Effects Of Different Operating Conditions Research Articles

Energy and exergo-economic analysis of a parallel feed multi-effect system integrated with humidification–dehumidification system for brine recovery

Desalination technologies reject large amounts of brine with significant value back to sea. The concept of hybridization of different desalination technologies has proven that it can be effective in terms of reducing rejected brine and increasing the freshwater production rate as well as reducing the freshwater cost. In this work, brine recovery to improve water production through a simple modified configuration of integrating a multi-effect desalination (MED) system with humidification–dehumidification system (HDH). The rejected brine of the MED system is used as the feed for the HDH system without the need for preheating the rejected brine since it leaves the MED at a suitable temperature for HDH application. The study focuses on investigating the effect of different operating conditions on the increase in system freshwater production rate and recovery ratio as well as the exergetic efficiency. Parameters investigated include steam temperature, feed salinity, number of brine streams, cooling water flow rate, and ambient temperature. An exergo-economic analysis has also been conducted using the cost flow method to evaluate the freshwater production cost for the modified system. Results indicate that the integration of HDH can increase the water production rate by a maximum of 7.82% and produce fresh water at 2.08 $/m3 compared to 2.094 $/m3 when using the standalone system under the same conditions.

Acclimation of electroactive biofilms under different operating conditions: comprehensive analysis from architecture, composition, and metabolic activity.

Electroactive biofilms (EABs) have aroused wide concern in waste treatment due to their unique capability of extracellular electron transfer with solid materials. The combined effect of different operating conditions on the formation, microbial architecture, composition, and metabolic activity of EABs is still unknown. In this study, the impact of three different factors (anode electrode, substrate concentration, and resistance) on the acclimation and performance of EABs was investigated. The results showed that the shortest start-up time of 127.3 h and highest power density of 0.84 W m-2 were obtained with carbon brush as electrode, low concentration of substrate (1.0 g L-1), and 1000 Ω external resistance (denoted as N1). The EABs under N1 condition also represented strongest redox capacity, lowest internal resistance, and close arrangement of bacteria. Moreover, the EABs cultured under different conditions both showed similar results, with direct electron transfer (DET) dominated from EABs to anode. Microbial community compositions indicated that EABs under N1 condition have lowest diversity and highest abundance of electroactive bacteria (46.68%). Higher substrate concentration (3.0 g L-1) promoted the proliferation of some other bacteria without electroactivity, which was adverse to EABs. The metabolic analysis showed the difference of genes related to electron transfer (cytochrome C and pili) and biofilm formation (xap) of EABs under different conditions, which further demonstrated the higher electroactivity of EABs under N1. These results provided a comprehensive understanding of the effect of different operating conditions on EABs including biofilm formation and electrochemical activity.

Enhanced chemical deacidification of crude soybean oil by rotating packed bed reactor

Chemical deacidification is a key process for vegetable oil refining, but its efficiency is limited by the liquid–liquid mass transfer performance of reaction system. Here, a mathematical model containing mass transfer and reactions for the chemical deacidification process was developed at first. The modeling results quantitatively revealed the effect of mass transfer on deacidification efficiency and deacidification reaction time. Then, rotating packed bed (RPB) reactor was firstly applied to enhance the chemical deacidification due to its excellent heterogonous mass transfer performance. The effect of different operating conditions on the deacidification efficiency was systematically investigated. Under the optimal conditions, 99.85% deacidification efficiency was obtained after continuous treatment by RPB reactor. Comparing with traditional stirred tank reactor, the reaction time was reduced from tens of minutes to less than 1 s in RPB. Meanwhile excess alkali consumption was avoided. This work demonstrates an efficient and promising technique for vegetable oil refining.

