters investigated were temperature, pitch concentration and sequence of pitch build up. The direct adsorption of pure colloidal pitch onto pulp fibres is not an option for papermaking. This is because of the very low chemical affinity measured between pitch and the model CMD polysaccharide. Virtually no pitch remains adsorbed by chemical interaction on CMD surfaces submitted to low shear. In spite of its low affinity for polysaccharides, colloidal pitch can be carried by fibres as the low desorption rate might not allow full particle desorption during the time frame of the forming process, and some physical entrapment might also occur. Pitch has a stronger affinity for pitch covered surfaces than for polysaccharides.

Some properties of Flexographic Printing Plates and Aspects on Print Quality

Abstract: Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate. Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties. Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.

New initiatives for environmental protection and energy saving in the Chinese paper industry.

Abstract: The restructuring and upgrades of Chinese paper industry and its impact in the promotion and development of environmental protection in other industries is discussed. It is suggested that optimisation of the whole subsystem of paper mill by the waste-to-energy concept, and closing water loops will significantly contribute to production profitability.

The Influence of Boron on the Emission of Sodium during Black Liquor Combustion under Oxidative Conditions

Abstract: The addition of boron to black liquor has the potential to reduce fume formation in a kraft recovery boiler. Two kraft black liquors, with and without boron, were analysed. Single 10 mg droplets were introduced into a furnace and were burned at temperatures of 900, 1000 and 1050 C with oxygen concentrations of 2, 5 and 10 (vol %). Under these conditions, the addition of boron to the black liquor is found to reduce both the extent of sodium emission and the combustion time. This shows that the boron reduced the sodium loss due to the lower amount of sodium carbonate available to be decomposed by the char. The char combustion time of the liquor with boron is found to be shorter because some of the char may be consumed by the borate. The added boron reduced the sodium loss mainly during the char combustion stage.

LCA for the Engineering Analysis of the Forest Biorefinery

Abstract: Many pulp and paper companies are considering implementation of the forest biorefinery for revenue diversification in order to improve their financial performance, implicating the addition of biomass-based products to the existing pulp and paper products portfolio The environmental benefits associated with these bio-products may not be immediately obvious For this reason, systematic methodologies are required to identify those process/product combinations that offer the most promising environmental benefits In this paper, it will show that the direct application of classical LCA methodology is not well suited for this purpose Instead, an LCA methodology based on system boundary expansion is proposed and used in an industry case study involving the implementation of an integrated forest biorefinery (IFBR) process at two different pulp and paper mills Using this approach, it is shown that the implementation of the IFBR for the production of polylactic acid (PLA) leads to environmental benefits, but only under certain conditions The main objective of the case study was to demonstrate the proposed approach and not to determine the best way of implementing an IFBR process For this purpose, more detailed process design, including the analysis of several scenarios and the corresponding LCA studies, would be required

Ink Transfer and Refusal Mechanisms in Lithographic Offset Printing and the Measurement of the Splitting Force of Fountain Solution Film

Abstract: This paper reports a recent investigation of the ink transfer and refusal mechanisms in lithographic offset printing. These are old but poorly understood applied surface chemistry problems. An adhesion approach is taken to investigate the position of splitting of an ink-fountain solution composite layer using a near-static and a dynamic method. Results from this study show that ink transfer and refusal in lithographic offset printing cannot be predicted by thermodynamic quantities such as surface energy or interfacial energy or work of adhesion. Ink transfer and refusal must be predicted by comparing the ink or fountain solution adhesion strength to other surfaces and the film splitting forces of the ink and fountain solution. This paper also reports the development of a new method which can measure the fountain solution layer splitting force under simulated printing conditions. This method has, for the first time, provided experimental value of the fountain solution layer splitting force relative to the ink layer splitting force. These forces provide direct information which can be used to control the press operating conditions. It is possible that this method can be adapted to determine forces that cause linting and therefore will also serve as a new and useful tool for understanding and controlling linting in lithographic offset printing.

Drainability, Permeability and Formation of RCF Pulps Blended with Sugar Beet Pulps

Abstract: Influence of retention systems and shear forces on drainage time and air permeability of handsheets prepared from a furnish of recovered fibres containing 10% enzymatically modified sugar beet pulp has been investigated. Addition of cationic coagulant neutralised the anionic soluble and colloidal particles present in suspensions and increased the effect of retention aids. Aluminium sulphate was more effective in the elimination of the negative effect of enzymatically modified sugar beet pulp and shortened the drainage time more then PDADMAC. The cationic coagulant aluminium sulphate, in a retention system with a cationic and anionic polyacrylamide flocculant, shortened drainage time of recovered fibres and enzymatically modified sugar beet pulp mixture by a factor of 3.3, increased air permeability by 88% and, in comparison with PDADMAC, improved the formation of handsheets. The retention system containing aluminium sulphate, cationic and anionic polyacrylamide flocculant was most effective with regard to drainage time and air permeability if shear forces were acting. The retention system containing an inorganic anionic flocculant based on modified bentonite or colloidal silica was equally effective, but the effect was reduced by shear forces. Best formation of handsheets was achieved by the application of a retention system consisting of aluminium sulphate, cationic polyacrylamide and anionic colloidal silica. These results should provide good initial guidance whenever the addition of a pulp with high anionic charge and high level of fines is being considered.

