| As a new type of process-enhanced reaction equipment,gas-liquid Reverse Jet Loop Reactor(RJLR)could achieve much higher mixing efficiency than traditional stirred tank reactor under the low energy consumption.And it was widely used in multi-phase reaction system limited by mass transfer or heat transfer processes.Although gas-liquid RJLR had shown good application prospects in the fields of chemical industry,environmental protection and bio-pharmaceuticals,relatively speaking,the study on its internal flow characteristics was still imperfect.Both experimental and simulation studies were relatively limited and had specific scope of application.At present,the design of gas-liquid RJLR still needs a large amount of experimental work.Therefore,it was of great significance to conduct in-depth research on it,especially to study the flow characteristics of fluids in equipment,and to reveal the essential reasons that affected the macro-performance of the reactor.In this paper,the air-water system was used as the research object,and the experimental device of gas-liquid RJLR was established.The annulus gas holdup ?a,Particle Size Distribution(PSD)of bubble and Residence Time Distribution(RTD)of liquid were used as the parameters of reactor performance.The respective analysis methods were established,and systematic experimental research was carried out on the factors affecting the three parameters.The results showed that ?a increased with the increase of gas phase flow,liquid phase flow and gas-liquid ratio,and the influence of nozzle position was relatively small.The PSD of bubbles was conformed to the lognormal distribution pattern.The average diameter and distribution range of the bubble increased with the increase of the gas flow rate,and decreased with the increase of the liquid flow rate,the downward movement of the nozzle and the increase of the diameter of draft tube.Under the experimental conditions,the RTD of liquid was closed to the CSTR.The degree of backmixing increased with increase of the diameter of draft tube.With the increase of gas and liquid flow rate and the downward shift of nozzle position,the degree of backmixing increased first and then decreased.When the gas flow rate was 0.75 m3·h-1,the liquid phase flow rate was 1.3 m3·h-1,and the nozzle moved down to 38 mm below the upper edge of the draft tube,the backmixing degree in the reactor reached the maximum.On the basis of experiments,Computational Fluid Dynamics(CFD)model ofgas-liquid RJLR was established to obtain more detailed flow field information.The reliability of the model was verified by experimental data.On this basis,the effects of different liquid flow rates and nozzle positions on the liquid circulation ratio and the distribution of liquid velocity in draft tube and annulus of reactor were studied.The results showed that the radial distribution of the liquid velocity in the draft tube was parabolic.The liquid velocity reached the maximum at the centerline and gradually decreased along the radial direction.At the same time,the liquid velocity gradually increased with the increase of liquid flow rate and the downward movement of nozzle position.The liquid velocity of the annulus increased with the increase of liquid flow rate and the downward movement of nozzle position.With the flow of fluid,the maximum radial velocity moved gradually from the vicinity of reactor wall to the draft tube,and the radial velocity gradient decreased gradually.The liquid circulation ratio(R)increased linearly with the increase of liquid flow rate,and increased first and then decreased with the downward movement of nozzle position.When the nozzle moved down to 38 mm below the upper edge of the draft tube,R reached the maximum. |
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