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Preferential recycling/rejection in CFBC/FBC systems using triboelectrostatic separation

Description: Circulating Fluidized Bed Combustion (CFBC) and Fluidized Bed Combustion (FBC) with recirculation are widely used technologies in the US for power generation. They have the advantage of fuel flexibility, and low NO{sub x} and SO{sub x} emissions. Typically, as partially combusted fuel is circulated in the system, only a split stream of this circulating stream is rejected, with remainder recycled to the combustor. As a consequence, there is unburned carbon and partially used, valuable, calcium hydroxide in the reject stream. If these useful materials in the reject stream can be recovered and sent back to the combustor, the efficiency of the system will be increased significantly and the equivalent emissions will be lower. This project studies an innovative concept to incorporate triboelectric separation into CFBC/FBC systems in order to preferentially split its recycle/reject streams based on material compositions of the particles. The objective is to answer whether useful constituents, like carbon, calcium carbonate and calcium hydroxide or oxide, can be selectively separated from combustion ash at elevated temperatures. Laboratory experimental studies are performed at temperatures from 25 C to 210 C, the data from which are presented in the form of recovery curves. These curves present quality-versus-quantity information useful for predicting the efficacy of triboelectric separation as applied to CFBC/FBC byproduct recycling and/or rejection.
Date: May 25, 2000
Creator: Ban, Heng & Stencel, J.M.
Partner: UNT Libraries Government Documents Department

Preferential recycling/rejection in CFBC/FBC systems using triboelectrostatic separation

Description: Circulating Fluidized Bed Combustion (CFBC) and Fluidized Bed Combustion (FBC) with recirculation are widely used technologies in the US for power generation. They have the advantage of fuel flexibility, and low NO{sub x} and SO{sub x} emissions. Typically, as partially combusted fuel is circulated in the system, only a split stream of this circulating stream is rejected, with remainder recycled to the combustor. As a consequence, there is unburned carbon and partially used, valuable, calcium hydroxide in the reject stream. If these useful materials in the reject stream can be recovered and sent back to the combustor, the efficiency of the system will be increased significantly and the equivalent emissions will be lower. This project studies an innovative concept to incorporate triboelectric separation into CFBC/FBC systems in order to preferentially split its recycle/reject streams based on material compositions of the particles. The objective is to answer whether useful constituents, like carbon, calcium carbonate and calcium hydroxide or oxide, can be selectively separated from combustion ash at elevated temperatures. Laboratory experimental studies are performed at temperatures from 25 C to 210 C, the data from which are presented in the form of recovery curves. These curves present quality-versus-quantity information useful for predicting the efficacy of triboelectric separation as applied to CFBC/FBC byproduct recycling and/or rejection.
Date: May 25, 2000
Creator: Ban, Heng & Stencel, J.M.
Partner: UNT Libraries Government Documents Department

Preferential recycling/rejection in CFBC/FBC systems using triboelectrostatic separation

Description: Circulating Fluidized Bed Combustion (CFBC) and Fluidized Bed Combustion (FBC) with recirculation are widely used technologies in the US for power generation. They have the advantage of fuel flexibility, and low NO{sub x} and SO{sub x} emissions. Typically, as partially combusted fuel is circulated in the system, only a split stream of this circulating stream is rejected, with remainder recycled to the combustor. As a consequence, there is unburned carbon and partially used, valuable, calcium hydroxide in the reject stream. If these useful materials in the reject stream can be recovered and sent back to the combustor, the efficiency of the system will be increased significantly and the equivalent emissions will be lower. This project studies an innovative concept to incorporate triboelectric separation into CFBC/FBC systems in order to preferentially split its recycle/reject streams based on material compositions of the particles. The objective is to answer whether useful constituents, like carbon, calcium carbonate and calcium hydroxide or oxide, can be selectively separated from combustion ash at elevated temperatures. Laboratory experimental studies are performed at temperatures from 25 C to 210 C, the data from which are presented in the form of recovery curves. These curves present quality-versus-quantity information useful for predicting the efficacy of triboelectric separation as applied to CFBC/FBC byproduct recycling and/or rejection.
Date: May 25, 2000
Creator: Ban, Heng & Stencel, J.M.
Partner: UNT Libraries Government Documents Department

