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MAGNETO-CHEMICAL CHARACTER STUDIES OF NOVEL Fe CATALYSTS FOR COAL LIQUEFACTION

Description: FTIR studies on FeMoO{sub 3} catalysts indicate that samples prepared by the pyrolysis method produce smaller size particles and promote more interactions with the metal catalysts. In samples prepared by coprecipitation, it is likely that iron carbides might be forming, inhibiting carbonyl and carbonate formations. In Fe-Co-MoO{sub 3} catalysts exposure to syngas seems to replace MoO{sub 3} with CO, generating cobalt carbonyl structures. Even though iron with other supports is known to be a hydrocarbon selective catalyst, with MoO{sub 3} as a support, seems to be a poor syngas conversion catalyst, while cobalt with MoO{sub 3} as a support generate carbonyl-like structures. These findings suggest that Fe-CO-MoO{sub 3} is a better syngas conversion catalyst and pyrolysis method seems to promote these formations better than coprecipiation method. Our direct liquefaction experimental results support these findings.
Date: August 16, 2001
Partner: UNT Libraries Government Documents Department

Nano-Carbides and the Strength of Steels as Assessed by Electrical Resistivity Studies

Description: The work of Frommeyer on electrical conductivity measurements in pearlitic steels is reviewed to provide insight into microstructures developed during wi wire drawing. Electrical re conductivity measurements were made as a function of drawing strain (up to {var_epsilon} = 6.0) for wires with strength exceeding 3500MPa. The results show that electrical conductivity increases during wire wire-drawing to a maximum value, then decreases with further deformation finally reaching a steady state value that is equal to the original conductivity. The initial increase is the result of pearlite plate orientation in the direction of wire wire-drawing, which makes the path of conduction through the ferrite plates more accessible. At a critical strain the cementite plates begin to fragment and the electrical conductivity decreases to a steady state value that is the same as that observed prior to wire drawing. With increasing strain, the cementite particles are refined and the strength increases due to the reduction in inter inter-particle spacing. It is concluded that the electrical conductivity of the wires is solely dependent on the amount of iron carbides provided they are randomly distributed as plates or as particles. An estimate was made that indicates the carbide particle size is approximately 3-5 nm in the steady state range of electrical conductivity.
Date: January 29, 2006
Creator: Lesuer, D; Frommeyer, G; Sherby, O & Syn, C
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch Wax Products from Ultrafine Iron Catalyst Particles

Description: In the previous reporting period, modifications were completed for integrating a continuous wax filtration system for a 4 liter slurry bubble column reactor. During the current reporting period, a shakedown of the system was completed. Several problems were encountered with the progressive cavity pump used to circulate the wax/catalyst slurry though the cross-flow filter element and reactor. During the activation of the catalyst with elevated temperature (> 270 C) the elastomer pump stator released sulfur thereby totally deactivating the iron-based catalyst. Difficulties in maintaining an acceptable leak rate from the pump seal and stator housing were also encountered. Consequently, the system leak rate exceeded the expected production rate of wax; therefore, no online filtration could be accomplished. Work continued regarding the characterization of ultra-fine catalyst structures. The effect of carbidation on the morphology of iron hydroxide oxide particles was the focus of the study during this reporting period. Oxidation of Fe (II) sulfate results in predominantly {gamma}-FeOOH particles which have a rod-shaped (nano-needles) crystalline structure. Carbidation of the prepared {gamma}-FeOOH with CO at atmospheric pressure produced iron carbides with spherical layered structure. HRTEM and EDS analysis revealed that carbidation of {gamma}-FeOOH particles changes the initial nano-needles morphology and generates ultrafine carbide particles with irregular spherical shape.
Date: September 30, 2006
Creator: Neathery, James K.; Jacobs, Gary; Sarkar, Amitava; Crawford, Adam & Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

