Effects of raw material moisture content,densification pressure and temperature on some properties of Norway spruce pellets

In order to study the pelletising process, Norway spruce sawdust pellets were produced under strictly controlled conditions on a laboratory scale. The aim of the work was to investigate how the moisture content of raw material and the densification parameters, pressure and temperature, affect compression strength, dry density and moisture uptake of the formed pellets. In the experiments performed, temperature (26–144 °C), moisture content (6.3–14.7 wt.% of d.b.) and pressure (46–114 MPa) were the factors which varied according to a prescribed central composite design. The relationships between the factor settings and the responses (dry density, moisture uptake and compression strength) were evaluated by multiple linear regressions.In the present study, it was found that high compression strength was strongly correlated with the density of the pellets. High temperature (at least up to 144 °C) and low moisture content at the start of compression (down to 6.3 wt.% of d.b.) increased the dry density of the pellets. Remarkably, compression force had very little effect in the tested range of 46–114 MPa, indicating that pressure in the die does not need to be higher than 50 MPa.Similarly, compression force had very little effect on moisture uptake in the pellets. The least moisture uptake occurred when the pellets were produced at 90 °C.     

Physicochemical properties of fuel shales

Current economic conditions call for innovative products such as coke for the electrode industry, graphite, and fullerenes. To that end, the physicochemical properties of fuel shales must be determined. Attention focuses on shales from the Pribaltiisk Basin (Leningrad field). The goals of the experiment are to determine the physical properties of the shales (moisture content, ash content, actual and apparent density, porosity), the optimal briquetting conditions, and the calorific value of the briquets. The influence of the fractional composition and moisture content on briquet strength is studied. The influence of the heating conditions on the physicochemical properties in the shales is considered. The briquets are heated in pipe furnaces with uncontrolled and controlled atmospheres, in the temperature range 200–1000°C. It is found that the increasing the briquetting pressure (from 10 to 15 MPa) and moisture content (from 11.6 to 37%) improves the briquet strength, while adding coal fines (4 wt %) and reducing the moisture content (to 23%) improves the calorific value of the briquets. Semicoking begins at 400°C. Further heating increases the yield of gases and reduces the yield of semicoke. After pressing, the shale fines may expediently be processed by heat treatment to obtain a graphite material.     

Preparation and properties of biocomposites composed of epoxidized soybean oil,tannic acid,and microfibrillated cellulose

As a new biobased epoxy resin system, epoxidized soybean oil (ESO) was cured with tannic acid (TA) under various conditions. When the curing conditions were optimized for the improvement of the thermal and mechanical properties, the most balanced properties were obtained when the system was cured at 210°C for 2 h at an epoxy/hydroxyl ratio of 1.0/1.4. The tensile strength and modulus and tan δ peak temperature measured by dynamic mechanical analysis for the ESO–TA cured under the optimized condition were 15.1 MPa, 458 MPa, and 58°C, respectively. Next, we prepared biocomposites of ESO, TA, and microfibrillated cellulose (MFC) with MFC contents from 5 to 11 wt % by mixing an ethanol solution of ESO and TA with MFC and subsequently drying and curing the composites under the optimized conditions. The ESO–TA–MFC composites showed the highest tan δ peak temperature (61°C) and tensile strength (26.3 MPa) at an MFC content of 9 wt %. The tensile modulus of the composites increased with increasing MFC content and reached 1.33 GPa at an MFC content of 11 wt %. Scanning electron microscopy observation revealed that MFC was homogeneously distributed in the matrix for the composite with an MFC content of 9 wt %, whereas some aggregated MFC was observed in the composite with 11 wt % MFC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Optimization of thermopressing conditions for the production of binderless boards from a coriander twin‐screw extrusion cake

