Pre-combustion Carbon Dioxide Capture Research Articles

Highly efficient separation and equilibrium recovery of H2/CO2 in hydrate-based pre-combustion CO2 capture

Gas hydrate-based CO2 capture processes have attracted considerable attention due to their potentials for energy-efficient pre-combustion CO2 capture. Recent investigations have explored the use of tailored-wettability porous silica gels, highlighting benefits in thermodynamic and kinetic efficiencies, specifically characterized by low energy requirements and rapid formation. However, achieving high purity levels for both H2 and CO2 is crucial for practical implementation. Consequently, identifying and optimizing an effective separation route becomes imperative. In this study, we examined the thermodynamic stability, gas uptake, and separation factors of THF (5.56 mol%) + H2 + CO2 hydrates with varying compositions (H2:CO2 = 80:20, 60:40, 30:70, or 20:80 mol%) in C0 and C1 silica gel (functionalized by monofunctional alkylsilanes (X-(CH3)2-Si-Cn)) systems with SDS (0 or 500 ppm). Pressure-composition diagrams for THF + H2 + CO2 systems in C0 and C1 silica gel were meticulously measured. Notably, the C1 silica gel system without SDS demonstrated good thermodynamic stability, substantial gas uptake, and a significant separation factor. Based on the pressure-composition diagram of the C1 silica gel system, we proposed a highly efficient route for separating H2 and CO2. This proposed cyclic process involves a three-stage reactor and achieve to gas hydrate-based pre-combustion CO2 capture, yielding a purity of approximately 91 % H2 and 94 % CO2. The present findings provide valuable insights into optimizing the wettability of porous media and efficient separation routes, demonstrating the feasibility of a gas hydrate-based pre-combustion carbon dioxide capture process.

Energy and exergy analyses of a novel integrated process configuration for tri-generation heat, power and liquefied natural gas based on biomass gasification

Using renewable sources like biomass is a proper solution for solving the problem of deficiency of fossil energy simultaneously with the increasing trend of energy consumption in the world.In the present study, an integrated system of liquefied natural gas production was investigated through rice husk gasification and providing the needed power of the cycle by integrated gasification combined cycle, in a way that surplus heat generated in integrated gasification combined cycle was used in absorption refrigeration system to reduce liquefied natural gas cycle consumed power which resulted in the reduction of the cycle specific power from 0.2405 kWh/kg to 0.1794 kWh/kg. Pre-combustion carbon dioxide capture was used to absorb the generated carbon dioxide of the integrated system and its effect on system operation was studied and reported. Sensitivity analysis was performed by investigating the effect of generated nitrogen injection to the combustion chamber and also the effect of the generated steam rate on the suggested integrated system operation. Results show that combined heat and power efficiency gets to 48% in whole with the increase of steam production rate to 7 kg/s. The results obtained from the exergy analysis show that overall exergy efficiency and total irreversibility of the proposed system is 74.10% and 63,242 kW, respectively.

Technical and Economic Assessments of Ionic Liquids for Pre-Combustion CO2 Capture at IGCC Power Plants

This study evaluates the feasibility and cost of ionic liquids (ILs) for precombustion carbon dioxide (CO2) capture at integrated gasification combined cycle power plants. The ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is selected as a physical solvent for CO2 capture. Using newly developed performance and cost models, our analysis shows that the energy penalty of the IL-based capture system mainly arises from powering various compressors and solvent pumps, and compressors and absorbers are the dominant capital cost components. Using the Integrated Environmental Control Model (IECM) for power plant assessments, the cost of CO2 avoided by the IL-based capture system is estimated to be $62/t CO2 in constant 2011 USD. The preliminary comparisons of performance and cost between IL- and Selexol-based capture systems show that an IL-based capture system could be a viable alternative to current liquid solvent processes.

