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Computational Modeling and Experimental Studies on NO(x) Reduction Under Pulverized Coal Combustion Conditions

Description: During this quarter efforts were made to conduct reburning experiments with coal. Our efforts met with partial success but there arose persistent problems with the operation of the coal feeder. This entire quarter has been the most challenging time for the research team in terms of solving the problems and carrying out the intended experiments. Discussed below are some of the results as well as challenges. We hope to overcome the problems in due time. At the writing of this report, some parts of the coal feeder are being rebuilt by MK Fabrication.
Date: September 1, 1997
Creator: Kumpaty, S.K.; Subramanian, K. & Hodges, T.L.
Partner: UNT Libraries Government Documents Department

Experiments and Computational Modeling of Pulverized Coal Ignition

Description: Under typical conditions of pulverized coal combustion, which is characterized by fines particles heated at very high rates, there is currently a lack of certainty regarding the ignition mechanism of bituminous and lower rank coals. It is unclear whether ignition occurs first at the particle oxygen interface (heterogeneous ignition) or if it occurs in the gas phase due to ignition of the devolatilization products (homogeneous ignition). Furthermore, there have been no previous studies aimed at determining the dependence of the ignition mechanism on variations in experimental conditions, such as particle size, oxygen concentration, and heating rate. Finally, there is a need to improve current mathematical models of ignition to realistically and accurately depict the particle-to-particle variations that exist within a coal sample. Such a model is needed to extract useful reaction parameters from ignition studies, and to interpret ignition data in a more meaningful way.
Date: May 1, 1997
Creator: Chen, J.C.
Partner: UNT Libraries Government Documents Department

EFFECT OF HEATING RATE ON THE THERMODYNAMIC PROPERTIES OF PULVERIZED COAL

Description: This semi-annual technical progress report describes work performed under DOE Grant No. DE-FG22-96PC96224 during the period March 24, 1998 to September 23, 1998 which covers the fourth six months of the project. Existing laser heating set-up at the Single Particle Laboratory, Federal Energy Technology Center, Morgantown, WV would work only in the range of 10 to 10 4 5 K/s. During this reporting period, appropriate changes were made to the laser heating system to heat particles in the range of 10 to 10 K/s. Also, calibration for all the components of the 4 7 electrodynamic balance measurement system including single-color pyrometer and heating laser was successfully completed. Following the calibration, a large number of single coal particles were caught in the electrodynamic balance and their volume, external surface area, mass, and density were measured. The same single particles were then heated bidirectionally with a pulsed (10 ms pulse width) Nd:YAG laser beams of equal intensity. The temporal power variation in the laser pulse was monitored for use in the heat transfer analysis by an ultra-fast fiber optic uv light transmitter included in the beam path and coupled to a silicon photodiode. Measurements of changes in particle size that accompanied rapid heating was made by means of the high-speed diode array imaging system discussed in our previous reports. Dynamics of volatile evolution and particle swelling were recorded using well established time-resolved high-speed cinematography. Measurements of the radiant emissive power from the heated and cooled (when the laser is turned off) particles was made using the single-color pyrometer. The above experiments are being repeated for a significant number of coal particles for a number of heating rates in between 10 - 10 K/s at FETC, Morgantown. 4 7 Shipment of the donated heated grid system components from our industrial partner, United Technologies ...
Date: October 27, 1998
Creator: SAMPATH, RAMANATHAN
Partner: UNT Libraries Government Documents Department

Pulverization Induced Charge: In-Line Dry Coal Cleaning

Description: The technical feasibility of separating mineral matter and pyrite from coal as it is transported from pulverizers to boilers in pulverized coal combustion units will be examined. The charge imparted on coal during pulverization and transport to pulverized coal (PC) burners in a utility boiler will be quantified. In addition to field charge measurements, an existing computational model will be extended to numerically simulate charged particle motion in a turbulent gas through an electric field. Results from the field tests and numerical modeling will be employed in design and construction of a laboratory scale pulverizer/classifier. This laboratory unit will be used to quantify the magnitude and differential charge imparted on bituminous and subbituminous coals during pulverization and classification at temperatures and with gaseous constituents typical to utility PC units. An electrostatic separator, designed for in-line operation between pulverizers and PC boilers, will be used to clean prepulverized coals. Theoretical and experimental data are to be used in preparing a preliminary design for a full-scale, (15 ton/hr) in-line, electrostatic coal cleaning device. Finally, the economic potential for application to PC units will be assessed.
Date: May 13, 1997
Creator: Schaefer, J.L. & Stencel, J.M.
Partner: UNT Libraries Government Documents Department

Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, April 1, 1997--June 30, 1997

Description: 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.
Date: August 7, 1997
Creator: Harb, J.N.
Partner: UNT Libraries Government Documents Department

Pulverization induced charge: In-line dry coal cleaning. Technical progress report No. 7, January 1, 1996--March 31, 1996

Description: Task 1 on charge determinations has been completed with additional measurements taken at the TVA Widows Creek plant. The probe which was designed and constructed for the field charge measurements proved to be effective in determining the average charge of pulverized coal particles. The charge measurements conducted at EKP`s Spurlock Station power plant and TVA`s Widows Creek plant have both yielded results which are in the same order of magnitude as those determined in controlled laboratory experiments. Under Task 3, coal separation determinations, separation tests performed on-site, combined with the charge measurements, showed that the charge generated by coal pulverization was sufficient for electrostatic separation of coal from mineral matter. These tests were conducted using a separation probe with different electric field strengths, i.e., different voltages were used across the two copper plates to generate the electric field. The results under four conditions were consistent and similar in terms of separation.
Date: August 1, 1996
Partner: UNT Libraries Government Documents Department

Char particle fragmentation and its effects on unburned carbon during pulverized coal combustion. Quarterly report, January 1, 1995--March 31, 1995

Description: This document is the tenth quarterly status report of work on a project concerned with the fragmentation of char particles during pulverized coal combustion that is being conducted at the High Temperature Gasdynamics Laboratory at Stanford University. The project is intended to satisfy, in part, PETC`s research efforts to understand the chemical and physical processes that govern coal combustion. The work is pertinent to the char oxidation phase of coal combustion and focuses on how the fragmentation of coal char particles affects overall mass loss rates and how char fragmentation phenomena influence coal conversion efficiency. The knowledge and information obtained will allow the development of engineering models that can be used to predict accurately char particle temperatures and total mass loss rates during pulverized coal combustion. The overall objectives of the project are: (1) to characterize fragmentation events as a function of combustion environment, (2) to characterize fragmentation with respect to particle porosity and mineral loadings, (3) to assess overall mass loss rates with respect to particle fragmentation, and (4) to quantify the impact of fragmentation on unburned carbon in ash. The knowledge obtained during the course of this project will be used to predict accurately the overall mass loss rates of coals based on the mineral content and porosity of their chars. The work will provide a means of assessing reasons for unburned carbon in the ash of coal fired boilers and furnaces. Accomplishments for this period are presented for Task 3, char fragmentation studies and Task 4, fragmentation modelling.
Date: August 1, 1995
Creator: Mitchell, R.E.
Partner: UNT Libraries Government Documents Department

Advanced, Low/Zero Emission Boiler Design and Operation

Description: This document reviews the work performed during the quarter April-June 2004. Task 1 (Site Preparation) had been completed 2003, along with three weeks of oxycombustion tests in Task 2 (experimental test performance) of the project. In current reporting period, the experimental testing has been completed: one additional week of tests has been performed to finalize the optimization of the combustion characteristics in O{sub 2}/CO{sub 2} environment ; two more days of testing were dedicated to mercury sampling in air-fired or O{sub 2}-fired conditions, and to characterization of heat transfer in O{sub 2} conditions vs. to air-blown conditions. Task 3 (Techno-Economic Study) has also been completed in current quarter: 250MWe, 500MWe and 1000MWe oxygen-fired PC unit have been simulated and quoted, and their performance and cost have been compared to same-capacity air-fired pulverized coal (PC) unit and IGCC. New and retrofit cases have been evaluated. The comparison has been completed in terms of capital cost, operating cost, cost of electricity and cost of CO{sub 2} avoided. The scope of task 4 (Conceptual Boiler Design) had been modified as per DOE request in previous quarter. Engineering calculations are currently in progress. Next steps include detail review of the experimental data collected during the entire testing campaign, finalization of detailed report on economic task, and reporting of the preliminary results in the boiler design task. Two papers summarizing the project main achievements have been presented at Clearwater coal conference in April 2004 (overall project results), and at the CO{sub 2} sequestration conference in May 2004 (emphasis on economics). Out of the {approx}$785k allocated DOE funds in this project, $545k have been spent to date, mainly in site preparation, test performance and economics assessment. In addition to DOE allocated funds, to date approximately $400k have been cost-shared by the participants, bringing the total project ...
Date: June 30, 2004
Creator: Chatel-Pelage, Fabienne & Varagani, Rajani
Partner: UNT Libraries Government Documents Department

