High CO2 Partial Pressure Research Articles

Improved CO2 Sorption in Freeze-Dried Amine Functionalized Mesoporous Silica Sorbent

This work investigates the structural and CO2 sorption properties of amine-functionalized mesoporous silica prepared by a freeze-drying method. It was found that the freeze-dried samples delivered significantly higher CO2 sorption capacities up to a factor of 18 times as compared to samples prepared by the conventional oven-drying evaporation method. The improved performance of the freeze-drying method was attributed to a higher surface area and access to active amine sites for CO2 sorption. The freeze-dried samples also exhibited good stability at a relatively high sorption temperature (90 °C) and flue gas CO2 partial pressure (15 kPa). The freeze-drying method reached the best CO2 sorption capacity of 4.71 mmol g–1 for samples with 70 wt % amine loading. Higher loading (80 and 90 wt %) led to excess amine not being incorporated into the mesoporous silica structure, thus covering active sites and limiting CO2 diffusion.

Thermogravimetric analysis–mass spectrometry (TGA–MS) of hydromagnesite from Dujiali Lake in Tibet, China

Thermogravimetric analysis–mass spectrometry, in situ X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize hydromagnesite [Mg5(CO3)4(OH)2·4H2O] from Dujiali Lake in Tibet, China. This study describes the variations in the thermal decomposition mechanisms of hydromagnesite at varying heating rates and under either helium (He) or carbon dioxide (CO2) atmospheres. In a He atmosphere, only two decomposition stages were observed; the loss of the crystalline water followed by the combined dehydroxylation and decarbonation. However, under a CO2 atmosphere, the dehydroxylation and decarbonation occur separately as the inert CO2 gas prevents the decomposition of the MgCO3 component of hydromagnesite. Overall, the thermal decomposition is an endothermic process. A distinctly exothermic process occurs at about 540 °C under conditions of high partial pressure of CO2 or high heating rate and implies the crystallization of magnesite (MgCO3). We propose that the release of H2O and CO2 at different stages likely results from the complicated hydrogen bonds and different carbonate groups in the crystal structure of hydromagnesite.

Physical aging of ester-cross-linked hollow fiber membranes for natural gas separations and mitigation thereof

Like other glassy polymers, ester-cross-linked polyimide hollow fiber membranes can experience physical aging, which leads to some loss of permeation productivity. Highly quenched asymmetric structures are especially susceptible to such aging. To explore approaches to control physical aging, CO2 conditioning and continuous CO2/CH4 feed tests were studied in this work. A 100 psig CO2 conditioning overnight did not affect the aging of cross-linked hollow fibers significantly. However, periodical 15 psig CO2 conditioning reduced the CO2 permeance loss of cross-linked hollow fiber membranes by ~50%, compared to unconditioned ones during a 2300 h aging test. To further suppress physical aging, continuous exposure to CO2/CH4 feed typical of realistic continuous operations was used for hollow fiber samples. This protocol, in fact, reflects the realistic situation for use of asymmetric membranes that typically run under protracted steady state conditions. A 200 psia continuous 50/50 CO2/CH4 feed resulted in a CO2 permeance loss of only up to 3%, compared the 25% loss for samples without continuous mixed gas feed during a 400 h aging test. These results suggest that physical aging may be essentially quenched as long as the membrane remains contacted with a high CO2 partial pressure feed typical of actual aggressive feeds for which the membrane would be used. By inhibiting physical aging, periodic CO2 conditioning and continuous CO2/CH4 feed provide high performance of cross-linked hollow fiber membranes for natural gas separations.

Dynamic modelling, simulation and basic control of CO2 absorption based on high pressure pilot plant for natural gas treatment

The continuous exploration of new gas reserves along with the increase in the global power demand necessitates the development of less demanding technologies, especially in terms of energy minimization. However, the development of CO2-rich type of gas resources poses significant challenges in the sour gas treatment industry due to bulk CO2 contaminants and high overflowing pressure at the well- head. For the treatment of CO2 rich natural gas, reliable data at high CO2 partial pressure condition is very crucial and the insight of the transient conditions must be thoroughly studied to design a controlled process that can handle any disturbances that might arise in the future. This paper reports the dynamic modelling and basic regulatory control studies of a high-pressure absorption pilot plant, which is located at Universiti Teknologi PETRONAS (UTP), for CO2 removal using MEA solvent. Steady state simulation has been demonstrated using Aspen Plus utilizing both equilibrium and rate based approaches. Dynamic and control analysis is then carried out in Aspen Dynamic using a modified equilibrium stage model.

