Effect of microwave treatment on drying and water impregnability of Pinus pinaster and Eucalyptus globulus

Wood is a material that has been used by humankind for a long time. However, wood researchers and industry have always been concerned about the issues during wood drying and the permeability problems of certain species. In this sense, microwave technology has been applied for wood drying and improving permeably. This paper investigates the microwave drying of two Portuguese wood species, Pinus pinaster sap and heartwood and Eucalyptus globulus heartwood using small clear specimens. The samples were grouped into six during each microwave treatment run according to their similarity of initial moisture content. Once the drying was completed, control and microwave -treated samples were impregnated with desalinated water to analyze their improvement in water absorption, and the compression strength parallel to the grain was analyzed. The results showed that each wood species behaves differently under microwave drying and initial moisture content. The impregnation results demonstrated that pine and eucalyptus microwave -treated heartwood samples improved their capability to absorb water. Finally, only the microwave -treated specimens of eucalyptus heartwood presented a decrease in the values of compression strength parallel to the grain compared to the control group. Therefore, MW treatment presents possibilities for further applications for the wood industry with supporting results

Avaliação da qualidade do papel produzido com fibras de Acacia spp

Com o presente trabalho pretende-se aprofundar o conhecimento sobre o potencial papeleiro da madeira de Acacia melanoxylon e Acacia dealbata. Para efeitos de posicionamento relativo das matérias primas, utilizaram-se aparas industriais de Eucalyptus globulus. A transformação da madeira em pasta foi realizada através do processo ao sulfato. O comportamento global das três espécies nos processos de cozimento e branqueamento é semelhante. No entanto, face à amostra de Eucalyptus globulus usada, a Acacia melanoxylon exibe um rendimento em pasta ligeiramente superior, o que está de acordo com os teores de lenhina e extractivos das madeiras. Para avaliar o potencial das pastas branqueadas na produção de papel, estas foram submetidas ao processo de refinação, em PFI, tendo-se obtido suspensões de pastas com resistência à drenagem crescentes. Posteriormente, caracterizou-se a suspensão fibrosa e o potencial papeleiro. Para o mesmo nível de refinação, os papéis produzidos com fibras de acácia apresentam valores superiores de lisura, índice de tracção e índice de rebentamento. Por outro lado, as fibras da Eucalyptus globulus apresentam maior resistência intrínseca e têm potencial para produzir papeis mais resistentes, embora à custa de maior consumo de energia na refinação. Para um dado nível de resistência mecânica, as características ópticas dos papéis são semelhantes

Ozone depolymerization of polysaccharides in different materials

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The effect of shear rate on apparent viscosity for different pulp suspensions

The goal of this work was to study the relationship between chemical pulps suspensions rheology and the operating variables of refining for three different paper fibres, namely Pinus sylvestris, Eucalyptus globulus and Betula verrucosa. The intention was the establishment of the best conditions for the refining of chemical pulps for paper production. In order to obtain that, the hydromechanics of the beating was analysed for the three pulps. So, the normal and tangential forces were evaluated, the distance between rotor and stator was measured and the pulp apparent viscosity evolution during refining was calculated. The refining essays took place in a laboratory Valley refiner, and the studied variables were the charge on the roll, the rotor speed of rotation and the specific applied energy. A global relationship between the apparent viscosity and the shear rate was finally obtained

Papermaking potential of Acacia dealbata and Acacia melanoxylon

The pulping and papermaking potential of Acacia dealbata and Acacia melanoxylon were studied using Eucalyptus globulus as a reference. Pulp yield, alkali consumption and delignification in the kraft process, of both species, compare very well with the reference. Pulp yield can be higher than that of E globulus and the residual lignin content lower after cooking, which is in good agreement with the lower lignin and extractives content of the wood samples used. Pulps produced from Acacia have slightly lower fibre length and coarseness and higher fibre width and wet fibre flexibility than E globulus pulps. As a consequence of fibre characteristics, the paper produced from Acacia is denser and exhibits higher tensile and burst strength, and lower tear resistance than that from E globulus, at a given PFI revolution. For the same sheet density E globulus displays higher strength properties, but the consequence of achieving this is a lower drainage rate and higher energy consumption in refining

Effect of carry-over on the kinetics of chlorine dioxide delignification of an unbleached hardwood kraft pulp

This work is concerned with the kinetics of the prebleaching stage of a kraft pulp of Eucalyptus globulus with chlorine dioxide. Its main purpose is to discuss the influence of the degree of washing, expressed as the COD of the pulp, on the kinetics and stoichiometry of chlorine dioxide delignification. The effect of the carry-over on the rate of delignification of a Do stage was studied over time for pulps with different initial organic charges (COD). A set of experiments was specially designed to discriminate the individual role of lignin and of COD upon the initial consumption of chlorine dioxide. A modified mathematical model, taking into account the reactions of chlorine dioxide with both lignin and the carry-over, has been developed. In this model, the initial chlorine dioxide consumption (in the fast phase of reaction) is dependent on two factors: the carry-over of the pulp and the temperature of operation. However, the carry-over does not affect the corresponding initial depletion factor for the Kappa number. The role of the dissolved organic material, carried with the pulp, upon the rate of reaction in the slow period is better described in the stoichiometry. The fit of the experimental results obtained for pulps with different COD reveals good prediction capabilities for both Kappa number and chlorine dioxide concentration in a conventional D0 stage

Effect of unbleached pulp kappa number on the kinetics of chlorine dioxide delignification

