1,721,010 research outputs found
Microalgal cell disruption through Fenton reaction: Experiments, modeling and remarks on its effect on the extracted lipids composition
No full textA novel cell disruption technique, based on the use of Fenton reaction, for the improvement of lipid extraction from microalgae has been recently presented in the literature. In this work, a mathematical model is proposed to quantitatively interpret the relevant experimental results obtained so far. Model results and experimental data are successfully compared. Moreover, a mechanistic explanation of the relevant phenomena underlying the positive effects of disruption on the composition of fatty acids methyl esters, obtained through trans-esterification of the extracted lipids, is presented
Batch growth kinetics of Nannochloris eucaryotum and its cultivation in semi-batch photobioreactors under 100 %v/v CO2: Experimental and modeling analysis
No full textThe growth kinetics of Nannochloris eucaryotum in batch reactors is quantitatively investigated in this work with the purpose to obtain the main kinetic parameters needed to design photobioreactors for its cultivation at the industrial scale. Specifically, maximum growth rate, half saturation constants and yields coefficients for nitrates and phosphates, respectively, are determined by fitting the experimental data. The reliability of the obtained parameter values is then successfully tested by predicting further experimental data through the model. Finally, the effects resulting from the use of 100 % (v/v) CO2 gas as carbon source on the growth and lipid production are investigated
Mechanochemical Treatment of Soils Contaminated by Heavy Metals in Attritor and Impact Mills: Experiments and Modeling
Full text linkAn integrative approach was developed to support the scale-up from lab-into pilot-scale mechano-chemical reactors for immobilize heavy metals in contaminated mining soil
Cultivation of hydrocarbon-tolerant microalgae in flowback wastewaters produced during hydrofracking of impermeable rocks
Full text linkHuge amounts of Wastewaters (WWs) are produced yearly by the hydrofracking of impermeable rock formations for the extraction of oil or natural gas. Flowback Wastewaters (FWs) are characterized by high contents of inorganic contaminants and hydrocarbons thus representing a relevant threat for the environment. In this work three hydrocarbon-tolerant microalgae have been cultivated in flowback water generated during hydraulic fracturing to investigate their growth kinetics. All three strains could grow in FWs irrespective of the presence of oil hydrocarbons. Biomass productivity varied significantly among the strains. Ochromonas danica achieved a specific growth rate equal to 0.386 day-1 during the exponential phase and a maximum biomass productivity equal to 39 mg L-1 day-1 after 11 days of batch cultivation. Scenedesmus dimorphus was capable to grow in the FWs by achieving a biomass concentration equal to 0.5 g L-1 after about 25 days of cultivation. On the contrary, Prototheca zopfii was strongly affected by the contaminants of FWs. Ultimately, this study demonstrated that specific strains of microalgae could thrive in FWs and thus represent suitable candidates to future research activity aimed to verify the possibility to bio-remediate these harmful WWs
CO2 absorption in aqueous NH3 solutions: Novel dynamic modeling of experimental outcomes
Full text linkIt is well known that CO2 capture and re-use is one of the main challenges to be pursued in order to tackle global warming issues. Aqueous ammonia solutions are among the most promising sorbents for post-combustion CO2 capture and could represent a valid and potentially economical alternative to the use of conventional alkanolamines, due to their higher absorption capacity, lower energy requirements for sorbent regeneration and greater resistance to oxidative and thermal degradation. Despite its apparent simplicity and convenience, the dynamic evolution of CO2 − NH3 system needs to be further investigated through proper mathematical models that permit to design, optimize, and control the capture process. In this work, the chemical absorption of carbon dioxide contained in a simulated flue gas (N2+CO2; CO2 15%v/v) by means of aqueous NH3 solutions was investigated both experimentally and theoretically. In particular, a rigorous mathematical model, capable to quantify the CO2 capture efficiency dynamics and the sorbent chemical composition during the process, is proposed for the first time. The model is validated by comparing modeling results with experimental data obtained under different operating conditions. The effect of both operating temperature and sorbent concentration are investigated. The good agreement between model results and experimental data confirms the effectiveness and the reliability of the developed tool that turns out to be able to quantify the dynamics of capture efficiency during the variation of the operating conditions. Therefore, it may be exploited to properly design, optimize and control the capture process and the absorbent regeneration section whose energy requirements also depend on the species concentration into the absorbent solution
Behavior of the extremophile green alga Coccomyxa melkonianii SCCA 048 in terms of lipids production and morphology at different pH values
