CO2 Impurities Research Articles

Impact of CO2 impurity on CO2 compression, liquefaction and transportation

The impurities present in CO2 streams are extremely important for CO2 pipeline and ship transportation affecting, various aspects such as, the range of operation, safety considerations, fracture control, cracking, corrosion control, dispersion in the event of a release, fluid density, operating pressure, temperature and the quantity of CO2 that can be transported. The range and levels of potential impurities emitted from CO2 Capture facilities will differ between different power plant and industrial sources and also between the capture technologies installed at the source. However, the potential CO2 specifications that could enter the transport and storage systems, particularly from industrial sources, remain relatively under-researched. Therefore, it is of critical importance to improve the understanding of the effect of these potential impurities, which have not been widely studied, on CO2 compression, liquefaction and transportation in relevant conditions. IEAGHG has identified the need to study the effects of impurities in CO2 streams on CO2 compression, pipeline and shipping transportation. This study has been performed by a consortium led by Newcastle University and including the University of Edinburgh to address this need. The report: - Reviews the CO2 impurities that could be present from different CO2 capture technologies and develops twelve CO2 impurity scenario compositions for further analysis . - Evaluates these impurity scenarios for CO¬2 physical and transport properties. The properties that are investigated are the dew point, bubble point, melting point, density, Joule-Thomson coefficients, speed of sound, viscosity and thermal conductivity. Comprehensive tables and figures are provided for all of the scenarios investigated and for binary combinations of CO2 with impurity . - Evaluates the effects of the impurities on CO2 compression and liquefaction in terms of performance and energy requirements. - Identifies the effects of the impurities on the operating conditions for both pipeline and ship based transportation. - Evaluates the effect of the impurities on the selection of materials for pipeline and ship transportation.

IMPACTS: Economic Trade-offs for CO2 Impurity Specification

The IMPACTS project has a stated broad objective to develop the knowledge base of CO2 quality required for establishing norms and regulations to ensure safe and reliable design, construction and operation of CO2 pipelines and injection equipment, and safe long-term geological storage of CO2. More specifically for this paper, the project sets out to reveal the impacts of relevant impurities in the CO2 stream on the design, operation and costs of the capture, transport and storage infrastructure and to provide recommendations for optimized CO2 quality through techno-economic assessments (amongst other considerations). This paper gives an overview of the work being carried out to investigate the impact of CO2 quality in various areas including corrosion, water content in the CO2 stream and the injection and storage processes. The paper reports on the derived impacts of the above mentioned aspects of CO2 quality. These impacts are combined with estimates of the cost of measures to mitigate or prevent these impacts from affecting the operation of the CCS system, or of adapting of CCS system design. Thus, the impacts can be set out as a set of cost functions relating to Capex and Opex and including the effects of overall availability and process efficiency changes. A specifically designed CCS chain model is used to assess the impacts on a number of reference CCS chains, carrying out comparative economic trade-offs to both understand the full- chain whole-life economics of certain CO2 impurities at different levels and then to potentially optimize a purity specification for various sets of circumstances.

Modelling CO2 –Water Thermodynamics Using SPUNG Equation of State (EoS) Concept with Various Reference Fluids

Due to the continuous increase of CO2 emission to environment, the Carbon Capture and Storage (CCS) processes gained a very high importance in the last decades. One common CO2 impurity during various CCS processes is water. Therefore, the calculation of CO–water thermodynamic properties is a vital issue. This work preliminary investigates the accuracy of the extended corresponding states equation of state SPUNG using various reference fluids for the density and vapour liquid equilibrium (VLE) calculations of the CO2 - water system. The evaluation is done by comparing the numerical prediction with experimental data. The study is conducted at different mixture concentrations, and covering a broad range of conditions. The study is conducted using N2, O2, C1, C2, C3, and C4 as reference fluids. The results show an impact on density prediction. On the other hand, the VLE calculations exhibited very low sensitivity to varying reference fluids.

