The dynamic adsorption isotherms of CO2-EGR were measured by using a Intelligent Gravimetric Analysis system.In the beginning stage of CO2 injection, all the injected CO2 enters into the adsorbent and the mole fraction of CH4 (yCH4) keeps 1.0. The CH4 recovery factor (RCH4) increases. The during of this stage (tcd) depends on the selectivity of CO2 over CH4 ( SCO2/CH4). A adsorbent with large SCO2/CH4 has long tCD. When SCO2/CH4 is greater than 1.0, CO2 reduces the fraction of CH4 in the adsorbed phase (xCH4) and more CH4 is driven out. In the second stage,the injected CO2 competes with CH4 for adsorption. The cumulative RCH4 of this stage is much larger than that of the initial stage. However, yCH4 decrease sharply. pCH4 in the whole CO2 injection is always larger than that before CO2 injection, suggesting CH4 desorption results from the displacement by CO2 rather than from pressure depletion.
17,846 PPNs with the diamond-like topology were computationally screened to identify the optimal adsorbents for the removal of H2S and CO2 from humid natural gas based on the combination of molecular simulation and machine learning algorithms. The top-performing PPNs with the highest adsorption performance scores (APS) were identified based on their adsorption capacities and selectivity for H2S and CO2. The strong affinity between water molecules and the framework atoms has a significant impact on the adsorption selectivity of acid gases. We proposed two main design paths (LCD ≤ 4.648 Å, Vf ≤ 0.035, PLD ≤ 3.889 Å or 4.648 Å ≤ LCD ≤ 5.959 Å, ρ ≤ 837 kg·m-3) of high-performing PPNs. We also found that artificial neural network (ANN) could accurately predict the APS of PPNs. N-rich organic linkers and highest isosteric adsorption heat of H2S and CO2 are main factors that could enhance natural gas sweetening performance.
A new method for integrated ionic liquid (IL) and absorption process design is proposed where a rigorous rate-based process model is used to incorporate absorption thermodynamics and kinetics. Different types of models including group contribution models and thermodynamic models are employed to predict the process-relevant physical, kinetic, and thermodynamic (gas solubility) properties of ILs. Combining the property models with process models, the integrated IL and process design problem is formulated as an MINLP optimization problem. Unfortunately, due to the model complexity, the problem is prone to convergence failure. To lower the computational difficulty, tractable surrogate models are used to replace the complex thermodynamic models while maintaining the prediction accuracy. This provides an opportunity to find the global optimum for the integrated design problem. A pre-combustion carbon capture case study is provided to demonstrate the applicability of the method. The obtained global optimum saves 14.8% cost compared to the Selexol process.
Adsorption of CO2 from post-combustion flue gas is one of the leading candidates for globally-impactful carbon capture systems. This work highlights opportunities and limitations of sub-ambient CO2 capture processes utilizing a multi-stage separation process. A hybrid process design using a combination of pressure-driven separation of CO2 from flue gas followed by CO2-rich product liquefaction to produce high purity (>99%) CO2 at pipeline conditions is considered. The economic viability of applying pressure swing adsorption (PSA) processes using fiber sorbent contactors with internal heat management were found to be most influenced by the productivity of the adsorption system. Three exemplar fiber sorbents (MIL-101(Cr), UiO-66, and zeolite 13X) were considered for application in the sub-ambient process of PSA unit. MIL-101(Cr) and UiO-66 fiber composites were estimated to have costs of capture as low as $61/tonne CO2.
This paper investigates the effect of inlet shape, entrance length and turbulence promoters on mass transfer by using 3D printed electrolyzers. Our results show that the inlet design can promote turbulence and lead to an earlier transition to turbulent flow. The Reynolds number at which the transition occurs can be predicted by the ratio of the cross-sectional area of the inlet to the cross-sectional area of the electrolyzer channel. A longer entrance length results in more laminar behavior and a later transition to turbulent flow. With an entrance length of 550mm, the inlet design did no longer affect the mass transfer performance significantly. The addition of gyroid type turbulence promoters resulted in a factor 2 to 4 increase in mass transfer depending on inlet design, entrance length and the type of promoter. From one configuration to another, there was a minimal variation in pressure drop (<16 mbar).
This study develops a model to predict the CO2 hydrate layer thickness. As to achieve this, we need the mass transfer coefficients at the interface between water phase and CO2 hydrate layer and the diffusion coefficients in CO2 hydrate. Firstly, we conducted the visualization experiment of CO2 hydrate layer dissolution behavior. From the experiment, we obtain the mass transfer coefficient on the CO2 hydrate layer. The experimental results show good agreement with the existing empirical equation. Secondly, we conducted the molecular dynamics simulation of CO2 hydrate to obtain the self-diffusion coefficients of CO2 and H2O molecules. As to calculate the self-diffusion coefficients, we identified inter-cage hopping and intra-cage movement of molecules based on each molecule travel distance. Finally, the results indicate that the kinetic model we proposed reproduce the layer thickness on the order.
