Optimization Of Operating Conditions Research Articles

A Review on Start-Up Phase Optimization of Kitchen Waste Anaerobic Digestion

Kitchen waste has been confirmed as an appropriate substrate for anaerobic digestion, although means of alleviating the difficulties and time-consuming nature of the start-up phase need to be further explored. Based on the mechanism of anaerobic digestion, we discuss the factors influencing the anaerobic start-up phase of kitchen waste. By controlling the temperature, pH, organic loading rate, inoculation ratio and other parameters, the high activity of methane-producing archaea and other bacteria can be intensified, thereby increasing the biogas yield. Furthermore, we introduce the methods of substrate pretreatment, operating condition optimization and conductive material addition. Finally, we put forward future perspectives and research gaps related to accelerating the start-up phase of anaerobic bioreactors utilized for kitchen waste biodegradation.

The coagulation behavior and removal efficiency of microplastics in drinking water treatment

As a kind of emerging contaminants, microplastics (MPs) have got great attention due to its worldwide distribution, ecotoxicology and difficult to remove. MPs have already been found in the drinking water because of its low removal efficiency during drinking water treatment. As an important process to remove the particles in water, the coagulation behavior of MPs with different characteristics is still not clear. Besides that, research about the removal of MPs by coagulation is on the initial stage and the results are not consistent. This article studied on the MPs which were hard to be removed during the coagulation by conventional coagulation methods during the drinking water treatment, aimed to found the influence of MPs characteristics on the coagulation behavior, explore the removal efficiency of MPs under optimal coagulation conditions and infer the coagulation mechanisms of MPs. According to the results of this article, size and concentration of MPs both had significant effect on the coagulation, but the size of MPs was the main impact factor, and the category of MPs had no significant effect on the coagulation. After operating condition optimization, the removal efficiency of MPs with size ≥13 μm could reach >70 % by PAC and PAM. During coagulation process, electrical neutralization of PAC played the most important role, the adsorption bridging and net sweeping of PAM could assistant the coagulation.

3D computational fluid dynamics-based analysis of water transfer characteristics of hollow fiber membrane for gas-to-gas membrane humidifier

Water in a proton exchange membrane fuel cell is the main factor determining its performance and durability. A humidifier provides water vapor to regulate the humidity of the fuel cell and enable proper operation. The water transfer properties of membranes are investigated through experiments, and simulations enable faster prediction and optimization of various operating conditions. In this study, a numerical simulation model using the diffusion coefficient empirical formula was developed to calculate the water vapor transport. User-defined function codes are applied to predict mass transfer using the concentration difference between the wet and dry surfaces of the membrane. The results were analyzed by the water transfer rate, mass fraction, and pressure characteristics of the influence of flow rate, pressure, temperature, humidity, and the number of membranes of 9 or 21. The analysis model predicted the experimental results with high reliability of R-square 0.96. It was confirmed that a high flow rate increased the outlet water transfer flux, and an increase in the tube decreased the water transfer flux.

PROSPECTS OF APPLICATION OF D-AMINO ACID TRANSAMINASE FROM AMINOBACTERIUM COLOMBIENSE FOR (R)-SELECTIVE AMINATION OF α-KETOACIDS

D-amino acid transaminase from Aminobacterium colombiense was applied for (R)-selective amination of 2-oxobutyrate, 2-oxovalerate and 2-oxo-4-phenylbutyrate to produce unnatural D-amino acids - D-homoalanine, D-norvaline and D-homophenylalanine. To increase the product yield of D-amino acids, a one-pot three-enzyme system was developed. The system included transaminase from A. colombiense, (R)-2-hydroxyglutarate dehydrogenase and glucose dehydrogenase and effectively shifted the equilibrium of transamination reaction toward the products. The system functioned in both neutral and slightly alkaline pH. We found that at high substrate concentrations (500 mM) transaminase from A. colombiense was inhibited by the products accumulated in the system. The optimization of operational conditions of the three-enzyme system led to the following yields of the target products: 435 mM D-homoalanine, 320 mM D-norvaline and 47,5 mM D-homophenylalanine; the enantiomeric excess of produced D-amino acids exceeded 99,5%

