This study presents a systematic investigation of pressure drop and gas holdup in an upward-flow fixedbed reactor,examining the effects of bubble size,bed height,particle shape,superficial gas velocity(SGV),and superf...This study presents a systematic investigation of pressure drop and gas holdup in an upward-flow fixedbed reactor,examining the effects of bubble size,bed height,particle shape,superficial gas velocity(SGV),and superficial liquid velocity(SLV)based on experimental measurements and empirical correlations.Two bubble generators,namely ring tube generator(RTG)and porous sintered film generator(PSG),are used.Key findings reveal that for the PSG,increasing SGV decreases small-bubble population while promoting large-bubble formation,with the bubbles stabilizing at a Sauter mean diameter(d_(32))of~3 mm.The RTG produces stable large bubbles(d_(32)=6—7 mm)with minimal size variations across the range of tested SGVs.The pressure drop decreases with an increase in SGV but increases with higher SLV and bed height,primarily due to the reduced liquid holdup and the dominance of static pressure.Smaller bubbles reduce the pressure drop by slowing rise velocity and minimizing frictional resistance.Clover-shaped particles exhibit the highest pressure drop owing to large porosity,while 3-mm toothed spheres show higher pressure drop than 5-mm spheres at high SGV because of intensified capillary forces.The gas holdup increases with increasing SGV and bed height but decreases slightly with increasing SLV.Smaller bubbles enhance gas holdup by improving bed distribution and residence time.The 3-mm toothed spheres show the highest gas holdup due to stronger capillary trapping,whereas the clover-shaped particles exhibit the lowest.Empirical correlations for pressure drop and gas holdup are developed,yielding calculation errors within±1%and±20%of the experimental values,respectively.展开更多
Biodiesel industrial production based on a solid base catalyst in a fixed-bed was simulated. The lab and bench scale experiments were carded out effectively, in which the kinetic model is established and it can descri...Biodiesel industrial production based on a solid base catalyst in a fixed-bed was simulated. The lab and bench scale experiments were carded out effectively, in which the kinetic model is established and it can describe the transesterification reaction well. The Antoine equation of biodiesel is regressed with the vapor-liquid data cited of literature. The non-random two liquid （NRTL） model is applied to describe the system of fatty acid methyl ester （FAME）, methanol and glycerol and parameters are obtained. The Ternary phase map is obtained from Aspen Plus via the liquid-liquid equilibrium （LLE） data. In order to describe the production in a fixed-bed performs in industrial scale after being magnified 1 000 times, the Aspen Plus simulation is employed, where two flowsheets are simulated to predict material and energy consumption. The simulation results prove that at least 350. 42 kW energy consumption can be reduced per hour to produce per ton biodiesel compared with data reported in previous references.展开更多
Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption...Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.展开更多
An industrial scale propylene production via oxidative dehydrogenation of propane （ODHP） in multi-tubular re- actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diame...An industrial scale propylene production via oxidative dehydrogenation of propane （ODHP） in multi-tubular re- actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefln over V2O5/γ-Al203 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other pa- rameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100% conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72 m for the first and 7.32 m for the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor run- away temperature problem and enabled operations at the wider range of conditions to obtain enhanced propyl- ene production in an industrial scale reactor.展开更多
One-dimensional heterogeneous plug flow model was employed to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether.Longitudinal temperature and conversion profiles predicted...One-dimensional heterogeneous plug flow model was employed to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether.Longitudinal temperature and conversion profiles predicted by this model were compared to those experimentally measured in a bench scale reactor.The reactor was packed with 1.5mm γ-Al2O3 pellets as dehydration catalyst and operated in a temperature range of 543-603K at an atmospheric pressure.Also,the effects of weight hourly space velocity(WHSV)and temperature on methanol conversion were investigated.According to the results,the maximum conversion is obtained at 603.15K with WHSV of 72.87h-1.展开更多
This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown co...This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown coal at800 °C. The chars prepared from the gasification experiments were then collected and subjected to reactivity characterisation(ex-situ reactivity) using TGA(thermogravimetric analyser) in air. The results indicate that the char reactivity from TGA was generally high when the char experienced intensive gasification reactions in 0.3%O2in the fixed-bed reactor. The addition of steam into the gasification not only enhanced the char conversion significantly but also reduced the char reactivity dramatically. The curve shapes of the char reactivity with involvement of steam were very different from that with O2 gasification, implying the importance of gasifying agents to char properties.展开更多
