Effects of Moisture Content on the Minimum Explosible Concentration of Aluminum Powder and the Related MechanismRead the full article
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Parametric Studies of Cement Production Processes
The cement industry is one of the most intensive energy consumers in the industrial sectors. The energy consumption represents 40% to 60% of production cost. Additionally, the cement industry contributes around 5% to 8% of all man-made CO2 emissions. Physiochemical and thermochemical reactions involved in cement kilns are still not well understood because of their complexity. The reactions have a decisive influence on energy consumption, environmental degradation, and the cost of cement production. There are technical difficulties in achieving direct measurements of critical process variables in kiln systems. Furthermore, process simulation is used for design, development, analysis, and optimization of processes, when experimental tests are difficult to conduct. Moreover, there are several models for the purpose of studying the use of alternative fuels, cement clinker burning process, phase chemistry, and physical parameters. Nonetheless, most of them do not address real inefficiency taking place in the processes, equipment, and the overall system. This paper presents parametric study results of the four-stage preheater dry Rotary Kiln System (RKS) with a planetary cooler. The RKS at the Mbeya Cement Company (MCC) in Tanzania is used as a case study. The study investigated the effects of varying the RKS parameters against system behaviour, process operation, environment, and energy consumptions. Necessary data for the modelling of the RKS at the MCC plant were obtained either by daily operational measurements or laboratory analyses. The steady-state simulation model of the RKS was carried out through the Aspen Plus software. The simulation results were successfully validated using real operating data. Predictions from parametric studies suggest that monitoring and regulating exhaust gases could improve combustion efficiency, which, in turn, leads to conserving fuels and lowering production costs. Composition of exhaust gases also depends both on the type of fuel used and the amount of combustion air. The volume of exit flue gases depends on the amount of combustion air and infiltrating air in the RKS. The results obtained from the study suggest a potential of coal saving at a minimum of about , which approximates to 76,126 tons per year at the current kiln feed of 58,000 kg·h-1. Thus, this translates to a specific energy saving of about 1849.12 kJ·kgcl-1, with relatively higher clinker throughput. In this vein, process modelling provides effective, safe, and economical ways for assessing the performance of the RKS.
An Accurate Iron Core Loss Model in Equivalent Circuit of Induction Machines
Iron core loss is the major loss in electrical machines. It performs up to 25% of total machine losses. The machine efficiency calculation requires an accurate prediction of losses. The accuracy of losses calculation depends largely on the equivalent circuit parameter determination and measurements. In this paper, an accurate procedure of iron core loss determination considering the variation effect of supply voltage, iron core temperature, rotor parameters due to skin effect, and magnetizing saturation. The iron core resistance is performed as main component in the equivalent circuit. This resistance is a function of supply voltage and used to calculate part of stray loss as well as iron core loss. The theoretical model is compared with practical results with high accuracy, which proves the validity of the proposed procedure.
Development of High Performance Airfoils for Application in Small Wind Turbine Power Generation
Small wind turbine power generation systems have the potential to meet the electricity demand of the residential sector in developing countries. However, due to their exposure to low Reynolds number (Re) flow conditions and associated problems, specific airfoils are required for the design of their blades. In this research, XFOIL was used to develop and test three high performance airfoils (EYO7-8, EYO8-8, and EYO9-8) for small wind turbine application. The airfoils were subsequently used in conjunction with Blade Element Momentum Theory to develop and test 3-bladed 6 m diameter wind turbine rotors. The aerodynamic performance parameters of the airfoils tested were lift, drag, lift-to-drag ratio, and stall angle. At , EYO7-8, EYO8-8, and EYO9-8 had maximum lift-to-drag ratios of 134, 131, and 127, respectively, and maximum lift coefficients of 1.77, 1.81, and 1.81, respectively. The stall angles were 12° for EYO7-8, 14° for EYO8-8, and 15° for EYO9-8. Together, the new airfoils compared favourably with other existing low Re airfoils and are suitable for the design of small wind turbine blades. Analysis of the results showed that the performance improvement of the EYO-Series airfoils is as a result of the design optimization that employed an optimal thickness-to-camber ratio () in the range of 0.85–1.50. Preliminary wind turbine rotor analysis also showed that the EYO7-8, EYO8-8, and EYO9-8 rotors had maximum power coefficients of 0.371, 0.366, and 0.358, respectively.
