Thermal Separations Research Articles

Determining desired sorbent properties for proton-coupled electron transfer-controlled CO2 capture using an adaptive sampling-refined classifier

Electrochemical CO2 capture technologies have been found to consume less energy than the industry standard of thermal separations, but their real-world applicability requires that they also operate at comparable rates. Optimizing for both low energy demands and high capture rates is complicated by trade-offs between the two objectives and the many manipulable solution chemistry variables, including species type and concentration. Here, we computationally identified the solution chemistries that are most likely to outperform thermal separations in both energy demand and capture rate for electrochemical capture driven by proton-coupled electron transfer reactions by using an adaptive sampling contour estimation method. This approach provided high confidence inferences with few simulation runs by selecting the most informative conditions to test. We found that moderately basic pKa values of the reduced form of the redox-active compound were the most important variables for low energy and high rate CO2 capture.

Ultrathin Two-Dimensional BiOCl-Bi2 S3 -Cu2 S Ternary Heterostructures with Enhanced LSPR effect for NIR Photonic Bacterial Disinfection.

Photonic disinfection, particularly near-infrared (NIR) light triggered antibacterial, has emerged as a highly promising solution for combating pathogenic microbes due to its spatiotemporal operability, safety, and low cost of apparatus. However, it remains challenging to construct NIR-responsive antibacterial agents with high light-converting efficacy and elucidate synergistic mechanisms. In this work, ultrathin two-dimensional (2D) BiOCl-Bi2 S3 -Cu2 S ternary heterostructures that can efficiently kill drug-resistant bacteria were synthesized by doping 0D Bi2 S3 and Cu2 S nanoparticles in the 2D BiOCl nanosheets via a facile one-pot hydrothermal method. Notably, the incorporation of Cu2 S nanoparticles bestows strong NIR light-harvesting capability to the composite nanosheets due to their localized surface plasmon resonance (LSPR). Upon NIR light illumination, the BiOCl-Bi2 S3 -Cu2 S nanosheets can achieve enhanced photonic hyperthermia and reaction oxygen species (ROS) generation, serving as single light-activated bi-functional photothermal/photodynamic therapeutics. High-speed hot electrons and large local electronic fields caused by LSPR might play an important role in thermal vibrations and effective carrier separations, respectively. Benefiting from the unique ternary heterostructures, both the photothermal conversion and ROS generation efficacy of BiOCl-Bi2 S3 -Cu2 S nanosheets are significantly improved compared to the binary BiOCl-Cu2 S or BiOCl-Bi2 S3 nanosheets. Accordingly, the ternary composite nanosheets can effectively kill bacteria via the NIR-driven photonic disinfection mechanism. This work presents a new type of 2D composite nanosheets with ternary heterostructures for NIR photonic disinfection.

Cation–Ligand Interactions Dictate Salt Partitioning and Diffusivity in Ligand-Functionalized Polymer Membranes

Membranes are an attractive alternative to current thermal separations due to their scalability and energy efficiency in desalinating water. Unfortunately, many of the conventional membrane materials available today are unable to differentiate between ionic solutes, especially alkali cations, compromising their use in ion–ion separations. Inspired by the ion-specific interactions exhibited by biological ion channels, recent research efforts have focused on synthesizing and characterizing new polymeric materials that incorporate ligands into polymer networks to bias solubility and/or diffusivity of one cationic species over another. Despite these efforts, little is known about the influence of incorporating ligands into polymer membranes on solubility and diffusivity of the complexing species. In this study, we first build a qualitative model of salt partitioning, diffusivity, and permeability in generic cation-complexing ligand-functionalized polymer membranes. Next, to validate our model and hypotheses, we perform atomistic molecular dynamics simulations of a 12-crown-4-functionalized membrane in the presence of alkali halide salts at low concentration. Generally, cation complexation enhances cation solubility but decreases diffusivity. Interestingly, the reduction in diffusivity is predicted to be larger than the enhancement in solubility for materials which operate by the mechanisms proposed in our physical picture, ultimately resulting in a reduction in the permeability of the selectively complexing ion.

Via Separations raises $38 million

Via Separations, a membrane start-up in Watertown, Massachusetts, has raised $38 million in a series B financing round led by NGP Energy Technology Partners. Via, one of C&EN’s 10 Start-Ups to Watch in 2019, is developing graphene oxide separation materials. It is targeting industries in which filtration can replace energy-intensive thermal separations. One example is removing solids from the black liquor that results from papermaking. Via will use the money it raised to deploy its system in the pulp and paper sector and adapt it for chemical production.

