Mineral Sequestration Research Articles

Geothermal resources, ore deposits and carbon mineral sequestration in hydrothermal areas of Southern Tuscany

Geothermal resources, ore deposits and carbon mineral sequestration in hydrothermal areas of Southern Tuscany

Carbon dioxide capture and storage by pH swing mineralization using recyclable ammonium salts and flue gas mixtures

AbstractCO2 mineral sequestration through the employment of silicate rocks such as serpentine is an important technology for the mitigation of CO2 emissions. Most mineral carbonation works in this study use pure CO2. The indirect carbonation process employed different flue gases (5, 15, 25% CO2) and the presence of SOx and NOx. Also, the direct contact of CO2 with the Mg source was compared to the indirect reaction of Mg with CO2 as NH4CO3. The impact of variables such as temperature, solid‐liquid ration (S/L), and molar ratio of additives on carbonation rate and degree was studied. An average carbonation efficiency of about 90% was achieved at 80°C after 30 min for indirect mineral carbonation process. The carbonation efficiency decreased to 50‒60% when the process was directly employed. The carbonation efficiency obtained in the presence of 15‒25% CO2 was very similar to that with 100% CO2 at 140°C, while at 80°C, the carbonation efficiency in presence of flue gas (40‒55%) was much larger compared to that using pure C02 (10% after 3 h). SOx and NOx co‐removal efficiency was 54.4% and 18% at 140˚C and 20 bar, respectively.

Mineralogical and Geochemical Characteristics of Caprock Formations Used for Storage and Sequestration of Carbon Dioxide

The main objective of the present study is to characterize cap rock formation used for geological storage of carbon dioxide (CO2). The petrophysical properties of several rocks were studied before CO2 injection. This step is necessary for an understanding of CO2-brine-rock interactions. The mineralogical composition of several clay samples collected from real storage sites located in the south of Tunisia was determined by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) coupled to a probe EDS, infrared spectroscopy, thermal analysis and fluorescence spectra. The obtained experimental results reveal that illite, calcite and quartz are the dominant clay minerals. Dolomite and albite are also present. Besides, SEM analysis shows laminated structure for these samples which suggests low crystallinity. This sample contains a higher content of Fe, Cl, Ca and O. The clay cover may also be useful in storage process by immobilizing the migration of CO2 outer of the geological site and activating the process of mineral sequestration.

Hydrothermal Carbonation of K–Rich Ash, Value Added Energy Engineering and CO2 Mineral Sequestration

In this paper, hydrothermal carbonation of raw K–rich ash derived from a palm oil plant factory in West Kalimantan, Indonesia had been studied and evaluated at varying temperatures of 50°C to 300°C, initial CO2 pressure at between 2MPa to 2.5MPa and a maximum final pressure of 8.5MPa and a residence time of 30min. The yield of the solid products was about between 47 wt% and 66 wt% and the effective CO2 content which was captured by hydrothermally solid products was between 0.057 ton · ton–1 and 0.115 ton · ton–1 following hydrothermal carbonation. In addition, dehydration of solid product occurred at mostly 300°C, while oxidation was started at 50°C. Obviously, both the sorption–dissociation of CO2 in the solution and hydrothermal carbonation process produce a global pressure drop in the system resulting in CO2 mineral sequestration. The carbonation efficiency of solid–fluid interactions at 25°C and after 24h period was 25.36% and 0.05 954mol of CO2 were consumed by the carbonation process. At the condition applied, observed several possibilities were observed such as: the pH (alkalinity), total inorganic carbon, direct precipitation of carbonates minerals as well as crystallization of carbonates in the solution and solid products.

