Pre-combustion CO2 Research Articles

Dynamic CO2 sorption on MgO-based sorbent in the presence of CO and H2O at elevated pressures

The presence of gas species other than the target adsorbate in practical conditions causes complications in implementing a sorption-based process because of synergistic or detrimental effects on the sorption mechanism. MgO-based sorbents have attracted massive attention for the pre-combustion CO2 capture, where H2O and CO co-exist in emission gas. Although H2O has been reported to greatly enhance CO2 sorption kinetics, CO2 sorption behavior and mechanism under a large quantity of H2O as in the practical condition remain unclear. Furthermore, CO2 sorption behavior in the presence of CO has not been adequately examined. Here, the dynamic CO2 sorption behavior of MgO-based sorbent was understood by coupling the breakthrough experiment under practically relevant conditions with in situ DRIFTS results. At elevated pressures, the sorption performance was considerably enhanced, whereas the influence by temperatures was insignificant. In addition, H2O enhanced CO2 sorption kinetics and initial CO2 sorption on MgO-based sorbent, whereas CO hindered them. In situ DRIFTS analyses for the mechanism study revealed that OH groups generated from H2O dissociation created highly basic sites that promoted the formation of monodentate carbonate, thereby enhancing the initial CO2 sorption. In contrast, CO hampered CO2 sorption through two mechanisms: (1) competitive sorption between CO2 generated from the water–gas shift reaction and CO2 in the feed; (2) interference of the promoted sorption by the molten nitrate salts. This study demonstrated that the practical condition of the pre-combustion CO2 capture significantly alters the CO2 sorption behavior of MgO, thereby providing insights for the ultimate implementation of MgO-based sorbents.

Techno-economic evaluation of carbon capture via physical absorption from HTL gas phase derived from woody biomass and sewage sludge

• Carbon capture from the HTL gas phase is modeled based on physical absorption. • Pre-combustion CO 2 capture has potential to facilitate H 2 recovery from HTL gas. • CO 2 with purity between 90 and 98 mol % is obtained at a cost of 40–53 EUR/tonne. • Higher CO 2 purity of 98–99 mol % can be achieved at a cost of 57–77 EUR/tonne. Due to its capability to produce negative CO 2 emissions, bioenergy in combination with carbon capture and storage (BECCS) has been identified as a key technology to limit global warming and to support the energy transition in pursue of the climate targets of this century. Among different bioenergy applications, advanced liquid biofuels produced through the hydrothermal liquefaction (HTL) of waste biomass have gained interest as promising drop-in alternatives to fossil fuels. However, there is lack of studies in literature that evaluate the potential of HTL as negative emission technology in the context of BECCS and present detailed process design of such an implementation for different types of biomass. In this paper, we perform carbon capture modeling based on state-of-art experimental data on HTL of waste lignocellulosic and urban biomasses by means of physical absorption via the Selexol™ process. The process model is utilized for developing a techno-economic analysis that highlights key parameters to optimize CO 2 capture cost efficiency. The results indicate that the purity of the CO 2 product fulfils the requirements for geological storage in all cases studied, and is on-spec for pipeline transportation when the composition of C 2+ hydrocarbons and H 2 S in the HTL gas are kept below 4 and 1 mol % respectively, or by the implementation of two absorption steps. For the standard process evaluated, the estimated cost of the captured CO 2 is between 40 and 53 EUR/tonne, which is in the range of the carbon price expected within this decade in the EU emission trading system, given the announced cap reductions until 2030 and the targets set by the European Green Deal.

High temperature CO2 sorption using mixed oxides with different Mg/Al molar ratios and synthesis pH

