Mathematical model of the extrusion of peat briquettes

A physicomathematical model of the extrusion of peat briquettes intended for the determination of the following solid fuel quality indices, which depend on the properties of briquetted peat, is presented: heat of combustion, elemental composition, density, uniaxial compressive strength, hardness, and water absorption. An inverse problem related to a search for the conditions of extrusion and the properties of raw materials necessary for ensuring the quality indices of peat fuel specified in the form of initial data was solved. The physicomathematical model developed is based on the results of experimental studies performed under industrial conditions on a crank press with an open matrix and on the interpretation and generalization of published experimental data.     

Briquetting of coal siftings and slacks in the presence of humates

Experimental data obtained in the development of a technology for the production of fuel briquettes from coal siftings and slacks are presented. The effects of the moisture content and the granulometric composition of coal components, the type and concentration of a binding agent, the compacting pressure, and the mode of solidification on the mechanical properties of fuel briquettes were studied.     

An Experimental Study on Binderless Briquetting of Low‐Rank Coals

The potential of binderless briquetting as a means of transforming low‐rank coals into low moisture high grade solid fuel products has been studied. Using two dried low‐rank coals, binderless briquettes with high mechanical strength have been successfully produced through mechanical compression. An increase in heating value was achieved as a result of moisture reduction in the briquettes compared to as‐received coals. The residue moisture content in the briquettes had a predominant effect on briquetting characteristics and there existed an optimum moisture content for the maximum briquettes strength. The chemical structure and wettability of binderless briquettes were analyzed using FTIR and contact angle measurement. The results showed that hydrophobicity and chemical structure significantly affected the briquette properties.     

Fuel briquettes from biomass–lignite blends

In this study, a western Turkish lignite (Kütahya-Seyitömer) was blended with some biomass samples such as molasses, pine cone, olive refuse, sawdust, paper mill waste, and cotton refuse, and these blends was used in the production of fuel briquettes. Blends were subjected to briquetting pressures between 50 and 250 MPa; the ratio of biomass to lignite was changed between 0 and 30 wt.%. The mechanical strength of obtained briquettes was investigated considering shatter index and compressive strength. Effects of the ratio of biomass to lignite and applied pressure on the strength of the briquettes were examined. This study indicated that the mechanical strength of the briquettes produced from Kütahya-Seyitömer lignite can be improved by adding some biomass samples. For example, the presence of paper mill waste increased the shatter index of the briquettes obtained. Similarly, sawdust and paper mill waste increased compressive strength of the briquettes. Water resistance of the briquettes can be augmented by adding olive refuse, cotton refuse, pine cone or paper mill waste.     

Production of fuel briquettes from anthracite fines

Experimental data on the development of a technology for the production of fuel briquettes from anthracite fines, slack coal, and coal slurries available in the Rostov oblast are presented. The effects of the moisture content and particle size distribution of the coal components, the moisture content of the charge, the composition of a binder, the compacting pressure, and the regime of hardening on the technical properties of the fuel pellets were studied. The possibility of obtaining water-resistant briquettes was demonstrated.     

Effect of printing parameters on mechanical properties of extrusion-based additively manufactured ceramic parts

The purpose of this study is to investigate the effect of printing parameters on the physical and mechanical properties of additively manufactured ceramics (alumina and zirconia). Sample parts were obtained by extrusion-based additive manufacturing of a ceramic-binder mixture and subsequent post-processing (debinding and sintering). Their mechanical properties (microhardness, flexural strength, toughness) were measured and correlated with the printing parameters. Part orientation is the most significant factor for microhardness and flexural strength in both ceramic materials. Parts with vertical orientation show higher hardness while horizontal samples show higher flexural strength compared to their respective counterparts. Extrusion velocity was found to be insignificant for hardness and flexural strength. However, a marginal increase in fracture toughness with the increase in the extrusion velocity was observed. The fracture toughness of additively manufactured ceramics shows an increasing trend with elastic modulus and flexural strength and a decreasing trend with hardness and sintered density.     

