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Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

Description: Immobilization of toxic and radioactive metals in the vadose zone by In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory and field studies have shown that Cr(VI) can be effectively immobilized by treatment with dilute gaseous H2S. The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to assess the long-term effectiveness of the technology and to optimize the remediation system.
Date: January 11, 2004
Creator: Deng, Baolin; Thornton, Edward; Cantrell, Kirk; Olsen, Khris & Amonette, James
Partner: UNT Libraries Government Documents Department

Removal of H2S and SO2 by CaCO3-Based Sorbents at High Pressure

Description: The theoretical and experimental investigation of the mechanism of SO2 and H2S removal by CaCO3 -based sorbents (limestones and dolomites) in pressurized uidized-bed coal combustors (PFBC) and high pressure gasi#12;ers, respectively, is the main objective of this study. It is planned to carry out reactivity evolution experiments under simulated high pressure conditions or in high pressure thermogravimetric and, if needed, uidized- bed reactor (high pressure) arrangements. The pore structure of fresh, heat-treated, and half-calcined solids (dolomites) will be analyzed using a variety of methods. Our work will focus on limestones and dolomites whose reaction with SO2 or H2S under atmospheric conditions has been studied by us or other research groups in past studies. Several theoret- ical tools will be employed to analyze the obtained experimental data including a variable di#11;usivity shrinking-core model and models for di#11;usion, reaction, and structure evolution in chemically reacting porous solids. During the six months of this reporting period, work was primarily done on the study of the behavior of the sul#12;dation of limestones under sequential calcination conditions in the presence of small amounts of oxygen and the development of a stochastic simulation code for determining the extent of pore volume trapping (formation of inaccessible pore space) in gas-solid reactions accompanied by pore volume reduction such as the sulfation and sul#12;dation of calcined limestones and dolomites. The incentive for carrying out sul#12;dation experiments in the presence of oxygen was provided by the observation that some sul#12;dation experiments that were conducted as oxygen was accidentally leaking into the feed mixture of the reactor showed completely di#11;erent behavior from that obtained in the absence of oxygen. Experiments were carried out in the thermogravimetric analysis system that we developed for studying gas-solid reactions at atmospheric or subambient pressures. The two CaCO3 solids (Greer limestone and Iceland spar) that we ...
Date: February 1, 1998
Creator: Sotirchos, Stratis V.
Partner: UNT Libraries Government Documents Department

Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

Description: Immobilization of toxic and radioactive metals (e.g., Cr, Tc, and U) in the vadose zone by in situ gaseous reduction using hydrogen sulfide (H2S) is a promising technology the U.S. Department of Energy (DOE) is developing for soil remediation. Earlier laboratory studies have shown that Cr(VI) in a number of soil samples can be effectively immobilized by treatment with dilute gaseous H2S. A field test has also been completed that resulted in 70% immobilization of Cr(VI). The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to assess the long-term effectiveness of the technology and to optimize the remediation system.
Date: June 1, 2001
Creator: Deng, B.; Thornton, Edward C.; Olsen, Khris B.; Cantrell, Kirk J. & Amonette, James E.
Partner: UNT Libraries Government Documents Department

PGandE Geysers Retrofit Project, Units 1-12: Final Report, Technical Data, Volume I - Sections 1-8

Description: The purpose of this work is to demonstrate whether there is a cost benefit to Pacific Gas and Electric Company in replacing the present iron catalyst/caustic/peroxide system used in the direct contact condenser units with an alternative approach using surface condensers and the Stretford System for hydrogen sulfide abatement.
Date: August 24, 1979
Partner: UNT Libraries Government Documents Department

H{sub2}S Abatement at The Geysers

Description: This paper discusses the efforts by the inter-departmental task forces which have been formed by PG and E to improve and expedite the development, design, installation, and modifications to hydrogen sulfide abatement and abatement-related systems for The Geysers power plants.
Date: December 1, 1980
Creator: Ziomek, N.L.
Partner: UNT Libraries Government Documents Department

Novel Composite Hydrogen-Permeable Membranes for Nonthermal Plasma Reactors for the Decomposition of Hydrogen Sulfide