Simulating Capillary Gas Chromatographic Separations including Thermal Gradient Conditions.

This article presents a method of simulating molecular transport in capillary gas chromatography (GC) applicable to isothermal, temperature-programmed, and thermal gradient conditions. The approach accounts for parameter differences that can occur across an analyte band including pressure, mobile phase velocity, temperature, and retention factor. The model was validated experimentally using a GC column comprised of microchannels in a stainless-steel plate capable of isothermal, temperature-programmed, and thermal gradient GC separations. The parameters governing retention and dispersion in the transport model were fitted with 12 experimental isothermal separations. The transport model was validated with experimental data for three analytes using four temperature-programmed and three thermal gradient GC separations. The simulated peaks (elution time and dispersion) give reasonable predictions of observed separations. The magnitudes of the maximum error between simulated peak elution time and experiment were 2.6 and 4.2% for temperature-programmed and thermal gradient GC, respectively. The magnitudes of the maximum error between the simulated peak width and experiment were 15.4 and 5.8% for temperature-programmed and thermal gradient GC, respectively. These relatively low errors give confidence that the model reflects the behavior of the transport processes and provides meaningful predictions for GC separations. This transport model allows for an evaluation of analyte separation characteristics of the analyte band at any position along the length of the GC column in addition to peak characteristics at the column exit. The transport model enables investigation of column conditions that influence separation behavior and opens exploration of optimal column design and heating conditions.

Systematic Analysis Reveals Thermal Separations Are Not Necessarily Most Energy Intensive

Summary At the industrial level, separation of a variety of mixtures is predominantly carried out by thermally driven processes such as distillation. Nevertheless, the current literature seems to suggest that much is to be gained by replacing these processes with alternative non-thermal methods, which will potentially require a fraction of the energy used by distillation. This is primarily due to the widespread perception that thermal separation processes, particularly those that involve vaporization, are highly energy intensive. However, this belief is not well founded, because it is based on extrapolation from comparisons in the literature, many of which make ad-hoc assumptions and result in incorrect conclusions. Our analysis shows that this confusion arises because the processes utilize different types of energy: heat and electricity. Here, we present a consistent framework that enables a fair comparison between different processes that consume different forms of energies. Using this framework, we refute the general perception that thermal separation processes are inherently the most energy intensive and conclusively show through the examples of two challenging mixtures constituting components with low relative volatilities, that distillation processes, when run properly, can consume remarkably lower fuel than non-thermal membrane alternatives, which have often been touted as more energy efficient.

N-Aryl-linked spirocyclic polymers for membrane separations of complex hydrocarbon mixtures.

The fractionation of crude-oil mixtures through distillation is a large-scale, energy-intensive process. Membrane materials can avoid phase changes in such mixtures and thereby reduce the energy intensity of these thermal separations. With this application in mind, we created spirocyclic polymers with N-aryl bonds that demonstrated noninterconnected microporosity in the absence of ladder linkages. The resulting glassy polymer membranes demonstrated nonthermal membrane fractionation of light crude oil through a combination of class- and size-based "sorting" of molecules. We observed an enrichment of molecules lighter than 170 daltons corresponding to a carbon number of 12 or a boiling point less than 200°C in the permeate. Such scalable, selective membranes offer potential for the hybridization of energy-efficient technology with conventional processes such as distillation.

Tying Devices to Mitigate Pounding of Adjacent Building Blocks

Adjacent building blocks separated by thermal expansion joints are vulnerable to pounding during earthquakes. The specified Saudi building code minimum separation may be very large and does not necessarily eliminate pounding forces. This research discusses the feasibility of tying the adjacent building blocks with simple devices to mitigate structural pounding when separated by thermal joints. Six and twelve-story moment resistance frames of intermediate ductility were designed for seismic loads of moderate risk. The seismic response was studied for frames with variable separation distances in three cases related to thermal joint, code minimum separation, required separation to eliminate pounding force, and in a fourth case in which the tying device was used along with thermal separation. A linear elastic model was used to model the assigned gap links between the adjacent building blocks. The tying device was modeled with a tension-only hook element. Four normalized earthquake records were used with inelastic-time history analysis to assess the seismic response of the adjacent building blocks. The proposed tying devices reduced successfully the pounding forces by 40% to 60% for adjacent building blocks with installed thermal separations. Building damage as observed from damage index and the hysteretic response was not influenced by the pounding force, indicating that the tying may be used on existing buildings with thermal separation as a partial mitigation technique to reduce the pounding hazard in such cases. Further improvement on the tying device will increase the mitigation of the pounding hazard.

