Effects Of Operating Parameters Research Articles

Effect of Operating Parameters on Photocatalytic Treatment of Synthetic Wastewater Using CaTiO3

Photocatalysis is thought to be a long-term, environmentally friendly, economically feasible, and promising technique for treating wastewater. The development of semiconductor nanoparticles has generated a great deal of interest in the treatment of wastewater. To break down complex contaminants found in wastewater into simpler compounds, including H2O and CO2, several UV/visible light excitable nanomaterials have been explored as photocatalysts. Their effectiveness can be managed by adjusting several reaction-related parameters like the intensity of light, irradiance time, pH, catalyst dose, temperature, doping, etc. The performance of the photocatalyst in the photodegradation of contaminants is greatly affected by these parameters. The main goal of this study is to find the best operational parameters and their impact on the photocatalytic treatment of synthetic waste-water using calcium titanate (CaTiO3) nanoparticles. For this purpose, sol-gel synthesized CaTiO3 with a band gap of 3.57 eV was used. The size of the synthesized nanoparticles is smaller than 47.62 nm. The results of photocatalytic treatment of synthetic wastewater demonstrate that CaTiO3 exhibits its best photocatalytic performance at 33 W UV light, pH 6.0, and 3.33 g L-1 CaTiO3 dose with 8 hours of irradiation time. With chemical oxygen demand (COD) concentrations varying from 700 to 40000 mg L-1 at the initial stages, the percentage of COD removal under these conditions was 100% to 77%.

Improved bacterial elimination in wastewater through electrocoagulation: hydrogen generation, adsorption of colloidal bacteria-flocks, and electric field bactericidal action

ABSTRACT Electrocoagulation (EC) has emerged as a promising method for wastewater treatment, offering efficient removal of various contaminants, including bacteria. This study investigates the mechanisms underlying bacterial removal in EC processes, mainly the hydrogen-mediated foam, the effect of operational parameters, including initial pH, current density, and reaction time, and evaluates the associated energy consumption. The EC reactor employed aluminum electrodes and operated at a current intensity of 3.0 A. It demonstrated a notable bacterial removal efficiency, with 120.102 UFC ml−1 of mesophyll floral aerobic bacteria removed through colloid bacteria-flocs precipitation, 440.102 UFC ml−1 via bacterial-bulls flotation from foam, and 117.102 UFC ml−1 through attraction at the electrodes’ plate surface. We found that the EC process leads to the formation of aluminum hydroxide and ferrous hydroxide precipitates, which adsorb bacteria and facilitate their removal from the wastewater via electrostatic forces with an energy consumption of 45 kWh/m3. Overall, this research provides valuable insights into the mechanisms governing bacterial removal in EC and highlights the importance of energy consumption analysis for optimizing wastewater treatment processes.

High efficiency of treated-phengite clay by sodium hydroxide for the Congo red dye adsorption: optimization, cost estimation, and mechanism study.

Wastewater textile dye treatment is a challenge that requires the development of eco-friendly technology to avoid the alarming problems associated with water scarcity and health-environment. This study investigated the potential of phengite clay as naturally low-cost abundant clay from Tamgroute, Morocco (TMG) that was activated with a 0.1M NaOH base (TMGB) after calcination at 850°C for 3 hours (TMGC) before its application in the Congo red (CR) anionic dye from the aqueous solution. The effect of various key operational parameters: adsorbent dose, contact time, dye concentration, pH, temperature, and the effect of salts, was studied by a series of adsorption experiments in a batch system, which affected the adsorption performance of TMG, TMGC, and TMGB for CR dye removal. In addition, the properties of adsorption kinetics, isotherms, and thermodynamics were also studied. Experimental results showed that optimal adsorption occurred at an acidic pH. At a CR concentration of 100 mg L-1, equilibrium elimination rates were 68%, 38%, and 92% for TMG, TMGC, and TMGB, respectively. The adsorption process is rapid, follows pseudo-second-order kinetics, and is best described by a Temkin and Langmuir isotherm. The thermodynamic parameters indicated that the adsorption of CR onto TMGB is endothermic and spontaneous. The experimental values of CR adsorption on TMGB are consistent with the predictions of the response surface methodology. These led to a maximum removal rate of 99.97% under the following conditions: pH =2, TMGB dose of 7g L-1, and CR concentration of 50 mg L-1. The adsorbent TMGB's relatively low preparation cost of around $2.629 g-1 and its ability to regenerate in more than 6 thermal calcination cycles with a CR removal rate of around 56.98%, stimulate its use for textile effluent treatment on a pilot industrial scale.

