Volume 16 Issue 1

Biochar was prepared by dry torrefaction of wood meal in a batch reactor under pressurized conditions. The biochar prepared at 340 °C (WMB-340) showed a higher heating value (HHV) of 30.5 MJ/kg, and it was employed to co-combust with anthracite coal (AC) with the HHV of 28 MJ/kg. The WMB-340 underwent two combustion stages, while the AC only showed one combustion stage. The combustion of AC was promoted by WMB-340 at temperatures higher than 490 °C, indicating the existence of a synergetic effect during co-combustion. Blending AC with 10% WMB-340 had no obvious effect on the combustion stage of AC. However, three combustion stages existed when blending more than 10% WMB-340 with AC. The activation energy of AC blended with 10% WMB-340 was 84.5 kJ mol-1, much lower than that of AC (179.3 kJ mol-1), indicating a lower energy for initialization of the blend. Therefore, AC blended with 10% WMB-340 was the optimal ratio for co-combustion in this study.

Lignin is a sustainable raw material with a high potential for use in the production of renewable products. While the market for lignin is slowly growing, lignin recovery via acid precipitation during the kraft pulping process requires the addition of chemicals that will impact the chemical balance of the pulp mill. This negatively affects both the environmental and business operations. Utilizing existing process streams as a source of chemicals will allow the mill to close the chemical loop and reduce emissions, which will have positive environmental impacts. This study investigated the internal production of sulphuric acid (H2SO4) and carbon dioxide (CO2) for use in lignin separation (also called extraction) at a Swedish kraft pulp mill. The process simulation tool CHEMCAD was used to model and analyze the wet gas H2SO4 (WSA) process to produce H2SO4. The chemical absorption process using monoethanolamine (MEA) to capturing CO2 was also analyzed. The utilization of the sulphur-containing gases to produce H2SO4 can generate an amount that corresponds to a significant lignin extraction rate. The CO2 available in the flue gases from a mill well exceeds the amount required for lignin extraction.

An analysis was conducted of the effects of cutting conditions in the cross-cutting of wood using circular saws. Gradual wear of the saw blade cutting wedges impacted the entire cutting process. Two different types of circular saw blades were used. One blade type featured sintered carbide tips and 54 saw blade teeth, whereas the other had high-speed steel with 56 teeth; both saw-blades were 600 mm in diameter with a rake angle of 20°. The two wood species were spruce (Picea abies) and beech (Fagus sylvatica). During sawing, the timber was fed at a velocity of vf = 6 and 12 m·min-1. The cutting speed (vc) was set at 60 m·s-1, 70 m·s-1 and 80 m·s-1. The saw blades were coated with three types of PVD coatings. The least energy intensive saw blade was a sintered carbide-free saw blade with a coating (AlTiN) at a displacement speed of 12 m·min-1 and cutting speed of 60 m·s-1 with a power of 1310,63 W. Any change of a saw blade considerably affected torque for all the wood species, so a particular type of saw blade will always have an impact on torque. Other parameters distinctively and individually influenced the process of wood sawing.

Bacterial cellulose (BC) was synthesized by Acetobacter xylinum using a carbon source of coconut shell hydrolysate, which was treated with an ultra-low concentration of sulfuric acid. The coconut shell was found to contain 57.13% holocellulose and 27.42% lignin. The effect of sulfuric acid concentration, reaction temperature, and reaction time on hydrolysis of coconut shell were evaluated by response surface methodology. The reducing sugar concentration was 8.39 g/L under the predicted optimum treatment at 200 °C for 32 min with a solution of 0.07% sulfuric acid. The holocellulose conversion rate was 56.1% at this condition. In a detoxification process using calcium hydroxide and activated carbon, furfural and hydroxymethylfurfural in the hydrolysate were almost completely removed, whereas formic acid and acetic acid levels decreased by 30%. After cultivation for 7 days at the reducing sugar status of 5 g/L, the BC production in medium with the detoxified hydrolysate could reach 1.66 g/L. After fermentation for 21 days, BC yield in medium using composited carbon source (20 g/L) of glucose and hydrolysate was 5.30 g/L. Structural analysis showed that BC obtained from medium of control and detoxified hydrolysate exhibited similar properties. This work provided a potential method for BC production.

Lignocellulosic biomass was delignified by combining physical and chemical pretreatment techniques. Then, a polysulfone-polyethylene glycol blend, which was compatible with the lignin-free biomass (0 wt% to 3.0 wt%), was used to fabricate composite membranes. The presence of hydroxyl groups after the pretreatment was evaluated via Fourier transform infrared spectroscopy. The rheology of the polymer solutions was assessed via the viscometric method. Also, the hydrophobicity of the fabricated membranes was determined using contact angle and porosity measurements. The fabricated membranes with near superhydrophobic properties (a contact angle of approximately 140°) based on this study revealed that contactor systems and biomedical applications would benefit from this modification.

