Degradation of Ni-YSZ and Ni-GDC fuel cells after 1000 h operation: Analysis of different overpotential contributions according to electrochemical and microstructural characterization

Solid Oxide Fuel Cell (SOFC) technologies are emerging as potential power generation units with limited environmental impacts. However, the main challenges towards large scale commercial applications are high costs and low lifetime compared to currently used technologies. The present study aims at understanding degradation mechanisms in SOFCs through both experimental and modelling approaches. For this purpose, two state of the art fuel cell configurations based on Ni cermet fuel electrode (either YSZ-Yttrium Stabilised Zirconia or GDC-Gadolinium Doped Ceria), YSZ electrolyte and LSCF (Lanthanum Strontium Cobalt Ferrite oxide) air electrode were chosen. The cells were tested for 1000 hours with H2 rich mixture as fuel feed and air as oxidant. Cells were characterised at several H2/H2O ratios and temperatures with air or oxygen fed to the air electrode using different techniques. These allowed the identification of kinetic parameters to be implemented in an in-house 2D Fortran based model. The model was able to successfully simulate global cell behaviour as a function of local features, and it was validated with experimental I-V curves recorded prior and post durability operation. Moreover, post-mortem microstructure characterisation was also performed to fine-tune the model towards a more accurate prediction of the degradation influence on cell performance.

Ethnobotanical and Chemical Studies on Gezo Molasses from Quercus brantii Lindl. Acorns in Turkey

Oak molasses, called “Gezo,” have been produced by the local people of Southeastern Anatolia. In this study, the ethnobotanical characteristics, production stages, health effects, and chemical composition of Gezo were determined. Traditional Gezo molasses is produced from the acorn of Quercus brantii Lindl. The survey was carried out in seven provinces with large populations. Molasses samples were collected from local producers in the region alongside the local names, usage, sorting, and grading methods used by the local people. The total contents of phenolics and flavanoids were found to vary between the range of 1.60–2.56 mg gallic acid equivalents (GAE) and 0.62–0.72 mg rutin (RE) per g of Gezo molasses, respectively. Gezo displayed scavenging activity against DPPH radicals ranging from 7.57 to 9.44 µM Trolox/g. The CUPRAC assay results showed that molasses also possessed reducing power activity with a value of 8.57–10.20 µM Trolox/g. Gezo is typically consumed by local people as a breakfast food. However, it is also used for medical purposes to treat bronchitis, cough, asthma, and diabetes. The region’s oak species are used by locals for fuel, feed, handicrafts, and games.

Statistical Modeling and Performance Optimization of a Two-Chamber Microbial Fuel Cell by Response Surface Methodology

Microbial fuel cell, as a promising technology for simultaneous power production and waste treatment, has received a great deal of attention in recent years; however, generation of a relatively low power density is the main limitation towards its commercial application. This study contributes toward the optimization, in terms of maximization, of the power density of a microbial fuel cell by employing response surface methodology, coupled with central composite design. For this optimization study, the interactive effect of three independent parameters, namely (i) acetate concentration in the influent of anodic chamber; (ii) fuel feed flow rate in anodic chamber; and (iii) oxygen concentration in the influent of cathodic chamber, have been analyzed for a two-chamber microbial fuel cell, and the optimum conditions have been identified. The optimum value of power density was observed at an acetate concentration, a fuel feed flow rate, and an oxygen concentration value of 2.60 mol m−3, 0.0 m3, and 1.00 mol m−3, respectively. The results show the achievement of a power density of 3.425 W m−2, which is significant considering the available literature. Additionally, a statistical model has also been developed that correlates the three independent factors to the power density. For this model, R2, adjusted R2, and predicted R2 were 0.839, 0.807, and 0.703, respectively. The fact that there is only a 3.8% error in the actual and adjusted R2 demonstrates that the proposed model is statistically significant.

