Showing papers in "Journal of Chemical Engineering of Japan in 2016"

Kinetic Analysis of Decomposition of Ammonia over Nickel and Ruthenium Catalysts

Abstract: The present study investigates the decomposition of ammonia (NH3) over Ni and Ru catalysts using a kinetic model based on a reaction mechanism consisting of kinetically important elementary steps. Experimental results obtained over a wide range of reaction conditions were reproduced by the model. Recombinative N2 desorption was the rate-limiting step on the Ru catalyst; whereas, the overall rate of NH3 decomposition was controlled by the NH3 dehydrogenation step on the Ni catalyst.

Numerical Simulation of Molten Slag Deposition in Radiant Syngas Cooler with a CFD-Based Model

Abstract: A computational uid dynamic (CFD) model and a deposition model are coupled to predict the molten slag deposition behavior in radiant syngas cooler (RSC) for entrained ow coal gasi cation. The slag particle deposition model is developed by identifying the excess rebound energy as a criterion to determine if the particle is deposited or rebounded from the wall while slag solidi cation in the impact process is also considered. The simulation results show that molten slag particles stick on the membrane wall between the height of 12.2–22.0 m for Reference Case with the maximum deposition rate 1.5×10−5 kg/(m2·s) at the position of height about 16.8 m. The deposition rate increases with increasing inlet temperature and operating load. Small inlet diameter leads to high deposition rate due to high transport rate and high deposit propensity, while small inner cylinder diameter leads to higher deposition rate due to higher deposit propensity.

Laboratory and Pilot Scale Studies of Potassium Extraction from K-feldspar Decomposition with CaCl2 and CaCO3

Abstract: Processes for potassium extraction from abundant K-feldspar have recently attracted interest to ensure potash self-sufficiency for developing countries. Concurrently, distiller waste and soda residue formed in the ammonia-soda process (Solvay method) have resulted in serious pollution. A method of potassium extraction from K-feldspar with distiller waste and soda residue as additives is proposed. The effects of roasting temperature, particle size of K-feldspar and the amount of additive on potassium extraction for the K-feldspar-CaCl2-CaCO3 system were studied. The reaction kinetics of the system with mass ratios of K-feldspar (106-160 mu m) : CaCl2 : CaCO3 = 1 : 2 : 2 at 750-850 degrees C were modeled by the diffusion-based Ginstling-Brounshtein equation. The apparent activation energy was approximately 111 kJ.mol(-1). On the basis of the XRD and SEM-EDS analysis, two different reaction mechanisms were proposed below and above the melting point of CaCl2 (772 degrees C). A pilot test was carried out at a roasting temperature of 850 degrees C and the recovery of potassium was approximately 82%. The encouraging results obtained in the laboratory were replicated at the pilot scale.

Development of DEM–CFD simulation of combustion flow in incinerator with the representative particle model

Abstract: A simulation code based on the discrete element method (DEM) and computational fluid dynamics (CFD) coupling model was developed to simulate the behavior of radioactive cesium in waste incinerators. The waste lump was represented by particles in the simulation. The energy equation for a mixed gas, diffusion equation for each gas component, as well as the energy, drying, pyrolysis, and combustion equations for each particle were solved in the simulation by adding a combustion model to the standard DEM–CFD coupling model. The particle size of the waste changed as drying, pyrolysis, and combustion progressed. At the end of the combustion process, particle waste became ash, and the number of ash particles was enormous. To avoid an excessive computational load due to the high particle number, a similar assembly model was adopted to reduce the particle number in the calculation. There was a good agreement between the simulation and experimental results for the temperature at the outlet of the furnace and the flue gas composition.

Modeling and Optimization of the Hot Compressed Water Extraction of Palm Oil Using Artificial Neural Network

Abstract: Hot compressed water extraction (HCWE) is a promising green alternative to the screw press in the palm oil processing. In this study, the steady-state characteristic of the HCWE was modeled by using an artificial neural network (ANN). The overall oil yield and other outputs; β-carotene, α-tocopherol and α-tocotrienol concentration, were described by the pressure and temperature in the HCWE. The results show that the predicted yield and concentrations agree well with experimental data. These models were used to estimate the optimum conditions of the HCWE process.