TECHNOLOGY DEVELOPMENT FOR IRON AND CONBALT FISCHER-TROPSCH CATALYSTS

Description: The use of alkali promoters has been widely practiced. However, data to compare various promoters is limited for the iron-based catalysts and much of the available data were obtained at low pressure or under a variety of reaction conditions. The importance of the alkali promoter in determining catalytic activity, stability and selectivity merits a comparison of the promoters under suitable reaction conditions. The present study utilizes medium pressure synthesis conditions to compare the alkali promoters under the same reaction conditions and over a wide range of conversion levels. Iron-based Fischer-Tropsch (FT) catalysts undergo a series of phase transformations during activation and use. Activation with carbon monoxide or syngas typically results in the conversion of Fe{sub 2}O{sub 3} to Fe{sub 3}O{sub 4} and ultimately to one or more carbides. During FT synthesis, iron carbides can be oxidized to Fe{sub 3}O{sub 4} if the H{sub 2}O/H{sub 2} or CO{sub 2}/CO ratios are high enough. There has been considerable debate about the active phase of the FT synthesis. Some studies have indicated an active oxide species while most have supported a carbide species. Moessbauer spectroscopy has proven to be an effective technique for the analysis of iron-based FT catalysts. In situ Moessbauer studies have been reported; however, these studies have been performed at low pressure and low conversions. Studies performed at industrially relevant conditions have generally involved removing the catalyst from the reactor followed by passivation which, if not performed properly, will oxidize the catalyst. Herein are reported the Moessbauer results obtained on an unpromoted precipitated iron catalyst that was activated and reacted in a slurry phase, continuous stirred tank reactor at high conversion and under industrially relevant conditions.
Date: October 1, 2000
Creator: Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

RESULTS OF CHARACTERIZATION TESTS OF THE SURFACES OF A COMMERCIALLY CARBURIZED AUSTENITIC STAINLESS STEEL

Description: A commercial surface carburization treatment that shows promise for hardening the surfaces of the stainless steel target vessel of the Spallation Neutron Source against cavitation erosion and pitting caused by the action of pulsed pressure waves in the liquid mercury target has been investigated. To verify promotional claims for the treatment and to uncover any factors that might be of concern for the integrity of a carburized target vessel, some characterization tests of the nature of the surface layers of carburized austenitic 316LN stainless steel were conducted. The findings support most of the claims. The carburized layer is about 35 {micro}m thick. Its indentation hardness is about five times larger than that of the substrate steel and declines rapidly with depth into the layer. The surface is distorted by the treatment, and the austenite lattice is enlarged. The corrosion resistance of the carburized layer in an acid medium is greater than that for untreated austenite. The layer is not brittle; it is plastically deformable and is quite resistant to cracking during straining. Contrary to the provider's assertations, the maximum carbon content of the layer is much less than 6-7 wt% carbon, and the carbon is not simply contained in supersaturated solid solution; some of it is present in a previously unreported iron carbide phase located at the very surface. Large variations were found in the thickness of the layer, and they signify that controls may be needed to ensure a uniform thickness for treatment of the SNS target vessel. Inclusion stringers and {delta}-ferrite phase embraced in the treated layer are less resistant to chemical attack than the treated austenite. From a cavitation pitting perspective under SNS bombardment, such non-austenitic phases may provide preferential sites for pitting. The shallow depth of the hardened layer will require use of protection measures to ...
Date: January 7, 2004
Creator: Farrell, K
Partner: UNT Libraries Government Documents Department

AISI/DOE Technology Roadmap Program: Behavior of Phosphorus in DRI/HBI During Electric Furnace Steelmaking

Description: Many common scrap substitutes such as direct reduced iron pellets (DRI), hot briquetted iron (HBI), iron carbide, etc., contain significantly higher levels of phosphorus steelmaking for the production of higher quality steels, control of phosphorus levels in the metal will become a concern. This study has developed a more complete understanding of the behavior of phosphorus in DRI during EAF steelmaking, through a thorough investigation of the kinetics and thermodynamics of phosphorus transfer in the EAF based upon laboratory and plant experiments and trials. Laboratory experiments have shown that phosphorus mass transfer between oxide and metallic phases within commercial direct reduced iron pellets occurs rapidly upon melting according to the local equilibrium for these phases. Laboratory kinetic experiments indicate that under certain conditions, phosphorus mass transfer between slag and metal is influenced by dynamic phenomena, which affect the mass transfer coefficient for the reaction and/or the slag metal interfacial area. Plant trials were conducted to directly evaluate the conditions of mass transfer in the electric furnace and to determine the effects of different scrap substitute materials upon the slag chemistry, the behavior of phosphorus in the steel, and upon furnace yield. The data from these trials were also used to develop empirical models for the slag chemistry and furnace temperature as functions of time during a single heat. The laboratory and plant data were used to develop a numerical process model to describe phosphorus transfer in the EAF
Date: October 5, 2001
Creator: Frueham, Richard J. & Manning, Christopher P.
Partner: UNT Libraries Government Documents Department

