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NUMERICAL CALCULATIONS FOR THE ASYMPTOTIC, DIFFUSION DOMINATED MASS-TRANSFER COEFFICIENT IN PACKED BED REACTORS

Description: For deep beds, the effective Sherwood number approaches a proportional relationship to the Peclet number as the Peclet number tends to zero. A sinusoidal periodically constricted tube model for the voids in the bed has been used to predict the constant of proportionality. This constant depends upon the dimensionless ratios of three lengths: the average tube radius, the oscillation amplitude, and wavelength.
Date: November 1, 1977
Creator: Fedkiw, Peter & Newman, John
Partner: UNT Libraries Government Documents Department

Field Deployable DNA analyzer

Description: This report details the feasibility of a field deployable DNA analyzer. Steps for swabbing cells from surfaces and extracting DNA in an automatable way are presented. Since enzymatic amplification reactions are highly sensitive to environmental contamination, sample preparation is a crucial step to make an autonomous deployable instrument. We perform sample clean up and concentration in a flow through packed bed. For small initial samples, whole genome amplification is performed in the packed bed resulting in enough product for subsequent PCR amplification. In addition to DNA, which can be used to identify a subject, protein is also left behind, the analysis of which can be used to determine exposure to certain substances, such as radionuclides. Our preparative step for DNA analysis left behind the protein complement as a waste stream; we determined to learn if the proteins themselves could be analyzed in a fieldable device. We successfully developed a two-step lateral flow assay for protein analysis and demonstrate a proof of principle assay.
Date: February 9, 2005
Creator: Wheeler, E; Christian, A; Marion, J; Sorensen, K; Arroyo, E; Vrankovich, G et al.
Partner: UNT Libraries Government Documents Department

Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

Description: Commercial spent fluid catalytic cracking (FCC) catalysts provided by Engelhard and Albemarle were used as supports for Fe-based catalysts with the goal of improving the attrition resistance of typical F-T catalysts. Catalysts with the Ruhrchemie composition (100 Fe/5 Cu/4.2 K/25 spent FCC on mass basis) were prepared by wet impregnation. XRD and XANES analysis showed the presence of Fe{sub 2}O{sub 3} in calcined catalysts. FeC{sub x} and Fe{sub 3}O{sub 4} were present in the activated catalysts. The metal composition of the catalysts was analyzed by ICP-MS. F-T activity of the catalysts activated in situ in CO at the same conditions as used prior to the attrition tests was measured using a fixed bed reactor at T = 573 K, P = 1.38 MPa and H{sub 2}:CO ratio of 0.67. Cu and K promoted Fe supported over Engelhard provided spent FCC catalyst shows relatively good attrition resistance (8.2 wt% fines lost), high CO conversion (81%) and C{sub 5}+ hydrocarbons selectivity (18.3%).
Date: February 5, 2010
Creator: Adeyiga, Adeyinka
Partner: UNT Libraries Government Documents Department

Review of arsenic removal technologies for contaminated groundwaters.

Description: This review was compiled to summarize the technologies currently being investigated to remove arsenic from drinking waters, with a special focus on developing and third-world countries where the problem is exacerbated by flooding and depressed economic conditions. The reason for compiling this report is to provide background material and a description of competing technologies currently described in the literature for arsenic removal. Based on the sophistication and applicability of current technologies, Argonne National Laboratory may develop an improved method based on magnetic particle technology. Magnetic particle sorbents may afford improved reaction rates, facilitate particle-water separation, and offer reusability. Developing countries like Vietnam and Bangladesh cannot afford expensive, large-scale treatments to remove arsenic from drinking waters to acceptable limits (from 50 ppb to 10 ppb, depending on the country). Low-cost, effective technologies that can be readily available at the household or community level are needed to solve the present crisis. Appropriate technologies should meet certain criteria, including the following: The treatment must be applicable over a wide range of arsenic concentrations; It should be easy to use without running water or electricity; and The materials for the treatment should be cheap and readily available, and/or suitable for reuse. Our review of arsenic removal technologies and procedures indicates that iron filings, ferric salts, granular ferric hydroxide, alumina manganese oxide, Aqua-bind., and Kimberlite tailings are potentially low-cost sorbents that can remove arsenic after simple mixing in a relatively short time. However, all these technologies suffer from significant shortcomings. Ferric salts are cheap and very effective at removing arsenic but the reaction rates are slow. Fixed-bed columns make use of activated alumina and iron-coated sands but do not work well with groundwater having high concentrations of iron because iron precipitates in the presence of air, which could clog and foul the column. Synthetic sorbents ...
Date: May 2, 2003
Creator: Vu, K. B.; Kaminski, M. D. & Nunez, L.
Partner: UNT Libraries Government Documents Department