The study of scale up for the oxidative coupling of methane （OCM） has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 （W-Mn/SiO2） catalyst. The effects of reaction ...The study of scale up for the oxidative coupling of methane （OCM） has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 （W-Mn/SiO2） catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COx; with the CH4/O2 molar ratio of 5, the highest C2 （ethylene and ethane） yield of 25% was achieved; the presence of steam （as diluent） had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity （GHSV）, higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%-61% and C2 yield of 24.2%-25.4% were achieved by a single pass without any significant loss in catalytic performance.展开更多
Recently, Fischer-Tropsch synthesis （FTS） has become an interesting technology because of its potential role in producing biofuels via Biomass- to-Liquids （BTL） processes. In Fischer-Tropsch （FT） section, biomas...Recently, Fischer-Tropsch synthesis （FTS） has become an interesting technology because of its potential role in producing biofuels via Biomass- to-Liquids （BTL） processes. In Fischer-Tropsch （FT） section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide （CO） and hydrogen （H2）, is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H2/CO in 2 ： 1 molar ratio that was fed at the rate of 30 mL（STP）·min^- 1 （GHSV ≈ 136 mL·gcat^-1 ·h^-1） into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 ℃ and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions （in terms of time on stream） were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products （α） for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.展开更多
Exfoliated 2D MAX Ti_(3) AlC_(2) conductive cocatalyst anchored with g-C_(3)N_(4)/TiO_(2) to construct 2D/0D/2D het-erojunction has been explored for enhanced CO_(2) photoreduction in a fixed-bed and monolith photorea...Exfoliated 2D MAX Ti_(3) AlC_(2) conductive cocatalyst anchored with g-C_(3)N_(4)/TiO_(2) to construct 2D/0D/2D het-erojunction has been explored for enhanced CO_(2) photoreduction in a fixed-bed and monolith photoreac-tor.The TiO_(2) particle sizes(NPs and MPs)were systematically investigated to determine effective metal-support interaction with faster charge carrier separation among the composite materials.When TiO_(2) NPs were anchored with 2D Ti_(3) AlC_(2) MAX structure,10.44 folds higher CH_(4) production was observed com-pared to anchoring TiO_(2) MPs.Maximum CH_(4) yield rate of 2103.5μmol g^(−1) h^(−1) achieved at selectivity 96.59%using ternary g-C_(3)N_(4)/TiO_(2)/Ti_(3) AlC_(2)2D/0D/2D composite which is 2.73 and 7.45 folds higher than using binary g-C_(3)N_(4)/Ti_(3) AlC_(2) MAX and TiO_(2) NPs/Ti_(3)AlC_(2) samples,respectively.A step-scheme(S-scheme)photocatalytic mechanism operates in this composite,suppressed the recombination of useful electron and holes and provides higher reduction potential for efficient CO_(2) conversion to CO and CH_(4).More im-portantly,when light intensity was increased by 5 folds,CH_(4) production rate was increased by 3.59 folds under visible light.The performance of composite catalyst was further investigated in a fixed-bed and monolith photoreactor and found monolithic support increased CO production by 2.64 folds,whereas,53.99 times lower CH_(4) production was noticed.The lower photocatalytic activity in a monolith photore-actor was due to lower visible light penetration into the microchannels.Thus,2D MAX Ti_(3) AlC_(2) composite catalyst can be constructed for selective photocatalytic CO_(2) methanation under visible light in a fixed-bed photoreactor.展开更多
An on-line prediction scheme combining the Karhunen-Love expansion and a recurrent neural network for a wall-cooled fixed-bed reactor is presented.Benzene oxidation in a pilotscale,single tube fixed-bed reactor is cho...An on-line prediction scheme combining the Karhunen-Love expansion and a recurrent neural network for a wall-cooled fixed-bed reactor is presented.Benzene oxidation in a pilotscale,single tube fixed-bed reactor is chosen as a working system and a pseudo-homogeneous twodimensional model is used to generate simulation data to investigate the prediction scheme presentedunder randomly changing operating conditions.The scheme consisting of the K-L expansion andneural network performs satisfactorily for on-line prediction of reaction yield and bed temperatures.展开更多
Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room tempera...Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr（VI） with formic acid as the reducing agent. It also demonstrated an efficient Cr（VI） removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr（VI）-containing water. Thus, it has a good potential for the catalytic reduction of Cr（VI） in the water treatment practice.展开更多