The influence of impurities on the transportation safety of an anthropogenic CO2 pipeline

Transportation safety is a key aspect of carbon capture and storage (CCS), which is a major technology used to reduce greenhouse gas emissions. Supercritical CO2 pipelines have been certified as an optimised choice for CO2 transportation. The results of this study show that the Peng–Robinson (PR) equation of state is recommended for analysis of the properties of supercritical CO2. The influence of nonpolar and polar impurities on the two-phase region and the location of the sharp discontinuity in the density are found by analysing the ternary phase equilibrium and physical parameters using the PR equation of state. A transitional area between the supercritical phase and the dense phase, where the density changes abruptly, is defined as the quasi-critical region. This study describes the functional relation between the temperature and the pressure that defines the quasi-critical line by calculating the partial derivative equations and then determines the effect of impurities on the quasi-critical region of transported CO2. Operational recommendations for pipeline transportation of flue CO2 are developed using a pipeline operated by Sinopec as an example, demonstrating the influence of impurities in flue CO2 on saturation pressure for control and prevention of fractures in CO2 pipelines.

Stability of Supported Amine Adsorbents to SO2 and NOx in Postcombustion CO2 Capture. 1. Single-Component Adsorption

Flue gases from coal-fired power plants typically contain not only CO2 but other acid-gas impurities such as SOx and NOx that can dramatically influence the CO2 capture efficiency. Whereas postcombustion CO2 capture by aminosilica materials has been extensively studied over the past few years because of their high equilibrium CO2 capacities, the performance of these materials under realistic conditions (in the presence of SOx, NOx, and O2) remains relatively unexplored. In this study, the degree of irreversible binding of SO2, NO, and NO2 to four supported amine adsorbents is evaluated to assess the SO2, NO, and NO2 adsorption capacities of aminosilica sorbents and their effects on the CO2 adsorption capacities. Adsorbents constructed using poly(ethyleneimine) and three different silane coupling agents (based on propyltrimethoxysilane linkers) with primary, secondary, and tertiary amines are evaluated. Under the experimental conditions used in this investigation, it is found that primary amines with high amine loadings displayed more affinity toward NO than their secondary and tertiary amine counterparts. However, overall, NO adsorption on the aminosilica adsorbents is low, and therefore, the CO2 capacities of the adsorbent materials exposed to NO remained almost unchanged after the exposure. In contrast, all materials showed a very high nitrogen dioxide adsorption capacity upon exposure to NO2. As a result, all adsorbents treated with NO2 exhibited a dramatic reduction in CO2 capacity, which corresponds to the deactivation of amine groups due to the irreversible binding of NO2. In addition, our results indicate that SO2 adsorbed significantly on supported amine adsorbents, resulting in a dramatic loss in CO2 capacity during CO2 capture from flue gas. With similar amine loadings, although secondary amines exhibited higher affinity to SO2, their CO2 capacity loss after exposure to SO2 is lower than that of primary amines, indicating that these materials are more stable in the presence of SO2, which implies that more SO2 desorbs from secondary amines during the desorption step. These results suggest that for silica-supported amine materials to be useful in practical CO2 capture applications, it is necessary to significantly reduce the SO2 and NO2 concentrations of the flue gas prior to the CO2 capture process. On the other hand, the capture efficiency of these materials does not change significantly in the presence of NO. This suggests that such materials might be promising for postcombustion CO2 capture from flue gas streams derived from natural gas combustion, as these streams typically contain reduced SO2 concentrations but can still have significant NOx concentrations.