CATALYTIC GASIFICATION OF COAL USING EUTECTIC SALT MIXTURES

Description: This progress report on the Department of Energy project DE-FG-97FT97263 entitled, ''Catalytic Gasification of Coal Using Eutectic Salt Mixtures,'' covers the period April-September 1998. The specific aims of the project for this period were to identify appropriate eutectic salt mixture catalysts for the gasification of Illinois No.6 coal, evaluate various impregnation or catalyst addition methods to improve catalyst dispersion, and evaluate gasification performance in a bench-scale fixed bed reactor. The project is being conducted jointly by Clark Atlanta University (CAU), the University of Tennessee Space Institute (UTSI) and the Georgia Institute of Technology (Georgia Tech) with CAU as the prime contractor. Several single salt catalysts and binary and ternary eutectic catalysts were investigated at Clark Atlanta University. Physical mixing and incipient wetness methods were investigated as catalyst addition techniques. Gasification was carried out using TGA at CAU and UTSI and with a fixed-bed reactor at UTSI. The results showed better gasification activity in the presence of the catalysts tested. The eutectic salt studies showed clear agreement between the melting points of the prepared eutectics and reported literature values. The order of catalytic activity observed was ternary > binary > single salt. With the soluble single salt catalysts, the incipient wetness method was found to give better results than physical mixing technique. Also, catalyst preparation conditions such as catalyst loading, drying time and temperature were found to influence the gasification rate. Based on the Clark Atlanta University studies on Task 1, the project team selected the 43.5%Li{sub 2}CO{sub 3}-31.5%Na{sub 2}CO{sub 3}-25%K{sub 2}CO{sub 3} ternary eutectic and the 29%Na{sub 2}CO{sub 3}-71%K{sub 2}CO{sub 3} and 2.3%KNO{sub 3}-97.7%K{sub 2}CO{sub 3} binary eutectic for the fixed bed studies at UTSI. The eutectic salts were found to be highly insoluble in aqueous medium. As a result the technique of adding the eutectic to the raw coal ...
Date: October 1, 1998
Partner: UNT Libraries Government Documents Department

CATALYTIC GASIFICATION OF COAL USING EUTECTIC SALT MIXTURES

Description: This progress report on the Department of Energy project DE-FG-97FT97263 entitled, ''Catalytic Gasification of Coal Using Eutectic Salt Mixtures'', covers the period April-September 1998. The specific aims of the project for this period were to identify appropriate eutectic salt mixture catalysts for the gasification of Illinois No.6 coal, evaluate various impregnation or catalyst addition methods to improve catalyst dispersion, and evaluate gasification performance in a bench-scale fixed bed reactor. The project is being conducted jointly by Clark Atlanta University (CAU), the University of Tennessee Space Institute (UTSI) and the Georgia Institute of Technology (Georgia Tech) with CAU as the prime contractor. Several single salt catalysts and binary and ternary eutectic catalysts were investigated at Clark Atlanta University. Physical mixing and incipient wetness methods were investigated as catalyst addition techniques. Gasification was carried out using TGA at CAU and UTSI and with a fixed-bed reactor at UTSI. The results showed better gasification activity in the presence of the catalysts tested. The eutectic salt studies showed clear agreement between the melting points of the prepared eutectics and reported literature values. The order of catalytic activity observed was ternary > binary > single salt. With the soluble single salt catalysts, the incipient wetness method was found to give better results than physical mixing technique. Also, catalyst preparation conditions such as catalyst loading, drying time and temperature were found to influence the gasification rate. Based on the Clark Atlanta University studies on Task 1, the project team selected the 43.5%Li{sub 2}CO{sub 3}-31.5%Na{sub 2}CO{sub 3}-25%K{sub 2}CO{sub 3} ternary eutectic and the 29%Na{sub 2}CO{sub 3}-71%K{sub 2}CO{sub 3} and 2.3% KNO{sub 3}-97.7%K{sub 2}CO{sub 3} binary eutectic for the fixed bed studies at UTSI. The eutectic salts were found to be highly insoluble in aqueous medium. As a result the technique of adding the eutectic to the raw ...
Date: April 1, 2000
Partner: UNT Libraries Government Documents Department

