Investigation Of The Flow Characteristics Of Gas-Solid Spouted Beds

Spouted beds technology has been applied to many industrial processes related to agriculture, petroleum, energy sources, foodstuff, medication, metallurgy and so on. The flow characteristics of spouted -beds affect product qualities, economic benefits, etc. There have been many literatures on the investigations into the flow characteristics of spouted beds, which have provided the foundation for the industrial applications. In practice, spouted beds technology is also used in many processes dealing with wet materials such as drying, granules spray-painting and improving, fine granules preparing, etc. However, there is still lack of researches on the flow characteristics of spouted beds treating with wet materials.Two kinds of solid materials were used to study flow characteristics in a two-dimension spouted bed, one being dry materials, the other being wet materials. The investigations on the later was carried out based on those on the former to provide the foundation for the application of spouted beds technology to the processes involving wet materials.The minimum spouting velocity, the maximum spouting pressure and the flow regime transition were determined to investigate the law of the flow characteristics transformation in spouted beds. To study the flow regime transition, the signals of pressure fluctuations were analyzed by modern nonlinear mathematic methods including Amplitude Spectrum Analysis, Hurst Analysis, V-statistic Analysis and Standard Deviation Analysis respectively, extracting the characteristic parameters of the signals such as main frequency, Hurst exponent, maximum V-statistic and standard deviation, which can reflect the flow state in spouted beds.The followings are the main achievements:1) Experimental formulas are obtained to calculate the minimum spouting velocity and the maximum spouting pressure in a dry gas-solid spouted bed. The experiments and the formulas all show that ums and Δpmax are both affected by the factors such as granule diameter, granule density, static bed height, nozzle diameter and cone angle.2) Increasing the spouting velocity, three types of flow regimes emerge in the drygas-solid spouted bed in turn, that is, fixed bed state, stable spouting state, and unstable spouting state. Modern nonlinear mathematic analytic methods are used successfully for dividing accurately flow regimes in spouted beds into which the researches are still not enough up to the present. Among these methods, Hurst Analysis and V-statistic Analysis are adopted to the field of spouted beds technology for the first time. According to the results, Hurst Analysis and Standard Analysis can distinguish precisely the transitions among these flow regimes.3) The moisture contained in the materials affects the wet spouted bed greatly making the gas-solid flow complex. The minimum spouting velocity, the maximum spouting pressure and the flow regime transition are all affected by moisture distinctly. Increasing the spouting velocity, the changes of the flow regimes in the wet bed fall into three states, i.e. fixed bed state, unstable spouting state and relatively stable spouting state. The transitions between these flow regimes could be identified by the results from Hurst's analysis and V-statistic analysis of the signals of pressure fluctuations. In addition, when the moisture content exceeds a certain value, dead zones and agglomerations appear. The measures to avoid and to lighten the degree of agglomerating are supposed.In a word, all these researches would help provide theoretical foundation for the operation of spouted beds.