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Thermal, Kinetic and Safety Aspects of a Thermally In-Stable Reaction Mixture: Mastering the Thermal Runaway Situations
Get PDF This article reports to the hazard evaluation studies of a laboratory scale reaction involving 1, 3-diethyl propanedioate and Fuming Nitric acid to form diethyl 2-nitropropanedioate. The process has been optimized and scheduled to the pilot scale batches after process safety evaluation. Fuming Nitric acid addition to 1,3-Diethyl propanedioate at 7°C is highly exothermic reaction with an adiabatic-temperature-rise of 113°C according for RC1e experiment. But the mixture strongly shows an exothermic event at an onset temperature of 60°C to a maximum temperature of 538°C within few seconds with a massive pressure rise in ARC experiment. Indeed, these hazard evaluation experimental results are clear to understand the hazards of the reaction in case of failing in controlled addition, which helped us to redesign the laboratory scale process and notified the required control measures at plant scale
Gasification of Biomass in an Updraft Fixed Bed Reactor: Effect of Viscous Models
Get PDF A numerical study to investigate the influence of viscous models in the biomass gasification in an updraft fixed bed reactor is presented. The unsteady simulations were performed using finite volume method of ANSYS Fluent. A two-dimensional axisymmetric transient model was used to simulate the biomass gasification process. The model is based on the Euler-Euler multiphase formulation. The reactive gas-solid flow considers both homogeneous and heterogeneous reactions (drying, pyrolysis, combustion and gasification). Source terms and chemical kinetics are incorporated into the code using user-defined functions programmed in C. Results are validated with experimental data available in the literature for gasification in a continuous reactor. Temperatures and mole fractions of CO, CO2, CH4, Tar, and H2 at the reactor exit are in good agreement with the experimental measurements. Laminar model is agreed with experimental data for net calorific value, however, discrepancies are observed when the mixture model is used. This work provides a methodology for studying gasification in fixed beds using a commercial CFD code which can be used in gasifier design, analysis, and optimization
Numerical Modeling of Turbulent Flow Inside the Centrifugal Blower
Get PDF In this paper, turbulent flow inside the centrifugal blower has been studied numerically. The computational simulation is conducted by employing the Reynolds Averaged NavierStokes (RANS) approach. The standard k-ɛ model with enhanced wall treatment has been implemented for modeling the turbulent flow. Effects of different angular velocities have been studied on static pressure and mass flow rate. The numerical results shows that static pressure and mass flow rate significantly increase as the angular velocity of blades increases
Managing Total Phosphorus Dynamic in a Small Rural/Urban Watershed using Geochemical Inference
Get PDF Watershed fingerprinting or geochemical tracing of hydrologic pathways and processes involves the strategic spatial and temporal collection of water samples for chemical indicators. We used the stable isotopes of hydrogen and oxygen and major cations and anions found in fresh water systems to infer total phosphorus (TP) movement and storage in a small Midwestern rural/urban watershed. Typically in Minnesota, water chemistry is dominated by calcium and magnesium charge balanced by bicarbonate alkalinity unless altered by human activity. Ion concentrations will vary in a landscape depending on the relative amounts of new precipitation added to the sampled water. Pre-event water found in lakes, wetlands and groundwater are influenced by biotic and abiotic factors such as organic carbon and soil/rock mineralogy. Results of this study suggested that historically high concentrations of TP from years of wastewater treatment plant discharge were trapped in a down gradient wetland system. We inferred that new cleaner wastewater discharge may drive a change in equilibrium phosphorus concentration between sediment stored TP and event-based flow. Redirecting flow around TP wetland sinks will help prevent long-term down river water quality impairment
Prediction of Hydrostatic Pressure and Downhole Mud Temperatures While Drilling
Get PDFIn deep and hot wells, the densities of water/oil muds and brines (geofluids) can be significantly different from those measured at surface conditions. As a result, bottom-hole pressures predicted with constant mud densities can be in error by hundreds of psig. Determining accurate the density of drilling mud (the density of the formation fluids) under downhole conditions needs for calculating the actual hydrostatic pressure in a well and predicting differential pressure at the bottom-hole. This will help to reduce the fluid losses resulting from miscalculated pressure differentials. In areas with high geothermal gradients, the thermal expansion of drilling muds can lead to unintentional underbalance, and a kick may occur. In this paper we demonstrate the use of an empirical equation for the downhole circulating mud temperature as well as the early derived analytical equation for the drilling mud hydrostatic pressure. A field example is presented
Eddy Dissipation Combustion Modeling of Turbulent Reacting Flow
Get PDF In this paper specious transport and gaseous combustion have been modeled numerically using computational fluid dynamics method. A cylindrical combustor burning methane (CH4) in air is studied using the eddy-dissipation model. Eddy dissipation combustion model has been coupled with the standard k-ɛ model to simulate this highly complex turbulent reactive fluid flow field. Effects of air and fuel velocities have been investigated on the reactant mass fractions, temperature and velocity profiles and NOX production
