Simulation of Pulverized Coal Injection in a Blast Furnace

A three-dimensional multiphase CFD model using an Eulerian approach is developed to simulate the process of pulverized coal injection into a blast furnace. The model provides the detailed fields of fluid flow velocity, temperatures, and compositions, as well as coal mass distributions during the devolatilization and combustion of the coal. This paper focuses on coal devolatilization and combustion in the space before entering the raceway of the blast furnace. Parametric studies have been conducted to investigate the effect of coal properties and injection operations.

Preliminary Study on Combustion of Biodiesel for Power Generation

In the recent wake of escalating crude oil prices due to depletion of fossil fuel, biodiesel has generated a significant interest as an alternative fuel for the future. The use of biodiesel to fuel microturbines or gas turbine application is envisaged to solve problems of diminishing supplies of fossil fuel reserves and environmental concerns. This paper examines the combustion of biodiesel derived from Malaysian Waste Cooking Oil (WCO) in a combustion test facility to study the feasibility of using the designated fuel at five various volumetric ratios for gas turbine application. Biodiesel was produced from waste cooking oil in Malaysia, mainly from palm oil sources and animal fats. The oil burner was able to fire the five blends of fuel without any modification or pretreatment. The combustion performance of Malaysian WCO biodiesel and distillate blends was examined with respect to the combustion efficiency. The results indicated biodiesel combustion required less air for stoichiometric combustion due to presence of oxygen in the fuel. Indeed biodiesel stand as a potential alternative fuel for power generation application with the best efficiency at blended ratio of 20% biodiesel and 80% distillate.

Hg Emission Modeling for a Blended Coal Particle

The largest source of human-caused mercury air emissions in the U.S principle is from combustion coal, a dominant fuel used for power generation. The coal chlorine content and ash composition, gas temperature, residence time and presence of different gases will decide the speciation of Hg into Hg° (elemental form) and HgCl2 (oxidized form). The extent of oxidation depends on the concentration of chlorine in flue gases. In order to predict the % of oxidized Hg, a transient model for combustion of a coal particle is formulated including Hg reactions. The model assumes that mercury and chlorine are released as a part of volatiles in the form of elemental mercury and HCl. A three step reaction is implemented for the oxidation of mercury. The model investigates the effect of coal blend with feedlot biomass (FB or Cattle manure), ambient temperature, and particle size on the extent of mercury oxidization. Mercury oxidation (HgCl2) increased with increase in diameter of particle and FB % in blended fuel.

Prediction of Mercury Speciation in Coal-Combustion Systems

This study is a part of a comprehensive investigation, to conduct bench-, pilot-, and full-scale experiments and theoretical studies to elucidate the fundamental mechanisms associated with mercury oxidation and capture in coal-fired power plants. The objective was to quantitatively describe the mechanisms governing adsorption, desorption, and oxidation of mercury in coal-fired flue gas carbon, and establish reaction-rate constants based on experimental data. A chemical-kinetic model was developed which consists of homogeneous mercury oxidation reactions as well as heterogeneous mercury adsorption reactions on carbon surfaces. The homogeneous mercury oxidation mechanism has eight reactions for mercury oxidation. The homogeneous mercury oxidation mechanism quantitatively predicts the extent of mercury oxidation for some of datasets obtained from synthetic flue gases. However, the homogeneous mechanism alone consistently under predicts the extent of mercury oxidation in full scale and pilot scale units containing actual flue gas. Heterogeneous reaction mechanisms describe how unburned carbon or activated carbon can effectively remove mercury by adsorbing hydrochloric acid (HCI) to form chlorinated carbon sites, releasing the hydrogen. The elemental mercury may react with chlorinated carbon sites to form sorbed HgCl. Thus mercury is removed from the gas-phase and stays adsorbed on the carbon surface. Predictions using this model have very good agreement with experimental results.

Thermodynamic Equillibrium Model of Emission Levels of Small Gas Turbine Engine Using Kerosene Ethanol Blends

The increasing awareness towards environment protection and peak load response is accredited in the development of gas turbine system. Many such system preliminary utilizes liquid fuels like kerosene. The emission level with such liquid fuel may be reduced by addition of oxygenated fuel like ethanol. Hence, the basic objective of present paper is to investigate analytically the influence of ethanol addition on emission levels of the kerosene fired small laboratory gas turbine unit. This paper discusses about the theoretical investigation on emission levels with kerosene-ethanol blended fuel using thermodynamic equilibrium model. The theoretical investigations have been carried out on Gilkes GT 85/2 twin shaft Gas Turbine Engine with ethanol blended kerosene fuel to a concentration level of 25% ethanol in the step of 5% increment. The investigations of the emission levels were carried out for CO2, CO, O2, H2, N2, H2O, OH and NO with respect to equilibrium temperature at different overall equivalence ratios ranging from 0.1 to 1.1. It is worth to mention that the equilibrium thermodynamic model clearly indicates that in narrow operative range of equivalence ratio (0.1 to 0.2) and the ethanol addition to an extent of 10% to 15% clearly offers reduced emission levels.