Elaboration of a new calculation procedure of hydrocarbon deposit layer thickness in fuel channels of heat engines and power plants

The article is devoted to theoretical research connected with elaboration of a new calculation procedure for hydrocarbon deposit layer thickness. A common problem of deposit formation in heat engines and power plants is thoroughly investigated. In addition, the wall composition, temperature, time and a number of life cycles, etc. are mentioned as key factors that have direct influence on this heat phenomenon. The paper describes thermophysical properties of deposits in fuel feed systems of different engines. The literature search and analysis did not reveal any similar procedures of calculation of hydrocarbon deposit layer thickness that could be connected with electrical properties of a wall or a deposit. The paper presents new equations for calculating the deposit formation thickness and rate based upon thermal and electrical nature of this process. These new equations led to elaboration of the new calculation procedure of hydrocarbon deposit layer thickness on a metal wall for any fuel channel of a heat engine or a power plant based on liquid hydrocarbon fuel or coolant. The new calculation technique was verified by experiments in aviation kerosene boiling in volume, which clarified special features in the application of new equations. Owing to the universal character of the proposed technique, it can be used for calculating the deposit formation virtually in all the known heat engines and power plants, for various operating conditions, for different metal wall compositions, at various fuel flow rates and pressures, temperature regimes inside fuel-feed and cooling channels.

Investigating the Potential of Recycling Flare-Source Hydrocarbon Gases in an Industrial Burner

Flare gas is considered a global environmental concern. Flaring contributes to wasting limited material and energy resources, economic loss and greenhouse gas emissions. Utilizing flared gas as fuel feed to industrial cracking furnaces grants advantages in terms of fuel economy and emissions reduction. This work presents the results obtained by ANSYS fluent simulation of a flare hydrocarbon gas utilized in a steam cracking furnace of ethylene process when combusting hydrocarbons flare gas in a low NOx burner. In addition, the study determined the suitability of different hydrocarbon fuel mixtures in satisfying the required adiabatic flame temperature. The flared stream is assumed to be inlet from both primary and secondary staged fuel burners. The simulation results illustrated the detailed temperature profiles along the furnace flue gas side. They also presented the influence of flare stream compositions and Wobbe Index (WI) on the temperature profile. It was found that having an alternative fuel with a heating value or WI similar to that of methane would not result in the same temperature profile of methane, as a current fuel source. In addition, using different excess air percentages has no linear effect on the burner’s temperature profile. However, the results showed that the best replacement of methane, as the main fuel source, is a flare mixture with the same WI of methane as well as a certain H2 content needs to be added to every flare mixture composition to reach the same temperature profile of methane

Secondary Agriculture towards Increasing Production and Sustainability

There is a pressing need for global agriculture to shift its focus to secondary agriculture in order to produce jobs as the world's population increases. The method of generating agricultural produce is biological in nature, making it a primary agriculture operation; but, when the raw produce is refined, it receives additional benefit, making it a secondary agriculture activity. Any farm related activity that uses the land or labor beyond the Kharif and Rabi seasons would qualify for a ‘Secondary Agriculture’ activity. India's scope for diversified agriculture is vast because of extensive arable land, multiple agro-climatic zones and a rich cafeteria of soils. However, India's reputation as a global agricultural powerhouse is ironically at odds with its farmers' low average wages. The road to higher agricultural Gross Value Added and farmers' income rests in efficient management of the post-production segment, comprising agri-logistics, processing and marketing. Agriculture generates raw materials that meet basic human requirements, and is considered as a primary economic activity. Of course, there are certain alternative agriculture activities like beekeeping, mushroom cultivation, backyard poultry, etc., which fall under the ambit of secondary agriculture. Secondary agriculture helps in using all parts of an agricultural produce, processing to enhance shelf-life, increasing total factor productivity, and generating additional jobs and income for farmers. It, thus, encompasses both food and non-food processing, and represents agro-processing. Income generation activities such as paddy straw fodder blocks, duck farming, honeybee keeping, mushroom cultivation, backyard poultry, among others, that do not compete with the time that is required for various inter-cultivation activities of primary agriculture production, qualify to be defined as a secondary agriculture. These Small-scale activities utilizes rural manpower, skills and locally available inputs efficiently. These enterprises can interact in space and/or time to achieve benefits through a synergistic resource transfer among enterprises, working closely such that waste from one part becomes a supply for another component of the system known as Integrated Farming System (IFS). Not only this but waste management is also one the important issue tackled with the help of secondary agriculture like leftover cane can be processed to produce by products of sugarcane. Thus, secondary agriculture realizes better productivity, profitability and sustainable production systems that would help to solve the fuel, feed and energy crisis, create more employment avenues, ensure regular income and encourage agriculture-oriented industry.

