Finite Element Analysis And T10 Optimization Of Ozone Contactors

A finite element analysis (FEA) computer program was used to model the hydraulic characteristics and to predict the corresponding residence time distribution (RTD) curves for four full-scale ozone contactors with hydraulic capacities ranging from 14.5 to 394 m³/min (5.5 to 150 mgd). On average, model predictions for contactor efficiency (T₁₀/HDT) were within 7.9% of actual test values. The Metropolitan Water District of Southern California (Metropolitan) is using the finite element program as a design tool to optimize the hydraulics of future ozone contactors. For one template model, results from several optimization runs are presented which confirm that T₁₀/HDT increases with increasing depth-to-length (D/L) ratio and which indicate that by adding two features, vanes or wall foils, the T₁₀/HDT is improved from 0.63 to 0.68 or to 0.66, respectively. Results from the template model also indicate that the T₁₀/HDT is unchanged with the addition of a single configuration of comer fillets.     

Single-stage microscale solvent extraction in parallel microbore tubes using a monoblock distributor with integrated microfluidic junctions

This study is focused on the scale-up of solvent extraction in microbore tubes. A monoblock distributor with integrated microfluidic junctions (MDIMJ) is used for generating liquid–liquid dispersion and feeding the parallel microbore tubes. Experiments involve solvent extraction of U(VI) from simulated lean streams using 30% (v/v) tributyl phosphate (TBP) in dodecane. Polytetrafluoroethylene (PTFE) microbore tubes are used as a microscale contactor. The effects of inlet flow rate and O/A ratio on stage efficiency and percentage extraction (PE) are studied. Maximum capacity tested is 1.33 × 10^–6 m³/s (4.8 LPH). With O/A = 2/1, more than 90% extraction is achieved in a contact time of less than 3 s.     

Exploring the gas-phase anaerobic bioremoval of H2S for coal gasification fuel cell feed streams

An initial study was conducted to assess the potential feasibility of developing an anaerobic photobiofiltration process to remove trace concentrations of H₂S from gas streams such as syngas generated by coal gasification for fuel cells. Using the strain Heliobacterium chlorum, net removals of H₂S by the biomass on the order of 7–18% were obtained with a simple gas–biomass contactor energized by red light. Volumetric elimination capacities are 1–2 orders of magnitude lower than those obtained in liquid cultures under optimal conditions. This, combined with observed severe transport limitations, is an indication that the real residence time for biomass–gas contact in the photobioreactor is at least 1–2 orders of magnitude lower than the calculated value based on the ratio of the coke bed volume to gas flow rate. The quantity of aqueous medium that must be utilized to maintain active biocatalyst is shown to be quite small. Thus, the use of a gas/biocatalyst contactor should result in minimal water vapor addition to syngas streams. The challenge is designing an anaerobic photobioreactor with a significantly greater biomass surface-to-volume ratio than traditional biofiltration reactors.     

Ozone Contactor Hydrodynamics

Tracer tests were conducted at the 6,000 pounds of ozone per day Tucson, CAP Water Treatment Plant in Tucson, Arizona. The tests were designed to determine T₁₀ values through the contactors at various operating conditions. The tests were modeled using three techniques. Peclet Number was calculated for each of the runs, which would indicate the hydrodynamic conditions inside the ozone contactor. The results indicated that the increase in water flow rate and the number of cells with gas flow increased Peclet Number. The flow rate of liquid seemed to impact the Peclet Number more than gas flow. The headloss in each cell appeared to be important in controlling the distribution of liquid and gas through the cell. A correlation was developed between the product of gas and liquid phase Reynolds Number and Peclet Number.     

The ratio of triglycerides to high-density lipoprotein cholesterol is associated with the risk of chronic kidney disease in Korean men