Estimation of the flow rate of pyrolysis gasoline, ethylene, and propylene in an industrial olefin plant using machine learning approaches

Light olefins, as the backbone of the chemical and petrochemical industries, are produced mainly via steam cracking route. Prediction the of effects of operating variables on the product yield distribution through the mechanistic approaches is complex and requires long time. While increasing in the industrial automation and the availability of the high throughput data, the machine learning approaches have gained much attention due to the simplicity and less required computational efforts. In this study, the potential capability of four powerful machine learning models, i.e., Multilayer perceptron (MLP) neural network, adaptive boosting-support vector regression (AdaBoost-SVR), recurrent neural network (RNN), and deep belief network (DBN) was investigated to predict the product distribution of an olefin plant in industrial scale. In this regard, an extensive data set including 1184 actual data points were gathered during four successive years under various practical conditions. 24 varying independent parameters, including flow rates of different feedstock, numbers of active furnaces, and coil outlet temperatures, were chosen as the input variables of the models and the outputs were the flow rates of the main products, i.e., pyrolysis gasoline, ethylene, and propylene. The accuracy of the models was assessed by different statistical techniques. Based on the obtained results, the RNN model accurately predicted the main product flow rates with average absolute percent relative error (AAPRE) and determination coefficient (R2) values of 1.94% and 0.97, 1.29% and 0.99, 0.70% and 0.99 for pyrolysis gasoline, propylene, and ethylene, respectively. The influence of the various parameters on the products flow rate (estimated by the RNN model) was studied by the relevancy factor calculation. Accordingly, the number of furnaces in service and the flow rates of some feedstock had more positive impacts on the outputs. In addition, the effects of different operating conditions on the propylene/ethylene (P/E) ratio as a cracking severity factor were also discussed. This research proved that intelligent approaches, despite being simple and straightforward, can predict complex unit performance. Thus, they can be efficiently utilized to control and optimize different industrial-scale units.

Water liquid distribution in a bioinspired PEM fuel cell

Water management is a key factor in the operation of hydrogen fuel cells since its formation may lead to significant mass transport losses, oxygen diffusion limitation and membrane durability issues. In this work, the effect of different operating conditions on the liquid water distribution inside a 50 cm2 active area bio-inspired PEM fuel cell has been studied. Therefore, a set of experiments was designed varying cell pressure, the reactants relative humidity (anode and cathode), temperature, and cell current density. Liquid water distribution for each operating condition was determined using neutron imaging technique as it has been proved to be an excellent technique for this purpose, including quantitative analysis and water profiles in the different areas of the bio-inspired flow field. The results show that high relative humidity of the inlet gas flows, high pressure, low temperatures and low current density favor the accumulation of water in the flow field channels and GDL. Specifically, water accumulates preferentially in the anode side that make contact with the low part of the cathode foams inserted in the flow field, instead of blocking the closest area to the gases outlets points. This is due to permeation from the cathode foams to the anode side.

Numerical simulation of granular silicon growth and silicon fines formation process in polysilicon fluidized bed

Operating conditions strongly affect the yield and quality of polysilicon in a polysilicon fluidized bed. In this study, a new model of polysilicon fluidized bed was established using the Euler–Euler model coupled with population balance model (PBM), which was combined with fluid flow, heat, and mass transfer models, while considering the scavenging effect of silicon fines. The effects of different operating conditions on the deposition and formation rates of silicon fines were investigated. Results show that the model can correctly describe the particle growth process in the fluidized bed of polysilicon. The silicon fines and the interphase velocity difference show “N”- and “M”-shaped distributions along the axial direction, respectively. The particle temperature and concentration near the wall are higher than those in the central region. The decomposition of silane in the bottom region of the bed is dominated by heterogeneous deposition. The scavenging of silicon fines occurs in the dilute-phase region. The effects of operating conditions, i.e. inlet gas temperature, silane composition, and gas velocity, on the reactor performance were also explored comprehensively. Increasing the inlet gas composition and velocity enhances the formation rates of solid silicon and fines. Increasing the inlet gas temperature promotes the growth of solid silicon and inhibits the formation of silicon fines. High fluidization ratio, low inlet silane concentration, and high inlet gas temperature enhance the selectivity of silicon growth.

