Characteristic And Application On Oxygen Active Species Injection Combined With Hydrodynamic Cavitation

At present,in the face of water pollution caused by urban domestic sewage discharge and industrial and agricultural production wastewater,and bio-invasion caused by oceanic trade,human beings need more efficient water treatment technology.Due to its high efficiency of hydroxyl radical(·OH)in water treatment,advanced oxidation technology(AOT)has been extensively studied.Along them,hydrodynamic cavitation-AOT is more likely to be used in large-scale applications.In recent years,various types of hydrodynamic cavitation-AOT have been proposed,but most of them have stopped at the laboratory scale and been far away from practical application.Hydrodynamic cavitation directly affects the process of generating ·OH and is the key to achieving scale application of AOT.In view of this,the paper is based on the new method of ·OH formation by oxygen active species combined with hydrodynamic cavitation.Aiming at the large-scale application of this new method,we have focused on the effect and mechanism of hydrodynamic cavitation on mixing oxygen active species and water,and realizing larger-scale application of the new method.The main research contents and results of the thesis are as follows:(1)For research of flow patterns of cavitating flow with oxygen active species or not,cavitation number,water mass flow ratios and cavitation image have been analyzed.The experimental results show that:?Both cavitating flow with OAS or not have choked flow mode and full-liquid flow mode.?The cavitation volume reduced with the increase of pressure ratios.?Natural suction capacity and hydrodynamic cavitation effects kept changing synchronously.?In the cavitating flow with OAs,the cavitation region was expanded by the OAS suction ?Hydrodynamic cavitation promoted the efficiency of ·OH formation by oxygen active species,and the conversion rate of oxygen active species reached 97%.(2)In order to investigate the role of hydrodynamic cavitation in the new method of ·OH formation,two-dimension numerical simulation study on cavitating flow without oxygen active species was carried out.The periodic variation of cavitation bubble volume fraction and spatial distribution,and the effect of pressure ratios on the cavitation periodic oscillation was confirmed.The numerical simulation results show that:?The volume fraction of cavitation bubbles decreased linearly with the increase of pressure ratios,and the cavitation effect gradually weakened with the pressure ratios increase.?Under different pressure ratios,the volume fraction and spatial distribution of cavitation bubbles showed periodic change.The cavitation bubble volume fraction tended to be stable over time.?Cavitation exhibited stable periodic oscillations only when the pressure ratio was 0.2.?Cavitation collapse only occurred at the end of the cavitation zone,so the effect of hydrodynamic cavitation occured only at the end of the cavitation zone.(3)In order to investigate the interaction between hydrodynamic cavitation and oxygen active species suction,three-dimension numerical simulation study on cavitating flow with oxygen active species was carried out.The numerical simulation results show that:?Oxygen active species destroied the cyclical variation of cavitation bubble volume fraction.?When oxygen active species was sucked in to hydrodynamic cavitation mixing reactor,oxygen active species fill the annular structure of the annular slit and rotate around the cross flow(water flow)firstly.Then,oxygen active species flow out of the annular slit and travel downstream along the wall of hydrodynamic cavitation mixing reactor.Until the cavitation collapsed,oxygen active species left the wall and mixed with the water.?The vortex due to cavitation collapse generated was the main reason for the complete uniform mixing of oxygen active species and water.The weighted coefficient of variation of oxygen active species was used to quantitative analysis the unmixed uniformity of oxygen active species and water.The weighted coefficient of variation of the outlet interface of the hydrodynamic cavitation mixing reactor was only 0.092%.Unmixed uniformity with hydrodynamic cavitation was 1/500 of the case without hydrodynamic cavitation.(4)In order to realize the large-scale application of the new method of ·OH formation by oxygen active species and hydrodynamic cavitation,large-flow hydrodynamic cavitation gas-liquid device has been built,and the hydrodynamic cavitation gas-liquid mixing effect was optimized and analyzed.The experimental results show that:?Large-flow hydrodynamic cavitation gas-liquid mixing device of H1×4 mode can obtain the best hydrodynamic cavitation gas-liquid mixing effect.?When the water flow rate is 33.51 m3/h,the oxygen active species conversion rate reached 66%.Based on the optimized process scheme of large-flow hydrodynamic cavitation gas-liquid system,containerized oxygen active species combined with hydrodynamic cavitation water treatment equipment was developed.For this containerized equipment,its operating discharge power is less than 20 kW,water treatment capacity is 15?40 m3/h,and its total reactive oxidant concentration is adjustable from 0 to 10 mg/L.In summary,this paper is aimed at the problem that high-concentration oxygen active species cannot able to mix and react efficencily with large-flow water bodies in large-scale application of the new method of·OH formation,numerical simulation and experimental study on the mechanism and effect of hydrodynamic cavitation on gas-liquid mixing efficiency of oxygen active species and water have been carried out.The cavitating flow pattern with oxygen active speices was ascertained,and mechanism of the interaction between oxygen active speices and hydrodynamic cavitating flow wasrevealed.A large-flow hydrodynamic cavitation gas-liquid mixinge device was constructed,and containerized oxygen active species combined with hydrodynamic cavitation water treatment equipment with a treatment capacity of 40 m3/h was developed.