Roddie R. Judkins

A novel process and material for the separation of carbon dioxide and hydrogen sulfide gas mixtures

Abstract Carbon fiber composite molecular sieve (CFCMS) synthesis and characterization of the macro-, meso- and micropore structure are reported. CFCMS physical properties, including strength, thermal conductivity and electrical resistivity, are reported and the thermal conductivity of CFCMS compared with literature data for granular activated carbon (GAC) and packed beds of GAC. Adsorption studies, including isotherms for CO2 and CH4 at temperatures of 30, 60 and 100 °C on CFCMS samples activated to different burn-offs, are reported. High pressure adsorption data for CO2 and CH4 show that the CFCMS material has sufficient selectivity for CO2 over CH4 for a commercial separation. Breakthrough experiments were conducted for CO2/CH4 and H2S/H2 gas mixtures and the selective separation of CO2 and H2S was demonstrated. The electrical conductivity of our novel monolith was exploited to effect the rapid desorption of adsorbed gases. Desorption at low applied voltage was accompanied by a heating of the CFCMS to temperatures

Fossil energy applications of intermetallic alloys

This paper presents the history and results of the US Department of Energy, Office of Fossil Energy (FE), development effort on iron aluminide alloys and the status of research and development on ultrahigh temperature (well above 1000°C) intermetallic alloys. The outstanding (perhaps unequaled) sulfidation resistance of iron aluminide alloys, based on the Fe3Al composition, was the basis for initiation of an exploratory project to determine whether improvement in mechanical properties of iron aluminide alloys could be achieved. This was a high-risk venture but with significant payoff if successful, because sulfidation was a critical problem for applications of alloys in coal gasification systems. The exploratory project, which was conducted at Oak Ridge National Laborator (ORNL), was successful, and the program was expanded in both scope and participation. Several other national laboratories, industrial research organizations, and universities were involved. Iron aluminide development is now quite mature. Some of the research has transferred to line programs leading to product that will be used in advanced fossil energy systems. The first product to be commercialized for fossil energ applications was a porous metal filter developed jointly by ORNL and Pall Corporation. In addition to th coal gasification application, these filters are also being used in combustion systems. Several other commercial products are being pursued. Additional exploratory projects on intermetallic alloys have been initiated. These are also high risk activities, but, as with the iron aluminides, the payoff potential is great. The intermetallic alloys presently being investigated include a Cr2Ta-strengthened chromium alloy and a boron-modified molybdenum silicid based on Mo5Si3. The challenges with these alloys are to modify them to provide acceptable mechanical properties, including ductility and toughness, and corrosion resistance to allow them to be used in structure applications such as gas turbines.

Passive CO2 removal using a carbon fiber composite molecular sieve

Abstract Manufacture and characterization of a carbon fiber composite molecular sieve (CFCMS), and its efficacy as a CO 2 gas adsorbent are reported. The CFCMS consists of an isotropic pitch derived carbon fiber and a phenolic resin derived carbon binder. Activation (selective gasification) of the CFCMS creates microporosity in the carbon fibers, yielding high micropore volumes (>0.5 cm 3 /g) and BET surface areas (>1000 m 2 /g). Moreover, the CFCMS material is a rigid, strong, monolith with an open structure that allows the free-flow of fluids through the material. This combination of properties provides an adsorbent material that has several distinct advantages over granular adsorbents in gas separation systems such as pressure swing adsorption (PSA) units. The results of our initial evaluations of the CO 2 adsorption capacity and kinetics of CFCMS are reported. The room temperature CO 2 adsorption capacity of CFCMS is >120 mg of CO 2 per g of CFCMS. A proposed project is described that targets the development, over a three-year period, of a demonstration separation system based on CFCMS for the removal of CO 2 from a flue gas slip stream at a coal-fired power plant. The proposed program would be conducted jointly with industrial and utility partners.

A novel carbon fiber based material and separation technology

Abstract Our novel carbon fiber based adsorbent material shows preferential uptake of CO 2 over other gases. The material has a unique combination of properties, which include a large micropore volume, a large BET surface area, and electrical conductivity. These properties have been exploited to effect the separation of CO 2 from a model gas (CH 4 ). Enhanced desorption is achieved using an electrical current passed through the material at low voltage. The manufacture, characterization, and CO 2 adsorption behavior of the materials is reported here, along with our novel electrical swing separation technology.

Solid-state phase stabilities of relevance to metal dusting in coal gasifier environments

Thermochemical calculations involving some typical mixed-gas environments and temperatures of gasifiers were used to examine iron-based phase stabilities to assess the potential for metal dusting in coal gasification systems. The results indicated that Fe 3 C is only stable under conditions when certain reactions are suppressed and that FeO and Fe 0.877S tend to form instead of the carbide. Assuming Fe3C is a necessary step in the metal dusting of steels, there are therefore numerous coal gasification systems where this type of carbon-related degradation will not occur, particularly under conditions associated with higher oxygen and sulfur activities.

