查看更多>>摘要：Bubble columns are widely used as contacting devices and multiphase reactors in process and chemical industries.Their"baseline"layout involves a vessel wherein the gas phase is injected into a stagnant liquid phase in the form of"dispersed bubbles"or"coalescence-induced structures".This"baseline"layout can be modified by including internal heat exchangers(to control the heat transfer and reaction rates)and a solid-phase(a catalyst),and by applying co-current/counter-current liquid circulation(to increase the mass transfer rate).Even in the"baseline"layout,the coupling between the phases gives rise to rich,fascinating and mysterious fluid dynamics phenomena.Indeed,it is recognized that the"global-scale"is imposed by the"local-scale"and that the coupling between the two scales emerges in the flow patterns(flow regimes).The"bubble-scale"(i.e.,the bubble motion and turbulent eddies that control heat and mass transfer),influences the medium-scale(i.e.,turbulent eddies that transport the dispersed phase)and the large-scale(i.e.,circulation cells and central plume oscillations)circulation,thereby characterizing the"reactor-scale".Unfortunately,the precise definitions behind multi-scale connections have not been unveiled thus far.Although it is thought that the"bubble-scale"is determined by the connection of three local parameters(namely,the liquid velocity,void fraction,and bubble sizes),a precise and analytical description of the connections between the"local-scale"parameters as well as their upscaling towards the"reactor-scale"in the different flow regimes is elusive to date.For this reason,bubble columns are still modeled using macroscopic methods(i.e.,empirical or semi-empirical correlations),rather than physical-based approaches; this is a major shortcoming as empirical/semi-empirical correlations can hardly be applied beyond the range of operating conditions and system designs over which they were obtained.
查看更多>>摘要：In order to investigate the separation mechanism and provide some guidance for the separator design,the single-phase flow field of the bubble separator for the Molten Salt Reactor is simulated numerically by Reynolds Stress Model.The results show that a low-pressure and high-velocity region is induced under the obstruction of the guiding vanes in the flowing channel and the tangential velocity distribution resembles the Rankine vortex.Besides,the swirl number along the axial position increases first and then decreases due to the improvement of the first light phase outlet.Moreover,the effects of the key structure parameter of the generating swirler including deflection angle,the guiding vane number and the hub ratio on the flow field are investigated and their sensitivity analyses are conducted at the same time.It demonstrates that the deflection has the largest influence on the flow field and the hub ratio is the second.
查看更多>>摘要：Natural gas is regarded as a cleaner fuel and could be a feedstock for chemicals production.In some regions where petroleum resources are limited,the coal-based synthetic natural gas(SNG)process could be an alternative option.Generally,the coal-based SNG process begins with the gasification of coal to produce crude syngas,implying that coal rank and gasification technology would have a significant impact on the process performance and product quality.Within this work,a series of coal-based SNG processes with different coal ranks and gasification technologies are investigated and analyzed based on rigorous process modeling and simulation.Sensitivity analysis is carried out to optimize key parameters and explore their effects on process performance.The results indicate that the low-rank coal with the Lurgi gasifier could effectively improve the energy conversion efficiency when compared with various combinations of coal ranks and gasification technologies.The lignite coal with the Lurgi gasifier could improve the energy efficiency up to 61% with a Wobbe index of 52 MJ/m3,a carbon yield of 44%,and the minimum CO2 emission of 3.5 kgCO2/kgSNG.The economic evaluation suggests that the total equipment investment for the process based on lignite is 20% and 27% lower than that based on bituminous and anthracite,respectively.Furthermore,the Lurgi gasifier could save 12% equipment investment compared with the Texaco gasifier when the process is based on the same coal rank.The research could provide quantitative guidance for the design and optimization of coal-based SNG processes.
