Effect of reactor geometry on the temperature distribution of hydrogen producing solar reactors

Global effects of greenhouse gas emissions associated with the current extensive use of fossil fuels are increasingly attracting research groups and industry to find a solution. In order to reduce or avoid such emissions, solar thermal cracking of natural gas has been studied by many research groups as a clean and economically viable option for hydrogen production with zero CO₂ emissions. By utilization of concentrated solar energy as the source of high temperature process heat, natural gas is decomposed into hydrogen gas and high grade carbon using a solar reactor. Our previous study shows that temperature distribution inside the solar reactor has significant effect on hydrogen production. In this paper, we expand our previous study by demonstrating that reactor geometry has a notable impact on temperature distribution inside the solar reactor and therefore it has an impact on natural gas to hydrogen conversion. Results show that there are approximately 22% and 32% losses from spherical and cylindrical reactors, respectively, while hydrogen production amount varies from 1.27 g/s to 8.95 g/s for spherical reactor, and 0.94 g/s to 8.94 g/s for cylindrical reactor geometry.     

A Comparative Study of Ascorbic Acid and Capsaicinoid Contents in Red Hot Peppers (Capsicum annum L.) Grown in Southeastern Anatolia Region

The aim of this study was to evaluate selected physico-chemical properties, ascorbic acid, and capsaicinoid (capsaicin, dihydrocapsaicin, norhydrocapsaicin, homodihydrocapsaicin, and total capsaicinoid) quantities of red hot pepper populations (Capsicum annum L.) grown in the South-Eastern Anatolia Region. Fresh and sun-dried red hot peppers and red hot pepper seed samples were collected from Kahramanmara?, pepper of Kahramanmara?; Gaziantep, pepper of Gaziantep; Kilis, pepper of Kilis; Diyarbak?r, pepper of Diyarbak?r; and ?anl?urfa, pepper of ?anl?urfa in the months of September through October 2010. The collected samples were analyzed in terms of certain quality parameters and capsaicinoid contents, while ascorbic acid amounts were determined only in fresh samples. All of the examined prameters were found to be significant statistically (P < 0.05). From the obtained results, it might be considered that these red hot pepper samples were suitable for cultivation due to their high-nutritional quality.     

Step-by-step methodology of developing a solar reactor for emission-free generation of hydrogen

This study presents a methodology to develop a solar reactor based on the thermodynamics and kinetics of methane decomposition to produce hydrogen with no emissions. The kinetic parameters were obtained in the literature for two cases; methane laden with carbon particles and methane without carbon particles. Results show that there is significant difference in experimentally obtained and theoretically predicted methane conversion. The paper also presents a parametric study on the effects of temperature, pressure and the influence of inert gas composition, which is fed along with methane, on the thermodynamics of methane decomposition. Results show that there is significant effect of the inert gas presence in the feeding gas mixture on the equilibrium of methane conversion and product gas composition. Results also show that higher conversions are obtained when the carbon particles laden with methane. The step-by-step reactor design methodology for homogenous methane decomposition and the parametric study results presented in this paper can provide a very useful tool in guiding a solar reactor design and optimization of process operating conditions.     

Hydrogen production via steam-methane reforming in a SOMBRERO fusion breeder with ceramic fuel particles

In the present study, hydrogen production potential of SOlid Moving BREeder ReactOr (SOMBRERO) fusion reactor and heat recovery of this system is investigated. The original SOMBRERO fusion reactor has a 1000 MWe KrF laser-driven IFE power plant. This reactors fusion power is 2677 MW and total thermal power is 2891 MW. The blanket is divided into three breeding zone and these breeding zones have different C, Li₂O and ceramic fuel particles. One-dimensional neutronic calculations of SOMBRERO fusion reactor have been performed by using XSDRNPM/SCALE4.4a neutron transport code. Steam Methane Reforming (SMR) method is used for large-scale hydrogen production and heat recovery of waste heat is analyzed. The numerical results show that the considered SOMBRERO fusion reactor has a good neutronic performance as well as the high hydrogen production potential with heat recovery of SMR process.     

Gentamicin loaded β‐tricalcium phosphate/gelatin composite microspheres as biodegradable bone fillers

In this study, novel composite bone fillers with microspherical shape, biodegradable property, and antibacterial effect were designed and prepared. Various fillers with different β‐tricalcium phosphate (β‐TCP)/gelatin (G)/glutaraldeyde (GA) compositions were loaded with a model antibiotic, gentamicin. The effect of composition and preparation conditions on the release of gentamicin was investigated in in vitro conditions. Complete release were observed in 12 h for pure β‐TCP powder, and this period was extended up to 96 h as the gelatin content increased in the microspheres. Morphological and chemical structures of the microspheres, before and after the release studies, were investigated by scanning electron microscopy and Fourier transform infrared, respectively. Antibacterial activities were examined against Escherichia coli by using disc diffusion method and promising results were obtained. It is proposed that these novel β‐TCP/G/GA microspheres can be applied locally to prevent and/or eliminate infection that might occur around a defected region of hard tissue and supports the healing process. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Hierarchical clustering analysis for the distribution of origanum-oil components in dense CO<Subscript>2</Subscript>

Hierarchical Clustering (HC) technique is demonstratively applied to analyze the distribution and classification of essential-oil components in oil and dense (subcritical/supercritical) CO₂ phases. For this purpose, relative-equilibrium-distribution data obtained for the 24 characteristic components of origanum-oil (Origanum Munituflorum) at 35, 45, 55 °C and 20–110 atm pressure range are used. With 24 components and 25 different pressure levels at three different temperatures, the total number of data points amounts to 600, which is large compared to other similar works, making the task of drawing of conclusions by visual inspection quite tedious. As demonstrated in this work, the use of HC technique facilitates the classification of the distribution of essential-oil components. HC-based classification analysis helps to reveal that the distributions of monoterpenes are the most sensitive to changes in temperature and pressure, and they are more soluble in CO₂ especially in the supercritical region. At 35 °C, at higher pressures, due to high solvent density/power, almost all components show similar distributions in the CO₂ and oil phases, indicating the loss of fractionation potential. Deterpenation by CO₂ is more favorable at higher temperatures. Cophnetic correlation shows the significance level of data clustering. HC analysis proved to be a useful tool in classification of the components and in determination of component clusters in the dense-gas and liquid phases.     

