盐水体系内气体驱动液固逆流化床的颗粒流动特性

The gas-driven inverse liquid-solid fluidized bed is a novel type of inverse fluidized bed bioreactor known for its low energy consumption，minimum solid attrition，and high mass transfer efficiency. These attributes make it a highly promising technology for biological wastewater treatment. To explore its potential in treating high-salinity wastewater，it is necessary to determine the effects of brine concentration on particle flow characteristics. A pilot-scale gas-driven inverse liquid-solid fluidized bed was custom-designed and constructed to investigate the detailed particle flow characteristics in a brine system. Key parameters，including flow regimes，flow regime transition velocities，bed expansion height，and solids holdup were obtained through a combination of experimental observations and monitoring the variations of the bed net pressure drop. The results show that with an increase in superficial gas velocity，the bed experiences four flow regimes：fixed bed，transition fluidization，complete fluidization，and circulating fluidization. These regimes are distinguished by flow regime transition velocities，such as the initial fluidization gas velocity，the minimum complete fluidization gas velocity，and the minimum circulating fluidization gas velocity. Comparatively，larger-diameter particles，such as PE4.0，are harder to fluidize than smaller particles like PE2.0 particles. Both the initial fluidization gas velocity and the minimum complete fluidization gas velocity increase for PE2.0 and PE4.0 particles as the brine concentration and the particle loading rise. Similarly，the minimum circulating fluidization gas velocities for PE2.0 and PE4.0 particles increase at higher brine concentrations. However，a unique trend was observed based on particle loading. For PE2.0 particles，the minimum circulating fluidization gas velocity consistently increases ， while for PE4.0 particles ， it first decreases and then slightly increases. Furthermore，an increase in brine concentration intensifies the density difference between the liquid and solid phases，making fluidization increasingly difficult. This leads to a decreased bed expansion height and an increase in the average solids holdup. The results provide basic data and theoretical insights for the development and industrial application of gas-driven inverse liquid-solid reactors.