Concentrated CO2 Stream Research Articles

Studies on the redox reaction kinetics of Fe2O3–CuO/Al2O3 and Fe2O3/TiO2 oxygen carriers

This paper contains the results of research work on chemical looping combustion (CLC). CLC is one of the most promising combustion technologies and has the main advantage of the production of a concentrated CO2 stream, which is obtained after water condensation without any energy penalty for CO2 separation. The objective of this work was to study the kinetics of both the reduction and oxidation reactions for the selected bi-metallic Fe2O3–CuO/Al2O3 and mono-metallic Fe2O3/TiO2 oxygen carriers. Based on our previous CLC research results, the most promising oxygen carriers were selected for the analysis. Tests were performed at isothermal conditions (600–950°C) in multiple redox cycles using a thermo-gravimetric analyzer (Netzsch STA 409 PG Luxx). For the reduction, 3% H2 in Ar was used, and for the oxidation cycle, air was used. The activation energy and the pre-exponential factor were determined, and the reaction model was selected. The F1 (volumetric model) and R3 (shrinking core model) were suitable models for Fe2O3/TiO2, with Ea equal to 33.8kJ/mole where F1 and D3 (3-dimensional diffusion model), were suitable for Fe2O3–CuO/Al2O3 reduction reaction kinetics decryption with Ea=42.6kJ/mole (F1 model). The best fits for oxidation reaction was obtained for R3 model, and F1 was also good for Fe2O3/TiO2 oxygen carrier. The chemical looping oxygen uncoupling (CLOU) effect of Fe2O3–CuO/Al2O3 material is the best described by the F1 or D3 models. The CLOU effect activation energy is equal to 22.2kJ/mole.

Kinetics of the reduction of hematite (Fe2O3) by methane (CH4) during chemical looping combustion: A global mechanism

Chemical-looping combustion (CLC) has emerged as a promising technology for fossil fuel combustion which produces a sequestration ready concentrated CO2 stream in power production. A CLC system is composed with two reactors, an air and a fuel reactor. An oxygen carrier such as hematite (94%Fe2O3) circulates between the reactors, which transfers the oxygen necessary for the fuel combustion from the air to the fuel. An important issue for the CLC process is the selection of metal oxide as oxygen carrier, since it must retain its reactivity through many cycles. The primary objective of this work is to develop a global mechanism with respective kinetics rate parameters such that CFD simulations can be performed for large systems. In this study, thermogravimetric analysis (TGA) of the reduction of hematite (Fe2O3) in a continuous stream of CH4 (15%, 20%, and 35%) was conducted at temperatures ranging from 700 to 825°C over ten reduction cycles. The mass spectroscopy analysis of product gas indicated the presence of CO2 and H2O at the early stage of reaction and H2 and CO at the final stage of reactions. A kinetic model based on two parallel reactions, (1) first-order irreversible rate kinetics and (2) Avrami equation describing nucleation and growth processes, was applied to the reduction data. It was found, that the reaction rates for both reactions increase with, both, temperature and the methane concentration in inlet gas.

Parametric behavior of a CO2 capture process: CFD simulation of solid-sorbent CO2 absorption in a riser reactor

The National Energy Technology Laboratory as well as other institutions are developing a variety of technology concepts as alternatives to liquid-amine based absorption processes for post-combustion CO2 capture from large sources such as utility power generation facilities. At low temperature, many of these advanced dry processes are based upon sorbents composed of supported polyamines. In the dry-sorbent process, CO2 from flue gas is absorbed in one reactor, followed by separation of the carbonated particles from the de-carbonated flue gas and in a second reactor the sorbent is regenerated, creating a concentrated stream of pure CO2 for sequestration. In this work, the adsorber performance is simulated using multiphase computational fluid dynamics with chemistry and heat transfer. The three-dimension geometry is based on the lower mixing section of a riser from a recently operated CO2 capture test unit. An eight point test matrix was used to explore the behavior and performance of the riser adsorber with respect to solids circulation rate, gas flow rate and heat removal. It is shown that CO2 adsorption increases with an increase in the solids flow, decreases for an increase in the gas flow. The reactor performance can be summarized as a function of the molar sorbent to CO2 ratio entering the reactor with an R2 value of 0.9985.