Effect of Buffer System on the Sulfide Stress Cracking Susceptibility of Low-Alloy Steel

The effects of a buffer system in test solution and CO2 partial pressure on sulfide stress cracking (SSC) susceptibility of low-alloy steel were investigated under pH 4.0 at 0.03 MPa H2S partial pressure. A double cantilever beam test was used to quantitatively evaluate SSC susceptibility. The corrosion rates and absorbed diffusible hydrogen concentration were also evaluated. Acetic acid/sodium acetate (acetate buffered solution) and carbonic acid/bicarbonate (bicarbonate buffered solution) buffered solutions were used as buffer systems in this study. From the results, in atmospheric pressure tests, KISSC values in bicarbonate buffered solutions were equivalent to or lower than those in acetate buffered solutions. In high CO2 partial pressure conditions, KISSC values in bicarbonate buffered solutions were much higher than those in acetate buffered solutions. At a high CO2 partial pressure and H2S partial pressure (pCO2/pH2S) ratio condition, hydrogen entry is considered to be greatly prevented by corrosion products probably containing amorphous iron carbonate. Presence of the corrosion product with high protectiveness produced in the high pCO2/pH2S ratio condition suggests the possibility that conventional test conditions using acetate buffered solutions are conservative or are equivalent test conditions for actual field conditions.

The Ca-looping process for CO2 capture and energy storage: role of nanoparticle technology

The calcium looping (CaL) process, based on the cyclic carbonation/calcination of CaO, has come into scene in the last years with a high potential to be used in large-scale technologies aimed at mitigating global warming. In the CaL process for CO2 capture, the CO2-loaded flue gas is used to fluidize a bed of CaO particles at temperatures around ~ 650 °C. The carbonated particles are then circulated into a calciner reactor wherein the CaO solids are regenerated at temperatures near ~ 950 °C under high CO2 concentration. Calcination at such harsh conditions causes a marked sintering and loss of reactivity of the regenerated CaO. This main drawback could be however compensated from the very low cost of natural CaO precursors such as limestone or dolomite. Another emerging application of the CaL process is thermochemical energy storage (TCES) in concentrated solar power (CSP) plants. Importantly, carbonation/calcination conditions to maximize the global CaL-CSP plant efficiency could differ radically from those used for CO2 capture. Thus, carbonation could be carried out at high temperatures under high CO2 partial pressure for maximum efficiency, whereas the solids could be calcined at relatively low temperatures in the absence of CO2 to promote calcination. Our work highlights the critical role of carbonation/calcination conditions on the performance of CaO derived from natural precursors. While conditions in the CaL process for CO2 capture lead to a severe CaO deactivation with the number of cycles, the same material may exhibit a high and stable conversion at optimum CaL-CSP conditions. Moreover, the type of CaL conditions influences critically the reaction kinetics, which plays a main role on the optimization of relevant operation parameters such as the residence time in the reactors. This paper is devoted to a brief review on the latest research activity in our group concerning these issues as well as the possible role of nanoparticle technology to enhance the activity of Ca-based materials at CaL conditions for CO2 capture and energy storage.

One-step production of C6\u2013C8 carboxylates by mixed culture solely grown on CO

BackgroundThis study aimed at producing C6–C8 medium-chain carboxylates (MCCAs) directly from gaseous CO using mixed culture. The yield and C2–C8 product composition were investigated when CO was continuously fed with gradually increasing partial pressure.ResultsThe maximal concentrations of n-caproate, n-heptylate, and n-caprylate were 1.892, 1.635, and 1.033 mmol L−1, which were achieved at the maximal production rates of 0.276, 0.442, and 0.112 mmol L−1 day−1, respectively. Microbial analysis revealed that long-term acclimation and high CO partial pressure were important to establish a CO-tolerant and CO-utilizing chain-elongating microbiome, rich in Acinetobacter, Alcaligenes, and Rhodobacteraceae and capable of forming MCCAs solely from CO.ConclusionsThese results demonstrated that carboxylate and syngas platform could be integrated in a shared growth vessel, and could be a promising one-step technique to convert gaseous syngas to preferable liquid biochemicals, thereby avoiding the necessity to coordinate syngas fermentation to short-chain carboxylates and short-to-medium-chain elongation. Thus, this method could provide an alternative solution for the utilization of waste-derived syngas and expand the resource of promising biofuels.