OXIDATIVE COUPLING OF METHANE USING INORGANIC MEMBRANE REACTORS

Description: The objective of this research is to study the oxidative coupling of methane in catalytic inorganic membrane reactors. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and higher yields than in conventional non-porous, co-feed, fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gas phase reactions, which are believed to be a main route for the formation of CO{sub x} products. Such gas phase reactions are a cause of decreased selectivity in the oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Membrane reactor technology also offers the potential for modifying the membranes both to improve catalytic properties as well as to regulate the rate of the permeation/diffusion of reactants through the membrane to minimize by-product generation. Other benefits also exist with membrane reactors, such as the mitigation of thermal hot-spots for highly exothermic reactions such as the oxidative coupling of methane. The application of catalytically active inorganic membranes has potential for drastically increasing the yield of reactions which are currently limited by either thermodynamic equilibria, product inhibition, or kinetic selectivity.
Date: April 1, 1998
Creator: Ma, Dr. Y.H.; Moser, Dr. W.R.; Dixon, Dr. A.G.; Ramachandra, Dr. A.M.; Lu, Dr. Y. & Binkerd, C.
Partner: UNT Libraries Government Documents Department

CATALYTIC GASIFICATION OF COAL USING EUTECTIC SALT MIXTURES

Description: The project, ''Catalytic Gasification of Coal Using Eutectic Salt Mixtures'', is being conducted jointly by Clark Atlanta University (CAU), the University of Tennessee Space Institute (UTSI) and the Georgia Institute of Technology (GT). The aims of the project are to: identify appropriate eutectic salt mixture catalysts for the gasification of Illinois No.6 coal; evaluate various impregnation or catalyst addition methods to improve catalyst dispersion; evaluate effects of major process variables (e.g., temperature, system pressure, etc.) on coal gasification; evaluate the recovery, regeneration and recycle of the spent catalysts in a bench-scale fixed bed reactor; and conduct thorough analysis and modeling of the gasification process to provide a better understanding of the fundamental mechanisms and kinetics of the process. The eutectic catalysts increased gasification rate significantly. The methods of catalyst preparation and addition had significant effect on the catalytic activity and coal gasification. The incipient wetness method gave more uniform catalyst distribution than that of physical mixing for the soluble catalysts resulting in higher gasification rates for the incipient wetness samples. The catalytic activity increased by varying degrees with catalyst loading. The above results are especially important since the eutectic catalysts (with low melting points) yield significant gasification rates even at low temperatures. Among the ternary eutectic catalysts studied, the system 39% Li{sub 2}CO{sub 3}-38.5% Na{sub 2}CO{sub 3}-22.5% Rb{sub 2}CO{sub 3} showed the best activity and will be used for further bench scale fixed-bed gasification reactor in the next period. Based on the Clark Atlanta University studies in the previous reporting period, the project team selected the 43.5% Li{sub 2}CO{sub 3}-31.5% Na{sub 2}CO{sub 3}-25% K{sub 2}CO{sub 3} ternary eutectic and the 29% Na{sub 2}CO{sub 3}-71% K{sub 2}CO{sub 3} binary eutectic for the fixed-bed studies at UTSI during this reporting period. Temperature was found to have a significant effect on the rate ...
Date: April 1, 1999
Partner: UNT Libraries Government Documents Department

THE ECONOMICAL PRODUCTION OF ALCOHOL FUELS FROM COAL-DERIVED SYNTHESIS GAS

Description: Langmuir-Hinshelwood-type kinetic schemes were derived for the formation of methanol through butanol and total hydrocarbons over a Co-K-MoS{sub 2}/C catalyst. Reduced Mo-Ni-K/C materials continue to be considered as promising catalysts for HAS. A kinetic study of this catalyst has been started. TPR results on alkali-substituted Mo/C are beginning to be amenable to a systematic quantitative analysis. The characterization studies of transition-metal-oxide catalysts has ended. Consideration of various models for the performance of a packed-bed membrane reactor in the synthesis of methanol indicates that a model involving large (but finite) permeances of CO and MeOH may be optimal. Comparison of the membrane reactor with a packed-bed tubular reactor indicates that the former may be advantageous at low total flow rates.
Date: January 1, 1997
Partner: UNT Libraries Government Documents Department

