Favorable Operating Conditions Research Articles

Directional production of even carbon volatile fatty acids from peanut meal: effects of initial pH and hydraulic residence time

In this study, peanut meal was used as the substrate for the continuous production of even carbon volatile fatty acids (ECFA) through anaerobic fermentation. First, a continuous stirred reactor (CSTR) was started by adjusting the initial pH to acclimate the related bacteria, and then the hydraulic residence time (HRT) was optimized. The effects of different initial pH and HRT on the potential of ECFA production by peanut meal fermentation, the transformation and utilization of main organic compounds, and the composition and replacement of microbial community structure behind it were investigated. The results showed that ECFA was the dominant factor in the acid production of peanut meal fermentation, and alkaline pH and HRT = 6 d were the more favorable operating conditions for the hydrolysis and acidification of peanut meal. The average concentration of total volatile fatty acids (TVFAs) obtained was 15,249.50 mg/L, and the content of ECFA varied from 88.51% to 96.27%, with an average ratio of 92.55%. This operation condition drove the formation of microbial community structure, mainly including Prepotella, Tepididimicrobium, Anaerosalibacter, and Igatzschineria, which were favorable for ECFA production, reflecting the potential of using peanut meal for targeted production of ECFA.

Degradation Investigation of Electrocatalyst in Proton Exchange Membrane Fuel Cell at a High Energy Efficiency.

The development of high efficient stacks is critical for the wide spread application of proton exchange membrane fuel cells (PEMFCs) in transportation and stationary power plant. Currently, the favorable operation conditions of PEMFCs are with single cell voltage between 0.65 and 0.7 V, corresponding to energy efficiency lower than 57%. For the long term, PEMFCs need to be operated at higher voltage to increase the energy efficiency and thus promote the fuel economy for transportation and stationary applications. Herein, PEMFC single cell was investigated to demonstrate its capability to working with voltage and energy efficiency higher than 0.8 V and 65%, respectively. It was demonstrated that the PEMFC encountered a significant performance degradation after the 64 h operation. The cell voltage declined by more than 13% at the current density of 1000 mA cm−2, due to the electrode de-activation. The high operation potential of the cathode leads to the corrosion of carbon support and then causes the detachment of Pt nanoparticles, resulting in significant Pt agglomeration. The catalytic surface area of cathode Pt is thus reduced for oxygen reduction and the cell performance decreased. Therefore, electrochemically stable Pt catalyst is highly desirable for efficient PEMFCs operated under cell voltage higher than 0.8 V.

Investigation and Optimization of Diesel Engine Outputs Under Undi Biodiesel-Diesel Strategies

Abstract The present investigation accentuates the impact of Undi biodiesel blended diesel on combustion, performance, and exhaust fume profiles of a single-cylinder, four-stroke diesel engine. Five Undi biodiesel-diesel blends were prepared and tested at four variable loads over a constant speed of 1500 (±10) rpm. The Undi biodiesel incorporation to diesel notably improved the in-cylinder pressure and heat release rate (HRR) of the engine. The higher amount of Undi biodiesel addition enhanced the brake thermal efficiency (BTE) and brake specific energy consumption (BSEC) of the engine. In addition, the Undi biodiesel facilitated the reduction of the major pollutants, such as unburned hydrocarbon (UHC), carbon monoxide, and particulate matter (PM) emissions with slightly higher oxides of nitrogen emissions of the engine. To this end, a trade-off study was introduced to locate the favorable diesel engine operating conditions under Undi biodiesel-diesel strategies. The optimal results of the engine operation were found to be 32.65% of brake thermal efficiency, 1.21 g/kWh of brake specific cumulated oxides of nitrogen and unburned hydrocarbon, 0.94 g/kWh of brake specific carbon monoxide (BSCO), and 0.32 g/kWh of brake specific particulate matter (BSPM) for 50% (by volume) Undi biodiesel blend at 5.6 bar brake mean effective pressure (BMEP) with a relative closeness value of 0.978, which brings up the pertinence of the trade-off study in diesel engine platforms.