Dyslipidemia is nephrotoxic and can result in the development of chronic kidney disease (CKD). The ratio of triglycerides (TG) to high-density lipoprotein cholesterol (HDL-C) (TG/HDL-C ratio) is well-correlated with insulin resistance and cardiovascular events. The aim of this study is to examine the association between the TG/HDL-C ratio and CKD in Korean adults. This study was retrospectively designed based on the National Health Insurance Service-National Health Screening cohort. Seventy three thousand and fifty-two participants aged between 40 and 79 years old at baseline (2009–2010) were included in the final analyses. The study population was classified into three tertile groups (T₁, T₂, and T₃) according to the TG/HDL-C ratio by sex. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for CKD were calculated using Cox proportional hazard regression models. The median follow-up duration was 5.9 years. Higher tertile groups of the TG/HDL-C ratio had lower estimated glomerular filtration rates in both sexes. The cumulative incidence of CKD of T₁, T₂, and T₃ was 11.89%, 12.90%, and 12.91%, respectively, in men and 10.17%, 10.61%, and 14.87%, respectively, in women (all p values < 0.001). Compared with T₁ of the TG/HDL-C ratio, the HRs (95% CIs) of T₂ and T₃ for CKD were 1.212 (1.118–1.315) and 1.183 (1.087–1.287), respectively, in men and 0.895 (0.806–0.994) and 1.038 (0.937–1.150), respectively, in women after being fully adjusted. Higher TG/HDL-C ratios were positively associated with CKD development in men, while middle levels of TG/HDL ratios reduced the CKD incidence in women.     

Enhancing CO2 absorption efficiency using a novel PTFE hollow fiber membrane contactor at elevated pressure

The internal structure design of membrane module is very important for gas removal performance using membrane contactor via physical absorption. In this study, a novel membrane contactor developed by weaving polytetrafluoroethylene (PTFE) hollow fibers was applied to remove CO₂ from 60% N₂ + 40% CO₂ mixture (with CO₂ concentration similar to that of biogas) at elevated pressure (0.8 MPa) using water as absorbent. Compared with the conventional module with randomly packed straight fibers, the module with woven PTFE fibers exhibited much better CO₂ absorption performance. The weaving configuration facilitated the meandering flow or Dean vortices and renewing speed of water around hollow fibers. Meanwhile, the undesired influences such as channeling and bypassing were also eliminated. Consequently, the mass transfer of liquid phase was greatly improved and the CO₂ removal efficiency was significantly enhanced. The effects of operation pressure, module arrangement, feed gas, and water flow rate on CO₂ removal were systematically investigated as well. The overall mass‐transfer coefficient (K_OV) varied from 1.96 × 10^?5 to 4.39 × 10^?5 m/s (the volumetric mass‐transfer coefficient K_La = 0.034–0.075 s^?1) under the experimental conditions. The CO₂ removal performance of novel woven fiber membrane contactor matched well with the simulation results. © 2017 American Institute of Chemical Engineers AIChE J, 64: 2135–2145, 2018     

Influence of the synthesis conditions on the curing behavior of phenol–urea–formaldehyde resol resins

The curing behavior of synthesized phenol–urea–formaldehyde (PUF) resol resins with various formaldehyde/urea/phenol ratios was studied with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicated that the synthesis parameters, including the urea content, formaldehyde/phenol ratio, and pH value, had a combined effect on the curing behavior. The pH value played an important role in affecting the shape of the DSC curing curves, the activation energy, and the reaction rate constant. Depending on the pH value, one or two peaks could appear in the DSC curve. The activation energy was lower when pH was below 11. The reaction rate constant increased with an increase in the pH value at both low and high temperatures. The urea content and formaldehyde/phenol ratio had no significant influence on the activation energy and rate constant. DMA showed that both the gel point and tan δ peak temperature (T_tanδ) had the lowest values in the mid‐pH range for the PUF resins. A different trend was observed for the phenol–formaldehyde resin without the urea component. Instead, the gel point and T_tanδ decreased monotonically with an increase in the pH value. For the PUF resins, a high urea content or a low formaldehyde/phenol ratio resulted in a high gel point. The effect of the urea content on T_tanδ was bigger than that on the gel point because of the reversible reaction associated with the urea component. Too much formaldehyde could lead to more reversible reactions and a higher T_tanδ value. The effects of the synthesis conditions on the rigidity of the cured network were complex for the PUF resins. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1368–1375, 2005     

Hydrodynamic and mass transfer performance of a new aero-ejector with its application to VOC abatement

The aero-ejector, an in-house developed gas-liquid contactor, ensures an improved gas-liquid contact, favorable to a high mass transfer in a small volume: its transfer capacity enables the elimination of 90% of pollutants from gaseous effluents in a single treatment. Through its characteristics, its use as a transfer device into a treatment process has distinct advantages. However, such an application needs modifications to make the contactor suitable for use in an industrial context (efficiency, compactness and low pressure drop). The aim of this research is to improve the contactor geometry in order to enhance its performances. Modifications have resulted in an energy improvement since an inlet gaseous pressure of was reached for a Q_G/Q_L ratio in excess of 10 and with a small loss of transfer efficiency. The study of the effect of operating parameters has identified a sizing criterion, the “useful volume”. This can be used to determine an optimal configuration for the gas-liquid contactor taking into account constraints such as pollutant solubility, pressure drop or compactness.     

