CO_(2) hydrogenation to CH3OH is of great significance for achieving carbon neutrality.Here,we show a urea-assisted grinding strategy for synthesizing Cu-Zn-Ce ternary catalysts(CZC-G)with optimized interfacial synerg...CO_(2) hydrogenation to CH3OH is of great significance for achieving carbon neutrality.Here,we show a urea-assisted grinding strategy for synthesizing Cu-Zn-Ce ternary catalysts(CZC-G)with optimized interfacial synergy,achieving superior performance in CO_(2) hydrogenation to methanol.The CZC-G catalyst demonstrated exceptional methanol selectivity(96.8%)and a space-time yield of 73.6 gMeOH·kgcat^(–1)·h^(–1) under optimized conditions.Long-term stability tests confirmed no obvious deactivation over 100 h of continuous operation.Structural and mechanistic analyses revealed that the urea-assisted grinding method promotes the formation of Cu/Zn-O_(v)-Ce ternary interfaces and inhibits the reduction of ZnO,enabling synergistic interactions for efficient CO_(2) activation and selective stabilization of formate intermediates(HCOO^(*)),which are critical for methanol synthesis.In-situ diffuse reflectance infrared Fourier transform spectra and X-ray absorption spectroscopy studies elucidated the reaction pathway dominated by the formate mechanism,while suppressing the reverse water-gas shift reaction.This work underscores the critical role of synthetic methodologies in engineering interfacial structures,offering a strategy for designing high-performance catalysts for sustainable CO_(2) resource utilization.展开更多
Experiments were made for the adsorption of CO2 and N2 on typical adsorbents to investigate the effects of porous structure and surface affinity of adsorbents as well as those of adsorption temperature and pressure th...Experiments were made for the adsorption of CO2 and N2 on typical adsorbents to investigate the effects of porous structure and surface affinity of adsorbents as well as those of adsorption temperature and pressure that might cause the variation of adsorption mechanism. It is shown that polar surface tends to enlarge the adsorption difference between CO2 and N2, and the difference is more sensitive to temperature than the adsorbents with non-polar surface. The adsorbents with non-polar surface are not much sensitive to the effect of water vapor, though the water vapor interferes the separation remarkably. The separation coefficient linearly increases with the micro- pore volume per unit surface area of activated carbons, but no rule is shown on mesoporous silicon materials. The function of adsorption mechanism on the separation is not as much as expected.展开更多
Process optimization in equation-oriented(EO)modeling environments favors the gradient-based optimization algorithms by their abilities to provide accurate Jacobian matrices via automatic or symbolic differentiation.H...Process optimization in equation-oriented(EO)modeling environments favors the gradient-based optimization algorithms by their abilities to provide accurate Jacobian matrices via automatic or symbolic differentiation.However,computational inefficiencies including that in initial-point-finding for Newton type methods have significantly limited its application.Recently,progress has been made in using a pseudo-transient(PT)modeling method to address these difficulties,providing a fresh way forward in EO-based optimization.Nevertheless,research in this area remains open,and challenges need to be addressed.Therefore,understanding the state-of-the-art research on the PT method,its principle,and the strategies in composing effective methodologies using the PT modeling method is necessary for further developing EO-based methods for process optimization.For this purpose,the basic concepts for the PT modeling and the optimization framework based on the PT model are reviewed in this paper.Several typical applications,e.g.,complex distillation processes,cryogenic processes,and optimizations under uncertainty,are presented as well.Finally,we identify several main challenges and give prospects for the development of the PT based optimization methods.展开更多
This article aims tomodel and analyze the heat and fluid flow characteristics of a carboxymethyl cellulose(CMC)nanofluid within a convergent-divergent shaped microchannel(Two-dimensional).The base fluid,water+CMC(0.5%...This article aims tomodel and analyze the heat and fluid flow characteristics of a carboxymethyl cellulose(CMC)nanofluid within a convergent-divergent shaped microchannel(Two-dimensional).The base fluid,water+CMC(0.5%),is mixed with CuO and Al2O3 nanoparticles at volume fractions of 0.5%and 1.5%,respectively.The research is conducted through the conjugate usage of experimental and theoretical models to represent more realistic properties of the non-Newtonian nanofluid.Three types of microchannels including straight,divergent,and convergent are considered,all having the same length and identical inlet cross-sectional area.Using ANSYS FLUENT software,Navier-Stokes equations are solved for the laminar flow of the non-Newtonian nanofluid.The study examines the effects of Reynolds number,nanoparticle concentration and type,and microchannel geometry on flow and heat transfer.The results prove that the alumina nanoparticles outperform copper oxide in increasing the Nusselt number at a 0.5% volume fraction,while copper oxide nanoparticles excel at a 1.5%volume fraction.Moreover,in the selected case study,as the Reynolds number increases from 100 to 500,the Nusselt number rises by 56.26% in straight geometry,52.93% in divergent geometry,and 59.10%in convergent geometry.Besides,the Nusselt number enhances by 18.75% when transitioning from straight to convergent geometry at a Reynolds number of 500,and by 19.81%at a Reynolds number of 1000.Finally,the results of the research depict that the use of thermophysical properties derived from the experimental achievements,despite creating complexity in the modeling and the solution method,leads to more accurate and realistic outputs.展开更多
