Electronic and Ionic Conductivities Enhancement of Zinc Anode for Flexible Printed Zinc-Air Battery

Zinc-air battery is considered a promising candidate for future energy applications due to its high energy density, safety and low cost. However, poor battery performance and low efficiency of zinc utilization, resulted from passivation effect of the zinc anode, is a major challenge. Thus, in this work, investigation of electronic and ionic conductivities enhancement of the zinc anode for flexible printed zinc-air battery has been carried out. The anode was made from a zinc-based ink, prepared from a mixture of zinc and zinc oxide particles. Carbon black, sodium silicate (Na2SiO3) and bismuth oxide (Bi2O3) were investigated for implementation on the anode. The results showed that performance of the battery increased when carbon black was introduced into the anode as the presence of carbon black improved electronic conductivity of the anode. Again, the battery performed better when Bi2O3 orNa2SiO3 was introduced due to the formation of solid electrolyte interface (SEI) on the anode. The SEI inhibits passivation of zinc active surfaces and provides effective electrolyte access. The battery with Bi2O3 provided the best performance. The highest performance was observed when Bi2O3 content reached 26wt.%. No significant improvement was observed whenBi2O3 concentration increased higher than 26 wt.%.Zinc-air battery is considered a promising candidate for future energy applications due to its high energy density, safety and low cost. However, poor battery performance and low efficiency of zinc utilization, resulted from passivation effect of the zinc anode, is a major challenge. Thus, in this work, investigation of electronic and ionic conductivities enhancement of the zinc anode for flexible printed zinc-air battery has been carried out. The anode was made from a zinc-based ink, prepared from a mixture of zinc and zinc oxide particles. Carbon black, sodium silicate (Na2SiO3) and bismuth oxide (Bi2O3) were investigated for implementation on the anode. The results showed that performance of the battery increased when carbon black was introduced into the anode as the presence of carbon black improved electronic conductivity of the anode. Again, the battery performed better when Bi2O3 or Na2SiO3 was introduced due to the formation of solid electrolyte interface (SEI) on the anode. The SEI inhibits passivation of zinc active surfaces and provides effective electrolyte access. The battery with Bi2O3 provided the best performance. The highest performance was observed when Bi2O3 content reached 26 wt.%. No significant improvement was observed when Bi2O3 concentration increased higher than 26 wt.%

Two-Dimensional Modeling of the Oxidative Coupling of Methane in a Fixed Bed Reactor: A Comparison among Different Catalysts

A proposed two-dimensional model of the oxidative coupling of methane (OCM) to C2 hydrocarbons (e.g., C2H4 and C2H6) in a fixed bed reactor operated under isothermal and non-isothermal conditions is described which can provide more accurate predictions of experimental data than the simplified one-dimensional model. The model includes a set of partial differential equations of the continuity, mass transfer and energy balance equations. The performance of the OCM using different catalysts was assessed in terms of CH4 conversion, C2 selectivity and C2 yield with respect to key operating parameters, such as feed temperature (973-1173 K), CH4/O2 ratio (3.4–7.5) and gas hour space velocity (GHSV) (18000-30000 h-1). The simulation results indicated that the Na-W-Mn/SiO2 catalyst exhibits the best performance among all of the catalysts. The C2 yield were 20.16% and 20.00% for non-isothermal and isothermal modes respectively which the OCM reactor is operated at a CH4/O2 ratio of 3.4, a feed temperature of 1073 K and a GHSV of 9720 h-1. An increase in the operating temperature increases the CH4 conversion but decreases the C2 selectivity. However, the effects of the CH4/O2 ratio and the GHSV exhibit an opposite trend to that of the operating temperature.A proposed two-dimensional model of the oxidative coupling of methane (OCM) to C2 hydrocarbons (e.g., C2H4 and C2H6) in a fixed bed reactor operated under isothermal and non-isothermal conditions is described which can provide more accurate predictions of experimental data than the simplified one-dimensional model. The model includes a set of partial differential equations of the continuity, mass transfer and energy balance equations. The performance of the OCM using different catalysts was assessed in terms of CH4 conversion, C2 selectivity and C2 yield with respect to key operating parameters, such as feed temperature (973 - 1173 K), CH4/O2 ratio (3.4 – 7.5) and gas hour space velocity (GHSV) (18000 - 30000 h-1). The simulation results indicated that the Na-W-Mn/SiO2 catalyst exhibits the best performance among all of the catalysts. The C2 yield were 20.16% and 20.00% for non-isothermal and isothermal modes respectively which the OCM reactor is operated at a CH4/O2 ratio of 3.4, a feed temperature of 1073 K and a GHSV of 9720 h-1. An increase in the operating temperature increases the CH4 conversion but decreases the C2 selectivity. However, the effects of the CH4/O2 ratio and the GHSV exhibit an opposite trend to that of the operating temperature

Optimal Design of Biodiesel Production Process from Waste Cooking Palm Oil

AbstractA design methodology for biodiesel production from waste cooking palm oil is proposed. The proposed method is flexible to the biodiesel process using various catalyst types: alkali and acid catalyst in homogenous and heterogeneous forms, and different process: enzyme process and supercritical process. A two-step approach of hydrolysis and esterification processes is also considered. Waste cooking palm oil consists of a mixture of triglyceride (e.g., trilaurin, tripalmitin, triolein, tristearin, trilinolein and trilinolenin) and free fatty acids (e.g., lauric acid, palmitic acid, stearic acid, oleic acid, linoleic and linolenic acid). A driving force approach and thermodynamic insight are employed to design separation units (e.g., flash separator and distillation) minimizing the energy consumption. Steady-state simulations of the developed biodiesel processes are performed and economic analysis is used to find a suitable biodiesel process. The results show that based on a net present value, the heterogeneous acid catalyzed process is the best process for biodiesel production. With the design methodology, the proposed biodiesel process can save the energy requirement of 41.5%, compared with a conventional process