Effects of hydrogen addition on methane combustion

In this study, the effect of hydrogen on methane combustion characteristic was tested. The ignition temperature (T₁₀) and burn off temperature (T₉₀) was carried out in a quartz reactor at atmospheric pressure with the mixture flow rate of 800 mL/min. The compositions of outlet gas were measured online by Gasmet DX4000 FTIR gas analyzer. The results showed that hydrogen enhanced the activity of methane. For all methane concentration range, the T₁₀ of methane could decrease 50 °C–70 °C with the H₂/CH₄ mole ratio at 0.1. For 1 vol.% methane combustion, when the H₂/CH₄ was equal to 0.05, the T₁₀ and T₉₀ could decrease 45 °C and 42 °C, respectively. When the H₂/CH₄ was 2.5, the T₁₀ and T₉₀ could decrease about 170 °C and 180 °C, respectively. Further more, CO generated in a wider temperature range when the hydrogen was added.     

Analysis of chemical methods for determination of interfacial areas in gas-in-liquid dispersions with non-uniform bubble sizes

Comparison of literature data on effective interfacial areas from sulfite oxidation and CO₂ absorption into alkali show considerable differences even for the same contactor. It is shown that the discrepancy results from the use of an overall conversion. Owing to the non-linear dependency of the conversion of the interfacial area and the non-uniformity of the τ/d_b-values of the bubbles this is not permitted. The deviation of a_chem from a_geo is larger the broader the distribution of τ/d_b and the higher the Stanton numbers are. The error can however be kept low if area measurements by chemical methods are carried out at low conversions, i.e. the gas—liquid contactor should possibly be operated as differential reactor. For a difference of a_chem from a_geo less than 15% the conversion in the smallest bubbles having largest τ/d_b-values should not exceed a value of about 0.4–0.8, the appropriate value depending on the reaction order. This presents a rather conservative guideline for efficient experimentation, however, it guarantees negligible difference of a_chem from a_geo for most practical applications.     

Combustion synthesis of SiC/Al2O3 composite powders with SiC nanowires and their growth mechanism

SiC/Al₂O₃ composite powders with SiC nanowires were synthesized using a one-step combustion synthesis method taking silica fume (SiO₂), aluminum powder (Al) and carbon black (CB) as raw materials, while ferrocene (C₁₀H₁₀Fe) was used as the catalyst. The calculated results for the relationship between the equilibrium phase and temperature of the Al–SiO₂–C system show that SiC and Al₂O₃ are the only equilibrium phases in the system. In addition, the effects of C₁₀H₁₀Fe on the combustion synthesis process and products were studied. It was found that with increasing catalyst content, the amount of residual Si in the products first decreases and then increases, the combustion temperature first increases and then decreases, and the nanowire content continues to increase. For an optimal amount of C₁₀H₁₀Fe of 0.75 wt%, almost no residual Si is observed in the product, while the combustion temperature (T_c) is high (2104 K), the SiC nanowire content is relatively high, and the nanowire aspect ratio is large. In addition, two growth mechanism models for SiC nanowires: VS and VLS were validated.     

Quantitative study of the annealing of poly(vinyl chloride) near the glass transition

Poly(vinyl chloride) displays a normal DSC of DTA curve for the glass transition when quenched from above its T_g. However if cooled slowly or annealed near the glass transition temperature, a peak appears on the DSC or DTA curve at the T_g. In this paper quantitative studies of the time and temperature effects on the production of this endothermal peak during the annealing of PVC homopolymer and an acetate copolymer are presented. The phenomenon conforms to the Williams, Landell, and Ferry equation for the relaxation of polymer chains, the rate of the peak formation becoming negligible at more than 50°C below T_g. The energy difference between the quenched and annealed forms is small. For a PVC homopolymer annealed 2 hr at 68°C, which is T_g ?10°C, the difference is 0.25 cal/g. For a 13% acetate copolymer of PVC similarly annealed, the difference is 0.36 cal/g. The measured rates of the process give a calculated activation energy of 13–14 kcal/mole for PVC homopolymer and copolymer. This appearance of a peak on the T_g curve for a polymer when annealed near the glass temperature appears to be a general phenomenon.     