Application of the Moving-Bed Chemical Looping Process for High Methane Conversion

The syngas chemical looping (SCL) process has been demonstrated at The Ohio State University for the conversion of gaseous fuels, such as natural gas and syngas, to sequestration-ready carbon dioxide (CO2) and high-purity hydrogen (H2) in a 25 kWth sub-pilot-scale unit operation. The present work focuses on parametric studies of the unique moving-bed reducer reactor operation for the conversion of methane to a concentrated stream of CO2. The variables studied include the reactor operating temperature, the gas hourly space velocity (GHSV), and the oxygen carrier/methane mass flow ratio. The results show that nearly full methane conversion (∼98%) can be achieved in the process with a GHSV of 395 h–1. Additionally, the post experiment oxygen-carrier analysis indicated that the oxygen-carrier conversion reached nearly 50%. Comparatively, the resulting oxygen-carrier conversion for the moving-bed reducer design is nearly 5 times greater than that theoretically achievable in a fluidized-bed reducer. The oxygen-carrier conversion profile along the height of the bed indicates that the conversion from Fe3O4 to FeO occurs at a much faster rate than the conversion from FeO to Fe in the reactor system. A multi-stage equilibrium simulation model for the reducer performance was developed using ASPEN Plus to compare against the experimental results. The simulation and experiment show a good match for oxygen-carrier and methane conversion results based on the testing conditions used. The parametric studies performed show promising results, indicating that the SCL technology can be used for the conversion of natural gas with CO2 readily separated.

Lacq-Rousse CO2 Capture and Storage Demonstration Pilot: Lessons Learnt From Two and a Half Years Monitoring

TOTAL conducts the first French pilot to demonstrate the technical feasibility and reliability of an integrated CO2 capture, transportation, injection and storage scheme from a boiler at a 30MWth scale. This pilot entails the conversion of an existing steam boiler into an oxy-fuel combustion unit, oxygen being used for combustion rather than air to obtain a more concentrated CO2 stream easier to capture. Then CO2 stream is compressed and conveyed via pipeline to the Rousse depleted gas field, 29 kilometers away, where it is injected into a deep carbonate reservoir. CO2 injection started earlier 2010 as all the proper official authorizations have been given. An appropriate monitoring plan is conducted to check the site integrity and storage performance. A preliminary baseline, conducted one year before the start of the injection is used as reference to detect any anomalous behavior which could be linked to any CO2 leakage. The aim of this paper is to present, the main lessons learned from the monitoring of the CCS pilot site of Lacq, after more than two years of injection and a year pre-injection baseline, in terms of monitoring-models offsets, security and risk analysis.

A Graphical Approach for Pinch-Based Source–Sink Matching and Sensitivity Analysis in Carbon Capture and Storage Systems

Carbon capture and storage (CCS) is regarded as an important interim technology for the reduction of carbon dioxide (CO2) emissions from large industrial facilities such as power plants and refineries. CCS involves capture of concentrated CO2 streams from point sources (industrial flue gases), followed by subsequent secure storage in an appropriate natural reservoir. Such reservoirs include various geological formations such as depleted oil or gas wells, inaccessible coal seams, and saline aquifers. In practice, such storage sites will have limitations on both CO2 storage capacity and injection rate, subject to geological characteristics. In this work, a graphical approach is proposed for matching multiple CO2 sources and storage sites (sinks) optimally within a predefined geographical region. The technique is developed on the basis of analogies with existing graphical pinch analysis approaches for the synthesis of industrial resource conservation networks (RCNs). Generalized principles for optimal CO2 so...

