A simulating investigation into the characteristics of the mass transfer between molten steel and particles in the 150 t RH-IJ refining

The characteristics of the mass transfer between powder particles and liquid steel in the Ruhrstahl Heraeus process injection （RH-IJ） refining were simulatively investigated by the use of a 1/4 scale water model of a 150 t Ruhrstahl Heraeus（RH） degasser. The influences of the lifting gas flow rate, the up-snorkel and down-snorkel inner diameters and the size of powder particles on the characteristics of the mass transfer were examined. The results show that under the condition that the inner diameters of both the up-snorkel and the down-snorkel are the same, the mass transfer coefficient in the liquid,k increases with the increase of the inner diameter of the up-snorkel,the particle size and the lifting gas flow rate （Q1）. However, the increase of Q~ should not result in a saturated circulation rate. Under the current working condition,k ranges from 3. 392 × 10 -5 m/s to 2. 661 × 10-4 m/s. On the other hand,with a given lifting gas flow rate and up-snorkel inner diameters ,the mass transfer weakens with the increase of the down-snorkel inner diameter. An inherently nonlinear relationship between the circulation rate （Q~） of molten steel in the RH degasser and k,which increases with the increase of Q1,was found. Under the condition of other parameters being the same,k increases with the increase of the powder particle size. In order to enhance the mass transfer,it is better not to use extremely fine powder.

Electromagnetohydrodynamic flows and mass transport in curved rectangular microchannels

Curved microchannels are often encountered in lab-on-chip systems because the effective axial channel lengths of such channels are often larger than those of straight microchannels for a given per unit chip length.In this paper,the effective diffusivity of a neutral solute in an oscillating electromagnetohydrodynamic(EMHD)flow through a curved rectangular microchannel is investigated theoretically.The flow is assumed as a creeping flow due to the extremely low Reynolds number in such microflow systems.Through the theoretical analysis,we find that the effective diffusivity primarily depends on five dimensionless parameters,i.e.,the curvature ratio of the curved channel,the Schmidt number,the tidal displacement,the angular Reynolds number,and the dimensionless electric field strength parameter.Based on the obtained results,we can precisely control the mass transfer characteristics of the EMHD flow in a curved rectangular microchannel by appropriately altering the corresponding parameter values.

Mechanical properties and failure characteristics of fractured sandstone with grouting and anchorage

Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage,the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5–320.0%, 62.8–493.0%, and 31.6–181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile–shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.

Correlation between Tectonic Environment and Chracteristics of Mass Movement （Landslides）： A Case Study from Java, Indonesia

In Central Java and Yogyakarta Special Region, there are several zones, which potential of landslide disaster. The zones are in general located at uplitted and or folded mountains, such as North Serayu Mountains, South Serayu Mountains, Menoreh Mountains, Southern Mountains and slopes of young volcanic area, including Ungaran-Merbabu-Merapi area, and Slamet-Sundoro-Sumbing area. Besides morphology, another main factor influencing vulnerability of the terrain is physical properties of the composing lithology. The geologic formations in the study area are predominantly composed of clayey and volcanic rocks. The cohesion force of clayey rock ranges 0.4-0.7 kg/cm^2, the internal friction angle ranges 20°-35°, while the cohesion force of volcanic rock （weathered） ranges 0.25-0.27 kg/cm^2, and the friction angle ranges 20°-35°. In general, rocks occupying the area are collectively dissected by joints and active faults, with soil of more than 5 m thick. Local rainfall belongs to high category （〉 2,500 mm/y）. However, landslides that occur in each physiographic zone mentioned above show different characterizations.

Effect of Configuration on Mass Transfer in a Filter-press Type Electrochemical Cell

Effect of configuration （structure of electrode, interelectrode gap, positions of inlet and outlet, volume of the cell and additional nets） on mass transfer characteristic of a filter-press type electrochemical cell has been studied. The mass transfer coefficients on the electrodes were obtained by using the well-known technique based on the determination of limiting diffusion current. It is found that mass transfer coefficients with mesh electrode are greater than that of with plate electrode. Mass transfer coefficient is decreased with interelectrode gap. While interelectrode gap achieved a certain value （7 ram）, mass transfer coefficient is steady, no more declining. Mass transfer characteristic for different positions of inlet and outlet are different and dimensionless number groups correlated equations are obtained by experiment. Mass transfer characteristic is the best when inlet located on the top and outlet on the bottom of the cell respectively. While magnified the volume of the cell to eight times, mass transfer characteristic changes little. Mass transfer characteristic without nets is lower than that of with additional nets in the exit region, but higher than that of with additional nets in the entry region.

Spatial and temporal variation of water mass mixing characteristic in the East China Sea

On the basis of the observation data of Kuroshio since 1984 and relative historical data in the East China Sea, spatial and temporal variation of water mass mixing characteristic in the observation area is analysed. The main results are as follows.

