Advanced Treatment Reactor Technology For Papermaking Wastewater Based On Computational Fluid Dynamics

China's paper industry had been growing along with its nation's GDP growth for more than thirty years,It has become the largest production country and the biggest consumption market for paper and paperboard products in the world.Meanwhile,China's paper industry has become the main resource of waste water discharge and COD emissions.The energy-saving and emission reduction technologies are urgent required by this industry.With the gradual strict national environmental protection standards,to develop useful advanced wastewater treatment technologies for papermaking industrial,at lower cost,with higher efficiency,has been focusing by researchers,but there are still blind spots at aspect of hydraulic fluid of advanced treatment technologies.This thesis conducted a systematic study in this field.Advanced treatment reactor consists of pre-mixing modular and main reacting modular based on modular design.Static mixer is used as a pH control and chemical mixing equipment,Simulated by fluent,it shows that the maximum velocity vector of commercial mixer concentrates in the near wall region the fluid swirling is a same direction with less fluid redirection.Due to the change of flow direction through each mixing unit,the designed mixer has better redirection function and more efficient mixing.The intensity of segregation of designed mixer is 2.10×10-4 through four mixing unit,while which of commercial mixer is 6.45×10-4?less intensity of segregation more mixing efficiency?,Designed mixer was choosed with the main structural parameters: four mixing units,250 mm length of each mixing unit,the contrary spin of adjacent mixing unit.PID control for pH value adjustment was improved.Single loop control system was replaced by cascade loop control taking acid dosage which is less lag as a deputy circuit,the effects of time delay was overcame.Fluctuation limit module was used to reduce the impact of the process resulted from mutation of measurement parameters or improper operation.Redundant pH meters were installed to eliminate effects of pH meter fails by checking the output of every p H meter.The requirements of pH responsive can be meet through static mixer designing and PID control improving.Simulated with Fluent,swirling water distributor can make a fine mixing effect as similar with the flow pattern of paddle agitator.Discrete Phase Model showed the residence time of swirling water distributor is 846 s,while which of cone water distributor is 1540 s,as swirling water distributor has less retention time and less back flow,it can be used for wastewater advanced reatment reactor.Numerical simulation for catalyst unit showed that the laminar flow without mixing effect is occured after throughing catalysts.The catalyst unit was optimized by helical baffle with one-third sector and 18°helical angle installed up the catalysts,then the velocity vector was divergent and fluid was mixed efficient after optimizing,the velocity was nearly four times than that before.The pressure drop of optimized catalyst unit was mainly located at the inlet,which is 631.14 Pa,then is 236.6Pa and 142.92 Pa at the two catalysts,the pressure loss of helical baffle could be ignored.Air-water mixing unit was designed.Main reacting modular was formed.The hydraulic flow states of each internal mixing pieces in a constituted reactor,such as air-water mixing unit?AW?,flow-folding unit?FF?and filler-basket unit?FB?,were investigated individually,using tracing-agent technique.The results show that: air and water are quickly mixed thoroughly by AW unit,the pattern of tracing agent duration curves,by change of air flow from 0.60L/min to 0.06L/min,show likely similar.Minor air flow also can guarantee mixing effect,the series number N of AW unit from 1.230 to 1.808,ensuring the hydraulic flow at a complete full mixed state;There is a dead zone in FF unit,the series number N of FF unit from 3.311 to 3.776,its hydraulic flow shows likely plug-flow state;The series number N of FB unit from 4.265 to 5.869,its hydraulic flow shows likely plug-flow state too.Experimental trials were carried out in several types constituted reactor with different combination of mixing units,results show that the better COD removal efficieny is able to be obtained by using FB+AW mixing units combination than FF+AW and FB+FF combinations,with the highest COD removal efficiency of 93.2%,also higher than that of each AW,FF or FB unit alone installed in the reactor.The COD removal efficiency by the Fenton's reagent treatment aiding with Ultrasonic wave is better than both that by Fenton or Ultrasonic wave,individually;the order of effective significance by each factors can be lined up as: the initial pH value > ultrasonic power > chemical dosage > ultrasonic treatment time.The proposed optimal conditions by orthogonal experimental tests are illustrated as: initial pH values 6,ultrasonic power 10 W,chemical dosage 0.3 mL,ultrasonic treatment time 11 min.,resulting a effluent with COD of 23.6 mg/l while the influent with COD of 380.4mg/L,colour of 570 times,to meet the emission standard of GB 3544-2008 completely;On other hand,Ultrasonic wave can play a role in anti-scaling,as a means for promoting long-term catalyst efficiency.The designed advanced treatment reactor and ordinary Fenton reactor were used to treat papermaking secondary biochemical effluent?hereinafter biochemical effluent?,the results showed The designed advanced treatment reactor treated biochemical effluent well,the effect is better than ordinary Fenton reactor.COD removal efficiency up to 93%.By researching the operating parameters,optimal processes were: packed 10%,initial pH value 6.0,Fe²⁺ and H₂O₂ dosage are 3.24mmol/L,gas flow 0.06L/min.Researching on pollutants conversion and degradation law of comprehensive wastewater,biochemical effluent and treated water.it shows biochemical effluent contains various alcohol and phenol material,treated water contains Butylated Hydroxytoluene and 2,6-Di-tert-butyl-p-benzoquinone,which are 73.99% and 7.69% of total organic,others are various alcohol,quinone,ester,aldehyde,content less 5%.After advanced treatment,the higher content of 1,1-diethyl acetal and epoxy propyl alcohol had been removed,Butylated Hydroxytoluene is hard to treat,so the relative content increased significantly.