查看更多>>摘要：Hydrodynamic cavitation (HC), as a new AOP, has been tried to treat some organic dye wastewater. In traditional HC equipment only positive pressure from water pump was used, which results in a low degradation extent. In this paper, the negative pressure from water pump is used to intensify the whole HC effect for enhancing the decolorization and mineralization of methylene blue (MB) in wastewater. Some influence factors (orifice plate hole number, inlet pressure, initial concentration and solution temperature) on MB degradation efficiency are studied. The determined results of Total Organic Carbon (TOC) and Liquid Chromatograph-Mass Spectrometer (LC-MS) were used to identify MB mineralization extent and confirm the intermediate products during MB degradation, respectively. The results showed that, under the conditions of low temperature, high inlet pressure and moderate dye concentration, the negative pressure assisting hydrodynamic cavitation (NPA-HC) system displayed a significantly enhanced MB degradation effect. The most efficient combination of 25 hole negative pressure assisted 3 hole positive pressure is obtained. At 30 °C in 10 mg/L MB solution, the degradation ratios are 27.43% (in NPA-HC) and 97.48% (in NPA-HC+H2O2 (MB/H2O2 = 1.0:7.5 in molar ratio)), respectively. And that, in single positive pressure HC system the MB degradation ratio is only 16.23%. This study provides a feasible method for intensifying organic dye HC degradation and enlarging wastewater treatment scale.
查看更多>>摘要：A two-dimensional non-equilibrium and non-linear lumped kinetic model of liquid chromatography is formulated and numerically approximated to simulate the separation of multi-component mixtures in a packed fixed bed cylindrical column operating under isothermal conditions. The model equations incorporate the bi-Langmuir adsorption thermo-dynamics as well as the radial and axial variations of concentration. By introducing distinct regions of injection at the column inlet, radial concentration gradients are generated to intensify the effect of mass transfer rate in the radial-direction, inside the column. The mathematical model is developed by a system of non-linear convection-diffusion partial differential equations for mass balance in the mobile phase, coupled with differential equation for mass balance in the stationary phase and algebraic equations for adsorption isotherm. In this study, a high-resolution, semi-discrete, finite-volume technique is formulated and applied to gain the numerical solution of the governing non-linear-model equations. A few numerical case studies are performed to investigate the effects of the various critical parameters on the process performance. The developed numerical algorithm provide an efficacious mechanism for investigating the retention behavior, systematic monitoring and efficient operation of non-equilibrium, liquid chromatographic processes.
Krzysztof KaczmarskiMateusz PrzywaraEwa Lorenc-Grabowska
14页
查看更多>>摘要：To gain a deeper insight into the adsorption kinetics mechanism, the adsorption of p-chlorophenol (PCP) from water, cyclohexane, and heptane on surface chemistry modified activated carbons was modeled by the general rate (GR) differential mass transport model, which takes into account external and internal mass transfer resistance. Due to the fact that the particles of AC are characterized by a wide particle size distribution (PSD) and pore diameter distribution (PDD), which are usually not considered for the simulation, our experimental dates were modeled with the GR model, in which PSD and PDD were included. It was found that, for organic phases, mainly the slow surface adsorption-desorption process controls mass transfer. In the case of water, the mass transfer was controlled by molecular diffusion in pores or by slow surface adsorption depending on AC. It was also shown that neglecting the PSD can lead to errors in the evaluation of the values of the adsorption model parameters, whereas, on the other hand, the pore diameter distribution can be successively approximated by average pore diameter.
查看更多>>摘要：Fouling affects heat exchangers' performance leading to additional utility requirements and economic penalties. Performance monitoring is required to ensure that exchangers operate within allowable limits. Conventional techniques use overall heat transfer rate to monitor thermal performance. These techniques fail when the heat transfer rate remains constant, which is the case anytime a heat exchanger has feedback control on temperature. In this paper, we propose an approach to monitor fouling in heat exchangers that have closed-loop control. Our approach is based on excess pressure drop and thermal load. A monitoring chart is also proposed based on combined hydraulic and thermal performance indicators. The proposed monitoring charts are demonstrated on two case studies - a cooler with a utility on the tube-side and a heater with the utility on the shell-side. The results show that even when setpoints and flowrates change due to process requirements, the proposed approach can effectively monitor fouling and identify if the operation is within allowable performance bounds. The results can be used to schedule the cleaning of the exchangers at an appropriate time so as to avoid excessive economic losses.