For the efficient harnessing of solar energy and mitigation of environmental pollution,the develop-ment and application of semiconductor photocatalysis technology is paramount.Herein,a novel SubPc-Br/CdS supramolecula...For the efficient harnessing of solar energy and mitigation of environmental pollution,the develop-ment and application of semiconductor photocatalysis technology is paramount.Herein,a novel SubPc-Br/CdS supramolecular array with an S-scheme heterojunction was synthesized through the intermolecu-larπ-stacked self-assembly of subphthalocyanine(SubPc-Br)and nanometer cadmium sulfide(CdS).This self-assembly system features a highly structured architecture and excellent stability.Experiments and ground-state differential charge calculations demonstrate that SubPc-Br and CdS form a built-in electric field during the self-assembly process,a critical factor in promoting the dissociation of electrons and holes.Additionally,this study utilized time-dependent density functional theory(TDDFT)to simulate the dynamic adsorption behavior of excited oxygen molecules on the SubPc-Br/CdS interface for the first time.The analysis of molecular charge differential density under different excited states proved that the addi-tion of SubPc-Br molecules not only improves the photocorrosion resistance of CdS in an O2 adsorption environment but also enhances the production of advanced reactive oxygen species under the synergistic action of h+and·O2-.When subjected to visible light,the degradation efficiency of minocycline(MC)achieved 96.8%within 60 min and maintained 80.3%after 5 cycles.In summary,this study highlights the feasibility of creating advanced S-scheme heterojunction photocatalysts through the strategic incor-poration of organic supramolecules with semiconductor catalysts.展开更多
The separation between methane and nitrogen is an inevitable and important task in the C1 chemicaltechnology and the utilization of methane from coalbed, yet it is considered to be one of the tough tasks in thefield o...The separation between methane and nitrogen is an inevitable and important task in the C1 chemicaltechnology and the utilization of methane from coalbed, yet it is considered to be one of the tough tasks in thefield of separation. Pressure swing adsorption is a preferable technology if an adsorbent that allowing a largecoefficient of separation for the CH4/N2 system is available. The separation coefficients between CH4 and N2were obtained on analyzing the breakthrough curves measured experimentally with nine adsorbents. A technique ofmeasuring the temperature-pulse was incorporated in the experiments, and the reliability of the result was improved.Superactivated carbon with large surface area and plenty of micropores was shown to have the largest separationcoefficient and to be promising for the commercial utilization.展开更多
The performance of combined Fenton oxidation and membrane bioreactor （MBR） process for the advanced treatment of an effluent from an integrated dyeing wastewater treatment plant was evaluated. The experimental resul...The performance of combined Fenton oxidation and membrane bioreactor （MBR） process for the advanced treatment of an effluent from an integrated dyeing wastewater treatment plant was evaluated. The experimental results revealed that under the optimum Fenton oxidation conditions （initial pH 5, H 2 O 2 dosage 17 mmol/L, and Fe^ 2＋ 1.7 mmol/L） the average total organic carbon （TOC） and color removal ratios were 39.3% and 69.5% after 35 min of reaction, respectively. Results from Zahn-Wallens Test also represented that Fenton process was effective to enhance the biodegradability of the test wastewater. As for the further purification of MBR process, TOC removal capacity was examined at different hydraulic retention times （HRT） of 10, 18 and 25 hr. Under the optimum HRT of 18 hr, the average TOC concentration and color of the final MBR effluent were 16.8 mg/L and 2 dilution time, respectively. The sludge yield coefficient was 0.13 g MLSS/g TOC and TOC degradation rate was 0.078 kg TOC/（m ^3 ·day）. The final effluent of MBR can meet the reuse criteria of urban recycling water – water quality standard for miscellaneous water consumption GBT18920-2002.展开更多
The reactions of exo-cellulase （cellobiohydrolase, CBH） and endo-cellulase （endoglucanase, EG） were investigated by analyzing the insoluble residues of microcrystalline cellulose （MCC） and filter paper cellulose...The reactions of exo-cellulase （cellobiohydrolase, CBH） and endo-cellulase （endoglucanase, EG） were investigated by analyzing the insoluble residues of microcrystalline cellulose （MCC） and filter paper cellulose （FPC） during enzymatic hydrolysis. Molecular parameters including molecular weight and its distribution, degree of polymerization, and radii of gyration were measured by size exclusion chromatography coupled with multi-angle laser light scattering. No significant change in MCC chains was found during the whole reaction period, indicating that CBH digestion follows a layer-by-layer solubilization manner. This reaction mode might be the major reason for slow enzymatic hydrolysis of cellulose. On the other hand, the degree of polymerization of FPC chains decreases rapidly in the initial reaction, indicating that EG digestion follows a random scission manner, which may create new ends for CBH easily. The slopes of the conformation plots for MCC and FPC increase gradually, indicating stronger chain stiffness of cellulose during hvdrolvsis展开更多
