Hasil untuk "Chemical industries"

Francesco Cenvinzo, Alberto Procacci, Alessandro Parente et al.

Despite advances in computing power, a major limitation in the simulation of turbulent flame stems from the need to track all chemical species involved in the thin reaction zones throughout the flow field. This paper investigates how Reduced Order Models (ROMs), combining data-driven analysis and neural network training, can significantly reduce computational cost. Specifically, neural networks are employed to assist in solving ϕ(x̲,t), a thermochemical scalar representing species mass fractions, energy, or temperature. The evolution of ϕ(x̲,t) over no time steps is used as input to a ROM framework, in which dimensionality reduction is achieved using Proper Orthogonal Decomposition (POD), while temporal dynamics are modeled using a Long Short-Term Memory (LSTM) network, with ANN trained for each of the retained POD modes. The scalar field for the nrom subsequent time steps is then predicted by the network, bypassing the need to solve the transport equation for these iterations. In this work the pair of values (no=10,nrom=1) and (no=20,nrom=5) are implemented. This approach is first validated on a non-reactive Large Eddy Simulation (LES) of a cavity flow, where air and H2 are injected separately and mix downstream. The methodology is then extended to a reactive Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulation of a non-premixed H2-air flame stabilized downstream of the same cavity geometry, assuming infinitely fast chemistry. When skipping CFD iterations, the network can also predict the flow evolution over a time step that is ten times larger than the standard CFD time step. This leads to a reduction in computational cost to reach a given physical time. Results demonstrate that the ROM is capable of accurately predicting the unsteady dynamics of the turbulent system across testing sequences unseen during training. The approach yields a CPU time saving of the order of 27%.

Guo Feng, Tiantian Liu, Jun Mu et al.

Novel Co and Cr free, high-temperature (Ni, Mn) co-doping CuFe5O8 black ceramic pigments were synthesized. The effects of mineralizer type and mineralizer amount on the synthesis and coloration of (Ni, Mn) co-doping CuFe5O8 pigments, as well as the effect of glazing calcination temperature on glaze coloration were systematically investigated using testing and characterization methods such as XRD, FE-SEM, TEM, EDS-mapping, HAADF and colorimeter. The results indicate that compared with H3BO3, NH4F, LiF and NaF mineralizers, the pigment with MgO as the mineralizer is relatively better. The optimized mineralizer MgO amount is 6.25 wt.% (mass ratio relative to the pigment). L*, a* and b* values of corresponding optimized pigment are 21.36, 1.10 and -0.24, respectively. The crystal phase of the pigment is CuFe5O8 (73–2314), and no diffraction peak of the heterophase is detected. The crystal size of the pigments is 0.8–1.5 μm with excellent dispersivity. The glazing temperatures have little effect on the coloration of the pigments when they are used at 1000 °C, 1150 °C and 1300 °C. The results show that the pigment has excellent high temperature resistance and is expected to be widely used in high-temperature glazing coloration.