A deoiled press cake resulting from twin‐screw extrusion of coriander fruits was used as a raw material for the production of self‐bonded boards. The operating parameters for thermopressing were varied and include the applied pressure (19.6–39.2 MPa), molding time (60–300 s), and molding temperature (155–205 °C). The optimized process conditions (21.6 MPa, 300 s, 205 °C) resulted in a board with a density of 1323 kg/m³, a flexural strength of 23 MPa, a modulus of elasticity of 4.4 GPa, and a thickness swelling of 31%. The thickness swelling was effectively reduced to 20% through the application of a heat treatment at 200 °C after thermopressing. A variation of the moisture content of the press cake between 3 and 8% showed that increased moisture contents do not lead to improved mechanical properties of the resulting board and further induce internal fracturing of the board during thermopressing. The manufactured binderless boards may act as environmentally friendly alternatives to commercial wood‐based boards such as oriented strand board and particleboard. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44650.     

Ultraporous poly(lactic acid) scaffolds with improved mechanical performance using high‐pressure molding and salt leaching

A novel processing technique, i.e. high‐pressure compression molding/salt leaching, was developed to fabricate ultraporous poly(lactic acid) (PLA) scaffolds. The optimized composition was studied in relation to the porosity, pore morphology, thermal property, and mechanical performance of the PLA scaffolds. At a porogen (CaCO₃) content of 90 wt %, the scaffolds have an interconnected open pore structure and a porosity above 80%. It was truly interesting that the structural stability of high‐pressure molded scaffolds was remarkably improved based on the fact that its glass transition temperature (83.5°C) increased about 20°C, as compared to that of the conventional compression‐molded PLA (60°C), which is not far from physiological temperature (～37°C) at the risk of structural relaxation or physical aging. More importantly, the mechanical performance of PLA scaffolds was drastically enhanced under optimized processing conditions. At pressure and temperature of 1000 MPa and 190°C, the porous PLA scaffolds attained a storage modulus of 283.7 MPa, comparable to the high‐end value of trabecular bone (250 MPa) ever reported. In addition, our prepared PLA scaffolds showed excellent cellular compatibility and biocompatibility in vitro tests, further suggesting that the high‐pressure molded PLA scaffolds have high potential for bone tissue engineering applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3509–3520, 2013     

Effect of mechanical thermal expression drying technology on lignite structure

Mechanical thermal expression (MTE) is a developing nonevaporative lignite dewatering technology. It has been proved to be effective to dewater high moisture content in low-rank coals via the application of mechanical force and thermal energy at elevated temperatures. In this paper, the dewatering behavior of the Xiaolongtang lignite in Yunnan province, China during the MTE process was studied with three process parameters: time, temperature, and pressure. Meanwhile, the mechanism was also explored of how variations in temperature and pressure during the MTE process affect the surface oxygen functional groups and pore structure, which was mainly conducted by means of Fourier transform-infrared spectrometer (FTIR) and mercury intrusion porosimetry (MIP). Increases in MTE temperature and pressure resulted in significant reductions in residual moisture content and moisture-holding capacity, along with the increase in fixed carbon content and content reductions of other elements, especially oxygen content, this could be largely attributed to the destruction of the surface oxygen functional groups and porosity in the lignite. Technologically, the optimal conditions for temperature and pressure are 150–220°C and 6–10?MPa. The residual moisture content of the lignite treated by MTE at 200°C, 10?MPa is lower than 8%; the dewatering rate reaches over 76% with the calorific value being approximately 22?MJ/kg. Carboxyl and hydroxyl groups break down at drying temperatures above 120°C and constant applied pressure 10?MPa; with the pore volume significantly reduced, only few pores (diameter?相似文献   

