The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

Oxy-fuel combustion of pulverized coal: Characterization, fundamentals, stabilization and CFD modeling

Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.

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An overview of advances in biomass gasification

Turbulent premixed combustion: Flamelet structure and its effect on turbulent burning velocities

This paper examines the fundamental and industrial application aspects of combustion of natural gas, heavy and light fuel oils, and coal in highly preheated air. The experiments have been carried out in an experimental furnace at 0.58 MW thermal input based on fuel, and the combustion air has been preheated to 1300 °C. The fuel injectors are positioned outside of the combustion air stream. Detailed in-furnace measurements of temperature, chemistry (O 2 , CO, NO x , and particulates), and heat transfer have been performed. Combustion of natural gas and light oil takes place without a visible presence of flame. Although the furnace was operated with an overall excess air of 10%, the combustion process occurs in strongly sub-stoichiometric conditions due to entrainment of large amounts of recirculated flue gases into the fuel jets before ignition. The experiments demonstrated an effective technology for efficient and environmentally friendly combustion of a wide range of fuels. The technology discussed in the main text offers the potential of high furnace efficiencies, uniform heat flux distribution, and dramatic reductions in CO 2 , CO, and NO emissions. Therefore, this technology should be considered for future design of industrial furnaces.

On the (MILD) combustion of gaseous, liquid, and solid fuels in high temperature preheated air

This paper deals with the new technology of burning fuels with high-temperature air and large quantities of flue gas. Furnace experiments at 0.58 MW fuel input and combustion air preheat of 1300°C were undertaken to examine the process. Comprehensive in-furnace measurements of velocities, temperature, gas composition (O2, CO2, CO, H2, CH4), and radiation were carried out. The furnace was operated under conditions resembling a well-stirred reactor, and almost all furnace volume was filled with combustion products containing 2%–3% oxygen. Both the natural gas streams and the combustion airstream entrained large quantities of hot combustion products before their mix. The whole furnace was “glowing”, and no visible flame was observed. The experiments were simulated using a computational fluid dynamics-based mathematical model. Three main conclusions were drawn: (1) the combustion process was much slower if compared with conventional burner technology, and hydrocarbons, hydrogen, and carbon monoxide were measured far downstream into the furnace, (2) high and uniform radiative heat fluxes were observed, and (3) novel simplified chemistry models applicable to this new combustion conditions are required.

Combustion of natural gas with high-temperature air and large quantities of flue gas

Mathematical modeling of MILD combustion of pulverized coal

Investigation of ash deposit formation during co-firing of coal with sewage sludge, saw-dust and refuse derived fuel

This paper deals with the technology of burning natural gas with combustion air preheated to 1300°C. The objective of this work is to assess the potential of several combustion models and NOx postprocessors for their abilities to predict NOx emissions. The steady-state computational results have been compared both with in-furnace measurements and with the measured furnace exit parameters. The following main conclusions have been drawn: (1) with the exception of the small region located within the natural gas jet, the computations resulted in good quality predictions: (2) the NOx has been formed in a thin elongated region (flamelet) located between the natural gas jet and the air jet: (3) the NO has been formed mainly by the thermal path, and the NO-reburning mechanism was of little importance: and (4) there are strong indications that the non-stationary behavior of the weak (fuel) jet must be accounted for if the predictions within the fuel jet were to be perfected.

Roman Weber

Papers

On the (MILD) combustion of gaseous, liquid, and solid fuels in high temperature preheated air

Combustion of natural gas with high-temperature air and large quantities of flue gas

Mathematical modeling of MILD combustion of pulverized coal

Investigation of ash deposit formation during co-firing of coal with sewage sludge, saw-dust and refuse derived fuel

Predicting NOx emissions of a burner operated in flameless oxidation mode