Advanced Catalytic Hydrogenation Retrofit Reactor

Description: Industrial hydrogenation is often performed using a slurry catalyst in large stirred-tank reactors. These systems are inherently problematic in a number of areas, including industrial hygiene, process safety, environmental contamination, waste production, process operability and productivity. This program proposed the development of a practical replacement for the slurry catalysts using a novel fixed-bed monolith catalyst reactor, which could be retrofitted onto an existing stirred-tank reactor and would mitigate many of the minitations and problems associated with slurry catalysts. The full retrofit monolith system, consisting of a recirculation pump, gas/liquid ejector and monolith catalyst, is described as a monolith loop reactor or MLR. The MLR technology can reduce waste and increase raw material efficiency, which reduces the overall energy required to produce specialty and fine chemicals.
Date: August 15, 2002
Creator: Machado, Reinaldo M.
Partner: UNT Libraries Government Documents Department

Fixed Bed Biomass Gasifier

Description: The report details work performed by Gazogen to develop a novel biomass gasifier for producimg electricity from commercially available hardwood chips. The research conducted by Gazogen under this grant was intended to demonstrate the technical and economic feasibility of a new means of producing electricity from wood chips and other biomass and carbonaceous fuels. The technical feasibility of the technology has been furthered as a result of the DOE grant, and work is expected to continue. The economic feasibility can only be shown when all operational problems have been overocme. The technology could eventually provide a means of producing electricity on a decentralized basis from sustainably cultivated plants or plant by-products.
Date: March 31, 2006
Creator: Bielenberg, Carl
Partner: UNT Libraries Government Documents Department

Subtask 2.8 - Control of Trace Elements in Gasification Systems

Description: Detailed investigations were carried out to investigate the removal of mercury using a variety of substrates at elevated temperature under reducing conditions. Sorbents tested mainly comprised 6A, 7A, 1B, 2B, and metals from the periodic table. The new high-surface halogen-treated carbon sorbents performed exceptionally well on the bench scale at relatively high temperatures (400 C). The new sorbents could be incorporated into a gas cleanup technology for fuel gas, where the gas is cooled to medium temperatures. Other work in this task focused on halogen-containing sorbents prepared on a carbon support. Similar sorbents had been previously found to be superior for mercury in flue gas. All granular sorbents were conducted in fixed beds heated at 350 and 400 C with 10 vol% hydrogen in a nitrogen stream containing 34.8 {mu}g/m{sup 3} of Hg{sup 0}.
Date: March 28, 2009
Creator: Swanson, Michael
Partner: UNT Libraries Government Documents Department

KINETICS OF DIRECT OXIDATION OF H2S IN COAL GAS TO ELEMENTAL SULFUR

Description: The direct oxidation of H{sub 2}S to elemental sulfur in the presence of SO{sub 2} is ideally suited for coal gas from commercial gasifiers with a quench system to remove essentially all the trace contaminants except H{sub 2}S. This direct oxidation process has the potential to produce a super clean coal gas more economically than both conventional amine-based processes and HGD/DSRP. The objective of this research is to support the near- and long-term DOE efforts to commercialize this direct oxidation technology. The objectives of this research are to measure kinetics of direct oxidation of H{sub 2}S to elemental sulfur in the presence of a simulated coal gas mixture containing SO{sub 2}, H{sub 2}, and moisture, using 60-{micro}m C-500-04 alumina catalyst particles and a PFA differential fixed-bed micro reactor, and to develop kinetic rate equations and model the direct oxidation process to assist in the design of large-scale plants. To achieve the above-mentioned objectives, experiments on conversion of hydrogen sulfide into elemental sulfur were carried out for the space time range of 0.01-0.047 seconds at 125-155 C to evaluate effects of reaction temperatures, moisture concentrations, reaction pressures on conversion of hydrogen sulfide into elemental sulfur. Simulated coal gas mixtures consist of 61-89 v% hydrogen, 2,300-9,200-ppmv hydrogen sulfide, 1,600-4,900 ppmv sulfur dioxide, and 2.6-13.7 vol % moisture, and nitrogen as remainder. Volumetric feed rates of a simulated coal gas mixture to the reactor are 100-110 cm{sup 3}/min at room temperature and atmospheric pressure (SCCM). The temperature of the reactor is controlled in an oven at 125-155 C. The pressure of the reactor is maintained at 28-127 psia. The following results were obtained based on experimental data generated from the differential reactor system, and their interpretations, (1) Concentration of moisture and concentrations of both H{sub 2}S and SO{sub 2} appear to affect slightly ...
Date: January 1, 2003
Creator: Kwon, K. C.
Partner: UNT Libraries Government Documents Department

