Electrochemical profile of an asymmetric supercapacitor using carbon-coated LiTi2(PO4)3 and active carbon electrodes

In this work, we reported an asymmetric supercapacitor in which active carbon (AC) was used as a positive electrode and carbon-coated LiTi₂(PO₄)₃ as a negative electrode in 1 M Li₂SO₄ aqueous electrolyte. The LiTi₂(PO₄)₃/AC hybrid supercapacitor showed a sloping voltage profile from 0.3 to 1.5 V, at an average voltage near 0.9 V, and delivered a capacity of 30 mAh g⁻¹ and an energy density of 27 Wh kg⁻¹ based on the total weight of the active electrode materials. It exhibited a desirable profile and maintained over 85% of its initial energy density after 1000 cycles. The hybrid supercapacitor also exhibited an excellent rate capability, even at a power density of 1000 W kg⁻¹, it had a specific energy 15 Wh kg⁻¹ compared with 24 Wh kg⁻¹ at the power density about 200 W kg⁻¹.     

Fuzzy modeling and particle swarm optimization for determining the optimal operating parameters to enhance the bio-methanol production from sugar cane bagasse

This work aims to maximize the production of bio-methanol from sugar cane bagasse through pyrolysis. The maximum value of the bio-methanol yield can be obtained as soon as the optimal operating parameters in a pyrolysis batch reactor are well defined. Using the experimental data, the fuzzy logic technique is used to build a robust model that describes the yield of bio-methanol production. Then, Particle Swarm Optimization (PSO) algorithm is utilized to estimate the optimal values of the operating parameters that maximize the bio-methanol yield. Three different operating parameters influence the yield of bio-methanol from sugar cane bagasse through pyrolysis. The controlling parameters are considered as the reaction temperature (°C), reaction time (min), and nitrogen flow (L/min). Accordingly, during the optimization process, these parameters are used as the decision variables set for the PSO optimizer in order to maximize the yield of bio-methanol, which is considered as a cost function. The results demonstrated a well-fitting between the fuzzy model and the experimental data compared with previous predictions obtained by an artificial neural network (ANN) model. The mean square errors of the model predictions are 0.11858 and 0.0259, respectively, for the ANN and fuzzy-based models, indicating that fuzzy modeling increased the prediction accuracy to 78.16% compared with ANN. Based on the built model, the PSO optimizer accomplished a substantial improvement in the yield of bio-methanol by 20% compared to that obtained experimentally, without changing system design or the materials used.     

A hierarchical modeling approach to the simulation and control of planar solid oxide fuel cells

The main aim of the paper is to propose hierarchical modeling as a suitable methodology to perform control-oriented analysis of planar solid oxide fuel cells (P-SOFC).     

Temperature, cycling, discharge current and self-discharge electrochemical studies to evaluate the performance of a pellet metal-hydride electrode

In this paper, we report electrochemical charge/discharge of hydrogen for a pellet metal-hydride electrode using an MmNi_5−XM_X alloy as active material. Strong dependence of temperature and discharge current was found for electrochemical applications. Pellet electrode showed good stability over 250 charge/discharge cycles. Self-discharge studies were carried out on completely charged electrode. The capacity of this electrode to absorb/desorb hydrogen could be defined as a stochastic function of some variables like temperature, cycling and discharge current conditions. More studies are in progress for calculating electrochemical parameters in these metal-hydride electrode systems.     

Maximize the operating profit of a SWRO-PRO integrated process for optimal water production and energy recovery

Pressure retarded osmosis (PRO) is a promising technology to reduce the specific energy consumption and the operating expenditure of a seawater reverse osmosis (SWRO) plant. In this study, a simple analytical PRO model is developed to predict the PRO performance as the dilution of draw solutions occurs. The model can predict the PRO performance with a high accuracy without carrying out complicated integrations and experiments. The operating profit of SWRO-PRO is also studied by calculating the profit generated for every m³ of seawater entering the process because maximizing the operating profit is the uttermost objective of the SWRO-PRO process. Based on the PRO analytical model, the operating profit and the dynamics of the SWRO-PRO process, a strategy has been proposed to maximize the operating profit of the SWRO-PRO process while maintaining the highest power density of the PRO membranes. This study proves that integration of SWRO with PRO can (1) push the SWRO to a higher recovery and maintain its high profitability, (2) effectively reduce the specific energy consumption of desalination by up to 35% and (3) increase the operating profit up to 100%.     