Hydration and carbonation reactions of calcium oxide by weathering: Kinetics and changes in the nanostructure

The weathering reactions of hydration and carbonation of nanostructured calcium oxide with atmospheric moisture and carbon dioxide have been characterized. This work is the first-to-date combined kinetic and nanostructural research on CaO oriented to two key processes for different systems, i.e. hardening of construction materials and carbon mineral sequestration. The evolution of the precipitated crystalline phases was monitored by X-ray diffraction and thermogravimetry, along with structural characterization by nitrogen physisorption, electron microscopy and small-angle scattering. Complete hydration of the samples was always found prior to the onset of carbon sequestration, which depended on the nanostructure of the samples. Hence, carbonation started after 300h of weathering for samples with a specific surface area of 40m2/g, whereas carbonation of the samples with 20m2/g occurred after 550h. Full carbonation from atmospheric CO2 (100% efficiency) was obtained in all cases. This combined research was completed by developing an empirical description of the weathering reactions in terms of a two-process Random Pore Model. Finally, this work aimed to determine the role of the nanostructure of samples based on industrial wastes as one of the most important factors for developing efficient carbon sequestration technologies.

Experimental investigation of enhanced carbonation by solvent extraction for indirect CO2mineral sequestration

An indirect CO2 mineral sequestration involving two separated steps with acetic acid as a recycling medium provides a promising method for CO2 sequestration as well as the minimum CO2 emission for calcium carbonate production. In such an indirect route, the calcium carbonate production in the second gas-liquid reactive crystallization step has been challenged by low carbonation efficiency. This paper describes significant enhancement of the second step by coupling reactive crystallization and solvent extraction with the introduction of the organic solvent, tributyl phosphate (TBP), to the process. Based on the reaction mechanism of this enhanced carbonation process, many influencing factors including stirring speed, phase ratio, reaction time, reaction temperature, CO2 partial pressure, and the composition of the initial aqueous solution, were studied. Given the operating conditions of 60 min reaction time, 500 rpm stirring speed, organic-to-aqueous phase volume ratio of 1, 80 °C reaction temperature, 4.0 MPa CO2 partial pressure, and initial pH of 7, the obtained crystallization conversion in the second step was found to increase from 20% to above 50%, with the incorporation of TBP and the addition of magnesium acetate.

Calcium silicates synthesised from industrial residues with the ability for CO2 sequestration.

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO2 emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO2 mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO2 concentration within a mixture of gases. The CO2 concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO2 per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry.

Toward Cleaner Geothermal Energy Utilization: Capturing and Sequestering CO $$_2$$ 2 and H $$_2$$ 2 S Emissions from Geothermal Power Plants

Field scale reactive transport models of CO $$_2$$ and H $$_2$$ S mineral sequestration in basalts were developed with a focus on Reykjavik Energy’s ongoing CarbFix and SulFix sour gas re-injection tests at Hellisheidi geothermal power plant, SW-Iceland. Field data, such as drill cuttings and a calcite cap-rock overlying the high-temperature geothermal reservoir, suggest that mineral CO $$_2$$ and H $$_2$$ S sequestration already plays an important role within Hellisheidi geothermal system. The data indicate CO $$_2$$ sequestration to be most intensive from 550–800-m depth below surface, while H $$_2$$ S sequestration is most intensive below 800-m depth. Injecting and precipitating CO $$_2$$ and H $$_2$$ S into nearby formations with the objective of imitating and accelerating natural sequestration processes should therefore be considered as an environmentally benign process. Reactive transport simulations predict rapid and efficient mineralization of both CO $$_2$$ and H $$_2$$ S into thermodynamically stable minerals, with calcite, magnesite, and pyrrhotite being the favored carbonate and sulfide minerals to form. At intermediate depths and low temperatures (25–90 $$^\circ $$ C), calcite is the main CO $$_2$$ sequestering carbonate predicted to form, while magnesite is the only carbonate predicted to form at high temperatures ( $$>$$ 250 $$^\circ $$ C). Despite only being indicative, it is concluded from this study that the capture and sequestration of CO $$_2$$ and H $$_2$$ S from geothermal power plants are a viable option for reducing their gas emissions and that basalts may comprise ideal geological CO $$_2$$ and H $$_2$$ S storage formations.