Preparation,modification, and characterization of acrylic cements

Acrylic cements with different compositions were prepared by mixing the solid part (composed of poly(methyl methacrylate), PMMA, and benzoyl peroxide, BPO) and the liquid part (composed of methyl methacrylate, MMA, and N,N‐dimethyl‐p‐toluidine, DMPT), modified by addition of hydroxyapatite (HA) and ammonium nitrate (AN) and characterized by measuring thermal and mechanical properties. Three sets of samples were prepared. For B‐group, the total amount of solid including HA was constant but the PMMA to HA ratio was varied. For C‐group, polymer/monomer ratio was constant and varying amounts of HA was added. For D‐group, polymer/monomer ratio was kept constant and AN was added in varying amounts. Effects of these composition changes on the properties of the cement such as setting time, curing temperature, tensile and compression strength, and deformation were examined. For B‐group samples, no linear change was observed in thermal (curing temperatures were all quite high) and mechanical (between 27 and 19 MPa for tensile, and 98 and 116 MPa for compression strength) properties upon change of HA content with change in solid/liquid ratio. For C and D‐group samples, a continuous decrease in curing temperature from 114 to 101°C and from 94 to 73°C was observed upon increasing HA and AN contents, respectively. Also, a linear relation was observed in compression strength (from 98 to 111 MPa) and in tensile strength (from 27 to 21 MPa) upon HA addition, and in the compression strength (from 103 to 85 MPa) and in the tensile strength (from 22 to 17 MPa) with NA addition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3631–3637, 2006     

Synthesis,fabrication, mechanical,electrical, and moisture absorption study of epoxy polyurethane–jute and epoxy polyurethane–jute–rice/wheat husk composites

Bisphenol‐C‐epoxy‐toluene diisocyanate polyurethane (PEBCT) has been synthesized and used for the fabrication of jute, jute–rice husk (JRH), and jute–wheat husk (JWH) composites. The composites have been fabricated by hand lay‐up technique under a hydraulic pressure of 30.4 MPa at 135°C for 2.5 h. PEBCT‐J, PEBCT‐JRH, and PEBCT‐JWH possess respectively, tensile strength of 37.4, 9.5, and 14.7 MPa, and flexural strength of 39.6, 12.9, and 21.3 MPa, electric strength of 1.3, 1.8, and 1.9 kV/mm and volume resistivity of 1.40 × 10¹³, 1.84 × 10¹³, and 1.91 × 10¹³ ohm cm. Tensile strength and flexural strength have decreased, while electric strength and volume resistivity are improved upon hybridization. PEBCT‐JWH has better interfacial bond strength and stiffness as compared to PEBCT‐JRH. Moisture uptake behavior of PEBCT‐J in water, 10% HCl and 10% NaCl at room temperature is quite different. Equilibrium moisture content of PEBCT‐J in 10% NaCl (5.5%) is almost half of those in water (11.3%) and 10% HCl (13.6%) environments. Equilibrium time for saline environment is also comparatively low. Equilibrium moisture uptake in boiling water has increased 1.84 times, while equilibrium time has decreased 15.3 times. The composites may be useful for low load bearing in construction industries and for marine applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of superheated steam treatment on moisture adsorption and mechanical properties of pre-dried rubberwood

Abstract

Rubberwood (Hevea brasiliensis) was treated with superheated steam (140–160?°C) for 1–3?h and then its adsorption ability, mechanical properties, and color changes were investigated. The results of adsorption show decreased equilibrium moisture content (EMC) for all heat-treated cases throughout the hygroscopic range. The Hailwood–Horrobin model was used to analyze the sorption isotherms and determine the monolayer and polylayer moisture contents for untreated and heat-treated rubberwood. The monolayer moisture content clearly decreased with treatment temperature and duration, whereas the reduction in polylayer moisture was relatively smaller. Moreover, the least density of water adsorption sites was found in wood after treatment at 160?°C for 3?h, indicating this as the cause for reduced equilibrium adsorption. All treatment conditions had improved mechanical properties, including compression parallel-to-grain, hardness, and tensile strength. The total color difference of the wood surface increased with increasing temperature and treatment duration.     