Evaluation of the performance of water-only cyclone for fine coal beneficiation using optimization process

A 3-levels and 3 variables Box-Behnken design combined with Response Surface Methodology (BBD-RSM) has been used to analyze the influence of outlet dimensions of Water-Only Cyclone (WOC) such as Vortex Finder Length (VFL), Vortex Finder Diameter (VFD) and Spigot Diameter (SPD). The effect of these variables on responses such as yield and ash was investigated. Results show that used coal with feed ash of 37.84% can be washed to reduce the ash up to 18.54%, and at this stage, washed coal yield was found at the level of 29.20%. The order of significance of the variables was found to be VFL> SPD> VFD> VFL.VFL for % Yield and VFL> VFD> SPD for % Ash.     

Comparison of conventional and spherical reactor for the industrial auto-thermal reforming of methane to maximize synthesis gas and minimize CO2

Auto-thermal reforming (ATR), a combination of exothermic partial oxidation and endothermic steam reforming of methane, is an important process to produce syngas for petrochemical industries. In a commercial ATR unit, tubular fixed bed reactors are typically used. Pressure drop across the tube, high manufacturing costs, and low production capacity are some disadvantages of these reactors. The main propose of this study is to offer an optimized radial flow, spherical packed bed reactor as a promising alternative for overcoming the drawbacks of conventional tubular reactors. In the current research, a one dimensional pseudo-homogeneous model based on mass, energy, and momentum balances is applied to simulate the performance of packed-bed reactors for the production of syngas in both tubular and spherical reactors. In the optimization section, the proposed work explores optimal values of various decision variables that simultaneously maximize outlet molar flow rate of H₂, CO and minimize molar flow rate of CO₂ from novel spherical reactor. The multi-objective model is transformed to a single objective optimization problem by weighted sum method and the single optimum point is found by using genetic algorithm. The optimization results show that the pressure drop in the spherical reactor is negligible in comparison to that of the conventional tubular reactor. Therefore, it is inferred that the spherical reactor can operate with much higher feed flow rate, more catalyst loading, and smaller catalyst particles.     

Particle Image Velocimetry study on the formation of gas bubbles and electrolyte velocity due to electrochemical reactions for different distances between the electrodes of Flooded Lead_ Acid batteries

During the charging processes in Flooded Lead_ Acid batteries (FLA), the production of gas bubbles occurs and it effects on the FLA performance. In this experimental investigation, the effect of distance between electrodes at different charge-discharge rates on the electrolyte flow velocity and bubbles behavior is investigated based on the Particle Image Velocimetry method. The reduction in the distance decreases the FLA capacity linearly at the same processes. It leads to an increase in the void fraction of bubbles and a decline in the diameter and rising velocity of the bubbles. The maximum diameter of the bubbles during the charging processes is very small compared to the distances between the electrodes. The effect of electrolyte velocity compared to the effect of the average rising velocity of bubbles on the FLA performance is negligible. The results show that the increase in the void fraction of the bubbles and the formation of bubble layers in the vicinity of the electrodes is the most critical factor at the increase of the ohmic resistance.     

A novel 1D approach for the simulation of unsteady reacting flows in diesel exhaust after-treatment systems

A new one-dimensional approach, based on the solution of the governing equations for unsteady, reacting and compressible flows has been developed for the simulation of the hydrodynamics, the transient filtration/loading and the catalytic/NO₂-assisted regeneration occurring in diesel particulate filters (DPF). The model is able to keep track of the chemical compounds, of the amount of soot transported by the flow, and it can estimate the increasing of back-pressure occurring in the exhaust system, due to the permeability variation of the porous wall and to the soot cake building up on the DPF porous surface. Further, a prediction of the oxidation of the deposited particulate induced by the Oxygen (collected in the exhaust gas), by the nitrogen dioxide (NO₂), by the carbon oxide (CO) and by the hydrocarbons (HC) converted along the diesel oxidation catalysts (DOC) is given.