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There is concern that mercury (Hg) in coal combustion by-products might be emitted into the environment during processing to other products or after the disposal/landfill of these by-products. This perception may limit the opportunities to use coal combustion by-products in recycle/reuse applications and may result in additional, costly disposal regulations. In this program, CONSOL conducted a comprehensive sampling and analytical program to include ash, flue gas desulfurization (FGD) sludge, and coal combustion by-products. This work is necessary to help identify potential problems and solutions important to energy production from fossil fuels. The program objective was to evaluate the potential for mercury emissions by leaching or volatilization, to determine if mercury enters the water surrounding an active FGD disposal site and an active fly ash slurry impoundment site, and to provide data that will allow a scientific assessment of the issue. Toxicity Characteristic Leaching Procedure (TCLP) test results showed that mercury did not leach from coal, bottom ash, fly ash, spray dryer/fabric filter ash or forced oxidation gypsum (FOG) in amounts leading to concentrations greater than the detection limit of the TCLP method (1.0 ng/mL). Mercury was detected at very low concentrations in acidic leachates from all of the fixated and more than half of the unfixated FGD sludge samples, and one of the synthetic aggregate samples. Mercury was not detected in leachates from any sample when deionized water (DI water) was the leaching solution. Mercury did not leach from electrostatic precipitator (ESP) fly ash samples collected during activated carbon injection for mercury control in amounts greater than the detection limit of the TCLP method (1.0 ng/mL). Volatilization tests could not detect mercury loss from fly ash, spray dryer/fabric filter ash, unfixated FGD sludge, or forced oxidation gypsum; the mercury concentration of these samples all increased, possibly due to absorption from ambient surroundings. Mercury loss of 18-26% was detected after 3 and 6 months at 100 F and 140 F from samples of the fixated FGD sludge. Water samples were collected from existing ground water monitoring wells around an active FGD disposal site (8 wells) and an active fly ash slurry impoundment (14 wells). These were wells that the plants have installed to comply with ground water monitoring requirements of their permits. Mercury was not detected in any of the water samples collected from monitoring wells at either site. A literature review concluded that coal combustion byproducts can be disposed of in properly designed landfills that minimize the potentially negative impacts of water intrusion that carries dissolved organic matter (DOM). Dissolved organic matter and sulfate-reducing bacteria can promote the transformation of elemental or oxidized mercury into methyl mercury. The landfill should be properly designed and capped with clays or similar materials to minimize the wet-dry cycles that promote the release of methylmercury.

This paper describes the economically optimal adoption and operation of distributed energy resources (DER) by a hypothetical California microgrid (μGrid) consisting of a group of commercial buildings over an historical test year, 1999. The optimization is conducted using a customer adoption model developed at Berkeley Lab and implemented in the General Algebraic Modeling System. A μGrid is a semiautonomous grouping of electricity and heat loads interconnected with the existing utility grid (macrogrid) but able to island from it. The μGrid minimizes the cost of meeting its energy requirements (consisting of both electricity and heat loads) by optimizing the installation and operation of DER technologies while purchasing residual energy from the local combined natural gas and electricity utility. The available DER technologies are small-scale generators (<500 kW), such as reciprocating engines, microturbines, and fuel cells, with or without combined heat and power (CHP) equipment, such as water and space heating and/or absorption cooling. By introducing a tax on carbon emissions, it is shown that if the μGrid is allowed to install CHP-enabled DER technologies, its carbon emissions are mitigated more than without CHP, demonstrating the potential benefits of small-scale CHP technology for climate change mitigation. Reciprocating engines with heat recovery and/or absorption cooling tend to be attractive technologies for the mild southern California climate, but the carbon mitigation tends to be modest compared to purchasing utility electricity because of the predominance of relatively clean central station generation in California.

We made considerable progress towards completing the development of a thermogravimetric reactor with video microscopy imaging capabilities (TGA/VMI). The video micrOSCOPY components were designed, installed and are currently under testing. With the newly developed TGA/VNH apparatus we can directly observe macroscopic changes in the morphology of pyrolyzing particles and thermal ignitions of burning particles while simultaneously monitoring the weight of pyrolyzing or reacting samples. The systematic investigation on the effects of pyrolysis conditions and char macropore structure on char reactivity continued. Pyrolysis and gasification experiments were performed consecutively in our TGA reactor and the char reactivity patterns were measured for a wide range of temperatures (400--600[degrees]C). These conditions cover both the kinetic and the diffusion limited regimes. Our results show conclusively that chars produced at high pyrolysis heating rates (and, therefore, having a more open cellular macropore structure) are more reactive and ignite more easily than chars pyrolyzed at low heating rates. These results have been explained using theoretical models. We also investigated for the first time the effect of coal particle size and external mass transfer limitations on the reactivity patterns and ignition behavior of char particles combusted in air. Finally, we used our hot stage reactor to monitormore » the structural transformations occurring during pyrolysis via a video microscopy system. Pyrolysis experiments were videotaped and particle swelling and the particle ignitions were determined and analyzed using digitized images from these experiments.« less