Influence of carbonisation on selected engineering properties of carbon resin electrodes for electrochemical treatment of wastewater

In this study, effects of selected factors on selected properties of carbon resin electrodes (CRE) have been investigated. CRE were developed from used dry cells and resin using non‐heat‐treatment process. Selected properties (density, electrical resistance, microstructure, hygroscopy, stability moisture content, compressive and flexural strength) of the electrodes were monitored and effects of carbonisation temperature, carbon particle size, and compaction pressure on these properties were studied. The study revealed that the density of CRE was in the range of 1.33 to 1.59 g/cm³, compressive strength ranged from 36.56 to 43.81 MN/m², flexural strength, moisture content, and swelling were in the range of 6.76 to 8.10 MN/m², 0.84–0.93%, and 6.04–9.30%, respectively. In all cases electrical resistance and density of CRE decreased with increasing carbonisation temperature at various operational factors (particle size, compacting pressure, and percentage of the resin used). Also, it was revealed that carbonisation of CRE from 30 to 220°C reduced specific electrical resistance and density from 1.85 to 1.29 × 10^?1 Ω/cm and from 1.35 to 1.24 g/cm³, respectively, but carbonisation temperature had no significant effect on wetness, compressive and flexural strength, stability, and moisture content of the electrodes. Estimated costs revealed that cost of producing CRE was cheaper ($13.25/m) than that of heat‐treated electrodes ($33.33/m). It was concluded that carbonisation temperature, particle size, compacting pressure, and percentage of the resin used are important factors in the development of CRE with lower specific electrical resistance.     

Pressureless joining of SiC ceramics with magnesia-alumina-silica glass ceramics

Liquid phase sintered SiC ceramics were joined using magnesia-alumina-silica (MAS) glass-ceramic fillers without applied pressure. Four different filler compositions with 9.3–25.2 wt.% MgO, 20.7–33.6 wt.% Al₂O₃, and 49.2–68.1 wt.% SiO₂ were studied. The effects of filler composition and joining temperature (1450–1600°C) on the joint strength were investigated. All compositions exhibited an optimum joining temperature at which the maximum joint strength was obtained. A low joining temperature resulted in poor wetting of the SiC substrate due to the high viscosity of the filler. Whereas a high joining temperature caused dewetting and large unfilled sections in the interlayer due to the deleterious interfacial reactions. The joint strength was inversely proportional to the interlayer thickness, which was a function of filler composition and joining temperature. The SiC ceramic joined at 1525°C with MgO-25 wt.% Al₂O₃-60 wt.% SiO₂ filler exhibited a four-point bending strength of 286 ± 40 MPa.     

Pelletised fuel production from palm kernel cake

Biomass is an important source of renewable energy. Worldwide, the palm oil industry generates large amounts of waste materials, such as shells, fibres and palm kernel cake, which can be used for power generation. Processing the palm kernel cake into a uniform fuel through pelletisation will be an attractive option — assessing the suitability of this process was the main objective of this research. Extensive analytical and pelletisation tests were performed to evaluate the physical properties of pellets produced from this material. The variables explored included the pelletisation pressure, temperature, fuel moisture and the effect of binders, which all had significant effects on density and tensile strength. The most favourable conditions for pellet production were a pressure of 9338 psi/64.38 MPa, a temperature of 80-100 °C and a fuel moisture content of 7.9%. These pellets had densities of 1184-1226 kg/m³ and tensile strengths of 930-1007 kPa. Adding small amounts of caustic soda (1.5-2.0wt%) to the palm kernel cake under these conditions increased the tensile strength to 3055 kPa, whereas starch additives were not found to be effective binders. It is estimated that the production of palm kernel cake pellets with 2 wt.% of the caustic soda binder would cost approximately £28-47/tonne.     

Preparation study for the low thermal expansion spodumene/mullite composites

In this work, spodumene/mullite ceramics with low thermal expansion were successfully prepared from spodumene, quartz, talc, and clay. The effects of spodumene content and sintering temperature on the mechanical properties of spodumene/mullite ceramics were investigated. The formed phases were then detected by X-ray diffraction analysis and the microstructures of the sintered bodies were determined by scanning electron microscopy. The interaction effects of the spodumene content and sintering temperature on the apparent porosity and bulk density were studied by response surface methodology. The results demonstrate that an appropriate sintering temperature and spodumene content can promote densification, improve the mechanical properties, and reduce the coefficient of thermal expansion (CTE) of spodumene/mullite ceramics. At the spodumene content of 40 wt.%, the sintering temperature of 1270°C, and the holding time of 90 min, the bending strength was 60.45 MPa, the CTE was 1.73 × 10^–6/°C (α_{[25–650°C]} < 2 × 10^–6/°C), the bulk density was 2.28 g cm^-3, and the apparent porosity was 0.43%. Therefore, this study was of guiding significance for reducing the production cost of spodumene low thermal expansion ceramics and improving product quality.     