Surface chemistry investigation of colloid transport in packed beds. Final report, August 1, 1989--July 31, 1996

Description: The importance of colloids as co-transport agents for pollutants in subsurface systems hinges on the extent to which electrostatic or other sources of repulsive colloid-collector interactions inhibit their filtration. When electrostatic interactions are favorable, for example when the colloid and groundwater media have opposite charge, colloids may be expected to travel only a few centimeters in saturated porous media. Repulsive electrostatic interactions between colloids and aquifer media with the same charge sign are postulated to significantly mobilize particles. As it happens, however, theories describing particle filtration from first principles, i.e., DLVO (Derjagin and Landau, Verwey and Overbeek) theory, dramatically underestimate filtration rates when colloid-collector interactions are electrostatically repulsive. One of the primary objectives of the project was to experimentally investigate potential reasons for the historical lack of agreement between particle filtration models based on DLVO theory and observed particle deposition rates. An important hypothesis of the study was to test the validity of the assumption of surface homogeneity, as required by these models. The approach was to focus on collector surfaces that were commonly used as model systems, e.g., glass beads and quartz sand. Laboratory-scale column filtration experiments were conducted with colloidal polystyrene latex spheres. Collector surface preparation and cleaning approaches were examined, as well as the effects of solution chemistry.
Date: December 31, 1996
Creator: Olson, T.M.
Partner: UNT Libraries Government Documents Department

CO-FIRING COAL: FEEDLOT AND LITTER BIOMASS FUELS

Description: The following are proposed activities for quarter 1 (6/15/00-9/14/00): (1) Finalize the allocation of funds within TAMU to co-principal investigators and the final task lists; (2) Acquire 3 D computer code for coal combustion and modify for cofiring Coal:Feedlot biomass and Coal:Litter biomass fuels; (3) Develop a simple one dimensional model for fixed bed gasifier cofired with coal:biomass fuels; and (4) Prepare the boiler burner for reburn tests with feedlot biomass fuels. The following were achieved During Quarter 5 (6/15/00-9/14/00): (1) Funds are being allocated to co-principal investigators; task list from Prof. Mukhtar has been received (Appendix A); (2) Order has been placed to acquire Pulverized Coal gasification and Combustion 3 D (PCGC-3) computer code for coal combustion and modify for cofiring Coal: Feedlot biomass and Coal: Litter biomass fuels. Reason for selecting this code is the availability of source code for modification to include biomass fuels; (3) A simplified one-dimensional model has been developed; however convergence had not yet been achieved; and (4) The length of the boiler burner has been increased to increase the residence time. A premixed propane burner has been installed to simulate coal combustion gases. First coal, as a reburn fuel will be used to generate base line data followed by methane, feedlot and litter biomass fuels.
Date: October 24, 2000
Creator: Annamalai, Dr. Kalyan; Sweeten, Dr. John & Mukhtar, Dr. Sayeed
Partner: UNT Libraries Government Documents Department