A thermodynamic analysis of the Linde-Hampson cycle using low-GWP R1234yf-blends

The Linde-Hampson cycle (LHC) exhibits a promising future as a cooling method to achieve cooling temperatures below −40 °C, and are highly desirable in commercial refrigeration. This paper investigated the refrigerant replacement options of low-GWP blends i.e. R1234yf/R1132a, R1234yf/R170, R1234yf/R41 and R1234yf/R744 in the LHC by using thermodynamic analysis. The compressor temperature, cooling capacity, coefficient of performance (COP) and exergy efficiency were chosen as the objective parameters. The modelling results show that the R1234yf/R41 mixture has larger cooling capacities, while the R1234yf/R1132a mixture has higher energy efficiency. Under a typical operating condition, the R1234yf/R1132a mixture attained a COP of 1.4162 and an exergy efficiency of 28.49%, demonstrating high priority for improving energy and exergy performances. Besides, the system performance will be improved significantly with increasing R1234yf mass fraction, but the cooling temperature will also increase. In addition, the condenser and expansion valve are the two components that deplete exergy the most, which should be the focus for performance improvement. These results have important guiding significance for understanding the effects of different operating conditions on the thermodynamic performance of the LHC, and also expand the selectivity towards the refrigeration system and its working fluids.

Experimental Comparative Investigations to Evaluate Cavitation Conditions within a Centrifugal Pump Based on Vibration and Acoustic Analyses Techniques

Cavitation is an essential problem that occurs in all kinds of pumps. This cavitation contributes highly towards the deterioration in the performance of the pump. In industrial applications, it is very vital to detect and decrease the effect of the cavitation in pumps. Using different techniques to analysis and diagnose cavitation leads to increase in the reliability of cavitation detection. The use of various techniques such as vibration and acoustic analyses can provide a more robust detection of cavitation within the pump. In this work therefore, focus is put on detecting and diagnosing the cavitation phenomenon within a centrifugal pump using vibration and acoustic techniques. The results obtained from vibration and acoustic signals in time and frequency domains were analysed in order to achieve better understanding regarding detection of cavitation within a pump. The effect of different operating conditions related to the cavitation was investigated in this work using different statistical features in time domain analysis (TDA). Moreover, Fast Fourier Transform (FFT) technique for frequency domain analysis (FDA) was also applied. Furthermore, the comparison and evaluation system among different techniques to find an adequate technique incorporating for accuracy and to increase the reliability of detection and diagnosing different levels of cavitation within a centrifugal pump were also investigated.

Performance Prediction of a Model Rotary Air Preheater Through Porous Media Approach

Abstract Rotary regenerative heat exchangers or rotary regenerators are used for various heat recovery applications in order to fulfill the energy requirements. Rotary air preheater is a rotary regenerative heat exchanger which is widely used in thermal power plants to recover heat energy from exhaust flue gases. Several numerical works are being carried out to improve the performance and reduce the cost of the rotary air preheater. However, the accurate modeling of the internal structure of the matrix demands a lot of CPU power and is a big challenge for researchers. To overcome this problem, the rotary matrix of the preheater can be modeled using a porous media approach. But a thorough investigation is required to evaluate its performance. In this work, rotary air preheater simulations were carried out by applying a porous media approach. The effects of different operating conditions, such as speed of rotor, the mass flowrate of incoming fluids, material of matrix, and inlet temperature of hot fluid on the performance of rotary air preheater were investigated. Simulation results were validated with the results obtained from the experimentation performed in-house. The effect of fluid flowrates on pressure drop was also studied. It has been observed that the rotational speed of the rotor significantly affects the performance of the preheater, while the inlet temperature of hot fluid has a negligible effect on performance.