Description: The goal of this experimental project was to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a nonthermal plasma and to recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), but it was not achieved at the moderate pressure conditions used in this study. However, H{sub 2}S was successfully decomposed at energy efficiencies higher than any other reports for the high H{sub 2}S concentration and moderate pressures (corresponding to high reactor throughputs) used in this study.
Date: September 30, 2007
Creator: Argyle, Morris; Ackerman, John; Muknahallipatna, Suresh; Hamann, Jerry; Legowski, Stanislaw; Zhao, Gui-Bing et al.
Partner: UNT Libraries Government Documents Department

Advanced sulfur control concepts for hot gas desulfurization technology

Description: The objective of this project is to develop a hot-gas desulfurization process scheme for control of H{sub 2}S in HTHP coal gas that can be more simply and economically integrated with known regenerable sorbents in DOE/METC-sponsored work than current leading hot-gas desulfurization technologies. In addition to being more economical, the process scheme to be developed must yield an elemental sulfur byproduct.
Date: September 1, 1998
Partner: UNT Libraries Government Documents Department

Advanced sulfur control concepts for hot gas desulfurization technology

Description: The objective of this project is to develop a hot-gas desulfurization process scheme for control of H{sub 2}S in HTHP coal gas that can be more simply and economically integrated with known regenerable sorbents in DOE/METC-sponsored work than current leading hot-gas desulfurization technologies. In addition to being more economical, the process scheme to be developed must yield an elemental sulfur byproduct.
Date: September 1, 1998
Partner: UNT Libraries Government Documents Department

High Temperature Electrochemical Polishing of H(2)S from Coal Gasification Process Streams.

Description: An advanced process for the separation of hydrogen sulfide from coal gasification streams through an electrochemical membrane is being perfected. H{sub 2}S is removed from a synthetic gas stream, split into hydrogen, which enriches the exiting syngas, and sulfur, which is condensed downstream from an inert sweep gas stream. The process allows for continuous removal of H{sub 2}S without cooling the gas stream while allowing negligible pressure loss through the separator. Moreover, the process is economically attractive due to the elimination of the need for a Claus process for sulfur recovery. To this extent the project presents a novel concept for improving utilization of coal for more efficient power generation.
Date: December 31, 1997
Creator: Winnick, J.
Partner: UNT Libraries Government Documents Department

High Temperature Electrochemical Polishing of H(2)S from Coal Gasification. Quarterly progress report, April 1-June 30, 1997

Description: An advanced process for the separation of hydrogen sulfide from coal gasification streams through an electrochemical membrane is being perfected. H{sub 2}S is removed from a synthetic gas stream, split into hydrogen, which enriches the exiting syngas, and sulfur, which is condensed downstream from an inert sweep gas stream. The process allows for continuous removal of H{sub 2}S without cooling the gas stream while allowing negligible pressure loss through the separator. Moreover, the process is economically attractive due to the elimination of the need for a Claus process for sulfur recovery. To this extent the project presents a novel concept for improving utilization of coal for more efficient power generation.
Date: December 31, 1997
Creator: Winnick, J.
Partner: UNT Libraries Government Documents Department

New technology for sulfide reduction and increased oil recovery. First quarter progress report, June 6, 1997--June 5, 1998

Description: Project work was initiated by Geo-Microbial Technologies, Inc. (GMT), Ochelata, Oklahoma for Contract Number DE-FG01-97EE15659 on June 18, 1997. The purpose of this project is to demonstrate reduction of sulfide contamination, as well as possible improvement of production in oil and gas production systems. This will be accomplished by application of the BioCompetitive Exclusion (BCX) process developed by GMT. A broad spectrum of well types and geographical locations is anticipated. The BCX process is designed to manipulate indigenous reservoir bacteria with the addition of synergistic inorganic chemical formulae. These treatments will stimulate growth of beneficial microbes, while suppressing metabolic activity of sulfate reducing bacteria, the primary source of harmful sulfide production.
Date: September 20, 1997
Creator: Hitzman, D.C.
Partner: UNT Libraries Government Documents Department

