Tawiwan Kangsadan

A 21st. Century Perspective on Molybdenum Powder Production by Hydrogen Reduction

High purity molybdenum metal powder is produced commercially from hexavalent molybdenum precursors, viz.: ammonium dimolybdate (ADM) or molybdenum trioxide. One conventional process incorporates first-stage and second-stage flowsheet components, with hydrogen gas serving as reductant. This two-stage strategy is employed in order to minimize the formation of volatile molybdenum species that would otherwise be generated at the high temperature required to obtain molybdenum (Mo) in a single stage conversion of the molybdenum precursor. Although molybdenum powder has been produced commercially for over a century, a comprehensive understanding of the kinetic mechanisms and powder characteristics, e.g. oxygen content and particle morphology, is far from being definitive. In fact, it might be argued that the “art” and engineering, in a commercial context, has advanced ahead of the fine-detail science-derived metallurgical process-engineering. Theoretical contributions presented in this paper are focused primarily on the fundamentals of the conversion process associated with second-stage reduction process – MoO2 to Mo and the factors that contribute to the oxygen content of the molybdenum powder product (1000 to 100 ppm(w) O, range). Thus, equilibrium-configuration details concerning both solid and gas phases are addressed, including the volatile hexavalent molybdenum vapor complexes as well as solubility of oxygen in molybdenum. In regard to the role of a chemical vapor-transport mechanism on powder morphology in second-stage conversion of MoO2 to Mo, it is shown that the partial pressure of the prominent molybdenum hydroxide vapor-complex (MoO2(OH)2) is far too low to support such a mechanism. This contention has been corroborated by employing helium to control the partial pressures of hydrogen and water in the gas phase. Secondarily, a limited assessment of the intrinsic rate-controlling mechanisms that can contribute to the residual oxygen-content of the Mo powder product is also provided. Powder morphology, and its concomitant influence on specific surface-area of the Mo powder product, is found to correlate with the oxygen-content determination of the powder produced during second-stage reduction, and according to the processing strategy employed. Consequently, it has been found cogent to “partition” second-stage reduction into: i) a relatively high-rate Primary Reduction Sequence, and ii) a lower rate Deoxidation Sequence.

Ultrasonic pretreatment enhanced the enzymatic hydrolysis of rice straw

Rice straw can be utilized to use as a raw material for production of biofuel due to its content with a high amount of sugar in a form of 35–40% w/w cellulose and 25–30% w/w hemicelluloses. The effect of ultrasonic treatment to enhance the saccharification process of the enzymatic hydrolysis from rice straw was investigated. Two frequencies at 20 and 24 kHz of ultrasonic treatment were used for 80 min on rice straw before the enzymatic hydrolysis was applied by using commercially available enzyme cocktails: Accellerase™ 1000, Cellic CTec and NS 50013 at 50°C for 48 h. The result was found that the glucose concentration of pretreated rice straw was significantly higher than that of untreated rice straw (p < 0.0001). At frequency of 24 kHz, the glucose concentration of all enzymes was significantly greater than that of enzymes at frequency of 20 kHz (p<0.0001). When treating the rice straw with the Accellerase™ 1000 was yield significantly the highest glucose concentration among the other enzymes (p<0.0001). These results reviewed that the ultrasonic pretreatment could enhance the saccharification process resulting in the acceleration of enzymatic hydrolysis.

Ethanol production from rice straw using ultrasonic pretreatment

Pretreatment is one of the approaches to yield the higher saccharification process leading to optimization of ethanol yield. The effect of ultrasonic pretreatment on ethanol production from rice straw was studied. A 0.16 kW/L ultrasonic treatment was applied to treat rice straw during enzymatic hydrolysis and fermentation process. The enzymatic hydrolysis process was carried out at 50°C and pH 4.8 by using a commercial enzyme and followed by fermentation with S.cereviceae. Morphological structure of rice straw was analyzed by a scanning electron microscopy (SEM) and the glucose concentration was detected by biochemistry analyzer. The result showed that the structure of rice straw after ultrasonic treatment showed a breaking of lignin and exposition of cellulose surface. The glucose concentration of the pretreated rice straw increased significantly by 57.65% (p = 0.003) when compared to the untreated rice straw. The total ethanol concentration of the untreated was not obviously different from the pretreated rice straw. Results revealed that ultrasonic treatment could enhance the ethanol production from rice straw.