Experimental study on a unitized regenerative fuel cell operated in constant electrode mode: Effect of cell design and operating conditions

Constant electrode (CE) operation of a unitized regenerative fuel cell (URFC) facilitates the optimization of each electrode. In this work, bipolar plates (BPPs) with different flow fields (FFs) are assessed, and a graphite BPP is compared with a titanium BPP in the cathode. Platinum coated titanium felt and carbon cloth and paper gas diffusion layers (GDLs) are tested in the cathode. The carbon BPP and GDLs operated with higher ohmic resistance than the titanium alternatives. However, the titanium GDL caused flooding in FC mode. Carbon GDLs can be applied in the cathode, where carbon paper operated with higher performance than carbon cloth. Titanium GDL is still required in the anode to resist the corrosive environment. A double-serpentine FF in the cathode and a parallel design in the anode were applied. Optimization of the URFC operating conditions under FC mode provided the best results at 80 °C, 2 barabs, with saturated air and dry hydrogen and stoichiometry ratios of 2 and 8. This resulted in a round-trip efficiency of 56% at 0.1 A cm−2, 48% at 0.3 A cm−2 and 22% at 1 A cm−2. In comparison, 56%, 52% and 37% were obtained with a discrete regenerative fuel cell (DRFC).

Novel Intelligent System Based on Automated Machine Learning for Multiobjective Prediction and Early Warning Guidance of Biogas Performance in Industrial-Scale Garage Dry Fermentation

Industrial-scale garage dry fermentation systems are extremely nonlinear, and traditional machine learning algorithms have low prediction accuracy. Therefore, this study presents a novel intelligent system that employs two automated machine learning (AutoML) algorithms (AutoGluon and H2O) for biogas performance prediction and Shapley additive explanation (SHAP) for interpretable analysis, along with multiobjective particle swarm optimization (MOPSO) for early warning guidance of industrial-scale garage dry fermentation. The stacked ensemble models generated by AutoGluon have the highest prediction accuracy for digester and percolate tank biogas performances. Based on the interpretable analysis, the optimal parameter combinations for the digester and percolate tank were determined in order to maximize biogas production and CH4 content. The optimal conditions for the digester involve maintaining a temperature range of 35–38 °C, implementing a daily spray time of approximately 10 min and a pressure of 1000 Pa, and utilizing a feedstock with high total solids content. Additionally, the percolate tank should be maintained at a temperature range of 35–38 °C, with a liquid level of 1500 mm, a pH range of 8.0–8.1, and a total inorganic carbon concentration greater than 13.8 g/L. The software developed based on the intelligent system was successfully validated in production for prediction and early warning, and MOPSO-recommended guidance was provided. In conclusion, the novel intelligent system described in this study could accurately predict biogas performance in industrial-scale garage dry fermentation and guide operating condition optimization, paving the way for the next generation of intelligent industrial systems.

Machine learning assisted predictions for hydrogen storage in metal-organic frameworks

Metal organic frameworks (MOFs) have been studied vastly for hydrogen storage purposes due to their unique properties. In the present work hydrogen storage capacity is modeled using machine learning approaches including Multi-layer Perceptron (MLP), Support Vector Machines (SVM), Random Forest (RF), CatBoost, LightGBM, XGBoost, and Committee Machine Intelligence System (CMIS) trained on experimental data gathered from various experimental studies. CMIS model shows the best results with R2=0.982 and Root Mean Square Error = 0.088. Additionally, this study uses the Leverage method to detect and eliminate suspected data points in order to improve predictability. Only 2.04% of data points are detected as suspected data points. Sensitivity analysis demonstrates that surface area, pore volume, pressure, and temperature have almost the same contribution on hydrogen storage. The findings of this research offer a valuable model for MOF selection and optimization of operational conditions in hydrogen storage processes that utilizes MOFs.