Scheme of post- and pre-combustion processes for CO 2 capture at high temperature using hydrotalcite-derived mixed oxides as CO 2 sorbents. • Several hydrotalcite-derived mixed oxides were prepared to be used as CO 2 sorbents. • Different Mg/Al molar ratios and synthesis pH were used to prepare the materials. • The CO 2 sorption isotherms were determined at 300 °C for screening purposes. • 8.5HT7 showed a high CO 2 sorption capacity: 1.62 mmol/g @ p CO 2 = 1 bar and 300 °C. • The effect of steam over successive CO 2 sorption–desorption cycles was assessed. Several hydrotalcites were prepared by the co-precipitation method with different Mg/Al molar ratios (from 2 to 20) and synthesis pH (8.5 and 10); upon calcination, the hydrotalcite-derived mixed oxides (HDMOs) were obtained, to be used as CO 2 sorbents at high temperature, for instance in post- or pre-combustion CO 2 capture processes. The sorption equilibrium isotherms were determined for screening purposes of all materials prepared using a magnetic suspension microbalance (static experiments) at 300 °C, along with a detailed physicochemical characterization (TG-DTG, ICP-OES, XRD, FTIR, physical sorption–desorption of N 2 at −196 °C and TPD-CO 2 ). In addition, the most promising HDMOs, in terms of CO 2 sorption capacity, were submitted to successive CO 2 sorption–desorption cycles (dynamic experiments) in a packed column at 300 °C, with and without water in the feed, to assess their potential in a sorption–desorption cyclic operation. The results indicate that a synthesis pH of 8.5 provides samples with better CO 2 sorption capacities and that there is an optimum Mg/Al molar ratio (between 4 and 10). The sample with a synthesis pH of 8.5 and a Mg/Al molar ratio of 7 (called 8.5HT7) provided an outstanding CO 2 sorption capacity (1.62 mmol·g −1 at 1 bar of CO 2 and 300 °C) when compared with the other samples herein prepared, but also when compared with commercial (MG63 and MG70) and with other similar materials found in the literature. Finally, an average working capacity of 1.04 mmol·g −1 and 2.11 mmol·g −1 was obtained after repeated sorption–desorption cycles at 0.4 bar of CO 2 and 300 °C for the 8.5HT7 HDMO under dry and wet conditions (45 vol.% H 2 O), respectively.

Integration of gas switching combustion and membrane reactors for exceeding 50% efficiency in flexible IGCC plants with near-zero CO2 emissions

• Gas switching combustion and membrane reactors are integrated in an IGCC plant. • The proposed plants produce flexible electricity/H 2 with CCS to balance renewables. • IGCC benchmarks with/without CCS incorporate hot gas clean-up and H-class turbines. • Electric/H 2 LHV efficiencies up to 50.3%/62.4% with >98% CO 2 capture are achieved. • The energy penalty is less than 2%-points relative to the unabated IGCC plant. Thermal power plants face substantial challenges to remain competitive in energy systems with high shares of variable renewables, especially inflexible integrated gasification combined cycles (IGCC). This study addresses this challenge through the integration of Gas Switching Combustion (GSC) and Membrane Assisted Water Gas Shift (MAWGS) reactors in an IGCC plant for flexible electricity and/or H 2 production with inherent CO 2 capture. When electricity prices are high, H 2 from the MAWGS reactor is used for added firing after the GSC reactors to reach the high turbine inlet temperature of the H-class gas turbine. In periods of low electricity prices, the turbine operates at 10% of its rated power to satisfy the internal electricity demand, while a large portion of the syngas heating value is extracted as H 2 in the MAWGS reactor and sold to the market. This product flexibility allows the inflexible process units such as gasification, gas treating, air separation unit and CO 2 compression, transport, and storage to operate continuously, while the plant supplies variable power output. Two configurations of the GSC-MAWGS plant are presented. The base configuration achieves 47.2% electric efficiency and 56.6% equivalent hydrogen production efficiency with 94.8–95.6% CO 2 capture. An advanced scheme using the GSC reduction gases for coal-water slurry preheating and pre-gasification reached an electric efficiency of 50.3%, hydrogen efficiency of 62.4%, and CO 2 capture ratio of 98.1–99.5%. The efficiency is 8.4%-points higher than the pre-combustion CO 2 capture benchmark and only 1.9%-points below the unabated IGCC benchmark.

Silica Supported MgO as An Adsorbent for Precombustion CO2 Capture

MgO-silica nanocomposites were synthesized by dispersing MgO on three different silica supports, viz., ordered mesoporous MCM-41, SBA-15, and the nonporous fibrous silica nanospheres material (KCC-...

Synthesis of mesoporous MgO–CeO2 composites with enhanced CO2 capture rate via controlled combustion