In this work a one-dimensional mathematical model was developed to simulate methane conversion and hydrogen yield in a fixed-bed reactor filled with catalyst particles. For the reason that reforming reactions are sore...In this work a one-dimensional mathematical model was developed to simulate methane conversion and hydrogen yield in a fixed-bed reactor filled with catalyst particles. For the reason that reforming reactions are sorely endothermic process, the heat is supplied to the reactor through electrical heating. The reforming reactions have been investigated from a modelling view point considering the effect of different temperatures ranging from 500℃ and 977℃ on the conversion of methane and hydrogen yield. Simulation results show that the steam reforming of methane in a fixed-bed reactor can efficiently store high temperature end thermal energy. When the operating temperature is increased to 977℃, the conversion of methane is 97.48% and the hydrogen yield is 2.2408. As a conclusion, the maximum thermochemical efficiency will be obtained under optimal operating temperature (977℃) and the steam/methane (3.86) ratio.展开更多
This work investigated the applicability of heterogeneous and pseudo-homogeneous models to predict the dynamic behavior of a fixed-bed catalytic reactor. Some issues concerning the dynamic behavior of the system were ...This work investigated the applicability of heterogeneous and pseudo-homogeneous models to predict the dynamic behavior of a fixed-bed catalytic reactor. Some issues concerning the dynamic behavior of the system were discussed, such as the prediction of the inverse response phenomenon. The proposed models (Het- erogeneous I and II and Pseudo-homogeneous) were able to predict with qualitative similarity the main characteristics of the dynamic behavior of a fixed-bed catalytic reactor, including the inverse response. The computational time demanded for the solution of the heterogeneous models was 10 to 50% longer than in the case of the pseudo-homogeneous model, making the use of the former suitable for applications where computational time is not the major restriction (off-line applications). On the other hand, when on-line applications are required, the simplified model (Pseudo-homogeneous model) showed to be a good alternative because this model was able to predict (qualitatively) the dynamics of the reactor using a faster and easier numerical solution.展开更多
The radiological characterization is to determine the type, the distribution and the radioactivity of the radionuclide in the reactor by investigation of the information, instrumentation detection, sampling analyses a...The radiological characterization is to determine the type, the distribution and the radioactivity of the radionuclide in the reactor by investigation of the information, instrumentation detection, sampling analyses and theoretical calculation. It is used for determination of the decommissioning implementation option and radiological protection measure of the workers. After completion of the decommissioning it is used for determination of the site release. The radiological characterization should go through whole decommissioning process, which includes： the collection and review of historical file, the performing calculation of radionuclide inventory in the reactor, in situ measurement, sampling analyses, the review and evaluation of the data obtained and the comparison of calculated result with measured date etc.. The special attention should be paid to the radiological characterization information from the key part of reactor in decommissioning end state. The sampling from the ＂hot spot＂ should not be lost; the number of the sampling should be reasonable based on reliable statistics. The radioactivity density for site release should comply with the guide, standard and regulation of International Atomic Energy Agency and China.展开更多
The manufacture,physical characterization,environmental applications and cytotoxicity properties of nanocomposites consisting of CuO/CeO2 nano-rare earth composite materials prepared using the coprecipitation method a...The manufacture,physical characterization,environmental applications and cytotoxicity properties of nanocomposites consisting of CuO/CeO2 nano-rare earth composite materials prepared using the coprecipitation method at molar ratio of 6:4 with aqueous solutions of copper nitrate and cerium nitrate were reported.The performance of the selective catalytic oxidation of ammonia to N2(NH3-SCO) over a CuO/CeO2 nano-rare earth composite materials in a tubular fixed-bed reactor(TFBR) at temperatures from 423 to 673 K in the presence of oxygen was elucidated.The catalytic redox behavior was determined by cyclic voltammetry(CV).The nanocomposite particles were characterized by TEM,with a tiny particle size around 10 nm with high dispersion phenomena.Further,cell cytotoxicity and the percentage cell survival were determined by using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetra-zolium(MTS) assay on human lung MRC-5 cell line.Experimental results showed that no apparent cytotoxicity was observed when the MRC-5 was exposed to the CuO/CeO2 nanocomposite materials.展开更多