A numerical study of capillary pressure–saturation relationship for supercritical carbon dioxide (CO2) injection in deep saline aquifer

Carbon capture and sequestration (CCS) is expected to play a major role in reducing greenhouse gas in the atmosphere. It is applied using different methods including geological, oceanic and mineral sequestration. Geological sequestration refers to storing of CO2 in underground geological formations including deep saline aquifers (DSAs). This process induces multiphase fluid flow and solute transport behaviour besides some geochemical reactions between the fluids and minerals in the geological formation. In this work, a series of numerical simulations are carried out to investigate the injection and transport behaviour of supercritical CO2 in DSAs as a two-phase flow in porous media in addition to studying the influence of different parameters such as time scale, temperature, pressure, permeability and geochemical condition on the supercritical CO2 injection in underground domains. In contrast to most works which are focussed on determining mass fraction of CO2, this paper focuses on determining CO2 gas saturation (i.e., volume fraction) at various time scales, temperatures and pressure conditions taking into consideration the effects of porosity/permeability, heterogeneity and capillarity for CO2–water system. A series of numerical simulations is carried out to illustrate how the saturation, capillary pressure and the amount of dissolved CO2 change with the change of injection process, hydrostatic pressure and geothermal gradient. For example, the obtained results are used to correlate how increase in the mean permeability of the geological formation allows greater injectivity and mobility of CO2 which should lead to increase in CO2 dissolution into the resident brine in the subsurface.

A laboratory-scale study of the aqueous mineral carbonation of coal fly ash for CO2 sequestration

Mineral sequestration of waste materials provides a promising method for CO2 sequestration, due to its potential as a finishing step in industries which produce CO2 and alkaline solid by-products. However, a number of challenges in mineral carbonation that remain to be resolved, including overcoming the slow kinetics of mineral–fluid reactions, dealing with the large volume of source material required, and reducing the energy needed to hasten the carbonation process. In order to overcome the slow reaction kinetics, experiments on accelerated carbonation are being conducted worldwide. As a result, studies of the operational parameters of the carbonation reaction are progressing. The present study examined the effect of two operational parameters on the mineralization of Australian coal fly ashes for CO2 sequestration at laboratory scale. In this study, carbonation tests were carried out for three Australian coal fly ash samples (S1, S2, S3) inside a continuously stirred reaction chamber. Different water-to-solid ratios (from 0.1 to 1) and reaction temperatures (20–80 °C) were tested under a moderate initial CO2 gas pressure of 3 MPa, and the pressure drop due to carbonation with time was recorded until a constant pressure was achieved at the end of each test. The quantity of CO2 stored in each test was estimated by applying ideal gas law to the test conditions. The formation of carbonates during testing was confirmed by performing micro-structural analysis using scanning electron microscopy. According to the results, a 0.2–0.3 water-to-solid mix ratio recorded the highest sequestration potential for all three fly ashes, and was identified as the optimum for mineralization. The increase of reaction temperature resulted in a faster rate of initial CO2 transfer into the fly ash material but did not have a significant impact on the overall sequestration. Of the three tested ashes, S3 ash sample showed the highest sequestration potential of 27.05 kg of CO2 per ton of fly ash under test conditions. The results confirm the possibility of manipulating the water-to-solid mix ratio and the reaction temperature to enhance the carbonation reaction for mineral CO2 sequestration.