Microwave assisted barking of frozen wood

Thawing pulpwood with microwave energy could be an effective means to improve winter barking operations in Canadian interior mills. Complete bark thawing requires 140 MJ per tonne of wood for average 25 cm diameter logs at 90 mass % moisture, dry basis. However, complete thawing may not be necessary, as warming both spruce and aspen bark from ?20°C to ?5°C, decreases the bark/wood bond strength from 2.5–4.5 MPa to room temperature values of 0.5–1.5 MPa. This improves the economics of winter operation, but the expenditure for capital which has no year-round use is not easily justified. Also the design of safe large-scale microwave generators and applicators remains a technical challenge.     

Preparation and Physicochemical Study of Hybrid Glass-Jute (Treated and Untreated) Bisphenol-C-Based Mixed Epoxy Phenolic Resin Composites

Glass-jute (treated and untreated) composites of mixed matrix materials [epoxy resin of bisphenol-C (EBC) and bisphenol-C-formaldehyde (BCF) of 50 wt.% of glass-jute fibers] have been prepared by hand layup technique at 150°C under 7.6 MPa pressure for 2 h. The hydrophilic character of the jute fibers has been reduced by acrylation of alkali-treated fibers with acrylic acid. Tensile strength increased from 87 MPa to 112 MPa (28.73%) and flexural strength increased from 66 MPa to 89 MPa (34.84%) on alkali treatment and acrylation. Similarly, electric strength increased from 2.71 to 3.89 kV/mm (43.54%) and volume resistivity increased from 1.23 × 10¹² to 1.77 × 10¹² Ω cm (143.90%). The edges of the 5 cm × 5 cm specimens were sealed with matrix material and subjected to distilled water and 10% each of aq. HCl and aq. NaCl solutions at room temperature for a water uptake study. The equilibrium water uptake was reduced drastically from 12.07–7.69% to 6.17–3.39% on acrylation. Similarly, diffusivity was also found to be reduced from 1.99–0.99% to 0.96–0.45%. Drastic reductions in water uptake and diffusivity are due to the replacement of hydrophobic ester groups. The reduction of water uptake is probably due to weak H-bond formation with ester and CH=CH groups, and π-electrons of benzene rings. No effect of boiling water is observed on the stability of the composite. Saturation time in boiling water was reduced twenty-eight/twenty-one times without any damage to the untreated/treated jute-glass composites, respectively.     

Development of empirical drying correlations for ground wood chip and ground wood pellet particles

In this research, the drying rates of ground chip and ground pellet particles of pine were investigated. Pulp wood chips and whole pellets were ground in a hammer mill. Grinder screens with perforations 3.2, 6.3, 12.7, and 25.4?mm were installed in the hammer mill to produce a range of ground particle sizes. Particle size of ground chips had a broad range of 0.25–6?mm, while pellet particles had a smaller range of 0.5–2?mm. Initial moisture contents of ground particles were conditioned to 0.1, 0.3, and 0.5 (dry mass basis) using sprayed water. The moistened particles were dried isothermally in a thin-layer dryer set at the temperatures of 50, 100, 150, and 200°C. Chip particles dried faster than pellet particles of the same particle sizes. In addition to water loss, the particles exposed to a temperature of 200°C lost 3–7% of their dry mass. Smaller particles lost more dry mass than larger particles. The modeling revealed that the drying constants of pellet particles are less than those of chip particles with the same particle size.     