Investigating the effect of salt and acid impurities in supercritical CO2 as relevant to the corrosion of carbon capture and storage pipelines

A series of corrosion exposure tests were performed in a supercritical CO2 environment used to represent the potential conditions for carbon capture and storage (CCS) pipelines. Impurities from various CO2 capture processes are potentially present, which segregate to the aqueous phase, hence combining with any free water present in the pipeline. Herein, salt (NaNO3, Na2SO4, NaCl) and acid (HNO3) impurities were added, along with 10g of water, to an autoclave at 7.6MPa and 50°C (supercritical CO2) for a 7 day steel specimen exposure. The tests conducted in supercritical CO2 were also compared with aqueous tests in atmospheric conditions. Weight loss and optical profilometry revealed that corrosion rates for all samples are significant, along with the potential for localised attack. The corrosion mechanism differs for each solution tested. The work herein contributes to a holistic appraisal of understanding the corrosion of CO2 pipelines.

Controlled-Freeze Technology for Processing Sour-Gas Resources

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper IPTC 16848, ’The Controlled-Freeze-Zone Technology for the Development of Sour-Gas Resources,’ by J.A. Valencia, SPE, and S.D. Kelman, SPE, ExxonMobil Upstream Research, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed. A single-step cryogenic-distillation process that removes carbon dioxide (CO2), hydrogen sulfide (H2S), and other impurities from natural gas has been developed by ExxonMobil. Rather than avoiding the freezing of CO2 at cryogenic temperatures, solidification is allowed to take place in a very controlled fashion. The technology has potential to separate CO2 and other impurities from natural gas and to discharge these contaminants as a high-pressure liquid stream. Introduction Meeting the demand for natural gas will require new resources. Many of those new resources will contain substantial amounts of CO2 and H2S that must be managed properly at the surface along with the produced hydrocarbons. Returning the CO2 and H2S to the subsurface for geosequestration or for use in enhanced oil recovery is emerging as a preferred option for management and disposal. A controlled-freeze technology can help meet that goal. Acid-Gas Injection When acid-gas injection is required for processing sour-gas resources, the treatment-process options shift toward releasing the acid gases from the natural gas at a relatively high pressure and as a liquid. Natural-gas fractionation can be designed to recover acid gas at high pressure and, at least partially in some cases, as a liquid. This method minimizes the power required for compression or pumping for reinjection of the waste acid gases. Fractionation-based processes rely on the relative volatility of the components in the sour-natural-gas stream. Bulk fractionation uses a single refrigerated tower for the bulk removal of acid-gas compounds, but the overhead sweet product still has a high residual-CO2 content of 15% or more. Higher purities would require lower temperatures, which in turn would lead to CO2 solidification occurring in the distillation column. Therefore, further treatment, usually with a solvent process, is needed to achieve the quality specifications normally required for natural-gas sales to transmission systems. The Ryan-Holmes process can achieve the required high-purity natural gas by use of a multiple-tower fractionation operation. This process uses a heavier-hydrocarbon liquid additive to suppress CO2 freezing during the distillation process. This hydrocarbon additive lowers the freezing point of CO2 in the first column and is recovered in later columns and recycled. While effective, this process requires that the recovered acid gas be vaporized during recovery of the hydrocarbon-liquid additive. Like the Ryan-Holmes process, the controlled-freeze process (CFP) is a single-step cryogenic-distillation process that is capable of achieving a high-quality sales-gas product. However, no hydrocarbon additive is required for the desired separation, so the second distillation step to recover the additive is not required. Also, the acid gas can be recovered as a high-pressure liquid, so pumping can be used for reinjection.

CO2 purification. Part I: Purification requirement review and the selection of impurities deep removal technologies

Depending on the reference power plant, the type of fuel and the capture method used, the CO2 product stream contains several impurities which may have negative impacts on pipeline transportation, geological storage and/or Enhanced Oil Recovery (EOR) applications. All negative impacts require setting stringent quality guidelines for each application and purifying the CO2 stream prior to exposing it to any of these applications.In this paper, the CO2 stream specifications and impurities from the conventional post-combustion capture technology are assessed. Furthermore, the CO2 restricted purification guidelines for pipeline transportation, EOR and geological storage are evaluated. Upon the comparison of the levels of impurities present in the CO2 stream and their restricted targets, it was found that the two major impurities which entail deep removal, due to operational concerns, are oxygen and water from 300ppmv to 10ppmv and 7.3% to 50ppmv, respectively. Moreover, a list of plausible technologies for oxygen and water removal is explored after which the selection of the most promising technologies is made. It was found that catalytic oxidation of hydrogen and refrigeration and condensation are the most promising technologies for oxygen and water removal respectively.