Refractive index measurements for brown stock washing loss - Mill investigations

Abstract: The usability of the refractometer to measure washing loss in chemical pulping was studied under mill conditions. Our earlier study showed that measurement works very well under laboratory conditions. The focus of investigation was on brown stock washing before and after oxygen delignification at a Finnish pulp mill. The E-values for the system were calculated on the grounds of the sample lap. Also, an on-line calculation method for washing effectiveness was generated. In addition, washing filtrates and filtrates which were centrifuged from pulp were analysed and the measuring results of the refractometer, SFS-3008 standard, conductivity and COD-analysis were compared. The measuring results indicated that the refractometer is suitable for measuring the dissolved dry solids of outgoing filtrates and pulp suspensions on a single washer. Therefore it is suitable for monitoring washing loss levels in the brown stock washing and because of this real-time measuring of washing effectiveness is possible.

What Is the Role for Biorefineries?: Part 1 - World Energy, Greenhouse Gases and Biorefineries

Abstract: In recent years there has been considerable interest in the concept of biorefineries - factories that will use biomass as a feedstock to produce a range of chemicals similar to those currently produced from crude oil in an oil refinery. One point of debate is whether the development of biorefineries will be an opportunity or a threat to the pulp and paper industry. It is the view of the present authors that much of the current discussion is based on an incorrect understanding of the issues and of the scale of the industry. This paper will address the markets which the first few generations of biorefineries are likely to serve. Over a longer period of time the situation is likely to change. Currently products are made from oil because this is the cheapest route. The pulp industry produces about as much byproduct lignin as it does chemical pulp. This is available as a very low cost raw material (fuel replacement value at most) and yet the quantity of lignin that is converted into profitable products is minute. The difficulty is that lignin is not an ideal feedstock, and is unlikely to become one until crude oil prices are much higher than at present. Over half of the oil produced is used to make transport fuels. In the near future, these are likely to be partly replaced with ethanol or other liquid chemicals produced from sugars and poly-saccha-rides. The technology used here is much more familiar to the pulp and alcoholic beverage industries than to the oil industry, and there is scope for the pulp industry to grow by serving this market. The next largest use for oil is probably as a fuel for stationary units. At the present state of development of synthetic fuels, it is much more economic to fire such units with solid biomass (or in some cases to use gasified biomass) than to go to the expense and complexity of producing synthetic liquid fuels. Only about 15% of oil ends up as 'other products' - including bitumen, petrochemicals, polymers, fibres and solvents. As oil becomes scarce and more expensive, we can expect bio-mass to replace it for some of the 'easier' applications (such as ethanol). The remaining oil produced will be used to produce these other chemicals - but in competition with organics derived from biomass. We can expect there to be a gradual shift with the products which can be most easily (and cheaply) be made from biomass moving to this route first. Thus any shift to bio-refining could represent an opportunity rather than a threat to the pulp and paper industry - possibly through alliances with oil companies and perhaps agricultural processing companies. The challenge will be to take this opportunity.

Applications of an Analytical Method to Calculate the Load Distribution along a Fibre in a Loaded Network

Abstract: A new analytical solution for the load distribution along a fibre in a network has been used to investigate some aspects of paper tensile strength and elastic modulus. The method uses a similar approximation to the shear-lag formulation but allows stress transfer at individual contacts, rather than specifying a single stress transfer function applying along the entire length of the fibre. Measured elastic modulus data, where the fibres only varied in length and not cross-section showed only a small effect of fibre length on modulus. This is consistent with a high overall stress transfer coefficient for each fibre-fibre contact, resulting in the contacts at the ends of the fibres being heavily loaded. The maximum force at the middle of the fibre was calculated as a function of the fibre-fibre shear bond strength. The data showed that most literature values are too low to allow the fibre to break during paper fracture. The simulation method was able to explain the reduction in sheet tensile strength with a reduction in density, but was unable to explain the reduction in sheet strength with reduced fibre length. The assumption that a fibre-fibre bond fails completely once its breaking load is exceeded is believed to cause the discrepancy.