Effects Of Different Operating Conditions Research Articles

Particle dynamics in a pseudo-2D spouted bed: Experiments and Euler–Lagrange simulations

This study is dedicated to a comprehensive examination of particle dynamics within a pseudo-2D spouted bed, employing a combination of experimental analysis and numerical simulations conducted with the Euler-Lagrange approach. To develop a robust CFD-DEM model for predicting particle dynamics in a pseudo-2D spouted bed, our proposed methodology includes the measurement of DEM parameters based on experimental data, a grid size independence test assessment, and an analysis of appropriate turbulent models and wall boundary conditions for the fluid phase. The effect of different operating conditions, e.g., particle mass and inlet air velocity, on the complex turbulent multiphase flow behavior is assessed. Additionally, we numerically investigated the frequency of collisions between particles and the temporal changes in collisional forces across various conditions. The experiments and numerical simulations provide valuable insights into the intricacies of particle dynamics within a pseudo-2D spouted bed, offering essential knowledge for the optimization of processes employing this equipment.

Simultaneous absorption of H2S, MM and COS into a novel SRSG absorbent using a rotating packed bed

In industries, many gases are required to remove hydrogen sulfide (H2S) and organic sulfur. However, it is still a huge challenge to achieve the efficient and simultaneous removal using a single process. Herein, a novel simultaneous removal sulfide gas (SRSG) absorbent is developed to simultaneously absorb H2S, methyl mercaptan (MM) and carbonyl sulfide (COS). The absorption mechanism between the SRSG absorbent and H2S, MM, COS is explored by quantum chemistry calculations (QCC) and controlled experiments in a rotating packed bed (RPB). Results indicate that the interaction between SRSG and H2S, MM belongs to physical absorption while COS absorption in SRSG obeys two molecule reaction mechanism. Furthermore, the effect of different operating conditions, including rotating speed (N), liquid flow rate (L), gas-liquid ratio (G/L) and temperature (T), on the absorption efficiencies (η) and gas volumetric mass transfer coefficient (KGa) of H2S, MM and COS is systematically investigated. It can be found that both η and KGa are dependent on those operating conditions. The optimal η value for H2S, MM and COS is up to 99.99%, 100%, 100%, respectively. Moreover, nondimensional equations for Sherwood number (Sh) are established, and the calculated and experimental values of Sh(H2S), Sh(MM) and Sh(COS) are in agreement with a deviation within ±13%, ±13%, and ±20%, respectively. These results will provide a valuable potential technique for simultaneously removing acidic gas components from industrial gases.

Hydrothermal liquefaction of Chlamydomonas nivalis and Nannochloropsis gaditana microalgae under different operating conditions over copper-exchanged zeolites

In this study, two different green microalgae, Chlamydomonas nivalis (C. nivalis) and Nannochloropsis gaditana (N. gaditana), were cultivated in open ponds and the harvested wet biomass was converted to bio-crude by hydrothermal liquefaction (HTL) with/without catalyst. Catalytic HTL experiments were performed by using copper-exchanged zeolites including Cu-MOR, Cu-ZSM-5, and Cu-SSZ13, synthesized by recently developed supercritical ion exchange method using scCO2. The composition of all bio-crudes was analyzed by elemental analysis and GC/MS. First, the effects of different operating conditions on the yields of the products and the bio-crude composition were determined for non-catalytic process. Temperature, duration, and water/algae biomass ratio in the feed were the process parameters investigated in the ranges of 250–350 ºC, 10–60 min, and 5–20 wt%, respectively. For C. nivalis, 300 ºC, 60 min, and water/algae ratio of 4 were the optimum conditions which led to maximum bio-crude yield of 18.8 wt%, while 300 ºC, 30 min, and water/algae ratio of 9 were the optimum ones for N. gaditana at which the maximum bio-crude yield of 34.0 wt% was observed. Bio-crude yield of N. gaditana was improved using Cu-MOR, while using catalysts for the case of C. nivalis resulted in more gasification with no positive effect on bio-crude yield. Moreover, elemental analysis showed that the fraction of nitrogen and oxygen in biocrude decreased in catalytic HTL runs, in line with the GC/MS results showing that the concentration of hydrocarbons and cyclic compounds increased in the presence of catalysts accompanied by a decrease in concentration of nitrogenous compounds.

Enhanced nitrogen removal through aerobic denitrifying bacteria in horizontal subsurface flow constructed wetlands: Influencing factors and microbial community structure

Variation in the demand for dissolved oxygen during nitrification and denitrification processes is one of the main constraints for nitrogen removal performance in conventional constructed wetlands. This study aimed to enhance the performance of horizontal submerged flow constructed wetland (HSCW) systems through aerobic denitrification (AD). The effects of different operating conditions on the performance and microbial community structure of the system were investigated using three experimental systems including a non-aerated HSCW without bacterial inoculation (CWC), a non-aerated HSCW with bacterial inoculation (CWM) and an intermittently aerated HSCW with bacterial inoculation (CWMA). Results showed that C/N ratio of 10 and aeration rate of 0.2 L/(min·L) were the optimum conditions for CWMA, which showed 29.01 % and 12.17 % higher COD and TN removals than CWC, even at an average temperature of 8.80℃. Microbial community analysis revealed that the addition of Pseudomonas stutzeri significantly increased the microbial diversity and abundance within the HSCWs. This study provides a new idea for the treatment of nitrogenous wastewater and the AD-CW system has a promising application in low-temperature areas.