In response to the accelerating demands of industrial development,the scale-up of stirred reactors has become increasingly prevalent.Multi-shaft stirred reactors have emerged as a promising solution;however,a critical...In response to the accelerating demands of industrial development,the scale-up of stirred reactors has become increasingly prevalent.Multi-shaft stirred reactors have emerged as a promising solution;however,a critical challenge remains in achieving efficient mixing while simultaneously minimizing energy consumption.Here,a novel approach based on differential rotation speeds to optimize mixing performance was proposed.Results demonstrate that a carefully configured rotation speed difference significantly enhances mixing efficiency,reducing mixing time by 17.89% and power consumption by 12.07%.This strategy not only amplifies flow field instability but also minimizes instability discrepancies,promoting a more uniform distribution of vortices across various scales.Furthermore,under this approach,the bottom impeller has the strongest impact on mixing,while the middle and lower impellers synergistically strengthen the weaker mixing regions and facilitate the redistribution of energy in the flow field.This method promotes efficient energy transfer from large-scale to small-scale vortices,ultimately improving overall mixing performance.This work offers a promising avenue for the optimal design and operation of multi-shaft stirred reactors,advancing both efficiency and energy sustainability.展开更多
中子探针具有磁矩和深穿透能力,且对轻元素灵敏、能够鉴别同位素及近邻元素,已成为材料科学领域创新研究的重要手段。作为国家三大中子源之一,中国工程物理研究院的中国绵阳研究堆(China Mianyang Research Reactor,CMRR)于2013年率先...中子探针具有磁矩和深穿透能力,且对轻元素灵敏、能够鉴别同位素及近邻元素,已成为材料科学领域创新研究的重要手段。作为国家三大中子源之一,中国工程物理研究院的中国绵阳研究堆(China Mianyang Research Reactor,CMRR)于2013年率先建成首期8套科学装置并于当年投入使用,稳定运行至今已有十余年。本文重点介绍了CMRR中子平台近几年的装置技术和应用研究进展。目前平台拥有15套科学装置,相比于首期装置数量已几近翻番。基于新研建的装置,将材料静态结构最大可测尺度由原有的数百纳米拓宽至数十微米,突破实现了微观动力学能量分辨能力约3个量级的提升(由原来的亚毫电子伏特提升至百纳电子伏特)。基于平台跨尺度多参量的综合型大科学装置集群优势,CMRR已应用于金属合金、磁性材料、电池材料、含能材料、软物质等关键工程材料研究和工程部件制造等领域。在未来,依托中子科学与技术全国重点实验室,着力推动以中子科学为基础的重大原始创新和新材料、凝聚态物理等多学科前沿发展,为工程材料及部件研发面临的瓶颈科学技术问题提供新认识和创新解决方案。展开更多
In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether （DME） from syngas including CO2 i...In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether （DME） from syngas including CO2 in a fixed bed reactor at commercial scale under both adiabatic and isothermal conditions. For this purpose, a computational fluid dynamic （CFD） simulation was carried out through which the standard κ-ε model with 10% turbulence tolerations was implemented. At first, an adiabatic fixed bed reactor was simulated and the obtained results were compared with those of an equivalent commercial slurry reactor. Then the concentration and temperature profiles along the reactor were predicted. Consequently, the optimum temperature, pressure, hydrogen to carbon monoxide ratio in the feedstock and the reactor height under different operation conditions were determined. Finally, the results obtained from this three-dimensional dynamic model under appropriate industrial boundary conditions were compared with those of others available in literature to verify the model. Next, through changing the boundary conditions, the simulation was performed for an isothermal fixed bed reactor. Furthermore, it was revealed that, under isothermal conditions, the performed equilibrium simulations were done for a single phase system. Considering the simultaneous effects of temperature and pressure, the optimum operation conditions for the isothermal and adiabatic fixed bed reactors were investigated. The results of the H2＋CO conversions indicated that, under isothermal condition, higher conversion could be achieved, in compared with that under adiabatic conditions. Then, the effects of various operating parameters, including the pressure and temperature, of the reactor on the DME production were examined. Ultimately, the CFD modeling results generated in the present work showed reasonable agreement with previously obtained data available in the literature.展开更多
Owing to the importance of process intensification in the natural gas associated processes, the present contribution aims to investigate the production of an important natural gas downstream product in an improved sys...Owing to the importance of process intensification in the natural gas associated processes, the present contribution aims to investigate the production of an important natural gas downstream product in an improved system.Accordingly, a membrane-assisted reactor for the oxidative dehydrogenation of ethane is presented. The presented system includes a membrane for axial oxygen dosing into the reaction side. Such a strategy would lead to optimum oxygen distribution along the reactor length and prevention of hot spot formation as well. A feasibility study is conducted by developing a validated mathematical model composed of mass and energy balance equations. The effects of various operating variables are investigated by a rigorous sensitivity analysis.Then, by applying the genetic algorithm, a multi-objective optimization procedure is implemented to obtain the optimum operating condition. Considerable increase in the ethane conversion and ethylene yield are the advancements of membrane-assisted oxidative dehydrogenation reactor working under the optimum condition.More than 30% increase in the ethane conversion is obtained. Furthermore, the ethylene yield is enhanced up to 0.45.展开更多
Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examin...Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examined in a fixed-bed reactor. The former group presented higher activity in the OCM, but the main product was carbon dioxide. While the later group showed lower activity but much higher selectivity to C2 hydrocarbons compared with the former. Electrochemical measurements were conducted in a solid oxide membrane reactor with La0.8 Na0.2CoO3 as catalyst. The results showed that methane was oxidized to carbon dioxide and ethane by two parallel reactions. Ethane was oxidized to ethene and carbon dioxide. A fraction of ethene was oxidized deeply to carbon dioxide. The total selectivity to C2 hydrocarbons exceeded 70%. Based on the experimental results, a kinetic model was suggested to describe the reaction results.展开更多