Moessbauer spectroscopy studies of iron-catalysts used in Fischer-Tropsch (FT) processes. Quarterly technical progress report, April--June, 1994

Description: Moessbauer spectroscopy investigations were carried out on 16 iron-based catalysts during the period under review. A set of 10 samples subjected to different pretreatments and Fischer-Tropsch synthesis were investigated to understand the effect of reduction in different gas atmospheres on the iron phases formed. Another set of 5 catalysts pretreated in CO and subjected to Fischer-Tropsch synthesis using two kinds of wax viz., (a) a low molecular wt. wax and (b) heavy wax were also studied. Although it is difficult to draw any definite conclusions from the data, some plausible trends are noticed: (1) pretreatment of a catalyst in H{sub 2} leads to the formation of {var_epsilon}-carbide; (2) pretreatment of a catalyst in H{sub 2}/CO leads to the formation of {chi}-carbide; (3) reduction of UCI-1185-149-2ND catalyst in CO leads to the formation of {chi}-carbide; and (4) reduction of DOE catalysts in CO leads to the formation of {var_epsilon}-carbide. Data are presented on the phases found in the various catalysts.
Date: December 31, 1994
Creator: Huffman, G.P. & Rao, K.R.P.M.
Partner: UNT Libraries Government Documents Department

TECHNOLOGY DEVELOPMENT FOR IRON AND COBALT FISCHER-TROPSCH CATALYSTS

Description: The impact of activation procedure on the phase composition of precipitated iron Fischer-Tropsch (FT) catalysts has been studied. Catalyst samples taken during activation and FT synthesis have been characterized by Moessbauer spectroscopy. Formation of iron carbide is necessary for high FT activity. Hydrogen activation of precipitated iron catalysts results in reduction to predominantly metallic iron and Fe{sub 3}O{sub 4}. Metallic iron is not stable under FT 3 4 conditions and is rapidly converted to {epsilon}{prime}-Fe{sub 2.2}C. Activation with carbon monoxide or syngas 2.2 with low hydrogen partial pressure reduces catalysts to {chi}-Fe{sub 5}C{sub 2} and a small amount of 5 2 superparamagnetic carbide. Exposure to FT conditions partially oxidizes iron carbide to Fe{sub 3}O{sub 4}; however, catalysts promoted with potassium or potassium and copper maintain a constant carbide content and activity after the initial oxidation. An unpromoted iron catalyst which was activated with carbon monoxide to produce 94% {chi}-Fe{sub 5}C{sub 2}, deactivated rapidly as the carbide was oxidized to Fe{sub 3}O{sub 4}. No difference in activity, stability or deactivation rate was found for {chi}-Fe{sub 5}C{sub 2} and {epsilon}{prime}-Fe{sub 2.2}C.
Date: April 30, 1999
Creator: Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

Moessbauer spectroscopy studies of iron-catalysts used in Fischer-Tropsch (FT) processes. Quarterly technical progress report, January--March, 1994

Description: The objective of this project is to carry out a Moessbauer spectroscopy study of Iron-based catalysts to identify iron phases present and correlate with water gas shift and FT activities. A total of 15 catalysts were evaluated so far. Results are presented on the amounts in each catalyst of the following phases: superparamagnetic phase, hematite ({alpha}-Fe{sub 2}O{sub 3}), magnetite (Fe{sub 3}O{sub 4}), Chi-carbide phase ({chi}-Fe{sub 5}C{sub 2}), and an epsilon-carbide phase ({var_epsilon}-Fe{sub 2.2}C).
Date: December 1994
Creator: Huffman, G. P. & Rao, K. R. P. M.
Partner: UNT Libraries Government Documents Department