Carbon dioxide adsorption properties and adsorption/desorption kinetics of amine-functionalized KIT-6

An amine-functionalized adsorbent was prepared by loading pentaethylenehexamine (PEHA) into the pores of KIT-6 mesoporous silica. Nitrogen adsorption/desorption, thermogravimetric analysis, and X-ray powder diffraction were employed to analyze the structural properties of the prepared adsorbents. The results reveal that the pore size, pore volume, and surface area of the adsorbents decrease after PEHA loading in KIT-6, while the basic KIT-6 pore structure remains unchanged. The CO2 adsorption performance of amine-functionalized KIT-6 was studied by isothermal CO2 adsorption, adsorption/desorption cycle regeneration testing, and multiple cycle tests. The amount of CO2 absorbed increased with increasing temperature in the temperature range of 303–343 K, achieving a maximum adsorption capacity of 3.2 mmol/g-adsorbent at 343 K. For temperatures greater than 343 K, the adsorption capacity decreased with increasing temperature. The amount of CO2 adsorbed remained nearly constant after 10 adsorption/desorption cycles. The CO2 adsorption/desorption kinetics of the PEHA-impregnated KIT-6 were investigated using three kinetics models. The results indicate that the CO2 adsorption process by the amine-functionalized adsorbent is dominated by intra-particle diffusion, and the adsorption rate is restricted by the intra-particle diffusion process. In addition, high CO2 partial pressure facilitates the adsorption of CO2. The CO2 adsorption breakthrough curves obtained by the deactivation model were in good agreement with the results of this study. The adsorbents were regenerated by vacuum and temperature swing adsorption regeneration. The results indicate that increasing the desorption temperature is an effective means of reducing the regeneration time. The absolute value of the activation energy obtained from the Arrhenius equation for CO2 desorption was 81.992 kJ·mol−1, which was greater than that obtained for adsorption.

Evidence of formation of lithium compounds on FTU tiles and dust

Abstract Since 2006 lithium as an advanced plasma facing material has been tested on the Frascati Tokamak Upgrade (FTU). Lithium in the liquid phase acts both as plasma facing component, i.e. limiter, and plays also a role in plasma operation because by depositing a lithium film on the walls (lithization) oxygen is gettered. As in all deposition processes, even for the lithization, the presence of impurities in plasma phase strongly affects the properties of the deposited film. During the 2008 campaigns of FTU it was observed a strong release of carbon dioxide (during disruptions), resulting in successive serious difficulty of operation. In order to find the possible reactions occurred, we have analyzed the surface of two tiles of the toroidal limiter close to the Liquid Lithium Limiter (LLL). The presence of molybdenum oxides and carbides suggested that the surface temperatures could have exceeded 1000 K, likely during disruptions. lithium oxides and hydroxides have been found on the tiles and in the dust collected in the vessel, confirming the presence of LiO and LiOH and a not negligible concentration of Li 2 CO 3 especially at the LLL location. On the basis of the above results, we propose here a simple rationale, based on a two reactions mechanism, which can explain the formation of Li 2 CO 3 and its subsequent decomposition during disruption with release of CO 2 in the vessel. Admitting surface temperatures above 1000 K during a disruption, relatively high partial pressures of CO 2 are also predicted by the equilibrium constant for Li 2 CO 3 decomposition.

