Study On The Hydrodynamic Behavior And Performance Optimization Of Electorn Beam Water Treatment Reactor

Water pollution is one of the most significant environmental issues in China and the world.Electron beam(EB)treatment of water,which is a new technology for water treatment,provides a new way to remove the pollutants that can not be degraded by traditionl water treatment technology.A lot of researches have been conducted to study the reaction kinetics of EB water treatment.However,relatively less attention has been paid to the hydrodynamic behavior and absorbed dose distribution of the EB reactor which is crucially important for the EB treatment efficiency.The nozzle jet EB reactor is selected as the research object in this paper for its relatively large treatment capacity.By means of theoretical analysis,numerical simulation,and experimental research methods,the behavior of the EB reactor is studied,mainly including the EB density distribution on water surface,hydrodynamic behavior of the flow within the EB reactor,hydrodynamic behavior of the jet flow ejected from the EB reactor and absorbed dose distribution of the flow.The influences of the flow characteristic on the uniformity of absorbed dose distribution and on the EB disinfection efficiency are discussed in this paper.The following results are obtained:By means of theoretical analysis and computational research,a critical nondimensional physical quantity that influence the EB density distribution on water surface is proposed in this paper.The non-dimensional physical quantity is VT / d,where V is the flow velocity,d is the diameter of the EB spot,and T is the EB scaningn period.The less the VT / d is,the more uniformity of the EB density distribution on water surface will be.When the VT / d is less than 0.9,the EB density distribution on water surface could be considered as uniform.The velocity and thickness of the flow under electron beam should be evenly distributed to improve the efficiency of the EB reactor.A three dimensional hydrodynamic model of the reactor is built to study the influence of the EB reactor configuration on the hydrodynamic of the flow based on the CFD method.The optimal configuration parameters of the EB reactor,which are determined based on the model,were as follows: the diameter of the reactor inlet is 0.2m,the length of the horizontal contraction part is 0.45 m,and the configuration of the bending part should be along the flow velocity direction.The outlet flow velocity and thickness of the optimal EB reactor are evenly distributed,which is verified by experiment.An Eulerian air-liquid two phase flow model is built to calculate the density and thickness distribution of the aerated flow ejected from the EB reactor based on the CFD method.The heat transfer caused by electron beam is considered in the model.Based on the simulation result of the two phase flow model,Monte Carlo method is used to calculate the energy deposition of electron beam in the aerated flow.The aeration of the flow decreases the optimal penertration depth(?h)of electron beam in water.Monte Carlo method is used to calculate the absorbed dose distribution of the aerated flow.The influence of the water characteristic on the uniformity of the absorbed dose distribution and the EB reactor disinfection efficiency is studied.The influence of the velocity,width,thickness and aeration of the flow on the EB reactor treatment efficiency is discussed based on the study.The influence of the flow velocity on the EB reactor treatment efficiency could be ignored when the flow velocity is less than 0.9d / T.The influence of the flow width on the EB reactor treatment efficiency could be ignored when the flow width is less than 0.89 times of the valid EB radiation width.