SEPARATION OF FISCHER-TROPSCH WAX PRODUCTS FROM ULTRAFINE IRON CATALYST PARTICLES

Description: In this reporting period, a fundamental filtration study was continued to investigate the separation of Fischer-Tropsch Synthesis (FTS) liquids from iron-based catalyst particles. The overall focus of the program is with slurry-phase FTS in slurry bubble column reactor systems. Hydrocarbon products must be separated from catalyst particles before being removed from the reactor system. An efficient wax product/catalyst separation system is a key factor for optimizing operating costs for iron-based slurry-phase FTS. Previous work has focused on catalyst particle attrition and the formation of ultra-fine iron carbide and/or carbon particles. With the current study, we are investigating how the filtration properties are affected by these chemical and physical changes of the catalyst slurry during activation/synthesis. The shakedown phase of the pilot-scale filtration platform was completed at the end of the last reporting period. A study of various molecular weight waxes was initiated to determine the effect of wax physical properties on the permeation rate without catalyst present. As expected, the permeation flux was inversely proportional to the nominal average molecular weight of the polyethylene wax. Even without catalyst particles present in the filtrate, the filtration membranes experience fouling during an induction period on the order of days on-line. Another long-term filtration test was initiated using a batch of iron catalyst that was previously activated with CO to form iron carbide in a separate continuous stirred tank reactor (CSTR) system. The permeation flux stabilized more rapidly than that experienced with unactivated catalyst tests.
Date: September 30, 2004
Creator: Neathery, James K.; Jacobs, Gary & Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

SEPARATION OF FISCHER-TROPSCH WAX PRODUCTS FROM ULTRAFINE IRON CATALYST PARTICLES

Description: In this reporting period, a fundamental filtration study was started to investigate the separation of Fischer-Tropsch Synthesis (FTS) liquids from iron-based catalyst particles. Slurry-phase FTS in slurry bubble column reactor systems is the preferred mode of production since the reaction is highly exothermic. Consequently, heavy wax products must be separated from catalyst particles before being removed from the reactor system. Achieving an efficient wax product separation from iron-based catalysts is one of the most challenging technical problems associated with slurry-phase FTS. The separation problem is further compounded by catalyst particle attrition and the formation of ultra-fine iron carbide and/or carbon particles. Existing pilot-scale equipment was modified to include a filtration test apparatus. After undergoing an extensive plant shakedown period, filtration tests with cross-flow filter modules using simulant FTS wax slurry were conducted. The focus of these early tests was to find adequate mixtures of polyethylene wax to simulate FTS wax. Catalyst particle size analysis techniques were also developed. Initial analyses of the slurry and filter permeate particles will be used by the research team to design improved filter media and cleaning strategies.
Date: March 31, 2004
Creator: Neathery, James K.; Jacobs, Gary & Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch Wax Products from Ultrafine Iron Catalyst Particles

Description: In this reporting period, a study of ultra-fine iron catalyst filtration was initiated to study the behavior of ultra-fine particles during the separation of Fischer-Tropsch Synthesis (FTS) liquids filtration. The overall focus of the program is with slurry-phase FTS in slurry bubble column reactor systems. Hydrocarbon products must be separated from catalyst particles before being removed from the reactor system. An efficient wax product/catalyst separation system is a key factor for optimizing operating costs for iron-based slurry-phase FTS. Previous work has focused on catalyst particle attrition and the formation of ultra-fine iron carbide and/or carbon particles. With the current study, we are investigating how the filtration properties are affected by these chemical and physical changes of the catalyst slurry during activation/synthesis. The change of particle size during the slurry-phase FTS has monitored by withdrawing catalyst sample at different TOS. The measurement of dimension of the HRTEM images of samples showed a tremendous growth of the particles. Carbon rims of thickness 3-6 nm around the particles were observed. This growth in particle size was not due to carbon deposition on the catalyst. A conceptual design and operating philosophy was developed for an integrated wax filtration system for a 4 liter slurry bubble column reactor to be used in Phase II of this research program. The system will utilize a primary inertial hydroclone followed by a Pall Accusep cross-flow membrane. Provisions for cleaned permeate back-pulsing will be included to as a flux maintenance measure.
Date: September 30, 2005
Creator: Neathery, James K.; Jacobs, Gary; Sarkar, Amitava & Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