Exchange forms of binder-free granulated zeolites A and X: Synthesis and properties

Samples of crystalline aluminosilicates, the granules of which are intergrowths of zeolite A and X crystals with various degrees of exchange of Na+ cations for K+, Li+, H+, Mg2+, Ca2+, and La3+ in them, have been synthesized. The influence of the chemical nature and concentration of the exchange cation on the phase composition and the characteristics of the pore structure of the zeolite granules has been studied. The equilibrium adsorption capacities for H2O vapor and CO2 of binder-free granulated zeolites A and X in the Na, K, Li, H, Ca, Mg, and La-forms have been determined, and their adsorption activities in natural gas drying and removal of H2S and CO2 impurities in the dynamic mode at 20–25°C and atmosphere pressure have been examined. The relationships between the amount of the adsorbate and the type and concentration of exchange cations in the binder-free granulated zeolites A and X have been found.

Selective Oxidation of Chromium by O2 Impurities in CO2 During Initial Stages of Oxidation

This study shows that the corrosion behaviour of 12 wt% Cr steel in CO2 at 550 °C is determined in the first stage of oxidation by reaction with O2 impurities. Depending on the amount of theses impurities and the thermal ramp rate, selective oxidation of chromium could lead to the formation of a protective chromium-rich oxide. An oxidation model describing qualitatively the nature of the oxide layer formed in the initial period of oxidation is presented. From these observations, surface engineering processes for protecting 9–12 wt% chromium steels from fast corrosion rate have emerged.

Electrochemical Substitution of Sodium Ions in Tungsten Phosphate Glass with Protons

A novel technique was developed to inject proton carriers into phosphate glass. Sodium ions in the sodium tungsten phosphate glass were electrochemically substituted with protons. A glass plate with a deposited Pd anode was placed on the molten tin cathode and heated at a temperature below glass transition temperature under DC-bias in hydrogen containing atmosphere. Protons were injected from the palladium anode and substituted the sodium ions in the glass. The sodium ions migrated to the cathode and discharged to the molten tin cathode by capturing an electron from the external circuit. The atomic sodium dissolved into the cathode and reacted with CO2 impurities in the atmosphere resulting deposition of sodium carbonate on the tin cathode surface. After almost all of the sodium ions were discharged from the glass, the proton concentration in the glass reached 4.3 × 1021 cm−3. The proton conductivity was found to be 1 × 10−3 Scm−1 at 350°C. The injected protons were stable at temperatures below 400°C. The glass obtained by this technique behaves as a mixed conductor of protons and electrons with a proton transport number of 0.30. A possible means to suppress the electronic conductivity was discussed.