查看更多>>摘要：To create efficient-high performing processes,one must find an optimal design with its corresponding controller that ensures optimal operation in the presence of uncertainty.When comparing different process designs,for the comparison to be meaningful,each design must involve its optimal operation.Therefore,to optimize a process'design,one must address design and control simultaneously.For this,one can formulate a bilevel optimization problem,with the design as the outer problem in the form of a mixed-integer nonlinear program(MINLP)and a stochastic optimal control as the inner problem.This is intractable by most approaches.In this paper we propose to compute the optimal control using reinforcement learning,and then embed this controller into the design problem.This allows to decouple the solution procedure,while having the same optimal result as if solving the bilevel problem.The approach is tested in two case studies and the performance of the controller is evaluated.The case studies indicate that the proposed approach outperforms current state-of-the-art simultaneous design and control strategies.This opens a new avenue to address simultaneous design and control of engineering systems.
查看更多>>摘要：Vanillin(VAN)is widely used in medicine,food and optoelectronics,but its low solubility leads to the decrease of bioavailability and increase of application costs.Three APIs-nico-tinamide(NIC),isonicotinamide(INM)and isoniazid(INH)were chosen to form cocrystals with VAN,aiming at improving the solubility of VAN and APIs simultaneously.Two co-crystals(VAN-NIC,VAN-INM)were obtained through cocrystallization while VAN reacted with INH to form one novel compound(VAN-INH).The crystal structures were characterized by single-crystal X-ray diffraction(SCXRD),Powder X-ray diffraction(PXRD),Fourier-Transform Infrared Spectroscopy(FT-IR)and Differential Scanning Calorimetry(DSC).The melting temperatures of VAN-NIC and VAN-INM cocrystals are between this of VAN and APIs.Compared with pure VAN and APIs,the solubility and dissolution rate of VAN-NIC and VAN-INM are significantly increased.The melting temperature of VAN-INH is greater than that of VAN and INH,and the solubility and dissolution rate is not increased significantly.The intermolecular energy between VAN and APIs as well as lattice energies of cocrystals/novel compound were computed to elucidate the formation mechanism and stability.The present investigation opens a new pathway for the development of natural product-drug cocrystals to improve solubility and dissolution rate of natural product.
查看更多>>摘要：In this work,expanded perlite(EP)was modified with a polymer of trimesoyl chloride and phenylenediamine,and evaluated as a novel competent adsorbent for aquatic arsenic(As(III))removal.The chemical structure and morphology of the developed polymer-modified EP(PM-EP)adsorbent were investigated by Fourier transform infrared spectroscopy,as well as scanning electron microscope/energy equipped with dispersive X-ray spectroscope.The conditions of batch removal such as the solution pH,contact time,sorbent dosage,and initial As(III)concentration were analyzed by factorial design.Based on the non-linear and linear Langmuir model that well correlates equilibrium data,the removal capacity of the produced PM-EP adsorbent was estimated as 447.9 mg g~(-1)and 454.5 mg g~(-1),respectively at optimized conditions(pH: 6; contact time: 60 min; adsorbent dosage: 10 g L~(-1)and temperature: 24 ℃).The As(III)adsorption mechanism onto PM-EP adsorbent was well described by the non-linear pseudo-second-order kinetic model.The prepared PM-EP adsorbent was subjected to a ten cycling-adsorption/desorption test and the results demonstrated that it had appreciated reuse performance until seven cycles.The removal efficiency of PM-EP was determined in the case of wastewater samples.The overall evaluation suggested that the synthesized PM-EP adsorbent could be a powerful alternative adsorbent for decontamination of As(III)ions from wastewaters and drinking waters.