New hybrid concentrated photovoltaic/membrane distillation unit for simultaneous freshwater and electricity production

Traditional photovoltaic-thermal desalination systems often rely on electricity to power pumps which can reduce the amount of electricity available for other practices. The current work presents an integrated system combining a concentrator photovoltaic (CPV) with a direct contact membrane distillation (DCMD) in a single unit. Hence, it is possible to use the thermal energy generated by the CPV unit to power the DCMD unit and produce both fresh water and electricity simultaneously. A comprehensive numerical model of the proposed system is developed and validated to investigate the effects of different operating conditions on the system's performance, such as the solar concentration ratio (CR), feed Reynolds number, and feed channel aspect ratio (AR), on the system's productivity. Furthermore, a modified design is introduced in which the length of the DCMD is enlarged beyond the CPV to benefit from the excess energy within the feed water. The predicted produced flux reached ∼33.2 kg/m2 h at CR = 300, Re = 175, and AR = 2400. The modified method produced a higher flux than the original design within the same CR values. The optimum length ratio values were calculated, which were found to be 1.7, while the counter configuration was nearly 1.5.

Aerobic treatment of fish canning wastewater using a pilot-scale external membrane bioreactor

Fish canning wastewater is characterized by high salinity and organic matter, which makes its treatment particularly difficult. To this purpose, the use of an aerobic membrane bioreactor (AeMBR) process could be a perfect option for the treatment of this wastewater. The aim of this study was to evaluate the effect of different operational conditions on the performance of the biological process and ceramic ultrafiltration (UF) membrane in AeMBR pilot plant for fish canning wastewater treatment. The AeMBR pilot was operated under ambient conditions (21.5 °C), 12 days of sludge retention time (SRT) and for a hydraulic retention time (HRT) of 24 h. The effect of operational parameters including organic loading rate (OLR) (3–5 kg COD/m3.day); total dissolved solids (TDS) (2.5–5 g/L), oxygenation rate (700 and 1300 NL/h) and transmembrane pressure (TMP) (0.05–1.5 bar) affected the quality of the effluent. The main performance results were the removal of approximately 97% of COD, 98% of BOD, 90% of nitrate and over 97% of total Kjeldahl nitrogen (TKN) and total phosphorus (TP). The treated effluent at the output of the AeMBR meets the quality standards according to the Food and Agriculture Organization (FAO) directive and the Moroccan standards for the discharge and reuse of water for irrigation and watering.

Production of Biodegradable Plastic from Biomass

Plastic pollution is one of the most dangerous environmental problems that threaten the world. Conventional plastic doesn’t degrade and tends to end up in seas and land, killing sea animals and polluting soils. Plastics obtained from agricultural wastes and have the ability to degrade, have appeared as possible solution to the conventional plastic problems. However, in order for the biodegradable plastic to substitute the conventional plastic, it must possess similar characteristics in addition to being economically and environmentally attractive. The aim of this paper is to produce durable and degradable plastic from potato peels. The effect of different operating conditions on the characteristics of the produced plastic, including biodegradation behavior, tensile strength and water absorption behavior, were studied. Acetic Acid with amounts of 4, 6 and 8 ml were used proving that the 8 ml acid concentration is the best from biodegradation point of view. Moreover, glycerol of amounts 2,4,6 ml were used, indicating a direct relation between degradation and glycerol amount, as well as, an inverse relation between water absorption and glycerol amount. Reaction temperature as well as drying temperatures were also tested showing that the low temperatures have good effect on enhancing the properties of the produced plastic.

Modeling and Experimental Validation for the Preparation of Concentrated Tea Extract Using a Forward Osmosis Process Using a Food-Grade Inorganic Draw Solute

In this study, a one-dimensional mathematical model was developed for the concentration of tea extract using a forward osmosis (FO) process. The membrane transport parameters were estimated by minimizing the error between the model output and the experimental results. The model equations were solved to predict the FO performance within allowable error limits. Further, a series of process flow sheet simulation studies were performed to investigate the effect of different operating conditions on the overall FO performance. Based on the simulation results, a multicriteria optimization was developed to attain the maximum permeate and minimum specific reverse solute flux (SRSF). Using the best-performing process flow sheet model, the feasibility of seawater and high-concentration reject brine as a draw solution was also investigated for the concentration of tea extract. The high-concentration reject brine (105.17 g L–1) can result in rapid dewatering with minimal SRSF (0.14 g L–1) along with simultaneous seawater dilution (81.38 g L–1).