Commercial Demonstration of the Manufactured Aggregate Processing Technology Utilizing Spray Dryer Ash

Description: This quarterly report covers the period from July 1st, 2004 through September 30th, 2004. It covers: technical development, permitting status, engineering status, construction status, operations summary and marketing support activities for this period. Plant startup, including equipment and system debugging, is underway. Minor adjustments to the SDA feed system, pug mill, and extruder were completed. Testing of admixtures to prevent the wetted SDA from sticking is continuing. The power plant is implementing a lime optimization program to reduce the calcium hydroxide values in the ash.
Date: November 1, 2004
Creator: Scandrol, Roy
Partner: UNT Libraries Government Documents Department

Modeling precipitation from concentrated solutions with the EQ3/6 chemical speciation codes

Description: One of the more important uncertainties of using chemical speciation codes to study dissolution and precipitation of compounds is the results of modeling which depends on the particular thermodynamic database being used. The authors goal is to investigate the effects of different thermodynamic databases on modeling precipitation from concentrated solutions. They used the EQ3/6 codes and the supplied databases to model precipitation in this paper. One aspect of this goal is to compare predictions of precipitation from ideal solutions to similar predictions from nonideal solutions. The largest thermodynamic databases available for use by EQ3/6 assume that solutions behave ideally. However, two databases exist that allow modeling nonideal solutions. The two databases are much less extensive than the ideal solution data, and they investigated the comparability of modeling ideal solutions and nonideal solutions. They defined four fundamental problems to test the EQ3/6 codes in concentrated solutions. Two problems precipitate Ca(OH){sub 2} from solutions concentrated in Ca{sup ++}. One problem tests the precipitation of Ca(OH){sub 2} from high ionic strength (high concentration) solutions that are low in the concentrations of precipitating species (Ca{sup ++} in this case). The fourth problem evaporates the supernatant of the problem with low concentrations of precipitating species. The specific problems are discussed.
Date: January 13, 1995
Creator: Brown, L. F. & Ebinger, M. H.
Partner: UNT Libraries Government Documents Department

BIO-ORGANIC CHEMISTRY QUARTERLY REPORT. December 1961, January andFebruary 1962

Description: It has been known for a hundred years that formaldehyde polymerizes to carbohydrate substances in alkaline media. Although the reaction has long attracted much attention, only recently has a detailed qualitative analysis of the products been carried out by chromatographic methods. We have started to re-examine this reaction by combining chromatography with radioactive tracer techniques in the hope of refining the quantitative aspects of the analysis. Our particular interest has been to develop methods for determining the relative proportions of ribose and ribulose in the mixtures of sugars formed in basic media, as well as under other polymerizing conditions. The finding of large amounts of these sugars might help to explain the occurrence of ribose as the only basic sugar in the fundamental replicating molecules--the nucleic acids. Formaldehyde is thought to have been present in the primitive reducing atmosphere which existed before life first appeared. The ribonucleic acids must have appeared in the constitution of reproducing systems at a very early stage in the development of living organisms. In this study, the polymerizations of formaldehyde were carried out in calcium hydroxide suspensions at 40{sup o}. Aliquots of the reaction mixtures were withdrawn at after various time intervals and the alkali was neutralized with sulfuric acid or, in later experiments, with carbon dioxide. The hydrolysis with sulfuric acid that was used initially to break down any polymers was shown to be unnecessary, as identical products were obtained with this treatment and with simple carbon dioxide neutralization.
Date: April 3, 1962
Partner: UNT Libraries Government Documents Department