No full textThe extremophile green alga Coccomyxa melkonianii SCCA 048 was investigated to evaluate its ability to grow in culture media with different pH. Specifically, Coccomyxa melkonianii was sampled in the Rio Irvi river (Sardinia, Italy) which is severely polluted by heavy metals as a result of abandoned mining activities. In this study, the strain was cultivated in growth media where the pH was kept fixed at the values of 4.0, 6.8 and 8.0, respectively. During the investigation, a significant phenotypic plasticity of this strain was observed. The strain grew well in the pH range 4.0–8.0, while the optimal value for its growth was 6.8. Furthermore, maximum lipid contents of about 24 and 22 %wt were achieved at the end of cultivation when using pH 4.0 and 8.0, respectively. Finally, the analysis of fatty acid methyl esters (FAMEs) highlights the presence of suitable amounts of compounds which can be profitably exploited in the food, nutraceutical, and cosmetic industry. This aspect, coupled with the possibility of cultivating Coccomyxa melkonianii under extreme pH conditions in economic open ponds, makes this strain an interesting candidate for several biotechnological applications
Characterization of hypersaline Oklahoma native microalgae cultivated in flowback and produced water: growth profile and contaminant removal
No full textThis work explores the potential of three hypersaline native microalgae strains from Oklahoma, Geitlerinema carotinosum, Pseudanabaena sp., and Picochlorum oklahomensis, for simultaneous treatment of flowback (FW) and produced wastewater (PW) and the production of algal biomass. The quality of wastewater before and after treatment with these microalgae strains was evaluated and a characterization of algal biomass in terms of moisture, volatile matter, fixed carbon, and ash contents was assessed. The experimental results indicated how all the microalgae strains were able to grow in both FW and PW, revealing their potential for wastewater treatment. Although algal biomass production was limited by nutrient availability both in PW and FW, a maximum biomass concentration higher than 1.35 g L-1 were achieved by the three strains in two of the PWs and one of the FWs tested, with Pseudanabaena sp. reaching nearly 2 g L-1. Interestingly, higher specific growth rates were obtained by the two cyanobacteria strains G. carotinosum and Pseudanabaena sp. when cultivated in both PW and FW, compared to P. oklahomensis. The harvested algal biomass contained a significant amount of energy, even though it was significantly reduced by the very high salt content. The energy content fell within the recommended range of 16-17 MJ kg-1 for biomass as feedstock for biofuels. The algal treatment resulted in the complete removal of ammonia from the wastewater and a significant reduction in contaminants, such as nitrate, phosphate, boron, and micronutrients like zinc, manganese, and iron
A Multilinear Regression Procedure for Solving the Inverse Problem with Physics-Informed Neural Networks: Application to Three Case Studies in Chemical Engineering
No full textPhysics-Informed Neural Networks (PINNs) are gaining increasing interest in the field of modeling and simulation as they enhance the extrapolation ability of standard Neural Networks (NNs), which typically fail to predict system behavior beyond the experimental range. Integrating governing equations into the training algorithm leads to physics-driven networks capable of extrapolating system trends from limited training datasets. In this context, this work proposes an innovative approach that employs PINNs to solve inverse problems that arise when the parameters of the governing equations are unknown. Leveraging a multilinear regression procedure, the proposed method analytically computes model parameters during training without burdening the network’s parameter optimization and reducing the risk of getting stuck in local minima. Three case studies are considered for validation: (i) a continuous stirred tank reactor with proportional control, (ii) an autocatalytic process described with a Lotka–Volterra model, and (iii) a plug flow reactor with multiple reactions, which demonstrate the method’s effectiveness in predicting the system behavior and simultaneously identifying model parameters
Mathematical modeling of the effect of iron on the growth and the bio-oil productivity of chlorella vulgaris
No full textIt has been recently shown in the literature that specific strains of microalgae are capable to simultaneously increase their growth rate and lipid content when cultured under suitable concentrations of iron. A mathematical model describing the effect of iron on all the complex phenomena affecting growth rate and lipid accumulation of C. Vulgaris is proposed in this work. Model results are successfully compared with experimental data which confirm the positive effect of growing iron concentrations on lipid productivity of C. Vulgaris. © 2014, AIDIC Servizi S.r.l
A simplified ABS numerical model: Comparison with HIL and full scale experimental tests
No full textAntilock braking systems (ABS) have been introduced on all passenger cars in recent years. This electronic control system prevents wheels from locking-up and so improves braking performance while ensuring the steerability of the car.
Modeling the ABS is essential in order to simulate the vehicle behavior during braking and to achieve a good agreement between the vehicle model and the experimental data.
An hardware in the loop test bench has been realized to test an industrial ABS control unit, thus allowing the development of anumerical model of the antilock braking system.
Several braking simulations have been carried out to make acomparison between the implemented ABS model and the real antiskid system tested in the HILS platform.
Moreover, a validation of the model has been carried out, comparing the ABS model, integrated within a 14 d.o.f. vehicle model, and the experimental data collected on an instrumented passenger car during various kind of braking maneuvers
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