Vapor Phase Infiltration of Metal Oxides into Nanoporous Polymer Membranes for Organic Solvent Separation

Membrane-based organic solvent separations promise a low-energy alternative to traditional thermal separations but require advanced materials that operate reliably in chemically aggressive environments. While inorganic membranes can withstand demanding conditions, they are costly and difficult to scale. Polymeric membranes, such as polymers of intrinsic microporosity, are easily manufactured into form factors consistent with large-scale separations (e.g., hollow fibers), but perform poorly in aggressive solvents. Here, a new post-fabrication membrane modification technique, vapor phase infiltration (VPI) is reported that infuses polymer of intrinsic microporosity 1 (PIM-1) with inorganic constituents to improve stability while generally maintaining the polymer’s macroscale form factor and microporous internal structure (Figure 1). The atomic-scale metal oxide networks within these hybrid membranes protect PIM-1 from swelling or dissolving in organic solvents including: tetrahydrofuran, dichloromethane, and chloroform (Figure 2a). This atomic-scale metal oxide network further decreases the molecular weight cutoff (MWCO; the smallest molecular weight the membrane “successfully” rejects) in n-heptane and toluene from a MWCO of about 600 g/mol for pristine PIM-1 thin film composite membranes to 204 g/mol for hybrid AlOx/PIM-1 membranes (Figure 2b). The hybrid membranes further retain this MWCO and high levels of rejection (>95%) in solvents that traditionally swell or even dissolve pristine PIM-1 (such as ethanol and tetrahydrofuran). The decrease in MWCO and increase in stability of AlOx/PIM-1 hybrid membranes allows them to perform separations not only between solutes and solvents, but also separations of more challenging systems such as those comprising multiple solvents. For example, the hybrid AlOx/PIM-1 membranes are capable of enriching the toluene concentration in a mixture of 90 wt% toluene, 5 wt% 1,3,5-triisopropylbenzene, and 5 wt% 1,3-diisopropylbenzene from 90.0 wt% to 97.8 ± 0.3 wt%. In this talk, we will discuss the chemical mechanisms of the infiltration process that we believe create the hybrid structures necessary to support this enhanced stability and separation performance. Figure 1

Vapor Phase Infiltration of Metal Oxides into Nanoporous Polymers for Organic Solvent Separation Membranes

Membrane-based organic solvent separations promise a low-energy alternative to traditional thermal separations but require materials that operate reliably in chemically aggressive environments. While inorganic membranes can withstand demanding conditions, they are costly and difficult to scale. Polymeric membranes, such as polymer of intrinsic microporosity 1 (PIM-1), are easily manufactured into forms consistent with large-scale separations (e.g., hollow fibers) but perform poorly in aggressive solvents. Here, a new postfabrication membrane modification technique, vapor phase infiltration (VPI), is reported that infuses PIM-1 with inorganic constituents to improve stability while maintaining the polymer’s macroscale form and nanoporous internal structure. The atomic-scale metal oxide networks within these hybrid membranes protect PIM-1 from swelling or dissolving in solvents. This stability translates to improved separation performance in a variety of solvents, including solvents capable of dissolving PIM-1. The infiltrated inorganic phase also appears to give new control over solute sorption in organic solvent nanofiltration (OSN). These hybrid membranes further show promising performance for organic solvent reverse osmosis (OSRO) separations in challenging solvents, even at small-molecular-weight differentials (14 Da). Because the VPI process can be integrated with state-of-the-art membrane modules, this treatment could be readily adopted into the large-scale manufacturing of advanced membranes.

Effects of a freeze-thaw-pressing muscle separation on the biochemical quality and self-stability of leg meat from red snow crab (Chionoecetes japonicus)

To evaluate the product quality of leg meat from red snow crab (Chionoecetes japonicus) prepared with a novel freeze-thaw-pressing muscle separation (FTPS), the biochemical properties were compared with those of two thermal muscle separations (boiling; BS or steaming; SS). Among the muscle separations, the yield from merus part was the highest with the FTPS (22.0 ± 2.1 g), followed by SS (20.3 ± 1.4 g) and BS (17.5 ± 1.8 g). The proximate compositions in the three leg meats were similar, but the quantitative analyses for the water extractive components (free amino acids, minerals, organic acids and ATP-related compounds) revealed that all the contents were notably higher in the leg meat with FTPS (LM-FTPS) than that with BS or SS. The sensorial acceptability test demonstrated the storable day limits of the LM-FTPS at −20 °C, 0 °C or 10 °C, but it was suggested only in storage either at 0 °C (3 days) or 10 °C (1 day), the day limits corresponded to 30 mg% of the VBN value and 5 log CFU g−1 of the total viable cell count. In the case of −20 °C storage, the storable day limit suggested within 5 days, based on the VBN value.