NUCLEAR POWERED CO2 CAPTURE FROM THE ATMOSPHERE

Description: A process for capturing CO{sub 2} from the atmosphere was recently proposed. This process uses a closed cycle of sodium and calcium hydroxide, carbonate, and oxide transformations to capture dilute CO{sub 2} from the atmosphere and to generate a concentrated stream of CO{sub 2} that is amenable to sequestration or subsequent chemical transformations. In one of the process steps, a fossil-fueled lime kiln is needed, which reduces the net CO{sub 2} capture of the process. It is proposed to replace the fossil-fueled lime kiln with a modified kiln heated by a high-temperature nuclear reactor. This will have the effect of eliminating the use of fossil fuels for the process and increasing the net CO{sub 2} capture. Although the process is suitable to support sequestration, the use of a nuclear power source for the process provides additional capabilities, and the captured CO{sub 2} may be combined with nuclear-produced hydrogen to produce liquid fuels via Fischer-Tropsch synthesis or other technologies. Conceivably, such plants would be carbon-neutral, and could be placed virtually anywhere without being tied to fossil fuel sources or geological sequestration sites.
Date: September 22, 2008
Creator: Sherman, S
Partner: UNT Libraries Government Documents Department

Investigation of early growth of calcium hydroxide crystals in cement solution by soft x-ray transmission microscopy

Description: Research on cement hydration was performed at the full-field soft transmission X-ray microscope XM-1 located at beamline 6.1.2 at the Advanced Light Source (ALS) in Berkeley CA which is operated by the Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California. A series of works [1-3] has been conducted using this microscope for the in situ observation and qualitative analysis of through-solution hydration products and products of topochemical reactions, which form in cementitious aqueous solutions. This paper studies the precipitation of the calcium hydroxide (CH) crystals from the cement solution. The analysis of successive images of the hydration process provides critical quantitative information about the growth rate of calcium hydroxide (CH) crystals, the supersaturation ratio, and the kinetic and diffusion coefficients of the growth process. ASTM Type II portland cement and 6% C{sub 4}A{sub 3}{bar S} admixture were mixed in aqueous solution and saturated with respect to CH and gypsum. The C{sub 4}A{sub 3}{bar S} admixture was included in the experimental program because of the general research program on expansive cements, and adding C{sub 4}A{sub 3}{bar S} to portland cement is an efficient method of generating ettringite and significant early-age expansion. The solution/solid materials ratio was 10 cm{sup 3}/g, which is higher than the one existing in regular concrete and mortars; to compensate for this dilution, the solution was originally saturated with CH and gypsum. To allow sufficient transmission of the soft X-rays, a small droplet was taken from the supernatant solution and assembled in the sample holder, and then squeezed between two silicon nitride windows for the analysis. The X-ray optical setup of the microscope XM-1 is described elsewhere [2]. In this experiment, a wavelength of 2.4 nm (516.6 eV) was used. The radiation transmitting the sample was detected using an X-ray CCD camera, with a resolution of ...
Date: February 2, 2009
Creator: Harutyunyan, V. S.; Kirchheim, A. P.; Monteiro, P. J. M.; Aivazyan, A. P. & Fischer, P.
Partner: UNT Libraries Government Documents Department

Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

Description: The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a "primer" on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the "primer," a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures.
Date: June 1, 2007
Creator: Naus, Dan J; Mattus, Catherine H & Dole, Leslie Robert
Partner: UNT Libraries Government Documents Department

A conceptual performance assessment model of the dissolved actinide source term for the WIPP

Description: This paper presents a performance assessment model of dissolved actinide concentrations for the Waste Isolation Pilot Plant (WIPP). The model assesses the concentration of each actinide oxidation state and combines these concentrations with an oxidation state distribution. The chemical behavior of actinides in the same oxidation state is presumed to be very similar for almost all situations, but exceptions arising from experimental evidence are accommodated. The code BRAGFLO calculates the gas pressure, brine mass, gas volume, and mass of remaining Fe and cellulosics for each time step and computational cell. The total CO{sub 2} in the repository and dissolved Ca(OH){sub 2} is estimated. Lookup tables are constructed for pmH and f(CO{sub 2}) as a function of brine type and volume, moles of CO{sub 2}, and Ca(OH){sub 2}. Amounts of five soluble complexants are considered. A model based on the formulation of Harvie et al. produces tables of solubilities for each actinide oxidation state as a function of pmH, f(CO{sub 2}), brine composition, and complexant. Experimental data yield lookup tables of fractions of Th, U, Np, Pu, and Am in each oxidation state as a function of f(CO{sub 2}) and complexant. The tables are then used to provide a concentration of a particular actinide at particular values of pmH and f(CO{sub 2}). Under steady-state conditions, the oxidation state of each actinide that is most stable in the particular chemical environment controls the concentration of that actinide in solution. In the absence of steady-state conditions, the oxidation state distribution of interest is that of the dissolved actinide, and the oxidation states may be treated as if they were separate compounds.
Date: December 31, 1996
Creator: Weiner, R.F.; Stockman, C.T.; Wang, Y. & Novak, C.F.
Partner: UNT Libraries Government Documents Department