Process simulation and economic analysis of the Calcium Looping Process (CLP) for hydrogen and electricity production from coal and natural gas

The Calcium Looping Process (CLP) is being developed to facilitate carbon dioxide (CO2) capture during the production of hydrogen (H2) from syngas. The process integrates CO2, sulfur, and halide removal with the water–gas shift (WGS) reaction in a single-stage reactor. In the CLP, a regenerable calcium oxide (CaO) sorbent is used to chemically react with and remove CO2 and other acid gases from syngas at high temperature (i.e., 550–700°C). The removal of CO2 drives the WGS reaction forward via Le Chatelier’s principle, obviating the need for a WGS catalyst and enabling the production of high-purity H2. The spent sorbent is heated in a calciner to regenerate CaO for reuse in the process and to release a concentrated CO2 stream, which can be dried and sequestered. The regenerated sorbent is then reactivated in a hydrator, to improve its recyclability, before being reintroduced into the H2 production reactor.Techno-economic analyses were performed to evaluate the application of the CLP to a coal-to-H2 plant, a steam methane reforming (SMR) plant, and an integrated gasification-combined cycle (IGCC) plant, all including ⩾90% CO2 capture. In each case, use of the CLP resulted in a 9–12% reduction in the cost of H2 or cost of electricity when compared with the use of conventional CO2 capture and WGS technologies. The economic advantage afforded by the CLP is realized because of the large amount of high-quality heat produced in the process, which is recovered to raise steam for electricity generation. This heat arises from the combustion of supplemental fuel in the CLP calciner and from the exothermic CO2 removal, WGS, and hydration reactions, which are carried out at high temperature (i.e., ⩾500°C) in the CLP. As a result of recovering this heat, the CLP-based coal-to-H2 and SMR plants, which are designed to produce 26,000kg/h H2, necessarily co-produce 320MWe and 190MWe of net electric power, respectively. Although the CLP can reduce the cost of producing H2 from coal, the resulting cost is still about 26% greater than the cost of H2 produced from natural gas using conventional WGS and CO2 capture technologies, assuming coal and natural gas prices of $1.55/GJ and $6.21/GJ, respectively. The lowest cost of H2 with CO2 capture for these fuel prices is achieved by applying the CLP to an SMR plant.

Integration of Calcium and Chemical Looping Combustion using Composite CaO/CuO-Based Materials

Calcium looping cycles (CaL) and chemical looping combustion (CLC) are two new, developing technologies for reduction of CO(2) emissions from plants using fossil fuels for energy production, which are being intensively examined. Calcium looping is a two-stage process, which includes oxy-fuel combustion for sorbent regeneration, i.e., generation of a concentrated CO(2) stream. This paper discuss the development of composite materials which can use copper(II)-oxide (CuO) as an oxygen carrier to provide oxygen for the sorbent regeneration stage of calcium looping. In other words, the work presented here involves integration of calcium looping and chemical looping into a new class of postcombustion CO(2) capture processes designated as integrated CaL and CLC (CaL-CLC or Ca-Cu looping cycles) using composite pellets containing lime (CaO) and CuO together with the addition of calcium aluminate cement as a binder. Their activity was tested in a thermogravimetric analyzer (TGA) during calcination/reduction/oxidation/carbonation cycles. The calcination/reduction typically was performed in methane (CH(4)), and the oxidation/carbonation stage was carried out using a gas mixture containing both CO(2) and O(2). It was confirmed that the material synthesized is suitable for the proposed cycles; with the very favorable finding that reduction/oxidation of the oxygen carrier is complete. Various schemes for the Ca-Cu looping process have been explored here that would be compatible with these new composite materials, along with some different possibilities for flow directions among carbonator, calciner, and air reactor.

