Conversion of recycled sawdust into high HHV and low NOx emission bio-char pellets using lignin and calcium hydroxide blended binders

Spruce wood sawdust (S), as biomass waste, could be utilized as a renewable fuel, but it suffers from its bulky, low energy density, high volatiles content and NO_x emission. This study investigated the possibility of conversion S into bio-char pellets (SC-Ps) as renewable and CO₂-neutral bio-fuel. Sawdust derived bio-char (SC) was produced through pyrolysis, and subsequently compressed into SC-Ps bonded by lignin (L) and hardened by Ca(OH)₂, NaOH, CaCl₂, CaO. The combustion characteristics of S and SC, the physical properties of SC-Ps including abrasive resistances (ARs), impact resistance index (IRI) and compress strengthens (CS) were evaluated. Results showed that the high heat value (HHV) of SC increased by 95% and its NO_x emission decreased due to the release of N-containing volatiles. Among these hardeners, addition of 5% Ca(OH)₂–10% L reduced the disruptive force created by uptake moisture and played an effect of hydration on hardening the bonds. In addition, the catalysis of hydroxide promoted the polymer chain growing into three-dimensional cross-linking that strengthened the bonds. Thus, the mechanical strengths of the SC-Ps bonded by Ca(OH)₂/L were sufficient for directly transportation and being charged into the blast furnace.     

Hydro–pyro integration in the processing of nickel laterites

Hydrometallurgical process routes are seen to be the future of treatment of the lower grade nickel laterites ores. Hydrometallurgical projects of recent years have focused on HPAL and have been largely unsuccessful economically so far, with huge capital cost overruns.The simplest and least capital intensive of the possible alternatives to HPAL is atmospheric heap leaching. Development work is also underway by several companies into atmospheric tank leaching which is also a potentially viable alternative.The natural product for a leaching process is a high grade nickel intermediate either from a direct precipitation process (containing approx. 36% Ni) or via ion exchange (>50% Ni).There are many existing pyrometallurgical facilities which could easily be adapted to take this nickel intermediate giving them significant potential benefits especially as nickel laterite ore grades diminish. The nickel production from these plants could also be increased and for new plants large capital and operating cost savings achieved by using suitable intermediates.There are also potential environmental benefits with much less energy consumed and lower greenhouse gases emitted per tonne of nickel produced.In the future an integrated hydrometallurgical plant with attached existing smelter or a more advanced pyrometallurgical smelting process (e.g. a DC arc furnace) could well be the way forward for new projects.     

The master sintering curves for BaTi0.975Sn0.025O3/BaTi0.85Sn0.15O3 functionally graded materials

The most important aim in the design and processing of functionally graded materials (FGMs) is to produce devices free from any deformation. Smart choices of different combination of graded layers, as well as the heating rate during sintering, are important for the fabrication of high-quality FGMs. In this study, BaTi_0.975Sn_0.025O₃/BaTi_0.85Sn_0.15O₃ (noted as BTS2.5 and BTS15, respectively) FGM was used as a model system for the construction of master sintering curves (MSCs) and estimation of the effective activation energies of sintering for different BTS graded layers. The MSCs were constructed, for BTS2.5 and BTS15 graded layers in FGMs, using shrinkage data obtained by a heating microscope during sintering at four constant heating rates, 2, 5, 10 and 20 °/min. The effective activation energies were determined using the concept of MSC; values of 359.5 and 340.5 kJ/mol were obtained for graded layers BTS2.5 and BTS15, respectively. A small difference of the effective activation energies of chosen powders made it possible for us to prepare high-quality FGMs, without delamination, distortion or other forms of defects.     