Determination and quantification of major climatic parameters influencing the CO2 of Lascaux Cave

High and low CO2 partial pressure (Pco2) levels can induce consequences to the internal system of a karstic cave. This then can further affect the state of the cave. Subsequently, speleothem growths and the walls with prehistorical paintings and engravings will be affected with either calcite dissolution or precipitation. Thus, pinpointing the major components of Pco2 is found indispensable. In this paper, a method is proposed in order to (1) identify the major components of the Pco2 and (2) quantify each specific contribution to the Pco2. Pco2, air temperature, air pressure, and water flow were measured from 2008 to 2010 in Lascaux Cave (Southwest of France). Pco2 varied from 0.62% (6200 ppm) in summer to 0.04% (400 ppm) in winter. We identified three major components: (1) seasonal: component A; (2) low frequency: component B; and (3) high frequency: component C. The method is applied to estimate the contribution of each component. Component A was modelled with a sinusoid curve fitted to the Pco2 measures. This component was subtracted from the measured Pco2. Then, from the remaining value of Pco2, Fourier transform, frequency filtering, and inverse Fourier transform were applied to separate high- and low-frequency components. As a result, the seasonal component A contributes 77% of the measured Pco2, while components B and C supply 13 and 11%, respectively. The three identified components have links with environmental parameters such as temperature, water flow, and atmospheric pressure. Hypotheses were proposed to describe these links. Knowledge on these aspects can help in cave management and protection specifically in answering the question: which parameter should be given more attention.

A warm or a cold early Earth? New insights from a 3-D climate-carbon model

Oxygen isotopes in marine cherts have been used to infer hot oceans during the Archean with temperatures between 60 °C (333 K) and 80 °C (353 K). Such climates are challenging for the early Earth warmed by the faint young Sun. The interpretation of the data has therefore been controversial. 1D climate modeling inferred that such hot climates would require very high levels of CO2 (2–6 bars). Previous carbon cycle modeling concluded that such stable hot climates were impossible and that the carbon cycle should lead to cold climates during the Hadean and the Archean. Here, we revisit the climate and carbon cycle of the early Earth at 3.8 Ga using a 3D climate-carbon model. We find that CO2 partial pressures of around 1 bar could have produced hot climates given a low land fraction and cloud feedback effects. However, such high CO2 partial pressures should not have been stable because of the weathering of terrestrial and oceanic basalts, producing an efficient stabilizing feedback. Moreover, the weathering of impact ejecta during the Late Heavy Bombardment (LHB) would have strongly reduced the CO2 partial pressure leading to cold climates and potentially snowball Earth events after large impacts. Our results therefore favor cold or temperate climates with global mean temperatures between around 8 °C (281 K) and 30 °C (303 K) and with 0.1–0.36 bar of CO2 for the late Hadean and early Archean. Finally, our model suggests that the carbon cycle was efficient for preserving clement conditions on the early Earth without necessarily requiring any other greenhouse gas or warming process.

Neutralisation of bauxite residue by carbon dioxide prior to acidic leaching for metal recovery

The present work considers the neutralisation of bauxite residue (red mud) with CO2 as a potential technology for reducing the acid consumption in the acidic leaching step for metal recovery. The pH of bauxite residue was reduced during neutralisation by the transformation of hydroxide ions to (hydrogen) carbonate ions. Neutralisation at high CO2 partial pressures and high temperatures reduces the alkalinity of the bauxite residue, but it leads to the stabilisation of silicate compounds such as cancrinite and grossular. After acidic leaching of the neutralised product with sulfuric acid, a decrease by 20% in the dissolution yield of Al, Fe, and Ti was observed, due to an insufficient amount of acid devoted to leaching as the transformation of calcite into bassanite and the high concentration of silicate compounds consumed part of the acid. Sc recovery by leaching of the highly neutralised bauxite residue was about 35wt%, which depends on Fe and Ti recovery. A positive correlation between La/Nd with Sc indicates that the recovery of La/Nd indirectly depends on the extraction of Fe/Ti, as Sc is chemically associated to these major metals.

High CO2 adsorption capacities in UiO type MOFs comprising heterocyclic ligand

For equilibrium-based CO2 capture, a high CO2 adsorption amount and working capacity of adsorbents to fulfill different conditions are desired. In this work, we investigated the CO2 adsorption in four UiO type MOFs comprising N, S, and O heterocyclic ligands. Our grand canonic Monte Carlo (GCMC) simulation results show that the CO2 adsorption amount in MOFs comprising N (UiO(BPYDC)), S (Zr-BTDC), and O (Zr-BFDC) heterocyclic ligands is higher than that in their parent MOF, UiO-67. The MOFs comprising O-heterocyclic ligand (Zr-BFDC) shows the highest CO2 adsorption amount, which is 4 times higher than that of UiO-67 at 1 bar. In addition, we also found that by changing the heteroatoms on the ligands, the CO2 working capacity can be precisely tuned. For post-combustion CO2 capture, Zr-BFDC shows the highest working capacity due to the relative steepness isotherms. However, for syngas purification, due to the higher partial pressure of CO2, the relative steepness of the CO2 isotherms for Zr-BFDC is less of an advantage, resulting in working capacities that are less than those of Zr-BTDC and UiO(BPYDC). For biogas stream purification, UiO(BPYDC) shows the highest working capacity. Furthermore, density functional theory (DFT) calculations revealed that the incorporation of heteroatoms alters the distribution of charge in the system, introducing regions of negative charge around heteroatoms, leading to enhanced interactions between framework atoms and CO2 molecules.