POC-scale testing of a dry triboelectrostatic separator for fine coal cleaning. Second quarterly technical progress report, January 1, 1996--March 31, 1996

Description: The Pittsburgh Energy Technology Center (PETC) developed a triboelectrostatic separation (TES) process which is capable of removing mineral matter from coal without using water. A distinct advantage of this dry coal cleaning process is that it does not entail costly steps of dewatering which is a common problem associated with conventional fine coal cleaning processes. It is the objective of this project to conduct a series of proof-of-concept (POC) scale tests at a throughput of 200--250 kg/hr and obtain scale- up information. Prior to the POC testing, bench-scale test work will be conducted with the objective of increasing the separation efficiency and throughput, for which changes in the basic designs for the charger and the separator may be necessary. The bench- and POC- scale test work will be carried out to evaluate various operating parameters and establish a reliable scale-up procedure. The scale-up data will be used to analyze the economic merits of the TES process. All required documents associated with project planning were completed and submitted to DOE for approval during the second quarter of this project. Approval of the project work plan is still pending at this time subject to additional review by DOE of requested modifications to the statement of work. Accomplishments during this reporting period include the set-up of an apparatus for assessing tribocharger performance, continued construction of the bench-scale (1 kg/hr) triboelectrostatic separator and initial development of a fundamental model for predicting the motion of charged particles in a non-uniform electrostatic field.
Date: August 1, 1996
Creator: Yoon, R.-H.; Luttrell, G.H. & Adel, G.T.
Partner: UNT Libraries Government Documents Department

Advanced combustor design concepts to control NO{sub x} and air toxics. Quarterly report, April--June 1996

Description: The ability to accurately model NO{sub x} formation from coal combustion requires an understanding of the mechanisms of volatile-N and char-N oxidation and reduction. This study has focused on NO{sub x} formation from the char-N fraction of coal since much less is known about the fate of char-N than that of volatile-N. As stated in earlier reports, chars from five different coals were collected for this study. These chars were subsequently burned in a simulated coal flame (see report for quarter ending 12/95) under a variety of conditions. The experimental phase of the study is now complete and key results are included in this report.
Date: June 30, 1996
Creator: Pershing, D.W.; Lighty, J.; Spinti, J. & Veranth, J.
Partner: UNT Libraries Government Documents Department

Suppression of fine ash formation in pulverized coal flames. Final technical report, September 30, 1992--January 31, 1996

Description: Coal ash, and particularly fine fly ash, remain one of the principal practical and environmental problems in coal-based power generation. In particular, submicron aerosols are identified with direct inhalation risk. Submicron ash is thought to arise from mineral vaporization during char combustion, followed by nucleation, condensation and coagulation to yield an aerosol. While aerosols are predominantly made out of volatile alkali minerals, they also can include refractory oxides that are chemically reduced to more volatile forms within the char particle and vaporized. Most of the ash of size greater than 1 {mu}m is generated by agglomeration of mineral as the char particle bums out. These two principal mechanisms are thought to account for most of the ash generated in coal combustion. Previous research has shown that various forms of coal treatment can influence the yields of fine ash from combustion. The research reported here investigates various forms of treatment, including physical coal cleaning, aerodynamic sizing, degree of grinding, and combinations of these on both aerosol yields and on yields of fine residual ash (1-4 {mu}m). The work also includes results from the combustion of artificial chars that include individual mineral elements. This research shows that these various forms of coal treatment can significantly change ash characteristics. While none of the treatments affected the bulk of the residual ash size distribution significantly, the yield of the ash aerosol mode (d<0.5 {mu}m) and fine residual ash mode (1-4 {mu}m) are changed by the treatments.
Date: July 19, 1996
Creator: Kramlich, J.C.; Chenevert, B.; Park, Jungsung; Hoffman, D.A. & Butcher, E.K.
Partner: UNT Libraries Government Documents Department