Insight into electricity production performance from dried waste activated sludge in dual chamber microbial fuel cells: Influencing factors, neural network modelling and microbial community analysis

Directly deriving electrical energy from waste activated sludge (WAS) by using microbial fuel cell (MFC) is one of the most promising alternatives to resource utilization of WAS. However, obtaining high MFC performance is still a great challenge for the full-scale implementation of MFC. Therefore, this study aimed to quantify and model the effect of different operating parameters on the performance of MFC fed with dried WAS as anode substrate. The results indicated that MFC exhibited a fast start-up time of 3 days at the inoculated anaerobic sludge: dry WAS mass ratio of 1:5. Moreover, the output voltage and power density of MFC were highly dependent of anolyte pH and temperature, WAS concentration, which was well simulated and predicted by the BPANN model. It was revealed that MFC fed with dry WAS exhibited good performance at 55ºC, pH 9.0 and WAS concentration of 16 g/L, while the stable output voltage and power density were 0.705 V and 5.248 W/m3, respectively. The anolyte temperature significantly affected microbial communities of the anode biofilm. At the phylum level, Synergistota and Proteobacteria dominated the anode biofilm at 35ºC, while Firmicutes was absolutely enriched in the anode biofilm at 55ºC. At the genus level, the predominant Advenella is detected in the anode biofilm at 35ºC, whereas the preponderant MBA03 is identified in the anode biofilm at 35ºC. The findings herein may provide a route for efficiently driving power energy from WAS, which can facilitate the fulfillment of full-scale MFC for the resource utilization of WAS.

Proposal and performance analysis of a novel hydrogen and power cogeneration system with CO2 capture based on coal supercritical water gasification

To establish a sustainable energy system, it is essential to achieve low-carbon and clean utilization of coal. In this study, a novel hydrogen and power cogeneration system with full CO2 capture that based on coal supercritical water gasification (SCWG) is proposed. Hydrogen is separated from syngas produced by coal SCWG, and the remaining combustible gas is burned to generate power. Moreover, supercritical CO2 cycle is integrated within the cogeneration system to recover the waste heat with high exergy efficiency. Thermodynamic performances, effects of key operation parameters and off-design performances under part-load conditions of the cogeneration system are analyzed. Under the design condition, the cogeneration system produces 20.26 mol kg−1 hydrogen and generates 8746 kJ kg−1 net power, achieving the high energy efficiency and exergy efficiency of 54.77% and 52.54%. The exergy efficiency of cogeneration system can be enhanced by optimizing the operation parameters, which is increased by 0.42%, 4.03% and 1.10% with the optimal coal water slurry concentration (17.5%), higher gasification temperature (750°C) and higher gas turbine inlet parameters (1500°C/3 MPa), respectively. The cogeneration system performance decreases with the power load, and the exergy efficiency decreases by 9.61% when the system power load reduces from 100% to 30%.

Gas-phase and liquid-phase purification of plastic waste derived carbon nanotubes: Effect of purification agent and operational parameters

The preparation of carbon nanotubes (CNTs) by catalytic pyrolysis of waste plastics is one of the most promising technologies to realize the harmless and high-value recycling of waste plastics. However, there are limited studies on the purification of waste-derived carbons, which is of significance for downstream applications. In this paper, the effects of different gas-phase purification conditions (temperature, gas type), liquid-phase purification (hydrochloric and nitric acid reflux), and combined gas-liquid purification on the properties of CNTs prepared from waste plastics were investigated. The as-obtained and purified CNTs were characterized using SEM, TEM, TPO, XRD, XPS, Raman spectroscopy, and FTIR spectroscopy. Results showed that operational temperatures have distinct impacts on the properties of CNTs during gas-phase purification. An appropriate temperature range for gas-phase purification was determined, with temperatures around 450 °C for air, 650 °C for CO2, and 700 °C for steam respectively, so that the amorphous carbon could be removed and the graphitization of CNTs was retained. Approximately 93 wt% of the metal catalyst particles could be removed with acid treatment for 4 h. In addition, carboxyl and hydroxyl functional groups were introduced to CNTs after acidic treatment. Furthermore, it was found that the approach combining CO2 treatment and nitric acid washing yielded CNTs with relatively higher quantities and lower defect levels. Results showed the properties of CNTs varied from the purification methods, which could meet different needs based on the downstream specific application requirements.