Role of Transient Co-Subcarbonyls in Ostwald Ripening Sintering of Cobalt Supported on γ-Alumina Surfaces

The stability and mobility of atomic cobalt and of cobalt subcarbonyl species on γ-Al2O3 surfaces have been investigated using density functional theory (DFT) with a view to elucidate possible mobile species on these surfaces, which can act as agents in the Ostwald ripening process. The two most stable alumina surfaces γ-Al2O3(100) and γ-Al2O3(110) were probed at different levels of hydration. The stability of cobalt subcarbonyl species on γ-Al2O3(100) at high partial pressure of CO (10 bar) increases with increasing number of CO ligands attached to the central cobalt atom up to Co(CO)3 but exhibits a more complex behavior on γ-Al2O3(110). The effect of the hydration level on the stability of cobalt subcarbonyls was investigated. The interpretation of the DFT results in a thermodynamic model shows that at equilibrium the main cobalt subcarbonyl species present on the alumina surface at ca. 500K in the presence of CO are Co(CO)3 and Co(CO)4, with Co(CO)3 being the dominant species on dry γ-Al2O3(100) and w...

The peculiar carbon metabolism in diatoms.

Diatoms are microalgae that arose over the last 100 Myr, thus phylogenetically constituting a relatively recent group of organisms. Analysis of microfossils that can be traced through geological time, as well as their contributions to seafloor sediments and fossil fuel reserves, demonstrates that diatoms have played a crucial role during this time. The review by Benoiston et al . [1] in this issue combines the current information on the evolution and biogeochemical functions of diatoms over time. Paleoecological data contain information for evaluating genetic variation through past climate changes, going back thousands of years in time [2]. In their review, Godhe & Reynardson [3] suggest the adoption of multiple strains of individual species for refining our understanding of the carbon metabolism and its variation within and between species. Diatoms are photosynthetic organisms using the energy of the Sun to build up organic molecules via CO2 fixation (primary production). For a long time, land plants have been supposed to be the main primary producers, however, recent estimations consider the contribution of algae to be as high as that of land plants [4]. The key process of the photosynthetic Calvin–Bensson–Bassham cycle is the fixation of CO2 onto ribulose-1,5-bisphosphate, mediated by the catalytic enzyme activity of RuBisCO. This reaction yields 3-phosphoglycerates, which immediately are converted to triose phosphates that are required to regenerate ribulose-1,5-bisphosphate. The contribution by Jensen et al . [5] reviews the regulation of the Calvin–Benson–Bassham cycle in diatoms, presenting a regulation process that is based on transcriptional regulation. This finding contrasts with land plants, in which the Calvin–Benson–Bassham is mostly regulated at the enzymatic level. Because a high local CO2 partial pressure in the close vicinity of the RuBisCO is vital to avoid photorespiration, …

Different Strategies for Accelerated CO2 Absorption in Packed Columns by Application of the Biocatalyst Carbonic Anhydrase