基金financially supported by the National Natural Science Foundation of China(52025103)。
文摘This study presents a systematic investigation of pressure drop and gas holdup in an upward-flow fixedbed reactor,examining the effects of bubble size,bed height,particle shape,superficial gas velocity(SGV),and superficial liquid velocity(SLV)based on experimental measurements and empirical correlations.Two bubble generators,namely ring tube generator(RTG)and porous sintered film generator(PSG),are used.Key findings reveal that for the PSG,increasing SGV decreases small-bubble population while promoting large-bubble formation,with the bubbles stabilizing at a Sauter mean diameter(d_(32))of~3 mm.The RTG produces stable large bubbles(d_(32)=6—7 mm)with minimal size variations across the range of tested SGVs.The pressure drop decreases with an increase in SGV but increases with higher SLV and bed height,primarily due to the reduced liquid holdup and the dominance of static pressure.Smaller bubbles reduce the pressure drop by slowing rise velocity and minimizing frictional resistance.Clover-shaped particles exhibit the highest pressure drop owing to large porosity,while 3-mm toothed spheres show higher pressure drop than 5-mm spheres at high SGV because of intensified capillary forces.The gas holdup increases with increasing SGV and bed height but decreases slightly with increasing SLV.Smaller bubbles enhance gas holdup by improving bed distribution and residence time.The 3-mm toothed spheres show the highest gas holdup due to stronger capillary trapping,whereas the clover-shaped particles exhibit the lowest.Empirical correlations for pressure drop and gas holdup are developed,yielding calculation errors within±1%and±20%of the experimental values,respectively.
基金The National Basic Research Program of China(973Program)(No.2010CB732206)the National Natural Science Foundation of China(No.21076044,21276050)
文摘Biodiesel industrial production based on a solid base catalyst in a fixed-bed was simulated. The lab and bench scale experiments were carded out effectively, in which the kinetic model is established and it can describe the transesterification reaction well. The Antoine equation of biodiesel is regressed with the vapor-liquid data cited of literature. The non-random two liquid （NRTL） model is applied to describe the system of fatty acid methyl ester （FAME）, methanol and glycerol and parameters are obtained. The Ternary phase map is obtained from Aspen Plus via the liquid-liquid equilibrium （LLE） data. In order to describe the production in a fixed-bed performs in industrial scale after being magnified 1 000 times, the Aspen Plus simulation is employed, where two flowsheets are simulated to predict material and energy consumption. The simulation results prove that at least 350. 42 kW energy consumption can be reduced per hour to produce per ton biodiesel compared with data reported in previous references.
基金Supported by the National Natural Science Foundation of China （21006053）, the Fundamental Research Funds for the Central Universities （65010551） and Special Projects of Environmental Protection （2009ZX07208）.
文摘Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.
文摘An industrial scale propylene production via oxidative dehydrogenation of propane （ODHP） in multi-tubular re- actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefln over V2O5/γ-Al203 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other pa- rameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100% conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72 m for the first and 7.32 m for the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor run- away temperature problem and enabled operations at the wider range of conditions to obtain enhanced propyl- ene production in an industrial scale reactor.
文摘One-dimensional heterogeneous plug flow model was employed to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether.Longitudinal temperature and conversion profiles predicted by this model were compared to those experimentally measured in a bench scale reactor.The reactor was packed with 1.5mm γ-Al2O3 pellets as dehydration catalyst and operated in a temperature range of 543-603K at an atmospheric pressure.Also,the effects of weight hourly space velocity(WHSV)and temperature on methanol conversion were investigated.According to the results,the maximum conversion is obtained at 603.15K with WHSV of 72.87h-1.
基金Support by the Victorian State Government under its Energy Technology Innovation Strategy programme and the 12th Five-Year Plan of National Science and Technology of China(2012BAA04B02)
文摘This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown coal at800 °C. The chars prepared from the gasification experiments were then collected and subjected to reactivity characterisation(ex-situ reactivity) using TGA(thermogravimetric analyser) in air. The results indicate that the char reactivity from TGA was generally high when the char experienced intensive gasification reactions in 0.3%O2in the fixed-bed reactor. The addition of steam into the gasification not only enhanced the char conversion significantly but also reduced the char reactivity dramatically. The curve shapes of the char reactivity with involvement of steam were very different from that with O2 gasification, implying the importance of gasifying agents to char properties.
