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Processes, Volume 9, Issue 3 (March 2021) – 165 articles

Cover Story (view full-size image): To accelerate the precipitation towards autonomous operation, the integration of real-time release testing is essential to implement a suitable process control. Therefore, the feasibility of online measurement techniques including Raman, FTIR, DAD, and fluorescence is demonstrated as PAT technology. To apply the online measured data to the process, a process model (digital twin) must be developed to pave the way for processing feedback-control. With the aid of the model and the online measurement of critical quality attributes (CQAs), the monitoring of process can be conducted, as well as the optimization of operation. In this way autonomous operation becomes feasible. View this paper
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22 pages, 3218 KiB  
Article
Effects of Swirl and Boiling Heat Transfer on the Performance Enhancement and Emission Reduction for a Medium Diesel Engine Fueled with Biodiesel
Processes 2021, 9(3), 568; https://doi.org/10.3390/pr9030568 - 23 Mar 2021
Cited by 54 | Viewed by 3110
Abstract
In order to improve the accuracy of numerical simulation, a new heat transfer model is developed by using a modular approach in the Anstalt für Verbrennungskraftmaschinen (AVL)-Boost software. The improved heat transfer model mainly considers the effects of the swirl and boiling heat [...] Read more.
In order to improve the accuracy of numerical simulation, a new heat transfer model is developed by using a modular approach in the Anstalt für Verbrennungskraftmaschinen (AVL)-Boost software. The improved heat transfer model mainly considers the effects of the swirl and boiling heat transfer inside the engine. In addition, a chemical kinetics mechanism including 475 reactions and 134 species is employed to predict the combustion of diesel engines fueled with biodiesel. The result shows that the boiling heat transfer will occur, especially in the high-temperature area. Analysis shows that the improved model is reliable and its precision is increased. Finally, the perturbation method is employed to investigate the relatively important inputs as the complex nonlinear function with a lot of output data and input data produced by the improved model. The relative effects of different parameters such as EGR, injection mass, injection timing, compression ratio, inlet air pressure, fuel injection pressure, exhaust pressure and inlet air temperature on performance and emission characteristics are compared. The eight parameters are investigated on four outputs of brake power, Brake Specific Fuel Consumption (BSFC), NOx and HC. The injected fuel mass plays an important role in emissions and performance. The EGR, compression ratio and inlet air pressure have a great effect on the HC and NOx emission. Full article
(This article belongs to the Special Issue Optimization Technology of Greenhouse Gas Emission Reduction)
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22 pages, 2281 KiB  
Review
Markers for the Comparison of the Performances of Anoxic Biotrickling Filters in Biogas Desulphurisation: A Critical Review
Processes 2021, 9(3), 567; https://doi.org/10.3390/pr9030567 - 23 Mar 2021
Cited by 6 | Viewed by 2634
Abstract
The agriculture and livestock industry generate waste used in anaerobic digestion to produce biogas containing methane (CH4), useful in the generation of electricity and heat. However, although biogas is mainly composed of CH4 (~65%) and CO2 (~34%), among the [...] Read more.
The agriculture and livestock industry generate waste used in anaerobic digestion to produce biogas containing methane (CH4), useful in the generation of electricity and heat. However, although biogas is mainly composed of CH4 (~65%) and CO2 (~34%), among the 1% of other compounds present is hydrogen sulphide (H2S) which deteriorates engines and power generation fuel cells that use biogas, generating a foul smell and contaminating the environment. As a solution to this, anoxic biofiltration, specifically with biotrickling filters (BTFs), stands out in terms of the elimination of H2S as it is cost-effective, efficient, and more environmentally friendly than chemical solutions. Research on the topic is uneven in terms of presenting performance markers, underestimating many microbiological indicators. Research from the last decade was analyzed (2010–2020), demonstrating that only 56% of the reviewed publications did not report microbiological analysis related to sulphur oxidising bacteria (SOB), the most important microbial group in desulphurisation BTFs. This exposes fundamental deficiencies within this type of research and difficulties in comparing performance between research works. In this review, traditional and microbiological performance markers of anoxic biofiltration to remove H2S are described. Additionally, an analysis to assess the efficiency of anoxic BTFs for biogas desulphurisation is proposed in order to have a complete and uniform assessment for research in this field. Full article
(This article belongs to the Special Issue Current Trends in Anaerobic Digestion Processes)
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22 pages, 68053 KiB  
Article
Full-Field Comparison of MRV and CFD of Gas Flow through Regular Catalytic Monolithic Structures
Processes 2021, 9(3), 566; https://doi.org/10.3390/pr9030566 - 23 Mar 2021
Cited by 3 | Viewed by 2417
Abstract
Understanding the influence of gas flow maldistribution in honeycombs can be beneficial for the process design in various technical applications. Although recent studies have investigated the effect of maldistribution by comparing the results of numerical simulations with experimental measurements, an exhaustive 3D full-field [...] Read more.
Understanding the influence of gas flow maldistribution in honeycombs can be beneficial for the process design in various technical applications. Although recent studies have investigated the effect of maldistribution by comparing the results of numerical simulations with experimental measurements, an exhaustive 3D full-field comparison is still lacking. Such full-field comparisons are required to identify and eliminate possible limitations of numerical and experimental tools. For that purpose, spatially resolved flow patterns were simulated by computational fluid dynamics (CFD) and measured experimentally by non-invasive NMR velocimetry (MRV). While the latter might suffer from a misinterpretation of artefacts, the reliability of CFD is linked to correctly chosen boundary conditions. Here, a full-field numerical and experimental analysis of the gas flow within catalytic honeycombs is presented. The velocity field of thermally polarized methane gas was measured in a regular 3D-printed honeycomb and a commercial monolith using an optimized MRV pulse sequence to enhance the obtained signal-to-noise ratio. A second pulse sequence was used to show local flow propagators along the axial and radial direction of the honeycomb to quantify the contribution of diffusion to mass transport. A quantitative comparison of the axially averaged convective flow as determined by MRV and CFD shows a very good matching with an agreement of ±5% and 10% for printed and commercial samples, respectively. The impact of maldistribution on the gas flow pattern can be observed in both simulation and experiments, confirming the existence of an entrance effect. Gas displacement measurements, however, revealed that diffusive interchannel transport can also contribute to maldistribution, as was shown for the commercial sample. The good agreement between the simulation and experiments underpins the reliability of both methods for studying gas hydrodynamics within opaque monolith structures. Full article
(This article belongs to the Special Issue Heterogeneous Catalysts for CO2 Valorisation)
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17 pages, 746 KiB  
Article
Optimization of Solvent and Extractive Distillation Sequence Considering Its Integration with Reactor
Processes 2021, 9(3), 565; https://doi.org/10.3390/pr9030565 - 23 Mar 2021
Cited by 7 | Viewed by 4136
Abstract
The integration of reaction and extractive distillation system is beneficial for reducing the process cost. A systematic method is proposed to identify the optimal solvent, solvent-to-feed ratio, extractive distillation sequence and reactor operating conditions based on the integration of reactor and extractive distillation. [...] Read more.