Methane Oxycombustion for Low CO2 Cycles: Blowoff Measurements and Analysis

Increasing concerns about climate change have encouraged interest in zero-CO2 emission hydrocarbon combustion techniques. In one approach, nitrogen is removed from the combustion air and replaced with another diluent, typically carbon dioxide or steam. In this way, formation of nitrogen oxides is prevented and the exhaust stream can be separated into concentrated CO2 and water by a simple condensation process. The concentrated CO2 stream can then be sequestered or used for enhanced oil recovery. Burning fuels in an O2/CO2 diluent raises new combustion opportunities and challenges for both emissions and operability: this study focuses on the latter aspect. CH4/O2/CO2 flames have slower chemical kinetics than methane-air flames and as such, flame stability is more problematic as they are easier to blow off. This issue was investigated experimentally by characterizing the stability boundaries of a swirl stabilized combustor. Near stoichiometric CO2 and N2 diluted methane/oxygen flames were considered and compared with lean methane/air flames. Numerical modeling of chemical kinetics was also performed to analyze the dependence of laminar flame speeds and extinction strain rates upon dilution by different species and to develop correlations for blowoff boundaries. Finally, blowoff trends at high pressure were extrapolated from atmospheric pressure data to simulate conditions closer to those of gas turbines.

The site monitoring of the Lacq industrial CCS reference project

Abstract TOTAL conducts the first French pilot to demonstrate the technical feasibility and reliability of an integrated CO2 capture, transportation, injection and storage scheme from a boiler at a 1/10th reduced scale of an industrial project. This pilot entails the conversion of an existing steam boiler into an oxy-fuel combustion unit, oxygen being used for combustion rather than air to obtain a more concentrated CO2 stream easier to capture. Then, CO2 stream is compressed and conveyed via pipeline to the Rousse depleted gas field, 30 kilometers away, where it is injected into a deep carbonate reservoir. CO2 injection has started early 2010 as all the proper official authorizations have been given. Those authorizations concern two years of injection and three years of post injection observation. An appropriate monitoring plan was designed to check the integrity of the site, to compare the CO2 behavior as it is planned and to get information to calibrate tools and models. This paper details the monitoring program: continuous measurements through permanent sensors, such as microseismicity or reservoir behavior with pressure and temperature data, and periodic surveys mainly for environmental purposes such as the groundwater quality and the surface water quality within the injection site catchment area and the fauna and the flora biodiversity.

Efficiency of hydrogen recovery from reformate with a polymer electrolyte hydrogen pump

The energy efficiency of hydrogen recovery from mixtures of CO2 ,H 2O, and H2 by a polymer electrolyte hydrogen pump (PEHP) has been evaluated. The PEHP pumps protons across the polymer electrolyte, producing [99.99% pure H2 and a concentrated CO2 stream. Single stage PEHP experiments recovered 65% of the hydrogen with an energy efficiency of 50%. The energy efficiency is limited by hydrogen mass transport across the porous gas diffusion electrode. The mass transport resistance for hydrogen increases as H2 is depleted from the CO2/H2 mixture by the PEHP. Analysis shows that a multistage PEHP with fixed applied potential difference can recover [90% of the hydrogen with an energy efficiency of 75%, whereas a novel multistage PEHP design with a programmed voltage profile can achieve [90% energy efficiency with [98% hydrogen recovery. V C 2010 American Institute of Chemical Engineers AIChE J, 57: 1767–1779, 2011

Chemical‐looping combustion process: Kinetics and mathematical modeling

AbstractChemical Looping Combustion technology involves circulating a metal oxide between a fuel zone where methane reacts under anaerobic conditions to produce a concentrated stream of CO2 and water and an oxygen rich environment where the metal is reoxidized. Although the needs for electrical power generation drive the process to high temperatures, lower temperatures (600–800°C) are sufficient for industrial processes such as refineries. In this paper, we investigate the transient kinetics of NiO carriers in the temperature range of 600 to 900°C in both a fixed bed microreactor (WHSV = 2‐4 g CH4/h/g oxygen carrier) and a fluid bed reactor (WHSV = 0.014‐0.14 g CH4/h per g oxygen carrier). Complete methane conversion is achieved in the fluid bed for several minutes. In the microreactor, the methane conversion reaches a maximum after an initial induction period of less than 10 s. Both CO2 and H2O yields are highest during this induction period. As the oxygen is consumed, methane conversion drops and both CO and H2 yields increase, whereas the CO2 and H2O concentrations decrease. The kinetics parameter of the gas–solids reactions (reduction of NiO with CH4, H2, and CO) together with catalytic reactions (methane reforming, methanation, shift, and gasification) were estimated using experimental data obtained on the fixed bed microreactor. Then, the kinetic expressions were combined with a detailed hydrodynamic model to successfully simulate the comportment of the fluidized bed reactor. © 2010 American Institute of Chemical Engineers AIChE J, 2010

