Expansion characteristics of an anaerobic fluidized bed reactor with internal biogas production

More realistic dynamic bed‐expansion experiments using a three‐phase anaerobic fluidized bed reactor (AFBR) with and without internal biogas production were conducted for the establishment of correlation equations for the mean volume ratio of wakes to bubbles ( k ). A predictive model was also developed for the expansion characteristics of the three‐phase AFBR with internal biogas production. The predicted bed‐expansion heights ( H GLS ) deviated by only ±10% from the experimental measurements for the three‐phase AFBR. According to the modeling results, if a three‐phase AFBR is loaded into a carrier with low specific gravity (dry density of carrier, ρ md = 1.37 g cm −3 ; wet density of carrier, ρ mw = 1.57 g cm −3 ) and operated at a high superficial liquid velocity ( u l = 4.0 cm s −1 ), the ratio of H GLS to H LS at a high superficial gas velocity ( u g = 1.5 cm s −1 ) can reach as high as 271%. A higher fluidized‐bed height has a greater effect on the bed‐expansion behavior because of the decrease in liquid pressure (surrounding gas bubbles) along the fluidized‐bed height. From parametric sensitivity analyses, H GLS is most sensitive to the parameter reactor width ( X ), especially within a small Δ X / X 0 range of ±10%; sensitive to ρ mw , diameter of the carrier, ρ md and total mass of carrier and least sensitive to u l , biofilm thickness and u g . Copyright © 2005 Society of Chemical Industry