Dicalcium silicate (2CaO·SiO2) synthesized through flame spray pyrolysis and solution combustion synthesis methods

Synthesis of dicalcium silicate (2CaO.SiO₂ or C₂S) through flame spray pyrolysis and a solution combustion method was investigated by the variation of flames and fuels. The synthesized powders were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). X-ray diffraction analysis revealed the formation of dicalcium silicate polymorphs with presence of calcium oxide, calcium carbonates and amorphous materials as impurities. Results suggest that some flames and fuels favor the formation of calcite during the synthesis process due to an excess of carbon atoms in the combustion. Fourier transform infrared spectra of all samples showed the main silicates reflections located near to 500?cm^?1 and 1000?cm^?1 and scanning electron microscopy showed the formation of spherical agglomerates of nanoparticles in both methods. By these two alternative methods of synthesis it was possible to obtain C₂S with nanometric particle size.     

“D-optimal experimental design” analysis in preparing optimal polyisobutylene based pressure sensitive adhesives

The aim of this work was to model the mechanical properties of different blends of polyisobutylene (PIB) pressure sensitive adhesives (PSAs) with different molecular weights (36,000, 51,000, 75,000, 400,000, and 1,100,000). The mechanical properties of PSAs are usually described by tack, peel, and shear strength which are strongly depended on the bulk viscoelastic properties of the adhesive system. It is assumed that the blends of high and low molecular weight PIB could affect these properties. According to D-optimal design of Design Expert software, various blends of five different molecular weights of PIB have been selected for study in this investigation. Using manual regression analysis, the quadratic model generated for three responses (tack, peel, and shear) was found to be statistically significant (p < 0.05). It was found that tack increases with decreasing molecular weight. It was also found that the presence of B10 and B12 as low molecular weight polymers and B50 as a high molecular weight polymer in increasing peel strength was more dominant compared with B15 and B100. Furthermore, shear strength was found to increase with an increasing concentration of the low molecular weight PIB, B15. The results have shown that statistical analysis meets theoretical expectations and they suggest desired blends of polymer for different aims.     

Practical identifiability analysis in dynamic gas–liquid reactors: Optimal experimental design for mass-transfer parameters determination

A dynamic gas–liquid transfer model without chemical reaction based on the unsteady film theory is analysed in order to confirm the possible identifiable parameters of the model from a given set of experimental data. The structural identifiability analysis of the model using the macroscopic concentrations at the gas and liquid phase shows that the identifiable parameters of the model are the gas hold-up, ?, the Henry's constant, H, the reciprocal of the diffusion time, D/δ², and the volumetric mass-transfer coefficient, k_La. A procedure for the optimal experimental design is proposed based on the analysis of the Fisher information matrix of the model. The analysis concludes that the measure of the dynamics of the concentration just in the liquid phase leads to important systematic errors in the determination of k_La. The importance of the concentration measurement simultaneously in the gas and the liquid phase for the parameter estimation is demonstrated and discussed.     

Advancements in traditional and nanosized flame retardants for polymers—A review

Synthetic polymers are ubiquitous materials widely used in construction, automotive, electronics, and countless commercial products. With the growing trend of polymer applications in everyday life, upholding the rigorous fire safety regulations has become a matter of concern. In this regard, numerous studies have been conducted for improving the fire retardancy of polymers, mainly through incorporating a diverse group of fire-retardant compounds into polymer-based composites. This review article aims to present a comprehensive overview of recent advances in the fire-retardant categories for polymeric materials especially emphasizing the nanosized fire retardants. Along with an attempt to focus attention on the consumption of conventional and possibly harmful fire retardants, potential eco-friendly alternatives are represented. A detailed discussion on the flame retardation mechanisms and conventional fire characterization techniques are also discussed.     

Economic analysis in product design——A case study of a TCM dietary supplement

An approach for the economic analysis of chemical product design is proposed. It takes into account of customers' preference on product quality and economic considerations such as pricing, profit, market share, capital investment, and operating cost. The activities needed to support business decision making – identifying product quality, estimating product cost, calculating financial metrics, and performing make–buy analysis – are discussed.The design of a Ganoderma lucidum dietary supplement, a traditional Chinese medicinal(TCM) product, is used to illustrate all the activities in this approach.     

Synthesis and process modeling of mesoporous γ-Al2O3 granules using the biopolymer chitosan via experimental design

In this study, biopolymer chitosan is presented as a template for synthesizing and shaping the mesoporous γ-Al₂O₃ macrospheres. This porous γ-Al₂O₃ granule has a high surface area (310 m²/g), high pore volume (.6148 cm³/g), and pore diameter between 2 and 10 nm. The full factorial design based on a mathematical model was implemented to study the acid concentration, chitosan amount, ammonia concentration, and aging time affecting the responses (Brunauer–Emmett–Teller surface area and pore volume). Predicted responses were found to be in satisfactory agreement with experimental values (R² = .9580 and .9109, respectively). The adequacy of the model was examined by analyzing the residual distribution plots and Pareto graph. X-ray diffraction, scanning electron microscopy (SEM), thermogravimetric analysis, and N₂ adsorption/desorption techniques are employed to characterize the structure of the prepared γ-alumina sample.     