Lithium in a Sustainable Circular Economy: A Comprehensive Review

Lithium is a vital raw material used for a wide range of applications, such as the fabrication of glass, ceramics, pharmaceuticals, and batteries for electric cars. The accelerating electrification transition and the global commitment to decarbonization have caused an increasing demand for lithium. The current supply derived from brines and hard rock ores is not enough to meet the global demand unless alternate resources and efficient techniques to recover this valuable metal are implemented. In the past few decades, several approaches have been studied to extract lithium from aqueous resources. Among those studied, chemical precipitation is considered the most efficient technology for the extraction of metals from wastewater. This paper outlines the current technology, its challenges, and its environmental impacts. Moreover, it reviews alternative approaches to recover lithium via chemical precipitation, and systematically studies the effects of different operating conditions on the lithium precipitation rate. In addition, the biggest challenges of the most recent studies are discussed, along with implications for future innovation.

Numerical Simulation on the Hydrogen Storage Performance of Magnesium Hydrogen Storage Reactors.

Magnesium hydride (MH) is one of the most promising hydrogen storage materials. Under the hydrogen storage process, it will emit a large amount of heat, which limits the efficiency of the hydrogen storage reaction. In this paper, the hydrogen storage performance of the magnesium hydrogen storage reactor (MHSR) and the effect of structural parameters were studied by numerical simulation. The effect of different operating conditions on the hydrogen storage performance of the MHSR is analyzed. The volume energy storage rate (VESR) was taken as the comprehensive evaluation index (CEI). The results show that fins and heat exchange tubes can improve the heat transfer performance of the MHSR. Increasing fin thickness can reduce hydrogen storage time, but increasing fin spacing is the opposite. With the increase of fin thickness and fin spacing, VESR increases first and then decreases. With the increase of inlet temperature, the hydrogen storage time decreases first and then increases. When the inlet velocity is more than 5 m/s, the hydrogen storage time basically stays at 900 s. By optimizing the operating conditions, the hydrogen storage time can be shortened by 57.8%.

An experimental study on recovering and concentrating ammonia by sweep gas membrane distillation

Ammonia is a toxic and hazardous substance, as well as a valuable chemical. The gaseous ammonia are soluble in water, rendering some industrial wastewater contains high concentration of ammonia. These wastewater can be a direct source for the production of commercially concentrated ammonia solution via sweep gas membrane distillation (SGMD). Taking advantage of vapor-liquid equilibrium of ammonia-water binary system, ammonia can be recovered from these wastewater, and concentrated to several times higher concentration under optimized conditions. In this work, we have demonstrated the ammonia recovery by SGMD process, and comprehensively investigated the effect of different operation conditions on the SGMD performance.

Comprehensive evaluation of municipal solid wastes and mixed feedstocks for commercial hydrothermal liquefaction in bio-refineries

Hydrothermal liquefaction (HTL) is a promising thermochemical conversion technology that converts waste biomass into valuable chemicals and energy. The process induces physical and chemical transformations of organic molecules under sub-critical or supercritical water. During HTL, the biomass molecules are hydrolyzed and degraded into low molecular weight, reactive species that may undergo recombination reactions to form condensed fragments. A substantial amount of oxygen from the biomass is removed via dehydration and decarboxylation during HTL. A number of existing studies in the literature have focused on hydrothermal conversion of feedstocks like wood, algae, plastics and the effect of different operating conditions on their hydrothermal conversion. However, literature on HTL of a heterogeneous feedstock like municipal solid wastes (MSW) is very limited. An understanding of the transformation of the different fractions present in MSW can be obtained from HTL of individual components. Available literature on HTL of bio-degradable wastes, non-bio-degradable polymers and MSW is reviewed in this paper. Consequently, catalytic upgradation to improve the yield and quality of the bio-crude, and continuous hydrothermal processing are also discussed. More importantly, a detailed discussion on the challenges involved in scaling up of the HTL process with MSW as the feedstock is presented using the available protocols for fuel readiness and data from commercial HTL plants. Due focus is given on the possibilities of deriving value-added products from the HTL of MSW on a large scale, while simultaneously tackling the waste management problem associated with MSW.