Membrane Gas-Solvent Contactor Pilot Plant Trials of CO2 Absorption from Flue Gas

Membrane gas-solvent contactors have received much attention for CO₂ absorption, as the approach incorporates advantages from both solvent absorption and membrane gas separation. This study reports on pilot plant trials of three membrane contactors for the separation of CO₂ from flue gas. The contactors were porous polypropylene (PP), porous polytetrafluoroethylene (PTFE), and non-porous polydimethylsiloxane (PDMS), with the solvent PuraTreatTM F^TM. To enable performance comparison, laboratory measurements based on a gas mixture of 10% CO₂ in N₂ were also undertaken on the same contactor–solvent systems. It was found that the PP contactor experienced significant pore wetting in both laboratory and pilot plant studies. In contrast, the PTFE contactor experienced only minor pore wetting in the laboratory. However, in the pilot plant trial of the PTFE contactor extensive pore wetting was observed, and the overall mass transfer coefficient measured was comparable with the PP contactor. The non-porous PDMS contactor had an overall mass transfer coefficient two orders of magnitude less than the PP contactor, due to the greater mass transfer resistance of the polymeric film. However, the non-porous membrane does not experience pore wetting, which resulted in the overall mass transfer coefficient being similar for both laboratory and pilot plant measurements.     

Sol–gel transition characterization of thermosensitive hydrogels based on water mobility variation provided by low field NMR

Sol–gel transition properties play a key role in various applications of thermosensitive hydrogels, but conventional methods for studying the sol–gel transition have some limitations. For extensive characterization of the water–polymer interaction and microstructure change during sol–gel transition, we propose a rapid and nondestructive method based on monitoring water mobility through low field NMR (LF-NMR), and this was applied to chitosan/β-glycerophosphate (CS/GP) hydrogels. The spin–spin relaxation time (T ₂) that depicted water mobility was measured by LF-NMR within 90 s. The T ₂ component corresponding to water protons trapped in polymer networks (T ₂₁ ) was very sensitive to sol–gel transition. A remarkable decrease of T ₂₁ value indicated obvious variations of water mobility when CS/GP was heated, and a turning point was observed on the T ₂₁–time curve. The gel point associated with this turning point could be easily determined by fitting the T ₂₁–time curves to a bilinear regression model, and the results showed good accuracy and repeatability owing to the nondestructive nature of LF-NMR. Variations in water components and microstructure of CS/GP caused by water migration after solidification were also analyzed by monitoring dynamic changes of T ₂. This rapid, nondestructive method provides a powerful tool for studying the sol–gel transition of hydrogels.     

Vinylidene fluoride copolymers with fluoroolefins

Summary Copolymers of vinylidene fluoride (VDF) with fluoroolefins of the series CF₂CFX (X = F, Cl, Br, CF₃ and C₅F₁₁) have been synthesized in the 0–16 mole % CF₂CFX range. Results of physico-chemical characterisation by means of DSC techniques (T_g, T_M, H_f) and X-ray diffraction are examined and related to the nature of the substituent of the fluoroolefin. The T_g/T_M ratio varies from 0.5 for the VDF homopolymer to higher values at increased CF₂CFX content, although to a different extent for the various series of copolymers. The results show that the Beaman-Boyer empirical rule (T_g/T_M=2/3), developed for homopolymers, also applies to some copolymeric systems.     

Thermal and Mechanical Properties of Polyurethanes Derived from Mono- and Disaccharides

Thermal and mechanical properties of polyurethane (PU) sheets pre-pared from the glucose/fructose/sucrose–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system were examined by differential scanning calorimetry, thermogravimetry, dynamic mechanical analysis and tensile tests. The saccharide content was varied at a constant NCO: OH ratio of 1·0. The glass transition temperature (T_g) increased with increasing saccharide content. The incorporation of saccharides into the PU structure results in a higher crosslinking density and a higher content of hard segments. The thermal decomposition was dependent on the saccharide content, an increase leading to a lower thermal decomposition temperature (T_d). The dissociation of saccharide OH groups and NCO groups is a major part of the thermal decomposition of these PUs. Dynamic mechanical analysis revealed two kinds of relaxation: the high temperature relaxation corresponds to main chain motion and the other is a local mode relaxation due to non-reacted isocyanate groups. The tensile stress and Young’s modulus increased with the saccharide content. © of SCI.     