Different nonideality relationships, different databases and their effects on modeling precipitation from concentrated solutions using numerical speciation codes

Description: Four simple precipitation problems are solved to examine the use of numerical equilibrium codes. The study emphasizes concentrated solutions, assumes both ideal and nonideal solutions, and employs different databases and different activity-coefficient relationships. The study uses the EQ3/6 numerical speciation codes. The results show satisfactory material balances and agreement between solubility products calculated from free-energy relationships and those calculated from concentrations and activity coefficients. Precipitates show slightly higher solubilities when the solutions are regarded as nonideal than when considered ideal, agreeing with theory. When a substance may precipitate from a solution dilute in the precipitating substance, a code may or may not predict precipitation, depending on the database or activity-coefficient relationship used. In a problem involving a two-component precipitation, there are only small differences in the precipitate mass and composition between the ideal and nonideal solution calculations. Analysis of this result indicates that this may be a frequent occurrence. An analytical approach is derived for judging whether this phenomenon will occur in any real or postulated precipitation situation. The discussion looks at applications of this approach. In the solutes remaining after the precipitations, there seems to be little consistency in the calculated concentrations and activity coefficients. They do not appear to depend in any coherent manner on the database or activity-coefficient relationship used. These results reinforce warnings in the literature about perfunctory or mechanical use of numerical speciation codes.
Date: August 1, 1996
Creator: Brown, L.F. & Ebinger, M.H.
Partner: UNT Libraries Government Documents Department

Enhancing the use of coals by gas reburning-sorbent injection. Volume 3, Gas reburning-sorbent injection at Edwards Unit 1, Central Illinois Light Company

Description: Design work has been completed for a Gas Reburning-Sorbent Injection (GR-SI) system to reduce emissions of NO{sub x}, and SO{sub 2} from a wall fired unit. A GR-SI system was designed for Central Illinois Light Company`s Edwards Station Unit 1, located in Bartonville, Illinois. The unit is rated at 117 MW(e) (net) and is front wall fired with a pulverized bituminous coal blend. The goal of the project was to reduce emissions of NO{sub x} by 60%, from the ``as found`` baseline of 0.98 lb/MBtu (420 mg/MJ), and to reduce emissions of S0{sub 2} by 50%. Since the unit currently fires a blend of high sulfur Illinois coal and low sulfur Kentucky coal to meet an S0{sub 2} limit Of 1.8 lb/MBtu (770 mg/MJ), the goal at this site was amended to meeting this limit while increasing the fraction of high sulfur coal to 57% from the current 15% level. GR-SI requires injection of natural gas into the furnace at the level of the top burner row, creating a fuel-rich zone in which NO{sub x} formed in the coal zone is reduced to N{sub 2}. The design natural gas input corresponds to 18% of the total heat input. Burnout (overfire) air is injected at a higher elevation to burn out fuel combustible matter at a normal excess air level of 18%. Recycled flue gas is used to increase the reburning fuel jet momentum, resulting in enhanced mixing. Recycled flue gas is also used to cool the top row of burners which would not be in service during GR operation. Dry hydrated lime sorbent is injected into the upper furnace to react with S0{sub 2}, forming solid CaSO{sub 4} and CaSO{sub 3}, which are collected by the ESP. The SI system design was optimized with respect to gas temperature, injection air ...
Date: October 1, 1994
Partner: UNT Libraries Government Documents Department

