Abstract: This study presents a systematic investigation of pressure drop and gas holdup in an upward-flow fixed-bed reactor, examining the effects of bubble size, bed height, particle shape, superficial gas velocity (SGV), and superficial liquid velocity (SLV) based on experimental measurements and empirical correlations. Two bubble generators, namely ring tube generator (RTG) and porous sintered film generator (PSG), are used. Key findings reveal that for the PSG, increasing SGV decreases small-bubble population while promoting large-bubble formation, with the bubbles stabilizing at a Sauter mean diameter (d₃₂) of ~3 mm. The RTG produces stable large bubbles (d₃₂ = 6-7 mm) with minimal size variations across the range of tested SGVs. The pressure drop decreases with an increase in SGV but increases with higher SLV and bed height, primarily due to the reduced liquid holdup and the dominance of static pressure. Smaller bubbles reduce the pressure drop by slowing rise velocity and minimizing frictional resistance. Clover-shaped particles exhibit the highest pressure drop owing to large porosity, while 3-mm toothed spheres show higher pressure drop than 5-mm spheres at high SGV because of intensified capillary forces. The gas holdup increases with increasing SGV and bed height but decreases slightly with increasing SLV. Smaller bubbles enhance gas holdup by improving bed distribution and residence time. The 3-mm toothed spheres show the highest gas holdup due to stronger capillary trapping, whereas the clover-shaped particles exhibit the lowest. Empirical correlations for pressure drop and gas holdup are developed, yielding calculation errors within ±1% and ±20% of the experimental values, respectively.

Key words: Fixed-bed reactor, Pressure drop, Gas holdup, Bubble characteristics

摘要： This study presents a systematic investigation of pressure drop and gas holdup in an upward-flow fixed-bed reactor, examining the effects of bubble size, bed height, particle shape, superficial gas velocity (SGV), and superficial liquid velocity (SLV) based on experimental measurements and empirical correlations. Two bubble generators, namely ring tube generator (RTG) and porous sintered film generator (PSG), are used. Key findings reveal that for the PSG, increasing SGV decreases small-bubble population while promoting large-bubble formation, with the bubbles stabilizing at a Sauter mean diameter (d₃₂) of ~3 mm. The RTG produces stable large bubbles (d₃₂ = 6-7 mm) with minimal size variations across the range of tested SGVs. The pressure drop decreases with an increase in SGV but increases with higher SLV and bed height, primarily due to the reduced liquid holdup and the dominance of static pressure. Smaller bubbles reduce the pressure drop by slowing rise velocity and minimizing frictional resistance. Clover-shaped particles exhibit the highest pressure drop owing to large porosity, while 3-mm toothed spheres show higher pressure drop than 5-mm spheres at high SGV because of intensified capillary forces. The gas holdup increases with increasing SGV and bed height but decreases slightly with increasing SLV. Smaller bubbles enhance gas holdup by improving bed distribution and residence time. The 3-mm toothed spheres show the highest gas holdup due to stronger capillary trapping, whereas the clover-shaped particles exhibit the lowest. Empirical correlations for pressure drop and gas holdup are developed, yielding calculation errors within ±1% and ±20% of the experimental values, respectively.

关键词: Fixed-bed reactor, Pressure drop, Gas holdup, Bubble characteristics