Armin D. Ebner

State-of-the-art Adsorption and Membrane Separation Processes for Carbon Dioxide Production from Carbon Dioxide Emitting Industries

Abstract With the growing concern about global warming placing greater demands on improving energy efficiency and reducing CO2 emissions, the need for improving the energy intensive, separation processes involving CO2 is well recognized. The US Department of Energy estimates that the separation of CO2 represents 75% of the cost associated with its separation, storage, transport, and sequestration operations. Hence, energy efficient, CO2 separation technologies with improved economics are needed for industrial processing and for future options to capture and concentrate CO2 for reuse or sequestration. The overall goal of this review is to foster the development of new adsorption and membrane technologies to improve manufacturing efficiency and reduce CO2 emissions. This study focuses on the power, petrochemical, and other CO2 emitting industries, and provides a detailed review of the current commercial CO2 separation technologies, i.e., absorption, adsorption, membrane, and cryogenic, an overview of the emerging adsorption and membrane technologies for CO2 separation, and both near and long term recommendations for future research on adsorption and membrane technologies. Flow sheets of the principal CO2 producing processes are provided for guidance and new conceptual flow sheets with ideas on the placement of CO2 separations technologies have also been devised.

Implementing a hydrogen economy

President Bush, during his State of the Union Address this year, pronounced a

State‐of‐the‐Art Adsorption and Membrane Separation Processes for Hydrogen Production in the Chemical and Petrochemical Industries

1.2 billion jump-start to the hydrogen economy. The move would represent not only freedom from US-dependence on foreign oil, which is a national security issue, but also a necessary and gargantuan step toward improving the environment by reducing the amount of carbon dioxide released into the atmosphere. However, hydrogen storage is proving to be one of the most important issues and potentially biggest roadblock for the implementation of a hydrogen economy. Of the three options that exist for storing hydrogen, in a solid, liquid, or gaseous state, the former is becoming accepted as the only method potentially able to meet the gravimetric and volumetric densities of the recently announced FreedomCar goals; and of all known hydrogen storage materials, complex hydrides may be the only hope. In recent years, months, weeks, and even days, it has become increasingly clear that hydrogen as an energy carrier is ‘in’ and carbonaceous fuels are ‘out’1. The hydrogen economy is coming, with the impetus to transform our fossil energy-based society, which inevitably will cease to exist, into a renewable energy-based one2. However, this transformation will not occur overnight. It may take several decades to realize a hydrogen economy. In the meantime, research and development is necessary to ensure that the implementation of the hydrogen economy is completely seamless, with essentially no disruption of the day-to-day activities of the global economy. The world has taken on a monumental, but not insurmountable, task of transforming from carbonaceous to renewable fuels, with clean burning, carbon dioxide-free hydrogen as the logical choice.

Elucidation of the ion binding mechanism in heterogeneous carbon-composite adsorbents

Abstract This review on the use of adsorption and membrane technologies in H2 production is directed toward the chemical and petrochemical industries. The growing requirements for H2 in chemical manufacturing, petroleum refining, and the newly emerging clean energy concepts will place greater demands on sourcing, production capacity and supplies of H2. Currently, about 41 MM tons/yr of H2 is produced worldwide, with 80% of it being produced from natural gas by steam reforming, partial oxidation and autothermal reforming. H2 is used commercially to produce CO, syngas, ammonia, methanol, and higher alcohols, urea and hydrochloric acid. It is also used in Fischer Tropsch reactions, as a reducing agent (metallurgy), and to upgrade petroleum products and oils (hydrogenation). It has been estimated that the reforming of natural gas to produce H2 consumes about 31,800 Btu/lb of H2 produced at 331 psig based on 35.5 MM tons/yr production. It is further estimated that 450 trillion Btu/yr could be saved with a 20% improvement in just the H2 separation and purification train after the H2 reformer. Clearly, with the judicious and further use of adsorption or membrane technology, which are both classified as low energy separation processes, energy savings could be readily achieved in a reasonable time frame. To assist in this endeavor of fostering the development of new adsorption and membrane technologies suitable for H2, CO and syngas production, the current industrial practice is summarized in terms of the key reforming and shift reactions and reactor conditions, along with the four most widely used separation techniques, i.e., absorption, adsorption, membrane, and cryogenic, to expose the typical conditions and unit processes involved in the reforming of methane. Since all of the reactions are reversible, the H2 or CO productivity in each one of them is limited by equilibrium, which certainly provides for process improvement. Hence, the goal of this review is to foster the development of adsorption and membrane technologies that will economically augment in the near term and completely revamp in the far term a typical H2, CO or syngas production plant that produces these gases from natural gas and hydrocarbon feedstocks. A review of the emerging literature concepts on evolving adsorption and membrane separations applicable to H2 production is provided, with an emphasis placed on where the state‐of‐the‐art is and where it needs to go. Recommendations for future research and development needs in adsorbent and membrane materials are discussed, and detailed performance requirements are provided. An emphasis is also placed on flow sheet design modification with adsorption or membrane units being added to existing plants for near term impact, and on new designs with complete flow sheet modification for new adsorption or membrane reactor/separators replacing current reactor and separator units in an existing plant for a longer term sustainable impact.