Densification of water hyacinth — basic data

The briquette-forming ability of water hyacinth (WH), a plant with prolific growth, to produce a fuel wood substitute or for further processing has been investigated. Compared to straw and sawdust, WH can undergo binderless briquetting. Pressure, water content and temperature have a strong influence on the briquette-forming ability of WH. Laboratory trials showed that optimal conditions are achieved between compaction pressures of 80 and 200 MPa, temperatures between 70 and 80 °C and water contents between 8 and 12 wt%. Die ram-extrusion and pellet-mill briquetting presses allow the compaction of WH with acceptable throughputs and with a specific energy consumption of 180 MJ t^?1. The produced briquettes, with a density of 1400kg m^?3 and a compression rate of 1:14, proved to be abrasive-resistant and showed an acceptable compressive strength. The re-expansion behaviour of the briquettes was moderate. The extractable matter of WH does not contribute to the briquette strength. No experimental indication of lignin softening could be found.     

Effect of the pyrolysis process on the physicochemical and mechanical properties of smokeless fuel briquettes

A greater understanding of the physics and chemistry of lignite–biomass briquetting could lead to better briquette performances and cost-effectiveness making these fuels more attractive to both producers and consumers. With this aim, chars obtained from different low rank coals and biomasses (sawdust, straw, olive stone and almond shell) were used to prepare smokeless fuel briquettes and their physicochemical and mechanical properties were studied depending on the pyrolysis conditions. Coal was pyrolysed at temperatures between 500 °C and 700 °C and the temperature chosen to carry out pyrolysis was 600 °C due to the lowest content of sulphur per thermie in the pyrolized material. In order to study the influence of the pyrolysis process on the properties of the briquettes, biomasses were pyrolysed separately at 400 °C and 600 °C and together with the coal at 600 °C of temperature. The materials pyrolysed at 600 °C showed a lower content of volatile matter and a higher calorific value than the standard levels reported in the literature for materials to prepare smokeless briquettes. The briquettes were prepared by mixing the pyrolysed materials with humates as binder and Ca(OH)₂ as sulphur sorbent. The briquetting process was followed by FT-IR, scanning electron microscopy (SEM), CO₂ adsorption and the mechanical properties were tested evaluating their impact resistance, water resistance and compression strength. The best briquettes with respect to the mechanical properties were those prepared with coal and biomasses co-pyrolysed at 600 °C although some of them fixed a higher percentage of sulphur during pyrolysis due to the metal content of the biomasses.     

Development of an aluminum/amorphous nano-SiO2 composite using powder metallurgy and hot extrusion processes

Ceramic nanoparticle reinforced aluminum matrix composites usually exhibit superior mechanical properties when compared to monolithic materials, particularly in severe working conditions such as elevated temperatures. Aluminum matrix nano-composites (AMNCs) are widely used for structural applications in aerospace and automotive industries due to their low density and high strength to weight ratio. The aim of this research was to study the effect of SiO₂ nanoparticles as the reinforcing phase on the mechanical properties of aluminum matrix composites. For this purpose, powder metallurgy and subsequent hot extrusion methods were used to prepare a reference sample and several Al-SiO₂ nano-composite rods, containing 1, 2 and 3 wt% nano-silica. Some sample preparation procedures for the manufacturing process, involved mixing, compaction, sintering, preheating and hot extrusion. Mechanical properties of the developed composites were investigated by macro- and micro-hardness, density measurement, tensile, cold compression and hot compression tests. A scanning electron microscope and an optical microscope were used for microstructural analysis of the composite and monolithic samples before and after the hot extrusion process. Experimental tests on aluminum matrix composites reinforced with nano SiO₂ particles revealed that adding just 1 wt% SiO₂ nanoparticle increases both hardness and tensile strength by 41.8% and 24.8%, respectively. In addition, the mechanical properties were seen to decrease with increases in the SiO₂ weight fraction. Density also decreased as the SiO₂ weight fraction increased. It can therefore be said that based on the findings of this study, the SiO₂ nanoparticle can be used as an effective reinforcing material for developing aluminum matrix nano-composites.     