The integration of reaction and extractive distillation system is beneficial for reducing the process cost. A systematic method is proposed to identify the optimal solvent, solvent-to-feed ratio, extractive distillation sequence and reactor operating conditions based on the integration of reactor and extractive distillation. The non-key component matrix method is used to generate the extractive distillation sequences. The proposed method can be used to evaluate different solvents, solvent-to-feed ratios, as well as the extractive distillation sequences; the optimal extractive distillation parameters corresponding to the minimum total annualized cost (TAC) can be identified considering different operating conditions. For the selective hydrogenation of benzene to cyclohexene process, the minimum total annualized cost of unit desired product, 4.01 $·kmol−1, is achieved when the reactor’s inlet temperature is 333 K, solvent N-Formylmorpholine and sequence S2 are employed, and the solvent-to-feed ratio is 4. Full article
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18 pages, 4982 KiB  
Article
CFD Modelling of a Hydrogen/Air PEM Fuel Cell with a Serpentine Gas Distributor
Processes 2021, 9(3), 564; https://doi.org/10.3390/pr9030564 - 23 Mar 2021
Cited by 22 | Viewed by 4382
Abstract
Hydrogen-fueled fuel cells are considered one of the key strategies to tackle the achievement of fully-sustainable mobility. The transportation sector is paying significant attention to the development and industrialization of proton exchange membrane fuel cells (PEMFC) to be introduced alongside batteries, reaching the [...] Read more.
Hydrogen-fueled fuel cells are considered one of the key strategies to tackle the achievement of fully-sustainable mobility. The transportation sector is paying significant attention to the development and industrialization of proton exchange membrane fuel cells (PEMFC) to be introduced alongside batteries, reaching the goal of complete de-carbonization. In this paper a multi-phase, multi-component, and non-isothermal 3D-CFD model is presented to simulate the fluid, heat, and charge transport processes developing inside a hydrogen/air PEMFC with a serpentine-type gas distributor. Model results are compared against experimental data in terms of polarization and power density curves, including an improved formulation of exchange current density at the cathode catalyst layer, improving the simulation results’ accuracy in the activation-dominated region. Then, 3D-CFD fields of reactants’ delivery to the active electrochemical surface, reaction rates, temperature distributions, and liquid water formation are analyzed, and critical aspects of the current design are commented, i.e., the inhomogeneous use of the active surface for reactions, limiting the produced current and inducing gradients in thermal and reaction rate distribution. The study shows how a complete multi-dimensional framework for physical and chemical processes of PEMFC can be used to understand limiting processes and to guide future development. Full article
(This article belongs to the Special Issue Experimental Analysis and Numerical Simulation of Fuel Cells)
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28 pages, 14290 KiB  
Review
State-of-Art Review of NO Reduction Technologies by CO, CH4 and H2
Processes 2021, 9(3), 563; https://doi.org/10.3390/pr9030563 - 23 Mar 2021
Cited by 16 | Viewed by 2841
Abstract
Removal of nitrogen oxides during coal combustion is a subject of great concerns. The present study reviews the state-of-art catalysts for NO reduction by CO, CH4, and H2. In terms of NO reduction by CO and CH4, [...] Read more.
Removal of nitrogen oxides during coal combustion is a subject of great concerns. The present study reviews the state-of-art catalysts for NO reduction by CO, CH4, and H2. In terms of NO reduction by CO and CH4, it focuses on the preparation methodologies and catalytic properties of noble metal catalysts and non-noble metal catalysts. In the technology of NO removal by H2, the NO removal performance of the noble metal catalyst is mainly discussed from the traditional carrier and the new carrier, such as Al2O3, ZSM-5, OMS-2, MOFs, perovskite oxide, etc. By adopting new preparation methodologies and introducing the secondary metal component, the catalysts supported by a traditional carrier could achieve a much higher activity. New carrier for catalyst design seems a promising aspect for improving the catalyst performance, i.e., catalytic activity and stability, in future. Moreover, mechanisms of catalytic NO reduction by these three agents are discussed in-depth. Through the critical review, it is found that the adsorption of NOx and the decomposition of NO are key steps in NO removal by CO, and the activation of the C-H bond in CH4 and H-H bonds in H2 serves as a rate determining step of the reaction of NO removal by CH4 and H2, respectively. Full article
(This article belongs to the Special Issue Recent Advances in Processed Materials for Energy Applications)
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25 pages, 2710 KiB  
Review
Development of Strategies for AOB and NOB Competition Supported by Mathematical Modeling in Terms of Successful Deammonification Implementation for Energy-Efficient WWTPs
Processes 2021, 9(3), 562; https://doi.org/10.3390/pr9030562 - 23 Mar 2021
Cited by 19 | Viewed by 3881
Abstract
Novel technologies such as partial nitritation (PN) and partial denitritation (PDN) could be combined with the anammox-based process in order to alleviate energy input. The former combination, also noted as deammonification, has been intensively studied in a frame of lab and full-scale wastewater [...] Read more.