Molecular simulation has emerged as an important sub-field of chemical engineering, due in no small part to the leadership of Keith Gubbins. A characteristic of the chemical engineering molecular simulation community is the commitment to freely share simulation codes and other key software components required to perform a molecular simulation under open-source licenses and distribution on public repositories such as GitHub. Here we provide an overview of open-source molecular modeling software in Chemical Engineering, with focus on the Molecular Simulation Design Framework (MoSDeF). MoSDeF is an open-source Python software stack that enables facile use of multiple open-source molecular simulation engines, while at the same time ensuring maximum reproducibility.
Cylindrical lamps are usually equipped in the tubular UV reactor to offer UV radiation. This paper describes the axisymmetric characteristics of UV radiation from the cylindrical UV lamp. Axisymmetric lamp emission models are developed in a two-dimensional axisymmetric space for the line source, the superficial source and the volumetric source. The present axisymmetric lamp emission models are easy to understand and of simple mathematical expressions. The experimental data in literature is used to validate the present axisymmetric lamp emission models. Good agreements have been obtained between the experimental data and the computations. A comparison show that the present models obtain the identical results as previous models.
Weisz-Prater number (NW-P) is often applied to assess the internal diffusion effect in heterogeneous catalytic reactions. However, the traditional calculation method with excessive empirical reference values affects the accuracy remarkably. A series of Pt/HPMo/SBA-15 catalysts with the pore size as a single variable were prepared to calculate the NW-P with a developed model combining the diffusion-reaction kinetic method. Utilizing dimensionless variables, internal effectiveness factor (η) and Thiele modulus (Φ_n), and the apparent activities over catalysts with different diffusion capacity, NW-P is obtained with improved accuracy. For the diffusion effect on the hydrotreatment of n-C16, according to the more precise NW-P, the pore size should be not less than 10 nm to avoid the step-limitation of internal diffusion in the premise of adequate acid sites. Using the novel method, a conclusion is drawn that the formation of m-i-C16 is more susceptible to internal diffusion than the consumption of n-C16.
A micro membrane adsorber with deep-permeation nano structure (DPNS) has been successfully fabricated by flowing synthesis. The nanoparticles are in situ assembled in membrane pores and immobilized in each membrane pores along the direction of membrane thickness. The nanoparticles with a lower size and thinner size distribution can be achieved owing to the confined space effect of the membrane pores. As a concept-of-proof, the nano ZIF-8 and ZIF-67 are fabricated in porous membrane pores for Methyl orange (MO) and Rhodamine B (RhB) adsorption. The adsorption rate is increased significantly owing to the enhanced contact and mass transfer in the confined space. The adsorption capacity for the RhB is also increased, since the size of the nanoparticles assembled in membrane pores is smaller with more active sites exposed. This micro membrane adsorber with DPNS has good reusability, and can provide a promising prospect for industrial application.
Membrane absorption (MA) has a great prospect for CO2 capture. In MA modeling, conventional 1D- and 2D- models make simplification of membrane contactor (MC) geometry. Geometry simplification allows an easy process modeling and numerical solution, however, is only reasonable for particular MCs. Here, efforts are underway to quantify the geometry effect on the MA-CO2 performance. First, we proposed a full 3D model without geometry simplification for simulating the MA-CO2 process in real MCs and then validated it with experimental data. More importantly, we highlighted a preferable hybrid model in which a correction factor (F) was introduced to the 2D simulation results to make their combination approximately equal to the 3D simulation values. The F was correlated with dimensionless parameters obtained from computational fluid dynamics (CFD) studies for characterizing the geometry effect. Such hybrid modeling contributes to characterizing the influence of geometry on the MA-CO2 performance and improving computation accuracy-efficiency combinations.
In this study, effect of swirling addition on the liquid mixing behavior of multi-orifice-impinging transverse jet mixer has been investigated by planar laser induced fluorescence as well as large eddy simulation (LES). In the case of swirling addition into the jet flow, there exists an optimized swirling jet angle or optimized jet-to-cross velocity ratio for the fixed mixer configuration. A larger swirling jet angle will make the flow dominated by the swirling, resulting in a slower mixing process. Interaction of swirling crossflow with no-swirling injected streams, or with swirling injected streams in the opposite direction is beneficial for the mixing. LES predictions show that many small vortices are produced homogenously due to intensified impingement in the case of opposite swirling directions, leading to a relative fast mixing process in several milliseconds. Whereas the mixing is restrained when the swirling directions of two flows are the same.