Relationship between pore structure and 1H‐NMR relaxation times in TiO2/poly(dimethylsiloxane) and CaCO3/poly(dimethylsiloxane) composite powders

Titanium(IV) oxide/polydimethylsiloxane (PDMS) and calcium carbonate/PDMS composite powders were obtained by adsorption of the polymer from a chloroform solution onto the inorganic particles followed by a thermal treatment. The composites were characterized by ¹H‐NMR relaxation and porosimetry. The composites present shorter spin–lattice (T₁) and spin–spin (T₂) proton relaxation times than silica‐reinforced PDMS, and the activation energies for the motions that cause spin–lattice relaxation are 5.8, 4.9, and 0.72 kJ mol⁻¹ for TiO₂/PDMS, CaCO₃/PDMS, and neat PDMS, respectively, revealing the greater rigidity of the polymer chains within the composite. Spin–spin relaxation (T₂) measurements of the composites showed a major component with a shorter T₂ and a minor component with a longer T₂. The intensity ratio of these two components is very close to the ratio between the amount of polymer that remains between the particles and that penetrating the particle pores as measured by Hg intrusion porosimetry. The shorter T₂ component was thus assigned to polymer interspersed among the particles, while the longer T₂ component was assigned to polymer within the particle pores. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2660–2666, 1999     

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the T_g and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10⁻³ S cm⁻¹ at room temperature and 1.42 × 10⁻² S cm⁻¹ at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3O₂ cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3 O₂ cell is 115.3 mAh g⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal Depolarization in the High‐Temperature Ternary Piezoelectric System xPbTiO3–yBiScO3–zBi(Ni1/2Ti1/2)O3

In the high‐temperature ternary perovskite piezoelectric system xPbTiO₃–yBiScO₃–zBi(Ni_1/2,Ti_1/2)O₃ (PT–BS–BNiT), the addition of bismuth to the A site and nickel to the B site leads to compositions that exhibit diffuse relaxor‐like behavior. For these, depolarization temperature, not Curie point, is the critical value of temperature. Depolarization temperature (T_d) is defined as the temperature at which the steepest loss in polarization occurs. This temperature is observed in poled materials through two different methods: loss tangent measurements and in situ d₃₃. Across the ternary system, multiple dielectric anomalies occurred which was observed in dielectric tests where the dielectric peak broadens and becomes frequency dependent as BNiT content increased. For different compositions, the value of T_d ranged between 275°C–375°C. Values for the piezoelectric coefficient increased with temperature up to d₃₃ = 1000 pC/N during in situ d₃₃. High temperature (up to 190°C) and high field (up to 40 kV/cm) were also applied to test ferroelectric properties in these regimes.     

Prediction of CO2/O2 absorption selectivity using supported ionic liquid membranes (SILMs) for gas–liquid membrane contactor

Given their unique and tunable properties as solvents, ionic liquids (ILs) have become a favorable solvent option in separation processes, particularly for capturing carbon dioxide (CO₂). In this work, a simple method that can be used to screen the suitable IL candidates was implemented in our modified gas–liquid membrane contactor system. Solubilities, selectivities of CO₂, nitrogen (N₂), and oxygen (O₂) gases in imidazolium-based ILs and its activity coefficients in water and monoethanolamine (MEA) were predicted using conductor-like screening model for real solvent (COSMO-RS) method over a wide range of temperature (298.15–348.15?K). Results from the analysis revealed that [emim] [NTf₂] IL is a good candidate for further absorption process attributed to its good hydrophobicity and CO₂/O₂ selectivity characteristics. While their miscibility with pure MEA was somehow higher, utilizing the aqueous phase of MEA would be beneficial in this stage. Data on absorption performances and selectivity of CO₂/O₂ are scarce especially in gas–liquid membrane contactor system. Therefore, considering [emim] [NTf₂] IL as a supporting material in supported ionic liquid membranes (SILMs), using aqueous phase of MEA as an absorbent would result in a great membrane-solvent combination system in furthering our gas–liquid membrane contactor process. In conclusion, COSMO-RS is a potentially great predictive utility to screen ILs for specified separation applications. In addition, this work provides useful results for the [emim] [NTf₂]-SILMs to be extensively applied in the field of CO₂ capture and selective O₂ removal.