Energy and exergy analysis of drying of potash particles in a pulsation-assisted fluidized bed

Potash particles exhibit cohesiveness and hygroscopic behavior in the presence of moisture. During the drying of wet potash particles, solid bridges form, and the agglomeration behavior of such particles reduces the efficiency of drying. In this work, pulsed airflow was employed to break agglomeration and eliminate channeling in a fluidized bed with wet potash particles. The effect of different operating conditions including inlet drying gas temperature (40 °C, 50 °C, and 60 °C) and pulsation frequency (1.0 Hz and 2.0 Hz) on the energy and exergy efficiency of fluidized bed drying of potash particles was investigated. A drying model based on the thin-layer theory was employed to correlate the experimental data of drying of potash particles. The results showed that the highest energy and exergy efficiency of potash drying, 28.6% and 27.8%, respectively, was achieved when the fluidized drying of potash particles was operated at lower temperatures and close to the natural frequency of the fluidized bed system.

Multi-Metal Oxide Catalyst for Electrochemical Oxidation of Organic Pollutants

In recent years, there has been a growing interest in developing highly efficient and stable catalysts for the electro-oxidation of water. These catalysts, besides water electrolysis, could be also a good alternative for removing organic pollutants from water by electro-degradation. Among the innovative groups of catalysts that have been investigated for this purpose, multi-metal oxides have been extensively studied for water electrolysis, but rarely for the direct or indirect oxidation of organic pollutants from water.1 Multi-metal oxide catalysts are composed of two or more metal cations that are chemically bonded to oxygen ions. The combination of different metal cations in a single oxide structure can lead to synergistic effects, which can enhance the catalytic activity and stability of the material. Several types of multi-metal oxide catalysts have been investigated for the electro-oxidation of water, including perovskite oxides, spinel oxides, layered double hydroxides, and mixed metal oxides. Perovskite oxides are a popular class of multi-metal oxide catalysts, which exhibit a wide range of interesting properties, including high catalytic activity, ionic and electronic conductivity, and thermal stability. These properties make perovskite oxides attractive materials for applications in various fields, such as environmental remediation.2 Additionally, the properties of perovskite oxides can be fine-tuned by doping or modifying their chemical composition, morphology, and crystal structure leading to the development of new materials with tailored properties.In this work, multi-metal oxide (perovskite) nanoparticles were synthesized by the hydrothermal method by adjusting the pressure and temperature to obtain multi-metal oxides with controlled crystallinity and morphology. The synthesis was successfully scaled up and electrodes were prepared by impregnating 3D supports with the active materials. The electrocatalytic activity of the prepared electrodes was analyzed by physical and electrochemical characterizations. Moreover, to evaluate the potential application of multi-metal oxide electrodes for organic pollutants removal, phenol was selected as the target pollutant. To complete the research, the effect of different operational conditions (current density, initial pH, initial phenol concentration, and flow rate) on the COD removal of the wastewater in the divided flow cell configuration was investigated. Furthermore, the removal pathway was studied using GC/MS. Acknowledgment: This project has received funding through the HYSOLCHEM project (grant agreement No. 101017928) from the European Union’s Horizon 2020 research and innovation programme.

Experimental studies on renewable hydrogen production by steam reforming of glycerol over zirconia promoted on Ni/Al2O3 catalyst

Abstract The impact of ZrO2 as a catalytic promoter for nickel-based alumina supported catalysts has been studied for the hydrogen synthesis via glycerol steam reforming. Hydrogen is a promising contender of clean fuel and has a key significance in the quest of an environment-preservation, low emission and more sustainable energy approach. Glycerol is a by-product produced during production of biodiesel by trans-esterification of vegetable oils. The higher hydrogen content in glycerol makes it the potential renewable feedstock for hydrogen production. Steam reforming process is the best method available which is highest in energy efficiency and most importantly most economical. The production of catalysts was based on the wet impregnation and co-precipitation methods. The majority of the bulk and surface properties of different synthesized catalysts were considered and determined by several characterization techniques like X-ray diffraction technique, BET surface area and scanning electron microscopy. The performance of catalyst is based on glycerol conversion and hydrogen yield obtained from the steam reforming process taking place in the fixed bed catalytic reactor. The effect of different operating conditions like contact time, temperature, metal loading, and steam to glycerol ratio were investigated to produce maximum hydrogen and glycerol conversion. The results show that the incorporation of promoter 2 % ZrO2 improved the activity of Ni/Al2O3 catalysts significantly resulting 96 % glycerol conversion, 84 % hydrogen production and greater stability at contact time = 15 kg cat s/mol, temperature = 800 °C, steam to glycerol ratio = 9:1 mol/mol, and pressure = 1 atm.