New Magnetic Field-Enhanced Process for the Treatment of Aqueous Wastes

Abstract A two-stage analysis of the mechanism of metal ion binding by a heterogeneous adsorbent was developed. In the first stage, a continuous proton affinity distribution was calculated from potentiometric titration data using the CONTIN method with a Langmuir kernel. Electrostatic effects were accounted for using a diffuse layer model. In the second stage, the parameters obtained from the continuous distribution function (i.e. the number of different types of surface sites, site densities and their protonation constants) were utilized in a discrete distribution to represent the adsorbent in surface complexation and double layer models using the GRFIT speciation code. This information on the surface groups was applied to metal ion potentiometric titration experiments to calculate the surface complexation equilibrium constants of the metal ions and hence elucidate the mechanism of ion binding to these sites. The proposed method was applied successfully to the adsorption of Sr and Cu ions on carbon-composite adsorbents, KAU-mod and SCN-mod. The continuous distribution method (CONTIN) revealed three types of surface sites within these carbon-composite adsorbents with pK values ranging between 3.5–4.1, 5.3–6.3 and 7.7–8.2. The analysis of the metal ion adsorption data using the GRFIT speciation code showed that only the first two surface sites were capable of forming surface complexes with the Sr ions, and that only the first site governed the adsorption of the Cu ions.

Feasibility and limitations of nanolevel high gradient magnetic separation

ABSTRACT A new magnetic adsorbent material, called magnetic polyamine-epichlorohydrin (MPE) resin, was prepared by attaching activated magnetite to the outer surface of polyamine-epichlorohydrin resin beads. Experiments were carried out in the presence of a 0.3-tesla magnetic field to investigate the removal of actinides (plutonium and americium) from pH 12 wastewater using this new resin. The results demonstrated that the MPE resin has a significantly enhanced capacity for actinides over conventional ferrite-based surface complexation adsorption processes (where no field is applied) and over traditional high-gradient magnetic separation (HGMS) processes that remove suspended particles. This enhancement was attributed to the presence and subsequent removal of suspended actinide nanoparticles through an HGMS effect, with the magnetite acting as a very effective HGMS element. A theoretical analysis verified this supposition by showing that under adequate pHs and particle-particle separations, the attractive...

On the use of the dual-process Langmuir model for correlating unary equilibria and predicting mixed-gas adsorption equilibria.

This work proposes a new separation concept denoted as nanolevel high gradient magnetic separation (HGMS) or magnetic adsorption. A magnetic heteroflocculation model describes the magnetic forces between two spherical particles with different sizes and magnetic properties, and reveals the feasibilities and limitations of nanolevel HGMS. The adsorbent particles, composed of antiferromagnetic magnetite, are modeled as large, immobile spheres on the order of 100–500 nm in radius. The adsorbate, paramagnetic colloidal Fe(OH)2 particles, are treated as freely diffusing small spheres on the order of 20–80 nm in radius. The model assumes that the magnetite particles are dispersed throughout a porous, nonmagnetic, solid matrix and that they are free of convective forces. The model also assumes that magnetic forces alone act on the Fe(OH)2 particles, opposed only by Brownian motion. When the magnetic force is attractive and overwhelms the randomizing Brownian force, adsorption occurs. The results from this model show the importance of the external field strength, the sizes of the adsorbent and adsorbate particles, and their magnetic properties in developing a practical nanolevel HGMS process.