CO2 mineral sequestration by wollastonite carbonation

In this paper, we demonstrated a new approach to CO2 mineral sequestration using wollastonite carbonation assisted by sulfuric acid and ammonia. Samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and 29Si nuclear magnetic resonance. The change in Gibbs free energy from −223 kJ/mol for the leaching reaction of wollastonite to −101 kJ/mol for the carbonation reaction indicated that these two reactions can proceed spontaneously. The leached and carbonated wollastonite showed fibrous bassanite and granular calcium carbonate, respectively, while the crystal structure of pristine wollastonite was destroyed and the majority of the Ca2+ in pristine wollastonite leached. The chemical changes in the phases were monitored during the whole process. A high carbonation rate of 91.1 % could be obtained under the action of sulfuric acid and ammonia at 30 °C at normal atmospheric pressure, indicating its potential use for CO2 sequestration.

Comparative study of five Québec ultramafic mining residues for use in direct ambient carbon dioxide mineral sequestration

The mineral carbonation of five different ultramafic mining residues was studied experimentally, namely chrysotile (Black Lake mine [Bl] and Asbestos mine [Asb]), nickel (Ni–Cu Dumont mine project [Du] and Raglan Ni–Cu–EGP mine [Rgl]) and diamond mine residues (Renard mine project [Rnd]). The CO2 uptake, gas volume and mining residue physical and chemical characteristics were monitored in a fixed-bed diffusion cell to determine their potential for direct ambient carbon dioxide capture and to identify specific parameters influencing their reactivity. The various samples exhibited different behavior when reacted with gaseous CO2. Brucite- and (fibrous serpentine) chrysotile-containing residues exhibited higher pore-water pH, carbonation rate and yield with brucite content broadly dictating the reaction progress. Massive serpentines such as lizardite/antigorite-containing residues were found to weakly dissolve which significantly reduced their carbonation rate. The Mgbru/Mgtot ratio (brucitic Mg-total Mg atom ratio) and the percentage of fibers were thus the key parameters controlling the direct carbonation of alkaline mining residues. Recourse to alkaline and alkaline-earth metal contents to assess mining residue carbonation capacity may lead to inaccurate estimates as the residue Mg/Si and Mg/Fe ratios were found to greatly control the carbonation capacity through silica gel coating (high Si content) or/and iron (III) hydroxide passivation (high Fe content).

Simultaneous precipitation of magnesite and lizardite from hydrothermal alteration of olivine under high-carbonate alkalinity

The present study reports original experiments in order to investigate the simultaneous serpentinization and carbonation of olivine with relevance in Earth systems (e.g. functioning of hydrothermal fields) or in engineered systems (e.g. ex-situ and in-situ mineral sequestration of CO2). For this case, specific experimental conditions were examined (200°C, saturated vapor pressure≈16bar, solution/solid weight ratio=15, olivine grain size<30μm and high-carbonate alkalinity≈1M NaHCO3). Under these conditions, competitive precipitation of magnesite and serpentine (preferentially lizardite type) was clearly determined by using conventional analytic tools (XRD, FESEM, FTIR and TGA); excluding the fate of the iron initially contained in olivine, the alteration reaction for olivine under high-carbonate alkalinity can be expressed as follows:2Mg2SiO4+2H2O+HCO3−→MgCO3+Mg3Si2O5OH4+OH−.This reaction mechanism implied a dissolution process, releasing Mg and Si ions into solution until supersaturation of solution with respect to magnesite and/or serpentine. The released iron contained in the olivine has not implied any precipitation of iron oxides or (oxy)hydroxides; in fact, the released iron was partially oxidized (about 50%) via a simple reduction of water (2Fe2++2H2O→2Fe3++H2+2OH−). In this way, the released iron was incorporated in serpentine (Fe(II) and Fe(III)) and in magnesite (Fe(II). The latter was clearly determined by FESEM/EDS chemical analysis on the single magnesite crystals. The nucleation and epitaxial growth processes at the olivine–fluid interfaces cannot be excluded in our investigated system.The experimental kinetic data fitted by using a kinetic pseudo-second-order model have revealed a retarding process of serpentine formation with respect to magnesite (about three times slower); in fact, the magnesite seems to reach an apparent stabilization after about 20days of reaction while the serpentine follows a progressive slower evolution. We assumed that the magnesite has reached a fast apparent equilibrium with solution because the available carbonate species are not renewed from fluid phase as typically constrained in aqueous carbonation experiments where a given CO2 pressure is imposed in the system.On the other hand, the reactivity of serpentinized olivine (chrysotile+brucite+small amount of residual olivine) and high-purity chrysotile at the same above investigated conditions; and the olivine serpentinization in initial acid pH≈0.66 are also reported as complementary information in this study.These novel experimental results concerning simultaneous serpentinization and aqueous carbonation of olivine expand the thermodynamic conditions where serpentine and magnesite can simultaneously precipitate; this could contribute to a better understanding of fluid–rock interactions in natural active hydrothermal fields on Earth.