Design and Analysis of a New Six-Phase Fault-Tolerant Hybrid-Excitation Motor for Electric Vehicles

Fault tolerance is a key factor for motor driving systems in electric vehicles. To realize the high fault-tolerance under short-circuit, open-circuit, and demagnetization fault, this paper proposes and investigates a new six-phase fault-tolerant hybrid-excitation motor. First, the single concentrated armature winding is adopted to achieve electrical, magnetic, thermal, and physical separations. The unequal teeth width and the asymmetric air-gap length are designed and optimized to reduce torque ripple and distortion of phase back EMF. Furthermore, the field windings are designed to provide magnetization under demagnetization fault. In addition, the motor is designed with the simple structure and no sliding contacts, as well as robust rotor with no windings. Moreover, the topology and operating principles of the proposed motor are analyzed; the characteristics of the proposed motor under healthy and fault conditions are investigated using finite-element analysis. Finally, the calculation results are given to verify the validity of the high fault tolerance for the proposed motor.

Study of XeF2 fluorination potential against Rh2O3, RuO2, ZrO2, and U3O8 for use in reactive gas recycle of used nuclear fuel

Triuranium octoxide (U3O8) and stable surrogate oxides of selected fission product species representative of a Used Nuclear Fuel (UNF) matrix typical of Light Water Reactor (LWR) service were fluorinated using an alternate, solid-phase fluorinating agent, XeF2. This fluorination reaction formed volatile and non-volatile compounds and demonstrated the possibility of chemical and thermal separations of the UNF matrix based on this approach. A series of experiments was conducted at the milligram quantity scale using a Shimadzu DTG-60 TG/DTA for testing of all non-radioactive samples and a Netzsch STA 409 TGA for testing of all radioactive samples. The fluorination and subsequent volatilization potentials were analyzed by mixing excess fluorinating agent with an oxide form of the UNF material and then heating to elevated temperatures for analysis. Thermogravimetric and differential thermal analysis allowed reaction pathways to be analyzed and suggested windows both thermally and chemically for separations of these various components. The differences in thermophysical properties of these products can be utilized as a starting point to effectively separate, isolate, and collect product streams with different compositions for further processing. The study of these chemistries could be incorporated into advanced separations methods to provide another possible solution for the long-term sustainability of nuclear energy applications.

Study of XeF2 fluorination potential against SrO, MoO3, and Nb2O5 in TG/DTA for use in reactive gas recycle

Oxides SrO, MoO3, and Nb2O5, simulating parts of the Used Nuclear Fuel (UNF) matrix were fluorinated using XeF2 to form volatile and non-volatile compounds to demonstrate the possibility of a chemical and thermal separations. Experiments were conducted using a TG/DTA instrument at the milligram quantity scale, and XRD enabled confirmation for the fluorination reaction when sample residues were present. The study of these chemistries could be incorporated into advanced separations methods to provide another possible solution for the long-term, sustainability of nuclear power as the issue of reuse and disposal of commercial fuel continues to grow.

Phase separation in thermal systems: A lattice Boltzmann study and morphological characterization

We investigate thermal and isothermal symmetric liquid-vapor separations via a fast Fourier transform thermal lattice Boltzmann (FFT-TLB) model. Structure factor, domain size, and Minkowski functionals are employed to characterize the density and velocity fields, as well as to understand the configurations and the kinetic processes. Compared with the isothermal phase separation, the freedom in temperature prolongs the spinodal decomposition (SD) stage and induces different rheological and morphological behaviors in the thermal system. After the transient procedure, both the thermal and isothermal separations show power-law scalings in domain growth, while the exponent for thermal system is lower than that for isothermal system. With respect to the density field, the isothermal system presents more likely bicontinuous configurations with narrower interfaces, while the thermal system presents more likely configurations with scattered bubbles. Heat creation, conduction, and lower interfacial stresses are the main reasons for the differences in thermal system. Different from the isothermal case, the release of latent heat causes the changing of local temperature, which results in new local mechanical balance. When the Prandtl number becomes smaller, the system approaches thermodynamical equilibrium much more quickly. The increasing of mean temperature makes the interfacial stress lower in the following way: σ=σ(0)[(T(c)-T)/(T(c)-T(0))](3/2), where T(c) is the critical temperature and σ(0) is the interfacial stress at a reference temperature T(0), which is the main reason for the prolonged SD stage and the lower growth exponent in the thermal case. Besides thermodynamics, we probe how the local viscosities influence the morphology of the phase separating system. We find that, for both the isothermal and thermal cases, the growth exponents and local flow velocities are inversely proportional to the corresponding viscosities. Compared with the isothermal case, the local flow velocity depends not only on viscosity but also on temperature.

