Research on Physical and Chemical Properties of Blended Bio-Oil Based on Fractionation

To improve the properties of bio-oil, a new method was proposed that does not involve introduction of any energy medium. An ether-soluble fraction (ES), a dichloromethane soluble fraction (DCMS), and a dichloromethane insoluble fraction (DCMIS) of bio-oil were obtained using ether and dichloromethane as extraction solvents. The same amount of each fraction (10 g) was blended into bio-oil with a certain quantity of 100 g. The three samples were then placed in sealed vials and heated for 12, 60, and 180 h at both 60 °C and 80 °C in an oil bath. Based on the aging properties of the three fractions, blended bio-oil was prepared using ES and DCMS in certain volume ratio. The total yield of the three fractions combined was around 90 wt%; the weight loss was thought to be due to the volatilization of low molecular weight matter and water during the process of solvent evaporation using a rotary evaporator. The aging test results indicated that the DCMIS fraction had the poorest properties compared with ES and DCMS such as acid number, water content and viscosity. In order to get the best properties of blended bio-oil, the optimal volume ratio of ES/DCMS was 1/2 according to the aging test

Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in-depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three-dimensional numerical model was established by COMSOL, where the build-in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure

Optimization and Performance Analysis of a Distributed Energy System Considering the Coordination of the Operational Strategy and the Fluctuation of Annual Hourly Load

The operation strategies of a distributed energy system (DES) are usually proposed according to the electrical load (FEL) and the thermal load (FTL), which take the cooling/heating load or electric load as unique constraint conditions that result in a too high or too low equipment load rate. This paper proposes a new hybrid operation strategy (HOS) that takes the full utilization of natural gas and the minimization of power consumption from the power grid as constraints and coordinates the cooling/electricity ratio and heating/electricity ratio of buildings and equipment. In the optimization phase of a DES, an optimization method based on the discretization of the load is proposed to investigate the influence of the uncertainty of the load on the DES, which helps to avoid repeated load simulations and provides stronger adjustability by quoting the normal distribution function to obtain multiple sets of load data with different fluctuations. Further, a multi-objective optimization model combining the genetic algorithm (GA) and mixed integer linear programming algorithm (MILP) was established to find the optimal configuration of equipment capacities by comprehensively considering the annual total cost, carbon emissions, and energy efficiency of the DES. Finally, an office building example was used to validate the feasibility of the above theories and methods. Compared with the FEL and FTL, the HOS reduced the energy waste of the DES by 19.7% and 15.5%, respectively. Compared with using a typical daily load, using an annual hourly load to optimize the DES-HOS produced a better comprehensive performance and lower adverse impacts derived from load fluctuations

Prediction of Acute Kidney Injury Following Isolated Coronary Artery Bypass Grafting in Heart Failure Patients with Preserved Ejection Fraction Using Machine Leaning with a Novel Nomogram

Background: The incidence of postoperative acute kidney injury (AKI) is high due to insufficient perfusion in patients with heart failure. Heart failure patients with preserved ejection fraction (HFpEF) have strong heterogeneity, which can obtain more accurate results. There are few studies for predicting AKI after coronary artery bypass grafting (CABG) in HFpEF patients especially using machine learning methodology. Methods: Patients were recruited in this study from 2018 to 2022. AKI was defined according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria. The machine learning methods adopted included logistic regression, random forest (RF), extreme gradient boosting (XGBoost), gaussian naive bayes (GNB), and light gradient boosting machine (LGBM). We used the receiver operating characteristic curve (ROC) to evaluate the performance of these models. The integrated discrimination improvement (IDI) and net reclassification improvement (NRI) were utilized to compare the prediction model. Results: In our study, 417 (23.6%) patients developed AKI. Among the five models, random forest was the best predictor of AKI. The area under curve (AUC) value was 0.834 (95% confidence interval (CI) 0.80–0.86). The IDI and NRI was also better than the other models. Ejection fraction (EF), estimated glomerular filtration rate (eGFR), age, albumin (Alb), uric acid (UA), lactate dehydrogenase (LDH) were also significant risk factors in the random forest model. Conclusions: EF, eGFR, age, Alb, UA, LDH are independent risk factors for AKI in HFpEF patients after CABG using the random forest model. EF, eGFR, and Alb positively correlated with age; UA and LDH had a negative correlation. The application of machine learning can better predict the occurrence of AKI after CABG and may help to improve the prognosis of HFpEF patients

The effect of H2O on the oxy-fuel combustion of a bituminous coal char particle in a fluidized bed: Experiment and modeling

