Advanced Materials Research Vol. 1094

Abstract: Inorganic species are released during pressurized gasification, can cause severe problem of hot corrosion. The direct utilization of coal is harmful for power plants. The aim of work to obtained comprehensive knowledge of release alkali species Na-,K-,Cl and S-species prior to carry out experiment. Therefore thermodynamic equilibrium calculations were performed by Fact Sage 5.2 and simulated the gasification environment at elevated pressure.Three soft Pakistani coal such as Lakhra (Vad < 41.44%), Thar (Vad < 42.02%) and Sor-range ((Vad < 21.11%) belong to Lignite and sub-bituminous coal were selected and releasing order was calculated by plotting mole fraction of each species Vs pressure (5 to 15bar ) at 1000°C.On the basis of predicted releasing order the H₂S can be predicted most stable species under gasification at elevated pressure. The high released amount of SO₂, H₂S, NaCl, KCl and HCl was predicted for LKH and SRC at 5 and 15 bar pressure and 1000°C temperature. Comparing with high pressure the predicted released of H₂S was found higher than SO₂, NaCl, KCl and HCl at 15 bar pressure while the released of SO₂ was observed lower than H₂S, NaCl, KCl and HCl at 5 bar pressure during gasification process. The above available predicted information is valuable for hot gas cleaning technology.

Abstract: Nowadays hydrogen as an important source of energy is still produced from fossil fuel processing largely, hence the separation of hydrogen from the gas mixture with high recovery ratio and purity arises as an important issue. In this paper we proposed a hydrogen recovery/production process from half-coke oven gas, and the material LaNi_4.3Al_0.7 was considered for use due to its low plateau pressure and good resistance to impurities. We use a Sieverts type volumetric apparatus to investigate the material properties,including P-C-T properties and hydriding/ dehydriding kinetics under different conditions. Based on the results obtained, the feasibility of using the material for gas separation purpose was discussed.Keywords: Gas separation; metal hydride; reaction kinetics; P-C-T properties; Sieverts method

Abstract: Hesigewula lignite was studied by fixed bed pyrolysis to achieve the optimal conditions for pyrolysis under low temperature. It was found that the maximum tar yield 6.60wt% under 50 mL/min of gas carrier, 500 °C, 0.5 MPa and holding for 15 min. By column chromatography, we extracted aromatics of the tar generated under the optimal condition. Aromatics with 2 and 3 rings are predominant in the tar from Hesigewula lignite pyrolysis by gas chromatography-mass spectrometry analysis (GC-MS), however, the tetracyclics and above compounds were very few. Naphthalene and its derivatives had pivotal position in aromatics.

Abstract: Apatite-type lanthanum silicates doped with Pr³⁺ at the La site, La_10-xPr_xSi₆O₂₇ (x = 0, 1, 2, 3, 4, 4.5), were synthesized via sol-gel process. Thermal behavior of the dried gel of La_10-xPr_xSi₆O₂₇ sample was studied using TG/DTA. X-ray diffraction, SEM and complex impedance analysis were used to investigate the microstructure and electrical properties of La_10-xPr_xSi₆O₂₇ ceramics. The XRD results indicated the maximum doping quantity of Pr³⁺ is x = 4.5. Lanthanum silicates doped with Pr³⁺ cations have a higher total conductivity than that of undoped lanthanum silicates. The enhanced total conductivity depends on the improved density of La_10-xPr_xSi₆O₂₇ (x = 0, 1, 2, 3, 4, 4.5). At 973K, the highest total conductivity is 1.36×10^-3S.cm^-1 for La₉PrSi₆O₂₇ ceramic.

Abstract: The growth process of diamond single crystals under HPHT was tested with acoustic emission (AE) technology, and the AE signals were analyzed with fast Fourier transform and wavelet packet analysis. The results show that there are many new frequency peaks in the frequency range that is higher than 80 kHz, and comparative analysis shows that these new frequency peaks are caused from the growth process of diamond crystals. The value of the signal energy and peak in different frequency bands are compared along with the diamond growth process. And it has reflected the dynamic changes in the time domain of the acoustic emission signals stimulated by the different acoustic emission sources. It also shows that the frequency of acoustic emission signals could be used as the effective means to distinguish the different acoustic emission sources in the diamond growth process.

Abstract: Preferential adsorption takes place at the step ledge between adjacent crystal faces, which usually serve as active sites for breaking chemical bonds. In this paper, we present a structural model to interpret the habit modification of single crystals in terms of the step geometries relationship between crystal faces. A new series of high index faces parallel to the ledge between adjacent facets can be explicitly determined from the presence of the symmetry operators in the space group. The relative stability of these new faces undergoes a faceting transition, driven by the adsorbate-induced changes of the step configuration. Combined with the chemical bond-geometric approach, our predictions accurately reproduce the tapering evolutions of KDP crystals in the present of metallic ions. The current work provides a new insight on how changes affecting elementary steps on one face are translated into the emergence of a new crystallographic face.

Abstract: To solve the problems of high dimension, multicollinearity, easily over-fitting, this paper further studies characteristic wavelength selection method, and proposes the improved successive projections algorithm based on mean impact value algorithm (SPA-MIV). The results show that the proposed algorithm reduces data dimensions and improves data quality effectively. After being processed by improved successive projections algorithm, the determination coefficient of of testing set of moisture, ash and volatile PLS calibration models are increased to 0.9318, 0.9127, 0.9389, and the of testing set determination coefficient of moisture, ash and volatile BP neural network calibration models are 0.9645,0.9432,0.9536.

Abstract: The depth profiles of Ni-coated copper substrates polished by different mesh size sandpapers were measured by the glow discharge optical emission spectroscopy (GDOES) depth profiling technique. The measured depth profiles were well fitted by the MRI-CRAS model developed recently on the basis of the Mixing-Roughness-Information depth (MRI) model and the CRAter-Simulation (CRAS) model, taking into account the pronounced crater effect upon GDOES depth profiling. The crater effect upon depth profiling was characterized quantitatively and the interface roughness values between the coated Ni layer and the Cu substrates were determined and compared with the ones measured by AFM.

Abstract: The activity of deformation modes and orientation evolution in the {0001}- oriented hexagonal crystals with basal slip as easy slip mode during channel die compression were investigated by crystal plasticity finite element method (CPFEM). Material parameters of magnesium and its alloys were used in CPFEM simulation. The pyramidal <c+a> slip contributes most of the strain in all cases of relative CRSS value and friction coefficient between mold and material. The friction coefficient has a more significant influence on the activity of various deformation modes and the orientation deviation from ideal {0001} orientation (<0001>//ND) compared with the relative CRSS value. The deviation angle can reach about 20° after 70% applied reduction under the friction coefficient of 0.20.

Abstract: It is easy to form the crystallization fouling of sodium (potassium) fluorosilicate during the wet-process phosphoric acid (WPA) production, which seriously affects the continuity of production. The crystallization fouling deposition model is selected to establish a model to simulate sodium (potassium) fluorosilicate fouling deposition process and to predict the deposition rate of fouling in the pipe in this paper. The predicted results by the model are on the whole consistent with the existed experimental data. The factors, such as fluid velocity, temperature and ion concentration that affect fouling deposition rate were discussed, it was found that the fouling deposition rate increases with the increasing of fluid velocity, decreases with the increasing of temperature, and the greater the ion concentration, the greater the deposition rate.