Automatic Unloading Liquid Rocket Engine Fuel Feed System Booster Pump Radial Thrust Bearings from Axial Force

Increasing the suction capacity, efficiency and energy parameters of high-speed pumps is an important task in the development of power systems in the aerospace industry, as well as in their application in energy and oil production. With improved cavitation properties, the pumps can operate at a higher shaft speed, and at its given value - with lower cavitation reserves, i.e. at a reduced inlet pressure. When the shaft speed increases, the pump weight and overall dimensions decrease. To increase the anti-cavitation qualities of pumps in the power system, auxiliary (booster) pumping units are used, creating the pressure necessary for the cavitation-free operation of high-pressure and high-speed main pumps of the engine fuel supply system. In accordance with its purpose, the booster pump must provide the required supply pressure of the specified flow rate at the lowest possible liquid pressure at the inlet. At the same time, the efficiency of the booster pump unit should be maximum, and the overall dimensions and weight should be minimal. The last two characteristics predetermine the maximum possible number of revolutions of the pump shaft. Ensuring the operability of the ball-bearing supports of the fuel supply units is one of the most important and complex tasks in the development of modern and promising liquid rocket engines (LRE), especially reusable ones. This task has always been one of the priorities in the fine-tuning the fuel feed units of such engines. The article proposes a method for calculating and controlling the unloading liquid rocket engine booster pump radial thrust bearings from axial force. The method can be applied in the entire range of liquid rocket engine calculations. The further development of this work will be mathematical modeling of the operation of the booster pump automatic axial force unloading.

Combustion Characteristics of Mui and Taru Basin Coal in a Fluidized Bed Combustor

Coal reserves at Mui and Taru in Kitui and Kilifi counties in Kenya are estimated to provide over 400 million tons. Being new discoveries, their properties were investigated using the ASTM standards, while the combustion characteristics were studied in a fluidized bed combustor (FBC). Proximate analyses of the Mui1, Mui2, and Taru coal samples were as follows: moisture content 3.75, 5.48, and 3.53%; volatile matter 59.25, 58.05, and 55.10%; ash content 9.25, 11.48, and 24.63%; and fixed carbon 27.80, 25.00, and 16.75%, respectively. Ultimate analysis for Mui1, Mui2, and Taru coal samples is as follows: sulphur wt.% 1.94, 1.89, and 1.07; carbon 65.68, 60.98, and 51.10%; hydrogen 5.97, 5.70, and 5.09%; nitrogen 0.92, 0.94, and 1.00%; and oxygen 11.62, 12.33, and 11.13%, respectively. Temperature–weight loss analysis showed that for Mui and Taru basin coal, devolatilization starts at 200°C and 250°C, and combustion was complete at 750°C and 650°C, respectively. The maximum temperature obtained in FBC was 855°C at 700 mm height, just above the point of fuel feed, while the minimum was 440°C at height of 2230 mm. Maximum pressure drop was 1.02 mbars at 150 mm, while minimum was 0.67 mbars at 700 mm from the base. Gross calorific values were Mui1 coal, 27090 kJ/kg (grade A), Mui2 coal, 25196 kJ/kg (grade B), and the Taru coal, 21016 kJ/kg (grade C). Flue gas analysis for Taru and Mui coal gave hydrogen sulfide as 20 ppm and 6 ppm, maximum carbon monoxide of 2000 ppm at 600°C, and a decrease in oxygen as combustion progressed to a minimum of 15%, followed by an increase to 20.3%, suggesting depletion of coal. Based on the findings, the coal samples were suitable for commercial use.