Comparative Study of the Grid Side Converter’s Control during a Voltage Dip
The modeling and control of a wind energy conversion system based on the Doubly Fed Induction Generator DFIG is the discussed theme in this paper. The purpose of this system was to control active and reactive power converted; this control is ensured thanks to the control of the two converters. The proposed control strategies are controlled by PI regulators and the sliding mode technique. In the present work a comparison of the robustness of the 2 controls of the grid side converter (GSC) during a voltage dip is shown. The simulation is carried out using the Matlab/Simulink software with a 300 kW generator.
Potential of Abattoir Waste for Bioenergy as Sustainable Management, Eastern Ethiopia, 2019
Our environment is facing serious problems of high volumes of waste generation and inadequate disposal system in worldwide particularly in developing countries. There is also lack of studies on quantification of abattoir waste and lack of workers awareness towards abattoir waste. Therefore, the purpose of the study was to estimate abattoir waste for bioenergy potential as sustainable management. A cross-sectional study was conducted in four selected abattoirs of Eastern Ethiopia from January 1st, 2018 to December 30th, 2018. The magnitude of abattoir waste composition was computed based on Aniebo mathematical computational from the actual number of slaughtered livestock. The study demonstrated that four selected abattoirs generate 1,606.403 ton of abattoir waste per year and using anaerobic digestion of about 85,139 m3/year of biogas and 111.25 ton/year of biofertilizer can be produced. The biogas or energy from the waste can replace firewood and charcoal and the expensive fossil fuels. Using Banks mathematical computation about 20,054.12 m3/year production of biogas could replace 20.56 ton/year of energy consumed by liquefied petroleum gas, kerosene, charcoal, furnace oil, petrol, and diesel in average. The current estimated biofertilizer (111.25 ton/year) from four abattoir sites can cover about 2,225 hectares/year with its advantage and efficiency of soil. When turned into cost, about $55,645 per year of price could estimate from biogas and biofertilizer. The study concluded that huge amount of biogas and dry biofertilizer yields could produce from abattoir waste through anaerobic digestion. Therefore, installing anaerobic digestion plant is recommended to ensure environmental safety and public health.
Removal of Hydrogen Sulfide from Biogas Using a Red Rock
The potential of red rock (RR) materials for the removal of H2S from biogas was studied. The rock samples were collected, sieved, and organized in various particle size ranges such as 0.32-250 μm, 250-500 μm, 500-750 μm, 750 μm-1 mm, and 1-1.5 mm. These samples were calcinated at the various temperatures as 500°C, 750°C, and 1000°C and then characterized for phase composition by energy-dispersive X-ray florescent technique, surface morphology by Zeiss Ultra Plus Field Emission Scanning Electron Microscopy (FE-SEM), and surface area by the Brunauer-Emmett-Teller (BET) method. The calcinated RR was filled in the bed reactor, and biogas was allowed to pass through the adsorbent while recording the inlet and exit concentration of H2S. The results show that particle size, calcination temperature, adsorbent mass, and biogas flow rate were parameters that influenced the removal efficiency and adsorption capacity of RR. The sample sieved at 0.32-250 μm and calcinated at a temperature of 1000°C showed 95% high removal efficiency and adsorption capacity of 0.37 g/100 g of the sorbent. Regeneration of spent materials when exposed to air, keep on by reuse in the column, appeared to have nearly similar removal efficiency as the original calcined sample. Thus, the overall performance of the material is promising, which is due to the presence of metals such as iron and magnesium, among others. Therefore, proving the successful elimination of contaminant, RR is an available material for biogas purification.