Journal of Engineering and Technological Sciences
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Development of a Respirable Dust Mitigation System for a High Longwall Face at Sihe Colliery in China - a Case Study
Get PDFDust is a major hazard in underground coal mines that threatens the work health and safety of coal miners. The dust issue becomes increasingly significant with the development of highly mechanized coal mining. This issue is particularly serious at the high longwall faces of the Sihe colliery in China as the concentration of dust, in particular respirable dust, at these faces far exceeds the regulatory dust limits. Field testing and computational fluid dynamics (CFD) simulations were conducted to understand the sources of dust generation and its dynamic movement in the #5301 longwall face of high-cutting height at the colliery. The investigation results showed that shearer generated dust was minimal during the coal cutting operation; that face spalling and chock movement were the main dust generating sources, causing significant contamination to the walkway; and that the majority of dust particles from the face (regardless of source) eventually disperse into the main gate, where the dust concentration was greater than 500 mg/m3. These findings were used to develop an effective coal dust mitigation system involving the installation of dust scrubbers, curtains, and venture and crescent sprays. The results of CFD modeling indicate that the dust concentration could be significantly reduced by adopting the new dust mitigation system
Non-linear Isotherm Models, Cadmium Kinetics, and Biosorption Thermodynamics of Dried Biomass of Native Aphanothece sp. in a Batch System
Get PDFDried biosorbent was prepared from Aphanothece sp. cyanobacteria harvested from a photobioreactor system fed with atmospheric carbon dioxide. Cadmium-ion biosorption of the prepared biosorbent from aqueous solution was characterized by non-linear (Langmuir, Freundlich and Dubinin"“Radushkevich) isotherms, non-linear kinetics (pseudo first-order and pseudo second-order) and thermodynamic analysis. The optimum conditions were pH 8.0, 30°C, 0.1 g/L biomass, and 60 min contact time. The biosorption efficiencies exceeded 90%. The low-range data (initial Cd concentration C0 = 1.09"“6.23 mg/L) and high-range data (C0 = 5.41"“83.07 mg/L) were best fitted to the Langmuir model, with maximum uptake capacities of 12.01 and 187.5 mg/g (R2 = 0.995 and 0.996). In the Dubinin"“Radushkevich isotherm model, the mean biosorption energy was 12.91 kJ/mol, suggesting that ion exchange was the working mechanism. The biosorption apparently followed pseudo second-order kinetics (R2 = 0.994"“0.999; k2 = 2.04 E-03 to 3.86 E-02 g/mg min). The biosorption process was energetically feasible (∆G0 = −13.47"“−8.88 kJ/mol), exothermic (∆H0 = −74.82 kJ/mol) and tended to become more ordered (∆S0 = −0.204 kJ/mol K) towards the end of the process. The biosorbent was reusable through three adsorption/desorption cycles in 1 M HCl
Probabilistic Modeling of Seismic Risk Based Design for a Dual System Structure
Get PDFThe dual system structure concept has gained popularity in the construction of high-rise buildings over the last decades. Meanwhile, earthquake engineering design provisions for buildings have moved from the uniform hazard concept to the uniform risk concept upon recognizing the uncertainties involved in the earthquake resistance of concrete structures. In this study, a probabilistic model for the evaluation of such risk is proposed for a dual system structure consisting of shear walls or core walls and a moment frame structure as earthquake resistant structure. Uncertainties in the earthquake resistance of the dual system structure due to record-to-record variability, limited amount of data, material variability and structure modeling are included in the formulation by means of the first-order second-moment method. The statistics of resistance against earthquake forces are estimated by making use of incremental nonlinear time history analysis using 10 recorded earthquake histories. Then, adopting the total probability theorem, the reliability of the structure is evaluated through a risk integral scheme by combining the earthquake resistance of the structure with the annual probability of exceedance for a given location where the building is being constructed
Seismic Pore Water Pressure Relief Wells for Gravel ColumnâBed System
Get PDFLiquefaction mitigation can be achieved by dissipating seismic pore pressures. The research reported in this paper elaborates the effectiveness in dissipating seismic pore pressures of a gravel bed and relief well system using gravel columns in a case study in Cilacap, Indonesia. Seismic pore pressure generation was analyzed using commonly available methods in liquefaction analysis. The evaluated pore pressures in the sand layer and gravel columns were used in a 2D dissipation analysis using finite-difference consolidation equation solutions. The results of this study showed that a simple and cost-effective relief well and gravel bed or strip system can effectively dissipate excess pore pressures in the sand layer and gravel columns to a maximum residual pore pressure below 40%, thus reducing liquefaction potential as well as protecting the foundations in the sand
Cultivation Strategy for Freshwater Macro- and Micro-Algae as Biomass Stock for Lipid Production
Get PDFIn this research, an algae cultivation strategy was studied. Integrating algae cultivation with wastewater treatment is currently seen as one of the most economical ways of producing algae biomass. A combination of an anaerobic baffled reactor (ABR) and a constructed wetland (CW) was applied for treating domestic wastewater with an additional collection tank for improving effluent quality. The effluent produced from the three stages was used as algae cultivation media and suplemented with 10% bold basal medium (BBM). The results showed both micro- and macro-algae growth and their lipid contents were higher when they were grown in effluent-BBM (9:1 v/v) media. The lipid content of the micro-algae mixed culture was 16.5% while for macro-algae Oedogonium sp and Cladophora sp it was 6.90% and 6.75% respectively
Application of Fin System on Adsorption of Methylene Blue Dye using Adsorbent Coating Layer: Mathematical Formulae
Get PDFTreatment of dye solution using fin system is one of the new adsorption application techniques that can replace expensive conventional adsorption treatment units that mostly used in industries. The fins will work as the media of adsorbent coating and immerse in a tank containing dye wastewater. The purpose of present study is to develop simple mathematical equations for the fin's system by using adsorbent coating layer (ACL) as an adsorbent. By installing coated fins inside the tank, the concentration of dye can be easily reduced up to 90 %. The equilibrium adsorption data was best met by the Langmuir isotherm, indicating the adsorption is homogeneous surface and in monolayer state. The mathematical formula developed from the isotherm model of adsorption was revealed to be used in large scale application for the removal of methylene blue dye from industrial wastewater since the percent error between calculated and experimental values were less than 15%
A Comprehensive Comparison Study of Empirical Cutting Transport Models in Inclined and Horizontal Wells
Get PDFIn deviated and horizontal drilling, hole-cleaning issues are a common and complex problem. This study explored the effect of various parameters in drilling operations and how they affect the flow rate required for effective cutting transport. Three models, developed following an empirical approach, were employed: Rudi-Shindu's model, Hopkins', and Tobenna's model. Rudi-Shindu's model needs iteration in the calculation. Firstly, the three models were compared using a sensitivity analysis of drilling parameters affecting cutting transport. The result shows that the models have similar trends but different values for minimum flow velocity. Analysis was conducted to examine the feasibility of using Rudi-Shindu's, Hopkins', and Tobenna's models. The result showed that Hopkins' model is limited by cutting size and revolution per minute (RPM). The minimum flow rate from Tobenna's model is affected only by well inclination, drilling fluid weight and drilling fluid rheological property. Meanwhile, Rudi-Shindu's model is limited by inclinations above 45°. The study showed that the investigated models are not suitable for horizontal wells because they do not include the effect of lateral section