Małgorzata Kupczewska-Dobecka, Katarzyna Konieczko, Joanna Jurewicz

1,1’-azodi(formamide) (azodicarbonamide – ADCA) is widely used as a blowing agent, a chemical substance designed to induce foaming processes. In Poland, ADCA is manufactured by a company specializing in the production of polyethylene foam bags and laminates used in various industries including home appliances, electronics, construction, furniture, automotive, and sports and leisure. The mechanism of action of ADCA involves thermal decomposition, resulting in nitrogen, carbon monoxide, as well as ammonia and carbon dioxide as the main gaseous decomposition products. These penetrate the polymer matrix, contributing to expansion and foaming properties. Most studies evaluating the relationship between occupational exposure and the development of allergic respiratory diseases focus on workers involved in ADCA production or its use as a blowing agent in plastics. The objective is to assess the respiratory sensitizing effects of ADCA in humans due to occupational exposure, based on literature data. The presented data confirm that long-term occupational exposure to ADCA can lead to persistent bronchial hyperreactivity symptoms in workers. 1,1’-azodi(formamide) can induce occupational asthma, with initial symptoms including nasal congestion, conjunctivitis, wheezing, and cough. Subsequently, symptoms such as chest tightness, dyspnea, and nocturnal cough attacks may appear, with a latency period of several years observed before symptom onset. In some cases, symptom progression was noted with continued ADCA exposure, while in others, exposure was discontinued after initial symptoms, preventing observation of symptom exacerbation. Prior exposure to allergens, such as working in bakeries, appears to accelerate symptom onset. Improvement in allergy symptoms has been noted during weekend breaks from work. There is no safe concentration identified for ADCA that would not result in adverse health effects for workers. A concentration of 0.036 mg/m 3 is considered the lowest observed adverse effect concentration, causing critical reduction in lung spirometric parameters. Med Pr Work Health Saf. 2024;75(5):455–473

Yensi Hariyanto, Siti Zulaikah, Cahyo Aji Hapsoro et al.

Critical minerals are an important natural resource that will continue to be necessary for modern industries. This study aims to determine the distribution of critical minerals based on geochemical data and magnetic susceptibility. Samples were taken from Lenggoksono beach, Southern Malang. The determination of chemical elements was conducted using X-ray fluorescence (XRF). Rare Earth Elements (REE) were identified using Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES). Magnetic susceptibility measurements were carried out using a Barrington Magnetic Susceptibility Meter (MS2B). The results showed that the dominant elements were Silica Oxide, SiO2 (70 Wt%), Iron Oxide, Fe2O3 (14.05 Wt%), and Calcium Oxide CaO (5.57 Wt%), which were categorized as critical minerals. The average REE elements detected were Cerium, Ce (6.75 mg/kg), Gadolinium, Gd (5.98 mg/kg), Neodymium, Nd (13.56 mg/kg), Praseodymium, Pr (6.62 mg/kg), Terbium, Tb (5.57 mg/kg), and Yttrium, Y (10.98 mg/kg). The magnetic susceptibility ranges from 13.27 to 4143.47 × 10-8m3/kg. Pearson’s Correlation analysis revealed a significant correlation between low-frequency magnetic susceptibility (ꭓlf) and high-frequency magnetic susceptibility (ꭓhf) with a significance level of 0.01. ꭓlf and ꭓhf also showed a significant correlation with Gd, with a correlation value of R² = 0.84 and a significance level of 0.05. These results indicate that the presence of one critical mineral can serve as a clue to the presence of other critical minerals, and magnetic susceptibility can be used as a proxy indicator for critical minerals in natural materials.

Chiara Molinari, Andreea Sima, Matteo Cavina et al.

Granite extraction waste represents an interesting alternative material for porcelain stoneware production, but information on its influence presents several gaps. For this reason, two different wastes were selected: a coarser iron-rich material from magnetic separation and a finer one from conveyance and abatement systems. Both were physically and chemically characterized. Batches were formulated by partial substitution of feldspar and technological behaviour of bodies was assessed by simulating the industrial manufacture at laboratory scale. Tiles were shaped by uniaxial pressure and fired by fast firing in electric roller kiln. The effect of waste addition was evaluated during the whole production process. Fired samples were characterized in terms of technological properties, mineralogical composition and microstructure evolution. The formulation optimization reduces firing temperature getting commercial technological constraints. A further increase of finer waste content affects compaction and mechanical strength. The presence of micaceous particles after the firing process may act as cracks initiation.

Wenhao Dou, Daxin Li, Bingzhu Wang et al.