Novel technologies such as partial nitritation (PN) and partial denitritation (PDN) could be combined with the anammox-based process in order to alleviate energy input. The former combination, also noted as deammonification, has been intensively studied in a frame of lab and full-scale wastewater treatment in order to optimize operational costs and process efficiency. For the deammonification process, key functional microbes include ammonia-oxidizing bacteria (AOB) and anaerobic ammonia oxidation bacteria (AnAOB), which coexisting and interact with heterotrophs and nitrite oxidizing bacteria (NOB). The aim of the presented review was to summarize current knowledge about deammonification process principles, related to microbial interactions responsible for the process maintenance under varying operational conditions. Particular attention was paid to the factors influencing the targeted selection of AOB/AnAOB over the NOB and application of the mathematical modeling as a powerful tool enabling accelerated process optimization and characterization. Another reviewed aspect was the potential energetic and resources savings connected with deammonification application in relation to the technologies based on the conventional nitrification/denitrification processes. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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17 pages, 2181 KiB  
Review
A Review of Bio-Oil Production through Microwave-Assisted Pyrolysis
Processes 2021, 9(3), 561; https://doi.org/10.3390/pr9030561 - 23 Mar 2021
Cited by 17 | Viewed by 3602
Abstract
The issue of sustainability is a growing concern and has led to many environmentally friendly chemical productions through a great intensification of the use of biomass conversion processes. Thermal conversion of biomass is one of the most attractive tools currently used, and pyrolytic [...] Read more.
The issue of sustainability is a growing concern and has led to many environmentally friendly chemical productions through a great intensification of the use of biomass conversion processes. Thermal conversion of biomass is one of the most attractive tools currently used, and pyrolytic treatments represent the most flexible approach to biomass conversion. In this scenario, microwave-assisted pyrolysis could be a solid choice for the production of multi-chemical mixtures known as bio-oils. Bio-oils could represent a promising new source of high-value species ranging from bioactive chemicals to green solvents. In this review, we have summarized the most recent developments regarding bio-oil production through microwave-induced pyrolytic degradation of biomasses. Full article
(This article belongs to the Special Issue Microwave Conversion Techniques Intensification)
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12 pages, 2459 KiB  
Article
Enzyme-Assisted Method for Phycobiliproteins Extraction from Porphyra and Evaluation of Their Bioactivity
Processes 2021, 9(3), 560; https://doi.org/10.3390/pr9030560 - 23 Mar 2021
Cited by 10 | Viewed by 2382
Abstract
Due to the poor protein availability of algae in their unprocessed form, development of extraction methods for phycobiliproteins is of great significance. This study aimed to extract phycoerythrin (PE) and phycocyanin (PC) from Porphyra via bacterial enzymatic hydrolysis and to evaluate their bioactivity. [...] Read more.
Due to the poor protein availability of algae in their unprocessed form, development of extraction methods for phycobiliproteins is of great significance. This study aimed to extract phycoerythrin (PE) and phycocyanin (PC) from Porphyra via bacterial enzymatic hydrolysis and to evaluate their bioactivity. To induce enzyme production, Porphyra powder was added into the culture medium of two marine bacterial strains. The pH and enzyme activity of the cultured supernatant, namely crude enzyme solution, were significantly raised. For PE and PC extraction, Porphyra were incubated within crude enzyme solution with homogenization and ultrasonication followed by ultrafiltration process. After distinguishing by fast performance liquid chromatography (FPLC), three major fractions were observed and identified as R-PE, R-PC and small molecular PE by high-performance liquid chromatography (HPLC) and polyacrylamide gel electrophoresis (PAGE) analysis. With respect to bioactivity, these three fractions exhibited free radical scavenging and antioxidant activities in a various degree. In addition, the angiotensin-converting-enzyme (ACE) inhibitory activity of both R-PE and R-PC fractions was observed in a concentration-dependent manner. Taken together, the employed process of bacterial enzymatic hydrolysis is suggested to be a feasible method to obtain PE and PC from Porphyra without limiting their bioactivity. Full article
(This article belongs to the Special Issue Application of Proteomics and Enzyme Technologies in Foods)
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15 pages, 3619 KiB  
Article
Evaluation of the Adsorption Efficiency on the Removal of Lead(II) Ions from Aqueous Solutions Using Azadirachta indica Leaves as an Adsorbent
Processes 2021, 9(3), 559; https://doi.org/10.3390/pr9030559 - 23 Mar 2021
Cited by 30 | Viewed by 4738
Abstract
The efficiency of Azadirachta indica (neem leaves) on the removal of Pb(II) ions by adsorption from aqueous solution was investigated in this study. The efficiency of these leaves (without chemical or thermal treatment) for the adsorption of Pb(II) ions has not previously been [...] Read more.
The efficiency of Azadirachta indica (neem leaves) on the removal of Pb(II) ions by adsorption from aqueous solution was investigated in this study. The efficiency of these leaves (without chemical or thermal treatment) for the adsorption of Pb(II) ions has not previously been reported. Batch experiments were performed to study the effect of the particle size, pH, adsorbent dose, contact time, initial Pb(II) ion concentration, and temperature. The maximum removal of 93.5% was achieved from an original Pb(II) ion solution concentration of 50 mg/L after 40 min, at pH 7, with 0.60 g of an adsorbent dose. The maximum adsorption capacity recorded was 39.7 mg/g. The adsorption process was also studied by examining Langmuir, Freundlich, Temkin isotherm, and Dubinin–Radushkevich (D-R) isotherm models. The results revealed that the adsorption system follows the pseudo-second-order model and fitted the Freundlich model. Several thermodynamic factors, namely, the standard free energy (∆G°), enthalpy (∆H°), and entropy (∆S°) changes, were also calculated. The results demonstrated that the adsorption is a spontaneous, physical, and exothermic process. The surface area, pore size, and volume of adsorbent particles were measured and presented using a surface area analyzer (BET); the morphology was scanned and presented with the scanning electron microscope technique (SEM); and the functional groups were investigated using μ-FTIR. Full article
(This article belongs to the Special Issue Various Adsorbents for Water Purification Processes)
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17 pages, 9904 KiB  
Article
Numerical Analysis of Hydrodynamic Loads on Passing and Moored Ships in Shallow Water
Processes 2021, 9(3), 558; https://doi.org/10.3390/pr9030558 - 22 Mar 2021
Cited by 4 | Viewed by 2152
Abstract
In this study, hydrodynamic interactions between passing and moored ships were studied by applying a time-domain numerical simulation method. The boundary value problem for a fluid domain was formulated based on a potential flow theory. A numerical method was developed based on a [...] Read more.