Acid Gases in CO2-rich Subsurface Geologic Environments

The analysis of species behavior involving dilute fluid environments has been crucial for the advance of modern solvation thermodynamics through molecular-based formalisms to guide the development of macroscopic regression tools in the description of fluid behavior and correlation of experimental data (Chialvo 2013). Dilute fluid environments involving geologic formations are of great theoretical and practical relevance regardless of the thermodynamic state conditions. The most challenging systems are those involving highly compressible and reactive confined environments, i.e., where small perturbations of pressure and/or temperature can trigger considerable density changes. This in turn can alter significantly the species solvation, their preferential solvation, and consequently, their reactivity with one another and with the surrounding mineral surfaces whose outcome is the modification of the substrate porosity and permeability, and ultimately, the integrity of the mineral substrates. Considering that changes in porosity and permeability resulting from dissolution and precipitation phenomena in confined environments are at the core of the aqueous CO2-mineral interactions, and that caprock integrity (e.g., sealing capacity) depends on these key parameters, it is imperative to gain fundamental understanding of the mineral-fluid interfacial phenomena and fluid-fluid equilibria under mineral confinement at subsurface conditions. In order to understand the potential effects of acid gases as contaminants of supercritical CO2 streams, in the next section we will discuss the thermodynamic behavior of CO2 fluid systems by addressing two crucial issues in the context of carbon capture, utilization and sequestration (CCUS) technologies: (i) Why should we consider (acid gas) CO2 impurities? and (ii) Why are CO2 fluid - mineral interactions of paramount relevance? ### Background on flue gas sources, composition, and CO2 - acid gases co-injection The control of anthropogenic greenhouse gases emissions in the atmosphere by means of their capture and sequestration in deep geological reservoirs has emerged as a potential technology for the middle- to long-term mitigation of the greenhouse effect …

Evaluation of CO2 Purification Requirements and the Selection of Processes for Impurities Deep Removal from the CO2 Product Stream

Depending on the reference power plant, the type of fuel and the capture method used, the CO2 product stream contains several impurities which may have a negative impact on pipeline transportation, geological storage and/or Enhanced Oil Recovery (EOR) applications. All negative impacts require setting stringent quality standards for each application and purifying the CO2 stream prior to exposing it to any of these applications.In this paper, the CO2 stream specifications and impurities from the conventional post-combustion capture technology are assessed. Furthermore, the CO2 restricted purification requirements for pipeline transportation, EOR and geological storage are evaluated. Upon the comparison of the levels of impurities present in the CO2 stream and their restricted targets, it was found that the two major impurities which entail deep removal, due to operational concerns, are oxygen and water from 300 ppmv to 10 ppmv and 7.3% to 50 ppmv respectively. Moreover, a list of plausible technologies for oxygen and water removal is explored after which the selection of the most promising technologies is made. It was found that catalytic oxidation of hydrogen and refrigeration and condensation are the most promising technologies for oxygen and water removal respectively.

Removal of sulfur compounds from natural gas for fuel cell applications using a sequential bed system

The development of an adsorbent system and process conditions for the removal of sulfur-compounds from natural gas at ambient conditions of temperature and pressure to meet the purity specifications required for use in the fuel processor of a PEM fuel cell is described. The sulfur compounds to be removed from the natural gas were H2S, dimethyl sulfide (DMS), carbonyl sulfide (COS), ethyl mercaptan (EM) and tertiary butyl mercaptan (TBM). The water content of natural gas was 120ppmw. Metal-exchanged zeolites (Ca–X and Na–X) and mixed metal oxides (of Cu–Mn and Fe–Mn) supported on alumina were used as adsorbents. Even though some of the adsorbents were active for the removal of particular sulfur compounds (Ca–X, for example, for the removal of DMS), none of them could remove all the sulfur impurities simultaneously. Multiple adsorbents are necessary. The choice of the combination of adsorbents depends on the type and relative amounts of the various sulfur compounds. The latter vary with the origin and source of the natural gas feedstock. The sequential location and quantity of the individual adsorbents in the total adsorbent bed is also a critical parameter. A sequential bed system comprising of Ca–X followed by Fe–Mn oxides had significant desulfurization capacity at 38°C, 15psig, and a natural gas space velocity of 6000h−1. This combination of adsorbents was also tolerant to the presence of water, aromatics, CO2, higher hydrocarbons and other such impurities sometimes present in the pipeline natural gas.