SEPARATION OF FISCHER-TROPSCH WAX PRODUCTS FROM ULTRAFINE IRON CATALYST PARTICLES

Description: In this reporting period, a fundamental filtration study was continued to investigate the separation of Fischer-Tropsch Synthesis (FTS) liquids from iron-based catalyst particles. The overall focus of the program is with slurry-phase FTS in slurry bubble column reactor systems. Hydrocarbon products must be separated from catalyst particles before being removed from the reactor system. An efficient wax product/catalyst separation system is a key factor for optimizing operating costs for iron-based slurry-phase FTS. Previous work has focused on catalyst particle attrition and the formation of ultra-fine iron carbide and/or carbon particles. With the current study, we are investigating how the filtration properties are affected by these chemical and physical changes of the catalyst slurry during activation/synthesis. In this reporting period, a series of crossflow filtration experiments were initiated to study the effect of olefins and oxygenates on the filtration flux and membrane performance. Iron-based FTS reactor waxes contain a significant amount of oxygenates, depending on the catalyst formulation and operating conditions. Mono-olefins and aliphatic alcohols were doped into an activated iron catalyst slurry (with Polywax) to test their influence on filtration properties. The olefins were varied from 5 to 25 wt% and oxygenates from 6 to 17 wt% to simulate a range of reactor slurries reported in the literature. The addition of an alcohol (1-dodecanol) was found to decrease the permeation rate while the olefin added (1-hexadecene) had no effect on the permeation rate. A passive flux maintenance technique was tested that can temporarily increase the permeate rate for 24 hours.
Date: March 31, 2005
Creator: Neathery, James K.; Jacobs, Gary & Davis, Burtron H.
Partner: UNT Libraries Government Documents Department

Synthesis of single phase {alpha}-Fe, Fe{sub 3}C and Fe{sub 7}C{sub 3} nano-particles by CO{sub 2} laser pyrolysis technique. Quarterly progress report, January--March, 1992

Description: Iron-containing catalysts have been known to be useful in assisting the Fischer-Tropsch (FT) reaction for synthesizing hydrocarbons. However, it has been well recognized that iron catalyst are not stable during the reaction but converted into iron carbides. It is thus important to understand the role of the iron carbides in the catalytic reaction of the FT-synthesis. It has been found difficult to produce iron carbide nano-particles as a single phase, because iron carbide phases are only metastable under 1 atm pressure. Iron carbide bulk particles prepared so far are often contaminated with metallic iron, iron oxides and free carbon. In this study, we investigate the synthesis of iron carbide nano-particles using CO{sub 2} laser pyrolysis technique. We show that this technique is successful in synthesizing {alpha}-Fe, Fe{sub 3}C and Fe{sub 7}C{sub 3} nano-particles in their single phase with sizes in the range of 5--20nm. In particular, we have produced for the first time the Fe{sub 7}C{sub 3} which has been known to exist but unable to be produced as a single phase. Furthermore, it is interesting that Fe{sub 5}C{sub 2} which has carbon and iron ratio between Fe{sub 3}C and Fe{sub 7}C{sub 3}, is not seen in any run of our synthesis.
Date: July 1, 1992
Creator: Eklund, P. C. & Bi, X. X.
Partner: UNT Libraries Government Documents Department

Effect of point defects on mechanical properties of metals. Technical progress report

Description: The major research effort was on iron. The recovery of the electron irradiation effect was studied in pure iron and iron-carbon alloys. This investigation resulted in several new findings in addition to the confirmation of two assumptions used in the interpretation of the mechanical effects of electron irradiation on high-purity iron single crystals. The irradiation softening effect was studied in single crystals oriented for the (011) slip and polycrystalline specimens. Then, a striking orientation effect was discovered and a large irradiation softening was found in single crystal specimens oriented for the hard (121) slip. In this oriertation, more than 60% of the yield stress is reduced by electron irradiation; thereby, the hardest oriertation becomes the softest orientation following electron irradiation. The solution softening and hardening effects of carbon atoms were investigated using highpurity iron single crystills similar to those used in the irradiationsoftening study. The general behavior of the softening and hardening was in good agreement with a proposed theory based on the irradiation- softening experiments. (auth)
Date: January 1, 1973
Creator: Meshii, M
Partner: UNT Libraries Government Documents Department