CO-FIRING COAL: FEEDLOT AND LITTER BIOMASS FUELS

Description: The following are proposed activities for quarter 3 (12/15/00-3/14/01): (1) Conduct TGA and fuel characterization studies - Task 1; (2) Continue to perform re-burn experiments. - Task 2; (3) Design fixed bed combustor. - Task 3; and (4) Modify the PCGC2 code to include moisture evaporation model - Task 4. The following were achieved During Quarter 3 (12/15/0-3/14/01): (1) Conducted TGA and Fuel Characterization studies (Appendix I). A comparison of -fuel properties, TGA traces etc is given in Appendix I. Litter has 3 and 6 times more N compared to coal on mass and heat basis. The P of litter is almost 2 % (Task 1). Both litter biomass (LB) and feedlot biomass (FB) have been pulverized. The size distributions are similar for both litter and FB in that 75 % pass through 150 {micro}m sieve while for coal 75 % pass through 60 {micro}m sieve. Rosin Rammler curve parameters are given. The TGA characteristics of FB and LB are similar and pyrolysis starts at 100 C below that of coal; (2) Reburn experiments with litter and with FB have been performed (Appendix II) -Task 2. Litter is almost twice effective (almost 70--90 % reduction) compared to coal in reducing the NOx possibly due to presence of N in the form of NH{sub 3}; (3) Designed fixed bed gasifier/combustor (Appendix III) - Task 3; and (4) Modified PCGC2 to include moisture evaporation model in coal and biomass particles. (Appendix IV) - Task 4.
Date: May 10, 2001
Creator: Annamalai, Dr. Kalyan; Sweeten, Dr. John & Mukhtar, Dr. Sayeed
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF HIGH ACTIVITY, COAL DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

Description: This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics. During the reporting period, the following has been accomplished: (1) A MS-TGA (mass spectrometric-thermogravimetric analysis) apparatus, which is one of the primary instruments that will be used in these studies, has been refurbished and modified to meet the requirements of this project. A NO{sub x} chemiluminescence analyzer (ThermoElectron, Model 10) has been added to the instrument to monitor NO{sub x} concentrations in the feed and product streams. Computer control and data acquisition system has been updated and modified to accommodate the requirements of the specific types of experiments planned. The diffusion pumps used to maintain vacuum for the mass spectrometer system have been replaced with turbomolecular pumps (Varian 300 HT). (2) A packed bed reactor/gas flow system has been assembled for performing reactivity studies. This system employs a Kin-Tek gas calibration/mixing system for varying NO and CO concentrations in the feed gas to the packed bed, a NO{sub x} chemiluminescence analyzer (ThermoElectron, Model 10), and a quadrupole mass spectrometer (Dycor). This system is required for steady-state reactivity studies, as well as mechanistic studies on the effects of NO and CO in the gas phase on intermediate oxygen surface complex populations on the carbon substrates. (3) Work has continued on the application of contrast matching, small angle neutron scattering to the characterization and development of char porosity. Contrast matching with perdeuterated toluene has been used to discriminate between inaccessible and inaccessible porosity in Pittsburgh No.8 ...
Date: December 31, 1998
Creator: Calo, Joseph M.
Partner: UNT Libraries Government Documents Department

CO2 SELECTIVE CERAMIC MEMBRANE FOR WATER-GAS SHIFT REACTION WITH CONCOMITANT RECOVERY OF CO2

Description: Two process schemes have been investigated by us for the use of hydrotalcites we prepared as CO{sub 2} adsorbents to enhance water gas shift (WGS) reaction: Case I involves the adsorption enhanced WGS packed bed reactor and Case II involves the adsorption enhanced WGS membrane reactor. Both cases will achieve the same objective as the hydrotalcite membrane reactor: i.e., improving the WGS reactor efficiency via the concomitant removal of CO{sub 2} for sequestration. In this report a detailed investigation of the design characteristics and performance of Case II, termed the Hybrid Adsorbent-Membrane Reactor (HAMR), is presented. The HAMR system includes a packed-bed catalytic membrane reactor (hydrogen selective) coupling the WGS reaction (in a porous hydrogen selective membrane) with CO{sub 2} removal with an adsorbent in the permeate side. The reactor characteristics have been investigated for a range of permeance and selectivity relevant to the aforementioned application. The HAMR system shows enhanced CO conversion, hydrogen yield, and product purity, and provides good promise for reducing the hostile operating conditions of conventional WGS reactors, and for meeting the CO{sub 2} sequestration objective. In the next quarterly report we will present the simulation result for Case I as well as the progress on hydrotalcite membrane synthesis.
Date: February 19, 2004
Creator: Liu, Paul K. T.
Partner: UNT Libraries Government Documents Department

