Hvdrodvnamic Characteristics In Dense Transport Bed

Pulverized Coal Pressurized Dense Transport Bed Gasifier is applicable for coal of low rank, high ash and high melting point and it is characterized by flexible gasification agents and low cost, which is one of the emerging gasification technologies suitable for IGCC.Experiments were carried out in a cold dense transport bed (0.102m-IDx17m-height) with three kinds of silica sand belonging to Geldart group B. The hydrodynamic characteristics in the dense transport bed were revealed and the dense suspension upflow (DSU) was realized, which was of high solids circulations rates (Gs) and high solids concentration. The main results were as follows:1. Effects of the components of dense transport bed1) The multiplex aeration along the standpipe could significantly increase Gs. The highest Gs was up to987kg/m2·s and nearly13m zone of the riser was in the DSU flow.2) The exit configurations with large inclination angle (≥30°) could facilitate the increase of Gs.2. The axial and radical flow characteristics1) The solids acceleration length was longer in a higher riser. Considering the effect of the riser height, a correlation was proposed to predict the solids acceleration length. Relative deviations of most of the predictions were less than20%over a wide range of Gs (18~987kg/m2·s).2) The solids concentration in the fully developed region was lower in a higher riser. Considering the effect of the riser height, a correlation was proposed to predict the solids acceleration length. Relative deviations of most of the predictions were less than25%in a wide range of Gs (8~987kg/m2·s).3) A correlation was proposed to predict the radial profile of the solids concentration, which was suitable for both Geldart group A and group B particles. Predictions of the correlation were in good agreement with the experimental data.3. The boundary of the DSU flow regime 1) Using the gas mass flow rate instead of the superficial gas velocity to reflect the effect of operating conditions, a boundary was proposed, which could distinguish the DSU and fast fluidization flow regime well.The system balance model1) A distribution pattern of the solids concentration was proposed, which was in the exponential distribution in the acceleration zone and kept constant in the fully developed zone. On this basis, combined with the prediction correlations of solids acceleration length and solids concentration in the fully developed region, a model was proposed for predicting the pressure drop in the riser. Relative deviations of most of the predictions were less than25%in a wide range of Gs (130~987kg/m2·s).2) A pressure balance model was proposed with the pressure drop model of the riser. Gs and axial and radical distribution of solids concentration were well predicted.