Environmental impact and techno-economic analysis of the coal gasification process with/without CO2 capture

Coal gasification, the technology for high-efficient utilization of coal, has been widely used in China. However, it suffers from high CO2 emissions problem due to the carbon-rich character of coal. To reduce CO2 emissions, different CO2 capture technologies are developed and integrated into the coal gasification based processes. However, involving CO2 capture would result in energetic and economic penalty. This paper analyses three cases of coal gasification processes from environmental, technical, and economical points of view. These processes are (1) a conventional coal gasification process; (2) a coal gasification process with CO2 capture and sequestration, in which CO2 is stored by mineral sequestration; (3) a coal gasification process with CO2 capture and utilization, in which CO2 is reused to produce syngas. The results show that the coal gasification process with CO2 capture and sequestration has advantage only in environmental aspect compared to the conventional process. The process with CO2 capture and utilization has advantages in both technical and environmental aspects while disadvantage in economic aspect. However, if the carbon tax higher than 15 USD/t CO2 is introduced, this disadvantage will be negligible.

Mechanisms of serpentine–ammonium sulfate reactions: towards higher efficiencies in flux recovery and Mg extraction for CO2 mineral sequestration

There is a growing research interest in CO2 mineral sequestration methods that follow an intermediate Mg extraction step (from Mg-silicates, especially serpentinite rock) by fluxing with ammonium sulfate (AS) or ammonium bisulfate (ABS).

Carbon Dioxide Sequestration in Alkaline Top Soil Using Alkaline Wastes

Due to growing concern about climate change and global warming, new ways must be developed to reduce CO2 emissions in atmosphere. Incinerator ash produced in municipal treatment facilities and marble-dust produced during marble cutting process are alkaline wastes. This paper examines the carbon mineral sequestration potential of mixing alkaline wastes in two soil samples in accelerated carbonation conditions. Six different percentages of alkaline wastes in 20g sample were used. Batch reactor conditions were maintained at 40°C, relative humidity 60-70% and CO2 flow-rate of 10 litres-a-minute. Optimum water content was found by carrying out experiments on a sample with 7 different water-to-solid ratio (0, 0.2, 0.4, 0.6, 0.8, 1 and 1.2). The particle-size effect was gauged by taking soil samples sieved through standard sieve sizes of BSS25 and BSS50. It was concluded that low water-to-solids ratio is better for carbonation, although some minimum amount of water is necessary for reaction. The optimum water-to-solids ratio for incinerator ash comes to be 0.4. Marble dust was found to be inefficient to capture CO2 due to lower pH and due to lump formation. As expected, carbonation was higher for samples with less particle size and higher surface area.

Benefaction from Carbonation of Flue Gas CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; as Coal Mining Filling

CO2 capturing, transport and sequestration by pressurized water dissolution and reacting by natural alkali lime and magnesia in coal fly ash or other sources become an industrial advantageous sequestration option resulting in green waste solutions or solid fines. Mg and Ca containing minerals are reacting with CO2 to form carbonates. Various types of fly ash materials may react with CO2 to form carbonate regarding ash composition and reaction parameters. Mineral sequestration of CO2 will also allow using the products in cement industry or as cement material in constructions with low cost. This paper discussed progress on coal mining filling by carbonation method using coal fly ash of Soma, Yatagan, Afsin Elbistan Power Stations. Other filler materials containing coal mine waste shale, fly ashes and foam concrete, and additives were searched for pretreatment methods to enhance cement reactivity; and in analyzing the structural changes to identify reaction paths and potential barriers.