One-step facile synthesis of the photocatalyst using pyrolyzed terephthalic acid and m-phenylenediamine composite for Cr(VI) reduction in aqueous solutions

Discharging heavy metals into water bodies presents a serious environmental risk. Hexavalent chromium (Cr(VI)) is one of the harmful substances that pose substantial health hazards to humans. The aim of this research is to synthesize an organic composite photocatalyst by polymerizing m-phenylenediamine (mPD) and Terephthalic acid (TA) at high temperatures. TA and mPD interact and result in the formation of a polymerized-mPD-TA photocatalyst to reduce Cr(VI) under visible light. Field Emission Scanning Electron Microscopic (FESEM), Energy-Dispersive X-ray (EDX), Dynamic Light Scattering (DLS), Fourier-transform Infrared spectroscopic (FT-IR), Brunauer-Emmett-Teller (BET), UV–Vis Diffuse Reflectance Spectra (UV-vis-DRS), Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky methods were used to characterize the produced photocatalyst. The effect of operational parameters including pH, volume of hole scavenger, photocatalyst mass, and Cr(VI) initial concentration was investigated, and the optimum conditions were clarified. To investigate the adsorptive characteristics of the prepared photocatalyst, Isotherm, and Kinetic investigations were carried out. The adsorption studies revealed that the Freundlich and pseudo-second-order (PSO) models offered a better suitable match to the experimental data. In order to investigate the practicality of the photocatalyst, reusability, and sunlight tests were carried out, and it was shown that the prepared composite possessed great durability and could perform under sunlight to reduce Cr(VI).

System simulation and parametric analysis of low-concentration coal mine gas fed SOFC-CHP with deoxygenation and enrichment pretreatment

Solid oxide fuel cell (SOFC) combined heat and power (CHP) can efficiently convert low-concentration coal mine gas (LC-CMG) into clean energy, avoiding the greenhouse effect of LC-CMG. Deoxygenation and methane enrichment pretreatment of LC-CMG can prevent explosion and anode oxidation risk. Herein, a chemical process model of LC-CMG fed SOFC-CHP system with the pretreatment was established to predict the performances under different operating conditions. Performance evaluation and exergy analysis were performed considering the use of oxygen-rich gas from the pretreatment at SOFC cathode. The effects of key operation parameters on system performances were investigated in terms of residual oxygen concentration, inlet methane concentration, fuel flow and fuel utilization. The results indicated that net electrical efficiency and heat supply efficiency can respectively reach 49.13 % and 23.90 % using LC-CMG of 15 % CH4 with enhancing effect of oxygen-rich gas at cathode. The decrease of methane concentration and the increase of residual oxygen concentration and flow rate caused the decreased electrical efficiency but the increased heat supply efficiency due to the enlargement of concentration polarization and heat supply. The optimal operation parameters were recognized by comprehensively considering diverse performance indicators. This work can guide system integration and operation optimization of LC-CMG fed SOFC-CHP.

Numerical Research on Leakage Characteristics of Pure Hydrogen/Hydrogen-Blended Natural Gas in Medium- and Low-Pressure Buried Pipelines

To investigate the leakage characteristics of pure hydrogen and hydrogen-blended natural gas in medium- and low-pressure buried pipelines, this study establishes a three-dimensional leakage model based on Computational Fluid Dynamics (CFD). The leakage characteristics in terms of pressure, velocity, and concentration distribution are obtained, and the effects of operational parameters, ground hardening degree, and leakage parameters on hydrogen diffusion characteristics are analyzed. The results show that the first dangerous time (FDT) for hydrogen leakage is substantially shorter than for natural gas, emphasizing the need for timely leak detection and response. Increasing the hydrogen blending ratio accelerates the diffusion process and decreases the FDT, posing greater risks for pipeline safety. The influence of soil hardening on gas diffusion is also examined, revealing that harder soils can restrict gas dispersion, thereby increasing localized concentrations. Additionally, the relationship between gas leakage time and distance is determined, aiding in the optimal placement of gas sensors and prediction of leakage timing. To ensure the safe operation of hydrogen-blended natural gas pipelines, practical recommendations include optimizing pipeline operating conditions, improving leak detection systems, increasing pipeline burial depth, and selecting materials with higher resistance to hydrogen embrittlement. These measures can mitigate risks associated with hydrogen leakage and enhance the overall safety of the pipeline infrastructure.