Techno-Economic Optimization of SOC Design and Operating Conditions in a Solid Oxide Fuel Cell-Gas Turbine Hybrid System

Solid oxide fuel cell-gas turbine (SOFC-GT) hybrid systems can reach exceptionally high fuel-to-electricity conversion efficiencies while emitting virtually zero criteria pollutants. Due to these characteristics and their fuel-flexibility, SOFC-GT hybrid systems are seen as a key technology in sustainable power generation. In this work we explore SOFC cell design parameters that can synergistically reduce thermal stress and cost, as well as system-level design strategies to maximize economic performance. Results show that NG-fueled hybrid systems can reach efficiencies of 75%-LHV at a cost-of-electricity of 77.73 $/MWh. A similar biogas system with integrated anaerobic digester and biogas upgrading resulted in an efficiency of 53%-LHV and a cost-of-electricity of 137.19 $/MWh.

Investigation on key geometries optimization and effect of variable operating conditions of a transcritical R744 two-phase ejector

There was no literature that involved the combined investigation on the key geometries optimization and the effect of variable operating conditions (temperature, pressure and dryness fraction of primary and secondary flows) for a R744 two-phase ejector. In this paper, CFD simulation on geometries optimization and effect of variable operating conditions of a transcritical R744 two-phase ejector was carried out for the first time. Firstly, each of three geometries of area ratio (AR), nozzle exit position (NXP) and constant-area mixing chamber length (L2) was optimized to determine their relative sensitivity on ejector performance. Then, two or three geometries under different optimization orders were optimized. Finally, the effects of temperature, pressure and dryness fraction of primary and secondary flows as well as back pressure on ejector performance were analyzed based on the optimal ejector geometries. The results showed that: (1) the relative sensitivity of entrainment ratio (ER) to AR is the highest with value of 44.56%, followed by NXP and L2; (2) optimizing two or three of these parameters under different optimization sequences can achieve certain optimization effect with ER improvement within 5.96%–33.91%, but the result depends on the optimization order; (3) the effect of dryness fraction of the primary flow on the ejector performance is greater than that of temperature; (4) the change of secondary flow pressure has a greater impact on the ejector ER as compared to the dryness fraction of the secondary flow; (5) not only increasing the primary and secondary flow pressure but also reducing the back pressure is conducive to improving the ejector performance.

Red Fruit Juice Concentration by Osmotic Distillation: Optimization of Operating Conditions by Response Surface Methodology.

Osmotic distillation (OD) was implemented at laboratory scale to concentrate a red fruit juice produced from a blend of blood orange, prickly pear, and pomegranate juice. The raw juice was clarified by microfiltration and then concentrated by using an OD plant equipped with a hollow fiber membrane contactor. The clarified juice was recirculated on the shell side of the membrane module, while calcium chloride dehydrate solutions, used as extraction brine, were recirculated on the lumen side in a counter-current mode. The influence of different process parameters, such as brine concentration (20, 40, and 60% w/w), juice flow rate (0.3, 2.0, and 3.7 L min-1), and brine flow rate (0.3, 2.0, and 3.7 L min-1) on the performance of the OD process in terms of evaporation flux and increase in juice concentration, was investigated according to the response surface methodology (RSM). From the regression analysis, the evaporation flux and juice concentration rate were expressed with quadratic equations of juice and brine flow rates, as well as the brine concentration. The desirability function approach was applied to analyse the regression model equations in order to maximize the evaporation flux and juice concentration rate. The optimal operating conditions were found to be 3.32 L min-1 brine flow rate, 3.32 L min-1 juice flow rate, and an initial brine concentration of 60% w/w. Under these conditions, the average evaporation flux and the increase in the soluble solid content of the juice resulted in 0.41 kg m-2 h-1 and 12.0 °Brix, respectively. Experimental data on evaporation flux and juice concentration, obtained in optimized operating conditions, resulted in good agreement with the predicted values of the regression model.