Use of Wire Matrix Inserts in Thermosiphon Reboilers in the Lower Operating Range

AbstractTurbulators are applied to increase the thermal efficiency of heat transfer units. The additional pressure drop can be challenging for the self‐circulation of thermosiphon reboilers. Thus, the effects of hiTRAN®‐wire matrix inserts for the boiling of water and a water/glycerol mixture were investigated herein, using the performance of a thermosiphon reboiler with plain tubes as a reference. The reboiler was operated at sub‐atmospheric pressures, small driving temperature differences, and under flooded conditions. Favorable and unfavorable operating conditions for using inserts were specified. Especially for the water/glycerol mixture, significant improvements of self‐circulation and heat transfer up to six times compared to the plain tube reference were observed, allowing an operation of thermosiphon reboilers at smaller driving temperature differences under sub‐atmospheric pressures.

Modelado multiescala de un biorreactor de membrana para el tratamiento de aguas residuales con grasas y aceites

Membrane bioreactors represent an attractive alternative for food industries wastewater treatment. This type of reactors comprise an aerobic tank (where the biochemical reactions take place) and a membrane tank (where the final filtration process occurs). Mathematical modeling of these systems is a practical tool for the design, control and optimization of wastewater treatment plants. Among the modeling approaches, there is no mathematical model that is specifically designed for membrane bioreactors, and that captures the hierarchical nature of these systems. In the present work, new mathematical models for mass and momentum transport are derived from the fundamental equations at the continuum level. With the use of the volume averaging method, effective medium models for both the aerobic and membrane tanks were developed. This modeling approach has the advantage that the coefficients involved in the model can be predicted from closure schemes, without representing a demanding computational effort. This deterministic model allows predicting the most favorable design and operating conditions. Additionally, numerical simulations of these models give rise to a better understanding of the involved mass transport mechanisms in the membrane tank, this is achieved through the prediction of the fluid velocity, and the dynamics of the total mass flux and the concentration at each point in the tank. The models derived here are valuable because they allow analyzing the effect of each (operational and/or design) parameter over the dynamics of long-chain fatty acids and oxygen concentrations.

A mathematical approach of the entropic index applied to chemical systems

AbstractThis article deals with the mathematical efforts for developing an entropic performance index, taking into account both the different entropy concepts for establishing it, including Communication Theory, and its practical application. To illustrate the performance of the index developed, two different approaches were applied to a reactive system that consists of multiple generic reactions. The reactive system was optimized using the strategy of generating the minimum entropy rate and then the index was applied to check the progress of the process. The index increased from 0.2146 to 0.549, thus indicating a better result and, consequently, more favourable operating conditions. Additionally, a more refined procedure was carried out, which generated a maximum value for the index of 0.6174. To reveal the efficiency of this index, classic indicators based on trade‐offs between conversion and yield were also used to optimize the reactive system, which resulted in an index value of 0.6129. A detailed comparative analysis showed a convergence of the optimal regions, given by the classical method and that established by the entropy index. However, the optimal operating points are different, which can be explained by the interactions between the components considered by the entropic index. The conclusion to be drawn is that the results based on the entropy index describe the real system more appropriately, and therefore its performance is superior.

Optimization of Bench-scale Shipboard STP Operating Conditions for Artificial Wastewater Treatment

This study intended to optimize the favorable operating conditions for Bench-scale shipboard STP by using artificial wastewater. For this purpose, the previously developed advanced sequence batch reactor and membrane bioreactor (MBR) combined system by our group was adopted at Bench-scale to study the applicability of this system for wastewater treatment and for the removal of nutrient and organic matter. The COD:T-N:T-P ratios of the influent were adjusted at 10:3:1 and the aeration during MBR process was provided at 7 min aeration and 3 min stop. The operating conditions were optimized by measuring the removal efficiencies of CODcr, T-P, and T-N at different time intervals of mixing and aeration. The operating conditions included mixing and aeration for 90:30, 80:40, 70:50, and 60:60 min, respectively. The optimal removal efficiencies were achieved under mixing and aeration for 70 min and 50 min, respectively, using Bench-scale shipboard STP. The results of the present study were in accordance with the MEPC.227(64) regulations for the removal of CODcr, phosphorus, and nitrogen for advanced shipboard wastewater treatment. A further study is required to evaluate a detailed mechanism of shipboard STP to justify the MEPC.227(64) regulations.