文摘The study of scale up for the oxidative coupling of methane （OCM） has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 （W-Mn/SiO2） catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COx; with the CH4/O2 molar ratio of 5, the highest C2 （ethylene and ethane） yield of 25% was achieved; the presence of steam （as diluent） had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity （GHSV）, higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%-61% and C2 yield of 24.2%-25.4% were achieved by a single pass without any significant loss in catalytic performance.
基金supported by the project of the National Science and Technology Development Agency (NSTDA),Thailand
文摘Recently, Fischer-Tropsch synthesis （FTS） has become an interesting technology because of its potential role in producing biofuels via Biomass- to-Liquids （BTL） processes. In Fischer-Tropsch （FT） section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide （CO） and hydrogen （H2）, is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H2/CO in 2 ： 1 molar ratio that was fed at the rate of 30 mL（STP）·min^- 1 （GHSV ≈ 136 mL·gcat^-1 ·h^-1） into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 ℃ and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions （in terms of time on stream） were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products （α） for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.
基金Ministry of Higher Education (MOHE),Malaysia,for financial support of this work under Fundamental Research Grant Scheme (No.R.J130000.7851.5F384)。
文摘Exfoliated 2D MAX Ti_(3) AlC_(2) conductive cocatalyst anchored with g-C_(3)N_(4)/TiO_(2) to construct 2D/0D/2D het-erojunction has been explored for enhanced CO_(2) photoreduction in a fixed-bed and monolith photoreac-tor.The TiO_(2) particle sizes(NPs and MPs)were systematically investigated to determine effective metal-support interaction with faster charge carrier separation among the composite materials.When TiO_(2) NPs were anchored with 2D Ti_(3) AlC_(2) MAX structure,10.44 folds higher CH_(4) production was observed com-pared to anchoring TiO_(2) MPs.Maximum CH_(4) yield rate of 2103.5μmol g^(−1) h^(−1) achieved at selectivity 96.59%using ternary g-C_(3)N_(4)/TiO_(2)/Ti_(3) AlC_(2)2D/0D/2D composite which is 2.73 and 7.45 folds higher than using binary g-C_(3)N_(4)/Ti_(3) AlC_(2) MAX and TiO_(2) NPs/Ti_(3)AlC_(2) samples,respectively.A step-scheme(S-scheme)photocatalytic mechanism operates in this composite,suppressed the recombination of useful electron and holes and provides higher reduction potential for efficient CO_(2) conversion to CO and CH_(4).More im-portantly,when light intensity was increased by 5 folds,CH_(4) production rate was increased by 3.59 folds under visible light.The performance of composite catalyst was further investigated in a fixed-bed and monolith photoreactor and found monolithic support increased CO production by 2.64 folds,whereas,53.99 times lower CH_(4) production was noticed.The lower photocatalytic activity in a monolith photore-actor was due to lower visible light penetration into the microchannels.Thus,2D MAX Ti_(3) AlC_(2) composite catalyst can be constructed for selective photocatalytic CO_(2) methanation under visible light in a fixed-bed photoreactor.
基金Supported by the National Natural Science Foundation of China(No.29676014)and others.
文摘An on-line prediction scheme combining the Karhunen-Love expansion and a recurrent neural network for a wall-cooled fixed-bed reactor is presented.Benzene oxidation in a pilotscale,single tube fixed-bed reactor is chosen as a working system and a pseudo-homogeneous twodimensional model is used to generate simulation data to investigate the prediction scheme presentedunder randomly changing operating conditions.The scheme consisting of the K-L expansion andneural network performs satisfactorily for on-line prediction of reaction yield and bed temperatures.
基金supported by the Basic Science Innovation Program of Shenyang National Laboratory for Materials Science(Grant Nos.Y4N56R1161 and Y4N56F2161)the National Natural Science Foundation of China(Grant No.51502305)
文摘Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr（VI） with formic acid as the reducing agent. It also demonstrated an efficient Cr（VI） removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr（VI）-containing water. Thus, it has a good potential for the catalytic reduction of Cr（VI） in the water treatment practice.