The economical production of alcohol fuels from coal-derived synthesis gas. Quarterly technical progress report number 12, July 1--September 30, 1994

Description: Both plug-flow microreactor systems at WVU are now functioning. Screening runs on these systems were started using carbide and nitride catalysts first, to avoid any question of contamination of the system with sulfur. The carbide and nitride catalysts are characterized by high activity but low selectivity towards alcohols. The Chevrel-phase catalysts tested have much lower activities but may be more selective to alcohols. Catalyst synthesis procedures are attempting to offset this tendency, and also to characterize and prepare sulfide catalyst by other approaches. At UCC and P, test runs on the reactor system have commenced. Higher alcohols up to butanol were observed and identified at high temperatures. Modeling studies have concentrated on the catalytic membrane reactor. The topical report, originally submitted last quarter, was revised after some errors were found. This report includes the design and economics for the seven cases discussed in previous quarterly reports. In the topical report, it is shown that a judicious choice of coal:natural gas feed ratio to the alcohol synthesis process allows the Shell Gasifier to be nearly competitive with natural gas priced at of $3.00/MMBtu. The advantage of the Shell Gasifier over the Texaco Gasifier is that the former produces a syngas with a lower H{sub 2}:CO ratio. When the feed to the process is coal only, there is no difference in the projected economics that would favor one gasifier over the other. The potential of co-generation of electric power with high alcohol fuel additives has been investigated. Preliminary results have revealed that a once-through alcohol synthesis process with minimal gas clean-up may provide an attractive alternative to current designs given the prevailing economic status of IGCC units.
Date: October 1, 1994
Partner: UNT Libraries Government Documents Department

Technology development for iron Fischer-Tropsch catalysis. Quarterly technical progress report, October--December, 1994

Description: Fischer-Tropsch catalysts must undergo a pretreatment in order to be active. As part of the authors comprehensive study to maximize the activity of iron based precipitated Fischer-Tropsch catalysts, they are currently attempting to optimize the activation procedure. Although they are able to achieve high activity using CO pretreatment, the catalysts tend to deactivate suddenly and rapidly after 500 hr of synthesis. Kolbel reports high CO conversion comparable to these results at a lower gas flow (2.4 vs. 3.4 nL/hr-g(Fe)); however, he achieved greater stability with conversions reported to be 90% after 1,400 hrs. One possibility for Kolbel`s higher stability could be due to the activation procedure. Herein are reported the initial results of a study to optimize the catalyst composition and the operating conditions for the iron based slurry phase Fischer-Tropsch synthesis when synthesis gas activation is utilized.
Date: December 31, 1994
Partner: UNT Libraries Government Documents Department

Evaluating mechanical properties of thin layers using nanoindentation and finite-element modeling: Implanted metals and deposited layers

Description: We present a methodology based on finite-element modeling of nanoindentation data to extract reliable and accurate mechanical properties from thin, hard films and surface-modified layers on softer substrates. The method deduces the yield stress, Young`s modulus, and hardness from indentations as deep as 50% of the layer thickness.
Date: December 31, 1996
Creator: Knapp, J.A.; Follstaedt, D.M. & Barbour, J.C.
Partner: UNT Libraries Government Documents Department

Carbon formation and metal dusting in advanced coal gasification processes

Description: The product gases generated by coal gasification systems contain high concentrations of CO and, characteristically, have relatively high carbon activities. Accordingly, carbon deposition and metal dusting can potentially degrade the operation of such gasifier systems. Therefore, the product gas compositions of eight representative gasifier systems were examined with respect to the carbon activity of the gases at temperatures ranging from 480 to 1,090 C. Phase stability calculations indicated that Fe{sub 3}C is stable only under very limited thermodynamic conditions and with certain kinetic assumptions and that FeO and Fe{sub 0.877}S tend to form instead of the carbide. As formation of Fe{sub 3}C is a necessary step in the metal dusting of steels, there are numerous gasifier environments where this type of carbon-related degradation will not occur, particularly under conditions associated with higher oxygen and sulfur activities. These calculations also indicated that the removal of H{sub 2}S by a hot-gas cleanup system may have less effect on the formation of Fe{sub 3}C in air-blown gasifier environments, where the iron oxide phase can exist and is unaffected by the removal of sulfur, than in oxygen-blown systems, where iron sulfide provides the only potential barrier to Fe{sub 3}C formation. Use of carbon- and/or low-alloy steels dictates that the process gas composition be such that Fe{sub 3}C cannot form if the potential for metal dusting is to be eliminated. Alternatively, process modifications could include the reintroduction of hydrogen sulfide, cooling the gas to perhaps as low as 400 C and/or steam injection. If higher-alloy steels are used, a hydrogen sulfide-free gas may be processed without concern about carbon deposition and metal dusting.
Date: February 1, 1997
Creator: DeVan, J.H.; Tortorelli, P.F.; Judkins, R.R. & Wright, I.G.
Partner: UNT Libraries Government Documents Department