Life cycle and cost assessment of mineral carbonation for carbon capture and storage in European power generation

Large-scale greenhouse gas (GHG) emission reductions are crucial for achieving the European goals for climate change mitigation. A frequently discussed option is carbon capture and storage (CCS), where CO2 emissions from point sources are captured and stored in geologic structures. However, concerns about risks of leakages of CO2 from geological storage have been raised. These risks could be avoided with ex situ mineral carbonation, where the captured CO2 is stored in an inert and stable solid form after reacting with calcium and magnesium silicates. For a comprehensive assessment of the environmental and economic performance of this CO2 storage option in fossil-fueled power generation chains, life cycle assessment (LCA) and levelized cost of electricity (LCoE) calculations are performed. The implementation of CCS using mineral carbonation leads to life cycle GHG emission reductions of 15–64% and LCoE increases of 90–370% on a per kWhel basis compared to a reference power plant without CCS. The life cycle GHG emission reduction achievable with mineral sequestration is less substantial than with geological storage of CO2 due to significant energy and chemical additives requirements. Accordingly, LCA results for other environmental indicators are worse than those of the reference plant without CCS and the geological CO2 storage option.

Impact of temperature and oxygen availability on the dynamics of ambient CO2 mineral sequestration by nickel mining residues

A detailed study of the sensitivity of mineral carbonation to temperature variations and air oxygen content in a saturated nickel mining residue (NiMR) under humid environments was carried out. The dynamics of CO2 uptake in NiMR beds subjected to carbonation was monitored as a function of temperature and oxygen content in the range 10–40°C and 0–20vol.%, respectively. An increase in the rate of carbonation was noticed along with elevated carbonation temperatures. A temperature rise from 10 to 40°C was accompanied by a ten-fold increase in initial reaction rate and was corroborated by a corresponding stimulated release of magnesium in pore water as evidenced by residue leaching experiments. Furthermore, significant heat was generated during reaction progress which led to a rise in temperature up to 4.9°C at a 10°C carbonation temperature. The rate of carbonation was found to be reduced by the increase of iron (III) content in the pore water fostered by the presence of dissolved oxygen. Formation of iron hydroxides induced pore water acidification which stimulated carbonation. This was counterbalanced by the ensuing precipitation of iron (III) hydroxide as a thin coating which slowed the progress of carbonation. Using weakly concentrated CDTA-chelating ligands helped curb iron (III) precipitation which ensured higher carbonation rates under an oxic environment.

A Novel Method for CO2 Sequestration via Indirect Carbonation of Coal Fly Ash

Coal fly ash is a potential candidate for CO2 mineral sequestration. If calcium is extracted selectively from coal fly ash prior to carbonation (namely indirect carbonation), a high-purity and marketable precipitated calcium carbonate (PCC) can be obtained. In the extraction process, recyclable ammonium salt (i.e., NH4Cl/NH4NO3/CH3COONH4) solution was used as a calcium extraction agent in this study. The influence of time, temperature, agent concentration, and solid-to-liquid ratio on calcium extraction efficiency was explored. NH4Cl/NH4NO3/CH3COONH4 are confirmed to be effective calcium extraction agents for the high-calcium coal fly ash investigated, and about 35–40% of the calcium is extracted into the solution within an hour. The calcium extraction performance is best for CH4COONH4, followed by NH4NO3 and NH4Cl. Increasing temperature from 25 to 90 °C and agent concentration from 0.5 to 3 mol/L only subtly increases calcium extraction efficiency for NH4Cl and NH4NO3, while the positive effect of incre...