In this study, hydrodynamic interactions between passing and moored ships were studied by applying a time-domain numerical simulation method. The boundary value problem for a fluid domain was formulated based on a potential flow theory. A numerical method was developed based on a finite element method with an efficient re-mesh algorithm. Regarding the free-surface boundary conditions, both double-body and free-surface models were considered for examining the free-surface effect on the hydrodynamic forces due to the passing ship. First, numerical results were validated by comparison with the model test results of Kriebel et al. (2005), where generic Series 60 hulls were considered as the target model for the passing and moored ships. In addition, hydrodynamic pressure fields and force time-series were investigated to understand the passing ship problem. Second, a series of numerical simulations were performed to study the effects of the passing ship speed, separation distance, water depth, and relative vessel size, which were used to compare the peak values of hydrodynamic forces. The applicability and limitations of the double-body and free-surface models are discussed for predicting passing ship loads. Full article
(This article belongs to the Special Issue Theoretical and Numerical Marine Hydrodynamics)
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13 pages, 4024 KiB  
Article
Cucumis melo Enhances Enalapril Mediated Cardioprotection in Rats with Isoprenaline Induced Myocardial Injury
Processes 2021, 9(3), 557; https://doi.org/10.3390/pr9030557 - 22 Mar 2021
Cited by 1 | Viewed by 2104
Abstract
This study sought to investigate the cardioprotective potency and interaction of muskmelon (Cucumis melo) with enalapril (ENA) against myocardial damage caused by acute and chronic isoprenaline (ISO) treatments in rats. In the acute model, 150 mg/kg (s.c) of ISO was administered [...] Read more.
This study sought to investigate the cardioprotective potency and interaction of muskmelon (Cucumis melo) with enalapril (ENA) against myocardial damage caused by acute and chronic isoprenaline (ISO) treatments in rats. In the acute model, 150 mg/kg (s.c) of ISO was administered for two consecutive days at the end of pretreatment with either ENA, muskmelon, or both in their respective groups. ISO was introduced into the chronic therapy of ENA/muskmelon/ENA + muskmelon groups during the last 10 days at 3 mg/kg. Muskmelon was tested at three doses (100, 200, and 500 mg/kg, p.o., 30 days), and one normal dose of ENA (10 mg/kg) was used. Blood samples were taken at the end of treatment, and the animals were sacrificed. Biochemical markers such as LDH and CK-MB, as well as antioxidant (superoxide dismutase (SOD) and catalases) and thiobarbituric acid reactive species (TBARS) were measured in both serum and heart tissue homogenate (HTH). To confirm the biochemical findings, histological slides of heart tissue were prepared. ISO administration induced an elevation in the amount of TBARS, which was increased in all groups in which it was administered. Prior treatment with muskmelon and ENA in animals resulted in a rise in biomarker activity in homogenated heart tissue and a decrease in serum. In terms of alleviating the abnormal conditions caused by ISO, the group given a high dose of muskmelon and combined therapy had the best outcomes. The activities of SOD and catalase were substantially higher in the treated classes. Histological findings showing the cytoprotective actions of the high dose of muskmelon and ENA have confirmed the biochemical outcomes of both models. It is therefore concluded that the high dose of muskmelon (500 mg/kg) has a promising cardioprotective potential that is improved more efficiently in the acute injury model in the presence of ENA. Full article
(This article belongs to the Special Issue Study on Processing and Biological Activity of Functional Foods)
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15 pages, 8338 KiB  
Article
Phase Distribution in the Tip Clearance of a Multiphase Pump at Multiple Operating Points and Its Effect on the Pressure Fluctuation Intensity
Processes 2021, 9(3), 556; https://doi.org/10.3390/pr9030556 - 22 Mar 2021
Cited by 7 | Viewed by 1493
Abstract
Tip clearance has a great effect on the flow and pressure fluctuation characteristics in a multiphase pump, especially at multiple operating points. The phase distribution and pressure fluctuation in tip clearance in a multiphase pump are revealed using the CFD (computational fluid dynamics) [...] Read more.
Tip clearance has a great effect on the flow and pressure fluctuation characteristics in a multiphase pump, especially at multiple operating points. The phase distribution and pressure fluctuation in tip clearance in a multiphase pump are revealed using the CFD (computational fluid dynamics) technology and high-speed photography methods. In this paper, the phase distribution, the gas-liquid two-phase velocity slip, and the pressure fluctuation intensity are comprehensively analyzed. Results show with the increase of the tip clearance, the multiphase pump pressurization performance is obviously deteriorated. In the meantime, the gas accumulation mainly occurs at the hub, the blade suction side (SS), and the tip clearance, and the maximum gas-liquid two-phase velocity difference is near the impeller streamwise of 0.4. In addition, the tip clearance improves the gas-liquid two-phase distribution in the pump, that is, the larger the tip clearance is, the more uniform the gas-liquid distribution becomes. Furthermore, the gas leads to the maximum pressure fluctuation intensity in the tip clearance which is closer to the tip leakage flow (TLF) outlet, and has a greater effect on the degree of flow separation in the tip clearance. Full article
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16 pages, 17259 KiB  
Article
Droplet Dynamics on a Wettability Patterned Surface during Spray Impact
Processes 2021, 9(3), 555; https://doi.org/10.3390/pr9030555 - 22 Mar 2021
Cited by 7 | Viewed by 3858
Abstract
Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously [...] Read more.
Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously remove the impacted spray droplets from the horizontal surface. We observed that the spray droplets falling on the superhydrophilic wedge region spread and form a thin liquid film, which is passively transported away from the surface. However, most of the droplets falling on the superhydrophobic region move towards the wedge without any flooding. The physics of the passive transport of the liquid film on a wedge is also delved into using numerical modelling. In particular, we elucidate the different modes of droplet transport in the superhydrophobic region and the interaction of multiple droplets. The observed droplet dynamics could have profound implications in spray cooling systems and passive removal of liquid from a horizontal surface. This study’s findings will be beneficial for the optimization of efficient wettability patterned surfaces for spray cooling application. Full article
(This article belongs to the Special Issue Micro and Nanotechnology: Application in Surface Modification)
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22 pages, 990 KiB  
Review
Effect of Alumina Additives on Mechanical and Fresh Properties of Self-Compacting Concrete: A Review
Processes 2021, 9(3), 554; https://doi.org/10.3390/pr9030554 - 22 Mar 2021
Cited by 26 | Viewed by 3230
Abstract
Self-compacting concrete (SCC) has been increasingly used in the construction sector due to its favorable characteristics in improving various durability and rheology aspects of concrete such as deformability and segregation resistance. Recently, the studies on the application of nano-alumina (NA) produced from factory [...] Read more.