Membrane separation technology has popularized rapidly and attracts much interest in gas industry as a promising sort of newly chemical separation unit operation. In this paper, recent advances on membrane processes f...Membrane separation technology has popularized rapidly and attracts much interest in gas industry as a promising sort of newly chemical separation unit operation. In this paper, recent advances on membrane processes for CO_2 separation are reviewed. The researches indicate that the optimization of operating process designs could improve the separation performance, reduce the energy consumption and decrease the cost of membrane separation systems. With the improvement of membrane materials recently,membrane processes are beginning to be competitive enough for CO_2 separation, especially for postcombustion CO_2 capture, biogas upgrading and natural gas carbon dioxide removal, compared with the traditional separation methods. We summarize the needs and most promising research directions for membrane processes for CO_2 separation in current and future membrane applications. As the time goes by, novel membrane materials developed according to the requirement proposed by process optimization with increased selectivity and/or permeance will accelerate the industrialization of membrane process in the near future. Based on the data collected in a pilot scale test, more effort could be made on the optimization of membrane separation processes. This work would open up a new horizon for CO_2 separation/Capture on Carbon Capture Utilization and Storage(CCUS).展开更多
An economic and effective method of preparing enriched 10B boric acid was established by chemical reactionof enriched 10BF3 and CaCO3. A process of boron trifluoride reacting with water was investigated under certainc...An economic and effective method of preparing enriched 10B boric acid was established by chemical reactionof enriched 10BF3 and CaCO3. A process of boron trifluoride reacting with water was investigated under certainconditions. Calcium carbonate was selected to counteract hydrofluoric acid followed on. Some key operation factorswere investigated, such as temperature, reaction time and the ratio of CaCO3 to 10BF3. The results showed that the yieldof enriched 10B boric acid could reach 97. 2% and the purity was up to 94. 1% under the following conditions: the temperaturewas 50-60,℃, the reaction time was 28 h and the ratio of CaCO3 to 10BF3 was 4. In addition, after recrystallizationand titration analysis, the purity of the product could reach over 99. 2% from 94.1%.展开更多
To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali...To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali-dation of flow simulation. In this work, the velocity profiles of single-phase flow in structured packing are measured at the Reynolds numbers of 20.0, 55.7 and 520.1, using the laser Doppler velocimetry （LDV）. The time-averaged and instantaneous velocities of three components are obtained simultaneously. The CFD simulation is also carried out to numerically predict the velocity distribution within the structured packing. Comparison shows that the flow pattern, velocity distribution and turbulent kinetic energy （for turbulent flow） on the horizontal plane predicted by CFD simulation are in good agreement with the LDV measured data. The values of the x-and z-velocity components are quantitatively well predicted over the plane in the center of the packing, but the predicted y-component is sig-nificantly smaller than the experimental data. It can be concluded that experimental measurement is important for further improvement of CFD model.展开更多
Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups whichcan be used as carriers of CO2 were prepared. One was poly(N-vinyl-γ-sodium aminobutyrate)(PVSA), whichwas obtained th...Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups whichcan be used as carriers of CO2 were prepared. One was poly(N-vinyl-γ-sodium aminobutyrate)(PVSA), whichwas obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) byradical polymerization. The other was poly(N-vinyl-γ-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), whichwas obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). Thecomposite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as supportmembranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 throughthe composite membranes were measured. The results show that the composite membranes present better CO2permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2pressure, the PVSA/PS composite membrane displays a CO2 permeation rate of 5.95 × 10-7 cm3.cm-2.s-1.pa-1with CO2/CH4 ideal separation factor of 212.1. At 20℃, 6400Pa of CO2 pressure, the VSA-SA/PS compositemembrane displays a CO2 permeation rate of 4.24 × 10-8 cm3@cm-2.s-1.Pa-1 with CO2/CH4 ideal separationfactor of 429.7. The results with the gas mixtures are not as good as those obtained with pure gas because ofthe coupling effects between CO2 and CH4. The heat cross-linked membrane shows good separation factor due todensification of the polymer.展开更多
The problem of optimal synthesis of an integrated water system is addressed in this study, where water using processes and water treatment operations are combined into a single network such that the total cost of fres...The problem of optimal synthesis of an integrated water system is addressed in this study, where water using processes and water treatment operations are combined into a single network such that the total cost of fresh water and wastewater treatment is globally minimized. A superstructure that incorporates all feasible design alterna- tives for wastewater treatment, reuse and recycle, is synthesized with a non-linear programming model. An evolutionary approach--an improved particle swarm optimization is proposed for optimizing such systems. Two simple examples are .Presented.to illustrate the global op.timization of inte.grated water networks using the proposed algorithm.展开更多