Purification of Commercial 2,3-Dimethyl Phenol Using Supercritical Fluid Extraction

The commercial value of phenols is often reduced due to the presence of colored impurities. Several conventional techniques have been used for the purification of phenols. However, conventional purification techniques are tedious and make use of hazardous and expensive organic solvents. In this study, we present a new method for purification of an aged-discolored (orange) commercial 2,3-dimethyl phenol (2,3-DMP) reagent (∼97%) using supercritical fluid CO2 (SCF CO2), as an extraction solvent. A supercritical fluid extraction (SFE)/purification apparatus was constructed and purification of the reagent under different extraction conditions was investigated. Based on the differential solubility of the 2,3-DMP and the impurities in SCF CO2, the commercial reagent was successfully purified by SFE; the purified 2,3-DMP was a white solid of high purity (>99.5%). The SFE method was also applied to purify a recently purchased batch of 2,3-DMP reagent. We found that the reagent purified by SFE was of a higher quality than a commercially available analytical standard.

Geochemical effects of impurities in CO2 on a sandstone reservoir

In most cases, CO2 captured from power plants or large industrial sources contains impurities. As purification of the stream is energy and cost intensive it is necessary to allow a certain level of impurities. The effects of impurities on (short- and long-term) geological storage are, however, uncertain. In this work, geochemical modelling with PHREEQC is performed to describe such effects on a sandstone reservoir (depleted gas field). The impact of two possible CO2 streams, originating from pre-combustion and oxyfuel capture technology is investigated. The streams contain O2, H2, CO, H2S, SO2, and/or NO as potential chemically reactive components. H2S, SO2 and NO are computed to oxidize, thereby forming sulfuric or nitric acid, and decrease the pH of the formation water. A low pH of the brine may be the result of extensive dissolution and dissociation, and therefore accumulation in the brine phase, especially close to the injection well. The impact of impurities on fast reacting minerals (short-term effects) is predicted to be relatively insignificant, due to the low amount of brine generally present in a gas field. On the long-term (equilibrium stage), impurities cause a slightly different mineralogy compared to pure CO2 injection. For the latter case a final increase in porosity of 3.5% is predicted whilst impurities (especially oxygen) could mitigate the porosity increase to zero due to the precipitation of minerals with higher molar volumes, like alunite and nontronite. Overall, the impurities do not seem to have a significant impact on the reservoir, even if accumulation in the brine takes place. The possible limiting effect of diffusion of impurities within the supercritical CO2 towards the brine has not been taken into account, even though the effect could be relevant. It could delay the effect of the impurities due to retarded dissolution. Further research should focus on this issue. Also the spatial effects and effects on different reservoir types, cap rock and well cement need to be investigated. © 2010 Elsevier Ltd. © 2011 Published by Elsevier Ltd.

Process configuration options for handling incomplete fuel conversion in CO2 capture: Case study on natural gas-fired CLC

“Innovative reactors” (based on chemical looping, membrane separation or sorption-enhanced processes) in power processes for CO2 capture appear to behave in such a way that some unconverted fuel could remain in the captured CO2-rich stream. This has the double drawback of adding impurities to the CO2 and of reducing the efficiency of the power cycle from which the CO2 was captured. The purpose of this paper is to illustrate the implications of some options for handling fractions of unconverted fuel in a captured CO2-rich stream. The selected case study is a chemical looping combustion (CLC) reactor integrated in a gas turbine cycle. Different process layouts are presented for the CO2 processing to reduce the amount of fuel components in the CO2, and process simulations are performed for fuel conversion rates in the range of 90–100%. Three different assumptions for the composition of the unconverted fuel were investigated (mixture of hydrocarbons, methane only, mixture of H2 and CO). Also the impact of the presence of fuel-derived N2 in the CO2 was investigated. Three different process solutions were studied for handling of the unconverted fuel: Separation of non-condensable gases in a distillation column, either for recirculation to the CLC reactor (fuel recovery method C) or for combustion in a duct burner (fuel recovery method C/B), or final oxidation of the unconverted fuel with oxygen from a cryogenic ASU (fuel recovery method O). Generally speaking, recovery of unconverted fuel for recirculation to the CLC reduction reactor through the use of a distillation column could have the double benefit of increasing the cycle efficiency and reducing the amount of impurities in the compressed CO2. It is however difficult to quantify the efficiency improvement, since it cannot be determined with the applied CLC reactor model how the reactor would respond to the introduction of a recirculation stream. The presence of H2 in the CO2 as well as the presence of N2 (or other inerts) in the fuel are found to be issues that merit further investigation. Also increasing rates of unconverted fuel in the CO2 due to oxygen carrier degradation could be an issue that merits further attention for CLC.