无烟煤的物理性质对其型煤抗压强度的影响

以无烟粉煤为原料,采用有黏结剂冷压成型方法,制备了几种型煤产品,并对无烟粉煤的显微硬度、可磨性、真密度、视密度、孔隙率最高内在水分和孔结构等物理性质进行了分析测试,重点研究了无烟煤的物理性质对型煤抗压强度的影响.结果表明,随无烟煤的反射率、显微硬度、真密度和视密度等指标的增加与可磨性的降低,型煤抗压强度均显示出增加的趋势,这与高压无黏结剂成型时,型煤强度与显微硬度关系相反.无烟煤的物理性质体现了煤的变质程度,因此,型煤抗压强度也与无烟煤的变质程度密切相关.研究结果还表明,不同煤阶无烟煤的孔结构分布和最高内在水分不尽相同,都影响无烟煤被黏结剂黏结的程度,从而影响无烟煤型煤的抗压强度.     

Physical extruder foaming of poly(lactic acid)—processing and foam properties

The article describes extrusion foaming of poly(lactic acid) (PLA) using carbon dioxide in the supercritical state as foaming agent emphasizing the steps required to establish a stable extrusion process. Low melt strength of PLA plays a role in optimizing processing conditions. The tests included PLA grades of different viscosity in addition to a chain extender. Processing at low temperature is possible due to the plasticizing effect of the CO₂ on the PLA melt and a sufficiently low melt temperature is also a prerequisite in production of stable foams due to improved melt strength. Foams were characterized by density, cell structure, crystallinity, and mechanical properties in compression. Low density, microcellular foams with density down to 20–30 kg/m³ were obtained for three different PLA grades. Varying die temperature and pressure drop rate we can explain observed abrupt drops in density with increasing CO₂ content by the interplay between cell nucleation and gas diffusivity at given temperatures. An effect on melt strength similar to using a chain extender is achieved by lowering the melt temperature at the die. Observed variations in sample crystallinity do not correlate with foam density. The PLA foams have good energy absorption capability. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Processing and physical properties of native grass-reinforced biocomposites

Big blue stem grass fiber-reinforced high density polyethylene powder biocomposites were fabricated using two separate processing schemes: (1) by compounding biofiber with the thermoplastic powder in an extruder and subsequently injection molding the extrusion pellets and (2) by combining biofiber and the powder thermoplastic powder using a modified sheet molding compounding (SMC) line and subsequently compression molding the sheet material. The physical properties including storage modulus, heat deflection temperature (HDT), notched Izod impact strength, and morphology were evaluated with dynamic mechanical analysis, Izod impact strength measurement, and microscopy observation. It was found that compression-molded specimens achieved similar modulus values to injection molded specimens for grass-reinforced high density polyethylene (HDPE) composites. The stiffness of the compression-molded specimens is related to the consolidation state of the samples, which depends on compression molding conditions such as temperature, pressure, and mold type. Compression-molded specimens exhibited a higher HDT and notched Izod impact strength compared to injection-molded samples. Grass fiber-reinforced cellulose acetate butyrate (CAB) biocomposites made with SMC processing had similar physical properties with grass fiber-reinforced HDPE composites, which indicates that natural fiber-reinforced CAB biocomposites have the potential to replace polyolefin-based composites for automotive applications. POLYM. ENG. SCI. 47:969–976, 2007. © 2007 Society of Plastics Engineers.     

