Nanoparticle evolution in flame spray pyrolysis—Process design via experimental and computational analysis

In flame spray pyrolysis (FSP), the evolution of metal oxide nanoparticles relies on quite a number of droplet (liquid) and vapor phase related physical mechanism as for instance precursor evaporation, oxidation, nucleation via gas-to-particle conversion mechanism, and subsequent particle (solid) growth mechanisms based on coagulation, sintering/coalescence, and agglomeration. The liquid precursor and dispersion oxygen feed rates are relevant control parameters of the FSP process for tailoring the nanoparticle size (diameter) and structure as well as the atomizer nozzle configuration. Sophisticated nonintrusive, laser-based in situ and ex situ diagnostics with multiscale spatial resolution (micrometer to meter range) are applied for analyzing droplet formation and size, gas velocity, temperature, species concentration, as well as primary and agglomerate diameters along the flow direction. Computational fluid dynamics (CFD) are coupled with population balance modeling (PBM) to elucidate the nanoparticle dynamics within the reactive spray. It is found that the CFD-PBM approach allows estimations of primary and agglomerate nanoparticle diameters within 80 and 75% accuracy compared to experimental data, suggesting that the methods presented could pave the way for designing next-generations of flame reactors.     

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.     

Role of the interlayer space of montmorillonite in hydrocarbon generation: An experimental study based on high temperature–pressure pyrolysis

The interlayer clay–organic complex is an important clay–organic association in sedimentary environments. However, the effects of organic matter storage in the interlayer space of clay minerals on the thermal degradation of organics and the generation of hydrocarbons have not been investigated. In this study, montmorillonite (Mt) and 12-amoniolauric acid (ALA) were used to prepare an interlayer Mt–ALA complex and a Mt–ALA complex in which Mt and ALA were simply mixed. Pyrolysis experiments on the ALA and Mt–ALA complexes were conducted in a confined gold capsule system at a fixed temperature and pressure of 350 °C and 36 MPa, respectively. X-ray diffraction, elemental analysis and Fourier transform infrared spectroscopy were used to characterize the Mt–ALA complexes, and automatically controlled gas chromatography along with a pyrolysis furnace was used to detect the volatile components released during pyrolysis. In the absence of Mt, the pyrolysis of ALA yielded only a small amount of C_1–5 hydrocarbons and CO₂. The amounts of C_1–5 hydrocarbons released from the pyrolysis of the interlayer Mt–ALA complex and the mixed Mt–ALA complex are approximately 43 and 5 times greater than the amounts released from ALA alone, respectively. The Brønsted acid sites in the interlayer space of Mt, which arise from the interlayer dissociated water, significantly promote the cracking of hydrocarbons through a carbocation mechanism, the isomerization of normal hydrocarbons and alkene–alkane conversion through hydrogenation, resulting in high i-alkane/n-alkane and alkene/alkane ratios in the pyrolysis products. The Lewis acid sites of Mt are primarily involved in the decarboxylation of ALA during pyrolysis and are responsible for CO₂ generation.     

Positioning “chemical product design” in the chemical engineering curricula in India

Chemical product design is concerned with the design of specialty products such as formulated products, specialty chemicals, etc. Chemical product design is becoming increasingly relevant to chemical engineers as chemical process industries (CPIs) are shifting away from the traditional commodity products to specialty products. In this article, the nature of the specialty product industry is discussed in detail. It is felt that this vital area is under-represented in Indian chemical engineering curricula and this has to be remedied immediately so that fresh chemical engineering graduates are able to adapt to the changing scenario. The teaching of chemical product design in other Universities abroad is considered and a discussion on our own experience at VIT University is provided.     

A discussion of the paper “Differential-scheme based dissolution diffusion model for calcium leaching in cement-based materials accounting for mix design and binder composition”

This paper presents a discussion on a recent article authored by Pichler et al. [Differential-scheme based dissolution diffusion model for calcium leaching in cement-based materials accounting for mix design and binder composition, Cem. Concr. Res. 42 (2012) 686–699].     

An emerging approach for the targeting analysis of dimethoate in olive oil: The role of molecularly imprinted polymers based on photo-iniferter induced “living” radical polymerization

This study concerns the first attempt to prepare molecularly imprinted polymers for the selective recognition of dimethoate using an iniferter polymerization technique (Inif-MIP). The synthesized polymers were fully characterized. SEM micrographs show a large accessibility to the binding sites with a significant improvement in MIP morphology. Inif-MIPs displayed high adsorption capacity (Q = 5.3 mg g⁻¹). The selectivity of this imprinting system was also assessed by means of cross-selectivity assays and the results obtained show that Inif-MIP displays a high selectivity for dimethoate, whereas some structural analogues (omethoate, malathion and methidathion) are poorly retained (6.3–28.7%) or not retained at all (fenthion). Inif-MISPE methodology was implemented by packing Inif-MIPs particles into a Solid Phase Extraction (SPE) cartridge and the loading, washing and eluting steps were optimized. The suitability of this sample preparation technique was demonstrated, as concentrations of dimethoate close to the tolerated maximum residue limits in the olive oil samples could be satisfactorily analyzed with good precision and accuracy. Some remarkable characteristics, like the sorbent reusability (at least 20 cycles without the lost of selectivity), low solvent consumption, reduced sample handling and, moreover higher recovery rates reaching 88% could be ascribed to the Inif-MISPE methodology.     