Additional high-energy milling to enhance the performance of porcelain stoneware manufacturing

Porcelain stoneware tile is the best class of ceramic tiles regarding technical performance. Low porosity and high glass content are some of its highlighted characteristics. The manufacturing cost is highly dependent on the feldspar content and the processing flow rate. Certain technical bottlenecks in the manufacturing steps, such as milling, forming, and firing, are intrinsically associated with limitations in the processing properties, such as the dry strength, bulk density, and pyroplastic deformation. In this work, improvements in these properties were achieved using high-energy milling (HEM) after conventional milling (CM). This study was carried out on a pilot industrial scale in the milling stage. Six experimental runs were evaluated. Slurries were spray-dried. The powders were humidified with 6.5% moisture. Specimens were conformed under a specific pressure of 45 MPa. The firing was performed using temperature ranging from 1150 to 1230°C. The use of HEM, in comparison to traditional milling for the similar particle-size distributions, has increased the dry density, +0.2 g.cm⁻³, dry bending strength, +1.0 MPa, and decreased the pyroplastic deformation index, −1.10⁻⁵ cm⁻¹. These results allow an estimated thickness reduction of 10%.     

Preparation and Characterization of Chitosan Coated Surgical Gauze Using Potassium Persulfate as Thermal Initiator

Chitosan powder was extracted from prawn shell via chitin formation by chemical treatment. Chitosan solution (2 wt.%) was prepared in aqueous solution containing ethanoic acid (2 wt.%) along with varying amounts of potassium persulphate as thermal initiator (10 to 50 mg). Surgical gauze was immersed in the chitosan solution for 10–45 min. Coating was carried out at 70–110°C and heating time varied from 30–180 min. Chitosan uptake and the mechanical properties of the chitosan coated surgical gauze, such as tensile strength (TS) and elongation at break (Eb), were measured. Soaking time, curing time, and curing temperature of the surgical gauze were optimized for the preparation of coated gauze over chitosan uptake and mechanical properties. Surgical gauze soaked for 20 min at 90°C for 120 min of curing showed the highest chitosan uptake and TS (9 MPa). Soil burial tests revealed that coated gauze became twisted and almost degraded within 6 weeks of ageing. Water uptake properties of the coated gauze were monitored. Scanning electron microscopic analysis of the surface of the coated gauze found that the coating of chitosan became brittle with the use of higher amounts (50 mg) of thermal initiator.     

Cold sintering of diatomaceous earth

Diatomite, a natural silicate-based sedimentary rock, was densified by cold sintering at room temperature and 150°C under various pressures (100, 200, and 300 MPa) and using different NaOH water solutions (0–3 M). The relative density of cold sintered diatomite can be as high as 90%, a condition that can be achieved by conventional firing only at 1200–1300°C. The cold sintered materials maintain the same mineralogical composition of the starting powder (quartz, glass, and illite) and are constituted by well-deformed and flattened grains oriented orthogonally to the applied pressure. Conversely, an evident phase evolution takes place upon conventional firing with the formation of cristobalite and mullite. The bending strength of cold sintered artifacts can exceed 40 MPa and increases to ≈80 MPa after post-annealing at 800°C, such mechanical strength is much larger than that of conventionally pressed samples sintered at 800°C, which is only ≈1 MPa.     

Gas-Hydrate Formation and Phase Transformations of Adsorbed Water in Kuznetsk Basin Coal

Among the properties of coal that must be studied in order to optimize its preparation for coke production and deep processing are the interactions of adsorbed materials—in particular, water, methane, and carbon dioxide—with its surface. An important aspect of these interactions is phase transformation of the adsorbed materials in the internal porous structure to form hydrate or ordinary ice. In regular coal, a hydrate of carbon dioxide is formed at a CO₂ pressure of 2–4 MPa and temperatures below 10°C, when the moisture content of the coal exceeds the threshold value. However, at the same moisture content, no ice is formed at temperatures between +13°C and –13°C, while decomposition of the hydrate is observed close to the equilibrium curve. For gases that do not form hydrates (helium, nitrogen, argon) in the given temperature and pressure ranges, increasing the pressure to 12 MPa has no influence on the solidification of sorbed water and ice formation.