Physical Modeling of the Vacuum Circulation Refining Process of Molten Steel

The available studies in the literature on physical modeling of the vacuum circulation (RH, i.e. Ruhrstahl Heraeus) refining process of molten steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was employed to investigate the flow and mixing characteristics of molten steel under the RH and RH KTB (Kawasaki top blowing) conditions and the mass transfer features between molten steel and powder particles in the RH PTB (powder top blowing) refining. The geometric similarity ratio between the model and its prototype (a multifunction RH degasser of 90 t capacity) was 1:5. The effects of the related technological and structural factors were considered. These latest studies have revealed the flow and mixing characteristics of molten steel and the mass transfer features between molten steel and powder particles in these processes, and have provided a better understanding of the refining processes of molten steel.

Effect of Structural Parameters on the Performance of NS High-efficiency Composite TraysⅠ.The Effect of Aperture and Opening Ratio on NS High-efficiency Composite Trays

In this paper,the structure and characteristics of the NS high-efficiency composite trays based on the doublelayer aperture jet sieve plate and compositely structured packing were investigated.The effect of aperture and opening ratio of plate on the fluid dynamics of the NS high-efficiency composite trays,such as the dry tray pressure drop,the wet tray pressure drop,the entrainment,the froth height,the leakage and mass transfer characteristics,were investigated.As a result, the low pressure drop,the high efficiency and the high capacity are the main advantages of the NS high-efficiency composite trays compared to other types of trays.According to this study,small aperture is useful for reducing the pressure drop and entrainment with a high mass transfer efficiency;while large aperture can achieve high capacity and efficiency in a broader operating range at the same pressure drop and entrainment.

Numerical analysis of seepage flow characteristic of collapse column under the influence of mining

Based on the importance of fractured rock mass seepage research, in order to analyze seepage flow characteristics of collapse column under the influence of mining, a method by embedding fractured rock mass flow solid coupling relationship into FLAC3D internal flow models is presented according to fluid-solid coupling theory and strength criterion. A calculation model of numerical analysis was established, and the influences of mining pressure and plastic damage to pore water pressure and seepage vector change rule were studied. The results show that collapse column is the main channel of confined water seepage upward. The impact is not big when the workface is away from the collapse column. But when the workface is nearing a collapse column, there will be a seepage channel on a side near the workface, in which seepage vector and head are comparatively large. With workface pushing through collapse column, the seepage channel transfers to the other side of the column. In addition, when the plastic damage area within the collapse column breaks through, a "pipeline flow" will be formed within the column, and seepage field will change remarkably and the possibility of water bursting will be greater.

Mercury mass flow in iron and steel production process and its implications for mercury emission control

The iron and steel production process is one of the predominant anthropogenic sources of atmospheric mercury emissions worldwide. In this study, field tests were conducted to study mercury emission characteristics and mass flows at two iron and steel plants in China. It was found that low-sulfur flue gas from sintering machines could contribute up to41% of the total atmospheric mercury emissions, and desulfurization devices could remarkably help reduce the emissions. Coal gas burning accounted for 17%–49% of the total mercury emissions, and therefore the mercury control of coal gas burning, specifically for the power plant burning coal gas to generate electricity, was significantly important. The emissions from limestone and dolomite production and electric furnaces can contribute29.3% and 4.2% of the total mercury emissions from iron and steel production. More attention should be paid to mercury emissions from these two processes. Blast furnace dust accounted for 27%–36% of the total mercury output for the whole iron and steel production process. The recycling of blast furnace dust could greatly increase the atmospheric mercury emissions and should not be conducted. The mercury emission factors for the coke oven,sintering machine and blast furnace were 0.039–0.047 g Hg/ton steel, and for the electric furnace it was 0.021 g Hg/ton steel. The predominant emission species was oxidized mercury, accounting for 59%–73% of total mercury emissions to air.

Targeted isolation and identification of bioactive pyrrolidine alkaloids from Codonopsis pilosula using characteristic fragmentation-assisted mass spectral networking

Codonopsis pilosula(CP),a well-known food medicine homology plant,is commonly used in many countries.In our preliminary study,a series of pyrrolidine alkaloids with high MS responses were detected as characteristic absorbed constituents in rat plasma after oral administration of CP extract.However,their structures were unclear due to the presence of various isomers and the lack of reference standards.In the present study,an MS-guided targeted isolation of pyrrolidine alkaloids of CP extract was performed by ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry(UPLC/Q-TOF MS).For data analysis under fast data directed acquisition mode(Fast-DDA),an effective approach named characteristic fragmentation-assisted mass spectral networking was successfully applied to discover new pyrrolidine alkaloids with high MS response in CP extract.As a result,seven new pyrrolizidine alkaloids[codonopyrrolidiums C–I(3–9)],together with two known ones(1 and 2),were isolated and identified by NMR spectral analysis.Among them,codonopyrrolidium B(1),codonopyrrolidium D(4)and codonopyrrolidium E(5)were evaluated for lipid-lowering activity,and they could improve high fructose-induced lipid accumulation in HepG2 cells.In addition,the characteristic MS/MS fragmentation patterns of these pyrrolizidine alkaloids were investigated,and 17 pyrrolidine alkaloids were identified.This approach could accelerate novel natural products discovery and characterize a class of natural products with MS/MS fragmentation patterns from similar chemical scaffolds.The research also provides a chemical basis for revealing in vivo effective substances in CP.