Lithiation of ramsdellite–pyrolusite MnO2; NMR,XRD, TEM and electrochemical investigation of the discharge mechanism

Electrolytic manganese dioxide (EMD) is made in aqueous sulfuric acid and neutralized or ion exchanged with aqueous lithium hydroxide before use in Li batteries. Solid state Li NMR studies show that Li is present on surface and vacancy sites and migrates into Mn (III) related sites after heat treatment to remove water. During heat treatment the MnO₂ rearranges from ramsdellite/pyrolusite intergrowth EMD to a defect pyrolusite heat-treated manganese dioxide (HEMD). EMD exhaustively treated with lithium hydroxide solution has 40–50% of the protons in EMD exchanged for Li ions to produce a structurally unchanged γ-MnO₂. Li magic angle spinning (MAS) NMR reveals that this lithiated material contains lithium in cation vacancy and Mn (III) related sites in the MnO₂ lattice in addition to ionic Li on the surface. During heat treatment, the vacancy lithium content prevents the ramsdellite to pyrolusite rearrangement in HEMD formation. Instead, an ordered ramsdellite/pyrolusite intergrowth of lithiated manganese dioxide (LiMD) is formed with an approximate composition of 50% ramsdellite and 50% pyrolusite. Li MAS NMR of LiMD shows Li resonances near 280 and 560 ppm, consistent with Li transition from surface and cation vacancy sites into the ramsdellite lattice.LiMD discharged against lithium shows two processes, one near 3.1 V, the other about 2.8 V. Li MAS NMR studies show the initial reduction results a lithium resonance near 560 ppm associated with Li near a mixed valence Mn (III/IV) environment followed by appearance of a resonance near 100 ppm consistent with a Li environment near Mn (III). TEM studies of the reduced material show initial expansion of the ramsdellite lattice accompanied by a loss in crystallinity in the 3.1 V discharge process followed by disappearance of the pyrolusite content via conversion to ramsdellite in the second discharge process.     

Role of vermiculite and zirconium–vermiculite on the formation of zircon–cordierite nanocomposites

The Zr^4 +–vermiculites were studied in their new role of the zircon precursor in the clay minerals mixtures which were prepared for firing of the zircon–cordierite nanocomposites. Currently there is a lack of data available about the structure of Zr^4 +–vermiculites, on which this study was performed. The modeling of the arrangement of interlayer material in the Zr^4 +–vermiculite led to new findings that water molecules are attracted more strongly by Mg^2 + cations than by Zr-tetrameric cations, and that both the tetrameric cations [Zr₄(OH)₁₄(H₂O)₁₀]^2 + and [Zr₄(OH)₈(H₂O)₁₆]^8 + may be present in the interlayer space of the Zr^4 +–vermiculites. Vermiculites from two different localities Czech Republic (Verm1) and from Brazil (Verm2) were intercalated using the zirconyl chloride (ZrOCl₂–30% solution in HCl) and the prepared Zr^4 +–vermiculites were designated as Zr^4 +–Verm1 and Zr^4 +–Verm2, respectively. Influence of the Zr^4 +–Verm1 and Zr^4 +–Verm2 in the mixtures of clay minerals on the properties of zircon–cordierite nanocomposites were investigated by their comparison with the properties of the zircon–cordierite nanocomposites, which were prepared using saturation of the clay minerals mixtures containing Verm1 and Verm2 with the zirconyl chloride (ZrOCl₂–30% solution in HCl). The zircon–cordierite nanocomposites fired from the clay mineral mixtures containing Zr^4 +–Verm1 and Zr^4 +–Verm2 showed a maximum porosity of P = 58 and 60%, skeletal density SD = 3.2 and 3.6, and the smallest pores with a median pores diameter MDP = 18 and 15 μm, respectively, in comparison with the zircon–cordierite nanocomposites fired from the clay mineral mixtures containing Verm1 and Verm2 and saturated with zirconyl chloride solution. The type of vermiculite Verm1 or Verm2 in the clay mineral mixtures did not affect the contents of the crystalline mineral phases in cordierite and zircon–cordierite nanocomposites.     