Numerical model for electrogenic transport by the ATP-dependent potassium pump KdpFABC

In vitro assays of ion transport are an essential tool for understanding molecular mechanisms associated with ATP-dependent pumps. Because ion transport is generally electrogenic, principles of electrophysiology are applicable, but conventional tools like patch-clamp are ineffective due to relatively low turnover rates of the pumps. Instead, assays have been developed to measure either voltage or current generated by transport activity of a population of molecules either in cell-derived membrane fragments or after reconstituting purified protein into proteoliposomes. In order to understand the nuances of these assays and to characterize effects of various operational parameters, we have developed a numerical model to simulate data produced by two relevant assays: fluorescence from voltage-sensitive dyes and current recorded by capacitive coupling on solid supported membranes. Parameters of the model, which has been implemented in Python, are described along with underlying principles of the computational algorithm. Experimental data from KdpFABC, a K+ pump associated with P-type ATPases, are presented, and model parameters have been adjusted to mimic these data. In addition, effects of key parameters such as nonselective leak conductance and turnover rate are demonstrated. Finally, simulated data are used to illustrate the effects of capacitive coupling on measured current and to compare alternative methods for quantification of raw data.

Unlocking the unique catalysts of CoTiO3/BiVO4@MIL-Fe(53) for improving Cr(VI) reduction and tetracycline degradation

Environmental contamination by hexavalent chromium (Cr(VI)) and antibiotic drug residues pose significant challenges to public health and ecosystems. This study investigates the application of CoTiO3/BiVO4@MIL-Fe(53) (CT/BV@Fe-MOF) for the reduction of Cr(VI) and degradation of tetracycline (TCL) under visible light. After grafting an iron-based metal–organic framework MIL-Fe(53) on a modified CoTiO3/BiVO4 composite, the photogenerated electrons could easily be transferred from CoTiO3 to BiVO4/Fe-MOF species via interfacial charge transfer. UV–vis diffuse reflectance spectroscopy showed that charge carriers were formed in response to visible light absorption. The effect of different operating parameters, including catalyst load, pH, initial Cr(VI), and TCL concentration, was systematically evaluated during the photocatalytic process. The CT/BV@Fe-MOF composite exhibited 98.7% reduction efficiency in Cr(VI) (50 ppm) and 97.5% degradation efficiency towards TCL (30 ppm) within 90 min, resulting in a greater efficiency than the pristine CoTiO3, BiVO4, and Fe-MOF materials. The CT/BV@Fe-MOF composite displayed excellent stability over six cycles, highlighting its potential for practical applications. In addition, the plausible degradation pathway of TCL was evaluated using LC-ESI/MS analysis, while the TEST program was utilized to investigate the toxicity of the products generated during the degradation process.

Analyzing the methanation thermodynamic feasibility of steel plant byproduct gases

To improve the utilization of byproduct gases in the steel plant, the coke oven gas (COG) methanation combined with blast furnace gas (BFG) and basic oxygen furnace gas (BOFG) was proposed in viewpoint of economy and environment. The optimization mathematics model based on Gibbs free energy minimization was established to predict the thermodynamic feasibility of the proposed methanation. To solve the proposed model, the convenient method was implemented by using the Gibbs module in Aspen Plus software. Effects of operation parameters on the methanation performance were revealed to identify the optimized conditions. To reduce the solid carbon concentration, it was found that the optimized conditions of temperature, pressure and stoichiometric number were 650 °C, 30 bar and 3.0, respectively. Moreover, it was discovered that 10 mol% of BFG or BOFG could be mixed into COG to obtain the maximum methane yield. In addition, it was testified that there were the good agreements between calculated results and industrial and published data, which indicated that the proposed methanation was thermodynamically feasible. Therefore, the simple and easy method was developed to evaluate the methanation operating conditions from the aspect of thermodynamic equilibrium, which provided the basic process conditions of byproduct gases methanation to enhance the steel plant efficiency and reduce carbon emissions.

