160 research outputs found
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Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, October 1, 1996--December 31, 1996
The key issues addressed this quarter were related to operational problems in the coal feed system, namely, the inability to accurately measure all of air entering the system, and plugging of coal in the feed lines due to poor entrainment. Both of these problems caused unacceptable uncertainty and/or fluctuations in the operating conditions and therefore required solutions. The coal entrainment problem was solved by installing a new educator designed for entraining solids in gas streams. All of the air entering the reactor now flows through the educator, either as motive air or through the suction air inlet. This ensures that the coal is entrained at relatively high velocity, so that it will flow to the reactor without forming slugs in the lines. A new feeder shroud was also installed with an air jet directed towards the auger to sweep off the tip in order to reduce pulsations when feeding coal. The problems associated with accurately metering the air have been somewhat more difficult to resolve. New strategies for completely closing the system have been tested and look promising. A new flowmeter was also purchased with cost sharing funds to directly measure the air flow rate of the two phase stream (after the coal injection point). If the system can be operated without leaks, then the changes will provide two independent measurements of the air flow to ensure accuracy. If the system cannot be sealed, the new flowmeter will still provide reliable measurement of the air flow and permit proper operation of the combustor. Consequently, we feel that the problems have been resolved and we look forward to a productive next quarter
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Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, April 1, 1997--June 30, 1997
This report describes work performed in the fifteenth quarter of a fundamental study to examine the effect of staged combustion on ash formation and deposition. Efforts this quarter included addition of a new cyclone for improved particle sampling and modification of the existing sampling probe. Particulate samples were collected under a variety of experimental conditions for both coals under investigation. Deposits formed from the Black Thunder coal were also collected. Particle size and composition from the Pittsburgh No. 8 ash samples support previously reported results. In addition, the authors ability to distinguish char/ash associations has been refined and applied to a variety of ash samples from this coal. The results show a clear difference between the behavior of included and excluded pyrite, and provide insight into the extent of pyrite oxidation. Ash samples from the Black Thunder coal have also been collected and analyzed. Results indicate a significant difference in the particle size of {open_quotes}unclassifiable{close_quotes} particles for ash formed during staged combustion. A difference in composition also appears to be present and is currently under investigation. Finally, deposits were collected under staged conditions for the Black Thunder coal. Specifically, two deposits were formed under similar conditions and allowed to mature under either reducing or oxidizing conditions in natural gas. Differences between the samples due to curing were noted. In addition, both deposits showed skeletal ash structures which resulted from in-situ burnout of the char after deposition
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Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, October 1, 1996--December 31, 1996
The key issues addressed this quarter were related to operational problems in the coal feed system, namely, the inability to accurately measure all of air entering the system, and plugging of coal in the feed lines due to poor entrainment. Both of these problems caused unacceptable uncertainty and/or fluctuations in the operating conditions and therefore required solutions. The coal entrainment problem was solved by installing a new educator designed for entraining solids in gas streams. All of the air entering the reactor now flows through the educator, either as motive air or through the suction air inlet. This ensures that the coal is entrained at relatively high velocity, so that it will flow to the reactor without forming slugs in the lines. A new feeder shroud was also installed with an air jet directed towards the auger to sweep off the tip in order to reduce pulsations when feeding coal. The problems associated with accurately metering the air have been somewhat more difficult to resolve. New strategies for completely closing the system have been tested and look promising. A new flowmeter was also purchased with cost sharing funds to directly measure the air flow rate of the two phase stream (after the coal injection point). If the system can be operated without leaks, then the changes will provide two independent measurements of the air flow to ensure accuracy. If the system cannot be sealed, the new flowmeter will still provide reliable measurement of the air flow and permit proper operation of the combustor. Consequently, we feel that the problems have been resolved and we look forward to a productive next quarter
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Investigation of mineral transformation and ash deposition during staged combustion. Final report, October 1, 1993--September 30, 1997
The purpose of this report is to document a recently completed four-year study to examine the impact of low-NOx firing technologies on ash formation and deposition while firing pulverized coal. Low-NOx burners and staged combustion inhibit NOx formation by restricting the amount of oxygen available to form a fuel-rich zone in which nitrogen compounds are reduced to molecular nitrogen (N{sub 2}) rather than oxidized. Additional oxygen is provided downstream for complete combustion. Consequently, coal and mineral particles encounter different temperatures and oxygen concentrations when they are burned under low-NOx firing conditions than they do in conventionally-fired units. Two coals with distinctly different inorganic contents and ash characteristics were fired in a pilot-scale laboratory combustor under both conventional and staged combustion conditions. Ash and deposit samples were collected at various locations in the reactor and analyzed in order to assess the influence of staged combustion. This report is organized as follows. First, a background section provides the foundation needed in order to understand the motivation for and the results of the experimental program. The next section presents a description of the experimental apparatus and procedures, including the development the analytical methods critical to the study. Results of the analyses of coal, ash and deposit samples are then presented and discussed for each of the two coals. Finally, the report ends with a short summary and statement of conclusions
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Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, April 1, 1996--June 30, 1996
