A flat submerged membrane combined with a TiO 2 /UV photocatalytic reactor (FSMPR) was employed in batch mode to remove humic acid (HA). HA removal efficiency was characterized by UV 254 absorbance, UV-vis spectra, di...A flat submerged membrane combined with a TiO 2 /UV photocatalytic reactor (FSMPR) was employed in batch mode to remove humic acid (HA). HA removal efficiency was characterized by UV 254 absorbance, UV-vis spectra, dissolved organic carbon (DOC) concentration, specific UV absorbance (SUVA), and trihalomethane formation potential (THMFP). The FSMPR process was effective in removing more than 86% of DOC and nearly 100% of UV 254 absorbance, while the THMFPs of samples were reduced to < 19 μ g/L after 150 min of treatment. In addition, changes in transmembrane pressure (TMP) with and without UV were evaluated; TiO 2 /UV was effective at controlling membrane fouling by HA. Analysis of the molecular weight (MW) distributions and three-dimensional excitation-emission matrix (EEM) fluorescence spectra of HAs revealed that the effectiveness in membrane fouling control is a result of changes in HA molecular characteristics. The TiO 2 /UV photocatalytic reactor caused the degradation of high MW, hydrophobic humic-like molecules to low MW, hydrophilic protein-like molecules, although this fraction was not completely removed during 150 min of treatment and was less responsible for membrane fouling.展开更多
This paper systematically examined the characteristics of dissolved organic matter(DOM) in a dynamic membrane bioreactor(DMBR) for municipal wastewater with a laboratory-scale continuous-flow device.Experimental resul...This paper systematically examined the characteristics of dissolved organic matter(DOM) in a dynamic membrane bioreactor(DMBR) for municipal wastewater with a laboratory-scale continuous-flow device.Experimental results showed that the system performed excellent pollutants' removal efficiencies.The increase of trans-membrane pressure(TMP) for the dynamic membrane(DM) could be divided into three stages,i.e.,zero increase stage,slow increase stage and abrupt rise stage.The maximal fouling rate of the DM reached to 4.34 kPa/h in abrupt rise stage.It was observed that the polysaccharides(PS) concentration of DOM samples gradually increased from the anaerobic zone to the aerobic zone in sequence,but the proteins(PN) concentration performed an opposite trend.The DM could retain a small part of the large molecular substances(>10 kDa) in the aerobic zone.Two particular fluorescence peaks appeared in the anaerobic zone and in the anoxic zone were also found in the effluent,which illustrated the dynamic cake layer closed to the stainless steel mesh might induce an anaerobic/anoxic micro environment.Based on the three-dimensional excitation-emission matrix(EEM) fluorescence spectroscopy analysis,aromatic proteins,aromatic proteinlike substance,fulvic acid-like substances and soluble microbial by-product-like materials could be biodegraded effectively in the DMBR,and the DM could partly remove the humic acid-like substances and soluble microbial by-product-like materials.展开更多
To achieve compact structure, light weight, and high thermal efficiency for the coal-fired boiler, the supercritical CO_2 power cycle has been considered as one of the promising alternatives in the coal-fired power co...To achieve compact structure, light weight, and high thermal efficiency for the coal-fired boiler, the supercritical CO_2 power cycle has been considered as one of the promising alternatives in the coal-fired power conversion system. One of the major problems concerning fossil fuel powered plants is the safety of the water wall in boiler design. In this work, the heat transfer characteristics of the supercritical CO_2 tube in the combustion chamber were determined through the low Reynolds number k-ε model, the gas real model and the P-1 radiation model. The study covered the supercritical CO_2 tube and the fins, and the annulus flue gas passage was also included. The wall temperature and the heat transfer coefficient were compared against those obtained from the