Recent advances on mixed matrix membrane for CO<sub>2</sub> separation are reviewed in this paper. To improve CO<sub>2</sub> separation performance of polymer membranes, mixed matrix membranes ...Recent advances on mixed matrix membrane for CO<sub>2</sub> separation are reviewed in this paper. To improve CO<sub>2</sub> separation performance of polymer membranes, mixed matrix membranes (MMMs) are developed. The concept of MMM is illustrated distinctly. Suitable polymer and inorganic or organic fillers for MMMs are summarized. Possible interface morphologies between polymer and filler, and the effect of interface morphologies on gas transport properties of MMMs are summarized. The methods to improve compatibility between polymer and filler are introduced. There are eight methods including silane coupling, Grignard treatment, incorporation of additive, grafting, in situ polymerization, polydopamine coating, particle fusion approach and polymer functionalization. To achieve higher productivity for industrial application, mixed matrix composite membranes are developed. The recent development on hollow fiber and flat mixed matrix composite membrane is reviewed in detail. Last, the future trend of MMM is forecasted.展开更多
Energy recovery device （ERD） is an important part of the seawater reverse osmosis （SWRO） desalination system. There are principally two kinds of ERDs, the centrifugal type and the positive displacement （PD） type...Energy recovery device （ERD） is an important part of the seawater reverse osmosis （SWRO） desalination system. There are principally two kinds of ERDs, the centrifugal type and the positive displacement （PD） type. The PD type is of extensive concern and is preferred in large-scale plants. In this article, an innovative fluid switcher was presented and a two-cylinder hydraulic energy recovery unit with a lab-scale fluid switcher was set up. Tap water was used as the working medium instead of the actual seawater and brine in SWRO desalination plants. Under steady state operating conditions, the experimental results were obtained on the variations of the pressure and flow rate to and from the energy recovery unit. The hydraulic recovery efficiency （En） of the energy recovery unit with the fluid switcher reached up to 76.83%.展开更多
Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using...Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system. To this end, a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted. Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel. Also, it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack, mostly by cross-linker concentration(48 psi). Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122% for 0.5 weight ratio of cross-linker/polymer. The presence of salts, in particular divalent cations, has a detrimental effect on the hydrogel stability. The maximum strain value applied on hydrogel in the presence of CaCl_2 was only about 201% as compared to 1010% in the presence of distilled water. Finally, thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300 °C. The results of this study revealed the potential application of the hydrogel to control sand production.展开更多
In the case of fault diagnosis for roller bearings, the conventional diagnosis approaches by using the time interval of energy impacts in time-frequency distribution or the pass-frequencies are based on the assumption...In the case of fault diagnosis for roller bearings, the conventional diagnosis approaches by using the time interval of energy impacts in time-frequency distribution or the pass-frequencies are based on the assumption that machinery operates under a constant rotational speed. However, when the rotational speed varies in the broader range, the pass-frequencies vary with the change of rotational speed and bearing faults cannot be identified by the interval of impacts. Researches related to automatic diagnosis for rotational machinery in variable operating conditions were quite few. A novel automatic feature extraction method is proposed based on a pseudo-Wigner-Ville distribution （PWVD） and an extraction of symptom parameter （SP）. An extraction method for instantaneous feature spectrum is presented using the relative crossing information （RCI） and sequential inference approach, by which the feature spectrum from time-frequency distribution can be automatically, sequentially extracted. The SPs are considered in the frequency domain using the extracted feature spectrum to identify among the conditions of a machine. A method to obtain the synthetic symptom parameter is also proposed by the least squares mapping （LSM） technique for increasing the diagnosis sensitivity of SP. Practical examples of diagnosis for bearings are given in order to verify the effectiveness of the proposed method. The verification results show that the features of bearing faults, such as the outer-race, inner-race and roller element defects have been effectively extracted, and the proposed method can be used for condition diagnosis of a machine under the variable rotational speed.展开更多
Detailed investigation of flow behavior in structured packing distillation columns is of great importance in accurate prediction of process efficiency and development of more efficient and optimal equipment internals....Detailed investigation of flow behavior in structured packing distillation columns is of great importance in accurate prediction of process efficiency and development of more efficient and optimal equipment internals. In this study, a three-dimensional two-phase flow model based on VOF method for simulating the hydrodynamics and mass-transfer behavior in a typical representative unit of the structured packing is developed. In the proposed model, the c 2 - ε c model is used for the closure of turbulent mass transfer equation. By solving the proposed model, the velocity distribution, phase fraction profile and concentration field are obtained. Using these data, the total liquid holdup, the wetted area and the separation efficiency [height equivalent to a theoretical plate (HETP)] are estimated. For testing the model validation, the simulated HETPs are compared with our previous experimental data obtained in a 150 mm-diameter column containing Mellapak 350Y operating at the pressures of 0.6-1.8 MPa. The compari-son shows that they are in satisfactory agreement, with an average absolute deviation (AAD) of 25.4%.展开更多
