Segmented copolymers with monodisperse crystallizable hard segments: Novel semi-crystalline materials

Segmented block copolymers with short monodisperse crystallizable hard segments have interesting structures and properties. In the melt, such short monodisperse segments are miscible with the matrix segments. Moreover, upon cooling, they crystallize fast, demonstrating a very high crystallinity, and only a small crystallization window is needed. The melting temperature of the short segments is high, provided that they can H-bond and/or contain aromatic groups. The melting temperature was found to decrease with increasing matrix segment concentration, due to the solvent effect of the matrix segments. At concentrations of crystallizable segment of 4-35 wt%, good dimensional and solvent stabilities were obtained.The monodisperse segments crystallized into nano-ribbons with uniform thickness and high aspect ratio, and these dispersed nano-ribbon crystallites constituted physical crosslinks, while acting also as reinforcing fillers. At concentrations of the monodisperse segments below 20 wt% no spherulitic ordering took place, and the semi-crystalline polymers were transparent. The monodisperse crystallizable segments can be used in combination with matrix segments of either low or high glass transition temperature, and may even contain (bio)functional units.     

Clogging of fibrous filters by liquid aerosol particles: Experimental and phenomenological modelling study

Fibrous filters are the most common means used to separate liquid aerosol particles from an industrial gas stream. The pressure drop and penetration (=1-efficiency) are the most important performance criteria of the filter. In this study, experimental and modelling results describing the pressure drop and penetration evolution of a glass microfibre HEPA filter are presented. For the experimental part, the pressure drop and penetration evolutions of a HEPA filter are described as well as the influence of the filtration velocity on those evolutions. For the modelling part, the physical collection mechanisms taken into account and their mathematical expressions which are the basis of the phenomenological model are described in a first step. After that the experimental values are compared to their modelled counterparts. Different efficiency models from the literature have been tested in order to determine the one closest to the experimental values. The influence of the filtration velocity on the model is studied in the last part. The model presented here is capable of describing the pressure drop and penetration evolution of a HEPA filter over the whole filtration period.     

Filtration of liquid aerosols with a horizontal fibrous filter

The aim of this study was to determine the filtration efficiency and pressure drop in liquid aerosol capture mechanisms using a fibrous coalescent filter. The experimental set-up was designed to measure filtration efficiency and pressure drop through the filter. To avoid the gravimetric effect, the filter was placed horizontally. A series of experiments highlighted the importance of operating conditions such as filtration velocity and aerosol concentration. The results demonstrated the advantage of working at high velocities to minimise the resistance of the medium and to enhance the mass efficiency of the coalescent filter. In parallel, no effect of aerosol concentrations in the pressure drop increase was noted.     

Loading characteristics of filter pretreated with anionic surfactant for monodisperse solid particles

Anionic surfactant (sodium oleate, SO) was used to pretreat polypropylene fibrous filters to make them negatively charged. This work examines the effects on particle loading of an anionic surfactant-pretreated filter. Also, the effects of various factors, such as the particle size, the face velocity, concentration of the surfactant, and particle distribution (mono and poly) on the particle loading characteristics were evaluated.Experimental data reveal that the electric field of a filter treated with anionic surfactant (SO) could be directly measured using an electrofieldmeter, suggesting that the pretreatment with surfactant charged the filters. The results demonstrate that pretreating the filter with SO surfactant increases its particle-loading capacity. The clogging points of the untreated filter, and of the 0.01, 0.05 and 0.08 M SO-pretreated filter are 18, 23, 28 and 33 g/m². The loading behavior of the SO-pretreated filter depended on the size of the particles and the operating face velocity. Additionally, the loading behavior of the SO-pretreated filter with polydisperse particles is much the same as that with monodisperse particles. However, the clogging point of the SO-pretreated filter with polydisperse particles is higher than that with monodisperse equal size.     