Self-compacting concrete (SCC) has been increasingly used in the construction sector due to its favorable characteristics in improving various durability and rheology aspects of concrete such as deformability and segregation resistance. Recently, the studies on the application of nano-alumina (NA) produced from factory wastes have been significantly considered to enhancing the performance, and mechanical strength, of SCC. Many experimental works show that NA can be used in SCC with appropriate proportion to enjoy the benefits of improved microstructure, fresh and hardened properties, durability, and resistance to elevated temperature. However, a limited detailed review is available to particularly study using NA to improve the performance of SCC, so far. Hence, the present study is conducted to fill the existing gap of knowledge. In this study, the effect of using NA in improving rheological, mechanical parameters, and elevated temperature resistance of SCC is reviewed. This research summarized the studies in this area, which have been different from the previous researches, and provided a discussion on limitations, practical implications, and suggestions for future studies. Full article
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9 pages, 951 KiB  
Article
Study of the Impact of Nonionic Additives on the Composition and Structure of Petroleum Dispersed Systems by IR Spectroscopy
Processes 2021, 9(3), 553; https://doi.org/10.3390/pr9030553 - 21 Mar 2021
Cited by 8 | Viewed by 1570
Abstract
The article describes a technique for obtaining a quantitative assessment of the composition and structure of the petroleum dispersed system (PDS) and its individual structural formations based on the data of the component composition and infrared spectroscopy. In the PDS of heavy petroleum [...] Read more.
The article describes a technique for obtaining a quantitative assessment of the composition and structure of the petroleum dispersed system (PDS) and its individual structural formations based on the data of the component composition and infrared spectroscopy. In the PDS of heavy petroleum feedstock modified with a mixture of unsaturated carboxylic acids and four atomic alcohols, the components of the core and the inner solvation shell are different in structure. The degree of affinity of the components of the inner and outer solvation shells of the complex structural unit (CSU), as well as that of the outer solvation shell and the hydrocarbon components of the dispersion medium, increases. Nonionic additives are involved, to a greater degree, in structuring the solvation shell of the CSU and also increase the degree of its affinity with the hydrocarbon components, which leads to an increase in the dispersion of the system and a decrease in its mobility. Full article
(This article belongs to the Special Issue Dynamic Modeling and Control in Chemical and Energy Processes)
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19 pages, 2914 KiB  
Article
Study on the Characteristics of Size-Segregated Particulate Water-Soluble Inorganic Ions and Potentially Toxic Metals during Wintertime in a High Population Residential Area in Beijing, China
Processes 2021, 9(3), 552; https://doi.org/10.3390/pr9030552 - 21 Mar 2021
Cited by 7 | Viewed by 2425
Abstract
Airborne particulate matter (PM) pollution often occurs in the wintertime in northern China, posing a potential threat to human health. To date, there are limited studies about the metals and inorganic ions to link source apportionments and health risk assessments in the different [...] Read more.
Airborne particulate matter (PM) pollution often occurs in the wintertime in northern China, posing a potential threat to human health. To date, there are limited studies about the metals and inorganic ions to link source apportionments and health risk assessments in the different size-segregated PM samples. In this study, our samples were collected by a high-volume air sampler from 26 December 2018 to 11 January 2019 in a high population residential area (Beijing). Water-soluble inorganic ions, metal elements in the different size-segregated PM samples were determined for health risk assessments by inhalation of PM. During the sampling period in Beijing, the average concentrations of PM1.1 and PM1.1–2.0 were 39.67 ± 10.66 μg m−3 and 32.25 ± 6.78 μg m−3. Distinct distribution profiles characterized the different elements. The markers of coal combustion Pb, As, and Se had >52% of their mass concentration in PM1.1. The average mass ratios of (NO3 + NO2)/SO42−, Cl/Na+, Cl/K+, and Cl/(NO3− + NO2) were 1.68, 6.58, 6.18, and 0.57, which showed that coal combustion and vehicle emissions were the main anthropogenic sources of PM in Beijing in winter. PM1.1 was the major contributor of Pb, Cd, and As for carcinogenic risks (CR) and hazard quotient (HQ). It was indicated that PM1.1 is more harmful than coarse PM. The toxic elements of Cr (VI) (1.12 × 10−6), V (0.69 × 10−6), and As (0.41 × 10−6) caused higher CR for children than Ni, Cd, Co, and Pb. Meanwhile, Pb (35.30 × 10−6) and Ni (21.07 × 10−6) caused higher CR for adults than As, Cr (VI), V, Co, and Cd, especially PM1.1. This study provides detailed composition data and the first report on human health in a high population residential area in Beijing. Full article
(This article belongs to the Section Environmental and Green Processes)
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11 pages, 1880 KiB  
Article
A Logistic Approach for Kinetics of Isothermal Pyrolysis of Cellulose
Processes 2021, 9(3), 551; https://doi.org/10.3390/pr9030551 - 20 Mar 2021
Cited by 3 | Viewed by 1934
Abstract
A kinetic model is proposed to fit isothermal thermogravimetric data obtained from cellulose in an inert atmosphere at different temperatures. The method used here to evaluate the model involves two steps: (1) fitting of single time-derivative thermogravimetric curves (DTG) obtained at different temperatures [...] Read more.
A kinetic model is proposed to fit isothermal thermogravimetric data obtained from cellulose in an inert atmosphere at different temperatures. The method used here to evaluate the model involves two steps: (1) fitting of single time-derivative thermogravimetric curves (DTG) obtained at different temperatures versus time, and (2) fitting of the rate parameter values obtained at different temperatures versus temperature. The first step makes use of derivative of logistic functions. For the second step, the dependence of the rate factor on temperature is evaluated. That separation of the curve fitting from the analysis of the rate factor resulted to be very flexible since it proved to work for previous crystallization studies and now for thermal degradation of cellulose. Full article
(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)
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24 pages, 6149 KiB  
Article
Applying Lean Six Sigma Methodology to a Pharmaceutical Manufacturing Facility: A Case Study
Processes 2021, 9(3), 550; https://doi.org/10.3390/pr9030550 - 20 Mar 2021
Cited by 39 | Viewed by 16946
Abstract
This research examines a case study on the implementation of an effective approach to advanced Lean Six Sigma problem-solving within a pharmaceutical manufacturing site which manufactures acetaminophen (paracetamol containing pain relief) tablets. Though this study was completed in a single manufacturing company, the [...] Read more.