Within this work, the combination of an energetically favorable aqueous N-Methyldiethanolamine (MDEA) solution and the enzyme carbonic anhydrase is investigated in a packed column pilot plant. The use of aqueous MDEA solution for CO2 separation is already known from natural gas applications, for which an increased driving force due to the higher partial pressures of CO2 overcompensates reaction kinetic limitations. The objective of the addition of carbonic anhydrase is to countervail the loss of separation efficiency caused by the lower driving force in CO2 capture from power plant flue gases. Hence, carbonic anhydrase acts as a key to harness the energetic advantage of these solvent systems. However, application of the enzyme also poses restrictions on the process. Especially compliance with the enzyme stability limits is challenging for desorption, which is generally performed at high temperatures.In order to determine an optimal implementation of the enzyme into the process the current work presents different strategies how to apply CA as a biocatalyst in reactive absorption processes and shows how absorption efficiency is influenced. For introducing the enzyme to a packed column two approaches are investigated in this study. The simplest way of application is to dissolve the enzyme in the solvent. This allows the enzyme to work exactly where the reaction kinetic limitation can be found, in the liquid boundary layer. However, due to the temperature sensitivity of the enzyme an additional enzyme recovery step prior to the desorber might be necessary if desorption is to be performed at high temperatures. The immobilization of the enzyme inside the absorption column presents an alternative to prevent this additional separation, but may cause additional mass transfer limitations at the solid particles in which the enzyme is immobilized. The immobilization and the necessity of a suitable packing in which the enzyme particles can be filled, also makes this strategy more complicated but allows placing the enzyme at a location of most suitable process conditions in the column. But most importantly it completely avoids that the enzymes experience high temperature in the desorber. Systematic investigations of the influence of specific liquid load, liquid inlet temperature, MDEA-concentration and enzyme immobilization on absorption performance are conducted. Dissolved enzyme showed a nearly three times higher absorption performance than the immobilized enzyme under equivalent operating conditions, however the immobilized enzyme concentration used was effectively 50 times lower, meaning the result is actually quite promising for immobilized CA. From the investigated operating conditions, a liquid inlet temperature of 20°C, a MDEA concentration of 30wt.-% and a liquid flow rate of 24 m3 m-2 h-1 showed the best absorption performance with the dissolved enzyme. The measured absorption rate was 7.57 times higher than without enzyme added.

A Compararitive Review of Next-generation Carbon Capture Technologies for Coal-fired Power Plant

Despite the demonstration of large-scale carbon capture and storage (CCS) at a small number of coal power plants in North America, development of the technology remains slow in Europe, where several large projects have been cancelled in the last five years. Established CO2 capture technologies such as amine scrubbing consume significant amounts of energy, reducing power plant efficiency by around 10%pts and contributing to increases in the cost of electricity production by up to 80%. Within these economic constraints, CCS demonstrations have been limited to regions where CO2 has a value for enhanced oil recovery, a low cost coal supply is available, and effective CO2 emissions caps or pricing are in place. For CCS to be competitive as a low carbon energy source in a broader context, there is clearly a need for new technologies which can achieve dramatic reductions in the cost of capture, primarily through a reduction in the process energy consumption.Concerted research efforts worldwide are therefore developing a wide range of innovative solutions to the fundamental gas separation step at the heart of nearly all forms of carbon capture, whether post-combustion, pre-combustion or oxyfuel combustion. Dedicated research programmes in the US and Europe in particular have set ambitious targets for new technologies to achieve a CO2 capture cost approaching $20/t. Novel solvents aim to achieve lower regeneration energy requirements than conventional amines, with phase change systems, ionic liquids and other non-aqueous solvents, and enzyme-activation all representing promising approaches. Alternatively, techniques used in other commercial gas separations, including solid sorbents, membranes, and cryogenic separation, have also been widely investigated. Whilst challenging for post-combustion capture applications, these techniques may be of particular benefit to pre-combustion capture systems where much higher partial pressures of CO2 are available, and integration of the CO2 capture step and water gas shift reaction can be achieved using sorbents or membranes. In oxyfuel combustion, pressurised systems have demonstrated the most potential for efficiency improvements, with novel power cycles such as the supercritical CO2 cycle well-suited to exploiting the unique combustion conditions. Developments in ceramic membranes for oxygen production may also provide a lower cost alternative to cryogenic air separation. Finally, chemical looping combustion is a unique approach to carbon capture which can achieve dramatic energy savings through its inherent avoidance of any gas separation step. This technology has recently begun to see significant scale up by a number of companies and research institutes, with a focus on low-cost oxygen carriers.This paper will review these developments in novel capture technologies and compare them on the basis of efficiency penalty, cost of electricity, cost of CO2 capture, and their current developmental status. Processes which inherently incorporate CO2 capture with the power generation process, such as chemical looping combustion or the oxyfuel-based Allam Cycle appear to offer the greatest potential to meet the economic targets. For retrofit applications, high performances are associated with capture plant which is able to compensate for energetic losses by acting as an additional source of power, with calcium looping and fuel-cell based processes as notable examples.