Experimental study of wet flue gas desulphurization with a novel type PCF device

Scrubbers are being widely used to remove the dust, sulphur dioxide and other harmful gases from coal-fired boilers. In this paper, a novel ‘wet-type’ desulphurization absorber, the PCF device (Chinese LOGO), was developed and studied through an experimental method. The mixture of air and SO₂ was used as simulated flue gas and CaCO₃-in-water suspension was used as absorbent. The results show that the PCF device has a good overall performance for FGD. Under moderate conditions employed, the content of SO₂ in outlet flue gas can achieve a level much lower than that permitted, while the pressure drop is very small due to co-flows in preliminarily treating chamber and no venturi structure in inlet tube. Guide plates and self-excitation chamber can improve the SO₂ removal efficiency by intensifying the mass-transfer and second purification. Some feasible process parameters are as follows: slurry pH value = 5.6-6.0, liquid-gas ratio = 8.7-10.4 L/m³, superficial gas velocity in inner cylinder = 3.5-4.5 m/s, and addition of Cl⁻ (in the form of CaCl₂) to the slurry (25 g/L) decreased the degree of SO₂ removal about 13.12%.     

Experimental study on effects of operating conditions and fuel quality on thermal efficiency and emission performance of a 300-MW boiler unit firing Thai lignite

This paper presents the results of an experimental study on a 300-MW boiler unit fired with Thai lignite. Effects of operating conditions (excess air ratio and unit load) and fuel quality on the boiler heat losses and thermal efficiency as well as on the gaseous (CO₂, CO, NO_x and SO₂) and particulate matter (PM) emissions from the boiler unit are discussed. The boiler thermal efficiency was weakly affected by the excess air ratio, unit load and fuel lower heating value, varying from 90.3 to 92.3% for wide ranges of the above variables. In all the tests, the NO_x, SO₂ and PM emissions were below the national emission standards for these pollutants. Quite low level of the SO₂ emission was secured by the high-efficiency flue gas desulphurization system. The CO emissions of rather small values were detected only at extremely low excess air ratios. The emission rate and specific emission (i.e. per MWh of electricity produced) for NO_x, SO₂ and CO were quantified using experimental emission concentrations of the pollutants. Meanwhile, the emission characteristics for CO₂ were determined with the use of fuel-C and fuel consumption by the boiler. In addition, the emission rate and specific emission for PM were estimated by taking into account the actual fuel-ash content and fuel consumption by the boiler, as well as the effects of SO₂ adsorption by fly ash in the boiler gas ducts and overall ash-collecting efficiency of the electrostatic precipitators and flue gas desulphurization system. Elevated CO₂ and NO_x emissions from the 300-MW boiler units firing Thai lignite are of great concern.     

Examination of acid-base properties of alumina treated with silane coupling agents, by using inverse gas chromatography

This study examined the specific component of the free energy of adsorption, − ΔG_A^SP, of the untreated and four types of silane coupling agent-treated alumina powders using inverse gas chromatography (IGC) by employing the adsorption of several polar and non-polar probes onto their surfaces at various temperatures. The acid-base properties of the untreated and surface-treated alumina powders were quantified using their K_A and K_D parameters, which reflect the ability of a surface to act as an electron acceptor and donor, respectively. The surface of the untreated alumina was found to be amphoteric and was able to function as both an electron acceptor and donor. The acid-base properties of the alumina surfaces treated with γ-glycidoxy propyl trimethoxy silane (GMS) and γ-amino propyl triethoxy silane (AES) were slightly basic, and those of the alumina surfaces treated with γ-methacryloxy propyl trimethoxy silane (MTMS) and γ-mercapto propyl trimethoxy silane (MCMS) were amphoteric.     