文摘CO_(2) hydrogenation to CH3OH is of great significance for achieving carbon neutrality.Here,we show a urea-assisted grinding strategy for synthesizing Cu-Zn-Ce ternary catalysts(CZC-G)with optimized interfacial synergy,achieving superior performance in CO_(2) hydrogenation to methanol.The CZC-G catalyst demonstrated exceptional methanol selectivity(96.8%)and a space-time yield of 73.6 gMeOH·kgcat^(–1)·h^(–1) under optimized conditions.Long-term stability tests confirmed no obvious deactivation over 100 h of continuous operation.Structural and mechanistic analyses revealed that the urea-assisted grinding method promotes the formation of Cu/Zn-O_(v)-Ce ternary interfaces and inhibits the reduction of ZnO,enabling synergistic interactions for efficient CO_(2) activation and selective stabilization of formate intermediates(HCOO^(*)),which are critical for methanol synthesis.In-situ diffuse reflectance infrared Fourier transform spectra and X-ray absorption spectroscopy studies elucidated the reaction pathway dominated by the formate mechanism,while suppressing the reverse water-gas shift reaction.This work underscores the critical role of synthetic methodologies in engineering interfacial structures,offering a strategy for designing high-performance catalysts for sustainable CO_(2) resource utilization.
文摘Experiments were made for the adsorption of CO2 and N2 on typical adsorbents to investigate the effects of porous structure and surface affinity of adsorbents as well as those of adsorption temperature and pressure that might cause the variation of adsorption mechanism. It is shown that polar surface tends to enlarge the adsorption difference between CO2 and N2, and the difference is more sensitive to temperature than the adsorbents with non-polar surface. The adsorbents with non-polar surface are not much sensitive to the effect of water vapor, though the water vapor interferes the separation remarkably. The separation coefficient linearly increases with the micro- pore volume per unit surface area of activated carbons, but no rule is shown on mesoporous silicon materials. The function of adsorption mechanism on the separation is not as much as expected.
基金supported by the National Natural Science Foundation of China(21978203,21676183).
文摘Process optimization in equation-oriented(EO)modeling environments favors the gradient-based optimization algorithms by their abilities to provide accurate Jacobian matrices via automatic or symbolic differentiation.However,computational inefficiencies including that in initial-point-finding for Newton type methods have significantly limited its application.Recently,progress has been made in using a pseudo-transient(PT)modeling method to address these difficulties,providing a fresh way forward in EO-based optimization.Nevertheless,research in this area remains open,and challenges need to be addressed.Therefore,understanding the state-of-the-art research on the PT method,its principle,and the strategies in composing effective methodologies using the PT modeling method is necessary for further developing EO-based methods for process optimization.For this purpose,the basic concepts for the PT modeling and the optimization framework based on the PT model are reviewed in this paper.Several typical applications,e.g.,complex distillation processes,cryogenic processes,and optimizations under uncertainty,are presented as well.Finally,we identify several main challenges and give prospects for the development of the PT based optimization methods.
文摘This article aims tomodel and analyze the heat and fluid flow characteristics of a carboxymethyl cellulose(CMC)nanofluid within a convergent-divergent shaped microchannel(Two-dimensional).The base fluid,water+CMC(0.5%),is mixed with CuO and Al2O3 nanoparticles at volume fractions of 0.5%and 1.5%,respectively.The research is conducted through the conjugate usage of experimental and theoretical models to represent more realistic properties of the non-Newtonian nanofluid.Three types of microchannels including straight,divergent,and convergent are considered,all having the same length and identical inlet cross-sectional area.Using ANSYS FLUENT software,Navier-Stokes equations are solved for the laminar flow of the non-Newtonian nanofluid.The study examines the effects of Reynolds number,nanoparticle concentration and type,and microchannel geometry on flow and heat transfer.The results prove that the alumina nanoparticles outperform copper oxide in increasing the Nusselt number at a 0.5% volume fraction,while copper oxide nanoparticles excel at a 1.5%volume fraction.Moreover,in the selected case study,as the Reynolds number increases from 100 to 500,the Nusselt number rises by 56.26% in straight geometry,52.93% in divergent geometry,and 59.10%in convergent geometry.Besides,the Nusselt number enhances by 18.75% when transitioning from straight to convergent geometry at a Reynolds number of 500,and by 19.81%at a Reynolds number of 1000.Finally,the results of the research depict that the use of thermophysical properties derived from the experimental achievements,despite creating complexity in the modeling and the solution method,leads to more accurate and realistic outputs.