Electrochemical activation of peroxydisulfate by Ti/IrTaO2 anode for quick degradation of xanthate

High concentrations of residual xanthate in mineral processing wastewater often limit the reuse of tailing water. Targeted removal of xanthate is an effective strategy for improving the tailing water recycling rate. In this study, the degradation efficiency and mechanism of sodium ethyl xanthate (SEX) in an electroactivated peroxydisulfate (EAPDS) system were investigated systematically. To avoid the influence of co-existing organic and inorganic matters in real flotation wastewater, we used simulated SEX wastewater to conduct the efficiency and mechanism investigation. A significant synergistic effect between electrocatalysis and peroxydisulfate was observed during the SEX decomposition. When the initial concentration of SEX was 200 mg/L, it achieved 100% removal rate only in 30 min with PDS dosage of 5 mM at current density of 10 mA/cm2. The introduction of peroxydisulfate boosted the removal efficiency six-fold compared to electrocatalysis alone. UV-Vis spectroscopy and GC-MS analyses revealed that the intermediate products of SEX were C2H5OH and CS2. The reactive oxygen species induced in the EAPDS were identified using a series of detection methods. •OH, 1O2, h+, O2•− and electron transportation process (ETP) all contributed to SEX removal. The degradation mechanism in the EAPDS system was proposed based on the analysis of the reactive oxygen species and products. Application to real flotation wastewater was attempted as well. The effects of different operating conditions were also evaluated, including pH, coexisting anions, PDS dosage, and current density. This study provides a new approach for the rapid removal of residual xanthates from mineral processing wastewater.

Treatment of food processing industries wastewater using a novel Fuller's earth clay-based tubular ceramic membrane.

This study investigates the feasibility of a robust, low-cost tubular microfiltration ceramic membrane fabricated using a mixture of locally available Fuller's earth clay (FEC) and solid waste material, rice husk ash (RHA), to treat effluents generated by a local dairy and palm oil industries. Fabrication of the membrane was carried out by employing the extrusion method followed by sintering at a temperature of 850 °C. Raw materials were characterized using XRD, XRF, FTIR, TGA, and differential thermal analysis (DTA). The membrane that underwent sintering exhibits a 61% porosity level, 43.29 L/m2 h bar water permeability, 0.115 μm average pore size, and relatively good corrosion resistance. Further, the effect of different operating conditions, including pressure (1.03-2.41 bar) and cross-flow rate (30-150 Lph), on the microfiltration of both the wastewaters is studied. The membrane lowered the COD levels below the discharge limit (<200 mg/L) of the Central Pollution Control of India for both wastewaters. Finally, Hermia's fouling models were used to identify the fouling mechanism concerned.

Modeling of contact thermal resistance in lateral capillary tube-suction line heat exchangers with experimental validation and investigation

This paper studied the lateral capillary tube-suction line heat exchanger (CTSLHX) with different contact types and different geometries. An improved one-dimensional model of the CTSLHX was established, using the CFD model to derive the contact thermal resistance between the capillary tube and the suction tube. An experimental bench was built to test the steady-state heat transfer and flow performance. It was found that the model predicted 87.6 % and 98.9 % of the measured mass flow rate within the error band of ± 10 % and ± 15 %. The prediction error of the CTSLHX heat transfer effectiveness was within ± 10 %. Parametric effects of different operating conditions and structural parameters on the performance of CTSLHX were investigated. Furthermore, experiments were carried out to study the temperature distribution along the transition section between the exit of the capillary tube and the evaporator. The unique temperature increase reveals that it is beneficial for reducing noise by wrapping a layer of rubber around the second increaser fitting.

Effect of different operation conditions on PCDD/F inhibition by ammonium dihydrogen phosphate: concentrations, distributions and mechanisms

Effect of different operation conditions on PCDD/F inhibition by ammonium dihydrogen phosphate: concentrations, distributions and mechanisms

Application of polyoxometalates and their composites for the degradation of antibiotics in water medium

This paper summarizes the potential of polyoxometalate (POM)-based catalysts in view of pharmaceutical wastewater treatment and recent advances that took place in this field. POMs are anionic clusters of transition metals, which exhibit unique characteristics such as high catalytic activity and multi-electron redox properties. Recently, they have been explored by some research groups for degrading antibiotics and pharmaceutical compounds (PCs) from contaminated water matrix. Several modifications of POM, along with their composite formation with new-age materials like g-C3N4 and reduced graphene oxide (RGO), have led to the formation of novel photocatalysts, which have also been reported as active materials to destroy the PCs. These promising catalysts have revealed the efficiency of complete destruction of these recalcitrant compounds within a short reaction time and showed good reusability characteristics. Among the widely used PCs, the notable ones include tetracycline (TC), sulfamethoxazole (SMX), ciprofloxacin (CIP), etc. Most of the articles cited here centered on TC degradation followed by other drugs. The effects of different operating conditions, degradation efficiency, and mechanism and stability aspects of various POM-based catalysts are discussed. The current knowledge gap in this area with bright future perspectives is also highlighted. The description will provide valuable insight to the research community regarding the capability of POM-based catalysts to eliminate antibiotics, as well as designing highly efficient catalysts for a sustainable future.

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.