Granulated graphene oxide-activated carbon for adsorptive removal of diclofenac sodium and ibuprofen in a continuous fixed-bed column

The granular graphene oxide-activated carbon (GGA) composite was synthesized with polyvinyl alcohol (PVA) and malonic acid (MA) as chemical crosslinker at different conditions. GGA synthesis was performed at different parameters including binder-to-powder ratio in the range of 0.5–1.2, synthesis time in the range of 2–24 h, and drying temperature in the range of 60–110 °C. Response surface methodology (RSM) was used to optimize the synthesis parameters of the adsorbent synthesis. The optimum parameters for synthesis were achieved at a binder-to-powder ratio of 0.875, a synthesis time of 23.992 h, and a drying temperature of 60.071 °C. XRD, FTIR, FE-SEM, BET and TGA analyses were used to discuss the characteristics of the adsorbent structures. The surface area and mechanical stability were found to be 156.59 m2/g and 95.417 %, respectively. The adsorption behavior of mono-components (diclofenac sodium (DCF)/ibuprofen (IBP)) and bi-components (DCF + IBP) on the GGA was evaluated in a fixed-bed column. The effects of column operating parameters, including bed mass (m: 0.25–0.75 g), flow rate (Q: 5–9 mL/min), and adsorbate concentration for DCF (C: 20–100 mg/L) and IBP (C: 5–15 mg/L) on the breakthrough curves were investigated. The experimental data of fixed-bed column were correlated with breakthrough models such as Thomas, Bohart-Adams, Yoon-Nelson, Yan, Gompertz, and Log-Gompertz via both linear (under different column operating conditions) and nonlinear (for DCF (Co of 60 mg/L; m of 0.5 g and Q of 7 mL/min) and IBP (Co of 10 mg/L; m of 0.5 g and Q of 7 mL/min)) regression analysis. The maximum adsorption capacities calculated by the Thomas model were 110.068 and 34.912 mg/g for DCF and IBP, respectively. In bi-component systems, antagonistic behavior was observed in the adsorption of DCF and IBP. The results showed that the GGA can successfully remove DCF and IBP through a fixed-bed adsorption column.

Community structure and function during periods of high performance and system upset in a full-scale mixed microalgal wastewater resource recovery facility

Microalgae have the potential to exceed current nutrient recovery limits from wastewater, enabling water resource recovery facilities (WRRFs) to achieve increasingly stringent effluent permits. The use of photobioreactors (PBRs) and the separation of hydraulic retention and solids residence time (HRT/SRT) further enables increased biomass in a reduced physical footprint while allowing operational parameters (e.g., SRT) to select for desired functional communities. However, as algal technology transitions to full-scale, there is a need to understand the effect of operational and environmental parameters on complex microbial dynamics among mixotrophic microalgae, bacterial groups, and pests (i.e., grazers and pathogens) and to implement robust process controls for stable long-term performance. Here, we examine a full-scale, intensive WRRF utilizing mixed microalgae for tertiary treatment in the US (EcoRecover, Clearas Water Recovery Inc.) during a nine-month monitoring campaign. We investigated the temporal variations in microbial community structure (18S and 16S rRNA genes), which revealed that stable system performance of the EcoRecover system was marked by a low-diversity microalgal community (DINVSIMPSON = 2.01) dominated by Scenedesmus sp. (MRA = 55 %-80 %) that achieved strict nutrient removal (effluent TP < 0.04 mg·L-1) and steady biomass concentration (TSSmonthly avg. = 400–700 mg·L−1). Operational variables including pH, alkalinity, and influent ammonium (NH4+), correlated positively (p < 0.05, method = Spearman) with algal community during stable performance. Further, the use of these parameters as operational controls along with N/P loading and SRT allowed for system recovery following upset events. Importantly, the presence or absence of bacterial nitrification did not directly impact algal system performance and overall nutrient recovery, but partial nitrification (potentially resulting from NO2− accumulation) inhibited algal growth and should be considered during long-term operation. The microalgal communities were also adversely affected by zooplankton grazers (ciliates, rotifers) and fungal parasites (Aphelidium), particularly during periods of upset when algal cultures were experiencing culture turnover or stress conditions (e.g., nitrogen limitation, elevated temperature). Overall, the active management of system operation in order to maintain healthy algal cultures and high biomass productivity can result in significant periods (>4 months) of stable system performance that achieve robust nutrient recovery, even in winter months in northern latitudes (WI, USA).