This research examines a case study on the implementation of an effective approach to advanced Lean Six Sigma problem-solving within a pharmaceutical manufacturing site which manufactures acetaminophen (paracetamol containing pain relief) tablets. Though this study was completed in a single manufacturing company, the implementation of this study delivers important application and results that can be deployed in other such manufacturing companies. The manufacturing site faced backlogs in customer orders due to increased demand. Increased demand is due to brand popularity and recognition, product efficacy and a COVID 19 pandemic that intensified the demand for pain relief tablets in an already very busy site. With increased demand, to ensure timely deliveries, customer satisfaction and minimize delays, sources of site productivity losses and wastes needed to be analyzed and reduced or eliminated. Manufacturing Packaging line downtime was identified as one area of concern. The goal of the research was to introduce a problem-solving technique to reduce downtime within a manufacturing site without affecting the production required to fulfil customer demand while increasing product quality. The research utilized an integrated LSS methodology which identifies, stratifies and effectively eliminates non-value adding (waste) activities, by following a 7-step customized problem-solving methodology which resulted in complete elimination of the issue under investigation and savings of just under half a million dollars. The learnings are being deployed and leveraged worldwide across the pharmaceutical organizations parent site and sister sites. The presented results demonstrated that Lean Six Sigma methodology and tools are effective for accurate root causing of problems and enablers of implementation of continuous improvement. Full article
(This article belongs to the Special Issue Sustainable Manufacturing and LCA Tools for Industrial Sectors)
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21 pages, 6620 KiB  
Article
Novel Numerical Spiking Neural P Systems with a Variable Consumption Strategy
Processes 2021, 9(3), 549; https://doi.org/10.3390/pr9030549 - 20 Mar 2021
Cited by 5 | Viewed by 1720
Abstract
A novel variant of NSN P systems, called numerical spiking neural P systems with a variable consumption strategy (NSNVC P systems), is proposed. Like the spiking rules consuming spikes in spiking neural P systems, NSNVC P systems introduce a variable consumption strategy by [...] Read more.
A novel variant of NSN P systems, called numerical spiking neural P systems with a variable consumption strategy (NSNVC P systems), is proposed. Like the spiking rules consuming spikes in spiking neural P systems, NSNVC P systems introduce a variable consumption strategy by modifying the form of the production functions used in NSN P systems. Similar to the delay feature of the spiking rules, NSNVC P systems introduce a postponement feature into the production functions. The execution of the production functions in NSNVC P systems is controlled by two, i.e., polarization and threshold, conditions. Multiple synaptic channels are used to transmit the charges and the production values in NSNVC P systems. The proposed NSNVC P systems are a type of distributed parallel computing models with a directed graphical structure. The Turing universality of the proposed NSNVC P systems is proved as number generating/accepting devices. Detailed descriptions are provided for NSNVC P systems as number generating/accepting devices. In addition, a universal NSNVC P system with 66 neurons is constructed as a function computing device. Full article
(This article belongs to the Special Issue Modeling, Simulation and Design of Membrane Computing System)
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11 pages, 1418 KiB  
Article
The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System
Processes 2021, 9(3), 548; https://doi.org/10.3390/pr9030548 - 19 Mar 2021
Cited by 10 | Viewed by 1923
Abstract
The typical time-dependent decrease of the iron corrosion rate is often difficult to consider while designing Fe0-based remediation systems. One of the most promising approaches is the amendment with manganese dioxide (Fe0/MnO2 system). The resulting system is a [...] Read more.
The typical time-dependent decrease of the iron corrosion rate is often difficult to consider while designing Fe0-based remediation systems. One of the most promising approaches is the amendment with manganese dioxide (Fe0/MnO2 system). The resulting system is a very complex one where characterization is challenging. The present communication uses methylene blue discoloration (MB method) to characterize the Fe0/MnO2 system. Shaken batch experiments (75 rpm) for 7 days were used. The initial MB concentration was 10 mg L−1 with the following mass loading: [MnO2] = 2.3 g L−1, [sand] = 45 g L−1, and 0 < [Fe0] (g L−1) ≤ 45. The following systems where investigated: Fe0, MnO2, sand, Fe0/MnO2, Fe0/sand, and Fe0/MnO2/sand. Results demonstrated that MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the test-tubes. Results confirm the complexity of the Fe0/MnO2/sand system, while establishing that both MnO2 and sand improve the efficiency of Fe0/H2O systems in the long-term. The mechanisms of water decontamination by amending Fe0-based systems with MnO2 is demonstrated by the MB method. Full article
(This article belongs to the Section Environmental and Green Processes)
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16 pages, 5652 KiB  
Article
Effects of Micro-Tab on the Lift Enhancement of Airfoil S-809 with Trailing-Edge Flap
Processes 2021, 9(3), 547; https://doi.org/10.3390/pr9030547 - 19 Mar 2021
Cited by 1 | Viewed by 1986
Abstract
Recently, the Trailing-Edge Flap with Micro-Tab (TEF with Micro-Tab) has been exploited to enhance the performance of wind turbine blades. Moreover, it can also be used to generate more lift and delay the onset of stall. This study focused mostly on the use [...] Read more.