Simulation of an Oxygen Membrane-Based Gas Turbine Power Plant: Dynamic Regimes with Operational and Material Constraints

This paper investigates the transient behavior of a natural gas-fired power plant for CO2 capture that incorporates mixed-conducting membranes for integrated air separation. The membranes are part of a reactor system that replaces the combustor in a conventional gas turbine power plant. A highly concentrated CO2 stream can then be produced. The membrane modules and heat exchangers in the membrane reactor were based on spatially distributed parameter models. For the turbomachinery components, performance maps were implemented. Operational and material constraints were emphasized to avoid process conditions that could lead to instability and extensive stresses. Two load-control strategies were considered for the power plant with a gas turbine operating at constant rotational speed. In the first load-control strategy, variable guide vanes in the gas turbine compressor were used to manipulate the mass flow of air entering the gas turbine compressor. This degree of freedom was used to control the turbine exit temperature. In the second load-control strategy, variable guide vanes were not used, and the turbine exit temperature was allowed to vary. For both load-control strategies, the mean solid-wall temperature of the membrane modules was maintained close to the design value. Simulation reveals that the membrane-based gas turbine power plant exhibits rather slow dynamics; fast load following was hence difficult while maintaining stable operation. Comparing the two load-control strategies, load reduction with variable air flow rate and controlled turbine exit temperature was found to be superior because of the considerably higher and faster load reduction capability, increased stability of the catalytic combustors in the membrane reactor, and higher power plant efficiencies.

Nuclear powered CO2 capture from the atmosphere

AbstractA process for capturing CO2 from the atmosphere was recently proposed. This process uses a closed cycle of sodium and calcium hydroxide, carbonate, and oxide transformations to capture dilute CO2 from the atmosphere and to generate a concentrated stream of CO2 that is amenable to sequestration or subsequent chemical transformations. In one of the process steps, a fossil‐fueled lime kiln is needed, which reduces the net CO2 capture of the process. It is proposed to replace the fossil‐fueled lime kiln with a modified kiln heated by a high‐temperature nuclear reactor. This will have the effect of eliminating the use of fossil fuels for the process and increasing the net CO2 capture. Although the process is suitable to support sequestration, the use of a nuclear power source for the process provides additional capabilities, and the captured CO2 may be combined with nuclear‐produced hydrogen to manufacture liquid fuels via Fischer‐Tropsch synthesis or other technologies. Conceivably, such plants would be carbon‐neutral and could be placed virtually anywhere without being tied to fossil fuel sources or geological sequestration sites. © 2009 American Institute of Chemical Engineers Environ Prog, 2009

The Oxy-combustion burner development for the CO2 pilot at Lacq

Steam demand is increasing for Oil & Gas projects, and in particular oil sands and extra-heavy oils thermal recovery schemes. Use of oil residues and bitumen can be a cost-effective solution for natural gas substitution in SAGD (Steam Assisted Gravity Drainage). However, use of such fuels gives rise to higher specific GHG emissions. Oxy-combustion technology is an elegant solution to this problem since oxygen allows complete combustion of very high viscosity and heavy fuels, and because it provides a concentrated CO2 stream, for easier Carbon Capture and Storage (CCS). Air Liquide has acquired over the last two decades extensive industrial experience of full oxy-combustion for the glass, metals, cement and waste treatment industries. This expertise and extensive scientific knowledge have been used to develop an innovative oxy-burner technology, specific to steam and power production applications. This oxy-burner technology presents novel and differentiating features, which will be described in this paper. In particular, it features a direct oxygen injection into the burner, without external mixing of oxygen with the flue gas recycle, which provides additional flue gas recycle rate flexibility, and enables a safe handling of the oxygen. Air Liquide has demonstrated the performance of this oxy-burner concept through downscaled (1 MW) oxy- combustion tests in a dedicated cold-wall test-rig with flue gas recycle. Total will retrofit the air-fired boiler at its Lacq CO2 Project (SW of France) with an intermediate size of this oxy- burner technology (four 8 MW oxy-burners). The paper presents: the innovative oxy-burner technology, its challenges and novelties, a description of the Air Liquide 1 MW oxy-combustion test rig and the test results obtained over a wide range of flue gas recycle rates, the integration of the oxy-combustion system into Total’s existing 30 MWth boiler.

