Corrosion on continuous supercritical water oxidation for polychlorinated biphenyls

Abstract

The corrosion resistance of Hastelloy C-276 and titanium alloy G5 against C1 anion which was generated by supercritical water oxidation (scWO) of 3-chlorobiphenyl (3-PCB) in a flow reactor was investigated over a period of 336 hours at a constant pressure of 30 MPa. The condition of the scWO reaction zone was fixed at 750 K. The concentration of chlorine in the effluent collected after cooling to ambient temperature was about 850 wppm. The Hastelloy C-276 has a nominal ratio of approximately 3.7 Ni/l Cr. The Ni/Cr ratio in the effluent was the same with the nominal ratio, and the Hastelloy C-276 was proved to be corroded on the surface located between the bottom of the reactor and the cooling parts, which are under sub- and near- critical conditions of water. The corrosion rate was found to be 5 to 34mm/y in the zone where the temperature ranged from 543 K to 650 K and the corrosion spread over the whole surface of the alloy; however, one can hardly observe such a serious corrosion except the zone located in the between the reactor and the cooling part.     

Twelve new compounds from Ligularia melanothyrsa; isolation of melanothyrsins A–E,normelanothyrsin A,and other eremophilane sesquiterpenoids

Twelve new compounds, namely, five melanothyrsins A–E (1α-angeloyloxyeremophilenolides), normelanothyrsin A (1α-angeloyloxynoreremophilenone), and six other eremophilane-type compounds, have been isolated from Ligularia melanothyrsa Hand.-Mazz. (Asteraceae), collected in the Sichuan Province of China. Six of the compounds have a 1α-angeloyloxy moiety, while the other six have no functional group at the C-1 position. The absolute configuration was also determined using CD spectra. This is the first chemical study of compounds isolated from this species.     

Titanylation and vanadylation of highly π-conjugated porphyrins

We report the efficient synthesis of tetrabicycloporphyrin titanyl and vanadyl without decomposition of the bicyclo[2.2.2]octadiene unit. The complexes were heated under vacuum to give titanyl and vanadyl tetrabenzoporphyrins in 100% yield. We also titanylated and vanadylated tetra[2,3]naphthoporphyrin and tetra[2,3]anthraporphyrin, which have a greater degree of π conjugation than tetrabenzoporphyrin.     

Efficient production of reference materials of hazardous organics using smart calibration by nuclear magnetic resonance

The accurate quantification of pesticide residues in food is an important factor in assuring the quality of life of our citizens. In general, chromatographic methods are used, which require certified reference materials (CRMs) for each analyte of interest for accurate quantitative analysis. Recently, regulation of pesticides in food, limiting the positive maximum residue (positive list system) has been brought into effect in Japan. Furthermore, ISO/IEC 17025 requires calibration and testing laboratories to program calibrations and measurements traceable to the International System of Units (SI). Accordingly, these laboratories need a suite of CRMs that are traceable to the SI. In order to address these requirements for every analyte of interest in an efficient manner, a new approach to producing SI traceable CRMs is required. Nuclear magnetic resonance (NMR) has been used widely in chemical analysis. One of the well known characteristics of NMR is the proportional relationship between peak area and the number of nuclei contributing to the peak. If accurate relative intensities of peak areas are obtained, this provides an attractive quantitative tool for organic compounds. The area of a signal from an analyte can be measured with respect to another signal originating from a comparator that has been added to the sample solution. The chosen comparator should not react with the analyte or resonate at any chemical shift similar to that of the analyte. This enables us to produce SI traceable CRMs more effectively. In this paper, we demonstrate a new approach for producing CRMs for pesticides using quantitative NMR??an SI traceable quantitative technique.     

Heat flux measurement over a cone in a shock tube flow

This paper is the part 2 of our previous thin film heat transfer measurements. In the first report we measured time variations of heat flux over a cylinder placed in a shock tube flow and compared experimental results with CFD results, Saito et al. (Shock Waves 14:327–333, 2004). We report a result of heat transfer measurements over an 86° apex angle cone surface impinged by a Ms = 2.38 shock wave in air with distributed thin film transfer gauges along cone surface and its comparison with results of numerical simulations. We performed double exposure holographic interferometric observation, and also from the heat transfer measurement and numerical simulation, confirmed the presence of delayed transition from regular to Mach reflection over the cone. The numerical estimation of delayed transition distance from the apex agreed very well with experimental one.      