Iron-Aluminide Filters for Hot-Gas Cleanup

Iron aluminides have shown good to excellent high-temperature corrosion resistance in sulfur-bearing environments and thus have potential for use as the material of construction for metallic filters used to clean fossil-fuel-derived gases prior to their introduction into gas turbine systems. Consequently, a background for consideration of such alloys for filter applications is given in terms of a brief summary of the physical metallurgy and relevant high-temperature corrosion behavior of iron aluminides. In addition, preliminary characterization results on iron-aluminide filter elements exposed in test beds that simulate environments associated with advanced coal-fired energy production are presented. Although good corrosion resistance was found, there were minor to moderate strength reductions that did not necessarily scale with time. Little degradation in ductility was observed.Copyright

Control of corrosion in coal liquefaction plant fractionation columns

Severe corrosion has been encountered in fractionation columns at the solvent refined coal (SRC) pilot plants in Fort Lewis, Washington, and Wilsonville, Alabama, as well as at the H-Coal Pilot plant in Catlettsburg, Kentucky, and the Exxon Donor Solvent Pilot Plant in Baytown, Texas. At the SRC plants, corrosion rates as high as 25 mm per year (one inch per year) on carbon steel and 6.4 mm per year (250 mils per year) on type 18-8 stainless steels have been measured in the portions of the columns operating at 220 to 260 °C (428 to 500 °F). Less severe corrosion is generally found at temperatures outside this range. The severity of this corrosion is related to the chlorine content of the coal. Studies of this corrosion problem by Oak Ridge National Laboratory (ORNL) personnel included exposure of corrosion coupons in the pilot plant columns, analyses of liquids collected at the pilot plants, and performance of laboratory experiments. As a result of this work, we can specify alloys with adequate corrosion resistance for construction of fractionation columns, identify the chlorine-bearing compounds, and propose chlorine transport and corrosion mechanisms. Identification of the corrodent and its mechanisms enables us to suggest process changes to remove the corrodent and thereby to control the corrosion.

The LAJ Cycle: A New Combined-Cycle Fossil Fuel Power System

Oak Ridge National Laboratory (ORNL) has developed a novel system for combined-cycle power generation, called the LAJ cycle. This system could serve as a basis for the development of a new generation of high-efficiency combined cycles. In one of several possible configurations of the new combined-cycle fossil fuel power system, natural gas enters the system at 4.0 MPa and about 300 K, is heated and reformed, and is transferred to a turbine at 4.0 MPa and 1200 K. The gas expands in the turbine to 0.6 MPa and 800 K, and then flows successively to heat exchangers and a condenser-separator, after which it is separated into two gas streams, one containing principally CO with some CH4 and water vapor and the other containing pure H2 . The CO and H2 flow to separate fuel cells and undergo electrochemical oxidation with the concomitant production of electricity. Separate streams of water and carbon dioxide (CO2 ) are produced, making this cycle compatible with carbon mitigation strategies based on sequestration. Model calculations indicate combined-cycle efficiencies greater than 70% based on the lower heating value of natural gas. The high efficiencies realized result from a combination of the high-pressure natural gas reformate expansion and the highly efficient CO and H2 fuel cells. Most of the power derives from the fuel cells in the system.Copyright

Development of Ceramic Composite Hot-Gas Filters

A novel type of hot-gas filter based on a ceramic fiber-reinforced ceramic matrix was developed and extended to fullsize, 60-mm OD by 1.5-meter-long, candle filters. A commercially viable process for producing the filters was developed, and the filters are undergoing testing and demonstration throughout the world for applications in pressurized fluidized-bed combustion (PFBC) and integrated gasification combined cycle (IGCC) plants. Development activities at Oak Ridge National Laboratory (ORNL) and at the 3M Company, and testing at the Westinghouse Science and Technology Center (STC) are presented. Demonstration tests at the Tidd PFBC are underway. Issues identified during the testing and demonstration phases of the development are discussed. Resolution of the issues and the status of commercialization of the filters are described.

Carbon Formation and Metal Dusting in Hot-Gas Cleanup Systems of Coal Gasifiers

There are several possible materials/systems degradation modes that result from gasification environments with appreciable carbon activities. These processes, which are not necessarily mutually exclusive, include carbon deposition, carburization, metal dusting, and CO disintegration of refractories. Carbon formation on solid surfaces occurs by deposition from gases in which the carbon activity (a sub C) exceeds unity. The presence of a carbon layer CO can directly affect gasifier performance by restricting gas flow, particularly in the hot gas filter, creating debris (that may be deposited elsewhere in the system or that may cause erosive damage of downstream components), and/or changing the catalytic activity of surfaces.