To improve the oxidation resistance of short carbon fiber (Csf)-reinforced mechanically alloyed SiBCN (MA-SiBCN) (Csf/MA-SiBCN) composites, dense amorphous Csf/SiBCN composites containing both MA-SiBCN and polymer-derived ceramics SiBCN (PDCs-SiBCN) were prepared by repeated polymer infiltration and pyrolysis (PIP) of layered Csf/MA-SiBCN composites at 1100 °C, and the oxidation behavior and damage mechanism of the as-prepared Csf/SiBCN at 1300–1600 °C were compared and discussed with those of Csf/MA-SiBCN. The Csf/MA-SiBCN composites resist oxidation attack up to 1400 °C but fail at 1500 °C due to the collapse of the porous framework, while the PIP-densified Csf/SiBCN composites are resistant to static air up to 1600 °C. During oxidation, oxygen diffuses through preexisting pores and the pores left by oxidation of carbon fibers and pyrolytic carbon (PyC) to the interior of the matrix. Owing to the oxidative coupling effect of the MA-SiBCN and PDCs-SiBCN matrices, a relatively continuous and dense oxide layer is formed on the sample surface, and the interfacial region between the oxide layer and the matrix of the as-prepared composite contains an amorphous glassy structure mainly consisting of Si and O and an incompletely oxidized but partially crystallized matrix, which is primarily responsible for improving the oxidation resistance.

Ahmed E. Kholif

The experiment aimed to evaluate the effects of varying levels of <i>Laurus nobilis</i> leaves [0% (control), 0.5%, 1%, 1.5%, and 2%] on the in vitro ruminal fermentation of a ruminant diet consisting of a 50% concentrate mixture, 40% berseem hay (<i>Trifolium alexandrinum</i>), and 10% rice straw (<i>Oryza sativa</i>). The in vitro incubation lasted 48 h, during which gas production (GP), methane (CH₄), carbon dioxide (CO₂), total and individual short-chain fatty acids (SCFA), and nutrient degradability were measured. The experiment utilized a randomized block design and consisted of two incubation runs. Gas chromatography analysis revealed that 1,8-cineole (81%) was the primary volatile compound in the <i>L. nobilis</i> leaves. The 0.5% inclusion level exhibited the highest (linear, <i>p</i> = 0.006) asymptotic GP and lowest lag of GP (linear, <i>p</i> = 0.002), while the 2% inclusion level had the highest lag of GP. The 2% inclusion level significantly lowered CH₄ (linear, <i>p</i> = 0.003) compared to the control, and all levels of the leaves linearly decreased in the proportional CH₄ production (<i>p</i> = 0.001), with the lowest value at the 0.5% inclusion level. The highest asymptotic CO₂ production was observed with the 0.5% inclusion level (linear, <i>p</i> = 0.002), while the 0.5%, 1%, and 1.5% inclusion levels significantly increased (quadratic, <i>p</i> = 0.006) the proportion of CO₂ compared to the control. The 0.5% inclusion level showed the highest (<i>p</i> < 0.001) degradable DM and fiber fractions compared to the control, whereas the 2% level decreased them. The 0.5% inclusion level resulted in the highest (<i>p</i> < 0.01) production of total SCFA, acetate, and propionate. Additionally, the 0.5% inclusion level demonstrated the highest (<i>p</i> < 0.05) metabolizable energy and microbial crude protein, while the 2% level reduced these measures compared to the control. It is concluded that <i>L. nobilis</i> leaves can be included at 0.5% of the ruminant diet (e.g., sheep) to improve ruminal fermentation and reduce CH₄ production.

Floriana Boscaino, Elena Ionata, Salvatore De Caro et al.