Ignition rate measurement of laser-ignited coals. Quarterly report, January 1, 1996--March 31, 1996

Description: Over the last several decades many experiments have been conceived to study the ignition of pulverized coal and other solid fuels. We are constructing a laser-based apparatus which offers several advantages over those currently in favor. Sieve-sized particles are dropped batch-wise into a laminar, upward-flow wind tunnel which is constructed with a quartz test section. The gas stream is not preheated. A single pulse from a Nd:YAG laser is focused through the tunnel and ignites several particles. The transparent test section and cool walls allow for application of two-color pyrometry to measure the particles` temperature history during ignition and combustion. Coals ranging in rank from lignites to low-volatile bituminous, and chars derived from these coals, will be studied in this project. For each fuel type, measurements of the ignition temperature under various experimental conditions (particle size and free-stream oxygen concentration), combined with a detailed analysis of the ignition process, will permit the determination of kinetic rate constants of ignition.
Date: April 28, 1996
Creator: Chen, J.C. & Kabadi, V.
Partner: UNT Libraries Government Documents Department

Computational modeling and experimental studies on NO{sub x} reduction under pulverized coal combustion conditions. Seventh quarterly technical progress report, July 1, 1996--September 30, 1996

Description: During this quarter (July-August 1996), the experiments for nitric oxide reburning with a combination of methane and ammonia were conducted successfully. This marked the completion of gaseous phase experiments. Preparations are underway for the reburning studies with coal. A coal feeder was designed to suit our reactor facility which is being built by MK Fabrication. The coal feeder should be operational in the coming quarter. Presented here are the experimental results of NO reburning with methane/ammonia. The results are consistent with the computational work submitted in previous reports.
Date: December 31, 1996
Creator: Kumpaty, S.K.; Subramanian, K.; Nokku, V.P. & Hodges, T.L.
Partner: UNT Libraries Government Documents Department

Mineral matter effects on char structural evolution and oxidation kinetics during coal char combustion

Description: The authors report on recent investigations of the evolution of char structure during carbon burnout and the role of mineral matter in determining this structure. Char samples collected in a carefully controlled laminar, flame-supported entrained flow reactor have been characterized using a number of microscopy tools. Observations of the inorganic structure of chars produced at a variety of combustion conditions are coupled with in-situ optical measurements of the char particle population with an eye towards identifying the mechanism of mineral interaction and its effects on carbon burnout kinetics during pulverized coal char combustion. Preliminary results show a surprising amount of inorganic mineral in solid solution with the carbonaceous matrix. This intimate mixing of organic and inorganic constituents may affect reactivity by both blocking oxygen access to active carbon sites and influencing the microscopic carbon structure that evolves during combustion.
Date: October 1, 1997
Creator: Lunden, M.; Yang, N.; Headley, T.; Shaddix, C. & Hardesty, D.
Partner: UNT Libraries Government Documents Department

Combustion of pulverized coal in vortex structures. Quarterly progress report No. 8, July 1, 1995--September 30, 1995

Description: This eighth quarterly report describes the activities and accomplishments of the research team at the University of Oklahoma, Norman, Oklahoma, related to the project entitled {open_quotes}Combustion of Pulverized Coal in Vortex Structures{close_quotes} during the period July 1, 1995 to September 30, 1995. The work performed in this quarter consisted of the following four tasks: (i) Completion of the schlieren flow visualization experiments, (ii) Conducting experiments with particulate laden shear layers in cold flow to measure mean velocity and turbulence intensity field, (iii) Conducting experiments with particulate laden shear layers in heated flow where the initial temperature was above the pyrolysis temperature of the coal, (iii) Conducting experiments with particulate laden shear layers in heated flow where the initial temperature was above the ignition temperature of the coal, and (iv) Revising and preparing the final version of a paper for the Energy Conference to be held in Houston in 1996. A 90-day no-cost extension of the project was obtained. In the final quarter, we plan to complete this work by conducting the final task of measuring concentration fields.
Date: October 1, 1995
Creator: Gollahalli, S.R.
Partner: UNT Libraries Government Documents Department