ATTRITION RESISTANT IRON-BASED FISCHER-TROPSCH CATALYSTS

Description: Fischer-Tropsch (FT) synthesis to convert syngas (CO + H{sub 2}) derived from natural gas or coal to liquid fuels and wax is a well-established technology. For low H{sub 2} to CO ratio syngas produced from CO{sub 2} reforming of natural gas or from gasification of coal, the use of Fe catalysts is attractive because of their high water gas shift activity in addition to their high FT activity. Fe catalysts are also attractive due to their low cost and low methane selectivity. Because of the highly exothermic nature of the FT reaction, there has been a recent move away from fixed-bed reactors toward the development of slurry bubble column reactors (SBCRs) that employ 30 to 90 {micro}m catalyst particles suspended in a waxy liquid for efficient heat removal. However, the use of FeFT catalysts in an SBCR has been problematic due to severe catalyst attrition resulting in fines that plug the filter employed to separate the catalyst from the waxy product. Fe catalysts can undergo attrition in SBCRs not only due to vigorous movement and collisions but also due to phase changes that occur during activation and reaction.
Date: October 1, 1999
Creator: Jothimurugesan, K.; James G. Goodwin, Jr. & Gangwal, Santosh K.
Partner: UNT Libraries Government Documents Department

SiC-Based Hydrogen Selective Membranes for Water-Gas-Shift Reaction, Annual Report: 2002

Description: In the first two years of this project, we focused on the membrane synthesis, characterization and optimization. In the past year, we have concentrated on the product development for improving the efficiency of hydrogen recovery from coal gasifier off-gas via water-gas-shift (WGS) reaction. A mathematical simulation study has been performed to compare the performance of the membrane reactor (MR) vs conventional packed bed rector for WGS reaction. Our result demonstrates that >99.999% conversion can be accomplished via WGS-MR using the hydrogen selective membrane developed by us. Further, water/CO ratio can be reduced, and >97% hydrogen recovery and <200 ppm CO can be accomplished according to the mathematical simulation. Thus, we believe that the operating economics of WGS can be improved significantly based upon the proposed MR concept. In parallel, gas separations and hydrothermal and long-term-storage stability of the hydrogen selected membrane have been experimentally demonstrated using a pilot-scale tubular membrane under a simulated WGS environment. For the remaining period of this project, we will conduct experimental study using the hydrogen selective membrane to verify the performance projected by the mathematical simulation.
Date: October 31, 2002
Creator: Liu, Paul K. T.
Partner: UNT Libraries Government Documents Department

INTEGRATED HYDROGEN STORAGE SYSTEM MODEL

Description: Hydrogen storage is recognized as a key technical hurdle that must be overcome for the realization of hydrogen powered vehicles. Metal hydrides and their doped variants have shown great promise as a storage material and significant advances have been made with this technology. In any practical storage system the rate of H2 uptake will be governed by all processes that affect the rate of mass transport through the bed and into the particles. These coupled processes include heat and mass transfer as well as chemical kinetics and equilibrium. However, with few exceptions, studies of metal hydrides have focused primarily on fundamental properties associated with hydrogen storage capacity and kinetics. A full understanding of the complex interplay of physical processes that occur during the charging and discharging of a practical storage system requires models that integrate the salient phenomena. For example, in the case of sodium alanate, the size of NaAlH4 crystals is on the order of 300nm and the size of polycrystalline particles may be approximately 10 times larger ({approx}3,000nm). For the bed volume to be as small as possible, it is necessary to densely pack the hydride particles. Even so, in packed beds composed of NaAlH{sub 4} particles alone, it has been observed that the void fraction is still approximately 50-60%. Because of the large void fraction and particle to particle thermal contact resistance, the thermal conductivity of the hydride is very low, on the order of 0.2 W/m-{sup o}C, Gross, Majzoub, Thomas and Sandrock [2002]. The chemical reaction for hydrogen loading is exothermic. Based on the data in Gross [2003], on the order of 10{sup 8}J of heat of is released for the uptake of 5 kg of H{sub 2}2 and complete conversion of NaH to NaAlH{sub 4}. Since the hydride reaction transitions from hydrogen loading to discharge ...
Date: November 16, 2007
Creator: Hardy, B
Partner: UNT Libraries Government Documents Department

