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.

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.

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.

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.

Mathematical Modeling and Experimental Study on Building Ceiling System Incorporating Phase Change Material (PCM) for Energy Conservation

Thermal storage plays a major role in a wide variety of industrial, commercial and residential application when there is a mismatch between the supply and demand of energy. Several promising developments are taking place in the field of thermal storage using phase change materials (PCM) in buildings. In the present paper, a detailed study of the thermal performance of a phase change material system for energy conservation in building is analyzed and discussed. An experiment consisting of two identical test houses has been constructed to study the effect of having PCM panel on the roof of the building. One house is constructed without PCM on the room in order to provide a reference case for comparison with the experimental house that includes the phase change material. The PCM is an inorganic eutectic mixture, which has melting temperature in the range of 26 - 28°C. A mathematical model has been developed in which finite volume method is used to predict the thermal behavior of the ceiling system incorporating PCMs. A comparison with the experimental results is also made.

The Operating Features of a Stoichiometric, Ammonia and Gasoline Dual Fueled Spark Ignition Engine

An overall stoichiometric mixture of air, gaseous ammonia and gasoline was metered into a single cylinder, variable compression ratio, supercharged CFR engine at varying ratios of gasoline to ammonia. The engine was operated such that the combustion was knock-free with minimal roughness for all loads ranging from idle up to a maximum load in the supercharge regime. For a given load, speed, and compression ratio there was a range of ratios of gasoline to ammonia for which knock-free, smooth firing was obtained. This range was investigated at its roughness limit and also at its knock limit. If too much ammonia was used, then the engine fired with an excessive roughness. If too much gasoline was used, then knock-free combustion could not be obtained while the maximum brake torque spark advance was maintained. Stoichiometric operation on gasoline alone was also investigated, for comparison. It was found that a significant fraction of the gasoline used in spark ignition engines could be replaced with ammonia. Operation on mostly gasoline was required near idle. However, mostly ammonia could be used at high load. Operation on ammonia alone was possible at some of the supercharged load points. Generally, the use of ammonia or ammonia with gasoline allowed knock-free operation at higher compression ratios and higher loads than could be obtained with the use of gasoline alone. The use of ammonia/gasoline allowed practical operation at a compression ratio of 12:1 whereas the limit for gasoline alone was 9:1. When running on ammonia/gasoline the engine could be operated at brake mean effective pressures that were more than 50% higher than those achieved with the use of gasoline alone. The maximum brake thermal efficiency achieved with the use of ammonia/gasoline was 32.0% at 10:1 compression ratio and BMEP = 1025 kPa. The maximum brake thermal efficiency possible for gasoline was 24.6% at 9:1 and BMEP = 570 kPa.