Abstract MgO–CeO 2 composites with enhanced sorption rate for CO 2 capture were prepared via a sol-gel combustion method. The effects of water, cerium, and citric acid on the sorption performance were investigated systematically to elucidate the role of components. The cerium content substantially lowered the decomposition temperature by 100 °C and the amount of citric acid affected the propagation rate. Controlled combustion led to different pore structures and CO 2 capture performances, and controlling the amount of citric acid was the most effective way to improve the textural properties and performances. The developed MgO–CeO 2 composites consist of nanoparticles covered with a flat plate, and a small amount of residual carbon from citric acid was also observed in the samples. The optimal MgO–CeO 2 composite using the Ce/Mg molar ratio of 0.05 exhibited a high surface area (333 m 2 /g) and enhanced CO 2 capture capacity (10.4 wt%) at 30 °C. All the composites showed a fast sorption rate that reached approximately 70% of the capacity within 3 min. The analysis of the CO 2 -TPD profiles and XPS spectra indicated that even a relatively small amount of carbonaceous residues after calcinations contributed to retaining more amounts of strong basic sites and consequently resulted in the fast sorption rate. In the cyclic test, the sorption capacity is reasonably stable from the 2nd cycle onwards. The simple preparation via cerium doping and the citric acid-assisted sol-gel combustion can contribute to the development of sorbents for post-combustion as well as pre-combustion CO 2 capture.

High-Temperature and High-Pressure Particle Attrition Characteristics of Dry Sorbents for Pre-Combustion CO<sub>2</sub> Capture by a Gas Jet in a Bubbling Fluidized Bed

High-Temperature and High-Pressure Particle Attrition Characteristics of Dry Sorbents for Pre-Combustion CO<sub>2</sub> Capture by a Gas Jet in a Bubbling Fluidized Bed

Ultra-high surface area mesoporous carbons for colossal pre combustion CO2 capture and storage as materials for hydrogen purification

Mesoporous carbons (with up to 95% of pore volume from mesopores) with surface area and pore volume of ∼4000 m2 g−1 and ∼3.6 cm3 g−1, respectively, are excellent CO2 absorbers under pre combustion conditions and can store 55 mmol g−1 (i.e., 2.42 g g−1) or 930 g l−1 at 25 °C and 50 bar.

Exceptionally stable Bakelite-type polymers for efficient pre-combustion CO2capture and H2purification

Pre-combustion CO2capture enables cleaner energy production from fossils. This involves separation of CO2from high pressure CO2/H2mixtures. Here we show high working capacity for such separation from Bakelite-type porous polymers.

Optimization and Characterization of an Amino Acid Ionic Liquid and Polyethylene Glycol Blend Solvent for Precombustion CO2 Capture: Experiments and Model Fitting

Amino acid ionic liquids are green solvents with low toxicities and properties suitable for precombustion CO2 capture, such as high CO2 absorption, good thermal stability, and negligible vapor pressure. However, their high viscosities and relatively high costs have hampered their industrial applications. In this work, we systematically studied the amino acid ionic liquid tetrabutylphosphonium glycinate ([P4444][Gly]) and its blends with the low-cost and less viscous cosolvent poly(ethylene glycol) (PEG400). The concentration of the blend solvent was optimized with respect to CO2 solubility, regeneration efficiency, and cyclic capacity. The solubilities of CO2 in [P4444][Gly], PEG400, and their blends of four different concentrations were measured experimentally in the temperature range of 60–140 °C and up to a pressure of 17 bar. The results showed that the CO2 solubility increased with increasing ionic liquid concentration in the blend and decreased with increasing temperature. The optimum CO2 absorption...

Experimental Investigation of Precombustion CO2 Capture Using a Fixed Bed of Coal Particles in the Presence of Tetrahydrofuran

This work presents a hybrid gas adsorption and hydrate formation process for CO2 capture from fuel gas (40 mol % CO2/H2) using a fixed bed reactor (FBR) of coal particles. To better understand the CO2 capture performance of this hybrid process, the effects of particle size and tetrahydrofuran (THF) concentration on gas consumption and CO2 selectivity were experimentally investigated at 100% liquid saturation of the fixed bed. The experiments were conducted at 274.2 K with the initial pressure fixed at 3.0 MPa. The results indicated that medium-sized coal particles (0.5–1.0 mm) are more favorable than small (0.1–0.5 mm) and large (1.0–3.0 mm) coal particles as higher gas uptake, CO2 recovery, and separation factor were obtained in the FBR filled with medium-sized coal particles. Gas uptake was observed to increase while increasing THF concentration from 1.0 to 5.6 mol %, but the optimum CO2 selectivity was obtained at 1.0 mol % THF. The gas uptake obtained at 1.0 mol % THF in the FBR of coal particles was ...