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

Description: Efforts during this second year focused on four areas: (1) continued searching and summarizing of published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) investigation of CO adsorption/desorption and temperature programmed hydrogenation (TPH) of carbonaceous species after FTS on unsupported iron and alumina-supported iron catalysts; (3) activity tests of alumina-supported iron catalysts in a fixed bed reactor; (4) sequential design of experiments, for the collection of rate data in a Berty CSTR reactor, and nonlinear-regression analysis to obtain kinetic parameters. Literature sources describing mechanistic and kinetic studies of Fischer-Tropsch synthesis on iron catalysts were compiled in a review. Temperature-programmed desorption/reaction methods (the latter using mass-spectrometry detection and also thermogravimetric analyzer (TGA)) were utilized to study CO adsorption/-desorption on supported and unsupported iron catalysts. Molecular and dissociative adsorptions of CO occur on iron catalysts at 25-150 C. The amounts adsorbed and bond strengths of adsorption are influenced by supports and promoters. That CO adsorbs dissociatively on polycrystalline Fe at temperatures well below those of FT reaction indicates that CO dissociation is facile and unlikely to be the rate-limiting step during FTS. Carbonaceous species formed after FT reaction for only 5 minutes at 200 C were initially hydrogenated under mild, isothermal condition (200 C and 1 atm), followed by TPH to 800 C. During the mild, isothermal hydrogenation, only about 0.1-0.2 mL of atomic carbon is apparently removed, while during TPH to 800 C multilayer equivalents of atomic, polymeric, carbidic, and graphitic carbons are removed. Rates of CO conversion on alumina-supported iron catalysts at 220-260 C and 20 atm are correlated well by a Langmuir-Hinshelwood expression, derived assuming carbon hydrogenation to CH and OH recombination to water to be rate-determining steps. In the coming year, studies will focus on quantitative determination of the rates of kinetically-relevant ...
Date: March 3, 2006
Creator: Mavrikakis, Manos; Dumesic, James A.; Gokhale, Amit A.; Nabar, Rahul P.; Bartholomew, Calvin H.; Zou, Hu et al.
Partner: UNT Libraries Government Documents Department

Prediction of Frictional Pressure Drop During Water Permeation Through Packed Beds of Granular Particulates

Description: A methodology has been developed based on the Kozeny-Carman equation to predict frictional pressure drops during water permeation of packed columns containing essentially noncompressible, but highly irregular particles. The resulting model accurately predicts pressure drop as a function of liquid flow rate and resin particle size for this system. A total of five particle sieve cuts across the range -20 to +70 mesh were utilized for testing using deionized water as the mobile phase. The Rosin-Rammler equation was used to fit the raw particle size data (wet sieve analysis) for the as-received resin sample and generate a continuous cumulative distribution function based on weight percent passing through the sieve. Probability distribution functions were calculated from the cumulative distribution for each particle sieve cut tested. Nine particle diameter definitions (i.e., number mean, volume mean, etc.) were then selected from the distribution function for each sample to represent the average spherically-equivalent particle diameter as input to the Kozeny-Carman equation. Nonlinear least squares optimization of the normalized pressure drop residuals were performed by parameter estimation of particle shape factor and bed porosity for all samples simultaneously using a given average particle diameter definition. Good fits to the full experimental data set were obtained when utilizing the number mean and the number median diameters. However, the shape factor and porosity values of 0.88 and 0.40, respectively, obtained from fitting the data using the number mean diameter were more consistent with experimental observations.
Date: October 25, 2005
Creator: KING, WILLIAM D.; ALEMAN, SEBASTIAN E.; HAMM, L. LARRY & PETTIS, MYRA A.
Partner: UNT Libraries Government Documents Department

Moisture Transport in Silica Gel Packed Beds: II. Experimental Study

Description: Experiments have been performed to obtain the transient response of a thin adiabatic packed bed of silica gel after a step change in inlet air conditions, comparisons are made with predictions using a solid-side resistance model and a pseudo-gas-side controlled model and better agreement obtained with the former model.
Date: August 1, 1986
Creator: Pesaran, A. A. & Mills, A. F.
Partner: UNT Libraries Government Documents Department