Structure of Propylene Turbulent Diffusion Flames in Cross-Flow Near Smoke Point

An experimental study of a propylene diffusion flame at its smoke point in a cross-flow with velocities ranging from 2 to 4 m/s and a series of diluted conditions was conducted. A gas jet flame from a circular tube burner (ID = 3.2 mm) with a range of exit velocities (4.2 to 34 m/s) corresponding to a Reynolds number range of 520 to 6065 was studied. Nitrogen was added to the fuel stream to eliminate smoking when the fuel flow rate was lower than the flow rate of pure fuel at smoke point condition (which is defined as the Critical Fuel Mass Flow Rate, CFMFR). The curve of N2 flow rate with fuel flow rate at the smoke point showed a skewed bell shape with two distinct regions. In the first region, the diluent flow rate increased with the fuel flow rate, and in the subsequent region the trend was reversed. These two regions were separated by a transition region. Our previous studies on flames in quiescent conditions concluded that these two regions were controlled by jet momentum and chemical kinetics, respectively. This study presents flame structure details such as transverse temperature and concentration profiles in typical flames representing these two regimes. Most of the temperature profiles show a dual peak structure, where the peak nearer to the burner was higher than the other. Furthermore, the peaks in the transition region flame were more distinct than those in the momentum dominated flame. Most of the flames in the 2 m/s cross-flow had lower O2 concentrations than the flames in the 3 and 4 m/s cross-flow. The temperature profiles, and the concentration profiles of O2 and soot change significantly when cross-flow velocity was changed from 2 to 4 m/s. Findings from this study enable us to understand industrial flares that are commonly used in petroleum refineries and chemical plants.

A Practical Solid-Propellant Micro-Thruster

Miniaturization of solid-propellant thrusters is an area of active research that has been motivated by the reduction in size of aerospace systems and the advancement of micromachining techniques. Though this micro-propulsion problem seems simplistic compared to the macro-scale counterpart, an efficient and reliable device has yet to be produced. A millimeter-scale novel composite solid-propellant thruster design that builds on pervious work [1] and increases efficiency is here presented. Current designs made primarily out of silicon suffer from high thermal losses and, in extreme cases, flame quenching due to the augmented surface area to volume ratio associated with miniaturization. Moreover, the reduced device dimensions drive the combustion reaction to complete outside of the thruster, misemploying the majority of the chemical energy. This occurs because the propellant mixing and chemical time do not scale with size, while the residence time does decrease as the size of the thruster decreases [2]. A novel thruster design that increases the propellant residence time is being characterized using ammonium perchlorate/binder composite propellant. The thruster geometry recycles thermal energy to the unburned propellant grain increasing its temperature and, therefore, burning rate and combustion efficiency. In addition, propellant formulation has been optimized for the thruster minimization.

Prediction of Raceways in a Blast Furnace

In a blast furnace, preheated air and fuel (gas, oil or pulverized coal) are often injected into the lower part of the furnace through tuyeres, forming a raceway in which the injected fuel and some of the coke descending from the top of the furnace are combusted and gasified. The shape and size of the raceway greatly affect the combustion of, the coke and the injected fuel in the blast furnace. In this paper, a three-dimensional (3-D) computational fluid dynamics (CFD) model is developed to investigate the raceway evolution. The furnace geometry and operating conditions are based on the Mittal Steel IH7 blast furnace. The effects of Tuyere-velocity, coke particle size and burden properties are computed. It is found that the raceway depth increases with an increase in the tuyere velocity and a decrease in the coke particle size in the active coke zone. The CFD results are validated using experimental correlations and actual observations. The computational results provide useful insight into the raceway formation and the factors that influence its size and shape.

Fretting Wear Between Supporting Grids and Cladding Tubes of Nuclear Fuel Rod

The experimental investigation was performed to find the associated changes in characteristics of fretting wear with various water temperatures. Fretting can be defined as the oscillatory motion with very small amplitudes, which usually occur between two contacting surfaces. The fretting wear, which occurs between cladding tubes of nuclear fuel rod and grids, causes in damages the cladding tubes by flow induced vibration in a nuclear reactor. In this paper, the fretting wear tests were carried out using the zirconium alloy tubes and the grids with increasing the water temperature. The tube materials in water of 20°C, 50°C and 80°C were tested with the applied loads from 5N up to 25N and the relative amplitude of 200μm. The worn surfaces were observed by SEM, EDX analysis and 2D surface profiler. As the water temperature increased, the wear volume was decreased, but oxide layer was increased on the worn surface. The abrasive wear mechanism was observed at water temperature of 20°C and adhesive wear mechanism occurred at water temperature of 50°C, 80°C. As the water temperature increased, surface micro-hardness was decreased, but wear depth and wear width were decreased due to increasing stick phenomenon. Stick regime occurred due to the formation of oxide layer on the worn surface with increasing water temperatures.

A Dynamic Model for a Closed-Loop Continuous Energy System Using Solar Power

One key advantage of solar power over more traditional power sources is its modular nature, allowing it to be used in remote locations or as a supplementary source of power. Recent studies show fuel cell technology as a good means of providing a continuous supply of electricity from a solar array, eliminating drawbacks caused by solar energy's cyclical nature. The high power density of such a system makes it ideal for use in areas such as unmanned aerial vehicles and space exploration. Due to the complexity and relatively high initial cost of current fuel cells, however, optimization of such a system is critical. This paper examines a dynamic model of a solar regenerative fuel cell system built in MATLAB Simulink. The system uses a polymer electrolyte membrane (PEM) fuel cell, running on stored hydrogen and oxygen, to produce power when solar energy is insufficient. It uses a PEM based electrolyzer to produce hydrogen and oxygen from water when solar energy exceeds demand. The mathematical model includes modules for each component, including solar cells, fuel cell, electrolyzer, and auxiliary systems. Models were built based on fundamental physics to the extent practical. The individual modules were first tested for their performances and then were integrated to form an integrated solar powered regenerative fuel cell system. The simulations were carried out for a day and night cycle and the results show that the closed loop system can be operated providing continuous supply of electric power.