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This work aims at improving the thermal shock resistance of Si3N4-SiC refractories. Si3N4-SiC specimens were prepared through two means:vacuum vibration casting and machine pressing, using industrial SiC particles and Si powder as raw materials and nitridation-firing at 1 400 °C for 8 h. The properties and density distribution of the specimens were characterized, and a water quenching method combined with a residual fracture toughness test program was designed to evaluate the thermal shock resistance of the Si3N4-SiC refractories. The comparison results indicate that the vacuum vibration cast specimens have better general properties and higher fracture toughness retention ratio, more uniform density distribution and less crack sources than the traditional pressed specimens, hence the vacuum vibration cast specimens have better thermal shock resistance than the traditional pressed ones. [ABSTRACT FROM AUTHOR]

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The resistance coefficient of dredging pipelines slurry is the basic index of hydraulic dredger's production prediction when transportation is limited. For the calculation of resistance coefficient, there are many formulas at home and abroad, but they all belong to the semi empirical and semi theoretical formula. The experimental conditions are ideal, and the applicability of the formulas is limited, which can't effectively guide the actual production and construction to some extent. We introduced the method to calculate the resistance coefficient of slurry using dredger construction history data, and developed the calculation software of slurry resistance coefficient. Taking the long distance dredging and filling construction of cutter suction dredger in Tianjin Port as an example, we carried out the cased analysis, which can provide the basis for production prediction project under similar working conditions. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to find out the variation characteristics and flow laws of two-phase fluid in coalbed methane (CBM) wells, the fluid parameters detector was developed, which had the functions to not only monitor the fluid pressure, temperature, fluid level, velocity, density distribution and bubbles forms of two-phase fluid, but also provide actual data to forecast the variations characteristics or show flow laws of two-phase fluid in coalbed methane wells. Based on the working principles and structures of the detector parts, the detection methods of the key two-phase fluid parameters including density distribution, bubbles forms and flow were established. Therefore, the detector can be applied in CBM and shale gas drainage, as well as in intelligent gas drainage. [ABSTRACT FROM AUTHOR]

With the selection of Geldart B type magnetite powder as medium solids, we investigated the density distribution characteristic of the fluidized bed along the directions of bed heights and axial positions, by combining the experimental measurement and numerical simulation based on the Euler-Euler multi-phase model. The results indicate that the distribution range of bed densities along bed heights and axial positions are 1.95-2. 10 g/cm³ and 2.00-2. 10 g/cm³ respectively with the operating gas velocity of 1.50Umf ≤ U ≤ 2.20Umf, and the standard deviation both less than 0.20 g/cm³. The density stability of axial positions is better than the density stability along different bed heights. Therefore, we should pay close emphasis to maintain the density fluctuation along bed heights as least as possible, which aims to improve the density stability in the whole ADMFB. It shows good agreements of the experimental measurement and numerical simulation results. [ABSTRACT FROM AUTHOR]