This report describes work completed during the eleventh quarter of a DOE-funded study of mineral transformations and ash deposition during staged combustion. Accomplishments included repairs and improvements to the laboratory combustor, collection of deposits and observation of deposition behavior as a function of operating conditions, and analysis of deposit samples collected under both staged and conventional conditions. The water cooling shell for the brass burner was rebuilt this quarter. It was necessary to rebuild the cooling shell because of frequently occurring leaks which could no longer be repaired. No new leaks have occurred since the repairs were made. Deposits were collected for several stoichiometries between SR=0.65 and SR=0.75. A changeover from carbon-rich deposits to deposits which contained little carbon was observed at about SR=0.73 for the coal and natural gas feed rates used the experiments. However, even deposits which contained relatively little carbon had a carbon- enriched layer at the tube surface. This layer was due to carbon which did not burn out completely after impaction. A similar type of carbon layer may affect deposit formation in utility boilers. One of the key contributions this quarter was the analysis of deposit samples collected under both staged and conventional conditions. These initial results indicate that deposits formed during staged combustion of a Pittsburgh No. 8 are similar to those formed during conventional combustion. Some small differences were observed and it is not yet known how significant these differences may be. However, substantial differences between the deposits and ash samples were observed. These differences were apparent in both the bulk compositions and ``species`` distributions. Continuing work will focus on clarifying and quantifying the effect of staged combustion on deposit formation and strength development
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Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, January 1, 1995--March 31, 1995
Progress during the sixth quarter of a three-year study was made in two task areas: (1) parametric testing of the target coals, and (2) analysis of samples from the combustion tests. A new microanalysis system was acquired (no cost to DOE) and is now functional, although development of analysis routines for the system is still in progress. This system has significantly increased our analytical throughput and has provided increased reliability. Parametric testing of the Pittsburgh No. 8 coal (weathered) was initiated this quarter. Initial analytical results from these tests show sulfur release and iron transformations as a function of test conditions and sampling location. A new supply of Pittsburgh No. 8 coal has been shipped and will be used to contrast behavior between the oxidized (weathered) and unoxidized Pittsburgh fuels. Finally, specific tasks for the next quarter have been identified and reported
Predictors of common femoral artery access site complications in patients on oral anticoagulants and undergoing a coronary procedure
Evolution and patterns of global health financing 1995-2014 : development assistance for health, and government, prepaid private, and out-of-pocket health spending in 184 countries
Background An adequate amount of prepaid resources for health is important to ensure access to health services and for the pursuit of universal health coverage. Previous studies on global health financing have described the relationship between economic development and health financing. In this study, we further explore global health financing trends and examine how the sources of funds used, types of services purchased, and development assistance for health disbursed change with economic development. We also identify countries that deviate from the trends. Methods We estimated national health spending by type of care and by source, including development assistance for health, based on a diverse set of data including programme reports, budget data, national estimates, and 964 National Health Accounts. These data represent health spending for 184 countries from 1995 through 2014. We converted these data into a common inflation-adjusted and purchasing power-adjusted currency, and used non-linear regression methods to model the relationship between health financing, time, and economic development. Findings Between 1995 and 2014, economic development was positively associated with total health spending and a shift away from a reliance on development assistance and out-of-pocket (OOP) towards government spending. The largest absolute increase in spending was in high-income countries, which increased to purchasing power-adjusted 914 and 51 to 37.6 billion in 2016. Nonetheless, there is a great deal of variation revolving around these averages. 29 countries spend at least 50% more than expected per capita, based on their level of economic development alone, whereas 11 countries spend less than 50% their expected amount. Interpretation Health spending remains disparate, with low-income and lower-middle-income countries increasing spending in absolute terms the least, and relying heavily on OOP spending and development assistance. Moreover, tremendous variation shows that neither time nor economic development guarantee adequate prepaid health resources, which are vital for the pursuit of universal health coverage.Peer reviewe
Future and potential spending on health 2015-40: Development assistance for health, and government, prepaid private, and out-of-pocket health spending in 184 countries
Background: The amount of resources, particularly prepaid resources, available for health can affect access to health care and health outcomes. Although health spending tends to increase with economic development, tremendous variation exists among health financing systems. Estimates of future spending can be beneficial for policy makers and planners, and can identify financing gaps. In this study, we estimate future gross domestic product (GDP), all-sector government spending, and health spending disaggregated by source, and we compare expected future spending to potential future spending. Methods: We extracted GDP, government spending in 184 countries from 1980-2015, and health spend data from 1995-2014. We used a series of ensemble models to estimate future GDP, all-sector government spending, development assistance for health, and government, out-of-pocket, and prepaid private health spending through 2040. We used frontier analyses to identify patterns exhibited by the countries that dedicate the most funding to health, and used these frontiers to estimate potential health spending for each low-income or middle-income country. All estimates are inflation and purchasing power adjusted. Findings: We estimated that global spending on health will increase from US24.24 trillion (uncertainty interval [UI] 20.47-29.72) in 2040. We expect per capita health spending to increase fastest in upper-middle-income countries, at 5.3% (UI 4.1-6.8) per year. This growth is driven by continued growth in GDP, government spending, and government health spending. Lower-middle income countries are expected to grow at 4.2% (3.8-4.9). High-income countries are expected to grow at 2.1% (UI 1.8-2.4) and low-income countries are expected to grow at 1.8% (1.0-2.8). Despite this growth, health spending per capita in low-income countries is expected to remain low, at 195 (157-258) per capita in 2040. Increases in national health spending to reach the level of the countries who spend the most on health, relative to their level of economic development, would mean $321 (157-258) per capita was available for health in 2040 in low-income countries. Interpretation: Health spending is associated with economic development but past trends and relationships suggest that spending will remain variable, and low in some low-resource settings. Policy change could lead to increased health spending, although for the poorest countries external support might remain essential
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