Thermal and kinetic study of manganese dithionate from absorbing or leaching solution via TG/XRD/IC analysis

ABSTRACT

Mangano-manganic oxide can be prepared through thermal decomposition of manganese sulfate from the absorption or leaching solution, so desulfurization by pyrolusite or leaching pyrolusite with sulfur dioxide should be fully exploited for the recovery of manganese salt. However, upon preparing MnSO₄ using above techniques, manganese dithionate is an inevitable by-product, which lowers the purity of the industrial raw material MnSO₄ and exerts negative influences on pyrolysis technology. Information regarding thermal decomposition of solid-state manganese dithionate is scarce. To recycle manganese dithionate efficiently, pyrolysis mechanism and kinetics were systematically investigated by thermal decomposition method. The characteristics of thermal decomposition products were determined by thermogravimetric analysis techniques (TG), X-ray diffraction (XRD), and Ion chromatography (IC). The experimental results revealed that both desulfurization and following dehydration of MnS₂O₆·H₂O were a one-step process, and the desulfurization occurred at about 150°C lower than the dehydration at 230°C. As increasing pyrolysis temperature to 900°C, the manganese sulfate was firstly formed, and to 1100°C, Mangano-manganic oxide was obtained by losing sulfur oxides. Consequently, the kinetic parameters for each decomposition steps of manganese dithionate were determined by the Coasts and Redfern (CR) integral method. The as-obtained experimental and kinetic results may provide theoretical guides for recycling manganese dithionate.     

Experimental and theoretical study on H2/CO2 separation by a five-step one-column psa process

An experimental and theoretical study is performed for bulk separation of H₂/CO₂ mixture (70/30 volume %) by PSA process with zeolite 5A, a process widely used commercially in conjunction with the catalytic steam reforming of natural gas or naphtha. For the optimized adsorption conditions of PSA, the characteristics of adsorption/desorption characteristics have been studied through breakthrough and desorption experiments under various conditions. The purge-to-feed ratio is important to the H₂ product purity only at a long adsorption step time. H₂ could be concentrated from 70% in the feed to 99.99% at H₂ recovery of 67.5%. The results of all five steps in PSA are successfully predicted by the LDF model considering an energy balance and nonlinear isotherm. For the model, the effective diffusivities (D,) are obtained separately from the uptake curves of H₂ and CO₂. The Langmuir-Freundlich isotherm is used to correlate the experimental equilibrium data and is very well fitted to the results.     

Very-high-performance concrete with ultrafine powders

The compactness and fluidity of binary and ternary compound paste systems containing ultrafine powders such as pulverized fly ash (PFA), pulverized granulated blast furnace slag (PS) and silica fume (SF) were quantitatively studied with the relative density (d/d₀) index. Through optimization of the proportions of compositions and applying heat treatment to specimens, a very-high-performance concrete (VHPC) including large quantities of ultrafine powders has been made successfully, which offers compressive strength up to 200 MPa. Two methods of overcoming the brittleness of VHPC were investigated.     

Self-propagating high-temperature synthesis of nano-TiCx particles with different shapes by using carbon nano-tube as C source

With using the carbon nano-tube (CNT) of high chemical activity, nano-TiC_x particles with different growth shapes were synthesized through the self-propagating high temperature in the 80 wt.% metal (Cu, Al, and Fe)-Ti-CNT systems. The growth shapes of the TiC_x particles are mainly octahedron in the Cu- and Al-Ti-CNT systems, while mainly cube- and sphere-like in the Fe-Ti-CNT system.     

Investigation of the rapid expansion of supercritical solution parameters effects on size and morphology of cephalexin particles

The particle size of organic and inorganic materials is vital parameter to determine its final use. Most of the newly developed pharmaceutical materials are poorly soluble or insoluble in the aqueous media such as biological fluids. Particle size reduction of such pharmaceuticals is one of the clues to improve the dissolution rate, adsorption and bioavailability. In this study, the effect of extraction and expansion parameters of the RESS process such as extraction temperature (313–333 K), extraction pressure (140–230 bar), effective nozzle diameter (450–1700 μm), nozzle length (2–15 mm) and spraying distance (1–7 cm) on the size and morphology of the precipitated particles of cephalexin were investigated. The morphology and particle size of the unprocessed and processed (precipitated) particles were examined by the SEM images. The mean particle size of the precipitated particles was between 0.86 and 7.22 μm depending upon the different experimental conditions used. The precipitated cephalexin particles were close to spherical form while the unprocessed particles were irregular or needle in shape.     