Measurement of the impurity gas pressure during combustion of a “gasless” system in a long cylindrical shell

A method for estimating the maximum impurity gas pressure averaged over the specimen cross section in the combustion wave for different cross sections of a long specimen is proposed. The impurity gas pressure in a given specimen cross section is understood as the gas pressure that induces cross-sectional fracture of the specimen enclosed into a shell and certain displacement along the shell of the pressed matter portion located ahead of the combustion wave front at the instant of fracture initiation. Special composite specimens are used to ensure constant conditions of impurity gas removal from the volume and to model the SHS process and associated impurity degassing in the case of long (L/d γ 1) cylindrical specimens under the condition L = const. The model mixtures are chosen to be typical compositions for SHS: Ti+C and Ti + 2B.     

Discussion of “Numerical simulation of moisture transport in concrete based on a pore size distribution model”

This paper presents a discussion on a recent article authored by Huang et al. [Numerical simulation of moisture transport in concrete based on a pore size distribution model, Cement and Concrete Research 67 (2015) 31–43].     

Statistical analysis of bacterial spore aerosols created by opening a spore containing “anthrax letter” in an office

This report provides a statistical analysis of a Bacillus atrophaeus spore aerosol generated by opening a spore containing letter in an office, simulating the effects of an “anthrax letter”. Spore aerosols were collected by five sets of high-resolution slit to agar samplers in a vacated office building (338.4 m², 1015.2 m³) during 34 replicates of a single control scenario. Results showed that 0.1 g of B. atrophaeus spores loaded in a letter were easily detected throughout the building following the opening of the letter. Areas under the curve (AUCs) were used to summarize each replicate scenario, and the variability of the AUCs was examined to assess the sample size requirements for future scenario analyses. Based on this analysis a minimum of five replicates of each scenario will be required for future statistical comparison of new scenarios intended to determine the effectiveness of existing or proposed anthrax letter response protocols.     

Reply to the comments on “Measurement of the temperature dependent diffusion coefficient of nanoparticles in the range of 295–600 K atmospheric pressure”

The diffusion coefficient of WO_x, Pt, and NaCl particles in the diameter range from 3 to 84 nm, determined from the penetration through a set of wire screens in the temperature range 295–600 K were recalculated with account for polydispersity of the used particles. Neglecting of polydispersity in Rudyak, Dubtsov, and Baklanov (2009) resulted in overestimation in the reported diffusion coefficient values by 10–15%. This difference, however, does not depend on the temperature in the range 300–600 K. However this decrease does not exceed the experimental error and, most importantly, the exponent of the T dependence remains almost unchanged.     

Reply to the discussion by Q. Zeng and S.L. Xu of the paper “Numerical simulation of moisture transport in concrete based on a pore size distribution model”

This paper presents a reply to the discussion of the paper “Numerical simulation of moisture transport in concrete based on a pore size distribution model” by Q. Zeng and S.L. Xu.     

Comment on “Measurements of the temperature dependent diffusion coefficient of nanoparticles in the range of 295–600 K at atmospheric pressure” by V.Y. Rudyak,S.N. Dubtsov,A.M. Baklanov

In a recent paper in this journal, Rudyak, Dubtsov, and Baklanov (2009) presented results of measurements of the penetration of nanoparticles with diameters from 3.5 to 84 nm at temperatures from ～300 to 600 K through a set of wire screens, from which they inferred diffusion coefficients. They argued that the formulation typically used for C, the Cunningham correction that accounts for non-continuum effects on the diffusion of nanoparticles, is not valid for temperatures greater than ～300 K, and they proposed a modification of this formulation which depends on both temperature and particle size. It is shown here that this modification produces unphysical results in that it yields negative values of the momentum accommodation coefficient. A likely reason for their results is that they used a polydisperse size distribution, for which the main contribution to the measured penetration would be from particles at sizes far from those attributed to them.     

Ceramic production and distribution in North-East Italy: Study of a possible trade network between Friuli Venezia Giulia and Veneto regions during the final Bronze Age and early Iron Age through analysis of peculiar “flared rim and flat lip” pottery

A particular type of pottery characterised by flaring rims and flat lips (FRFL ware) was widespread across the Friuli Venezia Giulia region in North-East Italy between the late Bronze Age and early Iron Age. A few of these jars have also been found occasionally in sites in the neighbouring Veneto region. Combined petrographic and chemical analyses were carried out on several shards from three settlements in the Veneto region, Concordia Sagittaria, Padova and Castion d'Erbè, in order to distinguish between local and imported varieties. Petrographic analysis revealed that local products and suspected imported artefacts of this type of pottery are compositionally different. The minero-petrographic composition of the FRFL potsherds is also uniform. Specifically, the presence of carbonate fragments with growing and saw teeth structures, showing alternation of growing white and dark-brown laminae, indicates the use of a similar temper, perhaps composed of concretions or speleothems. In addition, comparisons with a few shards from Friuli Venezia Giulia sites show considerable similarities. This evidence, together with the great diffusion and abundance of FRFL in Friuli Venezia Giulia, indicate that this ware originated from this region and was transported to the nearby Veneto.