Recently, the Trailing-Edge Flap with Micro-Tab (TEF with Micro-Tab) has been exploited to enhance the performance of wind turbine blades. Moreover, it can also be used to generate more lift and delay the onset of stall. This study focused mostly on the use of TEF with Micro-Tab in wind turbine blades using NREL’s S-809 as a model airfoil. In particular, the benefits generated by TEF with Micro-Tab may be of great interest in the design of wind turbine blades. In this paper, an attempt was made to evaluate the influence of TEF with Micro-Tab on the performance of NREL’s S-809 airfoils. Firstly, a computational fluid dynamics (CFD) model for the airfoil NREL’s S-809 was established, and validated by comparison with previous studies and wind tunnel experimental data. Secondly, the effects of the flap position (H) and deflection angle (αF) on the flow behaviors were investigated. As a result, the effect of TEF on air-flow behavior was demonstrated by augmenting the pressure coefficient at the lower surface of the airfoil at flap position 80% chord length (C) and αF = 7.5°. Thirdly, the influence of TEF with Micro-Tab on the flow behaviors of the airfoil NREL’s S-809 was studied and discussed. Different Micro-Tab positions and constant TEF were examined. Finally, the effects of TEF with Micro-Tab on the aerodynamic characteristics of the S-809 with TEF were compared. The results showed that an increase in the maximum lift coefficient by 25% and a delay in the air-flow stall were accomplished due to opposite sign vortices, which was better than the standard airfoil and S-809 with TEF. Therefore, it was deduced that the benefits of TEF with Micro-Tab were apparent, especially at the lower surface of the airfoil. This particularly suggests that the developed model could be used as a new trend to modify the designs of wind turbine blades. Full article
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12 pages, 893 KiB  
Article
Agronomic Characteristics of the Compost-Bedded Pack Made with Forest Biomass or Sawdust
Processes 2021, 9(3), 546; https://doi.org/10.3390/pr9030546 - 19 Mar 2021
Cited by 7 | Viewed by 2175
Abstract
To ascertain the agronomic value of the material resulting from the compost-bedded pack (CBP) in dairy barns, a cross-over experiment was designed with eight dry non-pregnant Holstein cows. The study was performed in two 11-week periods. Bedding materials used were: (1) CBP with [...] Read more.
To ascertain the agronomic value of the material resulting from the compost-bedded pack (CBP) in dairy barns, a cross-over experiment was designed with eight dry non-pregnant Holstein cows. The study was performed in two 11-week periods. Bedding materials used were: (1) CBP with sawdust (S) and (2) CBP with forest biomass (FB). Samples were taken from the raw bedding materials and from the CBP across the experiment. We conducted an additional study preparing two piles, one of each CBP material, to accomplish a composting process of 3 months, where samples were also taken. Granulometry and some chemical composition characteristics of FB made it a suitable bedding material to be used as CBP, but its high moisture content limited the ability to absorb liquid manure. Both the degree of stability of the organic matter and the temperature evolution of CBP suggest that a real composting process did not occur. Finally, the composting process of the piles did not lead to any relevant change in CBP materials. From the agronomic point of view, S and FB present potentially valuable characteristics as regards organic amendment in the soil, thanks to their high organic matter content and low nutrient content. Full article
(This article belongs to the Special Issue Composting in the Framework of Circular Economy)
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25 pages, 5177 KiB  
Article
Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller
Processes 2021, 9(3), 545; https://doi.org/10.3390/pr9030545 - 19 Mar 2021
Cited by 2 | Viewed by 1747
Abstract
An experimental study on the flow pattern dynamics in a standard mixing vessel with radial baffles filled with water and induced by a pitched blade impeller pumping downward is presented. Investigation is mainly focused on detection and analysis of quasi-periodical or periodical low-frequency [...] Read more.
An experimental study on the flow pattern dynamics in a standard mixing vessel with radial baffles filled with water and induced by a pitched blade impeller pumping downward is presented. Investigation is mainly focused on detection and analysis of quasi-periodical or periodical low-frequency phenomenon connected with time- and length-scales considerably exceeding the Blade Passage Frequency (hereinafter BPF) and common turbulent eddies. This phenomenon, which is expressed as large-scale mean-flow variations, is generally known as flow Macro-Instability (hereinafter MI). It could break-down just below the liquid surface, or it crashes to the liquid surface and causes its Macro-Swelling (hereinafter MS). Our investigation was based on classical two-dimensional (2D) Particle Image Velocimetry (hereinafter PIV) measurement within 3 selected vertical planes in the vessel and subsequent analysis of the velocity field. The dominant frequencies evaluated in the selected points and overall analysis of the quasi-periodical macro-flow pattern behavior is to be shown. Identification of the quasi-periodical substructures appeared within the flow pattern was performed using the Oscillation Pattern Decomposition (hereinafter OPD) method. Observation of the macro-flow patterns confirmed presence of the macro-flow structures detected within flow pattern at the identical mixing pilot plant setup by previous investigations of the MIs phenomenon, i.e., the primary circulation loop and strong impeller discharge jet located in the lower vessel segment and the strong ascending wall current at the baffle, which break-down below the surface very often. A further important contribution of the presented work is the investigation of both flow pattern within the baffles vicinity and in the middle of the sector far from the baffle, showing a significant difference. Low-frequency periodical (or quasi-periodical) behavior of the investigated macro-structures was qualitatively confirmed by the presented results and it was quantified using the velocity dominant frequencies evaluation, as noted below. This frequency analysis brings insight into the supposed and detected interconnections between dynamics of the adjacent flow structures. Detected different flow patterns within the main plane near the baffles and in the inclined plane reveal a strong influence of the baffle presence to the local vertical flow, especially within the upper part of the vessel. Quite a different flow pattern appears tangentially in front of and behind the baffle, where a wake is revealed, indicating significant influence of the baffle on the local tangential flow. The new findings represent a contribution to better understanding the physical phenomena behind the standard mixing process. Full article
(This article belongs to the Special Issue Advances in the Chemical Mixing Process)
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40 pages, 28052 KiB  
Article
Variable Selection for Fault Detection Based on Causal Discovery Methods: Analysis of an Actual Industrial Case
Processes 2021, 9(3), 544; https://doi.org/10.3390/pr9030544 - 19 Mar 2021
Cited by 5 | Viewed by 2546
Abstract
Variable selection constitutes an essential step to reduce dimensionality and improve performance of fault detection and diagnosis in large scale industrial processes. For this reason, in this paper, variable selection approaches based on causality are proposed and compared, in terms of model adjustment [...] Read more.
Variable selection constitutes an essential step to reduce dimensionality and improve performance of fault detection and diagnosis in large scale industrial processes. For this reason, in this paper, variable selection approaches based on causality are proposed and compared, in terms of model adjustment of available data and fault detection performance, with several other filter-based, wrapper-based, and embedded-based variable selection methods. These approaches are applied in a simulated benchmark case and an actual oil and gas industrial case considering four different learning models. The experimental results show that obtained models presented better performance during the fault detection stage when variable selection procedures based on causality were used for purpose of model building. Full article
(This article belongs to the Special Issue Synergies in Combined Development of Processes and Models)
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11 pages, 263 KiB  
Article
Synbiotic Fermented Milk with Double Fortification (Fe-Zn) as a Strategy to Address Stunting: A Randomized Controlled Trial among Children under Five in Yogyakarta, Indonesia
Processes 2021, 9(3), 543; https://doi.org/10.3390/pr9030543 - 19 Mar 2021
Cited by 7 | Viewed by 3163
Abstract
Stunting is one of the public health problems that has yet to be solved in Indonesia. This study developed synbiotic fermented milk with iron and zinc fortification that was then tested in a clinical setting. The product was made from skimmed milk and [...] Read more.