Didilia lleana Mendoza-CastilloHilda Elizabeth Reynel-AvilaLaura Gabriela Elvir-Padilla
11页
查看更多>>摘要：The assessment of bone char for the adsorption of toxic dental clinic pollutants is reported.Different conditions for bone char preparation via pyrolysis and its adsorption properties were evaluated using fluoride,mercury and arsenic as the target pollutants.The best pyrolysis conditions to improve the adsorption properties of this adsorbent for the removal of these dental clinical pollutants were identified.The best bone char was employed to quantify the experimental isotherms of the adsorption of mercury,fluoride and arsenic at pH 6 and 20-40 ℃.Results showed that the dehydroxylation of hydro-xyapatite contained in the bone char affected its adsorption properties for the removal of these pollutants and not only its defluoridation properties as has been already reported in the literature.It was concluded that the degree of hydroxy apatite dehydroxylation affected the ligand exchange involved in the adsorption mechanism of bone char for the removal of these adsorbates.Theoretical calculations with statistical physics and artificial neural networks indicated that fluoride and mercury adsorption on bone char was an endothermic multi-molecular process,while the arsenic adsorption was also endothermic but implying mono-adsorbate interactions.Bone char showed the best maximum adsorption capacities for fluoride(_(0.4)-1.58 mmol/g)followed by mercury(0.14-_(0.2)3 mmol/g)and arsenic(0.06-0.14 mmol/g),respectively.Calculated adsorption enthalpies for these pollutants ranged from 25.4 to 39.4 kj/mol.A detailed description of the adsorption mechanism and possible interactions involved in the removal of these dental clinic pollutants with bone char were also provided.This study contributes with theoretical and experimental results to support the development of an in situ solution for facing the water pollution problem caused by the dental clinics,which is an unregulated health care sector in terms of local and international legislations for water quality protection.
查看更多>>摘要：Emulsion viscosity and membrane permeation rate(MPR)are the major factors influencing the wall shear stresses in the membrane pores.However,the effect of the discrete phase viscosities and their relationship with the MPR is not well elaborated.The relationship between droplet size and the continuous phase viscosity at different MPRs was investigated.At higher MPR,the emulsion droplet size was observed to decrease with continuous phase viscosity due to the increase in the wall shear stress in the pores,as the thickness of the lubrication layer between the droplets and the pore walls increases with viscosity.While at low MPR,the droplet size increased with viscosity due to coalescing as the rate of surfactant diffusion onto the interface of the new droplets reduced.The MPR was observed to complement or contrast the effects of the continuous phase viscosity on droplet formation in the membrane pores,depending on its relative magnitude.
查看更多>>摘要：Reverse Osmosis(RO)is one of the widely adopted methods for water desalination to mitigate shortage of freshwater for domestic,irrigation and industrial consumption.Recently RO is also used as a draw solution regeneration step for most hybrid Forward Osmosis-Reverse Osmosis(FO-RO)systems used for water desalination.Accurate model is required which is more flexible and reliable,to design and operate RO treatment plants for producing freshwater from various water resources.However,most models do not represent multi element field scale RO systems accurately.Plant engineers widely use the available commercial programs for the design of multi element RO systems where the computational code is not provided,which makes the program inflexible.This work presents a computational tool developed on the python platform for the prediction and analysis of the RO process employed in a hybrid FO-RO system.A steady state model based on the solution-diffusion and film theory is established by employing concentration polarization,pressure drop and average solution properties in the computational calculations of the RO process.The model is used to design and estimate the performance parameters of an entire RO system having multiple membrane elements installed in a pressure vessel.A comparison between the outputs obtained by the model and membrane manufacturers software shows good agreement.
查看更多>>摘要：Current challenges faced by typical industrial production processes,such as distillation unit(DU),include achieving optimum operation with varying production performance.This paper proposes a mechanism-embedded neural network(MENN)modeling and operation optimization strategy(OOS)to solve this problem.According to the physical process mechanisms,we customize the neural network structure and design key correlation constraints.This ensures that the developed MENN model can accurately reflect the process characteristics.On this basis,the operation optimization problem is formulated to adjust the top temperature of the distillation column(TTDC)to produce qualified products.The strategy,with the process physical mechanisms as the basis for the operation guidance decision,alleviates the operation blindness,especially during transition process.Industrial experiments have illustrated the proposed strategy could adapt to the different production performance.During the experiment,the proposed OOS outperformed the OOS developed by a commercial company and improved the product qualification rate.
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