Effect of nano-Al2O3 particles on the corrosion behavior of alkyd based waterborne coatings

A modification in the alkyd based waterborne coatings was studied with the addition of 0.05%, 0.1%, 0.2%, and 0.3% nano-Al₂O₃. Corrosion performance of the nano-composite coatings were evaluated by applying these nanocomposites on mild steel substrate and exposing them to salt spray, humidity, and accelerated weathering. Mechanical properties were studied by subjecting the coating to scratch and abrasion test. The results showed that, with an increase in the concentration of nano-Al₂O₃ there was an improvement in the corrosion resistance, UV resistance, and mechanical properties of the coatings indicating the positive effect of addition of nano-Al₂O₃ particles in the coatings. Further, the transparency of the coating was not altered, maintaining the optical clarity of the coating.     

Experimental study of filterability behavior of model extracellular polymeric substance solutions in dead-end membrane filtration

A series of model extracellular polymeric substance (EPS) solutions was prepared by using sodium alginate, humic acid and some proteins on the basis of the components of actual EPS extracted from sludge for laboratory-scale SBR by the formaldehyde-NaOH method. The dead-end model filter of these solutions was carried out with 0.1 μm PVDF MF membrane under a transmembrane pressure of 0.1 MPa and the filterability behaviors of these solutions were also investigated. The experimental results showed that the filterability behaviors of BSA, β-lactoglobulin and lysozyme model solutions with five times the protein concentration in the actual EPS were similar with that of the actual EPS solution; in addition, the addition of sodium alginate and humic acid enhanced the rejection of proteins, and the values of α_c of model solutions increased with the addition of sodium alginate or humic acid, and especially the values of α_c of the model solution greatly increased with the addition of humic acid, and the presence of protein in the mixed components model solutions caused the decrease of the α_c values of sodium alginate.     

INFLUENCE OF K+ AND NA+ IONS ON DIRECT ELECTROSYNTHESIS OF SOLID K2FEO4 AND COMPARISON OF THE PHYSICOCHEMICAL PROPERTIES OF K2FEO4 SAMPLES

The influence of K⁺ and Na⁺ ions on the direct electrosynthesis of solid K₂FeO₄ was investigated in 14 M OH^? solutions. At 50 or 60°C, the maximum current efficiency of electrosynthesis is obtained in 9 M KOH +5 M NaOH solution. The maximum current efficiency of 64.9% is obtained at 60°C in 9 M KOH +5 M NaOH solution, similar to the maximum value of 63.9% at 70°C in 14 M KOH solution in the temperature ranges studied. The result shows that the temperature at which the maximum current efficiency is obtained in 9 M KOH +5 M NaOH is much lower than that in 14 M KOH. Solid K₂FeO₄ powders directly electrosynthesized in 9 M KOH +5 M NaOH and 14 M KOH solutions were characterized by Fourier transform-infrared spectrometry (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), and their electrochemical performance was investigated by means of galvanostatic discharge. The result shows that the two samples have similar physical properties and discharge performance.     