Calcium Looping Process (CLP) for Enhanced Noncatalytic Hydrogen Production with Integrated Carbon Dioxide Capture

The calcium looping process (CLP) is one of the clean coal technologies being developed for the production of hydrogen (H2) and electricity from coal-derived syngas. It integrates the water−gas shift reaction with in situ carbon dioxide (CO2), sulfur, and halide removal in a single-stage reactor. In the CLP, a regenerable calcium-based sorbent is used to react with and remove CO2, sulfur, and halide impurities from the synthesis gas during the production of H2. The removal of CO2 creates a favorable equilibrium and drives the water−gas shift reaction forward per Le Chatelier’s principle enabling the production of high-purity H2. In this investigation, the feasibility and optimum process conditions for the production of H2 in the absence of a water−gas shift catalyst have been described. Calcium oxide (CaO) sorbent has been found to enhance H2 yield to a large extent even in the absence of a water−gas shift catalyst. Specifically, at high pressures, high carbon monoxide (CO) conversion and H2 purity (>99%)...

Dynamic column breakthrough measurements for increasing LNG production efficiency with cryogenic pressure swing adsorption

The use of natural gas as a primary energy source is rapidly increasing on a global scale. To economically transport natural gas over long distances and satisfy this increase in demand, efficient production of liquefied natural gas (LNG) is required. Prior to the liquefaction of natural gas to produce LNG, it is highly desirable to remove N2 and CO2 impurities from the reservoir feed gas. Typically, CO2 is removed using a water-based amine solution. The regeneration of this amine solution is both energy intensive and costly. Furthermore, the amine solutions used are undesirable from health and environmental standpoints. Nitrogen is generally not removed prior to the liquefaction and must be separated from the end-flash vapor produced with the LNG. Conventionally this requires the construction of distillation towers operating at cryogenic conditions. In the environment of a cryogenic gas plant, adsorption-based processes for separating gases have several natural advantages over other methods. However, very little work has been done studying the efficiency of adsorption processes at the pressures and temperatures found in LNG plants. We have constructed a dynamic column breakthrough apparatus capable of measuring equilibrium adsorption and kinetics of adsorption at temperatures between 190 and 298 K and pressures to 1 MPa. This system was used to study the adsorption behaviour of N2, CO2 and CH4 on carbon molecular sieves and zeolites. This presentation will describe the measurement results and the challenges that were overcome as well as future plans to construct a larger scale apparatus.

Solid Oxide Fuel Cells: Operating Principles, Current Challenges, and the Role of Syngas

Syngas mixtures are excellent fuels for solid-oxide fuel cells (SOFC). Depending on the primary feedstock and the processing technology to produce the syngas, the composition (primarily mixtures of H2 and CO, but often including CH4, H2O, CO2, N2, and other impurities) can vary considerably. Thus, it is important to understand how SOFCs perform with alternative syngas mixtures. Syngas composition can affect materials selection, system design, and operating conditions. To assist understanding and interpreting performance, the article first reviews the basic principles governing SOFC chemistry and electrochemistry. The article also discusses alternative materials and system architectures, especially in the context of syngas fuels. A detailed computational model for a particular tubular, anode-supported, cell is used to compare SOFC performance using different syngas compositions. The syngas mixtures are derived from several processes, including partial oxidation (CPOx) or steam reforming of methane and dodecane, and gasification of coal or biomass.