The Measurement Of Hydrodynamic Parameters And The Mixed Characteristics In Multi-Stage Bubble Columns

Bubble columns are widely used as gas-liquid reactors in many fields due to their simple construction, no mechanical transmission components, operation stability, low operating cost, high energy efficiency and good mass and heat transfer rates, such as hydrogenation, desulfurization, Fischer-Tropsch synthesis, fermentations, bio-reactions, coal liquefaction and waste water and gas treatment etc.. A distinguishing feature of the bubble column slurry reactor is the intense back-mixing of the liquid phase, which results in reducing the low yields of the reaction and selectivity of products in most industrial applications. Based on the principle of CSTRs in series, introduction of partition plates in the bubble column decreases the back-mixing of liquid. The study on hydrodynamic parameters in multistage bubble column reactors can provide a theoretical direction for the further design and optimization of the multistage bubble columns which is very important for the intense energy and environmental problems.In this paper, a bubble column was used in the cold model experimental study. The measurement of hydrodynamics parameters and the mixed characters were studied with 2.5 m high and an inner diameter of 0.30m bubble column with plates using various measurement methods.The experiments results show that the local gas holdup and the liquid velocity decrease with the increasing of the radial position r/R, which are similar to the one in common bubble columns. Gas holdup, gas cap height, liquid velocity, axial dispersion coefficient and liquid circulation velocity increase with the superficial gas velocity increasing. The sieve plates introduced in bubble column can retard the gas and liquid moving from lower area to upper area. A gas layer appears under the sieve plate which departs the bubble column into two parts and forms two CSTRs to decrease the back-mixing, which result in the gas holdup under the plate is higher than the one above. The low opening area of the plate has a stronger block affect a higher gas cap height and a lower liquid circulation velocity. Distribution of the holes in plates has a slightly affect to the hydrodynamic parameters. The Sauter diameter can hardly changed in range of the research and the Sauter diameters are around 10mm.