Alexandre Mendonca TeixeiraLara de Oliveira ArinelliJose Luiz de Medeiros
19页
查看更多>>摘要：Dew-point adjustments and reclamation of thermodynamic gas-hydrate inhibitors injected in subsea flowlines are common operations in offshore natural gas rigs characterized by high costs, power consumption and carbon emissions. Typically, offshore plants employ triethylene-glycol absorption for water dew-point adjustment and Joule-Thomson expansion for hydrocarbon dew-point adjustment, while hydrate inhibitor reclamation is applied only on aqueous-inhibitor streams for re-concentration. To implement economically sustained post-combustion carbon capture on offshore rigs, a more efficient gas processing is necessary. This work contemplates a new process - supersonic separator inhibitor-reclamation - which recovers inhibitors from saturated raw-gas via supersonic separation with liquid-water injection additionally yielding exportable liquefied-petroleum-gas and natural gas with adjusted dew-points. This process dramatically improves profitability for thermodynamic inhibitors methanol, ethanol and monoethylene-glycol, creating an economic leverage that affords a post-combustion capture plant avoiding about 43% of carbon emissions. Even including post-combustion capture penalties, the supersonic separator inhibitor-reclamation process achieves a higher net value than the conventional gas processing without carbon capture. A multi-criteria sustainability assessment, based on quantitative metrics and qualitative aspects over all sustainability dimensions, evinces the supersonic separator inhibitor-reclamation process with carbon capture as more sustainable than the conventional counterpart for all inhibitors, whereas among the three inhibitors, the gas processing with monoethylene-glycol was ranked as the more sustainable for offshore rigs.
查看更多>>摘要：In this paper, we consider distributed simultaneous state and parameter estimation for a class of nonlinear systems, for which the augmented model comprising both the states and the parameters is only partially observable. Specifically, we first illustrate how the sensitivity analysis (SA) can select variables for simultaneous state and parameter estimation. Then, a community structure detection (CSD) based process decomposition method is proposed for dividing the entire system into interconnected subsystems as the basis of distributed estimation. Next, we develop local moving horizon estimators based on the configured subsystem models, and the local estimators communicate with each other to exchange their estimates. Finally, an SA and CSD based distributed moving horizon estimation (DMHE) mechanism is proposed. The effectiveness of the proposed approach is illustrated using a chemical process consisting of four connected reactors.
查看更多>>摘要：This special issue focuses on the important topics related to the development and application of membranes for challenging environments. As guest editors, we are pleased to present you with the 13 selected articles. Currently, membrane-based technologies have found a great variety of industrial applications, covering not only liquid and gas separation, but also energy production and storage. The range of industrial applications that takes advantages of membranes is very impressive and will continue to grow in the years to come. Statistics released by BCC Research indicated the healthy market growth of membrane technologies for many processes. For instance, the global membrane filtration market (BCC Research, 2020a) was reported at $12.71 billion in 2018 and is projected to grow at a compound annual growth rate of 6.24%, reaching $20.67 billion by 2026. The market for the ion exchange membrane (BCC Research, 2020b) meanwhile is forecasted to grow significantly from $800 million in 2019 to $1.05 billion by 2027.
查看更多>>摘要：The use of CO2 towards the production of chemicals can help in the decarbonization of industry, but the transformation of such a stable compound is a challenge. This work uses genetic algorithms for the design of multi bed reactors for the hydrogenation of CO2 towards handy products. Two cases of study were evaluated. The production of biomethane from biogas, where the presence of methane in the feedstock represents an additional challenge to achieve a high conversion, and the production of methanol. The optimization addressed the design, bed sizing and number of beds, and the operating conditions of the feedstock, composition, and temperature profile. The optimal configuration of the biomethanation reactor consists of 2 beds using a H2 to CO2 ratio of 2.75, operating at 15 atm, limiting the AT at each bed to 100 K. A lower number of beds is required if a larger △T_(max) is allowed, improving the reactor conversion. The methanol production reactor is recommended to consist of 6 beds operating at 50 atm, with a feed ratio H2 to CO2 of 3.5, requiring less catalyst than at higher pressure.
查看更多>>摘要：Kinetics of Henry reaction was performed to investigate the performance of fluorapatite. (FAP) catalyst. It was found that the catalyst showed the highest conversion and selectivity of 65% and 80%, respectively at 323 K. Kinetic model was validated, and the absence of mass-transfer resistance was proved by the Weisz Prater criterion. The as-synthesized catalyst is characterized using BET nitrogen adsorption-desorption, FTIR, FE-SEM, TPD-CO2, XPS, and XRD. Effect of catalyst loading, temperature, mole-ratio, speed of stirring, and solvents were studied. FAP catalyst showed good reusability up to four cycles.
查看更多>>摘要：Global kinetic models capable of capturing experimentally observed features of catalytic reactions are vital in design and optimization studies. In this work, a detailed analysis of the selective catalytic reduction of NO and NO2, particularly in automotive exhaust control is undertaken. The prominent metal based catalysts for this reaction range from Pt, Au & Rh to cheaper options including Cu, Ag & Co supported on Al2O3, SiO2, and occasionally, zeolites. Here, we focus on Ag & Co supported on Al2O3 catalysts, and propose a computationally tractable kinetic model capable of capturing the observed SCR features across a range of catalyst synthesis and reactor operating conditions. In particular, the effects of metal loading on catalyst performance are closely examined. In SCR, an important aspect is the catalytic activity at higher inlet O2 concentrations. The global kinetic model proposed here is shown to predict the trends with respect to reactor temperature and inlet feed compositions (including O2), well, for both catalysts.
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