Finding optimal transmission strategy for intra‐WBAN communications

This Letter proposes a stochastic model of the wearable sensor nodes of a wireless body area network (WBAN) based on Markov decision process (MDP). The proposed technique tackles the problem of maximising the likelihood of data transmission while minimising the computational cost and energy. Suitable transmission strategies subject to the energy level of the nodes and channel conditions are needed to be investigated to strike a balance between network lifetime and packet delivery ratio. MDP formulation of the problem is solved offline to find out the optimal transmission strategies for the representative input conditions. The results of this offline computation approach can directly map to optimal transmission policies for intra-WBAN communications. The experimental results demonstrate the robustness of the proposed scheme in handling both favourable and unfavourable operating conditions.

Effective photochemical treatment of a municipal solid waste landfill leachate.

This work aimed at studying the photochemical treatment of a landfill leachate using ultraviolet light, hydrogen peroxide, and ferrous or ferric ions, in a batch recycle photoreactor. The effect of inorganic carbon presence, pH, initial H2O2 amount (0–9990 mg L-1) as well as Fe(II) (200–600 ppm) and Fe(III) (300–700 ppm) concentrations on the total carbon removal and color change was studied. Prior to the photochemical treatment, a pretreatment process was applied; inorganic nitrogen and inorganic carbon were removed by means of air stripping and initial pH regulation, respectively. The leachate sent subsequently for photochemical treatment was free of inorganic carbon and contained only organic carbon with concentration 1200±100 mg L-1 at pH 5.1–5.3. The most favorable concentrations of H2O2 and ferric ions for carbon removal were 6660 mg L-1 and 400 ppm, respectively. Adjusting the initial pH value in the range of 2.2–5.3 had a significant effect on the organic carbon removal. The photo-Fenton-like process was more advantageous than the photo-Fenton one for leachate treatment. By applying the most favorable operating conditions, 88.7% removal of total organic carbon, 100% removal of total inorganic carbon, 96.5% removal of total nitrogen, and 98.2% color removal were achieved.

Contemporary Separation Processes for Insulation of Plant Extract for Food and Pharmaceutical Process Engineering

We live in a time that imposes a general ecological struggle for a healthier and better life. Exhaustive lifestyles require a rapid increase in research in the food industry, in order to improve food quality and to respond to the demands of the human organism. Consumers demand from the modern chemical industry to develop new technologies that will fit with the general modern and environmentally friendly trends in the world, that produce finished products in accordance with strict ecological criteria (Lisichkov et al., 2017). The significance and prospect of natural antioxidants in the production of healthy food is indicated by a large number of scientists and nutritionists around the world. In pharmacy, a relationship was established between free oxygen radicals and their influence on the pathogenesis of arteriosclerosis, cancer, increased blood pressure and heart disease on the one hand, and antioxidants and free radicals on the other (Lisichkov and Najdenova, 2005). The problem of isolating natural plant antioxidants is quite complicated. In fact, they are particularly sensitive to elevated temperatures, oxygen from the air, light and various types of organic solvents. Hence, there is a need for finding alternative separation procedures for the isolation of bioactive components (Najdenova and Lisichkov, 2005). In contrast to classical extraction, alternative extraction methods (ultrasonic extraction, microwave extraction, supercritical fluid extraction) have a number of advantages over classical, primarily of practical and ecological character. These unconventional extraction procedures take place under favorable operational conditions (low temperatures) and with the use of safe, green solvents, whereby a large amount of energy for regenerating solvents is not used (Lisichkov and Kuvendziev, 2009). The purpose of this work is to present the application of precise process ecotechnological procedures for the isolation of bioactive compounds from selected matrices of plant origin.