The study proposed an isotopes-tagging method for investigation of reactions under the atmosphere of product gas. To illustrate this method, the calcination kinetics of calcium carbonate Ca13CO3 in CO2 atmospheres were investigated by monitoring 13CO2 produced using a micro fluidized bed reaction analyzer (MFBRA). The results demonstrated that the presence of CO2 in the reaction atmosphere increases the apparent activation energy. The increase in the apparent activation energy is, however, significantly overestimated by the TGA because of the excessive suppression by stagnated product gas inside the sample crucible. Comparatively, the results from the MFBRA are due primarily to the thermal equilibrium limitation, because the gas diffusion in the MFBRA is essentially eliminated. It is thus concluded that the MFBRA is quite capable of acquiring the real kinetics of reactions in such inhibitory atmospheres. atmosphere.
This study proposes a multiperiod mixed integer linear programming model for the management of a single municipal solid waste (MSW) treatment plant with sustainability as the objective. Discrete and continuous variables define the capacity selections for diverse MSW technologies, and the operation of the MSW network, respectively. The economic target is considered to maximize the net present value. The environmental impact is the minimization of a normalized environmental objective function (NEOF). The social target is the maximization of jobs. An interesting feature about the research work is the requirement of biodrying technologies for MSW moisture content control. Due to the conflicted nature among the sustainability components, a multi-objective optimization (MO) is carried out to find the Pareto optimal solutions. The MO results show that the Pareto optimal solutions vary around profit range of US$ 4.9-8.5 billion, NEOF impact range of 3.2-3.6 units, and social benefit range of 2700-4828 jobs.
As an attractive alternative technology for the separation of long chain olefin and paraffin, a novel silver-based deep eutectic solvent (Ag-DES) was prepared and utilized for 1-octene/n-octane separation. Comprehensive reactive extraction separation experiments were performed to highlight the Ag-DES concentration and operating temperature discriminations using compounds with different ratio of 1-octene/n-octane. The novel Ag-DES showed optimal separation performance regarding 1-octene/n-octane and possessed the highest levels separation selectivity in the range 3.75-16.74 with excellent circulation stability in our best knowledge. Furthermore, FT-Raman measurements and quantum chemistry calculation were conducted to elucidate the interaction mechanism of Ag-DES in the separation of 1-octene and n-octane, which revealed that both chemical complexation and strong physical attraction existed in the complex of Ag-DES with 1-octene rather than n-octane. This study lends important insight for the development of Ag-DES reactive extraction separation process for the energy-efficient long chain α-olefin purification from F-T synthesis products.
In this work the flow behavior of granular material in flat-bottomed funnel flow silos was investigated through 3D Discrete Element Method (DEM) simulations. It is observed that particles in the flowing zone move collectively, manifested by the oscillatory fluctuations of the averaged particle vertical velocity and the non-Gaussian characteristics of the fluctuations of individual velocity around average. The delayed correlations of velocity fluctuation and the Fourier spectrums of velocity and contact force between particles were analyzed to characterize the propagation of flow fluctuation. It is found that there exist two special vertical positions in the converging zone. The lower one corresponds to the emission source from which the velocity wave propagates both upwards and downwards. The higher one locates at the upper boundary of converging zone and is characterized by the most violent fluctuation of contact force. Possible mechanisms of the appearances of these two vertical positions are discussed.
Editorial – The third “Futures” issueThis month’s volume of AIChE Journal is the third “Futures” issue. I think now we’ve established a tradition. This is my favorite issue each year.Each year we invite a group of early career researchers to contribute their pioneering works. I have sought the input of the AIChE Journal editorial team and consulting editorial board to identify contributors. The criterion is that the prospective author be seven or less years removed from her or his initial appointment as an academic, industrial, or national lab researcher.During the publication year we have a session at the Annual AIChE meeting where several of the authors have the opportunity to present their research. (This being the year of COVID-19, these presentations will unfortunately be virtual.)The “Futures” issue parallels the annual “Founders” issue; while the “Founders” issue celebrates the scholarly legacies of the greats from our profession, the “Futures” issue recognizes the research of emerging scholars.I hope that you enjoy this third installment of the “Futures” series.On behalf of the AIChE Journal editorial team, we look forward to your input and suggestions. As always, thanks for your support of
In this paper, a dynamic biomass gasification model was developed based on the hybrid peripheral fragmentation and shrinking-core (HPFS) model. To improve the accuracy of syngas generation transient prediction, the chemical kinetic model was trained using global surrogate optimization techniques. The pre-exponential factors of kinetic reactions are calibrated under non-catalytic conditions, employing experimental transient data of syngas generation rate and compositions under different temperatures and gasifying agents. The DYCORS and GOMORS were employed as the numerical solvers for finding the global optimum solution of the pre-exponential factors. The calibrated kinetic models based on both single-objective and multi-objective approaches have been validated by experimental data in four different biomass gasification scenarios. The calibrated kinetic model shows an over 95% decrease in terms of integrated squared error (ISE)-based model mismatch when compared to the original kinetic model.