Hydrothermally treated coals for pulverized coal injection. Final technical report

Description: This project investigated the suitability of hydrothermally dried low-rank coals for pulverized fuel injection into blast furnaces in order to reduce coke consumption. Coal samples from the Beluga coalfield and the Usibelli Coal Mine, Alaska, were used for the study. Crushed coal samples were hydrothermally treated at three temperatures, 275, 300 and 325{degrees}C, for residence times of 10, 60 and 120 minutes. Products were characterized to determine their suitability for pulverized coal injection. Characterization included proximate and ultimate analyses, vitrinite reflectance and TGA reactivity. A literature survey was also conducted.
Date: October 1, 1995
Creator: Walsh, D.E.; Rao, P.D.; Ogunsola, O. & Lin, H.K.
Partner: UNT Libraries Government Documents Department

Effect of Heating Rate on the Thermodynamic Properties of Pulverized Coal

Description: This semi-annual technical progress report describes work performed under DOE Grant No.DE-FG22-96PC96224 during the period September 24, 1997 to April 23, 1998 which covers the third six months of the project. During this reporting period, several components of the electrodynamic balance measurement system, Single Particle Laboratory, Federal Energy Technology center, Morgantown, WV, were successfully calibrated. A large number of single polystyrenespheres covering a size range of 80 - 200 microns in diameter were caught in the electrodynamic balance. The size counts of their projected images obtained using the top video-based imaging system, bottom video-based imaging system, and diode-array imaging system were calibrated against the actual size of the particles to within ± 3 microns. Signals obtained by the particle position control system were also calibrated against the actual movement of a polystyrene particle in the balance to within ± 1 microns. Presently, calibration of the Single Color Pyrometer to measure coal particle temperature histories is in progress. Donation agreement for the Heated-Grid measurement system from our industrial partner, United Technologies Research Center (UTRC), CT, was obtained and the arrangement for the completion of the shipment of the grid system components from UTRC to CAU is in progress. Several theoretical analyses were conducted to improve the model performance of the present work and the results were compared with data available from our previous studies. These activities resulted in several publications including three conference papers, and one student poster paper during this reporting period.
Date: May 1, 1998
Creator: Sampath, Ramanathan
Partner: UNT Libraries Government Documents Department

Combustion of pulverized coal in vortex structures. Quarterly progress report No. 7, April 1, 1995--June 30, 1995

Description: This seventh quarterly report describes the activities and accomplishments of the research team at the University of Oklahoma, Norman, Oklahoma, related to the project entitled {open_quotes}Combustion of Pulverized Coal in Vortex Structures{close_quotes} during the period April 1, 1995 to June 30, 1995. The work performed in this quarter consisted of the following four tasks: (i) conducting experiments with particulate laden shear layers to measure mean velocity and turbulence intensity field (ii) preparing an abstract for the 1995 UCR contractor`s meeting, and a paper for the Energy Conference to be held in Houston in 1996, (iii) participating and presenting a paper UCR meeting in Nashville, Tennessee, (iv) design and installation of devices to traverse the test section while keeping the optics undisturbed, and (v) and design and testing of a natural gas burner system to heat either of the streams to conduct pyrolysis and combustion experiments. In the next quarter, we plan to continue this work with heated shear layers in which particles undergo pyrolysis and combustion. Flow visualization and mean velocity field measurement instrumentation will continue as the major experimental techniques.
Date: July 1, 1995
Creator: Gollahalli, S.R.
Partner: UNT Libraries Government Documents Department

A distributed activation energy model of heterogeneous coal ignition. Technical progress report, January 1--March 31, 1995