MgO–Na2O–P2O5-Based Sintering Additives for Tricalcium Phosphate Bioceramics

Effects of MgO–Na₂O–P₂O₅-based sintering additives on densification, microstructure, hardness, compression strength, and biodegradability of β-tricalcium phosphate (β-TCP) ceramics were studied. Three additive compositions were prepared and introduced into β-TCP. Uniaxially compacted ceramic structures, sintered at 1250°C in air, were characterized. Scanning electron microscopy was used to study the microstructure. The X-ray diffraction technique was used for phase analysis. Results showed that these additives modified the microstructure and improved the sintered density and mechanical properties. An increase of 9% in density, 40% in hardness and 38% in compression strength were achieved. Biodegradation analysis revealed that these additives could tailor the rate of resorption and hardness degradation of β-TCP.     

Investigation of pelletization stage and its role in the formation of catalyst quality indices

The results of complex and systematic investigations of the pelletization stage are generalized by the example of commercial Cu-Zn-Al catalysts of carbon conversion (SNK-2) and methanol synthesis (SNM-U) produced during a period of 1.5 years. Flowability of precipitated Cu-Zn-Al catalyst masses at different stages of their preparation for pelletization as well as the effect of granulometric composition on the flowability are studied. Flowability of the catalyst mass is shown to depend, first of all, on the concentration of the fine fraction (<0.25 mm): it increases with a decrease in the number of fine particles. The statistical data which characterize nonuniformity of the height, diameter, mass and strength of the pellets of commercial SNM-U and SNK-2 catalysts are obtained for 600–1000 pellets (Performance Specifications (TU) provide for estimating the average values based on 30 pellets). The effect of the compacting pressure on the mechanical strength, density, and bulk weight of the pellets is investigated. The effect of the mass humidity and duration of the compacting force increase on the pellet mechanical strength is demonstrated. The coefficient of a linear dependence of the pellet size increase after the compacting load is removed is experimentally determined for precipitated Cu-Zn-Al disperse masses. A porous structure of pellets with different strengths is investigated. The activity of SNM-U and SNK-2 samples produced at different compacting pressures, whose pellets differ in density and strength, is determined. The present study has resulted in specifying the admissible amounts of water and graphite introduced into the process of pelletization. The revealed laws allow producing changes in the existing process regulations for catalyst production at the stage of pelletization and adjusting parameters of the manufacturing process to provide for optimal indices of catalyst quality and to avoid spoilage. The obtained data can be used for designing engineering equipment and pelletization machines.     

Curing temperature effect on mechanical strength of smokeless fuel briquettes prepared with molasses

Environmental acceptable smokeless fuel briquettes have been prepared with a low-rank coal and olive stone as biomass. The binder chosen for this study was molasses which acts with different roles, as chemical and matrix type. The effect of the curing temperature on these briquettes has been studied by Fourier transform infrared spectroscopy, temperature programmed decomposition (TPD) followed on-line by mass spectrometry and optical microscopy. TPD experiments help to predict the final properties of the briquettes more clearly than infrared spectroscopy. The aliphatic structures and methoxy groups as well as the hydrogen bonds decrease during the curing. On the other hand, the carboxylic groups tend to be formed due to the oxidation produced by the effect of curing temperature. In addition, the briquettes cured at 200 °C, 2 h showed the highest mechanical strength. These curing conditions also produce waterproof briquettes due to the presence of carboxylic groups which contribute to the stabilisation of the briquettes because of the formation of hydrogen bonds.     

Preparation and characterization of poly (vinyl butyral)‐leather fiber composites

This study reports the preparation and characterization of composites with recycled poly (vinyl butyral) (PVB) and wet blue leather fiber with leather contents of 30, 50, and 70 wt%, using an extruder equipped with a Maillefer single screw operated with a flat extrusion die. The components of the composites were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy (FTIR). After extrusion, the PVB/leather composite plates were compression‐molded to obtain specimens for testing the tensile properties, hardness, abrasion resistance, and tear strength. The morphologies of the composites were analyzed by scanning electron microscopy (SEM). The DMA and FTIR analyses showed that the recycled PVB contained plasticizer remained in the polymer matrix after extrusion. The SEM analysis revealed good interfacial adhesion between the PVB matrix and the leather fibers. Increasing the leather content in the composites led to a significant increase in the tensile modulus and a reduction in the tensile strain at breaks. The Shore hardness of the composites increased with the wt% of leather, whereas the abrasion resistance decreased. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.     