High-carbon fly-ash as a binder for iron ore pellets

Description: The goal of this project was to convert currently unusable fly-ashes into a material that can be used as a binder for iron ore. Such a binder would also be useful for other high-volume markets, including foundry sand mold binders. Previously, the investigators used fly-ash in combination with calcium hydroxide as an additive while calcium chloride was added as a hardening accelerator. However, the addition of chloride salts have a detrimental effect because chlorine causes corrosion in processing equipment. Therefore, other potential hardening accelerators were investigated during this project. During production, dried iron-ore pellets are required to have crushing strength of at least 22.2 newtons (5 pounds force) per 12.7 mm (1/2 inch) diameter pellet. The pellets are then sintered at temperatures up to 1300 C and must not exhibit a significant degree of spalling or cracking. Pellets will therefore be tested to determine whether acceptable dry crushing strengths can be achieved.
Date: September 1, 1999
Creator: Kawatra, S.K.; Eisele, T.C.; Ripke, S.J. & Ramirez, G.
Partner: UNT Libraries Government Documents Department

Conversion of coal wastes into waste-cleaning materials. Quarterly progress report, January 1, 1997--March 31, 1997

Description: In this report, we present more detailed study on the microstructure and chemical compositions of the MCM-41 phase converted from Conemiaugh ash. The converted mesoporous material was analyzed by TEM and the Energy Dispersive X-ray Spectroscopy in the TEM. This part of the work was done in collaboration with Princeton University. The hexagonal mesoporous structure was found to have a pore size about 26. 1 {Angstrom} with a Si/Al mole ratio of 13.4. In addition, we studied the conversion of several other fly ashes with a wide range of chemical compositions to mesoporous aluminosilicates. It was found that both Eddystone and Goudey fly ashes can be successfully converted into MCM-41 aluminosilicates. Moreover, besides working on the synthesis of aluminosilicate mesoporous materials by fusion of fly ash and Ca(OH){sub 2} powder. The nitrogen adsorption/desorption isotherms and XRD patterns of this mesoporous material using Ca(OH){sub 2} were similar to those of mesoporous material using NaOH. It is not clear at the moment whether the mesoporous materials using Ca(OH){sub 2} contains any Ca or not. If it odes, then the mesoporous materials synthesized with Ca(OH){sub 2} may be very useful for SO{sub 2}/NO gas adsorption in pollutant emission control by the reaction between those gases with Ca.
Date: September 1, 1997
Creator: Shih, W.H.
Partner: UNT Libraries Government Documents Department

New approach to immobilization of coal-model compounds on silica using a calcium carboxylate linkage

Description: In an earlier report, the authors described efforts to study the hydrothermolysis of surface-immobilized coal model compounds by attaching 1-(4{prime}-hydroxyphenyl)-2-phenylethane to the surface of fumed silica via a Si-OAr linkage using procedures developed by Buchanan, Poutsma and coworkers and heating the resultant material (SiO-DPE) under D{sub 2} pressure. Despite the successes noted here, they sought to find a method for constructing links between silica and organic materials which might better survive hydroliquefaction conditions. Attachment of long-chain aliphatic carboxylic acids to silica through Mg{sup ++} or Ca{sup ++} ions is a patented method for silica flotation which they thought might be adapted to their purposes. This preprint is a preliminary report on the preparation, thermolysis and hydrothermolysis of materials believed to have the general structure, SiO{sup {minus}}Ca{sup ++}{sup {minus}}O{sub 2}CAr.
Date: December 31, 1995
Creator: Ramakrishnan, S.; Guthrie, R.D.; Britt, P.F.; Buchanan, A.C. III & Davis, B.H.
Partner: UNT Libraries Government Documents Department

The toxicity of X material

Description: This report addresses toxicity (largely chemical) of Manhattan Project materials from the point of worker protection. Known chemical toxicities of X material (uranium), nitrous fumes, fluorine, vanadium, magnesium, and lime are described followed by safe exposure levels, symptoms of exposure, and treatment recommendations. The report closes with an overview of general policy in a question and answer format.
Date: December 1943
Creator: Ferry, J. L.
Partner: UNT Libraries Government Documents Department