Description: Experiments designed to measure kinetic rate constants of ignition of pulverized coals showed clearly that, for single particles or dilute suspensions, particle-to-particle variations due to reactivity and/or thermophysical properties are important. There exists ample evidence that the most important factor in interpreting these data is the existence of a variation in chemical reactivity in the sample. It is surprising, therefore, to note that all previous studies presumed that a single (average) activation energy is adequate to describe the ignition process. The equations formulated using this presumption are then correlated to the experimental measurements to infer the kinetic rate constants of ignition. The major objectives are to develop a model of heterogeneous ignition which allows for a distribution of activation energies, and to implement this model to interpret previously published data. It is the authors hypothesis that variations in chemical reactivity account for the experimental trends observed. Another objective of this project is to examine the effects of variations in thermodynamic and physical properties (e.g. specific heat, particle diameter, density) on data interpretation from previous ignition experiments.
Date: April 26, 1995
Creator: Chen, J.C.
Partner: UNT Libraries Government Documents Department

Combustion of pulverized coal in vortex structures. Quarterly progress report No. 6, January 1, 1995--March 31, 1995

Description: This sixth quarterly report describes the activities and accomplishments of the research team at the University of Oklahoma, Norman, Oklahoma, related to the project entitled ``Combustion of Pulverized Coal in Vortex Structures`` during the period January 1, 1995 to March 31, 1995. The work performed in this quarter consisted of the following four tasks: (1) design and fabrication of a computer-driven traversing mechanism for traversing LDV transmitter and receiving optics, (2) color schlieren photography, (3) presenting a report in the panel-review meeting in Pittsburgh, (4) installation of additional safety devices in response to the letter of Dr. Sean Plasynski, and (5) streamwise velocity measurement in the isothermal heterogeneous shear layer with nonreacting particles using LDV. In the next quarter, we plan to continue this work with heated shear layers in which particles undergo pyrolysis. Flow visualization and mean velocity field measurement instrumentation will continue as the major experimental techniques.
Date: March 1, 1995
Creator: Gollahalli, S.R.
Partner: UNT Libraries Government Documents Department

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, January 1, 1996--March 31, 1996

Description: This document is the seventh quarterly status report on a project that is conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub X} pulverized coal (P. C.) combustion. The project aims to identify the mechanisms of pyrite combustion and to quantify their effects, in order to formulate a general rate expression for the combustion of pyrite that accounts for coal properties as well as furnace conditions. In general, the project has the following objectives: 1) the characterization of the various mechanisms of intraparticle mass transfer and chemical reaction that control overall pyrite combustion rates and 2) the synthesis of the reaction rate resistances of the various mechanisms into a general rate expression for pyrite combustion. The knowledge gained from this project will be incorporated into numerical codes and utilized to formulate slagging abatement strategies involving the minor adjustment of firing conditions. Ultimately, the benefit of this research program is intended to be an increase in the range of coals compatible with staged, low-NO{sub X} combustor retrofits. 9 refs., 12 figs.
Date: May 1, 1996
Creator: Akan-Etuk, A.E.J. & Mitchell, R.E.
Partner: UNT Libraries Government Documents Department

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, April 1, 1996 - June 30, 1996

Description: This document is the eighth quarterly status report on a project that is conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P. C.) combustion. In general, the project has the following objectives: (1) the characterization of the various mechanisms of intraparticle mass transfer and chemical reaction that control overall pyrite combustion rates and (2) the synthesis of the reaction rate resistances of the various mechanisms into a general rate expression for pyrite combustion. The knowledge gained from this project will be incorporated into numerical codes and utilized to formulate slagging abatement strategies involving the minor adjustment of firing conditions. Ultimately, the benefit of this research program is intended to be an increase in the range of coals compatible with staged, low-NO{sub X} combustor retrofits.
Date: December 1, 1996
Creator: Das, K.; Akan-Etuk, A. E. J. & Mitchell, R. E.
Partner: UNT Libraries Government Documents Department

Investigation of mineral transformations and ash deposition during staged combustion. Quarterly technical progress report, April 1, 1996--June 30, 1996

Description: 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.
Date: August 1, 1996
Creator: Harb, J.N.
Partner: UNT Libraries Government Documents Department