Parameters influencing the evolution and oxidation of sulfur in suspension phase coal combustion

Journal ArticleStoker coal-fired boiler furnaces are significant in terms of coal consumption and environmental impact; however, they have received relatively little research attention. This paper describes the results of a two-year study on the formation of sulfur oxides in the suspension phase of a coal-fired spreader-stoker system. An eight foot, drop-tube furnace with upward hot-gas flow was used to define the evolution and oxidation of fuel sulfur in the suspension phase and to establish the influence of the combustion parameters on S02 formation. The results indicate that coal particles greater than approximately 0.1 inch fall to the stoker grate essentially unreacted. Thus, only between 8 and 20 percent of the coal feed actually burns in the suspension phase. In general, the evolution and oxidation of sulfur lags hydrogen but leads carbon. The behavior of the organic sulfur closely follows that of carbon; however, the decomposition of the sulfate sulfur depends primarily on the local temperature and oxygen concentration. The behavior of the sulfate sulfur is of major importance because of the high sulfate content of the natural coal fines

Pulverized Coal Combustion: The Influence of Flame Temperature

A laboratory combustor was used to investigate the factors that influence the conversion of fuel nitrogen in coal during coal combustion. Fuel NO was isolated by experimentation utilizing Argon/Oxygen/Carbon Dioxide mixtures as the oxidant, and care was taken to compare cases with air at matched conditions. For both well mixed and slowly mixed flame types, fuel NO contributed over 75% of the total NO emissions for all conditions examined. Fuel NO was insensitive to temperature changes except when the adiabatic flame temperatures were above 2480 0 K (4000°F). At the highest adiabatic flame temperature, 2580 0 K (4200°F), a 10% increase in fuel NO was observed. Four different coals and one coal char were investigated. Fuel NO could not be correlated with fuel nitrogen content alone, even though aerodynamic conditions were kept constant. Fuel nitrogen conversion to NO during pulverized char combustion was 12-16% at a stoichiometric ratio of 1.15 compared to 28% for a pulverized coal of the same nitrogen content. Furthermore, in contrast to the coal results, NO emissions from char combustion were not greatly influenced by changes in injector design. The implication is that although conversion of fuel nitrogen to NO may be relatively low during the char burnout regime of coal combustion, the residual "char NO" may be especially resistant to abatement by modifications of the burner aerodynamics

The Impact of Error-Management Climate, Error Type and Error Originator on Auditors’ Reporting Errors Discovered on Audit Work Papers

We examine factors affecting the auditor’s willingness to report their own or their peers’ self-discovered errors in working papers subsequent to detailed working paper review. Prior research has shown that errors in working papers are detected in the review process; however, such detection rates only rarely exceed 50% of the seeded errors. Hence, measures that encourage auditors to be alert to their own (or their peers’) potential errors any time they revisit the audit working papers may be valuable in detecting such residual errors and potentially correcting them before damage occurs to the audit firm or its client. We hypothesize that three factors affect the auditor’s willingness to report post detailed review discovered errors: the local office error-management climate (open versus blame), the type of error (mechanical versus conceptual) and who committed the error (the individual who committed the error (self) or a peer). Local office error-management climate is said to be open and supportive where errors and mistakes are accepted as part of everyday life as long as they are learned from and not repeated. In alternative, a blame error-management climate focuses on a “get it right the first time” culture where mistakes are not tolerated and blame gets attached to those admitting to or found committing such errors. We find that error-management climate has a significant overall effect on auditor willingness to report errors, as does who committed the error originally. We find both predicted and unpredicted significant interactions among the three factors that qualify these observed significant main effects. We discuss implications for audit practice and further research

Minimization of NO Emissions From Multi-Burner Coal-Fired Boilers Semi-Annual Report

Coal continues to be one of the principal energy sources for electric power generation in the United States. One of the biggest environmental challenges involved with coal utilization is the reduction of nitrogen oxides (NO{sub x}) formed during coal combustion. The most economical method of NO{sub x} abatement in coal combustion is through burner modification. Air-staging techniques have been widely used in the development of low-NO{sub x} pulverized coal burners, promoting the conversion of NO{sub x} to N{sub 2} by delaying the mixing in the fuel-rich zone near the burner inlet. Previous studies have looked at the mechanisms of NO{sub x} evolution at relatively low temperatures where primary pyrolysis is dominant, but data published for secondary pyrolysis in the pulverized coal furnace are scarce. In this project, the nitrogen evolution behavior during secondary coal pyrolysis will be explored. The end result will be a complete model of nitrogen evolution and NO{sub x} precursor formation due to primary and secondary pyrolysis

Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Siedlecki, S. A., Salisbury, J., Gledhill, D. K., Bastidas, C., Meseck, S., McGarry, K., Hunt, C. W., Alexander, M., Lavoie, D., Wang, Z. A., Scott, J., Brady, D. C., Mlsna, I., Azetsu-Scott, K., Liberti, C. M., Melrose, D. C., White, M. M., Pershing, A., Vandemark, D., Townsend, D. W., Chen, C,. Mook, W., Morrison, R. Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations. Elementa: Science of the Anthropocene, 9(1), (2021): 00062, https://doi.org/10.1525/elementa.2020.00062.Ocean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.This research was financially supported by the Major Special Projects of the Ministry of Science and Technology of China (2016YFC020600), the Young Scholars Science Foundation of Lanzhou Jiaotong University (2018033), and the Talent Innovation and Entrepreneurship Projects of Lanzhou (2018-RC-84)

In Vivo Methods for the Assessment of Topical Drug Bioavailability

This paper reviews some current methods for the in vivo assessment of local cutaneous bioavailability in humans after topical drug application. After an introduction discussing the importance of local drug bioavailability assessment and the limitations of model-based predictions, the focus turns to the relevance of experimental studies. The available techniques are then reviewed in detail, with particular emphasis on the tape stripping and microdialysis methodologies. Other less developed techniques, including the skin biopsy, suction blister, follicle removal and confocal Raman spectroscopy techniques are also described

Development and validation of a predictive model for American Society of Anesthesiologists Physical Status

Abstract Background The American Society of Anesthesiologists Physical Status (ASA-PS) classification system was developed to categorize the fitness of patients before surgery. Increasingly, the ASA-PS has been applied to other uses including justification of inpatient admission. Our objectives were to develop and cross-validate a statistical model for predicting ASA-PS; and 2) assess the concurrent and predictive validity of the model by assessing associations between model-derived ASA-PS, observed ASA-PS, and a diverse set of 30-day outcomes. Methods Using the 2014 American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) Participant Use Data File, we developed and internally cross-validated multinomial regression models to predict ASA-PS using preoperative NSQIP data. Accuracy was assessed with C-Statistics and calibration plots. We assessed both concurrent and predictive validity of model-derived ASA-PS relative to observed ASA-PS and 30-day outcomes. To aid further research and use of the ASA-PS model, we implemented it into an online calculator. Results Of the 566,797 elective procedures in the final analytic dataset, 8.9% were ASA-PS 1, 48.9% were ASA-PS 2, 39.1% were ASA-PS 3, and 3.2% were ASA-PS 4. The accuracy of the 21-variable model to predict ASA-PS was C = 0.77 +/− 0.0025. The model-derived ASA-PS had stronger association with key indicators of preoperative status including comorbidities and higher BMI (concurrent validity) compared to observed ASA-PS, but less strong associations with postoperative complications (predictive validity). The online ASA-PS calculator may be accessed at https://s-spire-clintools.shinyapps.io/ASA_PS_Estimator/ Conclusions Model-derived ASA-PS better tracked key indicators of preoperative status compared to observed ASA-PS. The ability to have an electronically derived measure of ASA-PS can potentially be useful in research, quality measurement, and clinical applications.https://deepblue.lib.umich.edu/bitstream/2027.42/152155/1/12913_2019_Article_4640.pd

Combustion 2000

This report is a presentation of work carried out on Phase II of the HIPPS program under DOE contract DE-AC22-95PC95144 from June 1995 to March 2001. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations. HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design) Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests) There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract. The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and {le} 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas. To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine. The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 F (1260-1371 C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. The UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by the choice of gas turbine and the matching steam turbine, the design process of the High Temperature Advanced Furnace (HITAF) moved ineluctably to a down-fired, slagging configuration. This design was based on two air heaters: one a high temperature slagging Radiative Air Heater (RAH) and a lower temperature, dry ash Convective Air Heater (CAH). The specific details of the air heaters are arrived at by an iterative sequence in the following order:-Starting from the overall Cycle requirements which set the limits for the combustion and heat transfer analysis-The available enthalpy determined the range of materials, ceramics or alloys, which could tolerate the temperatures-Structural Analysis of the designs proved to be the major limitation-Finally the commercialization issues of fabrication and reliability, availability and maintenance. The program that has sought to develop and implement these HIPPS designs is outlined below