Effective usage of 2D MXene nanosheets as solid lubricant – Influence of contact pressure and relative humidity

Newly emerging Ti3C2Tx–nanosheets (MXenes) have attracted considerable attention in energy storage, catalysis and, more recently, tribology. MXene nanosheets are characterized by a weakly-bonded multi-layered structure with self-lubricating ability, making them a suitable candidate for solid lubrication. This contribution aims at addressing for the first time their application in higher loaded steel/steel dry sliding contacts by investigating the influence of contact pressure and relative humidity on friction and wear performance. Compared to the uncoated reference, a 2.3-fold friction reduction and a 2.7-fold reduction of the wear volume were verified for MXene-coated specimens for moderate contact pressures and low relative humidity. This was due to the in-situ formation of a compacted tribo-film consisting of densified Ti3C2Tx–nanosheets. In contrast, too high pressures induced a partial rupture of the wear-protecting tribo-layer, thus reducing its beneficial effects. Additionally, no beneficial effects regarding friction and/or wear were found at higher relative humidities, which was correlated with the expansion of the basal spacings. Therefore, this study summarizes favorable operating conditions for MXene nanosheets when used as solid lubricant to improve friction and/or wear thus making them excellent candidates for advanced, next-generation solid lubricants.

Performance evaluation and process simulation for synergetic removal of NOx, CO2 and PM using green alkaline solution in a high-gravity rotating packed bed

The high-gravity rotating packed bed (HiGee RPB) developed here can simultaneously remove multiple air pollutants using alkaline solution, thus achieving the flue gas deep purification. The electric-arc-furnace reduction slag (EAFRS) leachate was then used as the alkaline absorbent in HiGee RPB for assessing the removal efficiencies of nitrogen oxide (NOx), carbon dioxide (CO2) and particulate matters (PM) from flue gas. The results indicated the changes to the CO2 capture was enhanced by increasing the initial PH value of the alkaline solution. In contrast, this value has no significant influence on NOx removal. The suitable NOx removal efficiency ranged from 90.9% to 97.09% at the liquid-to-gas (L/G) ratio of 0.01 and high gravity factor of 58.9 to 368. The precipitated calcium carbonate gained from carbonation via HiGee process exhibited similar physical properties to commercial products. In addition, 95.9% of PM removal efficiency was achieved at the L/G ratio and high gravity factor of 0.03 and 235.4, respectively. This treatment furthermore demonstrated a high efficiency for PM collection of over 90% and balanced the energy consumption. Based on the result, an Aspen simulation and a preliminary cost-benefit analysis were carried out to develop a mass-balance model for this system and determine the favorable operating conditions.

Optimization of FX-70 refrigerant evaporative heat transfer and fluid flow characteristics inside the corrugated tubes using multi-objective genetic algorithm

In this study, the heat transfer optimization (evaporation) and the specification of the FX-70 zeotropic refrigerant flow inside a corrugated pipe have been investigated. Despite the low HTC (HTC), this type of refrigerant is highly applicable in low or medium temperature engineering systems during the evaporation process. To eliminate this defect, high turbulence and proper mixing are required. Therefore, using heat transfer (HT) augmentation methods will be necessary and effective. In order to find the most favorable operating conditions that lead to the optimum combination of pressure drop (PD) and HTC, empirical data, neural networks, and genetic algorithms (GA) for multi-objective (MO) (NSGA II) are used. To investigate the mentioned cases, the geometric parameters of corrugated pipes, vapor quality, and mass velocity of refrigerant were studied. The results showed that with vapor quality higher than 0.8 and corrugation depth and pitch of 1.5 and 7 mm, respectively, we would achieve the desired optimum design.