Simulation of an oxygen membrane-based combined cycle power plant: part-load operation with operational and material constraints

This paper presents the design and part-load performance of a natural gas-fired oxy-combustion combined cycle power plant for CO2 capture. The combustion chamber of a conventional gas turbine was replaced by a membrane reactor, making it possible to obtain a highly concentrated CO2 stream for long-term storage. The focus was on power plant operation with a view to operational and material constraints of individual process components to ensure their proper performance and required lifetime. In this respect, the mixed-conducting membrane modules were of particular interest. Temperature as well as concentration limitations for CO2 and other chemical species narrowed the operating window. Other critical reactor components added further constraints. For part-load operation of the power plant, two load control strategies were analysed for the gas turbine operating at constant rotational speed. In the first load control strategy, variable guide vanes were used to manipulate the mass flow of air to the gas turbine compressor. This degree of freedom was used to control the turbine exit temperature. In the second control strategy, variable guide vanes were not used and the turbine exit temperature was allowed to vary. For both load control strategies, the mean solid-wall temperature of the membrane modules was maintained close to its design value, which led to improved stability. The load-control strategy using variable guide vanes was superior to the strategy without variable guide vanes due to higher combined cycle efficiencies and increased load-reduction capability. Moreover, the performance of the catalytic combustors in the membrane reactor, operating at near stoichiometric conditions, also improved as a result of increased oxygen concentrations at part-load operation. Relevant process components were based on spatially distributed conservation balances for energy, species, mass, and momentum. A stability diagram was incorporated into the membrane module model to investigate the risk of degradation. Performance maps were used for turbomachinery components.

Experimental Study of Oxy-Fuel Combustion and Sulfur Capture in a Mini-CFBC

Oxy-fuel technology uses effectively pure oxygen for fossil fuel combustion in order to obtain a highly concentrated CO2 stream, suitable for direct compression and sequestration. It is an effective technology to reduce greenhouse gas emissions to the atmosphere from large point sources such as power generation plants. Oxy-fuel FBC technology has the combined advantage of producing high CO2 concentration flue gas and allowing excellent fuel flexibility. In addition, with external cooling of the recirculated solids, the flue gas recirculation ratio can be reduced. CETC-Ottawa has carried out oxy-fuel fluidized bed combustion with flue gas recirculation on its modified mini-CFBC. The mini-CFBC has an internal diameter of 100 mm and internal height of 5000 mm. Both bituminous and sub-bituminous coals were fired. Limestone was premixed with coal and fed to the mini-CFBC. Recirculated solids were cooled in the return leg of the mini-CFBC. The bed temperature was controlled at about 850 °C, while the oxygen concentration in the primary gas was ∼25% and in the secondary gas was ∼50%. With flue gas recycle, the CO2 concentration in the flue gas reached 82–90%. Sulfur capture efficiency and CO and NOx concentrations were also measured and were all at acceptable levels. The transition from air firing to oxy-fuel firing was a fast and relatively smooth process, and operation of the mini-CFBC under oxy-fuel firing conditions was similar to that of air firing.