文摘In this work a one-dimensional mathematical model was developed to simulate methane conversion and hydrogen yield in a fixed-bed reactor filled with catalyst particles. For the reason that reforming reactions are sorely endothermic process, the heat is supplied to the reactor through electrical heating. The reforming reactions have been investigated from a modelling view point considering the effect of different temperatures ranging from 500℃ and 977℃ on the conversion of methane and hydrogen yield. Simulation results show that the steam reforming of methane in a fixed-bed reactor can efficiently store high temperature end thermal energy. When the operating temperature is increased to 977℃, the conversion of methane is 97.48% and the hydrogen yield is 2.2408. As a conclusion, the maximum thermochemical efficiency will be obtained under optimal operating temperature (977℃) and the steam/methane (3.86) ratio.
文摘This work investigated the applicability of heterogeneous and pseudo-homogeneous models to predict the dynamic behavior of a fixed-bed catalytic reactor. Some issues concerning the dynamic behavior of the system were discussed, such as the prediction of the inverse response phenomenon. The proposed models (Het- erogeneous I and II and Pseudo-homogeneous) were able to predict with qualitative similarity the main characteristics of the dynamic behavior of a fixed-bed catalytic reactor, including the inverse response. The computational time demanded for the solution of the heterogeneous models was 10 to 50% longer than in the case of the pseudo-homogeneous model, making the use of the former suitable for applications where computational time is not the major restriction (off-line applications). On the other hand, when on-line applications are required, the simplified model (Pseudo-homogeneous model) showed to be a good alternative because this model was able to predict (qualitatively) the dynamics of the reactor using a faster and easier numerical solution.
文摘The radiological characterization is to determine the type, the distribution and the radioactivity of the radionuclide in the reactor by investigation of the information, instrumentation detection, sampling analyses and theoretical calculation. It is used for determination of the decommissioning implementation option and radiological protection measure of the workers. After completion of the decommissioning it is used for determination of the site release. The radiological characterization should go through whole decommissioning process, which includes： the collection and review of historical file, the performing calculation of radionuclide inventory in the reactor, in situ measurement, sampling analyses, the review and evaluation of the data obtained and the comparison of calculated result with measured date etc.. The special attention should be paid to the radiological characterization information from the key part of reactor in decommissioning end state. The sampling from the ＂hot spot＂ should not be lost; the number of the sampling should be reasonable based on reliable statistics. The radioactivity density for site release should comply with the guide, standard and regulation of International Atomic Energy Agency and China.
基金Project partially supported by the National Science Council of the Republic of China Taiwan (NSC 98-2221-E-132-003-MY3)
文摘The manufacture,physical characterization,environmental applications and cytotoxicity properties of nanocomposites consisting of CuO/CeO2 nano-rare earth composite materials prepared using the coprecipitation method at molar ratio of 6:4 with aqueous solutions of copper nitrate and cerium nitrate were reported.The performance of the selective catalytic oxidation of ammonia to N2(NH3-SCO) over a CuO/CeO2 nano-rare earth composite materials in a tubular fixed-bed reactor(TFBR) at temperatures from 423 to 673 K in the presence of oxygen was elucidated.The catalytic redox behavior was determined by cyclic voltammetry(CV).The nanocomposite particles were characterized by TEM,with a tiny particle size around 10 nm with high dispersion phenomena.Further,cell cytotoxicity and the percentage cell survival were determined by using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetra-zolium(MTS) assay on human lung MRC-5 cell line.Experimental results showed that no apparent cytotoxicity was observed when the MRC-5 was exposed to the CuO/CeO2 nanocomposite materials.
基金supported by the National Natural Science Foundation of China (22078030,52021004)National Key Research and Development Project (2019YFC1905802)+4 种基金Key Project of Independent Research Project of State Key Laboratory of Coal Mine Disaster Dynamics and Control (2011DA105287-zd201902)Chongqing Natural Science Foundation Innovation and Development Joint Fund Project (CSTB2022NSCQ-LZX0014)Hubei Three Gorges Laboratory Open/Innovation Fund (SK211009,SK215001)Fundamental Research Funds for Central Universities(2022CDJQY-005)this work also received funding from the China Scholarship Council。
文摘In response to the accelerating demands of industrial development,the scale-up of stirred reactors has become increasingly prevalent.Multi-shaft stirred reactors have emerged as a promising solution;however,a critical challenge remains in achieving efficient mixing while simultaneously minimizing energy consumption.Here,a novel approach based on differential rotation speeds to optimize mixing performance was proposed.Results demonstrate that a carefully configured rotation speed difference significantly enhances mixing efficiency,reducing mixing time by 17.89% and power consumption by 12.07%.This strategy not only amplifies flow field instability but also minimizes instability discrepancies,promoting a more uniform distribution of vortices across various scales.Furthermore,under this approach,the bottom impeller has the strongest impact on mixing,while the middle and lower impellers synergistically strengthen the weaker mixing regions and facilitate the redistribution of energy in the flow field.This method promotes efficient energy transfer from large-scale to small-scale vortices,ultimately improving overall mixing performance.This work offers a promising avenue for the optimal design and operation of multi-shaft stirred reactors,advancing both efficiency and energy sustainability.