Experimental research on hydrogen-rich syngas yield by catalytic biomass air-gasification over Ni/olivine as in-situ tar destruction catalyst

This research focuses on investigating the air-gasification process of pine sawdust using a fluidized bed unit with Ni/olivine as an in-situ tar destruction catalyst. The goal is to eliminate tar production and obtain high-quality synthesis gas. Consequently, the effects of reaction conditions and catalyst properties on the producer gas composition, the lower heating value (LHV) of the yielded synthesis gas (syngas), char conversion efficiency (CCE), and cold gas efficiency (GE) are comprehensively explored. The conclusions indicate that higher temperatures favor the H2 and CO production and result in an evident decrease of CH4 and C2H4, which is responsible for the increasing gas LHV. The tar capture efficiency (TCE) increases by increasing the equivalence ratio (ER); however, a reverse trend obtains for gas LHV because of a significant decline in the combustible gas contents. The results also reveal that when using Ni/olivine as the bed material, GE reaches an optimum value of 72.4% at equivalence ratio (ER) of 0.21 and then lowers down with a further increase in ER to 0.39 due to the enhanced char combustion reaction. The tar yield (1.3–6.8 g/Nm3) significantly decreases with temperature, whereas H2 concentration (14.1–29.8 vol %), CCE (51.3–89.1%), GE (44.8–86.1%) and gas LHV (5.13–7.19 MJ/Nm3) promote at high temperature. Compared to raw-olivine, the lower heating value (LHV) of the producer gas slightly increases under the same conditions (T = 800 °C and ER = 0.21) when the bed material is Ni/olivine. The conclusions obtained help to provide reliable theoretical guidance for operating condition optimization of biomass catalytic air-gasification with Ni/olivine as bed material in a fluidized bed reactor.

Effect of support salts on apparent performance of Li metal anode in Ethylene carbonate/Ethyl methyl carbonate solvent and dynamic mechanism analysis

Lithium metal batteries (LMB) have received widespread attention due to their high energy density and potential commercial value. The relationship between the rate performance, cycling performance, microstructure of the deposition layer, and SEI of lithium anodes has not yet been elucidated. Here, we investigated the cycling performance and rate characteristics of metal lithium anodes in classic carbonate electrolytes containing different supporting salts. And the microstructure and chemical information of the lithium anode surface were analyzed. In addition, microelectrode technology was used to study the dynamic behavior and reaction of electroplating/stripping lithium process under different polarization conditions (current density), revealing the apparent performance, microscopic visual information, and dynamic causes and mechanisms of SEI. The results indicate that in carbonate electrolytes containing LiBOB and LiPF6, the cycling performance of lithium anodes, the microstructure of the deposition layer, and SEI can be significantly improved. Microelectrode research has revealed a close causal relationship between the stability and coordination of each basic step, including lithium ion mass transfer, interface charge transfer, and surface crystallization kinetics parameters, and the apparent performance of lithium anodes. This correlation can serve as a dynamic evaluation basis for future selection and optimization of operating and manufacturing conditions.

Electrochemical performance study of proton exchange membrane electrolyzer considering the effect of bubble coverage

Bubble dynamics are closely related to the electrochemical performance of a proton exchange membrane electrolyzer (PEMEC). However, tiny bubbles need to be clustered together to affect the electrochemical performance of PEMEC significantly. In this paper, the effect of microscopic bubbles on macroscopic electrochemical properties were assessed by bubble coverage. The bubble dynamics, two-phase flow, and electrochemical performance were captured under different conditions using a high-speed, microscopic visualization experimental system. The results show that various factors influence the two-phase flow pattern. At 60 °C, 1.5 A/cm2 and 5 mL/min, the annular flow occupied 76.8% of the gas phase area, and when the water flow increased to 80 mL/min, the annular flow ratio decreased substantially to 2.7%. The two-phase flow of bubbles in the flow channel showed different flow patterns over time. Under the experimental conditions (60 °C, 20 mL/min, 0.8 A/cm2), the bubble flow pattern experienced the emergence of bubbles, bubble flow, segmental plug flow, annular flow, and final steady state with the occurrence times of 0.15 s, 1.5 s, 5.0 s, 10.5 s, and 21.2 s, respectively. The bubble coverage increased with current density and temperature, while it decreased with the increase of water velocity. In addition, the effects of temperature and water velocity on bubble coverage and PEMEC performance vary in principle. Specifically, higher temperature mainly improves the bubble coverage by increasing the electrochemical performance of PEMEC. In contrast, higher water velocity mainly improves the electrochemical performance of PEMEC by decreasing the bubble coverage. This study elucidates the relationship between microscopic bubbles and macroscopic electrochemical performance, contributing to a better understanding of the processes and principles of bubble effects on the electrochemical performance of PEMEC. The results may provide a theoretical basis and experimental data for operating condition optimization, operating efficiency improvement, multiphase flow study, gas diffusion layer structure, and flow field design of PEMEC.

