Chaotic mixing is regarded as an effective method to improve the mixing effect in the laminar stirred tank.To generate chaos in flow field in stirred tank,many efforts including aperiodic movement,asystematic installation impeller,etc.,were made to save mixing time and energy consumption.The computational fluid dynamics of chaotic flow field and the hyperchaotic controlling method as well as macro-instability were reviewed.Multiple flow field coupling is important in the turbulent mixing region of stirred tank.The development trends of flow field coupling and hyperchaotic controlling in chaotic mixing were prospected in energy saving operation.
Macro-instability(MI)is an important natural phenomenon affecting the mixing performance in stirred tank significantly,which results from movement and evolution of large eddies.Factors associated with MI frequency in mixing operation and energy dissipation related to MI were reviewed.Flow pattern in turbulent regime contains many coherent structures,which have much energy vortices and may result in flow field MI.Adjustment of coherent structure and controlling MI may contribute to energy saving and good mixing performance.Controlling methods for MI was prospected.
Ammonia is the major pollutant in many industrial and agricultural wastewaters,while with an increasing demand for nitrogen fertilizer worldwide,recovery of ammonia from high concentration ammonium wastewater is a significant way to reduce environmental pollution and to meet the development requirements.The present work was to investigate the factors following pH value,molar ratio of chemical reagents to afford theoretical support for wastewater treatment and resource recycling.Precipitate of struvite was analyzed by X-ray diffraction(XRD).Results indicated that by formation of magnesium ammoniumphosphate,ammonium in steel wastewater could be removed under the conditions following pH 10,with molar ratio of PO43-∶NH4+∶Mg2+ 1.3∶1∶1.2,and the ammonium removal efficiency was up to 95%.