PREFERENTIAL RECYCLING/REJECTION IN CFBC/FBC SYSTEMS USING TRIBOELECTROSTATIC SEPARATION

Description: Circulating Fluidized Bed Combustion (CFBC) and Fluidized Bed Combustion (FBC) with recirculation are widely used technologies in the US for power generation. They have the advantage of fuel flexibility, and low NO{sub x} and SO{sub x} emissions. Typically, as partially combusted fuel is circulated in the system, only a split stream of this circulating stream is rejected, with the remainder recycled to the combustor. As a consequence, there is unburned carbon and partially used and valuable calcium hydroxide in the reject stream. If these useful materials in the reject stream can be recovered and sent back to the combustor, the efficiency of the system will be increased significantly and the equivalent emissions will be lower. This project studies an innovative concept to incorporate triboelectric separation into CFBC/FBC systems in order to preferentially split its recycle/reject streams based on material compositions of the particles. The objective is to answer whether useful constituents, like carbon, calcium carbonate and calcium hydroxide or oxide, can be selectively separated from combustion ash at elevated temperatures. Laboratory experimental studies are performed at temperatures from 25 C to 210 C,the data from which are presented in the form of recovery curves. These curves present quality-versus-quantity information useful for predicting the efficacy of triboelectric separation as applied to CFBC/FBC byproduct recycling and/or rejection.
Date: December 1, 2004
Creator: Ban, Heng & Stencel, John M.
Partner: UNT Libraries Government Documents Department

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Final technical report, September 1, 1991--August 31, 1992

Description: In this project, the ISGS is investigating the pelletization of fine coal with calcium hydroxide, a sulfur-capturing sorbent. The objective is to produce a readily-transportable fuel which will burn in compliance with the recently passed Clean Air Act Amendment (CAAA). To improve the economics of pelletizing, carbonation, or, the reaction of carbon dioxide with calcium hydroxide, which produces a binding matrix of calcium carbonate, is being investigated as a method of hardening pelletized coal fines. This year, pellets were produced from 28 {times} 0 coal fines collected from an Illinois preparation plant using a laboratory version of a California Pellet Mill (CPM), a commercially available pellet machine. The CPM effectively pelletized coal fines at the moisture content they were dewatered to at the plant. Carbonation nearly doubled the strength of pellets containing 10 wt % calcium hydroxide. Other results from this year`s work indicate that inclusion of calcium hydroxide into pellets resulted in chlorine capture of approximately 20 wt % for combustion tests conducted at both 850 and 1100{degrees}C. Arsenic emissions were reduced from near 38 wt% at 850 C to essentially nil with inclusion of 10 wt % calcium hydroxide into the pellets. At 110{degrees}C, arsenic emissions were reduced from about 90 wt % to about 15 wt %. Sodium emissions, however, increased with the addition of calcium hydroxide. At 850{degrees}C, sodium capture dropped from about 98 wt % to 73 wt % for pellets containing 10 wt % calcium hydroxide; at 1100{degrees}C, capture dropped from about 92 wt % to about 20 wt %.
Date: December 31, 1992
Creator: Rapp, D. M.; Lytle, J. M.; Hackley, K. C.; Strickland, R.; Berger, R. & Schanche, G.
Partner: UNT Libraries Government Documents Department

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Technical report, September 1, 1991--November 30, 1991

Description: Current coal mining and processing procedures produce a significant quanity of fine coal that is difficult to handle and transport. The objective of this work is to determine if these fines can be economically pelletized with calcium hydroxide, a sulfur capturing sorbent, to produce a clean-burning fuel for fluidized-bed combustors or stoker boilers. To harden these pellets, carbonation, which is the reaction of calcium hydroxide with carbon dioxide to produce a cementitious matrix of calcium carbonate, is being investigated. Previous research indicated that carbonation significantly improved compressive strength, impact and attrition resistance and ``weatherproofed`` pellets formed with sufficient calcium hydroxide (5 to 10% for minus 28 mesh coal fines).
Date: December 31, 1991
Creator: Rapp, D. M.
Partner: UNT Libraries Government Documents Department

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Technical report, December 1, 1992--February 28, 1993

