Research On Working Characteristics Of Spiral Symmetry Stream Anaerobic Bioreactor

The pressure of water environment and energy demand have been increasing in recent years.Anaerobic digestion technology can not only control waste water pollution,but also produce biogas energy.Therefore,the development and application of a new highly-efficient anaerobic reactor can strongly promote Chinese environmental protection and new energy business undoubtedly.Spiral Symmetry Stream Anaerobic Bioreactor?SSSAB?is a highly-efficient anaerobic reactor.Studying its working characteristics can help to master the principles and rules of operation,improve the efficiency of treatment,and lay the foundation for engineering application and popularization.In this paper,the structural characteristics,flow field characteristics,operation characteristics and sludge characteristics of the SSSAB reactor are systematically investigated.The main results are as follows.?1?The water distribution unit,spiral reaction unit and three-phase separation unit are analyzed in this paper in order to study the structural characteristics of SSSAB reactor.The simulation results show that:?1?In the distribution unit,the uniform area proportion increases with the number of orifices increasing.?2?In the piral reaction unit,with the cutting angle increasing,the axial velocity increases,the tangential velocity reduces,and the radial velocity is often neglected as its absolute value is very small compared with the axial velocity and the tangential velocity.With the installation angle increasing,the spiral flow area decreases gradually.The 180osymmetrical arrangement of 2 plates forms two independent spiral flow in the vicinity of the upper and lower plates respectively.The 120osymmetrical arrangement of 3 plates forms a strong–weak periodic spiral flow.The 180osymmetrical arrangement of 4 plates forms strong spiral flow in the whole region.?3?In the three-phase separation unit,with the characteristic parameter i?i=r₁/r₂,where r₁ presents the bottom frustum radius of reverse cone,and r₂ presents radius of spiral reaction unit of SSSAB reactor?increasing,the recirculation area and dead zone reduces.?4?In order to test the reliability of CFD model,the fluorine ion tracer test is used to compare with the simulation results.Results show that:the dead zone rate of CFD simulation is 15.34%,and the dead zone rate of fluorine ion tracer test is 20.00%.The relative error between them is 4.66%,which indicates that the CFD model establishes in this paper having good prediction and can well reflet the actual flow situation.?2?The flow field characteristics of SSSAB reactor are studied by fluorine ion tracer test.?1?The mixing model characteristics of SSSAB reactor under different conditions are described:the back-mixing is small and the flow pattern tends to be plug flow when the collecting gas pipes are clear or the collecting gas pipes are blocked at low loading rate,and the back-mixing is large and the flow pattern tends to be complexly mixed flow when the collecting gas pipes are blocked at medium,high or super high loading rate.?2?The regression equations between the number of series N,the volume hydraulic load L(L·L^-1·d^-1)and the volume gas producing rate G(L·L^-1·d^-1)are as followings:N=-0.312L+0.020G+4.322?R²=0.982?when the collecting gas pipes are clear and N=-0.027L-0.041G+3.942?R²=0.986?when the collecting gas pipes are blocked.?3?The efficient characteristics of SSSAB reactor are studied.With the hydraulic retention time?HRT?decreasing,the total dead zone and hydraulic dead zone of the reactor increase gradually.The efficiency of the reactor increases gradually with the increase of the number of series N,but the amplitude decreases gradually.?3?In order to investigate the treatment effect of SSSAB on organic wastewater,a load experiment is carried out with sucrose solution to simulate high concentration wastewater.The results show:?1?The start-up time of the SSSAB reactor is only 25 days,and it shows the characteristic of quick start-up.When the influent substrate concentration is 20.070 kg·m^-3 and the HRT is 2.7 h,the volume removal rate can reach up to 118.293 kgCOD·m^-3·d^-1,and the performance is in the forefront at home and abroad.The SSSAB reactor has good stability,but the stability decreases with the increase of volume load.?2?The orthogonal experiment is carried out and the optimum combination of operating conditions is:temperature 35oC,C:N:P=250:5:1,trace element 1.0 ml·L^-1,pH=7.8.The influence of operation conditions on reactor volume removal rate are temperature,pH,C:N:P and trace elements.?4?The granular sludge characteristics in different phases and different locations are studied.?1?On the 120th day,TSS,VSS and VSS/TSS reach the peak.From bottom to top,sludge concentration gradually decreases,stability gradually increases,TSS,VSS,CV values gradually decrease.?2?On the 110th day,the flocculating parametres of granular sludge reach the best value.From bottom to top,the coagulability and stability increase,zeta potential decreases,contact angle increases,and Ca/Mg ion content gradually increases,CV value decreases gradually.?3?On the 120th day,the precipitation characteristics of the granular sludge are the best.From bottom to top,the sedimentation and stability gradually increase,the particle size and density gradually increase,and the CV value gradually decreases.?4?On the 120th day,Specific Methanogenic Activcity?SMA?reaches its peak.From bottom to top,biological activity and stability increase,SMA value increases,and CV value decreases gradually.