Model-Based Analysis of an Integrated Zinc-Air Flow Battery/Zinc Electrolyzer System

This work aims at analyzing an integrated system of a zinc-air flow battery with a zinc electrolyzer for energy storage application. For efficient utilization of inherently intermittent renewable energy sources, safe and cost-effective energy storage systems are required. A zinc-air flow battery integrated with a zinc electrolyzer shows great promise as an electricity storage system due to its high specific energy density at low cost. A mathematical model of the system was developed. The model was implemented in MATLAB and validated against experimental results. The validation of the model was verified by the agreement between the simulation and experimental polarization characteristic. The behavior and performance of the system were then examined as a function of different operating parameters: the flow rate of the electrolyte, the initial concentration of potassium hydroxide (KOH) and the initial concentration of zincate ion. These parameters significantly affected the performance of the system. The influence of the hydrogen evolution reaction (HER) on the performance of the system was investigated and discussed as it significantly affected the coulombic efficiencies of both the zinc-air flow battery and the zinc electrolyzer. Optimal KOH concentration was found to be about 6–7 M. Whilst increased KOH concentration enhanced the discharge energy of the battery, it also increased HER of both the battery and the electrolyzer. However, higher initial concentration of zincate ion reduced HER and improved the coulombic efficiency of the system. Besides, a higher flow rate of electrolyte enhanced the performance of the system especially at a high charge/discharge current by maintaining the concentration of active species in the cell. Nevertheless, the battery suffered from a higher rate of HER at a high flow rate. It was noted that the model-based analysis provided better insight into the behavioral characteristics of the system leading to an improved design and operation of the integrated system of zinc-air flow battery with the zinc electrolyzer

Performance of Membrane-Assisted Solid Oxide Fuel Cell System Fuelled by Bioethanol

The membrane separation units for bioethanol purification including pervaporation and vapor permeation are integrated with the bioethanol-fuelled solid oxide fuel cell (SOFC) system. The preliminary calculations indicate that Hydrophilic type is a suitable membrane for vapor permeation to be installed after a hydrophobic pervaporation. Based on energy self-sufficient condition and data of available pervaporation membranes, the simulation results show that the use of vapor permeation unit after the pervaporation can significantly improve the overall electrical efficiency from 10.96% for the system with pervaporation alone to 26.56%. Regarding the effect of ethanol recovery, the ethanol recovery at 75% can offer the optimal overall efficiency from the proposed purification system compared to the ethanol recovery at 31.16% for the case with the single pervaporation

Two-Dimensional Mathematical Modeling of the Oxidative Coupling of Methane in a Membrane Reactor

The oxidative coupling of methane (OCM) in a dense BSCFO membrane reactor (MR) was theoretically studied using a two-dimensional reactor model. The simulation results indicated that increasing the operating temperature results in increased CH4 conversion and decreased C2 selectivity. An increase in the methane feed flow rate lowers the CH4 conversion but increases the C2 selectivity; however, the effect of the air flow rate on the OCM membrane reactor exhibits an opposite trend. The optimum configuration of the dense BSCFO-MR to provide the best performance was 0.018 m in diameter and 0.2 m in length at a GHSV of 38904.54 h-1 and temperature of 1073 K. Under these optimal conditions, the CH4 conversion is 43.713%, the C2 selectivity is 61.352% and the C2 yield is 26.82%

Hydrogen Production from Sorption Enhanced Biogas Steam Reforming Using Nickel-Based Catalysts

Hydrogen gas is a clean and sustainable fuel/energy carrier considered to be a possible alternative to fossil fuels. Sorption enhanced biogas steam reforming is a process which combines a CO2 adsorption unit with a hydrogen production unit. In the CO2 sorption section, CaO was selected as the adsorbent due to its high stoichiometric adsorption capacity. From the adsorption test, the highest adsorption capacity (0.2849 gCO2/gCaO) was achieved at a temperature of 873 K. Four types of bed arrangement were investigated using a feed gas with a CH4/CO2 ratio of 1.5, an S/C ratio of 3, a temperature of 873 K and at atmospheric pressure. The results indicate that the Type II system (Catalyst physical mixed with sorbent system packed in fixed bed quartz reactor, 0.8 g of 12.5 wt% Ni/Al2O3 mixed with 2 g of CaO) exhibits the highest improvement in CH4 conversion with the introduction of CO2 adsorption (93.0% and 81.7%, with and without CO2 sorption, respectively) and high purity hydrogen was produced (97.0% v/v and 62.3% v/v, with and without CO2 sorption respectively)

Performance Assessment of SOFC Systems Integrated with Bio-Ethanol Production and Purification Processes

The overall electrical efficiencies of the integrated systems of solid oxide fuel cell (SOFC) and bio-ethanol production with purification processes at different heat integration levels were investigated. The simulation studies were based on the condition with zero net energy. It was found that the most suitable operating voltage is between 0.7 and 0.85 V and the operating temperature is in the range from 973 to 1173 K. For the effect of percent ethanol recovery, the optimum percent ethanol recovery is at 95%. The most efficient case is the system with full heat integration between SOFC and bio-ethanol production and purification processes with biogas reformed for producing extra hydrogen feed for SOFC which has the overall electrical efficiency of 36.17%. However more equipment such as reformer and heat exchangers are required and this leads to increased investment cost