Ultrasound assisted preparation, characterization, and application of biosorbent for Rhodamine 6G removal from wastewater

AbstractNatural adsorbents offer promise for application in environmental protection mainly based on the cost efficiency and biodegradable nature. In the current work, a biosorbent has been synthesized from coconut shell (a common agrochemical waste) in the presence of ultrasound with an objective to improve the microstructure of the carbon coupled with activation using mixture of HNO3 with H2SO4 (7:3 proportion). SEM analysis clearly confirmed that ultrasound induced cavitational effects improved the porous structure of the sample. FTIR and XRD results confirmed the favorable adsorption characteristics for the synthesized activated carbon with no negative changes due to the use of ultrasound. The synthesized adsorbent was used for the removal of a toxic dye, Rhodamine 6G present in effluent at a level of 25 mg L−1. The detailed study into effect of operating parameters elucidated that optimum treatment time for maximum dye removal was 22 min whereas the optimal value of biosorbent loading and pH were 8 gL−1 and 10, respectively. The equilibrium data was fitted into different types of adsorption isotherm models, and Langmuir isotherm model was elucidated as the best fitted model with an adsorption capacity of 90.9 mg g−1. Similarly, the kinetic studies revealed that pseudo second order model fitted better than all the other models. Overall, the efficacy of prepared adsorbent in the presence of ultrasound was effectively demonstrated for the Rhodamine 6G removal from wastewater, also demonstrating the effect of different operating conditions during the adsorption.

Investigation on 3D fatigue crack propagation in pitch bearing raceway of offshore wind turbines

In complex marine environments, pitch bearings are more prone to crack initiation, propagation, and evolution, which leads to contact fatigue problems. Accurately identifying and predicting the evolution of early crack extensions in pitch bearings can effectively prevent major economic losses caused by failure. The two limitations of the current research on pitch bearing cracking are the low efficiency of the simulation and the fact that the contact fatigue models are mostly simplified to two-dimensional models. These models do not accurately reflect the influence of the raceway geometry parameters on the real situation. This study combined Bladed and MATLAB for an integrated life cycle simulation using Python and a cloud platform to reduce the simulation duration. A three-dimensional modelling method was proposed to calculate the crack propagation in pitch bearings throughout the full life cycle. The effects of different operating conditions, crack depths, and initial crack angles were investigated and analyzed. The results suggested that the maximum Hertz contact stress was 2961.4 MP. When the initial crack angle was greater than 0°, the crack generally propagated towards the core area. When the crack angle was less than 30°, the crack propagated gradually in depth and towards the surface. The fatigue life at an initial crack angle of 60° was 1.5 times that of an initial crack angle of 30°.

Droplet separation and sieving mechanism by grooved microchannel

A novel droplet sieving method utilizing grooved microchannel is proposed to achieve the monodispersity of droplets. The sieving performance and mechanism are investigated experimentally. Three different sieving flow regimes are observed in the experiment: incomplete sieving, complete sieving and main droplet rupture. The effects of different operating conditions on sieving efficiency are studied systematically. The results showed that when the total flow rate of the continuous phase in the main channel is lower, the small droplets would accumulate between the main droplets and could not be separated. Complete sieving could be achieved when the main body of the small droplet enters the sieving layer before arriving at the sieving channel. The larger continuous phase flow rate in sieving channel could create thicker sieving layer, which is conducive for small droplets to entering the sieving layer to achieve complete sieving. On the contrary, the higher continuous phase flow rate in the main channel would lead to thinner sieving layer, and the required flow rate in sieving channel would be higher to achieve complete sieving. Under the same sieving channel flow rate, the longer droplet is more apt to rupture. The sieving mechanism of droplets is proposed according to the force analysis in the channel. Whether the main droplet ruptures at the sieving junction depends on the combined action of the suction of the sieving channel, the interfacial tension, and the supporting force of the sieving groove.