Low-quality natural gas sulfur removal/recovery

Description: A significant fraction of U.S. natural gas reserves are subquality due to the presence of acid gases and nitrogen; 13% of existing reserves (19 trillion cubic feed) may be contaminated with hydrogen sulfide. For natural gas to be useful as fuel and feedstock, this hydrogen sulfide has to be removed to the pipeline specification of 4 ppm. The technology used to achieve these specifications has been amine, or similar chemical or physical solvent, absorption. Although mature and widely used in the gas industry, absorption processes are capital and energy-intensive and require constant supervision for proper operation. This makes these processes unsuitable for treating gas at low throughput, in remote locations, or with a high concentration of acid gases. The U.S. Department of Energy, recognizes that exploitation of smaller, more sub-quality resources will be necessary to meet demand as the large gas fields in the U.S. are depleted. In response to this need, Membrane Technology and Research, Inc. (MTR) has developed membranes and a membrane process for removing hydrogen sulfide from natural gas. During this project, high-performance polymeric thin-film composite membranes were brought from the research stage to field testing. The membranes have hydrogen sulfide/methane selectivities in the range 35 to 60, depending on the feed conditions, and have been scaled up to commercial-scale production. A large number of spiral-wound modules were manufactured, tested and optimized during this project, which culminated in a field test at a Shell facility in East Texas. The short field test showed that membrane module performance on an actual natural gas stream was close to that observed in the laboratory tests with cleaner streams. An extensive technical and economic analysis was performed to determine the best applications for the membrane process. Two areas were identified: the low-flow-rate, high-hydrogen-sulfide-content region and the high-flow-rate, high-hydrogen-sulfide-content region. In both ...
Date: January 29, 1998
Creator: Amo, K.; Baker, R.W.; Helm, V.D.; Hofmann, T.; Lokhandwala, K.A.; Pinnau, I. et al.
Partner: UNT Libraries Government Documents Department

HYDROGEN SEPARATION MEMBRANES

Description: A likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse through the membrane structure. An amorphous membrane such as zinc sulfide appeared to be promising. Previously, ZnS film coating tests had been performed using an electron-beam vacuum coating instrument, with zinc films successfully applied to glass substrates. The coatings appeared relatively stable in air and in a simple simulated gasification atmosphere at elevated temperature. Because the electron-beam coating instrument suffered irreparable breakdown, several alternative methods were tested in an effort to produce a nitrogen-impermeable, hydrogen-permeable membrane on porous sintered steel substrates. None of the preparation methods proved successful in sealing the porous substrate against nitrogen gas. To provide a nitrogen-impermeable ZnS material to test for hydrogen permeability, two ZnS infrared sample windows were purchased. These relatively thick ''membranes'' did not show measurable permeation of hydrogen, either due to lack of absorption or a negligible permeation rate due to their thickness. To determine if hydrogen was indeed adsorbed, thermogravimetric and differential thermal analyses tests were performed on samples of ZnS powder. A significant uptake of hydrogen gas occurred, corresponding to a maximum of 1 mole H{sub 2} per 1 mole ZnS at a temperature of 175 C. The hydrogen remained in the material at ambient temperature in a hydrogen atmosphere, but approximately 50% would be removed in argon. Reheating in a hydrogen atmosphere resulted in no additional hydrogen uptake. Differential scanning calorimetry indicated that the hydrogen uptake was probably due to the formation of a zinc-sulfur-hydrogen species resulting in the formation of hydrogen sulfide. The zinc sulfide was found to be unstable above approximately 200 C, probably with the reduction to metallic zinc with the evolution of hydrogen ...
Date: August 1, 1999
Creator: McCollor, Donald P. & Kay, John P.
Partner: UNT Libraries Government Documents Department

BIODESULF(TM), A Novel Biological Technology for the Removal of H2S From Sour Natural Gas