Understanding the Consequences of Soil Amendments on Host Selection by a Maize Viral Vector (CicadulinambilaNaudé)
Get PDFThe significance of applying different rates of soil elements on host selection by a viral vector was studied in a confined habitat, to understand the mechanism of host selection by the leafhopper (CicadulinambilaNaudé), a vector of Maize Streak Virus Disease (MSV). Field collected leafhoppers were used in a screen house to assess insect settling preferences by evaluating insect behavior towards host plants, exposed to different rates of nitrogen and phosphorus fertilizers (0, 25, 50 and 75kg/ha.). Analysis of the two elements in the host plant tissues showed significant variation in levels of percent nitrogen (% N: p = 0.031) and phosphorus (% P: p = 0.001). Similarly, a significantly higher number of insects settled on plants treated with a higher rate of nitrogen (21%) and phosphorus (44%), compared to low rates of the same (9% and 28% respectively) (p = 0.019). Host choice by insects was significantly longer phosphorus treated hosts (four days) than nitrogen treated (three days). No significant differences were detected in the analysis of host plants for % neutral detergent fibers, acid detergent fibers, lignin and tannins. However, regression analysis revealed that neutral detergent fibers had significantly negative relationship with nitrogen fertilizer, while and phosphorus showed a negative relationship with lignin. This study showed that fertilizer amendments can critically affect host attack by leafhoppers with amplifications on viral disease transmission
Reduce Distillation Column Cost by Hybrid Particle Swarm and Ant Colony Optimization Technique
Get PDFA novel method for optimum design of plate type distillation column integrating the equilibrium, hydraulic and economic calculations is presented in the present paper. The present study explores the use of non-traditional optimization technique: called hybrid Particle swarm optimization (PSO) and Ant colony optimization (ACO), for design optimization of plate type distillation column from economic point of view. The optimization procedure involves the selection of the major plate geometric parameters such as hole diameters, ratio of downcomer area to tower area, weir height, fractional hole area in tray, tray spacing, tower diameter etc. and minimization of total annual cost is considered as design target subjected to operational constraints like flooding, weeping entrainment, quality specifications etc. The solution space of such type of problem is very complex due to presence of various nonlinear constraints and multiple minima. Hybrid Particle swarm optimization and Ant colony optimization (PSACO) technique is applied to deal with such complexity. The particle swarm optimization applies for global optimization and ant colony approach is employed to update positions of particles to attain rapidly the feasible solution space. Ant colony optimization works as a local search, wherein, ants apply pheromone-guided mechanism to update the positions found by the particles in the earlier stage. The presented hybrid Particle swarm optimization and Ant colony optimization (PSACO) technique is simple in concept, few in parameters and easy for implementations. Furthermore, the PSACO algorithm explores the good quality solutions quickly, giving the designer more degrees of freedom in the final choice with respect to traditional methods. One case study is presented to demonstrate the effectiveness and accuracy of proposed algorithm. The PSACO approach is able to reduce the total cost of distillation column as compare to cost obtained by commercial simulator
Economic Analysis of Residual Tree Damage Following Selective Logging in a Caspian Hardwood Forest
Get PDF This study evaluated the logging damage to residual trees following logging operations by opportunity and replacement cost approaches. A total density of 5.1 trees/ha and 17.3m3/ha of wood were harvested. On average, 9.8 trees were damaged for every tree extracted including 8 trees killed or severely damaged. The results of showed that selective cutting can damage residual trees US$47369.25. The results of this study also suggest that logging practices need to be accompanied by close supervision of field personnel and post logging site inspections to be implemented properly
Measurement of the Value for the Economic Benefits from Leisure-An Application of Nested Logit Model
Get PDF Most of the employees in Taiwan now have two days off per week, increased participations in leisure and sport have raised the utilizing on the environmental resources at maple-watching sites for viewing maple trees. Therefore, a balance policy between environmental conservation and economic growth must be considered. Specifically, what will be the result of removing these maple-watching spots? Comparatively, what is to be gained when leisure activities increase? This study adopts six maple tree viewing sites and uses questionnaires to survey tourist experiences. The Nested Logit model is applied to construct a nested choice structure and estimate the value of economic benefits from leisure and sport using a Random Utility model. Finally, this study shows the economic benefits of leisure participation in these sites and proves that these values will increase by improving each maple tree viewing site’s characteristics. Additionally, various economic benefits are to be derived when the maple tree viewing sites are removed in case of requests from public policy