Layered model of electrorheological fluid under flow

We present a theoretical model of the behavior of a concentrated electrorheological fluid (ERF) which explicitly takes into account the effects of conductivity. The increase in shear viscosity under an electric field is due to a layered structure between the electrodes, made up of the remnants of particle chains adhering to the electrodes by electrostatic image forces, and a freely flowing liquid layer where all the shear flow is concentrated. This layered model can explain the variation of electric current with shear rate, as well as the rheological response of a dynamic yield stress proportional to the square of the applied electric field.     

Experimental and numerical study of pressure wave refrigerator performance

A new compact pressure wave refrigerator has been designed and manufactured at the Shock Wave Research Center, Institute of Fluid Science, Tohoku University. The performance of this device was investigated for combinations of major operational parameters, such as the rotational speed of gas distributor, the length of expansion tubes, the input gas pressure. The maximum temperature decrease of 20 K has been measured. Some theoretical consideration to the efficiency of the pressure wave refrigerator and two-dimensional numerical simulations were carried out in order to understand the wave interactions that take place inside the device.Received: 26 May 2003, Accepted: 12 August 2003, Published online: 14 October 2003 Correspondence to: T. Saito     

Prediction of growth rate and density of frost layer developing under forced convection

An experimental study was carried out on heat and mass transfer rates, growth rates and the density of frost layers on a flat plate in forced convection conditions. The density and thickness of the frost layers were correlated by the dimensionless parameters introduced in the authors' previous paper [6]. Measured density and thickness of the frost layers are compared with those in natural convection conditions and with those measured by other investigators. It is shown that these parameters can also be used to generalize the density and growth rates of frost layers developed under forced convection conditions.     

Interaction of a shock with a sphere suspended in a vertical shock tube

Shock wave interaction with a sphere is one of the benchmark tests in shock dynamics. However, unlike wind tunnel experiments, unsteady drag force on a sphere installed in a shock tube have not been measured quantitatively. This paper presents an experimental and numerical study of the unsteady drag force acting on a 80 mm diameter sphere which was vertically suspended in a 300 mm x 300 mm vertical shock tube and loaded with a planar shock wave of M _s = 1.22 in air. The drag force history on the sphere was measured by an accelerometer installed in it. Accelerometer output signals were subjected to deconvolution data processing, producing a drag history comparable to that obtained by solving numerically the Navier-Stokes equations. A good agreement was obtained between the measured and computed drag force histories. In order to interpret the interaction of shock wave over the sphere, high speed video recordings and double exposure holographic interferometric observations were also conducted. It was found that the maximum drag force appeared not at the time instant when the shock arrived at the equator of the sphere, but at some earlier time before the transition of the reflected shock wave from regular to Mach reflection took place. A negative value of the drag force was observed, even though for a very short duration of time, when the Mach stem of the transmitted shock wave relfected and focused at the rear stagnation point of the sphere.Received: 31 March 2003, Accepted: 7 July 2003, Published online: 2 September 2003     

Analysis of water molecules around GTP in Hras-GTP complex and GDP in Hras-GDP complex by molecular dynamics simulations

We investigate the structures of the Hras-GTP and the Hras-GDP complexes in water solvents in order to understand the mechanism of GTP hydrolysis in the Hras-GTP complex. We performed MD simulations of these complexes in order to study the positions and the orientations of water molecules around the guanosine nucleotides. Using trajectories we calculated the angular distribution of water molecules around the most distant phosphorus from guanosine in our previous work. It was shown that water molecules are distributed evenly in GTP, although unevenly in GDP. This suggests that the trigger of GTP hydrolysis is possibly the attack of water molecule to γ?phosphate from the appropriate direction. In this paper, in order to investigate the role of water molecules in GTP hydrolysis in detail, we calculate the orientation of water molecules. The distribution of the orientation is different between GTP and GDP. In order to investigate the cause of this difference, we examine the hydrogen bonds between water molecules and oxygen atom of the most distant phosphate from guanosine. We find that these hydrogen bonds are formed. We also find that the oxygen atom of hydrogen bond is determined by the position of the water molecule of hydrogen bond.