Pressure Fluctuations in a Liquid-Sprayed Gas Fluidized Bed

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• 作者：Sandip Bhowmick ; Neetu A. Baveja ; C. P. Shringi ; K. T. Shenoy ; S. K. Ghosh
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：August 13, 2014
• 年：2014
• 卷：53
• 期：32
• 页码：12631-12638
• 全文大小：460K
• ISSN：1520-5045

文摘

Generally the quality of a liquid-sprayed fluidized bed is monitored by measuring the bed temperature at several axial positions, as well as the average bed pressure drop. The number of temperature measurement points increases during scale-up of the reactor. Such a large number of measuring points makes the installation very expensive. High frequency pressure fluctuation measurement in a fluidized bed is emerging as a promising technique to retrieve qualitative information on the dynamics of gas fluidized beds. Pressure fluctuation measurement at just one height is sufficient for early detection of changes in the hydrodynamics of fluidized beds when the fluidized bed height is about 1 m or less. Hence, investigation has been carried out on pressure fluctuation in a liquid-sprayed gas fluidized bed. A monitoring technique based on the pressure fluctuation measurement can be used in parallel with the conventional temperature measurement, and the number of temperature measuring points can be reduced. Also the combination of both gives more reliability in online monitoring. In the present study, differential pressure fluctuation was measured across a liquid-sprayed fluidized bed. The feed liquid was either water or ammonium nitrate solution in the experiments carried out. The measured data were analyzed using time domain, frequency domain, and state space analysis. The aim of this investigation was to find a reliable analysis technique which can be easily applied to relate the measured pressure data to the health of the liquid-sprayed fluidized bed. A drastic reduction in the standard deviation of pressure fluctuation was observed when ammonium nitrate solution was injected. The standard deviation shows the demarcation among dry, water-sprayed, and solution-sprayed fluidized beds. However, a wide spread of its value with time adds difficulty in setting the limit corresponding to desired behavior of the solution-sprayed fluidized bed. In the frequency analysis a significant difference was not observed among dry, water injected, and solution injected fluidized beds with respect to the dominant frequency and the magnitude of the peak. S-statistics shows some promising results as most of the S values were below the critical value for consistent hydrodynamics or quality of the liquid-sprayed fluidized bed. If the pressure fluctuation in a dry fluidized bed is chosen as reference, S values are significantly higher than the critical value. It was also found that the S-statistics can detect the change in bed hydrodynamics when a higher concentration solution was fed to the fluidized bed.