Monitoring and prediction of big process data with deep latent variable models and parallel computing

Process monitoring and quality prediction are crucial for maintaining favorable operating conditions and have received considerable attention in previous decades. For majority complicated cases in chemical and biological industrial processes with particular nonlinear characteristics, traditional latent variable models, such as principal component analysis (PCA), principal component regression (PCR), partial least squares (PLS), may not work well. In this paper, various nonlinear latent variable models based on autoencoder (AE) are developed. In order to extract deeper nonlinear features from process data, the basic shallow AE models are extended to the deep latent variable models, which provides a deep generative structure for nonlinear process monitoring and quality prediction. Meanwhile, with the ever increasing scale of industrial data, the computational burden for process modeling and analytics has becoming more and more tremendous, particularly for large-scale processes. To handle the big data problem, the parallel computing strategy is further applied to the above model, which partitions the whole computational task into a few sub-tasks and assigns them to parallel computing nodes. Then the parallel models are utilized for process monitoring and quality prediction applications. The effectiveness of the developed methods are evaluated through the Tennessee Eastman (TE) benchmark process and a real-life industrial process in an ammonia synthesis plant (ASP).

Evaluation of the Thermal Stability and Surface Characteristics of Thermoplastic Polyurethane V-Belt.

This article proposes thermography as a non-contact diagnostic tool for assessing drive reliability. The application of this technique during the operation of the belt transmission with a heat-welded thermoplastic polyurethane V-belt was presented. The V-belt temperature changes depending on the braking torque load at different values of the rotational speed of the active pulley, which were adopted as diagnostic characteristics. In this paper, the surface morphology of the polyurethane (PU) belts was assessed on the basis of microscopic and hardness tests. A surface roughness tester was used to evaluate the surface wear. The surface morphology and topography of the materials was determined by scanning electron microscopy (SEM) and optical microscopy. It was found that the most favorable operating conditions occurred when the temperature values of active and passive connectors were similar and the temperature difference between them was small. The mechanical and structure results indicate that the wear of the PU belt was slight, which provided stability and operational reliability for V-belt transmission. The microscopic images lacked clear traces of cracks and scratches on the surface, which was confirmed by the SEM observations.

Designing Advanced Catalysts for Energy Conversion Based on Urea Oxidation Reaction.

Urea oxidation reaction (UOR) is the underlying reaction that determines the performance of modern urea-based energy conversion technologies. These technologies include electrocatalytic and photoelectrochemical urea splitting for hydrogen production and direct urea fuel cells as power engines. They have demonstrated great potentials as alternatives to current water splitting and hydrogen fuel cell systems with more favorable operating conditions and cost effectiveness. At the moment, UOR performance is mainly limited by the 6-electron transfer process. In this case, various material design and synthesis strategies have recently been reported to produce highly efficient UOR catalysts. The performance of these advanced catalysts is optimized by the modification of their structural and chemical properties, including porosity development, heterostructure construction, defect engineering, surface functionalization, and electronic structure modulation. Considering the rich progress in this field, the recent advances in the design and synthesis of UOR catalysts for urea electrolysis, photoelectrochemical urea splitting, and direct urea fuel cells are reviewed here. Particular attention is paid to those design concepts, which specifically target the characteristics of urea molecules. Moreover, challenges and prospects for the future development of urea-based energy conversion technologies and corresponding catalysts are also discussed.

Data-Driven Model Predictive Monitoring for Dynamic Processes

Process monitoring plays an important role in maintaining favorable process operation conditions and is gaining increasing attention in both academic community and industrial applications. This paper proposes a data-driven model predictive fault detection method to achieve efficient monitoring of dynamic processes. First, a measurement sample is projected into a dominant latent variable subspace that captures main variance of the process data and a residual subspace. Then the dominant latent variable subspace is further decomposed as a dynamic feature subspace and a static feature subspace. A fault detection residual is generated in each subspace, and corresponding monitoring statistic is established. By using the model predictive monitoring scheme, not only the status of a process but also the type of a detected fault, namely a dynamic feature fault or a static feature fault, can be identified. Effectiveness of the proposed data-driven model predictive monitoring scheme is tested on a lab-scale distillation process.