Application of the DMXTM CO2 Capture Process in Steel Industry

The VALORCO project coordinated by ArcelorMittal and funded by ADEME aims at reducing and valorizing CO2 emissions from steel industry. This paper presents the main results of task 1.1A of the VALORCO project dedicated to CO2 capture on blast furnace gases by means of amine scrubbing technologies. Blast furnace gases are characterized by high CO2 and CO partial pressures and the absence of oxygen. Since few literature data are available on the effect of CO on solvent degradation and CO2 absorption, experimental work was needed. In this context, three IFP Energies nouvelles (IFPEN) processes initially developed for CO2 capture on coal power stations were evaluated for blast furnace applications: HicaptTM process (MEA 30wt.%), Hicapt+TM process (MEA 40wt.%) and DMXTM process (Demixing solvent).For the three processes, it was shown that CO absorption is slow and mainly physical even though kinetic studies highlighted a chemical absorption of CO in CO2-free amine solutions, especially for MEA solvents. This chemical absorption is however largely inhibited in presence of CO2 which limits this phenomenon to occur in real process conditions. Degradation studies in batch reactors showed a low impact of CO on MEA solutions and no quantitative effect on DMX solvent. Compared to flue gases containing oxygen, amine degradation observed with blast furnace gases is globally negligible for all tested solvents. Above conclusions were confirmed with two long-run tests (∼1500h) on a CO2 capture mini-pilot at IFPEN. These tests also underlined a high CO2/CO selectivity with very few CO in CO2 produced, the possibility of reaching high CO2 capture rate (>99.5%) and the good operability for all studied processes. Moreover, DMX solvent allows using carbon steel as process metallurgy and producing CO2 at 6 bara which turn into subsequent economical savings. Considering an available steam at 21 €/t, it would be possible to produce CO2 from blast furnace gases at around 40 €/t by using the DMXTM process.

Multicycle activity of natural CaCO3 minerals for thermochemical energy storage in Concentrated Solar Power plants

Thermochemical energy storage in Concentrated Solar Power plants by means of the Calcium-Looping process is a promising novel technology that would allow for a higher share of renewables. A main benefit of this technology is the use of widely available, non-toxic and environmentally friendly calcium carbonate minerals as raw materials to store energy. Efficient integration of the Calcium-Looping process into Concentrated Solar Power plants involves the endothermic calcination of CaCO3 in the solar receiver while the exothermic carbonation of CaO is carried out at high temperature under high CO2 partial pressure. The heat released by this reaction is carried out by the excess CO2 and employed for power generation by means of a closed CO2 cycle. This work explores the multicycle Calcium-Looping performance of naturally occurring CaCO3 minerals such as limestone, chalk and marble for thermochemical energy storage in Concentrated Solar Power plants. Despite their similar composition (almost pure CaCO3), these minerals exhibit a significant difference in their Calcium-Looping multicycle activity, which may be attributed to differences in particle size and microstructure. Pore plugging at the Calcium-Looping conditions for thermochemical energy storage tested in our work is a main limiting mechanism on the multicycle CaO carbonation activity.

Experimental analysis of density fingering instability modified by precipitation.

We analyze the effect of precipitate formation on the development of density induced hydrodynamic instabilities. In this case, the precipitate is BaCO3, obtained by reaction of CO2 with aqueous BaCl2. CO2(g) dissolution increases the local density of the aqueous phase, triggering Rayleigh-Taylor instabilities and BaCO3 formation. It was observed that at first the precipitate was formed at the finger front. As the particles became bigger, they began to fall down from the front. These particles were used as tracers using PIV technique to visualize the particle streamlines and to obtain the velocity of that movement. This falling produced a downward flow that might increase the mixing zone. Contrary to expectations, it was observed that the finger length decreased, indicating that for the mixing zone development, the consumption of CO2 to form the precipitate is more important than the downward flow. The mixing zone length was recovered by increasing the availability of the reactant (higher CO2 partial pressure), compensating the CO2 used for BaCO3 formation. Mixing zone development rates reached constant values at shorter times when the precipitate is absent than when it is present. An analysis of the nonlinear regime with and without the precipitate is performed.