Description: The state-of-the-art technologies for the removal of sulfur compounds from Sour Natural Gas (SNG) are not cost-effective when scaled down to approximately 2-5 MMSCFD. At the same time, the SNG Production is increasing at 3-6 TCF/Yr and -78 TCF potential reserves are also sour. Assuming only 3% treatment of this potential SNG market is for small volume processing, the potential U.S. Market is worth $0.14 to $0.28 billion. Therefore, the Gas Processing Industry is seeking novel, cost-effective, environmentally compatible and operator friendly technologies applicable to the small volume producers in the range of less than 1 MMSCFD to - 5 MMSCFD. A novel biological process, BIODESTJLFTM (patent pending), developed at ARCTECH removes H{sub 2}S and other sulfur contaminants that make the Natural Gas Sour. The removal is accomplished by utilizing an adapted mixed microbial culture (consortium). A variety of anaerobic microbial consortia from ARCTECH`s Microbial Culture Collection were grown and tested for removal of H{sub 2}S. One of these consortia, termed SS-11 was found to be particularly effective. Utilizing the SS-11 consortium, a process has been developed on a laboratory-scale to remove sulfur species from Sour Natural Gas at well head production pressures and temperatures. The process has been independently evaluated and found to be promising in effectively removing H{sub 2}S and other sulfur species cost effectively.
Date: October 1, 1997
Creator: Srivastava, K.C.; Stashick, J.J.; Johnson, P.E. & Kaushik, N.K.
Partner: UNT Libraries Government Documents Department

New technology for sulfide reduction and increased oil recovery. Third quarter progress report

Description: Project work was initiated by Geo-Microbial Technologies, Inc. (GMT), Ochelata, Oklahoma for Contract Number DE-FG01-97EE15659 on June 18, 1997. The purpose of this project is to demonstrate reduction of sulfide contamination, as well as possible improvement of production in oil and gas production systems. This will be accomplished by application of the BioCompetitive Exclusion (BCX) process developed by GMT. A broad spectrum of well types and geographical locations is anticipated. The BCX process is designed to manipulate indigenous reservoir bacteria with the addition of synergistic inorganic chemical formulae. These treatments will stimulate growth of beneficial microbes, while suppressing metabolic activity of sulfate reducing bacteria (SRB), the primary source of harmful sulfide production.
Date: March 20, 1998
Partner: UNT Libraries Government Documents Department

New technology for sulfide reduction and increased oil recovery. Second quarter progress report, September 7, 1997--December 8, 1997

Description: Project work was initiated by Geo-Microbial Technologies, Inc. (GMT), Ochelata, Oklahoma for Contract Number DE-FG01-97EE15659 on June 18, 1997. The purpose of this project is to demonstrate reduction of sulfide contamination, as well as possible improvement of production in oil and gas production systems. This will be accomplished by application of the BioCompetitive Exclusion (BCX) process developed by GMT. A broad spectrum of well types and geographical locations is anticipated. The BCX process is designed to manipulate indigenous reservoir bacteria with the addition of synergistic inorganic chemical formulae. These treatments will stimulate growth of beneficial microbes, while suppressing metabolic activity of sulfate reducing bacteria (SRB), the primary source of harmful sulfide production.
Date: December 20, 1998
Partner: UNT Libraries Government Documents Department

Method for direct production of carbon disulfide and hydrogen from hydrocarbons and hydrogen sulfide feedstock

Description: A method for converting hydrocarbons and hydrogen sulfide to carbon disulfide and hydrogen is provided comprising contacting the hydrocarbons and hydrogen sulfide to a bi-functional catalyst residing in a controlled atmosphere for a time and at a temperature sufficient to produce carbon disulfide and hydrogen. Also provided is a catalyst for converting carbon sulfides and hydrogen sulfides to gasoline range hydrocarbons comprising a mixture containing a zeolite catalyst and a hydrogenating catalyst.
Date: December 1998
Creator: Miao, Frank Q. & Erekson, Erek James
Partner: UNT Libraries Government Documents Department

Data summary report for M.W. Kellogg Z-sorb sorbent tests. CRADA 92-008 Final report