experiments. Based on the examinations of the calculated flow and turbulence fields, the distributions of the velocity and the temperature inside the supercritical CO_2 tube in the combustion chamber were resolved numerically. Moreover, the effects of the heat transfer coefficient on the heat transfer characteristics were also discussed. And it was numerically focused on the influence of the inclined angle on the flow and the heat transfer of the supercritical CO_2 tube. The results show that the heat transfer coefficient keeps namely constant as the increasing inclined angle. It would help to better understand the heat transfer mechanism of unique characteristics of supercritical CO_2 above the pseudo-critical temperature, which may provide the corresponding theoretical basis on the optimization design of the coal-fired boiler.展开更多
With the development of industrial technology,heat transfer at the microscale has attracted more and more attention.In this work,200μm platinum wire and 150μm nickel-chromium wire were used as experimental objects,w...With the development of industrial technology,heat transfer at the microscale has attracted more and more attention.In this work,200μm platinum wire and 150μm nickel-chromium wire were used as experimental objects,which the power was provided by DC power with the range of 15.6 W to 56.2 W.Distilled water was used as the experimental liquid.Various bubbles on the micro wire were observed and the heat mechanism was analyzed.A variety of bubble attachment phenomena were captured on the 200μm platinum wire,including the adhesion during bubble detachment,the rotation of small attached bubbles on the surface of large bubble,multiple bubbles circling at the top of the same bubble,and different attached bubble departure phenomena.Marangoni force in the vertical direction triggered the formation of bubble attachment.In addition,the effects of surface tension,adhesion force and buoyancy force on the circling of the bubble were also considered.The analysis of the bubble sweeping on the 150μm nickel-chromium wire was analyzed.The results showed that the static bubble would interact with the sweeping bubbles on the other side,thereby changing the heat transfer mechanism,which was not discussed in detail before.The bubble jet flow generated by thermocapillary convection on the vertical direction of the bubble surface was the main influencing factor,which would change the microlayer encountered in front of the bubble.The effects of bubble diameter and liquid subcooling on the sweeping velocity were also studied.The results showed that the larger the bubble diameter was,the lower the sweeping velocity would be achieved while the liquid subcooling temperature had less impact on the velocity of sweeping bubble.展开更多
基金supported by the National Water Pollution Control and Treatment Key Technologies R&D Program (2008ZX07421-006 and 2009ZX 07424-006)
文摘A flat submerged membrane combined with a TiO 2 /UV photocatalytic reactor (FSMPR) was employed in batch mode to remove humic acid (HA). HA removal efficiency was characterized by UV 254 absorbance, UV-vis spectra, dissolved organic carbon (DOC) concentration, specific UV absorbance (SUVA), and trihalomethane formation potential (THMFP). The FSMPR process was effective in removing more than 86% of DOC and nearly 100% of UV 254 absorbance, while the THMFPs of samples were reduced to < 19 μ g/L after 150 min of treatment. In addition, changes in transmembrane pressure (TMP) with and without UV were evaluated; TiO 2 /UV was effective at controlling membrane fouling by HA. Analysis of the molecular weight (MW) distributions and three-dimensional excitation-emission matrix (EEM) fluorescence spectra of HAs revealed that the effectiveness in membrane fouling control is a result of changes in HA molecular characteristics. The TiO 2 /UV photocatalytic reactor caused the degradation of high MW, hydrophobic humic-like molecules to low MW, hydrophilic protein-like molecules, although this fraction was not completely removed during 150 min of treatment and was less responsible for membrane fouling.
