The effect of oxy-fuel combustion with simulated flue gas recycle on NOx formation and flame stability in a 20 kW coal and coal/biomass combustor [abstract]

Only abstract of poster available.Track I: Power GenerationThe adoption of renewable energy standards aimed at reducing carbon dioxide emissions and the expansion of carbon cap and trade systems are expected to have great impact on regions that are dependent upon coal for electricity generation. A retrofit technology for existing coal-fired power plants is needed in order to meet these standards and reduce CO2 emissions while limiting the costs to be passed on to electricity consumers. It is anticipated that bioenergy resources in the form of agricultural waste or bioenergy crops grown specifically for energy production (e.g. switchgrass) could constitute the majority of the renewable energy portfolio in regions that do not have ample wind and solar resources. The cofiring of renewable biomass with coal is an attractive option for reducing the carbon footprint of a power generation plant that does not require a significant change in the power plant design. Another approach to reduce greenhouse gas emissions is to implement Carbon dioxide Capture and Storage (CCS) technology, thereby preventing the release of CO2 into the atmosphere. The combination of cofiring of coal and biomass with CCS is potentially a carbon negative technology, providing energy while removing CO2 from the atmosphere. The carbon dioxide in the flue gas can be highly concentrated by replacing combustion air with a mixture of oxygen and recycled flue gas (oxy-coal combustion) thus removing the need for CO2 scrubbing. While there are costs associated with oxygen production, advances in air-separation technologies are being made—particularly in the area of ion-membrane separation technologies. Moreover, oxy-coal combustion has the potential to reduce the formation of nitrogen oxides (NOx) beyond the levels achievable by low NOx burners and overfire air, thereby offsetting some of the costs associated with oxygen production by reducing or eliminating the need for post combustion NOx cleanup. The overall objective of this work is to investigate the cofiring of biomass with coal under oxy-combustion conditions, as a means of mitigating atmospheric carbon dioxide emissions while yielding burning characteristics that are similar or superior to traditional coal combustion. Experiments are performed in a 15-35 kWth, horizontally-fired laboratory combustor. The gas compositions (concentrations of O2, N2 and CO2) of the primary and secondary flows are varied over a wide range of conditions and the effects of the cofiring ratio (sawdust feed rate/total fuel feed rate) and gas composition on flame stability and NOx formation are investigated. Flame stability is determined by reducing the secondary oxidizer swirl velocity until the flame is visibly detached from the fuel jet. Effects on NOx formation are determined by measuring NO in the flue gas via a ThermoFisher scientific CEM following complete char burnout

Boosting the Electrochemical Performance of Li₁.₂Mn₀.₅₄Ni₀.₁₃Co₀.₁₃O₂ by Atomic Layer-Deposited CeO₂ Coating

It has been demonstrated that atomic layer deposition (ALD) provides an initially safeguarding, uniform ultrathin film of controllable thickness for lithium-ion battery electrodes. In this work, CeO2 thin films were deposited to modify the surface of lithium-rich Li1.2Mn0.54Ni0.13Co0.13O2 (LRNMC) particles via ALD. The film thicknesses were measured by transmission electron microscopy. For electrochemical performance, ∼2.5 nm CeO2 film, deposited by 50 ALD cycles (50Ce), was found to have the optimal thickness. At a 1 C rate and 55°C in a voltage range of 2.0-4.8 V, an initial capacity of 199 mAh/g was achieved, which was 8% higher than that of the uncoated (UC) LRNMC particles. Also, 60.2% of the initial capacity was retained after 400 cycles of charge-discharge, compared to 22% capacity retention of UC after only 180 cycles of charge-discharge. A robust kinetic of electrochemical reaction was found on the CeO2-coated samples at 55°C through electrochemical impedance spectroscopy. The conductivity of 50Ce was observed to be around 3 times higher than that of UC at 60-140°C. The function of the CeO2 thin-film coating was interpreted as being to increase substrate conductivity and to block the dissolution of metal ions during the charge-discharge process

Flame Design: A Novel Approach Developed to Produce Clean, Efficient Diffusion Flames