Chemical Thermodynamics of Hydrocarbon Compositions in Natural Gas Field, Northeast of Thailand

The phase envelope of hydrocarbon species in natural gas can be predicted by using thermodynamic simulation. Conceptual thermodynamics depends on physical and chemical characteristics in equilibrium condition. The API gravity of condensate is expressed in a range of 55–63°. Its average density is similar to the specific gravity of 0.74. Pressures in each gas processing process are decreased from the gas well (74.754 bar g) to the condensate tank (0.02 bar g). Mostly methane is discovered approximately 96 mol%. Due to physical and chemical properties, this petroleum reservoir indicates the dry gas reservoir. Chemical reactions depending on hydrocarbon compositions can be valuable for evaluating phase equilibrium. These chemical reactions based on hydrocarbon species are fabricated by chemical species as reactants and products. For creating them, all compositions related to the genesis of petroleum in the same environment are combined as a reactant. They are possibly defined as phase related to Gibbs free energy. Carbon dioxide, hydrogen, and nitrogen gas in petroleum reservoir are 10, 8, and 2 mol%, respectively. The chemical thermodynamics is simulated by using Prode Properties, a computer software program, in which Peng–Robinson equation of state is used as the chemical thermodynamic model. Characteristics of phase envelope consist of the critical temperature and pressure at phase transformation between liquid and gas. Two types of conceptual schemes are varying the invariable and variable mole fraction to evaluate the phase envelope. For their invariable mole fraction, the carbon ratio is defined at 60:20 percentages. Temperatures of natural gas from the phase envelope are inversely proportional to equilibrium constant. High temperature at low equilibrium constant specifies the forward chemical reaction. For their variable mole fraction, the increased carbon atoms affect to gradually intensify the temperature and pressure. Hydrocarbon types and mole fraction of these components concern to the possibility of phase envelope at suitable phase.

Mathematical Model of Petroleum Dynamics in Closed Conduit

Petroleum transport from a gas well to the gas production plant is relevant to the petroleum production of the natural gas field. This migration affects movement direction on distance and chemical components under the emphasis upon the relationship between condensate and other fluid hydrocarbons. The physical properties of condensate are analyzed on the basis of API gravity (55.52–62.84°), density (0.73–0.76 g/cm3), specific gravity (0.7362–0.7566), Reid vapor pressure, and true vapor pressure. The highest hydrocarbon composition is methane, 96.70 %. Hydrocarbon concentrations from the gas processing plant are found overall C7+ (heptane, C7H16) to C16 (hexadecane, C16H34), and found most octane (C8H18). Petroleum dynamics is evaluated in the criteria of petroleum transport in closed conduit. Mathematical model of petroleum dynamics is defined by the diffusion coefficient of the specific chemical reactions depending on methane–ethane and methane–propane which are 15.71 and 9.20 cm2/s, respectively. The quantities of molar fluxes gradually increase from one location to another location when phases change from gas to liquid, and decrease to the condensate storage tank due to the completion of liquid. The liquid phase preferably occurs because propane is slightly heavier than ethane. Their physical properties have been less affected to molar flux in the chemical reaction of propane. According to methane–ethane combination, molar fluxes as a function of sampling distances of methane in reactants are higher than methane in products. Besides, the molar fluxes of other components are expressed in the systematic trend.

Interactive Force of Two-Dimensional Compressive Deformation by Discrete Element Method (DEM)

Discrete Element Method (DEM) computer simulation is used to examine the influence of contact force between two-dimensional aggregates of polystyrene microsphere formed on the air-liquid interface. Colloidal aggregates have been treated as the granular material or discontinuum materials. The interaction force models are related to experiment which had done by digital video microscopy. The interaction mechanisms of the contact forces between particles in the colloidal system can be considered as a combination of spring and dashpot force and van der Waals force. According to the DEM, the interaction forces are evaluated to introduce relations between particles and the result comparison between the computer simulation and the experimental work. This study indicates that the behavior of the colloidal aggregates depends on the long-ranged (spring and dashpot) and the short-ranged interaction force (van der Waals). Besides, the behaviors shown in both computer simulation and the experiment are in good agreement. Thus, this computer simulation method can mimic the behavior of colloidal aggregates forming as a monolayer at the air-liquid interface.