Lignite-fired air-blown IGCC systems with pre-combustion CO2capture

Detailed analyses based on mass and energy balances of lignite-fired air-blown gasification-based combined cycles with CO2 pre-combustion capture are presented and discussed in this work. The thermodynamic assessment is carried out with a proprietary code integrated with Aspen Plus® to carefully simulate the selective removal of both H2S and CO2 in the acid gas removal station. The work focuses on power plants with two combustion turbines, with lower and higher turbine inlet temperatures, respectively, as topping cycle. A high-moisture lignite, partially dried before feeding the air-blown gasification system, is used as fuel input. Because the raw lignite presents a very low amount of sulfur, a particular technique consisting of an acid gas recycle to the absorber, is adopted to fulfill the requirements related to the presence of H2S in the stream to the Claus plant and in the CO2-rich stream to storage. Despite the operation of the H2S removal section representing a significant issue, the impact on the performance of the power plant is limited. The calculations show that a significant lignite pre-drying is necessary to achieve higher efficiency in case of CO2 capture. In particular, considering a wide range (10–30 wt.%) of residual moisture in the dried lignite, higher heating value (HHV) efficiency presents a decreasing trend, with maximum values of 35.15% and 37.12% depending on the type of the combustion turbine, even though the higher the residual moisture in the dried coal, the lower the extraction of steam from the heat recovery steam cycle. On the other hand, introducing the specific primary energy consumption for CO2 avoided (SPECCA) as a measure of the energy cost related to CO2 capture, lower values were predicted when gasifying dried lignite with higher residual moisture content. In particular, a SPECCA value as low as 2.69 MJ/kgCO2 was calculated when gasifying lignite with the highest (30 wt.%) residual moisture content in a power plant with the advanced combustion turbine. Ultimately, focusing on the power plants with the advanced combustion turbine, air-blown gasification of lignite brings about a reduction in HHV efficiency equal to almost 1.5 to 2.8 percentage points, depending on the residual moisture in the dried lignite, if compared with similar cases where bituminous coal is used as fuel input. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of Syngas Constituents on CdO- and MgO-Based Sorbents for Pre-combustion CO2 Capture

Magnesium oxide/cesium carbonate composites as well as cadmium oxide/sodium halide mixtures have been previously described as potential candidates for pre-combustion carbon dioxide capture. Here, the effects of water and hydrogen alongside CO2 were examined in simulated partial pressure swing experiments analyzed by thermogravimetric means. It was shown that the magnesium/cesium sorbents are tolerant to hydrogen at a temperature of 370 °C and that their working capacities over 25 cycles are enhanced by the addition of water to the sorption gas stream. The cadmium/sodium iodide sorbent showed a stable working capacity for 23 sorption cycles at 285 °C, but tended to lose working capacity after that point. At 305 °C, a significant loss in capacity was observed during sorption cycling. As reduction in an inert gas/hydrogen mixture was not found to commence below 400 °C, a halide promoter disintegration mechanism is assumed to be the cause of the decay. The sorption of hydrogen sulfide was also examined. Both ...

Effect of Steam on the Reactivity of MgO-Based Sorbents in Precombustion CO2 Capture Processes

Low-cost MgO-based sorbents were prepared through modification of natural dolomite and were found to be capable of capturing CO2 from coal gas at elevated temperatures and pressures (i.e., 330° 20 bar). The effect of steam on the reactivity of the MgO sorbents was investigated experimentally. The results indicate that the presence of steam significantly improves the overall rate of the carbonation reaction through two different mechanisms. The presence of steam improves the intrinsic rate of the carbonation reaction by altering the carbonation reaction pathway through the formation of more reactive transient MgO·H2O•/Mg(OH)2• intermediate compounds. The formation of the transient intermediate compounds with larger molar volume (compared with MgO) results in the expansion of the inner pores, which lowers diffusion resistance to the reactant gas (i.e., CO2) during carbonation.

Design optimization of a pre-combustion CO 2 capture plant embedding experimental knowledge

Abstract This work is focused on the design optimization of a pre-combustion CO2 capture plant comprising a sweet high-temperature water–gas shift process and an integrated H2S and CO2 removal process using a mixture of dimethylethers of polyethylene glycol as physical solvent. The steady-state model of the commercial-scale plant has been derived from pilot plant models, which have been extensively validated against experimental data obtained from the pre-combustion CO2 capture facility realized at the Buggenum IGCC power station in the Netherlands. A two-phase optimization-based design approach suited to the use of process simulator environments has been adopted. In the first phase, global design decisions at plant level are evaluated, targeting the minimization of the energy consumption due to CO2 capture. These are the extent of CO conversion in the water–gas shift unit and the percentage of CO2 capture in the removal unit. An optimization of both global design variables is presented considering (i) a wide range of carbon capture targets, (ii) deactivation of catalyst activity throughout the catalyst life and (iii) different operational limits of the steam/CO ratio in the water–gas shift unit. Experimental data from the pilot plant has been used to determine the rate of catalyst deactivation and the operational limits of steam/CO ratio. The second phase of the design procedure targets the local decision variables at unit level. Two studies are presented focusing on: (1) the design of the solvent regeneration and CO2 compression section, and (2) the impact of the solvent temperature on the energy consumption and equipment cost of the removal unit. The design optimization revealed that the specific energy consumption of the pre-combustion capture unit can be reduced by 10% when operating at a minimum molar steam/CO ratio of 1.5 in comparison to the current vendor suggestion of 2.65. These energy savings come at the cost of a lower optimal carbon capture rate, namely 78% instead of 87.5% as reported in the preliminary design.

