Research Articles

Pulp mills are making increasing efforts to reduce fossil fuel use and carbon dioxide emissions. Lime kilns, which are typically fired with fuel oil or natural gas, use the most fossil fuel in modern pulp mills. A modern kraft pulp mill can be fossil fuel-free during normal operation if fossil-based lime kiln fuels are substituted with renewable alternatives. This study compared the production and use of various renewable fuels, namely, hydrogen, producer gas, torrefied biomass, lignin, and pulverized biomass, in lime kiln operations in a 1.5 Mt/a kraft pulp mill in South America to define the techno-economic optimum for the fossil fuel-free operation of the pulp mill. The attractiveness of each of the concepts was dependent on local conditions and especially the prices of fossil fuels and electricity. The results showed, however, that feasible options exist for the replacement of fossil fuels in lime kiln operations.

Levulinic acid (LA) is an important platform compound that can be obtained from biomass resources. Using corncobs as the raw material that had already removed the hemicellulose, this work studied the relevant hydrolysis kinetics. The kinetic experiments were performed at various temperatures in the range of 150 °C to 180 °C and sulfuric acid concentrations between 0.2 mol/L and 0.8 mol/L in a reactor designed by the authors. The highest yield of LA was obtained at 150 °C and 0.8 mol/L H2SO4 at 58.0 mol%. A new simple kinetic model that consists of four first-order reactions was proposed; the model assumes that humins can be only converted from 5-hydroxymethylfurfural (5-HMF). A modified parameter fitting method that contained equality constraints and a weighted objective function was applied in this study. The kinetic model was in excellent agreement with the experimental data.

The phthalation of bagasse was investigated comparatively with the three main isolated components in 1-allyl-3-methylidazium chloride (AmimCl) to reveal the reaction behavior of bagasse. In the first two parts, the detailed changes of cellulosic and hemicellulosic components in bagasse were elucidated during phthalation. In Part 3, the phthalation of lignins was performed in AmimCl with various ratios of phthalic anhydride/lignins from 10 to 50 mmol/g. The phthalation degree ranged from 41.1% to 68.8% for the phthalated lignins. The aliphatic hydroxyls of lignins were more easily phthalated than the phenolic hydroxyls as revealed by 31P nuclear magnetic resonance (NMR) analysis. Fourier transform infrared spectroscopy (FT-IR) and two dimensional (2D) heteronuclear single quantum correlation (HSQC) confirmed the attachment of phthaloyl group onto lignins. Severe degradation of lignin macromolecules was found at high ratios of phthalic anhydride/lignins (30 to 50 mmol/g) by gel permeation chromatography (GPC) analysis. These results provide a detailed understanding of reaction behaviors of lignins during bagasse phthalation, which are beneficial to prepare composites based on phthalated lignocellulose with better properties.

The effect of particle pretreatments on the biodeterioration of wood-plastic composites (WPCs) was investigated. WPCs made from untreated and pretreated frond midrib particles of date palm were used. Before the addition of a coupling agent, the wood particles were pretreated or extracted with either cold or hot water and mixed with polypropylene to produce panels, which were then superficially inoculated with an ascomycete’s fungus Trichoderma harzianum T6776. The WPC surfaces were studied using scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDX) measurements. In comparison with the control, an intensive growth of T. harzianum hyphae was found over the WPC surface manufactured from untreated date palm midrib particles with the colonies clearly visible. The pretreatments of date palm particles reduced the growth of T. harzianum in comparison with the control and untreated particles. The results suggested that particle pretreatments could be a suitable way to limit the growth of molds over WPC surfaces made from date palm midrib.

Cellulose nanofibrils (CNF) were investigated as a binder in the formulation of particleboard (PB) panels. The panels were produced in four different groups of target densities with varying amounts of CNF binder. The produced panels were then tested to determine the modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), water absorption (WA), and thickness swelling (TS) properties. Density gradients through the thickness of the panels were evaluated using an X-ray density profiler. The effect of drying on the strength development and adhesion between CNF and wood particles (WP) was investigated, and the effect of surface roughness on the wood-CNF bonding strength was evaluated through lap shear testing and scanning electron microscopy. It was found that at lower panel densities, the produced samples met the minimum standard values recommended for particleboard panels. Medium-density panels met the standard levels for IB, but they did not reach the recommended values for MOR and MOE. The possible bonding mechanism and panel formation process are discussed in light of microscopic observations and the results of lap shear tests were presented.