HIGH-GRADIENT MAGNETIC SEPARATION FOR THE TREATMENT OF HIGH-LEVEL RADIOACTIVE WASTES

A new model has been developed for predicting mixed-gas adsorption equilibria from multicomponent gas mixtures based on the dual-process Langmuir (DPL) formulation. It predicts ideal, nonideal, and azeotropic adsorbed solution behavior from a knowledge of only single-component adsorption isotherms and the assertion that each binary pair in the gas mixture correlates in either a perfect positive (PP) or perfect negative (PN) fashion on each of the two Langmuir sites. The strictly PP and strictly PN formulations thus provide a simple means for determining distinct and absolute bounds of the behavior of each binary pair, and the PP or PN behavior can be confirmed by comparing predictions to binary experimental adsorption equilibria or from intuitive knowledge of binary pairwise adsorbate-adsorbent interactions. The extension to ternary and higher-order systems is straightforward on the basis of the pairwise additivity of the binary adsorbent-adsorbate interactions and two rules that logically restrict the combinations of PP and PN behaviors between binary pairs in a multicomponent system. Many ideal and nonideal binary systems and two ternary systems were tested against the DPL model. Each binary adsorbate-adsorbent pair exhibited either PP or PN behavior but nothing in between. This binary information was used successfully to predict ternary adsorption equilibria based on binary pairwise additivity. Overall, predictions from the DPL model were comparable to or significantly better than those from other models in the literature, revealing that its correlative and predictive powers are universally applicable. Because it is loading-explicit, simple to use, and also accurate, the DPL model may be one of the best equilibrium models to use in gas-phase adsorption process simulation.

Isolated swine heart ventricle perfusion model for implant assisted-magnetic drug targeting.

ABSTRACT Argonne National Laboratory is developing an open-gradient magnetic separation (OGMS) system to fractionate and remove nonglass-forming species from high-level radioactive wastes (HLW); however, to avoid clogging, OGMS may require high-gradient magnetic separation (HGMS) as a pretreatment to remove the most magnetic species from the HLW. In this study, the feasibility of using HGMS in the pretreatment of HLW was demonstrated. A HLW simulant of Hanfords C-103 tank waste, which contained precipitated hydroxides and oxides of Fe, Al, Si, and Ca, was used. Preliminary fractionation results from a 0.3-T bench-scale HGMS unit showed that a significant amount of Fe could be removed from the HLW simulant. Between 1 and 2% of the total Fe in the sludge was removed during each stage, with over 18.5% removed in the 13 stages that were carried out. Also, in each stage, the magnetically retained fraction contained about 20% more Fe than the untreated HLW; however, it also contained a significant amount of Si...

A comprehensive in vitro investigation of a portable magnetic separator device for human blood detoxification

An isolated swine heart ventricle perfusion model was developed and used under physiologically relevant conditions to study implant assisted-magnetic drug targeting (IA-MDT). A stent coil was fabricated from a ferromagnetic SS 430 wire and used to capture 100-nm diameter magnetite particles that mimicked magnetic drug carrier particles (MDCPs). Four key cases were studied: (1) no stent and no magnet (control), (2) no magnet but with a stent, (3) no stent but with a magnet (traditional MDT), and (4) with a stent and a magnet (IA-MDT). When applied, the magnetic field was fixed at 0.125T. The performance of the system was based on the capture efficiency (CE) of the magnetite nanoparticles. The experiments done in the absence of the magnetic field showed minimal retention of any nanoparticles whether the stent was present or not. The experiments done in the presence of the magnetic field showed a statistically significant increase in the retention of the nanoparticles, with a marked difference between the traditional and IA-MDT cases. Compared to the control case, in one case there was nearly an 11-fold increase in CE for the IA-MDT case compared to only a threefold increase in CE for the traditional MDT case. This enhanced performance by the IA-MDT case was typical of all the experiments. Histology images of the cross-section of the coronary artery revealed that the nanoparticles were captured mainly in the vicinity of the stent. Overall, the IA-MDT results from this work with actual tissue were very encouraging and similar to those obtained from other non-tissue and theoretical studies; but, they did point to the need for further studies of IA-MDT.