Chlorine dioxide delignification of different unbleached kraft pulps from Eucalyptus globulus, having Kappa numbers of 12 to 18, was studied in the temperature range of 285 K to 358 K. The effect of the unbleached pulp Kappa number on the initial fast phase of delignification was investigated with respect to the depletion factors for Kappa number and chlorine dioxide concentration, as proposed by Barroca et al. Furthermore, the behaviour of the floor lignin content of the pulp, or the floor Kappa number, was analysed within this range. The results show that all pulps exhibit a similar pattern, with respect to temperature, in depletion factors for Kappa number and chlorine dioxide concentration. The degree of normalised delignification and chlorine dioxide consumption is very similar and independent of the Kappa number of the unbleached pulps. Moreover, the results reveal that there is a strong correlation between the floor lignin content and the temperature, and that this correlation is applicable to a wide range of unbleached pulp Kappa numbers, since the residual Kappa number is independent of its initial value. The results enable the general application of a kinetic model to kraft pulps with different unbleached Kappa numbers

Determination of sugar content in Pinus pinaster and its corresponding hollocellulose, cellulose and kraft pulps

This paper deals with the study of the polysaccharide complex from Portuguese Pinus pinaster, as well as from its main components, i.e., holocellulose, cellulose and pulps obtained using different cooking conditions. Nordic Pinus sylvestris was also studied in order to compare it with Portuguese pine. Two methods were used: one consisted of the hydrolysis of polysaccharides with trifluoroacetic acid (TFA) and quantification of the amount of each sugar using High Performance Liquid Chromatography (HPLC). The latter approach used here consisted of the hydrolysis of the samples under scrutiny by sulphuric acid and converting it into alditols, which were then esterified before injecting to Gas Chromatography coupled with Mass Spectrometry. Myo-inositol was used as an internal standard. The results obtained by the two methods showed that the TFA procedure prevents monosaccharide degradation, comparatively with the sulphuric acid one. In fact, the overall sugar yield was found systematically higher than 93% for TFA hydrolysis, whereas that corresponding to H2SO4 treatment never exceeded 77%. The sugar composition of both pines was found very similar and the sulfidity level (from 10 to 55%) did not affect the pulp sugar composition. The glucose/mannose and xylose/arabinose ratios were found to be around 3.5 for both Portuguese and Nordic pines. Finally, kraft pulping of Pinus pinaster was found to affect drastically galactose, mannose and arabinose

Toxicity reduction and biodegradability enhancement of cork processing wastewaters by ozonation

Biodegradability enhancement and detoxification of cork boiling wastewater (CBW) are required for the successful implementation of biological treatment options. We studied the possibility of achieving these goals through ozonation pre-treatment by experimenting on the effect of ozone dose and pH. The CBW used had a pH of 5.81, a chemical oxygen demand (COD) of 1,865 mg L-1, a biochemical oxygen demand (BOD5) of 498 mg L-1 and total phenol (TP) and tannin compounds concentrations of 523 and 399 mg L-1, respectively. The ozone doses ranged from 0.27 to 2.63 for the O-3(applied)/COD0 ratios with samples at natural pH and set to 3.33 and 9.96. Ozonation allowed the BOD20/COD ratio (biodegradability index) to increase from 0.37 to 0.63 and a toxicity reduction from 3.08 to 1.24 TU (Microtox). The corresponding removals obtained were 15.2-62.0%, 38.4-83.2% and 56.7-92.1% for COD, TP and colour, respectively. The best outcome of ozonation pre-treatment requires O-3(applied)/COD0 ratios over 1.5 and an acid pH. The increase of TP removals with ozone dose at acid pH led to biodegradability enhancement and CBW detoxification. However, for similar conditions the highest COD removals were obtained at alkaline pH due to the hydroxyl radicals' high oxidation ability but lack of selectivity

Investigation of lab-scale horizontal subsurface flow constructed wetlands treating industrial cork boiling wastewater

The feasibility and treatment efficiency of horizontal subsurface flow constructed wetlands (HSFCW) was assessed for the first time for cork boiling wastewater (CBW) through laboratory experiments. CBW is known for its high content of phenolic compounds, complex composition of biorecalcitrant and toxic nature. Two lab-scale units, one planted with Phragmites australis (CWP) and one unplanted (CWC), were used to evaluate the removals of COD, BOD, total phenolic compounds (TPh) and decolourization over a 2.5-years monitoring period under Mediterranean climatic conditions. Seven organic and hydraulic loading rates ranging from 2.6 to 11.5 g COD/m2/d and 5.7e9.1 L/m2/d were tested under average hydraulic retention time (HRT) of 5 ± 1 days required due to the CWB limited biodegradability (i.e., BOD5/ COD of 0.19). Average removals of the CWP exceeded those of the CWC and reached 74.6%, 91.7% and 69.1% for COD, BOD5 and TPh, respectively, with respective mass removals rates up to 7.0, 1.7 and 0.5 (in g/m2/d). Decolourization was limited to 35%, since it mainly depends on physical processes rather than biodegradation. CBW concentration of nine phenolic compounds ranged from 1.2 to 38.4 mg/L (for the syringic and ellagic acids, respectively) in the raw CBW, with respective removals in the CWP unit ranging from 41.8 to 76.3%, higher than those in the control unit. Despite CBWhigh concentration of TPhs (average of 116.3 mg/L), the HSFCW reached organic load removals higher than those of conventional biological treatment methods.info:eu-repo/semantics/publishedVersio