Non-conventional yeasts (NCYs) (i.e., non-<i>Saccharomyces</i>) are used as alternative starters to promote aroma complexity of fermented foods (e.g., bakery products). A total of 66 yeasts isolated from artisanal food matrices (bread and pizza sourdoughs and milk whey) from different geographical areas of the Campania region (Italy) were screened for physiological and technological characteristics such as leavening ability, resistance to NaCl and pH, exopolysaccharide and phytase activity production, and carbohydrate assimilation. Selected and isolated microorganisms were also used to study the leavening kinetics in experimental doughs as mixed inocula of two different strains. Volatile organic compounds (VOCs) of the inoculated doughs were analyzed with solid-phase microextraction/gas chromatography–mass spectrometry (SPME/GC-MS). Most of the strains belonged to non-<i>Saccharomyces</i> species (<i>Pichia kudriavzevii</i>, <i>Kluyveromyces marxianus</i>) and <i>Saccharomyces</i> (<i>S. cerevisiae</i>). Several strains produced exopolysaccharides (EPSs), that are important for dough rheological properties. Moreover, yeasts isolated from whey showed extracellular phytase activity. The mixed starter culture of the <i>S. cerevisiae</i> and NCY strains showed a synergic effect that enhanced the doughs’ aroma complexity. The use of non-conventional yeasts mixed with <i>S. cerevisiae</i> strains can be advantageous in the bakery industry because they improve the bread aroma profiles and nutritional properties by bioactive molecule production.

John Samelis, Charikleia Tsanasidou, Loulouda Bosnea et al.

The performance of a mixed thermophilic and mesophilic starter culture consisting of <i>Streptococcus thermophilus</i> ST1 and the Greek indigenous nisin-A-producing <i>Lactococcus lactis</i> subsp. <i>cremoris</i> M78 was evaluated in the absence (A: ST1+M78) or presence (B: ST1+M78+H25) of <i>Lactiplantibacillus plantarum</i> H25—another indigenous ripening strain—under real cheesemaking conditions. Three pilot-scale trials of fresh (6-day-old) Galotyri PDO cheese were made from boiled milk by an artisanal method using simple equipment, followed by cold ripening of the A1–A3 and B1–B3 cheeses at 4 °C for 30 days. All of the cheeses were analyzed microbiologically and for pH, gross composition, proteolysis, sugar and organic acid contents, and sensorial attributes before and after ripening. The artisanal (PDO) Galotyri manufacturing method did not ensure optimal growth of the ST1+M78 starter as regards the constant ability of the thermophilic strain ST1 to act as the primary milk acidifier under ambient (20–30 °C) fermentation conditions. Consequently, major trial-dependent microbial and biochemical differences between the Acheeses, and generally extended to the Bcheeses, were found. However, high-quality Galotyri was produced when either starter strain predominated in the fresh cheeses; only trial A1 had microbiological and sensory defects due to an outgrowth of post-thermal Gram-negative bacterial contaminants in the acidified curd. The H25 adjunct strain, which grew above 7 to 9 log CFU/g depending on the trial, had minor effects on the cheese’s pH, gross composition, and proteolysis, but it improved the texture, flavor, and the bacteriological quality of the Bcheeses during processing, and it exerted antifungal effects in the ripened cheeses.

Jixiang Zhang, Xiaolei Zhang, Athanasios Rentizelas et al.

Biofuel large-scale application was constrained due to cost control. In order to reduce biofuel production cost and increase profitability, long-term strategy (strategic) and medium-term strategy (tactical) combined logistic model were assessed in this study. Geographic information system has been integrated into logistic model to minimize the effect of uncertainty on logistic modelling accuracy, with aims of transferring uncertainty problem to be certain. Combined heat and power generation plant as a case study present in logistic model, which provide a method in plant location and capacity selection criteria; logistic model design; and interaction between logistic model and local conditions. The logistic plan with compression as a pre-treatment technology has the optimal profitability performance, their properties affect the selection of the transport route, especially optimal for a lower availability of agricultural residues. With increased availability, torrefaction turns to more efficiency biomass pre-treatment technology due to storage cost significant reduction. With geographic information system transportation route assistance, logistic model transportation cost and CO2 emission has a 0.02% and 0.01% reduction.

Azusa Oita, Kiwamu Katagiri, Tetsuya Eguchi et al.