Carbon formation and metal dusting in hot-gas cleanup systems of coal gasifiers

Description: The product gas resulting from the partial oxidation of Carboniferous materials in a gasifier is typically characterized by high carbon and sulfur, but low oxygen, activities and, consequently, severe degradation of the structural and functional materials can occur. The objective of this task was to establish the potential risks of carbon deposition and metal dusting in advanced coal gasification processes by examining the current state of knowledge regarding these phenomena, making appropriate thermochemical calculations for representative coal gasifiers, and addressing possible mitigation methods. The paper discusses carbon activities, iron-based phase stabilities, steam injection, conditions that influence kinetics of carbon deposition, and influence of system operating parameters on carbon deposition and metal dusting.
Date: November 1, 1995
Creator: Judkins, R.R.; Tortorelli, P.F.; Judkins, R.R.; DeVan, J.H. & Wright, I.G.
Partner: UNT Libraries Government Documents Department

The role of catalyst activation on the activity and attrition of precipitated iron Fischer-Tropsch catalysts

Description: The results of this work indicate that magnetite is not catalytically active for Fischer-Tropsch Synthesis (FTS) in precipitated, unsupported iron catalysts, but the formation of the carbide phase is necessary to obtain FTS activity. The transformation of magnetite to carbide, though essential to obtain FTS activity, also causes the catalyst to break down. This can lead to severe problems during operation in a commercial slurry phase reactor. The results presented here imply that activation and attrition are simultaneous and complementary processes. In another study, we show that the catalyst can also under go attrition on a micron scale which is caused by lack of strength of the forces binding the catalyst primary particles in the agglomerates. Both these processes can make wax separation and product recovery extremely difficult. In this study, we have also shown that H{sub 2} reduction of this catalyst to metallic iron is detrimental to subsequent catalyst activity and causes a loss of surface area due to sintering of the iron crystallites. Reduction to metallic Fe also causes impurities such as S to segregate to the surface causing a complete loss of FTS activity. It has been shown that even submonolayer amounts of S can cause a dramatic decrease in FTS activity, hence reduction to metallic Fe should be avoided during activation of these catalysts. We have shown, however, that a mild H{sub 2} reduction to magnetite does not lead to S segregation to the surface, and is therefore acceptable.
Date: December 31, 1995
Creator: Datye, A.K.; Shroff, M.D.; Harrington, M.S.; Coulter, K.E.; Sault, A.G. & Jackson, N.B.
Partner: UNT Libraries Government Documents Department

Moessbauer spectroscopy studies of iron-catalysts used in Fischer-Tropsch (FT) processes. Quarterly technical progress report, October--December, 1994

Description: Moessbauer spectroscopy investigations on 6 iron-based catalysts and analysis of the XAFS measurements done earlier on 23 catalysts , were carried out during the period under review. A set of 4 catalysts subjected to CO pretreatment and Fischer-Tropsch synthesis were sent by Robert J. Gormley, PETC, Dept. of Energy, to understand the effect of reduction on the iron phases formed. A catalyst activated in CO and subjected to Fischer-Tropsch synthesis and extracted directly into an ``O`` ring sealed Moessbauer absorber holder under argon atmosphere and another catalyst from the same run but exposed to air were sent by Dr. Burt Davis, CAER, Univ. of Kentucky, for identifying the iron phases present and to monitor the differences, if any, between two catalysts. Results to date are presented.
Date: December 31, 1994
Creator: Huffman, G.P. & Rao, K.R.P.M.
Partner: UNT Libraries Government Documents Department