Distributed energy resources (DER) technologies, such as gas-fired reciprocating engines and microturbines, can be economically beneficial in meeting commercial-sector energy loads. Even with a lower electric-only efficiency than traditional central stations, combined heat and power (CHP) applications can increase overall system energy efficiency. From a policy perspective, it is useful to have good estimates of penetration rates of DER under different economic and regulatory scenarios. We model the diffusion of DER in the US commercial building sector under various technical research and technology outreach scenarios. Technology market diffusion is assumed to depend on the system's economic attractiveness and the developer's knowledge about the technology. To account for regional differences in energy markets and climates, as well as the economic potential for different building types, optimal DER systems are found for several building types and regions. Technology diffusion is predicted via a baseline and a program scenario, in which more research improves DER performance. The results depict a large and diverse market where the West region and office building may play a key role in DER adoption. With the market in an early stage, technology research and outreach programs may shift building energy consumption to a more efficient alternative.

We report the design and operation of a test device suitable for studying combustion oscillations produced by commercial-scale gas turbine fuel nozzles. Unlike conventional test stands, this test combustor uses a Helmholtz acoustic geometry to replicate the acoustic response that would otherwise be observed only during complete engine testing. We suggest that successful simulation of engine oscillations requires that the flame geometry and resonant frequency of the test device should match the complete engine environment. Instrumentation for measuring both pressure and heat release variation is described. Preliminary tests suggest the importance of characterizing the oscillating behavior in terms of a nozzle reference velocity and inlet air temperature. Initial tests also demonstrate that the stabilizing effect of a pilot flame depends on the operating conditions.

Experiments in a rapid compression machine have examined the influences of variations in pressure, temperature, and equivalence ratio on the autoignition of n-pentane. Equivalence ratios included values from 0.5 to � 2.0, compressed gas initial temperatures were varied between 675K and 980K, and compresed gas initial pressures varied from 8 to 20 bar. Numerical simulations of the same experiments were carried out using a detailed chemical kinetic reaction mechanism. The results are interpreted in terms of a low temperature oxidation mechanism involving addition of molecular oxygen to alkyl and hydroperoxyalkyl radicals. Idealized calculations are reported which identify the major reaction paths at each temperature. Results indicate that in most cases, the reactive gases experience a two-stage autoigni tion. The first stage follows a low temperature alkylperoxy radical isomerization pathway that is effectively quenched when the temperature reaches a level where dissociation reactions of alkylperoxy and hydroperoxyalkylperoxy radicals are more rapid than the reverse addition steps. The second stage is controlled by the onset of dissociation of hydrogen peroxide. Results also show that in some cases, the first stage ignition takes place during the compression stroke in the rapid compression machine, making the interpretation of the experiments somewhat more complex than generally assumed. At the highest compression temperatures achieved, little or no first stage ignition is observed.

Energy planning represents an investment-decision problem. Investors commonly evaluate such problems using portfolio theory to manage risk and maximize portfolio performance under a variety of unpredictable economic outcomes. Energy planners need to similarly abandon their reliance on traditional, ''least-cost'' stand-alone technology cost estimates and instead evaluate conventional and renewable energy sources on the basis of their portfolio cost--their cost contribution relative to their risk contribution to a mix of generating assets. This report describes essential portfolio-theory ideas and discusses their application in the Western US region. The memo illustrates how electricity-generating mixes can benefit from additional shares of geothermal and other renewables. Compared to fossil-dominated mixes, efficient portfolios reduce generating cost while including greater renewables shares in the mix. This enhances energy security. Though counter-intuitive, the idea that adding more costly geothermal can actually reduce portfolio-generating cost is consistent with basic finance theory. An important implication is that in dynamic and uncertain environments, the relative value of generating technologies must be determined not by evaluating alternative resources, but by evaluating alternative resource portfolios. The optimal results for the Western US Region indicate that compared to the EIA target mixes, there exist generating mixes with larger geothermal shares at equal-or-lower expectedmore » cost and risk.« less