Rice husk co-firing with coal in a short-combustion-chamber fluidized-bed combustor (SFBC)

This study encompassed the characteristics and performance of co-firing rice husk, a by-product of rice-milling process, with coal in a short-combustion-chamber fluidized-bed combustor (SFBC). Bed phenomena investigated in a cold-flow model combustor showed that with the different mixes of materials, the anticipated offshoot of combustion, the minimum fluidizing velocity (U_mf) was 0.4-0.8 m/s. In concord with axial temperature profiles, axial gas concentration profiles implied that a recirculating ring was able to circumscribe CO within the short-main chamber. The formation, decomposition, and eventual maturity of NO_x characterized the NO_x evolution, inferred from concentration profiles. The impacts of fluidizing velocity and blending ratio on gas emissions and combustion efficiency (E_c) are described. The fluidizing velocity had consequential effect on gas emissions, except NO_x. Surprisingly, NO_x did not hinge much on increased N-content of the mixtures with coal. As expected, increased SO₂ was relevant to increased coal mass. Increased fluidizing velocity adversely affected E_c while increased coal fraction enhanced E_c, mostly >97%.     

Batch production of micron size particles from poly(ethylene glycol) using supercritical CO2 as a processing solvent

The major advantage of using supercritical carbon dioxide (CO₂) as a solvent in polymer processing is an enhancement in the free volume of a polymer due to dissolved CO₂, which causes a considerable reduction in the viscosity. This allows spraying the polymer melt at low temperatures to produce micron size particles. We have used supercritical CO₂ as a solvent for the generation of particles from poly(ethylene glycol) (PEG) of different molecular weights. Since PEG is a hydrophilic compound, it is a most commonly used polymer for encapsulating a drug. PEG particles with different properties may allow keeping a good control over the release of the drug. It has been possible to produce particles with different size, size distribution, porosity and shape by varying various process parameters such as molecular weight, temperature, pressure and nozzle diameter. A flow and a solidification model have been applied in order to have a theoretical insight into the role of different parameters.     

Synthesis of Silicon Dioxide Optical Films Mixed with Acrylic Series Monomers by Sol-gel Process

In this study, silicon dioxide (SiO₂) particles are mixed with acrylic series monomers (methyl metacrylate (MMA) and 2-hydroxyethyl methacrylate (2-HEMA)) by sol-gel process to prepare inorganic-organic hybrid materials for the optical film. The other optical film has the same composition and process as the above but tri(ethylene glycol) dimethacrylate (TEGDMA) is added.

An infrared spectrometer, differential scanning calorimeter, thermo gravimetric analysis, ultraviolet-visible spectrophotometer, and spectroscopic-ellipsometer have been used to explore the effect on optical, hardness, and thermal properties of the two series of thin films. TEGDMA used as a bonding resin in this study showed that not only a better hardness and thermal properties, but also maintain good optical properties in the SiO₂ hybrid materials by sol-gel process.     

Synthesis of α-Al2O3 platelets and kinetics study for thermal decomposition of its precursor in molten salt

The precursor, ammonium aluminum carbonate hydroxide (AACH) was synthesized via solid-state reaction at 60 °C. The experimental results show that the AACH is orthorhombic NH₄Al(OH)₂CO₃, and the calcined powder products are hexagonal platelets of α-Al₂O₃ which can be obtained from calcining AACH in molten salt at 1000 °C. The linear and nonlinear methods were used to calculate the activation energies of the thermal process of AACH. The calculated results indicated the decomposition process involved two stages which were single-step kinetic processes. The most probable reaction mechanisms of the two stages were estimated by two comparative methods. The values of pre-exponential factor A of the two stages were obtained on the basis of E_α and the reaction mechanisms.     

Observations of solid–liquid systems in anchor agitated vessels

Although process development is often done in well agitated vessels (e.g. with a retreat curve, pitched blade turbine etc.), there are a sizeable number of contract manufacturers’ still deploying a significant number of anchor agitated process units. For the purpose of observing the Zwietering constant value ‘S’ and few industrially important solid–liquid systems, we conducted extensive suspension experiments with anchor agitated vessels for varying D/T ratios (0.74 and 0.73). In this study, Zwietering's N_js (just suspension speed) and the corresponding ‘S’ factor were obtained for each system over a range of solid loadings. We found that the Zwietering constant was strongly dependent on the nature of the solid–liquid system; i.e. different systems had different ‘S’ values for the same geometrical configuration.