Description: A series of tests were undertaken from August 6, 1992 through July 6, 1993 at METC`s High Pressure Bench-Scale Hot Gas Desulfurization Unit to support a Cooperative Research and Development Agreement (CRADA) between METC`s Sorbent Development Cluster and M.W. Kellogg. The M.W. Kellogg Company is currently developing a commercial offering of a hot gas clean-up system to be used in Integrated Gasification Combined Cycle (IGCC) systems. The intent of the CRADA agreement was to identify a suitable zinc-based desulfurization sorbent for the Sierra Pacific Power Company Clean Coal Technology Project, to identify optimum operating conditions for the sorbent, and to estimate potential sorbent loss per year. This report presents results pertaining to Phillips Petroleum`s Z-Sorb III sorbent.
Date: May 1994
Creator: Everett, C. E. & Monaco, S .J.
Partner: UNT Libraries Government Documents Department

Kinetics of Mn-based sorbents for hot coal gas desulfurization. Quarterly progress report, March 15, 1995--July 15, 1995

Description: Hot gas desulfurization may be accomplished by using solid sorbents such as oxides of those metals that form stable sulfides. The effectiveness of a desulfurizing agent in treating such gases is related to the predicted equilibrium partial pressure of hydrogen sulfide which will be present in a phase combination of the reduced form of sulfide and oxide phases. The focus of much current work being performed by the Department of Energy on sorbent development is in the use of zinc ferrite, zinc titanate, and Z-Sorb. The latter sorbent is a commercial product consisting of ZnO, a promoter, and a proprietary supporting matrix designed to provide stability and prolong sorbent life. Although these Zn-based sorbents have been the subject of extensive pilot-scale and process development work, all sorbents produced to date still experience structural and reactive degradation over multi-cycle use at relatively moderate temperatures. An effective alternative to zinc-based sorbents could be manganese sorbents which withstand high temperature operation and also maintain structural and reactive integrity over many cycles, as investigations by Ben-Slimane and Hepworth have indicated. Thermodynamic limits may prevent MnO from achieving the low sulfur specifications of the product gas for use in a molten carbonate fuel cell, but under the correct conditions the guideline for IGCC systems can easily be achieved. Furthermore, manganese sorbents could possibly be used in conjunction with a polishing sorbent (such as zinc oxide) possessing more favorable thermodynamic properties to reach levels acceptable for fuel cell applications (< 10 ppmv). Such an arrangement may not require that the zinc sulfide be regenerated since the sulfur concentration of the cleaned gas is low enough that the zinc oxide may be discarded when exhausted.
Date: July 15, 1995
Creator: Hepworth, M.T.
Partner: UNT Libraries Government Documents Department

High temperature electrochemical polishing of H{sub 2}S from coal gasification process streams. Quarterly progress report, July 1, 1995--September 30, 1995

Description: Coal may be used to generate electrical energy by any of several processes, most of which involve combustion or gasification. Combustion in a coal-fired boiler and power generation using a steam-cycle is the conventional conversion method; however total energy conversion efficiencies for this type of process are only slightly over 30%. Integration of a gas-cycle in the process (combined cycle) may increase the total conversion efficiency to 40%. Conversion processes based on gasification offer efficiencies above 50%. H{sub 2}S is the predominant gaseous contaminant in raw coal gas. This process is concerned with the removal of H{sub 2} from coal gas through an electrochemical membrane technology.
Date: March 1, 1996
Creator: Winnick, J.
Partner: UNT Libraries Government Documents Department

Membrane process for separating H{sub 2}S from natural gas

Description: Objective was to develop a membrane process for separating hydrogen sulfide and other impurities (CO{sub 2}, water vapor) from low-quality natural gas. A membrane material was identified with very high H{sub 2}/CH{sub 4} selectivity in the range of 40--60; membrane production was scaled up to commercial size rolls; high-pressure membrane and module development and optimization were completed; and a membrane permeation flux of 4{times}10{sub {minus}6} cm{sup 3}/s{center_dot}cm{sup 2}cmHg, twice as high state-of-the-art cellulose acetate membranes, was achieved.
Date: July 1, 1995
Creator: Baker, R.W.
Partner: UNT Libraries Government Documents Department