Stunting is one of the public health problems that has yet to be solved in Indonesia. This study developed synbiotic fermented milk with iron and zinc fortification that was then tested in a clinical setting. The product was made from skimmed milk and fructooligosaccharides (FOS) and fermented with Lactobacillus plantarum. A sample of 94 stunted children under five years old were randomly assigned to intervention or control groups. The intervention group received double-fortified synbiotic milk, while the control group drank non-fortified milk. After three months, the number of normal children in both groups, according to weight- or height-for-age z-score category, was found to be increasing. However, the difference between the two groups was not significant (p > 0.05). The study suggests that fermented milk may have a good effect on child growth. Further research is needed to deepen the potency of synbiotic fermented milk for stunted children. Full article
(This article belongs to the Special Issue Advances in Microbial Fermentation Processes)
14 pages, 4140 KiB  
Article
Analysis of a Series‑Parallel Resonant Converter for DC Microgrid Applications
Processes 2021, 9(3), 542; https://doi.org/10.3390/pr9030542 - 18 Mar 2021
Cited by 8 | Viewed by 2571
Abstract
An input-series output-parallel soft switching resonant circuit with balance input voltage and primary-side current is studied and implemented for direct current (DC) microgrid system applications. Two resonant circuits are connected with input-series and output-parallel structure to have the advantages of low voltage stresses [...] Read more.
An input-series output-parallel soft switching resonant circuit with balance input voltage and primary-side current is studied and implemented for direct current (DC) microgrid system applications. Two resonant circuits are connected with input-series and output-parallel structure to have the advantages of low voltage stresses on active devices and low current stresses on power diodes. A balance capacitor is adopted on high voltage side to balance two input capacitor voltages. The LLC (inductor–inductor–capacitor) resonant circuit cells are employed in the converter to have soft switching operation for power semiconductors. The magnetic coupling component is adopted on the primary-side to automatically realize current balance of the two resonant circuits. In the end, a laboratory hardware circuit is built and tested. Experiments demonstrate and prove the validity of the resonant converter. Full article
(This article belongs to the Special Issue Application of Power Electronics Technologies in Power System)
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2 pages, 168 KiB  
Editorial
Special Issue “Design, Control and Optimization of Desalination Processes”
Processes 2021, 9(3), 541; https://doi.org/10.3390/pr9030541 - 18 Mar 2021
Viewed by 1385
Abstract
Water scarcity due to the ever-increasing worldwide demand and climate change is one of the greatest hurdles of our time [...] Full article
(This article belongs to the Special Issue Design, Control and Optimization of Desalination Processes)
27 pages, 13372 KiB  
Article
Modelling and Optimization of Processing Factors of Pumpkin Seeds Oil Extraction under Uniaxial Loading
Processes 2021, 9(3), 540; https://doi.org/10.3390/pr9030540 - 18 Mar 2021
Cited by 12 | Viewed by 3188
Abstract
In the present study, a Box–Behnken design of response surface methodology (RSM) was employed to optimize the processing factors (force: 100, 150, and 200 kN; speed: 3, 5, and 7 mm/min; and temperature: 40, 60, and 80 °C) for extracting pumpkin seeds oil [...] Read more.
In the present study, a Box–Behnken design of response surface methodology (RSM) was employed to optimize the processing factors (force: 100, 150, and 200 kN; speed: 3, 5, and 7 mm/min; and temperature: 40, 60, and 80 °C) for extracting pumpkin seeds oil under uniaxial compression. The design generated 15 experiments including twelve combinations of factors and three replicates at the center point. The responses: oil yield (%), oil expression efficiency (%), and energy (J) were calculated, and the regression models determined were statistically analyzed and validated. The optimum factors combination: 200 kN, 4 mm/min and 80 °C predicted the oil yield of 20.48%, oil expression efficiency of 60.90%, and energy of 848.04 J. The relaxation time of 12 min at the optimum factors increased the oil efficiency to 64.53%. The lower oil point force was determined to be 57.32 kN for estimating the maximum oil output. The tangent curve and generalized Maxwell models adequately (R2 = 0.996) described the compression and relaxation processes of pumpkin seeds oil extraction. Peroxide value increased with temperatures. The study provides detailed information useful for processing different bulk oilseeds under uniaxial loading for optimizing the mechanical oil pressing in large-scale oil production. Full article
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15 pages, 1330 KiB  
Article
Indirect Monitoring of Anaerobic Digestion for Cheese Whey Treatment
Processes 2021, 9(3), 539; https://doi.org/10.3390/pr9030539 - 18 Mar 2021
Cited by 2 | Viewed by 1747
Abstract
Efficient monitoring is an open problem in the operation of anaerobic digestion processes, due to the lack of accurate, low-cost, and proper sensors for the on-line monitoring of key process variables. This paper presents two approaches for the indirect monitoring of the anaerobic [...] Read more.
Efficient monitoring is an open problem in the operation of anaerobic digestion processes, due to the lack of accurate, low-cost, and proper sensors for the on-line monitoring of key process variables. This paper presents two approaches for the indirect monitoring of the anaerobic digestion of cheese whey wastewater. First, the observability property is addressed using conventional and nonconventional techniques, including an observability index. Then, two model-based observer techniques, an extended Luenberger observer, a sliding mode observer, and a data-driven technique based on fractal analysis are formulated and discussed. The performance and capabilities of the proposed methodologies are illustrated on a validated model with experimental data of the anaerobic digestion of cheese whey. Experimental pH measurements are used for the data-driven approach based on fractal analysis. The experimental data sets correspond to experimental conditions (pH > 7.5 and temperature (T) = 40 °C) favoring volatile fatty acid (VFA) production (30 g/L) with simultaneously acceptable biogas production (3420 mL). Results also show that the proposed observers were able to predict satisfactory key process variables. On the other hand, the fractal analysis provides reliable qualitative trends of VFA production and chemical oxygen demand (COD) consumption. Full article
(This article belongs to the Special Issue Anaerobic Processes, Monitoring and Intelligence Control)
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