文摘中子探针具有磁矩和深穿透能力,且对轻元素灵敏、能够鉴别同位素及近邻元素,已成为材料科学领域创新研究的重要手段。作为国家三大中子源之一,中国工程物理研究院的中国绵阳研究堆(China Mianyang Research Reactor,CMRR)于2013年率先建成首期8套科学装置并于当年投入使用,稳定运行至今已有十余年。本文重点介绍了CMRR中子平台近几年的装置技术和应用研究进展。目前平台拥有15套科学装置,相比于首期装置数量已几近翻番。基于新研建的装置,将材料静态结构最大可测尺度由原有的数百纳米拓宽至数十微米,突破实现了微观动力学能量分辨能力约3个量级的提升(由原来的亚毫电子伏特提升至百纳电子伏特)。基于平台跨尺度多参量的综合型大科学装置集群优势,CMRR已应用于金属合金、磁性材料、电池材料、含能材料、软物质等关键工程材料研究和工程部件制造等领域。在未来,依托中子科学与技术全国重点实验室,着力推动以中子科学为基础的重大原始创新和新材料、凝聚态物理等多学科前沿发展,为工程材料及部件研发面临的瓶颈科学技术问题提供新认识和创新解决方案。
文摘In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether （DME） from syngas including CO2 in a fixed bed reactor at commercial scale under both adiabatic and isothermal conditions. For this purpose, a computational fluid dynamic （CFD） simulation was carried out through which the standard κ-ε model with 10% turbulence tolerations was implemented. At first, an adiabatic fixed bed reactor was simulated and the obtained results were compared with those of an equivalent commercial slurry reactor. Then the concentration and temperature profiles along the reactor were predicted. Consequently, the optimum temperature, pressure, hydrogen to carbon monoxide ratio in the feedstock and the reactor height under different operation conditions were determined. Finally, the results obtained from this three-dimensional dynamic model under appropriate industrial boundary conditions were compared with those of others available in literature to verify the model. Next, through changing the boundary conditions, the simulation was performed for an isothermal fixed bed reactor. Furthermore, it was revealed that, under isothermal conditions, the performed equilibrium simulations were done for a single phase system. Considering the simultaneous effects of temperature and pressure, the optimum operation conditions for the isothermal and adiabatic fixed bed reactors were investigated. The results of the H2＋CO conversions indicated that, under isothermal condition, higher conversion could be achieved, in compared with that under adiabatic conditions. Then, the effects of various operating parameters, including the pressure and temperature, of the reactor on the DME production were examined. Ultimately, the CFD modeling results generated in the present work showed reasonable agreement with previously obtained data available in the literature.
文摘Owing to the importance of process intensification in the natural gas associated processes, the present contribution aims to investigate the production of an important natural gas downstream product in an improved system.Accordingly, a membrane-assisted reactor for the oxidative dehydrogenation of ethane is presented. The presented system includes a membrane for axial oxygen dosing into the reaction side. Such a strategy would lead to optimum oxygen distribution along the reactor length and prevention of hot spot formation as well. A feasibility study is conducted by developing a validated mathematical model composed of mass and energy balance equations. The effects of various operating variables are investigated by a rigorous sensitivity analysis.Then, by applying the genetic algorithm, a multi-objective optimization procedure is implemented to obtain the optimum operating condition. Considerable increase in the ethane conversion and ethylene yield are the advancements of membrane-assisted oxidative dehydrogenation reactor working under the optimum condition.More than 30% increase in the ethane conversion is obtained. Furthermore, the ethylene yield is enhanced up to 0.45.
基金This work was supported supported by the Center Petrochemical Company of China (X599027).
文摘Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examined in a fixed-bed reactor. The former group presented higher activity in the OCM, but the main product was carbon dioxide. While the later group showed lower activity but much higher selectivity to C2 hydrocarbons compared with the former. Electrochemical measurements were conducted in a solid oxide membrane reactor with La0.8 Na0.2CoO3 as catalyst. The results showed that methane was oxidized to carbon dioxide and ethane by two parallel reactions. Ethane was oxidized to ethene and carbon dioxide. A fraction of ethene was oxidized deeply to carbon dioxide. The total selectivity to C2 hydrocarbons exceeded 70%. Based on the experimental results, a kinetic model was suggested to describe the reaction results.