Method To Configure a Multitube Membrane Reactor with Cooling Based on a Three-Dimensional Asymmetric Unit

Cooling tubes within a membrane reactor can help to maintain favorable operating conditions; however, the addition of cooling tubes significantly increases the complexity and number of alternatives for the internal layout. A method is proposed to configure a reactor with both membrane and cooling multitubes based on the results of a simplified asymmetric unit. This simplified triangular unit is used to preoptimize the operating conditions as well as provide guidelines for the relative dimensions of the packed bed, membrane, and cooling chambers. Cooling tubes with smaller diameters were placed next to the exterior wall to reduce the impact of having to break the central pattern. Furthermore, for this hexagonal multitube pattern, an external hexagonal wall significantly improved the reactor performance by keeping favorable temperature profiles throughout the cross section of the reacting chamber not just those regions near the center of the reactor.

Biosorption of direct black dye by cassava root husks: Kinetics, equilibrium, thermodynamics and mechanism assessment

The objective of this study was to evaluate the removal of the direct black ECO TFA (DBET) dye from tannery industry by cassava root husks (CRH) from starch industry as a biosorbent material. For this, CRH biosorbent was characterized, in terms of textural parameters and functional groups. Based on the results, it was verified that CRH is a nonporous material, also DBET dye adsorption takes place, especially, in hydroxyl and carboxyl groups abundantly present in CRH biosorbent. Preliminary adsorption tests evidenced the most favorable operational conditions, namely, particle size mixture, lower temperature 30 °C, higher stirring speed 150 rpm (due to lower diffusional resistances) and pH 2.0 (favoring electrostatic interactions between DBET dye and CRH biosorbent). Adsorption kinetics studies evidenced favorable kinetics, described by the pseudo-second-order model, indicating that the adsorption itself as the of the overall mass transfer process, rather than diffusional ones. Equilibrium data was described by Langmuir isotherm within the evaluated temperature range (30–50 °C). Nevertheless, near-linear isotherm profiles (similar to Henry’s law) were observed. Thermodynamic parameters indicated an exothermic and physisorption process (∆Hads = −14.73 kJ mol-1). Overall, equilibrium results along with functional groups characterization and identified intermolecular interactions (e.g. electrostatic, hydrophobic and H-bond) point out that multilayer sorption mechanism most likely rules the DBET dye uptake by the CRH biosorbent. Thus, the results evidence the potential of CRH biosorbent for direct dyes removal, given the observed technical-operational features along with its renewable and residual characteristics, which provides both economic and environmental advantages for such biomaterial.

A Numerical and Experimental Study on the Fabrication GaN Films by Chemical Vapor Deposition

Abstract Computational modeling and simulation are employed to study a rotating susceptor vertical impinging chemical vapor deposition (CVD) reactor to predict GaN film deposition. Many metal-organic chemical vapor deposition reactor manufacturers use prior experience to design and fabricate CVD reactors without a fundamental basis for the process and information on the optimal conditions for the deposition. Through trial and error, they fine tune the gas flow parameters, heater temperatures, chamber pressure, and concentration of species gases for optimal growth. However, expensive raw precursor gas and time are wasted through this method. A computational model is an important step in the CVD reactor design and GaN growth prediction. It can be used to model and optimize the reactor to yield favorable operating conditions. In this paper, a simple geometry consisting of a rotating susceptor and flow guide is considered. The focus is on gallium nitride (GaN) thin films. The study shows how the computational model can benefit reactor design. It also presents comparisons between model prediction results and experimental data from a physical, practical, system. Commercially available software is used, with appropriate modifications, and the results obtained are discussed in detail.