TG–DSC analysis of straw biomass pyrolysis and release characteristics of noncondensable gas in a fixed-bed reactor

Under the double pressures caused by the energy shortage and environmental damage, to exploit the agricultural wastes and convert into available clean fuels are becoming more and more urgent in modern society. The aim of learning the pyrolysis characteristics of soybean straw and corn straw, the nonisothermal thermogravimetry and differential scanning calorimetry (TG-DSC) method was used in this work. The results showed that both of biomass feedstocks all underwent four different pyrolysis stages, with the increase in heating rate, the peak temperature shifted toward the high-temperature interval, and that the yield of bio-char also increased correspondingly; potassium had an influence on the thermal cracking of biomass, and that the existence form of potassium and impregnation increment of sylvite would result in the yield of bio-char was distinct. In addition, temperature and catalyst had a significant impact on the gaseous products of biomass pyrolysis. Increasing the pyrolysis temperature could enhance the yield of CO and H₂ and CH₄ content reached the maximum at 600°C. For both of the biomass, sylvite had a negative effect on the formation of CH₄, and H₂ content of soybean straw reached a maximum with 5% K₂CO₃ and corn straw with 5% KCl.     

SustainPro—A tool for systematic process analysis,generation and evaluation of sustainable design alternatives

Chemical processes are continuously facing challenges from the demands of the global market related to economics, environment and social issues. This paper presents the development of a software tool (SustainPro) and its application to chemical processes operating in batch or continuous modes. The software tool is based on the implementation of an extended systematic methodology for sustainable process design (Carvalho et al., 2008, Carvalho et al., 2009). Using process information/data such as the process flowsheet, the associated mass/energy balance data and the cost data, SustainPro guides the user through the necessary steps according to work-flow of the implemented methodology. At the end the design alternatives, are evaluated using environmental impact assessment tools and safety indices. The extended features of the methodology incorporate life cycle assessment analysis and economic analysis. The application and the main features of SustainPro are illustrated through a case study of β-galactosidase production.     

Classification of Magnetic Nanoparticle Systems—Synthesis,Standardization and Analysis Methods in the NanoMag Project

This study presents classification of different magnetic single- and multi-core particle systems using their measured dynamic magnetic properties together with their nanocrystal and particle sizes. The dynamic magnetic properties are measured with AC (dynamical) susceptometry and magnetorelaxometry and the size parameters are determined from electron microscopy and dynamic light scattering. Using these methods, we also show that the nanocrystal size and particle morphology determines the dynamic magnetic properties for both single- and multi-core particles. The presented results are obtained from the four year EU NMP FP7 project, NanoMag, which is focused on standardization of analysis methods for magnetic nanoparticles.     

On the measurement of local gas hold-up and interfacial area in gas–liquid contactors via light sheet and image analysis

Particle image velocimetry techniques coupled with advanced image processing tools are receiving an increasing interest for measuring flow quantities and local bubble-size distributions in gas–liquid contactors.Aim of this work is that of providing a numerical procedure able to reconstruct local gas hold-up and specific interfacial area from images obtained by laser sheet illumination. A correction for measured quantities accounting for laser sheet thickness is proposed and tested by means of Monte Carlo simulations. The algorithms proposed are robust and independent of any measured parameters of the actual bubble size distribution.     

On the measurement of bubble size distribution in gas–liquid contactors via light sheet and image analysis

Particle image velocimetry techniques coupled with advanced image processing tools are receiving an increasing interest for measuring flow quantities and local bubble-size distributions in gas–liquid mechanically agitated vessels.When trying to analyze image information the problem arises that bubble sizes are generally underestimated, due to the fact that the laser sheet used for lighting the system randomly cuts bubbles over non-diametrical planes, leading to an apparent bubble size distribution even in the ideal case of single sized bubbles. Clearly in the case of bubbles with a size distribution the experimental information obtained is affected by the superposition of effects.Aim of this work is that of providing a numerical procedure able to reconstruct actual bubble size distributions from relevant apparent size distributions obtained by laser sheet illumination and image analysis. The procedure proposed is robust and viable and can account for laser sheet thickness. The procedure is shown to provide fully satisfactory results even with quite extreme distributions. BSD resolution dependence on the numerousness of raw data processed is discussed. Use of the proposed procedure for extracting BSD from bubble chord raw data obtained by other devices, such as point probes, is straightforward.     