基金the National Natural Science Foun-dation of China(No.22278334)。
文摘For the efficient harnessing of solar energy and mitigation of environmental pollution,the develop-ment and application of semiconductor photocatalysis technology is paramount.Herein,a novel SubPc-Br/CdS supramolecular array with an S-scheme heterojunction was synthesized through the intermolecu-larπ-stacked self-assembly of subphthalocyanine(SubPc-Br)and nanometer cadmium sulfide(CdS).This self-assembly system features a highly structured architecture and excellent stability.Experiments and ground-state differential charge calculations demonstrate that SubPc-Br and CdS form a built-in electric field during the self-assembly process,a critical factor in promoting the dissociation of electrons and holes.Additionally,this study utilized time-dependent density functional theory(TDDFT)to simulate the dynamic adsorption behavior of excited oxygen molecules on the SubPc-Br/CdS interface for the first time.The analysis of molecular charge differential density under different excited states proved that the addi-tion of SubPc-Br molecules not only improves the photocorrosion resistance of CdS in an O2 adsorption environment but also enhances the production of advanced reactive oxygen species under the synergistic action of h+and·O2-.When subjected to visible light,the degradation efficiency of minocycline(MC)achieved 96.8%within 60 min and maintained 80.3%after 5 cycles.In summary,this study highlights the feasibility of creating advanced S-scheme heterojunction photocatalysts through the strategic incor-poration of organic supramolecules with semiconductor catalysts.
文摘The separation between methane and nitrogen is an inevitable and important task in the C1 chemicaltechnology and the utilization of methane from coalbed, yet it is considered to be one of the tough tasks in thefield of separation. Pressure swing adsorption is a preferable technology if an adsorbent that allowing a largecoefficient of separation for the CH4/N2 system is available. The separation coefficients between CH4 and N2were obtained on analyzing the breakthrough curves measured experimentally with nine adsorbents. A technique ofmeasuring the temperature-pulse was incorporated in the experiments, and the reliability of the result was improved.Superactivated carbon with large surface area and plenty of micropores was shown to have the largest separationcoefficient and to be promising for the commercial utilization.
基金supported by HuPao Dyeing Plant,JiangSu Province,China
文摘The performance of combined Fenton oxidation and membrane bioreactor （MBR） process for the advanced treatment of an effluent from an integrated dyeing wastewater treatment plant was evaluated. The experimental results revealed that under the optimum Fenton oxidation conditions （initial pH 5, H 2 O 2 dosage 17 mmol/L, and Fe^ 2＋ 1.7 mmol/L） the average total organic carbon （TOC） and color removal ratios were 39.3% and 69.5% after 35 min of reaction, respectively. Results from Zahn-Wallens Test also represented that Fenton process was effective to enhance the biodegradability of the test wastewater. As for the further purification of MBR process, TOC removal capacity was examined at different hydraulic retention times （HRT） of 10, 18 and 25 hr. Under the optimum HRT of 18 hr, the average TOC concentration and color of the final MBR effluent were 16.8 mg/L and 2 dilution time, respectively. The sludge yield coefficient was 0.13 g MLSS/g TOC and TOC degradation rate was 0.078 kg TOC/（m ^3 ·day）. The final effluent of MBR can meet the reuse criteria of urban recycling water – water quality standard for miscellaneous water consumption GBT18920-2002.
基金Supported by the National Natural Science Foundation of China （20976130 and 20806057）, National Science and Technology Pillar Program of China （2007BAD42B02）, Program for New Century Excellent Talents in University of Ministry of Education of China （No. NCET-08-0386）, and the R＆D program of Tianjin Binhai New Area （2010-BK17C004）..