Compressive Strength of Fired-Clay Brick with Variations in Composition of Rice Husk Ash Compared with Ancient Bricks in Dvāravatī Peroid, Northeast Thailand

Clay raw materials are approved by using stream sediments from a river in the Northeast of Thailand. These sediments at grain sieved for particle size below 75 µm are mixed with black-rice husk ash (RHA) at various ratios of 1:1, 1:2, and 1:3. The clay/RHA mixtures are cast and fired at 900, 1,000, 1,100, and 1,200 °C. A uniaxial compressive test is carried out for all types of specimens acquired from different firing temperatures. The increase of firing temperature increases the overall strength with the exception of the firing temperature of 1,100 °C when RHA is present in the mixture. Results show that inclusive specimens with increased amount of RHA decrease their ultimate compressive strength and elastic modulus. The reduction of the strength with increased RHA is remarkable for specimens fired at 1,100 °C. The compressive strength, elastic modulus of fired-clay blocks shows a linear relationship when compared between two firing temperatures of 900 and 1,200 °C but dramatically fluctuations at firing temperatures between 1,000 and 1,100 °C. The primary conclusion is that the strength of the fired-clay blocks is governed by the quartz-tridymite-cristobalite phase transformation. It is found that cristobalite transforms from tridymite at temperatures as low as 1,100 °C. The strengths and mineral components of the mixed-fired-clay blocks (1:2) at 1,000–1,200 °C can be related to ancient bricks in Fa Daed Song Yang (FDSY), during Dvāravatī period. However, the FDSY bricks show obviously plastic deformation with yield strength of 1.0–1.4 MPa and elastic modulus of 100–230 MPa.

Compressive Strength in Various Submersion Tests of Fired Clay Bricks from Chi River Sub-Basin

The river sediments from the Chi River basin, including Chi River and Nam Phong River, are valuable to comprehend the brick process, physical and chemical properties which lead to its strength. Study areas cover three different regions in Maha Sarakham, Kalasin and Roi Et provinces nearby six brickyards which are separated in two areas Nam Phong and Chi River area. Mechanical property is referred to compressive strengths of a brick unit. These compressive strengths of the fired brick unit increase with increasing their densities. Elastic moduli of original fired brick at the ultimate stress and strain corresponding by time in submersion test show that any solutions filled in void or pore can enhance the apparent density of bricks. Thus, fired bricks are capable to resist compressive force than the normal condition. The ratio of modulus in submersion test for 4 hours, expressed in the original fired brick to water, acidic saline and saline is 1: 1.1: 1.2: 1.6, respectively. The stress level depends on the fracture plane over particular long space fabricating by manufacturing process. These results are related only to the linearity plot.

Dynamic Correlation Function of Monodispersed Colloid

Diffusive behaviors for two-dimensional (2D) monodispersed polystyrene array of droplet spreading by either methanol or ethanol suspension are observed on a rigid surface. Methanol solution can spread speedily on the glass surface because of the positive spreading coefficient. Conversely, the ethanol will not easily proliferate out. Monodisperse polystyrene particles are involved in Brownian motion in a thick layer during alcohol evaporation. A monolayer dimension of the drop has been developed at the final spreading. Lateral capillary forces are produced and caused the aggregation of particles. Evaporation at the edge of the ethanol film did not lead to the film to retract. The formation of 2D array, which preceded the spreading of the microscopic droplet across the surface, is able to indicate the dense structure to the dynamic correlation function.

Geochemical Speciation Associated to Brine and Groundwater

Chemical speciation of brine and groundwater is examined to assess the distribution of chemical stability and behaviors of their solutions. Brine and groundwater are randomly collected from Ban Muang and Wanon Niwat District, Sakon Nakhon province. Hydrochemical parameters and also chemical compositions of their major ions are examined to evaluate the hydrochemical facies. Brine is generally indicated the Na-Cl type. For major cations, groundwater expresses mainly the sodium and calcium ions. However, brine presents dominantly sodium and potassium ions. Major anions of groundwater display principally the bicarbonate and chloride, but brine shows primarily the chloride and sulphate. The salinity zone of sodium chloride is confined only in the small area. The influence of rock salts in some areas is concerned. Relationship of Na+ and Cl-proves the stoichiometric balance of them. Chemical phases from the saturation indices consist of anhydrite, calcite, dolomite and gypsum, which found most in every sample. Generally, saturation condition of groundwater indicates the under saturation. Besides, saturation indices (SI) of brine state the super saturation for anhydrite. The anhydrite saturation index is obviously presented the supersaturated condition when the total dissolved solids (TDS) are greater than 250,000 mg/L.