A facile strategy for designing hollow-porous polymer microparticles with tunable structures

Biodegradable hollow-porous microparticles have shown great potentials in chemical and biomedical areas owing to their distinctive structural attributes. Herein, a simple but instructive strategy was proposed to construct hollow-porous polylactic acid (PLA) microparticles in one-step based on electrohydrodynamic atomization technology. Hollow-porous microparticles with fusiform, red blood cell and spherical shapes were successfully fabricated with production rates of 70 mg/h, 30 mg/h and 105 mg/h. A formation map in terms of flow rate ratio and PLA concentration was obtained to demonstrate the operating regions. Effects of key operating parameters were studied, showing that high voltage (11.4 kV−12.4 kV) and low PLA concentration conditions (2.5 %−3.5 %) are preferred to get well-structured particles. The evolutions of Taylor cone and atomization state were also explored experimentally and numerically to further understand the process. The prepared microparticles exhibit excellent sustained release performance and high encapsulation rate (>90 %). This strategy offers a satisfactory one-step method for preparing various structured hollow-porous polymer particles as drug carriers.

Mechanical and surface properties of semifinished potato tuber exposed to UV-C radiation at varied operational parameters

AbstractThe current study aimed at investigating the effect of certain operational parameters of UV-C radiator on the selected mechanical properties of semifinished potato tuber. Innovator potato variety was selected for the preparation of semifinished potato strips. The prepared potato strips were stored for 24 h following exposure at the desired storage condition. The irradiation experiment was carried out using a UV-C chamber at varied UV-C doses, Mode of exposure, and distance from the radiator. UV-C dose has a pronounced effect over the other tested parameters. Samples subjected at 60 mJ/cm2 resulted in higher resistance to compression and bending force while the resistance to cutting force was enhanced at a lower UV-C dose (15 mJ/cm2). Mechanical properties were not significantly impacted by the mode of exposure and distance from the light. Furthermore, the Morphological and microstructural properties of the sample were examined using SEM and AFM resulting in alteration in granule size, spacing, and roughness of the irradiated samples.

Dielectrophoretic separation/classification/focusing of microparticles using electrified lab-on-a-disc platforms

BackgroundSeparation, classification, and focusing of microparticles are essential issues in microfluidic devices that can be implemented in two categories: using labeling and label-free methods. Label-free methods differentiate microparticles based on their inherent properties, including size, density, shape, electrical conductivity/permittivity, and magnetic susceptibility. Dielectrophoresis is an advantageous label-free technique for this objective. Besides, centrifugal microfluidic devices exploit centrifugal forces to move liquid and particles. The simultaneous combination of dielectrophoretic and centrifugal forces exerted on microparticles still needs to be scrutinized more to predict their trajectories in such devices. ResultsAn integrated system utilizing two categories in microfluidics is proposed: dielectrophoretic manipulation of microparticles and centrifugal-driven microfluidics, followed by a numerical analysis. In this regard, we assumed a rectangular microchannel with internal unilateral planar electrodes equipped with three equal-sized outlets placed radially on a centrifugal platform where microparticles flow toward the disc's outer edge. The effect of different coordinate-based parameters, including radial and lateral distances (X and Y offsets)/tilting angles toward the radius direction (α), on the particles' movement was investigated. Additionally, the effect of operational parameters, including applied voltage, the microchannel width, the number of enabled electrodes, the diameter of particles, and the configuration of electrodes, were analyzed, and the distributions of particles toward the outlets were monitored. It was found that enhanced particle focusing becomes possible at lower rotation speeds and higher electric field values. Furthermore, the proposed centrifugal-DEP system's efficiency for classifying red blood cells/platelets and Live/Dead yeast cells systems was evaluated. SignificanceOur integrated system is introduced as a novel method for focusing and classifying various microparticles with no need for sheath flows, having the ability to conduct particles at desired routes and focusing width. Furthermore, the system effectively separates various bioparticles and offers ease of operation and high-efficiency throughput over conventional dielectrophoretic devices.