Microwave sintering of copper–graphite composites

Microwave processing is a distinctive and alternative technique when compared with the available processes such as material synthesis, sintering, and processing utilizing the conventional heating sources. Owing to microwave–material molecular interaction, microwave heating is of internal and faster. This results in improved quality of the product with time and energy savings. Metal at its bulk form reflects microwaves; however in its powder form, it couples with microwaves. This work emphasizes on the development of copper–graphite metal matrix composite for electrical sliding contact applications through microwave hybrid heating (2.45 GHz, 3.2 kW). The fabricated composites were tested for their mechanical properties such as porosity, relative density and hardness. Microstructural aspects were studied through SEM.     

Analysis of evaporating mist flow for enhanced convective heat transfer

Enhancement of forced convective heat transport through the use of evaporating mist flow is investigated analytically and by numerical simulation. A two-phase mist, consisting of finely dispersed water droplets in an airstream, is introduced at the inlet of a longitudinally-finned heat sink. The latent heat absorbed by the evaporating droplets significantly reduces the sensible heating of the air inside the heat sink which translates into higher heat-dissipation capacities. The flow and heat transfer characteristics of mist flows are studied through a detailed numerical analysis of the mass, momentum and energy transport equations for the mist droplets and the airstream, which are treated as two separate phases. The coupling between the two phases is modeled through interaction terms in the transport equations. The effects of inlet mist droplet size and concentration on the thermal performance of the heat sink are analyzed parametrically. The results provide insight into the complex transport processes associated with mist flows. The simulations indicate that significantly higher heat transfer coefficients are obtained with mist flows as compared to air flows, highlighting the potential for the use of mist flows for enhanced thermal management applications.     

A novel fabrication route to microlaminated TiB2–NiAl composite sheet with {111}<μνω> texture by roll bonding and annealing treatment

Microlaminated TiB₂–NiAl composite sheet consisting of alternating NiAl and TiB₂-rich layers has been successfully fabricated. This fabrication method is composed of roll bonding for producing a multi-laminated Ni–(TiB₂/Al) sheet from Ni sheets and TiB₂/Al composite sheets, and of subsequent annealing treatment for forming a NiAl intermetallic phase by reaction diffusion. Microlaminated TiB₂–NiAl composite sheet obtained by this method exhibits strong {111}<μνω> texture. The formation mechanism of such texture by reaction diffusion has been discussed in view of texture inheritance. This method could utilize reaction diffusion to control texture component of materials, which is expected to provide an access to synthesize materials with texture for special requirement.     

The effect of sodium sulphate on the hydrogen reduction process of nickel laterite ore

A series of nickel laterite ores with different calculated amounts of anhydrous sodium sulphate were prepared by physical blending or sodium sulphate solution impregnation. The reduction of the prepared nickel laterite ore by H₂ was carried out in a fluidised-bed reactor with provisions for temperature and agitation control, and the magnetic separation of the reduced ore was performed using a Davis tube magnetic separator. The mineralogical properties of the raw laterite ore, reduced ore and magnetic concentrate were characterised using ICP, TG–DSC, N₂ adsorption, X-ray diffraction and optical microscopy. The catalytic activity of sodium sulphate was also studied by using Hydrogen temperature-programed reduction. The experimental results indicate that Na₂SO₄ could overcome the kinetic problems faced by the laterite ore and that it exhibited noticeable catalytic activity only if the temperature reached at least 750 °C. This high temperature accelerated the crystal phase transition of the silicate minerals and increased the utilisation of H₂. In comparing the results from the two different methods for adding Na₂SO₄, the nickel content and recovery of the magnetic concentrate were increased by using the impregnation method rather than the physical blending method and the increasing amount of sodium sulphate assisted in the further beneficiation of nickel. The partial pressure of H₂ and the reducing time also affected the reduction process of the iron oxides. The results of the microscopic study indicated that the formation of a Fe–S solid solution, which was derived from the SO₂ sulphide reduction of FeO, was conducive to mass transfer and accelerated the coalescence of metallic ferronickel particles. For the nickel laterite ore, under the synergistic effect of sodium sulphate and hydrogen, a nickel content and nickel recovery of 6.38% and 91.07% were obtained, respectively, with high product selectivity.