Description: Pelletization of fine coal with calcium hydroxide, a sulfur capturing sorbent, represents a method to produce a fuel which will burn in compliance with the recently passed Clean Air Act Amendments (CAAA`s). To harden the pellets, the reaction of carbon dioxide with calcium hydroxide, referred to as carbonation, is being studied. Carbonation forms a bonding matrix of calcium carbonate. This is a two-year research program. This report covers the second quarter of the second year. Research is indicating that 5 to 10 wt% calcium hydroxide pellets can be produced via a roller-and-die pellet mill and air cured to achieve sufficient quality for handling and transportation. This quarter, 1/2 inch-diameter pellets containing 10% calcium hydroxide were demonstrated to gradually react with atmospheric carbon dioxide (3 days) while air drying to achieve compressive strengths equivalent to those attained for fully dried pellets which had been carbonated for one-hour with 100% commercial grade carbon dioxide. It was also demonstrated that an organic, adhesive binder, corn starch, can be very effective at producing strong pellets but drying is required before appreciable pellet strength is attained. For pellets containing 2 wt% corn starch, it was determined that less than 50% of the ultimate strength was achieved as the pellets were dried from 20 wt% to 5 wt% moisture. Strength improved considerably as the pellet moisture content was reduced below 5 wt%.
Date: May 1, 1993
Creator: Rapp, D.; Lytle, J.; Hackley, K.; Dagamac, M.; Berger, R. & Schanche, G.
Partner: UNT Libraries Government Documents Department

Combustion and emissions characterization of pelletized coal fuels. Technical report, December 1, 1992--February 28, 1993

Description: The aim of this project is to demonstrate that sorbent-containing coal pellets made from low grade coal or coal wastes are viable clean burning fuels, and to compare their performance with that of standard run-of-mine coal. Fuels to be investigated are: (a) carbonated pellets containing calcium hydroxide sorbent, (b) coal fines-limestone pellets with cornstarch as binder, (c) pellets made from preparation plant recovered coal containing limestone sorbent and gasification tar as binder, and (d) a standard run-of-mine Illinois seam coal. The fuels will be tested in a laboratory scale 411 diameter circulating fluidized bed combustor. Progress this quarter has centered on the development of a hydraulic press based pellet mill capable of the high compaction pressures necessary to produce the gasification tar containing pellets outlined in (c) above. Limited quantities of the pellets have been made, and the process is being fine tuned before proceeding into the production mode. Tests show that the moisture content of the coal is an important parameter that needs to be fixed within narrow limits for a given coal and binder combination to produce acceptable pellets. Combustion tests with these pellet fuels and the standard coal are scheduled for the next quarter.
Date: May 1, 1993
Creator: Rajan, S.
Partner: UNT Libraries Government Documents Department

Hydrogen and Nitrogen Control in Ladle and Casting Operations

Description: In recent years there has been an increasing demand to reduce and control the amount of dissolved gases in steel. Hydrogen and nitrogen are two of the most important gases which when dissolved in liquid steel affect its properties significantly. Several steelmaking additions have been investigated in this research for their effect on the hydrogen and nitrogen content of steels. It has been established that calcium hydroxide (hydrated lime) acts as a source of hydrogen. Carburizers, such as metallurgical coke, were found to result in no hydrogen pickup when added to liquid steel. Addition of petroleum coke, on the other hand, increased the hydrogen content of liquid steel. Ferroalloy such as medium carbon ferromanganese when added to the liquid iron was found to increase its nitrogen content, the increase being proportional to the amount of ferroalloy added. Similarly, addition of pitch coke, which had a significant nitrogen impurity, increased the nitrogen content of liquid iron. A mathematical model was developed to quantify the absorption of nitrogen and hydrogen from the air bubbles entrained during tapping of liquid steel. During the bottom stirring of liquid metal in a ladle, the inert gas escaping from the top displaces the slag layer and often forms an open eye. The absorption of atmospheric nitrogen through the spout eye was estimated for different slag thickness and gas flow rate. The ultimate goal of this research was to develop a comprehensive set of equations which could predict the nitrogen and hydrogen pickup from their various sources. Estimates of hydrogen and nitrogen pickup during the steel transfer operations such as tapping and ladle stirring and the predicted pickup from steelmaking additions were integrated into empirical equations. The comprehensive model is designed to predict the gas pickup under varying operating conditions such as the metal oxygen and sulfur ...
Date: January 15, 2005
Creator: Fruehan, Richard J. & Misra, Siddhartha
Partner: UNT Libraries Government Documents Department