Demonstration of a Reheat Combustor for Power Production With CO2 Sequestration

Concerns about climate change have encouraged significant interest in concepts for ultralow or “zero”-emissions power generation systems. In a concept proposed by Clean Energy Systems, Inc., nitrogen is removed from the combustion air and replaced with steam diluent. In this way, formation of nitrogen oxides is prevented, and the exhaust stream can be separated into concentrated CO2 and water streams. The concentrated CO2 stream could then serve as input to a CO2 sequestration process. In this study, experimental data are reported from a full-scale combustion test using steam as the diluent in oxy-fuel combustion. This combustor represents the “reheat” combustion system in a steam cycle that uses a high and low-pressure steam expansion. The reheat combustor serves to raise the temperature of the low-pressure steam turbine inlet, similar to the reheat stage of a conventional steam power cycle. Unlike a conventional steam cycle, the reheat enthalpy is actually generated by oxy-fuel combustion in the steam flow. This paper reports on the unique design aspects of this combustor, as well as initial emissions and operating performance.

Dow to close pet plant in Pisticci, Italy

This paper evaluates the opportunities and associated costs for post-combustion capture at a world-scale complex refinery. It is concluded that it is technically feasible to apply post-combustion capture at such a refinery. The costs for capture and sequestration from a gasifier are calculated to be lowest at about 30 Euro per ton; this process currently already produces a concentrated CO2 stream. Next, the CO2 source most suited for capture appears to be a combined stack, but there are a number of other sources that may be targeted at comparable costs. In total these sources may form about 40% of the overall refinery emissions. Our evaluations show the costs of capture from such sources based on available amine technology will be in the range of 90–120 Euro per ton, which is about 3–4 times higher than the current carbon trading values. The capture of CO2 from a large amount of smaller CO2 sources will bring along even much higher costs. A high-level study of the CO2 emissions profile of a number of Shell refineries shows that, typically, up to 50% of the emitted CO2 may be captured at similar costs. About 10–20% of concentrated CO2 associated with hydrogen manufacturing may be captured at lower costs. The remainder of emitted dilute CO2 will bring along significantly higher costs. Based on this study, it is concluded for the justification of the implementation of post-combustion capture at refineries, either a significant increase in carbon trading values, mandatory regulations, or a major technological break-through is required.

Deuterium and big bang nucleosynthesis

Hydrogen is produced in a redox chemical loop in which the oxygen atom is ‘stolen’ from water by a circulating solid based on iron oxides. In addition to the transportation of oxygen, the circulating solid, having a high heat capacity, ensures heat transfer in the cycle. Water is split by the oxidation of FeO to Fe3O4, this producing H2 and leaving the oxygen of the water in the solid. The back-reduction to FeO occurs in a separate reactor using natural gas, the structural oxygen producing a concentrated CO2 stream. The exothermicity of the water splitting does not balance the endothermicity of the flameless combustion of natural gas with Fe3O4. Hence, before this combustion is carried out, super-oxidation by air of some or all of the Fe3O4 to Fe2O3, carried out in a third reactor, supplies the heat required for the reaction enthalpy balance as well as the energy required by the plant energetic balance. In this “One-Step Hydrogen” process, intrinsically separated streams of hydrogen and storage-ready CO2, suitable for Enhanced Oil Recovery (EOR) applications, are produced. Thus, any upstream (N2O2 separation) or downstream (transformations and CO2 capture) energy intensive steps are avoided. The use of fluidized bed technology allows also the management of the heat flows and of thermodynamic equilibria constraints and ensures the most efficient heat exchange in the loop.The chosen circulating solid consists of 30% Fe on an Mg-Al2O3 spinel; this is perfectly suitable with respect to its structural and mechanical properties for use in a commercial fluidized bed technology.Management of the amount of super-oxidation allows one to target the OSH technology to produce hydrogen (with or without steam export), co-produce hydrogen and electric power, or even to supply only energy by integrating this process into a hydrogen-powered combined cycle energy production plant (H2CC). In comparison with the current technologies with CO2 recovery, the one-step process described here shows better efficiencies and much better environmental performance because CO2 removal is virtually complete.