Poly(ε‐caprolactone) composite scaffolds loaded with gentamicin‐containing β‐tricalcium phosphate/gelatin microspheres for bone tissue engineering applications

In this study, novel poly(ε‐caprolactone) (PCL) composite scaffolds were prepared for bone tissue engineering applications, where gentamicin‐loaded β‐tricalcium phosphate (β‐TCP)/gelatin microspheres were added to PCL. The effects of the amount of β‐TCP/gelatin microspheres added to the PCL scaffold on various properties, such as the gentamicin release rate, biodegradability, morphology, mechanical strength, and pore size distribution, were investigated. A higher amount of filler caused a reduction in the mechanical properties and an increase in the pore size and led to a faster release of gentamicin. Human osteosarcoma cells (Saos‐2) were seeded on the prepared composite scaffolds, and the viability of cells having alkaline phosphatase (ALP) activity was observed for all of the scaffolds after 3 weeks of incubation. Cell proliferation and differentiation enhanced the mechanical strength of the scaffolds. Promising results were obtained for the development of bone cells on the prepared biocompatible, biodegradable, and antimicrobial composite scaffolds. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40110.     

Release of Acetazolamide from Swellable Hydroxypropylmethylcellulose Matrix Tablets

Controlled-release swellable tablets were prepared by a simple direct compression process using hydroxypropylmethylcellulose (HPMC) as the matrix former. The effects of the viscosity and concentration of the polymer and the pH of the dissolution medium on the release behavior of acetazolamide were investigated. The influence of the drug particle size was also evaluated. Ten, 15, 20, and 25% of two different viscosity grades of HPMC were dry mixed with acetazolamide, Fast Flo Lactose, and magnesium stearate, then directly compressed into tablets. The experimental tablets were tested for their drug contents, weight variations, and hardnesses. Dissolution tests were carried out under sink conditions at three different pH values: pH 1.2, 5.4, and 7.4. Release rate data were evaluated according to the equation log M/M_w = log k + n log t.     

Kinetic modeling of counterflow diffusion flames of butadiene

A comprehensive, semi-detailed kinetic scheme was used to simulate the chemical structures of counterflow diffusion and fuel-rich premixed 1,3-butadiene flames, to better understand the formation of polycyclic aromatic hydrocarbons (PAH). The results showed that model predictions were in good agreement with the experiments for most of the species in both the flames. In the counterflow flames higher-molecular weight products are slightly over predicted. The pathways characterizing the pollutant formation are very different in the premixed and in the counterflow flames confirming or suggesting the need to verify and refine the detailed mechanisms tuned for premixed conditions when they are extrapolated and used in diffusion flames. Reaction paths analysis for PAH formation in the counterflow flame shows that both the HACA mechanism and the resonantly stabilized radicals are important for the growth of PAH. The kinetic model was unsuccessful in predicting the increased reactivity in O₂-doped diffusion flames, indicating the need for improved models and also the opportunity of new experiments of butadiene oxidation in the intermediate temperature region.     

Alpha-tricalcium phosphate (α-TCP): solid state synthesis from different calcium precursors and the hydraulic reactivity

The effects of solid state synthesis process parameters and primary calcium precursor on the cement-type hydration efficiency (at 37°C) of α-tricalcium phosphate (Ca₃(PO₄)₂ or α-TCP) into hydroxyapatite (Ca_10−xHPO₄(PO₄)_6−x(OH)_2−x x = 0–1, or HAp) have been investigated. α-TCP was synthesized by firing of stoichiometric amount of calcium carbonate (CaCO₃) and monetite (CaHPO₄) at 1150–1350°C for 2 h. Three commercial grade CaCO₃ powders of different purity were used as the starting material and the resultant α-TCP products for all synthesis routes were compared in terms of the material properties and the reactivity. The reactant CaHPO₄ was also custom synthesized from the respective CaCO₃ source. A low firing temperature in the range of 1150–1350°C promoted formation of β-polymorph as a second phase in the resultant TCP. Meanwhile, higher firing temperatures resulted in phase pure α-TCP with poor hydraulic reactivity. The extension of firing operation also led to a decrease in the reactivity. It was found that identical synthesis history, morphology, particle size and crystallinity match between the α-TCPs produced from different CaCO₃ sources do not essentially culminate in products exhibiting similar hydraulic reactivity. The changes in reactivity are arising from differences in the trace amount of impurities found in the CaCO₃ precursors. In this regard, a correlation between the observed hydraulic reactivities and the impurity content of the CaCO₃ powders—as determined by inductively coupled plasma mass spectrometry—has been established. A high level of magnesium impurity in the CaCO₃ almost completely hampers the hydration of α-TCP. This impurity also favors formation of β- instead of α-polymorph in the product of TCP upon firing.