Effects of Acid Treatment on the Acidic Properties and Catalytic Activity of MCM-41 for the Oxidative Dehydrogenation of Isobutane

Abstract: Mesoporous silicas have shown promise as materials for solid catalysts or catalyst supports due to their unique characteristics. Metal-doped mesoporous silicas are known to be catalytically active in the oxidative dehydrogenation (ODH) of isobutane. However, heavy-metal-free mesoporous silicas have not been studied closely for their use as catalysts. In the present study, MCM-41 (#41 Mobil composition of matter) was acid-treated to enhance its catalytic activity, although pure MCM-41 was confirmed as catalytically inactive for the ODH of isobutane (isobutene yield = 0.9%). The pH of a slurry of as-synthesized MCM-41 was changed during acid treatment. A pH adjustment to 6.5 resulted in great improvement in catalytic activity (isobutene yield = 6.1%), but a pH adjustment to 4.5 resulted in insufficient improvement (isobutene yield = 4.5%). It was confirmed via XRD and N2 adsorption-desorption measurement that the pH adjustment to 4.5 degraded the ordered structure of MCM-41. This degradation would be a crucial factor that would render acid treatment less effective. In addition to the acid treatment, Al doping to MCM-41 was conducted. Al doping also greatly enhanced the acidity and catalytic activity of MCM-41.

Hydrothermally Synthesized Ceria with a High Specific Surface Area for Catalytic Conversion of Ethanol to Ethylene

Abstract: Morphological control can be used to improve the catalytic activity of cerium oxide (ceria, CeO2). In this study, ceria with a high specific surface area was synthesized via the hydrothermal reaction of ceric nitrate and was tested for the catalytic conversion of ethanol to ethylene. As a reference, ceria was also synthesized via a precipitation reaction of cerous nitrate using aqueous ammonia. The Japan reference catalyst JRC-CEO-1 also served as a reference. The specific surface area of the hydrothermally synthesized ceria was as high as that of JRC-CEO-1, but was much higher than that of either reference after calcination at 873 K. Thermogravimetric analysis and IR spectroscopy revealed that the cerias made by hydrothermal and precipitation reactions consisted of high-purity CeO2, whereas JRC-CEO-1 contained 1.5% decomposable functional groups (OH-, CO3 2-). For both ethanol conversion and ethylene selectivity in a catalytic dehydration reaction of ethanol, the activity of the hydrothermally developed ceria was higher than that for either reference. The reaction pathway for the dehydration reaction of ethanol over ceria showed that the specific surface area and the basicity of the Lewis basic sites of the ceria were influential properties. The high catalytic activity of the hydrothermally synthesized ceria was derived from its high specific surface area and high-purity CeO2.

Recovery of Calcium Phosphates from Composted Chicken Manure

Abstract: To recover phosphorus from composted chicken manure, a batch method with aqueous HNO3, HCl and H2SO4 was used to examine the elution behavior of the aqueous calcium and phosphate contained in the manure. Since the main components in manure are Ca2+ and K+ along with PO4 3- and those ions can be dissolved using an acidic eluate, it was expected that most of the aqueous Ca2+, K+ and PO4 3- could be obtained via the elution. Therefore, it seemed plausible that the removal of the aqueous K+ obtained by the elution of composted chicken manure would result in the formation of calcium phosphates. If calcium phosphates are formed, they can be used for phosphate rock, which also consists of various calcium phosphates. When using 0.1 mol/L HNO3, HCl or H2SO4, the elution behavior of the PO4 3- was not dependent on the acids. However, 0.1 mol/L H2SO4 was not sufficient for the elution of Ca2+, probably due to the precipitation of the calcium sulfate. The eluted amount of K+ using 0.1 mol/L HNO3 was lower than that using 0.1 mol/L of either HCl or H2SO4. Since the poor elution of K+ should enrich the concentrations of Ca2+ and PO4 3- in the acidic aqueous solution after the elution, it was suggested that aqueous HNO3 would be suitable as an eluate in the present system. After the elution of the composted chicken manure, when 0.1 mol/L HNO3 was used to adjust the solution pH of the acidic aqueous solution to greater than 6, Ca2+ and PO4 3- were precipitated, but K+ was not. The precipitate was calcium hydroxyapatite, one of the typical components of phosphate rock, which showed that composted chicken manure could be replaced phosphate rock as a new source of phosphorus.