Fischer-Tropsch wax catalytic cracking for the production of low olefin and high octane number gasoline: Process optimization and heat effect calculation

To produce low olefin gasoline with high octane number by Fischer-Tropsch (F-T) wax fluid catalytic cracking (FCC) process, operating conditions optimization were carried out in the pilot-scale riser and turbulent fluidized bed (TFB) FCC unit. The experimental results in the riser indicated that under the condition of low reaction temperature and regenerated catalyst temperature, large catalyst-to-oil weight ratio (C/O) and long reaction time, the gasoline olefin content could be reduced to 20.28 wt%, but there is large octane number loss owing to a great loss in high octane number olefin. Therefore, a novel FCC process using the TFB reactor was proposed to strengthen the aromatization reaction. The reaction performance of TFB reactor were investigated. The result demonstrated that the TFB reactor has more significant effect in reducing olefins and improving aromatics. At the expense of certain gasoline yield, the gasoline olefin content reduced to 23.70 wt%, aromatics content could increase to 26.79 wt% and the RON was up to 91.0. The comparison of reactor structure and fluidization demonstrated that the TFB reactor has higher catalyst bed density. The reaction heat and coke combustion heat was calculated indicating the feasibility of its industrial application of the TFB process.

Sulfate Reduction in an Upflow Anaerobic Sludge Blanket Bioreactor and Optimization of Operational Conditions: pH, Hydraulic Retention Time, Sulfate Loading Rate, COD/SO42- Ratio

Sulfate Reduction in an Upflow Anaerobic Sludge Blanket Bioreactor and Optimization of Operational Conditions: pH, Hydraulic Retention Time, Sulfate Loading Rate, COD/SO42- Ratio

Cluster-Based Multiobjective Particle Swarm Optimization and Application for Chemical Plants

In multiobjective particle swarm optimization (MOPSO), the global-best particle is randomly selected for each population particle from a nondominated solution set. However, this Roulette wheel-based global particle selection is ineffective for convergence and diversity when the problem has numerous decision variables or a large number of global-best candidates. Thus, this study proposes the cluster-based MOPSO (CMOPSO). In CMOPSO, the similarities between particles are considered when selecting the global-best particle. The cluster for each particle is determined based on the Euclidean distance in the decision or objective space. The proposed approach is demonstrated by applying an operating condition optimization problem to the hydrogen production process. The target process is a representative chemical plant with a large search space and strong nonlinearity. Furthermore, the performance of CMOPSO is assessed by comparing it with that of MOPSO. The results indicate that CMOPSO considered in the decision space exhibits superior performance in terms of convergence and diversity.

Efficiency analysis and operating condition optimization of solid oxide electrolysis system coupled with different external heat sources

Coupling external heat sources effectively reduces energy consumption and improves the efficiency of the solid oxide electrolysis (SOEC) system. While an in-depth analysis of the SOEC systems in different coupling scenarios is still needed. According to the internal heat demand and the temperature of external heat sources, three coupling scenarios are defined in this study, i.e., no heat source coupling (Scenario 1), coupled low-temperature heat source (Scenario 2), and coupled high-temperature heat source (Scenario 3). Firstly, the influence of critical parameters on system efficiency is analyzed from two perspectives, including specific system loss and specific energy consumption. The results present that efficiency η1 mainly increases with the rise of steam utilization. Efficiency η2 is not significantly affected by the parameters and is primarily positively correlated with the fuel electrode steam concentration. Efficiency η3 is negatively related to steam utilization, fuel electrode steam concentration, and fuel electrode flow rate, while positively to stack operating temperature. Meanwhile, for Scenarios 1 and 2, the exothermic state of the stack module should be avoided. Furthermore, the system performance maps and stack operating windows in the three scenarios are obtained by changing multiple operating parameters simultaneously and setting constraints. For Scenarios 1 and 2, high system efficiency, high hydrogen production, and long lifetime cannot be achieved simultaneously, so operating parameters need to be selected at a compromise. For scenario 3, high fuel electrode flow rate and low steam utilization can basically meet the above requirements. Both high stack operating temperature and high fuel electrode steam concentration can improve hydrogen production, while the former is mainly beneficial to efficiency η3, and the latter can improve the three efficiencies. The results obtained can be used not only to choose the optimal working conditions of various external heat sources but also to guide the online control and load regulation during system operation.