A Cold Flow Model of Interconnected Slurry Bubble Columns for Sorption-Enhanced Fischer–Tropsch Synthesis

For technical application with continuous operation of sorption-enhanced (SE) reactions, e.g., Fischer–Tropsch, a special reactor concept is required. SE processes are promising due to the negative effects of water on conversion and catalyst. The reactor concept of two interconnected slurry bubble columns combines the reaction with in situ water removal in the first, and sorbent regeneration in the second column with continuous exchange of slurry between the two. The liquid circulation rate (LCR) between the columns is studied in a cold flow model, measured by an ultrasonic sensor. The effects of different operating and geometric parameters, e.g., superficial gas velocity, liquid level and tube diameter on gas holdup and LCR are discussed and modelled via artificial intelligence methods, i.e., extremely randomized trees and neural networks. It was found that the LCR strongly depends on the gas holdup. The maximum of 4.28 L min−1 was reached with the highest exit, widest tube and highest superficial gas velocity of 0.15 m s−1. The influence of liquid level above the exit was marginal but water quality has to be considered. Both models offer predictions of the LCR with errors &lt; 6%. With an extension of the models, particle circulation can be studied in the future.

Membrane role in heat and mass transfer resistance distribution and performance of hollow fiber membrane contactor for SGMD desalination

Hollow fiber membrane contactor (HFMC) is the core device of heat mass exchange between seawater solution and sweeping air in sweeping gas membrane distillation (SGMD) desalination. In order to reveal the distribution of heat and mass transfer resistance on feed solution side, porous membrane side and sweeping air side, a mathematical model considering the simultaneous heat mass transfer and water vapor diffusion mechanism in the membrane pores was established for the cross-flow HFMC. The simulation results of the model were compared with experimental results and literature results. Comparison shows that the deviation of simulation results of the model is less than 13.4 %, which verifies the accuracy and reliability of the simulation results. Influences of the main structural characteristics of porous membrane on the resistance distribution of heat and mass transfer, efficiency and membrane flux were explored. Air side dominates the heat transfer process, while the membrane side accounts for less than 39 % of the total heat transfer resistance for the main range of membrane microstructure parameters investigated. The mass transfer is controlled by the porous membrane except for thin membrane with a thickness of less than 100 μm. Membranes with porosity above 0.8 and as thin as possible can achieve better mass transfer efficiency and freshwater flux. Increasing mean pore diameter has a strong promotion effect on the increase of membrane flux before it reaches 150 nm, and beyond this critical value, the water vapor diffusion mechanism changes from Knudsen collision to molecular collision. Effects of different operating parameters and membrane microstructure parameters on air temperature distribution and humidity distribution were also analyzed.

Local entropy generation optimization and thermodynamic irreversibility analysis of oval-shaped coaxial ground heat exchangers: A detailed numerical investigation

Optimizing the heat transfer and thermodynamic efficiency of Ground Heat Exchangers (GHE) is crucial for maximizing the energy efficiency of Ground-coupled Heat Pump (GCHP) systems utilized in building heating and cooling applications. This study pioneers an effective approach of both the first and second laws of thermodynamics of the newly oval-shaped coaxial GHEs (oval-CGHEs), assessing heat transfer, thermohydraulic performance, and local entropy generation rate to explore the optimum design and operational conditions for heat exchange maximization and entropy generation minimization. Utilizing a three-dimensional numerical model validated by experimental results, this study examines the trade-offs between heat transfer improvements and entropy generation rate intensification of the oval-CGHEs in comparison to the typical circular-shaped CGHE (circle-CGHE) further than exploring the effect of key operational and design parameters and performing sensitivity analysis. The results reveal that oval-CGHEs exhibit higher irreversibility as a penalty for their superior heat transfer capabilities compared to traditional circular-shaped CGHEs (circle-CGHE), which can be mitigated by optimizing the position of the inner tube. Moreover, the study underscores the criticality of maintaining a balance between enhanced heat transfer and the associated rise in irreversibility, particularly concerning the factors of mass flow rates and installation depths.