Mixed matrix membranes composed of two-dimensional metal–organic framework nanosheets for pre-combustion CO2 capture: a relationship study of filler morphology versus membrane performance

Mixed matrix membranes containing metal–organic frameworks were fabricated for pre-combustion CO2 capture.

Investigation of the capacity decay of a CdO–NaI mixed sorbent for pre-combustion CO2 capture

CdO–NaI mixtures for pre-combustion CO2 sorption were found to lose iodine by oxidation of iodide to higher-oxidised species. Morphology changes and the reversibility of the decay reaction were also investigated.

Dynamic Modeling and Validation of a Precombustion CO2 Capture Plant for Control Design

In view of the increasing share of electricity produced by renewable energy sources, transient operation of decarbonized power plants is gaining more relevance. This is due to the inherent fluctuating operation of wind or solar plants. Accurate physically based dynamic models are important tools to study the interaction between power plant and CO2 capture unit during dynamic operation. Moreover, such models are indispensable to design appropriate control systems aimed at improvement of dynamic performance. This paper documents the development of dynamic components as well as system models of a precombustion CO2 capture unit applied to integrated gasification combined cycle (IGCC) systems following an object-oriented modeling approach. The models have been implemented by means of the Modelica language into an open source software library. The fluid properties are computed with accurate thermodynamic models implemented within an in-house property package which is interfaced with the Modelica process models. Comprehensive model validation has been performed at component, subsystem, and system level by comparison against experimental measurements obtained from various open- and closed-loop transient tests at the CO2 capture pilot plant situated at the Buggenum IGCC power station. Results are in satisfactory agreement, considering the main process mass flow and temperature variables. To demonstrate the use of validated, dynamic process models, a control design study is presented whereby a control strategy based on feed-forward, feed-back, and cascade control has been implemented and tested with the aim to improve dynamic performance of the capture unit. It can be concluded that prompt syngas load variation is a feasible operating mode for precombustion CO2 capture units featuring sophisticated control systems. The software library containing the validated component and system models serves as a reliable foundation for the development of large-scale precombustion capture unit models.

Resource scarcity in palladium membrane applications for carbon capture in integrated gasification combined cycle units

Abstract Recently, many reviews on pre-combustion CO 2 capture (CCS) in an IGCC plant have been focused on the techno-economic performance of palladium-based membrane reactor modules downstream of conventional steam reforming or shift reactors. Although the determination and minimisation of the amount of palladium necessary for a specific power production capacity has been the target of many research studies, surprisingly little attention has been paid in the open literature to the availability of this metal in the large quantities required for large scale applications. To fill this gap, the scope of this work was to compare the amount of palladium needed for pre-combustion CCS with Pd-membranes and the available production capacity of palladium. Two specific techno-economic studies with a different net IGCC power output were selected from the literature. In each case, the amount of palladium that is necessary for the plant to be in operation was compared with the world supply and demand for palladium. The results show that even for a power plant of “only” 1 GWe net electricity production utilizing membranes with the best reported performance, a relatively large (∼0.7%) amount of palladium is required compared to the total world supply. Considering the total worldwide electricity production from fossil fuels (14,455 TWh in 2010) a tremendous increase in the world supply of Palladium would be required to redirect from the traditional IGCC power plants without CO 2 capture units to the new membrane technology. We conclude that large scale pre-combustion capture of CO 2 using palladium membranes seems to be unfeasible and research on Pd-based membrane reactors should focus on small(er) scale applications.

Multiple sorption cycles evaluation of cadmium oxide–alkali metal halide mixtures for pre-combustion CO2 capture

Both powdered and pelletised CdO–NaI composite CO2 sorbents were tested in reversible CO2 sorption experiments. Sorption capacity stability improved in moist environments and if pre-treated in inert gas.