Search

During mechanical defibration of wood, a minor fraction of the wood mass is dissolved in the process water. These dissolved substances represent an extra energy demand when they are treated in the mill's wastewater treatment plant. Galactoglucomannan, the main hemicellulose in spruce, can be recovered from thermomechanical pulp mill process water by a process based on microfiltration (MF) and ultrafiltration (UF). The purpose of this work was to study the scale-up of the process from laboratory scale to continuous industrial scale. MF was first studied in the laboratory, and then combined with UF in a continuous pilot process on-site at a pulp mill. The data obtained were used to estimate the cost of the membrane processes for galactoglucomannan recovery which was found to be about €1160 per ton hemicelluloses. [ABSTRACT FROM AUTHOR]

A method is proposed for producing fatty acid esters of thermomechanical pulp (TMP) using fatty acids of intermediate chain length (C6-C12). The end objective is to use a stream of fatty acids produced via refining tall oil from Alberta's pulping mills. Depending on the degree of modification, these treated materials can serve either as reinforcement or as copolymers in composite applications. The effect of reaction conditions—reaction time, reaction temperature, fatty acyl concentration, and fatty acid chain length—on the degree of substitution of the pulp samples was studied. The reaction conditions were applied for each fatty acyl chloride and the pulp samples were characterized using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, force tensiometry, time-of-flight secondary ion mass spectroscopy, atomic force microscopy, and thermal gravimetric analysis. The degree of substitution (DS) plateaued after two hours at a concentration of 0.25 M of hexanoyl chloride. These conditions were used for the other systems studied. The esterification of the pulp samples was heterogeneous as evident from both the AFM and SIMS images, because of the presence of lignin on the surface. Nevertheless, based on adhesion forces measured using AFM, the surface of the modified pulp samples was less polar. This was also confirmed via contact angle measurements. Also, the changes in chemical functionality were studied using FTIR and XPS with the appearance of peaks characteristic of C˭O (esters) and an increase in intensity of the alkyl shifts, respectively. Finally, it was found that esterification significantly improved the thermal properties of the pulp samples. [ABSTRACT FROM PUBLISHER]

Douglas-fir heartwood thermomechanical pulp was treated with laccase enzymes at 25 and 50°C with and without added oxygen. The treated pulps were bleached with hydrogen peroxide at increasing alkali charges. Laccase treatments without added oxygen increased bleached brightness by 1.5-2.5 pts ISO, and decreased hydrogen peroxide consumption by 15-20%. The enzyme treatments were not enhanced when supplemented with oxygen. When the effectiveness of four different laccase enzymes was compared for the treatment of Douglas-fir heartwood thermomechanical pulp, there were no significant differences found in the performance among the enzymes. Possible explanations for the observed results are given. [ABSTRACT FROM AUTHOR]

Dissolved aromatic substances in water suspensions of unbleached and peroxide‐bleached spruce thermomechanical pulp (TMP) were isolated by sorption on XAD‐8 resin and fractionated into lignin and oligomeric aromatic substances (OAS). The fractions were characterized by chromatographic (GC and HP‐SEC) and spectrometric (FT‐IR, 13 C‐NMR, GC‐MS) methods, as well as by GC after direct on‐line pyrolysis and thermally assisted hydrolysis and methylation. The dissolved lignin in unbleached TMP water was structurally similar to spruce milled‐wood lignin (MWL), but its average molar‐mass was lower and the mass distribution more narrow. The oligomeric aromatic substances included phenolic dimers, trimers, and tetramers that were structurally different from those of MWL. After peroxide bleaching the amount of dissolved semipolar (MTBE) extractives and oligomeric aromatic substances was much lower. The amount of dissolved lignin from wood fibers was, on the contrary, much higher. The lignin released from TMP after bleaching was extensively oxidized and had a slightly higher average molar‐mass than lignin released from unbleached TMP. [ABSTRACT FROM AUTHOR]