Oxy-fuel fluidized bed (FB) combustion is considered one of the promising ways to control CO2 emission from coal-fired power plants. The effect of H2O on the char conversion during wet flue-gas recycle, in which the H2O concentration could be around 40%, is still not well understood. To this end, experiments and modeling were performed in this work. Combustion tests with bituminous coal char were carried out in an electrically heated fluidized bed in O2/CO2, O2/H2O and O2/CO2/H2O for various O2, CO2 and H2O concentrations at the bed temperature of 850 \ub0C. At the same time, the influence of the bed temperature and the char size on char combustion was investigated in O2/CO2/H2O atmosphere. A thermocouple was inserted into the center of the char particle to measure the particle temperature, from which the char combustion characteristics were determined and analyzed. The results indicate that the participation of H2O in the combustion atmosphere enhances the carbon conversion, and it also reduces the particle temperature. A transient char-particle conversion model, taking into account heat and mass transfer from the bed to the particle and heterogeneous combustion and gasification of char, was developed to quantitatively examine the role of H2O. The model shows a good ability to predict the measured char-temperature history. Simulations were carried out to establish the role of H2O in O2/H2O and O2/CO2/H2O as in the FB experiments. The model was used to analyze the peak temperature and the burnout time of a char particle, as well as the relative contributions to the consumption of the carbon in the char by O2 (combustion), and CO2 and H2O (gasification). The results indicate that the endothermic char-H2O reaction is the main reason for the prolongation of the burnout time of char and the decrease in the particle temperature in O2/CO2/H2O as compared in O2/CO2. During wet flue-gas recycle, char-O2 still accounts for a major part of the total carbon consumption, but the contribution of char-H2O to the overall carbon consumption increases with the H2O concentration and cannot be ignored (i.e. when the H2O concentration attains 30%, the contribution of the char-H2O reaction to the overall carbon consumption is 14%). However, the contribution of char-CO2 to the char conversion is limited

Dehydroxylation and Structural Distortion of Kaolinite as a High-Temperature Sorbent in the Furnace

As a high-temperature sorbent, kaolinite undergoes the flash calcination process in the furnace resulting in the dehydroxylation and structural distortion, which are closely related to its heavy metal/alkali metal adsorption characteristics. We investigated the flash calcination of kaolinite by the experiments using a drop tube furnace and by the characterization of flash-calcined products using thermogravimetric-differential scanning calorimeter (TG-DSC), X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR)and nuclear magnetic resonance (NMR). There were three kinds of hydroxyl groups in kaolinite during flash calcination at 800–1300 °C, E-type (~50%, easy), D-type (~40%, difficult) and U-type (~10%, unable) according to the removal difficulty. The hydroxyl groups activation was believed to be the first step of the removal of E-type and D-type hydroxyl groups. The kinetics model of dehydroxylation groups at 900–1200 °C was established following Arrhenius equation with the activation energy of 140 kJ/mol and the pre-exponential factor of 1.32 × 106 s−1. At 800 °C, the removal of E-type hydroxyl groups resulted in the conversion of a part of VI-coordinated Al in kaolinite to V-coordinated Al and the production of meta-kaolinite. When the temperature rose up to 1200 °C, mullite was produced and a part of V-coordinated Al converted to IV-coordinated Al and VI-coordinated Al. Finally, the adsorption characteristics of kaolinite was discussed according to the results of dehydroxylation and structural distortion

Typical Gaseous Semi-Volatile Metals Adsorption by Meta-Kaolinite: A DFT Study

Kaolinite can be used as in-furnace adsorbent to capture gaseous semi-volatile metals during combustion, incineration, or gasification processes for the purposes of toxic metals emission control, ash deposition/slagging/corrosion inhibition, ultrafine particulate matter emission control, and so on. In this work, the adsorptions of typical heavy metals (Pb and Cd) and typical alkali metals (Na and K) by meta-kaolinite were investigated by the DFT calculation. The adsorption energies followed the sequence of NaOH-Si surface > KOH-Si surface > PbO-Al surface ≈ CdO-Al surface ≈ NaOH-Al surface > KOH-Al surface > NaCl-Al surface ≈ Na-Si surface > Na-Al surface > KCl-Al surface > Pb-Al surface > PbCl2-Al surface > CdCl2-Al surface ≈ K-Si surface ≈ PbCl-Al surface > K-Al surface > CdCl-Al surface > NaCl-Si surface > KCl-Si surface > Cd-Al surface. Si surface was found available to the adsorptions of Na, K, and their compounds, although it was invalid to the adsorptions of Pb, Cd, and their compounds. The interactions between adsorbates and surfaces were revealed. Furthermore, the discussion of combining with the experimental data was applied to the subject validity of calculation results and the effect of chlorine on adsorption and the effect of reducing atmosphere on adsorption