When cutting wood, heat is generated in the cutting zone and in the gullet due to the friction between the teeth of the blade and the material that is being cut. Since the wood is hydrophilic, the saw blade cannot be cooled with liquids, as is usual when cutting metals. The only way to remove the heat from the source is by conductivity to the centre of the saw blade and then by convection into the air. This research presents an analytical model to calculate the natural frequencies of circular saw blades exposed to different temperature distributions. The model confirmed experimental findings of many authors, i.e. the heating of the saw blade cutting edge reduces its natural frequencies, the rate of the reduction depending on the temperature difference between the cutting edge and the rest of the blade and on the shape of the temperature distribution. In contrast, heating the centre of the saw blade increases its natural frequencies, the rate of increase depending on the temperature difference and the shape of the temperature distribution. With the presented model, the most favourable temperature distribution can be calculated from the point of view of the critical saw blade speed, which can be achieved by heating or cooling the centre of the saw blade.

Tubular particleboard is made of wood shavings through high-temperature extrusion. It is a particleboard with round thru-holes aligned lengthwise in the board. This paper discussed the development of multidimensional-interface extrusion technology. Process parameters were determined for the production of five different particleboard thicknesses of 24 mm, 28 mm, 35 mm, 40 mm, and 60 mm. The authors also tested the physical and lengthwise mechanical properties of the tubular particleboards. The manufactured tubular particleboards had the following properties, with respect to the above thicknesses: MOR of 4.9 to 2.2 MPa; MOE of 380 to 250 MPa; IB of 0.54 to 0.37 MPa; TS of 1.7 to 0.8%; and LDC of 9.1 to 5.2%. All met the values specified in the standards LY/T 1856 (2009) and GB/T 34717 (2017). MOR was ≥1 and ≥1.7; IB was ≥0.1 and ≥0.17; TS was ≤5; LDC was ≤15. It was concluded that as the thickness of the board increased, the mechanical properties decreased, but the physical properties increased. When compared to traditional extruded tubular particleboards, the multidimensional-interface extruded tubular particleboards had excellent physical and lengthwise mechanical properties. In addition, the lengthwise mechanical properties were similar to flat-pressed tubular particleboard, and ultra-thick particleboard can be produced.

To develop a waterborne wooden flooring coating, the existing problems of the current waterborne coated wooden floorings were analyzed, and their corresponding solutions were considered. In this paper, based on the final effects of a novel waterborne UV wooden floor coating, the authors used a waterborne UV coating with different solids contents, as well as finishing and drying technology to treat the substrate with different tree species. According to the LY/T standard 1859-2009 (2009) and Q/YFL standard 0035-2018 (2018), the performance of the varnish film of the waterborne UV wooden floor coating was determined. The waterborne coating wooden flooring processes and effects of the varnish film were optimized to provide excellent performance. The performance of the varnish film and the developed waterborne coated wooden flooring met the standard requirements: the surface wear-resistance was less than or equal to 0.15 g/100r, the varnish film hardness was greater than or equal to H, the level of varnish film adhesion was less than or equal to 2, and the total volatile organic compounds was less than or equal to 20 µg/m3. This study provided a demonstration and basis for wooden flooring companies to develop a waterborne wooden floor coating.

This paper presents an application of an open architecture control system implemented on a multi-axis wood computer numerical control milling machining center, as a digital twin control. The development of the digital twin control system was motivated by research and educational requirements, especially in the field of configuring a new control system by “virtual commissioning”, enabling the validation of the developed controls, program verification, and analysis of the machining process and monitoring. The considered wood computer numerical control (CNC) machining system is supported by an equivalent virtual machine in a computer-aided design and computer-aided manufacturing (CAD/CAM) environment, as well as in the control system, as a digital twin. The configured virtual machines are used for the verification of the machining program and programming system via machining simulation, which is extremely important in multi-axis machining. Several test wood workpieces were machined to validate the effectiveness of the developed control system based on LinuxCNC.

The aim of this research was to study the effect of chipping method on geometry of particles obtained from date palm frond as a lignocellulose residue. For this purpose, date palm fronds were chipped with four different equipment: chipper-flaker, chipper-hammer mill, flaker-hammer mill, and chipper-flaker-hammer mill. The geometry of the particle including particle size, particle size distribution, shape, and aspect ratio were investigated. The results showed that maximum weight percentage (more than 40%) was related to the particles sizes of +30/-40 mesh for all chipping methods and more than 50% of all generated particles had a needle shape. In the chipper-hammer mill method, both the weight percentage of useable particles in particleboard and the particle percentage of the rectangle or nearly rectangle particle were higher. Thus, the chipper-hammer mill method was judged to be the best method.