Preparation of cellulose tri-acetate membranes for high-alcohol beverages via genetic algorithms and high throughput experimentation

In fermented beverages, volatile esters are trace compounds with a significant effect on the flavour profile. Some of the most important esters in beer are ethyl acetate (solvent-like aroma) and isoamyl acetate (banana aroma). These esters have a defined threshold which, when exceeded, will be experienced as unpleasant upon tasting. Therefore, the industry needs to selectively remove and fractionate esters by means of adsorption and tune the level of esters in the different process streams.Nanofiltration (NF) and Reverse Osmosis (RO) membranes are known to have a high potential towards removal of low molecular weight components from liquid streams. However, membrane preparation depends on several parameters with complex interactions to obtain the targeted membrane performance. Multi-parameter optimization strategies are thus very useful to reduce material consumption, minimize time and labour during the development of a ‘bottom-up’ preparation method. High throughput (HT) filtration techniques in combination with genetic algorithms (GAs) are known to be very powerful to direct such membrane preparation.This optimization strategy is used to obtain cellulose tri-acetate (CTA) membranes for filtration of high-alcoholic beverages towards ethyl acetate and isoamyl acetate depletion. Before the implementation of the proposed strategy, a successful optimization of the HT operating conditions was setup together with a selection of benchmark membranes by screening the performance of various commercially available nanofiltration (NF) and reverse osmosis (RO) membranes.Next, the non-compositional (solvent impregnation, membrane thickness, solvent evaporation time, annealing time and temperature) and compositional parameters (polymer concentration, solvents and additives selection) used during non-solvent induced phase separation (NIPS) preparation of CTA membranes were determined. Finally, CTA membranes were optimized using GAs.

Treatment of tributyl phosphate by fenton oxidation: Optimization of parameter, degradation kinetics and pathway

In nuclear industry, tributyl phosphate (TBP) is used as organic extracting solvent to separate uranium and plutonium. The spent TBP is finally discarded as the radioactive organic waste, which should be treated due to its potential risk. In this study, TBP degradation by Fenton oxidation was investigated in detail, including the optimization of operational conditions, degradation kinetics and degradation products. The optimal conditions for TBP degradation (per 10 ml) by Fenton oxidation was: 95 °C, pH 2, 150 ml 30% H2O2, and 105 ml 0.2 M Fe(II). H2O2 was continuously added with the flow rate of 0.5 ml/min, Fe(II) was intermittently added with the flow rate of 3 ml/10 min. The oil phase volume decreased with time and completely disappeared at the third hour. In contrast, the COD in water phase increased firstly and then decreased. At the end of the experiments, the COD achieved 23.8 g/L. The detection of phosphorus in water phase further confirmed the decomposition of TBP. Mono-butyl phosphate and di-butyl phosphate were identified as the intermediate products of TBP degradation. In addition, other four degradation products with the same m/z of 154 were identified, which may be derived from the hydroxylation of mono-butyl phosphate and di-butyl phosphate. Based on the degradation products, the degradation pathway of TBP was proposed. This study could provide an insight into the TBP degradation by Fenton oxidation, and an potential strategy for treating the spent radioactive organic solvent.

Improving Operational Flexibility of Integrated Energy Systems Through Operating Conditions Optimization of CHP Units

Improving Operational Flexibility of Integrated Energy Systems Through Operating Conditions Optimization of CHP Units