Template Synthesis of Nitrogen Self-Doped Hierarchical Porous Carbon with Supermicropores and Mesopores for Electrical Double-Layer Capacitors

Nitrogen self-doped hierarchical porous carbon for electrical double-layer capacitors was synthesized by direct carbonization of bean dregs-based tar with potassium acetate as the template agent. The pore structure parameters and chemical element composition were adjusted by varying the heating rate during the carbonization process. The electrochemical properties of the electrode materials were evaluated in a three electrode system with 6 M KOH as the electrolyte. The resultant bean dregs-based porous carbons (BDPCs) exhibited high specific surface area, unique hierarchical architecture (consisting of supermicro- and mesopores), and medium nitrogen content (0.66 to 0.78%). The BDPC-10 sample had the highest specific surface area of 1610 m2/g and reasonable pore size distribution, and consequently exhibited an excellent specific capacitance of 363.7 F/g at the current density of 1 A/g. Nevertheless, the capacitance was reduced to 280.5 F/g at 3 A/g, giving a capacitance retention ratio of 77.1%. This study suggests a facile and environmentally friendly template synthesis process for supercapacitor electrode materials preparation, but it also faces challenges to increase the rate capability

NiS/MoS2 Mott-Schottky heterojunction-induced local charge redistribution for high-efficiency urea-assisted energy-saving hydrogen production

Urea-assisted water electrolysis possesses the prospective prospect for high-efficiency hydrogen production by replacing oxygen evolution reaction (OER) with thermodynamically more favorable urea oxidation reaction (UOR). Modulating the electronic structure of electrocatalysts through constructing metal-semiconductor heteminterface represents an effective strategy to promote the electrochemical performances. Herein, we construct a Mott-Schottky bifunctional electrocatalyst by in-situ growth of NiS/MoS2 hetero-nanoflowers on the conductive carbon cloth (CC) substrate (abbreviated as NiS/MoS2@CC hereafter) for both hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Thanks to the Mott-Schottky effect, the self-driven charge transfer occurs across the NiS/MoS2 heterointerfaces, which results in the built-in electric field, the accelerated charge transfer rate, and the modified chemisorption free energies for reaction intermediates, ultimately expediting the dissociation of water and urea molecules. Consequently, the as-fabricated NiS/MoS2@CC electrode only requires an overpotential of 87 mV for hydrogen evolution reaction (HER) in 1.0 M KOH and a potential of 1.36 V for UOR in 1.0 M KOH solution with 0.5 M urea to attain a current density of 10 mA cm(-2), respectively. Moreover, when served as the free-standing anode and cathode simultaneously, the NiS/MoS2@CC-assembled urea electrolyzer requires a cell voltage of 1.46 V at 10 mA cm(-2), which is 200 mV smaller than that of the pure water splitting counterpart. This study may deepen the understanding of electronic modulation via Mott-Schottky establishment

NiS/MoS2 Mott-Schottky heterojunction-induced local charge redistribution for high-efficiency urea-assisted energy-saving hydrogen production

Urea-assisted water electrolysis possesses the prospective prospect for high-efficiency hydrogen production by replacing oxygen evolution reaction (OER) with thermodynamically more favorable urea oxidation reaction (UOR). Modulating the electronic structure of electrocatalysts through constructing metal-semiconductor heteminterface represents an effective strategy to promote the electrochemical performances. Herein, we construct a Mott-Schottky bifunctional electrocatalyst by in-situ growth of NiS/MoS2 hetero-nanoflowers on the conductive carbon cloth (CC) substrate (abbreviated as NiS/MoS2@CC hereafter) for both hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Thanks to the Mott-Schottky effect, the self-driven charge transfer occurs across the NiS/MoS2 heterointerfaces, which results in the built-in electric field, the accelerated charge transfer rate, and the modified chemisorption free energies for reaction intermediates, ultimately expediting the dissociation of water and urea molecules. Consequently, the as-fabricated NiS/MoS2@CC electrode only requires an overpotential of 87 mV for hydrogen evolution reaction (HER) in 1.0 M KOH and a potential of 1.36 V for UOR in 1.0 M KOH solution with 0.5 M urea to attain a current density of 10 mA cm(-2), respectively. Moreover, when served as the free-standing anode and cathode simultaneously, the NiS/MoS2@CC-assembled urea electrolyzer requires a cell voltage of 1.46 V at 10 mA cm(-2), which is 200 mV smaller than that of the pure water splitting counterpart. This study may deepen the understanding of electronic modulation via Mott-Schottky establishment