文摘The reactions of exo-cellulase （cellobiohydrolase, CBH） and endo-cellulase （endoglucanase, EG） were investigated by analyzing the insoluble residues of microcrystalline cellulose （MCC） and filter paper cellulose （FPC） during enzymatic hydrolysis. Molecular parameters including molecular weight and its distribution, degree of polymerization, and radii of gyration were measured by size exclusion chromatography coupled with multi-angle laser light scattering. No significant change in MCC chains was found during the whole reaction period, indicating that CBH digestion follows a layer-by-layer solubilization manner. This reaction mode might be the major reason for slow enzymatic hydrolysis of cellulose. On the other hand, the degree of polymerization of FPC chains decreases rapidly in the initial reaction, indicating that EG digestion follows a random scission manner, which may create new ends for CBH easily. The slopes of the conformation plots for MCC and FPC increase gradually, indicating stronger chain stiffness of cellulose during hvdrolvsis
基金Supported by the National Key R&D Program of China(No.2017YFB0603400)the National Natural Science Foundation of China(No.21436009)Tianjin Research Program of Basic Research and Frontier Technology(No.15JCQNJC43400)
文摘Membrane separation technology has popularized rapidly and attracts much interest in gas industry as a promising sort of newly chemical separation unit operation. In this paper, recent advances on membrane processes for CO_2 separation are reviewed. The researches indicate that the optimization of operating process designs could improve the separation performance, reduce the energy consumption and decrease the cost of membrane separation systems. With the improvement of membrane materials recently,membrane processes are beginning to be competitive enough for CO_2 separation, especially for postcombustion CO_2 capture, biogas upgrading and natural gas carbon dioxide removal, compared with the traditional separation methods. We summarize the needs and most promising research directions for membrane processes for CO_2 separation in current and future membrane applications. As the time goes by, novel membrane materials developed according to the requirement proposed by process optimization with increased selectivity and/or permeance will accelerate the industrialization of membrane process in the near future. Based on the data collected in a pilot scale test, more effort could be made on the optimization of membrane separation processes. This work would open up a new horizon for CO_2 separation/Capture on Carbon Capture Utilization and Storage(CCUS).
基金Supported by the Independent Innovation Fund of Tianjin University(No.1307)
文摘An economic and effective method of preparing enriched 10B boric acid was established by chemical reactionof enriched 10BF3 and CaCO3. A process of boron trifluoride reacting with water was investigated under certainconditions. Calcium carbonate was selected to counteract hydrofluoric acid followed on. Some key operation factorswere investigated, such as temperature, reaction time and the ratio of CaCO3 to 10BF3. The results showed that the yieldof enriched 10B boric acid could reach 97. 2% and the purity was up to 94. 1% under the following conditions: the temperaturewas 50-60,℃, the reaction time was 28 h and the ratio of CaCO3 to 10BF3 was 4. In addition, after recrystallizationand titration analysis, the purity of the product could reach over 99. 2% from 94.1%.
基金Supported by the National Natural Science Foundation of China （No.20476072）.
文摘To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali-dation of flow simulation. In this work, the velocity profiles of single-phase flow in structured packing are measured at the Reynolds numbers of 20.0, 55.7 and 520.1, using the laser Doppler velocimetry （LDV）. The time-averaged and instantaneous velocities of three components are obtained simultaneously. The CFD simulation is also carried out to numerically predict the velocity distribution within the structured packing. Comparison shows that the flow pattern, velocity distribution and turbulent kinetic energy （for turbulent flow） on the horizontal plane predicted by CFD simulation are in good agreement with the LDV measured data. The values of the x-and z-velocity components are quantitatively well predicted over the plane in the center of the packing, but the predicted y-component is sig-nificantly smaller than the experimental data. It can be concluded that experimental measurement is important for further improvement of CFD model.
文摘Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups whichcan be used as carriers of CO2 were prepared. One was poly(N-vinyl-γ-sodium aminobutyrate)(PVSA), whichwas obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) byradical polymerization. The other was poly(N-vinyl-γ-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), whichwas obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). Thecomposite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as supportmembranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 throughthe composite membranes were measured. The results show that the composite membranes present better CO2permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2pressure, the PVSA/PS composite membrane displays a CO2 permeation rate of 5.95 × 10-7 cm3.cm-2.s-1.pa-1with CO2/CH4 ideal separation factor of 212.1. At 20℃, 6400Pa of CO2 pressure, the VSA-SA/PS compositemembrane displays a CO2 permeation rate of 4.24 × 10-8 cm3@cm-2.s-1.Pa-1 with CO2/CH4 ideal separationfactor of 429.7. The results with the gas mixtures are not as good as those obtained with pure gas because ofthe coupling effects between CO2 and CH4. The heat cross-linked membrane shows good separation factor due todensification of the polymer.
基金Supported by Tianjin Municipal Science Foundation （No. 07JCZDJC 02500）
文摘The problem of optimal synthesis of an integrated water system is addressed in this study, where water using processes and water treatment operations are combined into a single network such that the total cost of fresh water and wastewater treatment is globally minimized. A superstructure that incorporates all feasible design alterna- tives for wastewater treatment, reuse and recycle, is synthesized with a non-linear programming model. An evolutionary approach--an improved particle swarm optimization is proposed for optimizing such systems. Two simple examples are .Presented.to illustrate the global op.timization of inte.grated water networks using the proposed algorithm.