基金supported by the National Natural Science Foundation of China (51138009,51208365,20976139)the State Key Laboratory of Pollution Control and Resource Reuse,China (PCRRY11015)+1 种基金the National Key Technologies R & D Program (2012BAJ21B03)the Project of the Science and Technology Commission of Shanghai Municipality(11dz1211202,11QH1402600)
文摘This paper systematically examined the characteristics of dissolved organic matter(DOM) in a dynamic membrane bioreactor(DMBR) for municipal wastewater with a laboratory-scale continuous-flow device.Experimental results showed that the system performed excellent pollutants' removal efficiencies.The increase of trans-membrane pressure(TMP) for the dynamic membrane(DM) could be divided into three stages,i.e.,zero increase stage,slow increase stage and abrupt rise stage.The maximal fouling rate of the DM reached to 4.34 kPa/h in abrupt rise stage.It was observed that the polysaccharides(PS) concentration of DOM samples gradually increased from the anaerobic zone to the aerobic zone in sequence,but the proteins(PN) concentration performed an opposite trend.The DM could retain a small part of the large molecular substances(>10 kDa) in the aerobic zone.Two particular fluorescence peaks appeared in the anaerobic zone and in the anoxic zone were also found in the effluent,which illustrated the dynamic cake layer closed to the stainless steel mesh might induce an anaerobic/anoxic micro environment.Based on the three-dimensional excitation-emission matrix(EEM) fluorescence spectroscopy analysis,aromatic proteins,aromatic proteinlike substance,fulvic acid-like substances and soluble microbial by-product-like materials could be biodegraded effectively in the DMBR,and the DM could partly remove the humic acid-like substances and soluble microbial by-product-like materials.
基金supported by the National Key R&D Program of China (2017YFB0601805)support from the Natural Science Foundation of Anhui Province (1708085ME108)
文摘To achieve compact structure, light weight, and high thermal efficiency for the coal-fired boiler, the supercritical CO_2 power cycle has been considered as one of the promising alternatives in the coal-fired power conversion system. One of the major problems concerning fossil fuel powered plants is the safety of the water wall in boiler design. In this work, the heat transfer characteristics of the supercritical CO_2 tube in the combustion chamber were determined through the low Reynolds number k-ε model, the gas real model and the P-1 radiation model. The study covered the supercritical CO_2 tube and the fins, and the annulus flue gas passage was also included. The wall temperature and the heat transfer coefficient were compared against those obtained from the experiments. Based on the examinations of the calculated flow and turbulence fields, the distributions of the velocity and the temperature inside the supercritical CO_2 tube in the combustion chamber were resolved numerically. Moreover, the effects of the heat transfer coefficient on the heat transfer characteristics were also discussed. And it was numerically focused on the influence of the inclined angle on the flow and the heat transfer of the supercritical CO_2 tube. The results show that the heat transfer coefficient keeps namely constant as the increasing inclined angle. It would help to better understand the heat transfer mechanism of unique characteristics of supercritical CO_2 above the pseudo-critical temperature, which may provide the corresponding theoretical basis on the optimization design of the coal-fired boiler.
基金The authors would like to thank the Anhui Provincial Natural Science Foundation(No.2008085J25)Project of support program for outstanding young people in Colleges and Universities(Grant No.gxyqZD201830)for their financial support of this study.
文摘With the development of industrial technology,heat transfer at the microscale has attracted more and more attention.In this work,200μm platinum wire and 150μm nickel-chromium wire were used as experimental objects,which the power was provided by DC power with the range of 15.6 W to 56.2 W.Distilled water was used as the experimental liquid.Various bubbles on the micro wire were observed and the heat mechanism was analyzed.A variety of bubble attachment phenomena were captured on the 200μm platinum wire,including the adhesion during bubble detachment,the rotation of small attached bubbles on the surface of large bubble,multiple bubbles circling at the top of the same bubble,and different attached bubble departure phenomena.Marangoni force in the vertical direction triggered the formation of bubble attachment.In addition,the effects of surface tension,adhesion force and buoyancy force on the circling of the bubble were also considered.The analysis of the bubble sweeping on the 150μm nickel-chromium wire was analyzed.The results showed that the static bubble would interact with the sweeping bubbles on the other side,thereby changing the heat transfer mechanism,which was not discussed in detail before.The bubble jet flow generated by thermocapillary convection on the vertical direction of the bubble surface was the main influencing factor,which would change the microlayer encountered in front of the bubble.The effects of bubble diameter and liquid subcooling on the sweeping velocity were also studied.The results showed that the larger the bubble diameter was,the lower the sweeping velocity would be achieved while the liquid subcooling temperature had less impact on the velocity of sweeping bubble.
