Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stab...Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.展开更多
Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Ch...Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Chemical routes,mainly the modified Siemens process,have dominated the preparation of polycrystalline SoG-Si;however,traditional chemical techniques employ a series of complex chemical reactions involving various corrosive and hazardous reagents.In addition,large amounts of complex waste solar cells and Si kerf slurry waste gradually accumulate and are difficult to recycle using these approaches.New methods are required to meet the demand for SoGSi preparation and Si waste recycling.The metallurgical route shows promise but is hindered by the problem of eliminating B and P from metallurgical-grade Si(MG-Si).Various pyrometallurgical treatments have been proposed to enhance the removal of B and P from MG-Si.This article reviews Si refining with slag treatment,chlorination,vacuum evaporation,and solvent refining,and summarizes and discusses the basic principles and recent representative studies of the four methods.Among these,solvent refining is the most promising and environmentally friendly approach for obtaining low-cost SoG-Si and is a popular research topic.Finally,a simple and green approach,i.e.,a combination of solvent refining,slag treatment,or vacuum directional solidification,is proposed for low-cost SoG-Si preparation using MG-Si or Si wastes as raw materials.展开更多
Due to the high salt content of coal chemical wastewater,pipeline fouling often occurs during wastewater treatment.Fouling will cause the diameter of the pipe to shrink or even block,which is not conducive to the safe...Due to the high salt content of coal chemical wastewater,pipeline fouling often occurs during wastewater treatment.Fouling will cause the diameter of the pipe to shrink or even block,which is not conducive to the safe and stable operation of the wastewater treatment process.In this paper,the experimental device was designed by using FLUENT software and the fouling deposition mechanisms at different flow velocities and different positions in a 90 deg bend were studied.The experimental results show that when the flow velocity is between 0.2 m·s^(-1) and 0.3 m·s^(-1),the thickness of fouling layer was positively correlated with the flow velocity;when the flow velocity is equal to 0.4 m·s^(-1),the formation of fouling is the most serious;when the flow velocity is between 0.4 m·s^(-1) and 0.7 m·s^(-1),the thickness of fouling layer was negative correlation with the flow velocity;with the increase of inlet velocity,the time for sediment point to develop into sediment surface is shortened.The fouling layer is easy to fall off because of the large shear force on the wall surface of the inner bend of the 90°elbow,so the density of sediment at this position is high.展开更多
基金financially supported by East-West Cooperation Project of Ningxia Key R&D Plan(2017BY064)National First-rate Discipline Construction Project of Ningxia(NXYLXK2017A04)。
文摘Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.
文摘Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Chemical routes,mainly the modified Siemens process,have dominated the preparation of polycrystalline SoG-Si;however,traditional chemical techniques employ a series of complex chemical reactions involving various corrosive and hazardous reagents.In addition,large amounts of complex waste solar cells and Si kerf slurry waste gradually accumulate and are difficult to recycle using these approaches.New methods are required to meet the demand for SoGSi preparation and Si waste recycling.The metallurgical route shows promise but is hindered by the problem of eliminating B and P from metallurgical-grade Si(MG-Si).Various pyrometallurgical treatments have been proposed to enhance the removal of B and P from MG-Si.This article reviews Si refining with slag treatment,chlorination,vacuum evaporation,and solvent refining,and summarizes and discusses the basic principles and recent representative studies of the four methods.Among these,solvent refining is the most promising and environmentally friendly approach for obtaining low-cost SoG-Si and is a popular research topic.Finally,a simple and green approach,i.e.,a combination of solvent refining,slag treatment,or vacuum directional solidification,is proposed for low-cost SoG-Si preparation using MG-Si or Si wastes as raw materials.
基金financially supported by the Natural Science Foundation of Ningxia Hui Autonomous Region(2020AAC03025)Undergraduate Training Programs for Innovation(2019107490001)+1 种基金East-West Cooperation Project of Ningxia Key R&D Plan(2017BY064)National First-rate Discipline Construction Project of Ningxia(NXYLXK2017A04)。
文摘Due to the high salt content of coal chemical wastewater,pipeline fouling often occurs during wastewater treatment.Fouling will cause the diameter of the pipe to shrink or even block,which is not conducive to the safe and stable operation of the wastewater treatment process.In this paper,the experimental device was designed by using FLUENT software and the fouling deposition mechanisms at different flow velocities and different positions in a 90 deg bend were studied.The experimental results show that when the flow velocity is between 0.2 m·s^(-1) and 0.3 m·s^(-1),the thickness of fouling layer was positively correlated with the flow velocity;when the flow velocity is equal to 0.4 m·s^(-1),the formation of fouling is the most serious;when the flow velocity is between 0.4 m·s^(-1) and 0.7 m·s^(-1),the thickness of fouling layer was negative correlation with the flow velocity;with the increase of inlet velocity,the time for sediment point to develop into sediment surface is shortened.The fouling layer is easy to fall off because of the large shear force on the wall surface of the inner bend of the 90°elbow,so the density of sediment at this position is high.