基金Supported by the National Natural Science Foundation of China(21436009)the Program of Introducing Talents of Discipline to Universities(B06006)
文摘Recent advances on mixed matrix membrane for CO<sub>2</sub> separation are reviewed in this paper. To improve CO<sub>2</sub> separation performance of polymer membranes, mixed matrix membranes (MMMs) are developed. The concept of MMM is illustrated distinctly. Suitable polymer and inorganic or organic fillers for MMMs are summarized. Possible interface morphologies between polymer and filler, and the effect of interface morphologies on gas transport properties of MMMs are summarized. The methods to improve compatibility between polymer and filler are introduced. There are eight methods including silane coupling, Grignard treatment, incorporation of additive, grafting, in situ polymerization, polydopamine coating, particle fusion approach and polymer functionalization. To achieve higher productivity for industrial application, mixed matrix composite membranes are developed. The recent development on hollow fiber and flat mixed matrix composite membrane is reviewed in detail. Last, the future trend of MMM is forecasted.
基金the Seawater Desalination Research Programs of Tianjin(043185211-4)
文摘Energy recovery device （ERD） is an important part of the seawater reverse osmosis （SWRO） desalination system. There are principally two kinds of ERDs, the centrifugal type and the positive displacement （PD） type. The PD type is of extensive concern and is preferred in large-scale plants. In this article, an innovative fluid switcher was presented and a two-cylinder hydraulic energy recovery unit with a lab-scale fluid switcher was set up. Tap water was used as the working medium instead of the actual seawater and brine in SWRO desalination plants. Under steady state operating conditions, the experimental results were obtained on the variations of the pressure and flow rate to and from the energy recovery unit. The hydraulic recovery efficiency （En） of the energy recovery unit with the fluid switcher reached up to 76.83%.
基金support of the Iran National Science Foundation(INSF)with Project No.of 95849122
文摘Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system. To this end, a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted. Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel. Also, it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack, mostly by cross-linker concentration(48 psi). Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122% for 0.5 weight ratio of cross-linker/polymer. The presence of salts, in particular divalent cations, has a detrimental effect on the hydrogel stability. The maximum strain value applied on hydrogel in the presence of CaCl_2 was only about 201% as compared to 1010% in the presence of distilled water. Finally, thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300 °C. The results of this study revealed the potential application of the hydrogel to control sand production.
基金supported by National Natural Science Foundation of China (Grant No. 50875016, 51075023)Fundamental Research Funds for the Central Universities of China (Grant No. JD0903, JD0904)
文摘In the case of fault diagnosis for roller bearings, the conventional diagnosis approaches by using the time interval of energy impacts in time-frequency distribution or the pass-frequencies are based on the assumption that machinery operates under a constant rotational speed. However, when the rotational speed varies in the broader range, the pass-frequencies vary with the change of rotational speed and bearing faults cannot be identified by the interval of impacts. Researches related to automatic diagnosis for rotational machinery in variable operating conditions were quite few. A novel automatic feature extraction method is proposed based on a pseudo-Wigner-Ville distribution （PWVD） and an extraction of symptom parameter （SP）. An extraction method for instantaneous feature spectrum is presented using the relative crossing information （RCI） and sequential inference approach, by which the feature spectrum from time-frequency distribution can be automatically, sequentially extracted. The SPs are considered in the frequency domain using the extracted feature spectrum to identify among the conditions of a machine. A method to obtain the synthetic symptom parameter is also proposed by the least squares mapping （LSM） technique for increasing the diagnosis sensitivity of SP. Practical examples of diagnosis for bearings are given in order to verify the effectiveness of the proposed method. The verification results show that the features of bearing faults, such as the outer-race, inner-race and roller element defects have been effectively extracted, and the proposed method can be used for condition diagnosis of a machine under the variable rotational speed.
基金Supported by the National Natural Science Foundation of China (20676091)the Program for New Century Excellent Talentsin University and the Program for Changjiang Scholars and Innovative Research Teams in Universities (IRT0641)
文摘Detailed investigation of flow behavior in structured packing distillation columns is of great importance in accurate prediction of process efficiency and development of more efficient and optimal equipment internals. In this study, a three-dimensional two-phase flow model based on VOF method for simulating the hydrodynamics and mass-transfer behavior in a typical representative unit of the structured packing is developed. In the proposed model, the c 2 - ε c model is used for the closure of turbulent mass transfer equation. By solving the proposed model, the velocity distribution, phase fraction profile and concentration field are obtained. Using these data, the total liquid holdup, the wetted area and the separation efficiency [height equivalent to a theoretical plate (HETP)] are estimated. For testing the model validation, the simulated HETPs are compared with our previous experimental data obtained in a 150 mm-diameter column containing Mellapak 350Y operating at the pressures of 0.6-1.8 MPa. The compari-son shows that they are in satisfactory agreement, with an average absolute deviation (AAD) of 25.4%.