The aerobic and peroxide-induced coupling of aqueous thiols—II. Reaction mechanisms,model analysis,and a comparison of the model and experimental results

Kinetic results of the preceeding paper are used to formulate the most probable reaction mechanisms for the peroxide-induced and aerobic coupling of aqueous thiols. Parameters in the proposed mechanisms are evaluated for n-propylthiol using the results of independent measurements. A remarkably good agreement is achieved between the model and experimental results.The peroxide reaction, which is not affected by either copper ion or radical scavengers, is shown to be a nucleophilic substitution (S_N 2) reaction which proceeds by a two-step mechanism as follows: RS⁻ + H₂O₂

RSOH + OH⁻ rate-determining RS⁻ + RSOH → RSSR + OH⁻ In the reaction the thiolate anion acts as the nucleophile while hydrogen peroxide and the transient sulfenic acid, RSOH, function as electrophiles.The most plausible mechanism for the copper-catalyzed, aerobic coupling reaction is as follows: Cu⁺ (RSSR)₂⁺ + RS⁻

(RSSR)Cu⁺ (RS⁻) + RSSR (RSSR)Cu⁺ (RS⁻) + RS⁻

(RSSR)Cu⁺ (RS⁻)₂⁻ (RSSR)Cu⁺ (RS⁻)₂⁻ + O₂

Cu⁺(RSSR)₂⁺ + HO₂⁻ rate-determining RS⁻ + H₂O₂

RSOH + OH⁻ rate-determining RS⁻ + RSOH → RSSR + OH⁻ For the n-propylthiol substrate, the pertinent parameters in the mechanism are 1n (K₁) = −11,000 K/T + 33.6, where K₁ is dimensionless, 1n (K₂) = 4270 K/T −10.5, where K₂ is in 1/mol, 1n (k₂) = 30.0 − 5260 K/T, and 1n (k₂) = 26.8 − 6190 K/T, where k₁ and k₂ are in 1/(mol min).     

Measurement and analysis of particle—particle interaction in a cocurrent flow of particles in a dilute gas—solid system

The experimental apparatus of Arastoopour et al.[3] was modified to measure pressure drop and solid velocities for cocurrent flow of particles in a pneumatic conveying line. The data were translated into particle—particle interaction expression using a force balance over the particles. The particle interaction is a combination of collision and drag force in a particles low relative velocity region. A correlation for particle—particle interaction with relative velocity between the particles of 0.3–4.6 m/s has been developed. The correlation describes our experimental data within the 10% deviation.     

Steady-state polarization response of chloride-induced macrocell corrosion systems in steel reinforced concrete — numerical and experimental investigations

Chloride-induced macrocell corrosion of steel is recognized as a frequent and harmful problem affecting reinforced concrete structures. For this specific corrosion mechanism, anodic and cathodic areas at steel-concrete interface are spatially separated. Thereby, at equilibrium, anodic and cathodic potentials are different due to electrical resistivity of concrete, which means there is a potential gradient and a macrocell corrosion current flowing in the concrete volume. Despite some available works on electrochemical modelling of free macrocell corrosion systems in reinforced concrete, the literature is very scarce regarding the response of such systems under polarization. Due to this lack of knowledge, the assessment of steel corrosion rate in reinforced concrete is still commonly based on the uniform corrosion assumption. In this paper, the detailed polarization response of the different components of macrocell systems is studied in steady-state condition on the basis of numerical simulations and the qualitative conclusions are validated by original experiments. Some important results are achieved, with potentially major consequences regarding the non-destructive evaluation of steel corrosion in reinforced concrete. In particular, the distribution of the polarizing current in the macrocell system is found to be dependent on the polarization nature (anodic or cathodic) and magnitude. Moreover, in case of chloride-induced macrocell systems, the apparent linear polarization range is actually much higher than usually assumed and significant differences are observed between anodic and cathodic responses.     

Hydrodynamics of three-phase fluidization of homogeneous ternary mixture in a conical conduit——Experimental and statistical analysis

Hydrodynamics of conical fluidized bed differ from that of columnar beds by the fact that a velocity gradient exists along the axial direction of the bed.The gas–liquid–solid fluidized bed has emerged in recent years as one of the most promising devices for three-phase operations.Such a device is of considerable industrial importance as evident from its wide applications in chemical,refining,petrochemical,biochemical processing,pharmaceutical and food industries.To explore this,a series of experiments have been carried out for homogeneous well-mixed ternary mixtures of dolomite of varying compositions in a three-phase conical fluidized bed.The hydrodynamic characteristics determined included the bed pressure drop,bed fluctuation and bed expansion ratios.The single and combined effects of operating parameters such as superficial gas velocity,superficial liquid velocity,initial static bed height,average particle size and cone angle on the responses have been analyzed using response surface methodology(RSM).A 25 full factorial central composite experimental design has been employed.Analysis of variance(ANOVA) showed a high coefficient of determination value and satisfactory prediction second-order regression models have been derived.Experimental values of bed pressure drop,bed fluctuation and bed expansion ratios have been found to agree well with the developed correlations.     

An effect of the impeller eccentricity on the process characteristics in an agitated vessel—experimental and numerical modeling

An effect of the impeller eccentricity on the process characteristics in an agitated vessel was analyzed on the basis of our own experimental and numerical results obtained within the turbulent range of the Newtonian liquid flow. Mixing time, power consumption, local and mean values of the heat transfer coefficients and distributions of the transport coefficients (shear rate and friction coefficient) at the vicinity of the vessel wall were studied experimentally within the wide range of the operating and geometrical parameters of the agitated vessel equipped with eccentrically located high-speed impeller. Numerical simulations of hydrodynamics in an agitated vessel with eccentrically located axial flow impeller (up-pumping propeller or downpumping HE-3 impeller) were carried out using CFD method.