A novel technique for the development of acetabular cup by cold isostatic compaction and sintering of UHMWPE powder with optimized processing parameters

Life of a metal on ultra-high molecular weight polyethylene (UHMWPE) total hip replacement is often limited to 10–15 years, due to wear loss and aseptic loosening. Due to its high melt flow index, UHMWPE is typically processed by ram extrusion or compression molding technique, but yet to be processed to the full potential of its mechanical integrity in acetabular shape without any fusion defects or weak bonding. The main objective of the present study is to develop a novel technique to fabricate defect-free acetabular cups with desired bearing characteristics and surface finish by sintering medical-grade UHMWPE GUR 1050 powder after its cold isostatic compaction with optimum processing parameters. Sintering kinetics of UHMWPE is studied comprehensively using a thermomechanical analyzer. The influence of compaction pressure, sintering temperature, and sintering duration on sintering kinetics of UHMWPE is explored to realize their optimum. The optimally processed UHMWPE has the relative density of 97% and Vickers hardness of 5.4 with tensile yield strength and elastic modulus of 21.5 and 625 MPa, respectively. The newly developed acetabular cup exhibited inherent plateau-finished bearing surface with an average surface roughness of <100 nm, having good bearing characteristics and desired dimension.     

Material characteristics affecting formcoke

The influence of aggregate and binder phase characteristics on formcoke products has been studied by investigating the compaction kinetics of the system and determining the mechanical strength of the briquettes produced. The char phase was characterized in terms of density, hardness and porosity and the binder phase with respect to rheological properties. Results indicate that binder phase fluidity affects compaction viscosity during the particle flow stage of compaction and that char porosity influences final briquette bulk density by affecting the amount of total compaction required to obtain a given bulk density. In general, increased total compaction was shown to result in higher product bulk density with the attendent higher gross composite strength. The latter relationship was seen to be approximately linear over the range of bulk porosity found in this study. A higher briquette strength was found for systems with aggregates carbonized at lower temperatures. Similarly the binder phase fluidity was also seen to affect briquette strength, higher fluidity resulting in higher strength. It was concluded that this was due to increased binder penetration in the highly porous char carbonized at lower temperatures. With no significant pore structure in the aggregate, as found with high temperature char, briquette strength was seen to become approximately constant for the three binder coals used.     

The use of hardness in the study of compaction behaviour and die loading

An experimental relationship between density, hardness and compacting pressure is obtained for the isostatic compaction of Alcoa grade 1202 atomised aluminum powder. These results are used to evaluate the use of hardness measurement in the determination of density contours within compacts and pressure distributions at the compact—die interface. Density contours and pressure distributions are presented for closed die compacts; the results are in general agreement with those reported in the literature for more complex techniques. The technique is shown to be suitable for use in many situations.     

Consolidation behavior and hardness of P/M molybdenum

In this study, the consolidation behavior and hardness of commercially available molybdenum powder were investigated. In order to analyze the compaction response of the powder theoretically, an elastoplastic constitutive equation based on the yield function presented by Shima and Oyane was applied to predict the compact density under uniaxial pressure from 100 MPa to 700 MPa. The compacts were sintered at 1400-1600 °C for 20-60 min. The sintered density and grain size of molybdenum were increased with increasing the compacting pressure and processing temperature and time. The effect of the porosity and grain size on the hardness of the specimens was explained based on the modified plasticity theory of porous material and the Hall-Petch type equation.