共查询到18条相似文献,搜索用时 62 毫秒
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最低喷动速度是喷动床设计的重要参数之一。过去人们习惯采用Mathur-Gisher公式来计算,但由于该公式是建立在小直径床层(D_c=0.076~0.3m)实验的基础上的,故在大直径床层上应用时,产生明显的偏差。本文通过实际数据分析,提出了大直径喷动床层最低喷动速度计算的经验公式。 相似文献
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气固流化床广泛应用于化工、炼油、冶金、电力等工业生产领域。由于流化床中气固两相流动的复杂性,流化床测量方法的研究成为了一个重要的研究领域。电容层析成像(ECT)是20世纪80年代以来发展起来的一种非介入式多相流测量技术,已经在多相流测量领域发挥了重要作用。总结了国内外近年来应用ECT技术进行气固流化床测量的进展,特别是对气固流化床内固体相浓度、流化床流型识别、固体相速度等方面工作进行了总结,并简单介绍了ECT在流化床干燥中的应用,讨论了ECT和其他测量方法结合使用情况。最后对ECT在流化床测量中的局限性和发展方向进行了讨论。 相似文献
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针对低温流体液、气两相的介电特性,通过向传统的电容-介电分布函数关系的线性近似方程中引入修正偏量,得到了修正的电容层析成像线性反演算法。以8电极电容层析成像传感器作为几何模型,对液氧-氧气管内两相流进行了模拟,对比了4种不同流型下原始线性算法、修正的线性算法及以全变分1范数正则化为代表的非线性算法的反演结果。采用相关性系数及图像误差定量衡量了反演结果的质量,结果表明,修正线性反演算法显著提升了反演结果的质量,全变分1范数正则化的求解耗时是修正线性算法的10倍以上。当赋以3%测量噪声时,非线性算法表现出对噪声极强的敏感性,修正线性算法具备更好的抗噪能力和反演结果准确性。 相似文献
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A cylindrical gas-liquid-solid spouted bed, driven exclusively by gas flow, has been developed with a high potential for use in biochemical processes, such as a biological wastewater treatment. A plexiglass column with a 152 mm inner diameter was used in combination with a 53 mm inner diameter plexiglass draft tube. Three particle types were studied with densities ranging from 1044 kg/m3-1485 kg/m3 and average particle sizes ranging from 0.7-2.5 mm. Four flow regimes were observed when increasing the gas velocity, including fixed bed, semispouted bed, full spouted bed, and internal circulating fluidized bed. The transition gas velocities between those regimes were experimentally measured and termed as minimum spouting velocity, full spouting velocity, and minimum circulating velocity, respectively. A measurement of the downward particle flux in the annulus was used to identify the minimum spouting velocity, while the particle velocity and dense phase retraction in the annulus were monitored for the full spouting and minimum circulating velocities. All regime transition velocities increased with more dense particles and longer draft tubes. The minimum spouting velocity and full spouting velocity were not affected when varying the nozzle-tube gap, while the minimum circulating velocity increased with longer nozzle-tube gaps. Experiments without a draft tube were carried, though the spouting stability was significantly reduced without the draft tube. 相似文献
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Abdelwahid Azzi Hiba Bouyahiaoui Abdallah S. Berrouk Andrew Hunt Ian S. Lowndes 《加拿大化工杂志》2020,98(8):1835-1848
The temporal and cross-sectional distributions of particles in a 127 mm diameter fluidized bed have been obtained using a new generation, high-speed electrical capacitance tomography. Two planes of eight electrodes were used and mounted at 160 and 660 mm from the gas distributor which was a 3 mm thick porous plastic plate (maximum pore size of 50-70 μ m). 3 mm diameter, nearly-spherical polyethylene granules made up the bed. Experiments at sampling frequencies of 200-2000 cross-sections per second and gas superficial velocities from just below the minimum fluidization to 83% above minimum fluidization velocities were used. The time series of the cross-sectional average void fractions have been examined both directly and in amplitude and frequency space. The last two used probability density functions and power spectral densities. The information gathered shows that the fluidized bed was operating in the slugging mode, which is not surprising given the size of the particles. It has been found that an increase in the excess gas velocity above the minimum fluidization velocity resulted in an increase in the mean void fraction, an increase in the length and velocity of the slug bubbles as well as the bed height, and a slight decrease in the slug frequency. The results are presented in a level of detail suitable for comparison with later numerical simulation. 相似文献
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It is difficult to measure the gas-solids flow in a circulating fluidised bed (CFB) because of the complicated and rapid transient process. Electrical capacitance tomography (ECT), a cross-sectional imaging technique, has been used to measure the dilute flow in a large square CFB. A sensor has been specifically designed for the measurement and a new algorithm has been developed for image reconstruction. Flow conditioning parts (internals) are designed and placed inside the CFB, aiming to enhance the contact between gas and particles in the dilute gas-solids flow. The dynamic characteristics and detailed information were obtained on two sections in the bed at different height. The performance of the internals is related to their size, combination, height in the bed and the superficial gas velocity. It has been confirmed that a particular combination of internals can increase the solids concentration in the central area of a cross-section, and can improve the probability density distribution (PDD) with a moderate gas velocity. Using a combination of a large internal at an upper location and a small one at a lower location can optimise the flow in the CFB. 相似文献
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以欧拉多项流模型为基础,对底角锥度为60°、床直径为0.44 m的喷动床内气固两相流的动力学特性进行了模拟研究,并对不同气速下喷泉高度、颗粒体积分数、颗粒速率的变化进行分析,结果发现喷泉高度与进口气速在u/ums=1.2~1.8范围内具有良好的线性关系,拟合度可达到0.9997。固体颗粒体积分数在轴心区域较高,随着径向距离的增加逐渐下降,且随高度的增加呈现先减小后增大的趋势;颗粒体积分数受速率的影响较大,随着喷动速率的增大,颗粒体积分数趋于减小,但减小幅度不同。颗粒速度在喷泉核心区随床层高度增大而减小。同一床层高度上的颗粒速度随气速的增加而增大,但增大值不同。 相似文献
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The two-dimensional spouted bed has been pointed out in recent research works as an improved configuration of spouted beds. The main advantages in relation to the conventional spouted beds are the easy construction and scale-up. In this work we begin the study of coating of tablets in two-dimensional spouted beds. An experimental system was constructed and the data obtained were used to determine the values of maximum pressure drop, minimum spout flowrate and gas-to-particle heat transfer coefficient, for 36 process conditions. The experimental results have been correlated with process and geometrical parameters. 相似文献