James M. Ekmann

Reduction of nitrogen oxides from post-combustion gases utilizing molecular radical species

Abstract Plasma induced radicals from ammonia, methane and hydrogen have been injected into NO laden post-combustion gases to reduce pollutant concentrations. Results of chemical kinetics modelling indicate that radicals from ammonia, which are formed by interaction with an argon plasma stream, introduced into the post-combustion gases, will provide nearly complete NO removal. Laboratory investigations have shown that molecular radical reduction is capable of providing up to 94 mol% NO reduction. Streams of ammonia or combined ammonia/methane, which provide this reduction, utilize a minimum input energy and yield no substantial ammonia discharge.

Coal Storage and Transportation

Coal preparation, storage, and transportation are essential to coal use. Preparation plants, located near to the mine, remove some inorganic minerals associated with raw coal. Coal is transported from the mines to the point of consumption, often an electric generating plant, by rail, barge and trucks. Railroads are the predominant form of coal transportation within a country. Global coal trade, movement by large ocean-going vessels, continues to increase. At the end use site, the coal is crushed, ground, and the moisture content reduced to the proper specifications for end use. Coal is stored at various points in the supply chain. Processed coal will weather and oxidize, changing its properties; it can self-ignite, unless precautions are taken. Technology in use today is similar to that used in previous decades. Performance improvements have come from improved software and instruments that deliver real-time data. These improve management of sub-processes in the coal supply chain and reduce costs along the supply chain.

High-energy Nd:YAG laser ignition of coals

One of the main purposes of the present study is to explore the use of laser radiation to initiate and support combustion of coals. Within this context, some experiments were conducted to study the interaction of the Nd-Yag laser radiation with four different coals. Laser intensities ranging from 0.5 X 103 to 1.5 X 104 W/cm2 at 1.064 micrometers wavelength and the pulse duration of 5 ms were used. For laser intensities less than 800 W/cm2, no ignition was observed for all coals. For laser intensities above this value, two ignition mechanisms were observed: the surface ignition followed by the gas phase ignition when Wyoming subbituminous, Indian lignite and North Dakota lignite coals were used. For the same range of the laser intensities, however, only the gas phase ignition was observed when Pittsburgh bituminous coal was used. It was also noted that a significant amount of the external laser radiations were absorbed by the pyrolysis products during the early stages of the ignition period.

FLOW STUDIES OF HIGHLY-LOADED-COAL-WATER MIXTURES AS A FUNCTION OF THE PARTICLE SIZE DISTRIBUTION

ABSTRACT Mixtures of pulverized coal in water (CWMs) are being studied as a retrofit fuel for boilers, process heaters, gas turbines and stationary diesel engines. Each application may possess design characteristics which restrict the maximum particle size of the CWM. PETC has been involved in a research program to examine the flow characteristics of highly-loaded CWMs in both a flow loop and in bench-scale laboratory experiments as a function of the particle size distribution. Extensive flow tests have been conducted on CWMs in 0.025-meter and 0.051-meter schedule 40 pipes. The facility includes appropriately sized pumps, horizontal and vertical test sections and flow, pressure and temperature measuring equipment. Nominal velocities range from 0.31 meters per second (mps) to 6 mps for each line size. In addition, extensive laboratory measurements of viscometric properties of CWMs have been made. The range of particle sizes examined either in the loop or the laboratory includes from 100% below 30μ to ...

Effects of coal-water mixture properties in atomization

Recent suggested CWM applications include using filter cake material and mill tailings as coal sources. Neither coal type nor particle size distribution are necessarily well suited for coal-water mixture production. Slurries were prepared with and without additives and attempts were made to characterize their rheological properties and atomize these materials. Limits of operation and the value of existing rheological instrumentation and methods were investigated. Effects of changes in particle size distribution are discussed.

Characterization of coal—oil mixtures by a pseudo diffusivity parameter

Abstract For the use of coal—oil mixtures as combustion fuels stable maintenance of the solid—liquid suspension is vital and for this reason the settling properties of these mixtures were studied with a system of ultrasonic sensors. The sedimentation theory of Smiles, which relies on unsteady state diffusion analogies, was applied successfully to the coal-oil mixtures and pseudo diffusion coefficients were determined.