Agro-food systems require nutrient input from several sources to provide food products and food-related services. Many of the nutrients are lost to the environment during supply chains, potentially threatening human and ecosystem health. Countries therefore need to reduce their nutrient/nitrogen footprints. These footprints are importantly affected by links between sectors. However, existing assessments omit the links between sectors, especially between the agriculture, manufacturing, and energy sectors. We propose a novel approach called the nutrient-extended input–output (NutrIO) method to determine the nutrient footprint as a sum of direct and indirect inputs throughout the supply chains from different sources of nutrients. The NutrIO method is based on a nutrient-based material flow analysis linked to economic transactions. Applying this method, we estimated the nitrogen footprint of Japan in 2011 at 21.8 kg-N capita ^−1 yr ^−1 : 9.7 kg-N capita ^−1 yr ^−1 sourced from new nitrogen for agriculture and fisheries, 7.0 kg-N capita ^−1 yr ^−1 from recycled nitrogen as organic fertilizers, and 5.1 kg-N capita ^−1 yr ^−1 from industrial nitrogen for chemical industries other than fertilizers. A further annexed 55.4 kg-N capita ^−1 yr ^−1 of unintended nitrogen input was sourced from fossil fuels for energy production. The nitrogen intensity of the wheat and barley cultivation sector, at 1.50 kg-N per thousand Japanese yen (JPY) production, was much higher than that of the 0.12 kg-N per thousand JPY production for the rice cultivation sector. Industrial nitrogen accounted for 2%–7% of the nitrogen footprint of each major food-related sector. The NutrIO nitrogen footprint sourced from new nitrogen for agriculture and fisheries, at 8.6 kg-N capita ^−1 yr ^−1 for domestic final products, is comparable to the food nitrogen footprint calculated by other methods, at 8.5–10.5 kg-N capita ^−1 yr ^−1 . The NutrIO method provides quantitative insights for all stakeholders of food consumption and production to improve the nutrient use efficiencies of agro-food supply chains.

R. Ellis, M. Cochrane, M. Dale et al.

F. Abbasi, H. Mirzadeh, A. Katbab

Raymond H. Myers, A. I. Khuri, Walter H. Carter et al.

M. Haruta

P. Duboc, B. Mollet

D. Dodds, R. Gross

Mohammad Ghashghaee, Mehdi Ghambarian

Theoretical assessment of the protonation reaction in the activation of propene on hydroxylated Mo(VI) and W(VI) metathesis catalysts is presented in this paper using the density functional theory calculations and five support clusters varying from simple SiO4H3 clusters to a large Si4O13H9 cluster. The bond distances and thermochemical data were similar for most of the clusters. The formation of isopropoxide was more favorable than a propoxide counterpart bonded via the primary carbon atom, with the Gibbs free energies of –3.73 and –7.78 kcal/mol, respectively, for the W catalyst. Overall, the 1T cluster models with optimized H atoms or an all-relaxed alternative would be considered appropriate replacements for a larger 4T cluster model saturated with OH groups and optimized terminal hydrogen atoms. The largest deviations in the energetic data were observed between the protonated structures formed on the two larger clusters saturated with either OH or H groups.

Navaratnarajah Kuganathan, Alexander Chroneos

Technetium (⁹⁹Tc) is an important long-lived radionuclide released from various activities including nuclear waste processing, nuclear accidents and atmospheric nuclear weapon testing. The removal of ⁹⁹Tc from the environment is a challenging task, and chemical capture by stable ceramic host systems is an efficient strategy to minimise the hazard. Here we use density functional theory with dispersion correction (DFT+D) to examine the capability of the porous inorganic framework material C12A7 that can be used as a filter material in different places such as industries and nuclear power stations to encapsulate Tc in the form of atoms and dimers. The present study shows that both the stoichiometric and electride forms of C12A7 strongly encapsulate a single Tc atom. The electride form exhibits a significant enhancement in the encapsulation. Although the second Tc encapsulation is also energetically favourable in both forms, the two Tc atoms prefer to aggregate, forming a dimer.