Research on Combustion and Emission Characteristics of Ammonia under Preheating Conditions

Abstract: The present study focuses on determining the potential applicability of ammonia (NH3) as a carbon-free alternative fuel through numerical simulations. The combustion and emissions characteristics of premixed NH3-air flame at preheating conditions were numerically investigated. The burning velocity and all species mole fraction were determined using the Miller and Bowman and the Reductive Konnov mechanism. The results show that both the equivalence ratio and preheating temperature have important effects on the laminar burning velocity and adiabatic flame temperature of NH3. The reaction rate of production and mole fraction of H, O, and OH radicals, together with nitrogen radicals such as NH2, NH, and N in the reaction zone, increases as the preheating temperature is increased from 298 to 573 K. Although NO concentrations in the exhaust gas increased with increasing preheating temperature under fuel-lean conditions, they could be maintained at a reasonably low level at all preheating temperatures, mainly due to the increased reduction reaction of NO with NH2, NH, N radicals. The main N radical formation in the NH3-air combustion originates from NH3 rather than N-2, which indicates that the N-2 dilution effect of NH3-air flame is negligible for NO formation. Furthermore, the equivalence ratio has a dominant effect on NO yields, because of the higher reduction reaction and lower flame temperature at higher equivalence ratio conditions, leading to a lower formation of HNO, which indicates a potential in reducing NO emissions in NH3 combustion. Therefore, the preheating temperature and equivalence ratio should be given sufficient consideration in practical operations to minimize NO formation in combustion of NH3 as a clean fuel.

Measurement and Estimation of the Particle Size Distribution by the Buoyancy Weighing-Bar Method and the Rosin-Rammler Equation

Abstract: Rondang Tambun1,2, Katsuhiko Furukawa3, Masayuki Hirayama3, Masamitsu Shimadzu4, Shin-ya Yamanaka4 and Yuichi Ohira4 1 Department of Chemical Engineering, University of Sumatera Utara, Jl. Almamater Kampus USU Medan 20155, Indonesia 2 Division of Chemical and Materials Engineering, Graduate School of Engineering, Muroran Institute of Technology, Muroran, Hokkaido 050-8585, Japan 3 Taihoku Civil Engineering and Construction Co., Furano, Hokkaido 076-0031, Japan 4 Division of Sustainable and Environmental Engineering, Graduate School of Engineering, Muroran Institute of Technology, Muroran, Hokkaido 050-8585, Japan

Water Solubility of Complexes between a Peptide Mixture and Poorly Water-Soluble Ionic and Nonionic Drugs

Abstract: Recently, a peptide mixture (Pep) obtained as a casein hydrolysate was found to be e ective for enhancing the water solubility or water dispersibility for poorly water-soluble drugs. In the present study, complexation of Pep with ionic and nonionic drugs indomethacin (Indo), ibuprofen (Ibu), and prednisolone (Pre) was studied. The water solubility of complexes containing Indo and Ibu, both of which have a dissociable carboxylic group, increased with increasing pH. In contrast, the water solubility of a complex containing Pre, which does not contain dissociable groups, was almost independent of pH. As all three complexes were permeable through an ultra ltration membrane with a molecular-weight cuto 10,000 gmol−1, the complexes were present not as colloidal materials but relatively small species in aqueous media. Moreover, Indo, Ibu, and Pre were complexed with twelve peptide fractions, which were derived from Pep by combining ammonium sulfate precipitation with ultra ltration. Water solubility of the drugs increased with all Pep-derived fractions, suggesting that various peptides interact with the drugs.