Pilot plant formaldehyde distillation: experiments and modelling

Despite their industrial importance, only few experimental studies on distillation of aqueous, methanolic formaldehyde solutions are described in the literature. In the present work, for the first time, results from pilot-scale distillation of mixtures of formaldehyde, water, and methanol are presented. The experiments were carried out in a 250 mm diameter distillation column equipped with 2 m Sulzer BX wire gauze packing. Two variants of that packing were studied: the commercially available type and a modified type with increased specific surface. The column was operated at 1 bar at total reflux. Both the overall feed composition and the fluid dynamic loads were varied systematically in the experiments. Samples were taken above and below the packing bed as well as at one intermediate position. For analysis, the sodium-sulfite method (formaldehyde), gas chromatography (methanol), and Karl–Fischer titration (water) were used. A total of 19 experiments were carried out. The studied formaldehyde distillations are complex reactive processes due to a series of reactions taking place in both phases. The experimental data were successfully modelled with a stage based physico-chemical model for thermal separations of formaldehyde containing mixtures, which was recently developed.

Thermal design and experimental validation for optical transmitters

This paper describes a thermal design methodology for a 2.5 Gbps optical transmitter that mainly comprises a laser array of 12 VCSELs and a laser driver module. An integrated heat sink design was performed and optimized through modeling and simulation. Temperature regulation of the laser array has been performed through design and optimization of the thermal path (cavity and heat spreader) and separations (wire bonding lengths). Detailed module simulation was performed after the heat sink design and the temperature regulations. To validate the simulation results, a test vehicle of 2.5 Gbps transmitter was built up and tested under various thermal conditions. The airflow rate and ambient temperature were controlled by a wind tunnel. It has shown that the experimental and detailed module simulation results are comparable. A cooling solution with natural convection has been achieved so that the case temperature can be kept under 70 °C without using a fan. The modeling and simulation were done by using a computational fluid dynamics (CFD) program.

Thermal and mechanical separations of silicon layers from hydrogen pattern-implanted wafers

A silicon layer was successfully transferred from a hydrogen pattern-implanted wafer to another by a thermal or mechanical cleavage process. The first wafer was masked with various patterns of 2.3 micron-thick poly-silicon, and was implanted at a hydrogen dose of 4,5, or 8 1016 cm−2 with an energy of 150 keV or 180 KeV. After etching off the implantation mask, the wafer was bonded to a thermally grown oxide wafer face-to-face by low-temperature direct bonding. The bonded pair was then either heated (thermally) or bent (mechanically) until hydrogen-induced silicon layer cleavage occurred, resulting in the silicon layer transfer from the implanted wafer to the other. In this experiment, it was demonstrated that mechanical cleavage can overcome the fractional implantation area limination of thermal cleavage.

Very large thermal separations for polyelectrolytes in salt solutions

A conductivity method is used to measure the Soret coefficient and heat of transport of aqueous sodium poly(styrenesulfonate)(NanPSSA). The data are used to calculate thermal separation factors for NanPSSA dissolved in aqueous sodium chloride solutions. The calculations show that large steady-state concentration gradients in the polyelectrolyte will be established when a temperature gradient is applied to mixed NanPSSA–NaCl solutions, ranging up to 80% change in concentration per degree as the polyelectrolyte concentration approaches zero. The Soret coefficient and heat of transport of aqueous sodium benzenesulfonate are measured and compared with the corresponding values for NanPSSA.

Thermogravitational Column as a Technique for Thermal Diffusion Factor Measurement in Liquid Mixtures

Abstract Thermogravirational thermal diffusion separations are studied for benzene-n-heptane, benzene-n-hexane, toluene-n-heptane, toluene-n-hexane, carbon tetra-chloride-n-hexane, and cyclohexane-n-hexane mixtures at a mean temperature of 37.5°C. The column used was of 90 cm length with a 0.095 cm gap. Despite its length, this column can be used as a standard for the value of αT extraction when the separation factor is extrapolated to ΔT = 0°C. Thermal diffusion factors are calculated for benzene-n-heptane and benzene-n-hexane mixtures in different concentrations. For the rest of the systems investigated, αTD12 values (D12 being the ordinary diffusion coefficient) are calculated.