Influences of bedding characteristics on the acoustic wave propagation characteristics of shales

The acoustic response characteristics of shales were investigated by the acoustic transmission experiment,which is the basis of solving geological and engineering problems using the seismic or logging information during the process of the exploration and development of shale gas reservoirs.Based on the theory of acoustic wave and the background of acoustic transmission experiment,the initial condition,vibration source condition,boundary condition and stability condition were constructed,and the numerical simulation of acoustic transmission experiment of shales were completed through Matlab programming.The results show that under the same bedding angle,the acoustic time and attenuation coefficient of shales shown positive correlation with the bedding density;whereas under the same bedding density,the variation laws of the acoustic time and the attenuation coefficient of shales were more complex with the change of the bedding angle,that is,the acoustic time and attenuation coefficient of shales increased first,then decreased and then increased again with the increase of the bedding angle.

Fluidization characteristics of different sizes of quartz particles in the fluidized bed

Fluidization characteristics of quartz particles with different sizes are experimentally investigated in a fluidized bed with an inner diameter of 300 mm and height of 8250 mm.Results show that the average solid holdup increases with the increase in superficial gas velocity and the decrease in initial solid holdup in the dense zone of the fluidized bed.The average cross-sectional solid holdup decreases with increasing bed height and superficial gas velocity.The bed expansion coefficient increases with the increase in superficial gas velocity and the decrease in solid holdup.Correlations of average solid holdup,average cross-sectional solid holdup and bed expansion coefficient are also established and discussed.These correlations can provide guidelines for better understanding of the fluidization characteristics.

Modelling the bed characteristics in fluidised-beds for top-spray coating processes

A particle sub-model describing the bed characteristics of a bubbling fluidised bed is presented. Atomisation air, applied at high pressures via a nozzle positioned above the bed for spray formation, is incorporated in the model since its presence has a profound influence on the bed characteristics, though the spray itself is not yet considered. A particle sub-model is developed using well-known empirical relations for particle drag force, bubble growth and velocity and particle distribution above the fluidised-bed surface. Simple but effective assumptions and abstractions were made concerning bubble distribution, particle ejection at the bed surface and the behaviour of atomisation air flow upon impacting the surface of a bubbling fluidised bed, The model was shown to be capable of predicting the fluidised bed characteristics in terms of bed heights, voidage distributions and solids volume fractions with good accuracy in less than 5 min of calculation time on a regular desktop PC. It is therefore suitable for incorporation into general process control models aimed at dynamic control for process efficiency and product quality in top-spray fluidised bed coating processes.