Soot formation and flame extinction are vital concerns in the combustion of fossil fuels. In particular, soot is responsible for pollutant emissions, and extinction can cause inefficient or unstable burning. Normal-gravity experiments have demonstrated that flames can be designed to improve both characteristics by redirecting some or all of the nitrogen from the oxidizer into the fuel. Such nitrogen exchange can produce permanently blue flames, which are soot free under all possible flame conditions. Furthermore, this approach can lead to stronger, extinction-resistant flames. Past investigations of nitrogen exchange were unable to identify the physical mechanisms responsible for its benefits because these mechanisms cannot be isolated when normal-gravity flames are studied. In contrast, the Diffusion Flame Extinction and Soot Inception (DESI) experiment considers spherical flames, where nearly perfect spherical symmetry affords new levels of control. Because of buoyancy, spherical flames cannot be created in Earth s gravity. DESI was conceived by principal investigator Professor R.L. Axelbaum of Washington University in St. Louis. Tests to date have utilized the 2.2-Second Drop Tower at the NASA Glenn Research Center at Lewis Field. The experiment is slated for testing aboard the International Space Station in a few years. Two mechanisms have been proposed to explain the connection between nitrogen exchange and permanently blue flames. These are the structure (chemical effects) and hydrodynamics (flow direction and speed). In normal-gravity flames, the structure and hydrodynamics are coupled, since nitrogen exchange simultaneously modifies both. Spherical microgravity flames, on the other hand, allow independent control of these factors. Specifically, structure can be modified via nitrogen exchange, and flow direction can be reversed by swapping the ambient and burner-feed gases. In DESI, these variations can be accomplished without changing the theoretical flame temperature

NANO HIGHLIGHT Synthesis and Classification of Monodisperse Magnetic Nanoparticles

Magnetic nanoparticles/nano-composites (ferromagnetic, ferrimagnetic and antiferromagnetic materials) have many promising industrial and biomedical applications such as catalysis, magnetocooling, optical and recording devices, purification of enzymes and other biological materials, and water purification devices. Most of the conventional methods for the synthesis of magnetic nanoparticles are rather complex, usually involving several steps; efforts have been made to establish direct preparation routes of these magnetic particles. In this project, γ-phase iron oxide nanoparticles were synthesized using a flame aerosol reactor. The effects of flame temperature profile and sampling conditions have been investigated on the morphology and magnetic properties of synthesized maghemite nanoparticles. The particle size and magnetic properties of the powders can be controlled by varying the flame temperature and sampling conditions. Figure 1 shows the EM images of synthesized γ-phase iron oxide naoparticles under different flame conditions. To obtain mono-sized magnetic nanoparticles for a variety of industrial and medical applications, a high-throughput monodisperse particle classification system capable of tailoring synthesized nanoparticles into tighter size distributions has been designed and fabricated. The system consists of a highthroughput, high-charging-efficiency nanoparticle charger [1] and a high throughput nanometer differential mobility analyzer [2]. The system performance had been evaluated prior to its integration with the flame synthesis system. Besides the development of the classification system, the effort has been also on the development of a multi-stage differential mobility analyzer column [3]. This new DMA column allows the multiple extractions of mono-sized nanoparticles simultaneously. The new column expects to facilitate the classification and testing processes while reducing the waste of synthesized magnetic nanoparticles

Effects of Structure and Hydrodynamics on the Sooting Behavior of Spherical Microgravity Diffusion Flames

We have examined the sooting behavior of spherical microgravity diffusion flames burning ethylene at atmospheric pressure in the NASA Glenn 2.2-second drop tower. In a novel application of microgravity, spherical flames allowed convection across the flame to be either from fuel to oxidizer or from oxidizer to fuel. Thus, microgravity flames are uniquely capable of allowing independent variation of convection direction across the flame and stoichiometric mixture fraction, Z(sub st). This allowed us to determine the dominant mechanism responsible for the phenomenon of permanently-blue diffusion flames -- flames that remain blue as strain rate approaches zero. Stoichiometric mixture fraction was varied by changing inert concentrations such that adiabatic flame temperature did not change. At low and high Z(sub st) nitrogen was supplied with the oxidizer and the fuel, respectively. For the present flames, structure (Z(sub st)) was found to have a profound effect on soot production. Soot-free conditions were observed at high Z(sub st) (Z(sub st) = 0.78) and sooting conditions were observed at low Z(sub st) (Z(sub st) = 0.064) regardless of the direction of convection. Convection direction was found to have a lesser impact on soot inception, with formation being suppressed when convection at the flame sheet was directed towards the oxidizer

The 8th International Symposium on Coal Combustion (ISCC-8)

No abstract availabl