Optimization of pre-combustion capture for thermal power plants using Pinch Analysis

Carbon dioxide emissions from the chimneys of thermal power plants create major environmental risks. Therefore, an important step toward reducing the emissions in these power plants can be the carbon dioxide pre-combustion capture process. In this paper, a 150 MW thermal steam cycle power plant fueled by bagasse was studied. The power plant has an efficiency of 32.74%, and emits 246.52 t/h carbon dioxide. First, the design and simulation of a suggested pre-combustion carbon dioxide capture process was outperformed. In this process, the amount of carbon dioxide separation and capture using mono ethanol amine (MEA) 30 wt% as solvent is 90%. In this condition, the mass flow of bagasse was increased about 60% to keep the plant efficiency constant. At the same time, the energy loss as a result of the addition of the carbon dioxide recovery unit was around 11%. The process was optimized through Pinch Analysis to reduce energy waste and fuel flow. Moreover, it was indicated that power plant efficiency could be increased around 8% by integrating the hot exhaust gases from the gasification unit with power plant boiler using a heat recovery steam generation (HRSG) unit. With this modification, bagasse consumption was decreased by 23%.

Comparison of the efficiency of carbon dioxide capture by sorption-enhanced water–gas shift and palladium-based membranes for power and hydrogen production

Pre-combustion capture of carbon dioxide requires the industrial separation of carbon dioxide from hydrogen-rich streams. The present study analyses the thermodynamic efficiency penalty of this separation step and the achievable carbon capture ratio, with particular focus on high-temperature separation technologies: sorption-enhanced water–gas shift (SEWGS) and palladium membranes. Twelve different cases have been simulated, starting from coal-derived syngas or from natural gas derived reformate, using carbon dioxide capture by conventional absorption, SEWGS, and palladium membranes, and producing hydrogen-rich fuel for power production or pure hydrogen. For the production of decarbonised fuel from coal syngas, SEWGS always yields the lowest efficiency penalty per unit of carbon dioxide captured. For the production of pure hydrogen from coal syngas, SEWGS has a significantly higher carbon capture ratio than the alternatives while palladium membranes yield the lowest efficiency penalty per unit of carbon dioxide captured. For the production of decarbonised fuel from natural gas reformate, SEWGS is the most efficient technology in terms of efficiency penalty. For the production of pure hydrogen from natural gas syngas, palladium membranes yield the lowest efficiency penalty.

Environmental Performance of Hypothetical Canadian Pre-Combustion Carbon Dioxide Capture Processes Using Life-Cycle Techniques

The methodology of life-cycle assessment was applied in order to evaluate the environmental performance of a hypothetical Saskatchewan lignite-fueled Integrated Gasification Combined Cycle (IGCC) electricity generation, with and without pre-combustion carbon dioxide (CO2) capture from a full life-cycle perspective. The emphasis here is placed on environmental performance associated with air contaminants of the comparison between IGCC systems (with and without CO2 capture) and a competing lignite pulverized coal-fired electricity generating station in order to reveal which technology offers the most positive environmental effects. Moreover, ambient air pollutant modeling was also conducted by using American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) air dispersion modeling to determine the ground-level concentration of pollutants emitted from four different electricity generating stations. This study assumes that all stations are located close to Estevan. The results showed a significant reduction in greenhouse gas (GHG) emissions and acidification potential by applying both post-combustion and pre-combustion CO2 capture processes. The GHG emissions were found to have reduced by 27%–86%, and IGCC systems were found to compare favorably to pulverized coal systems. However, in other environmental impact categories, there are multiple environmental trade-offs depending on the capture technology used. In the case of post-combustion capture, it was observed that the environmental impact category of eutrophication potential, summer smog, and ozone depletion increased due to the application of the CO2 capture process and the surface mining coal operation. IGCC systems, on the other hand, showed the same tendency as the conventional coal-fired electricity generation systems, but to a lesser degree. This is because the IGCC system is a cleaner technology that produces lower pollutant emission levels than the electricity generating station; thus, the benefits of capture are reduced on a comparative basis. The results from air dispersion analysis showed that the maximum ground-level concentrations of pollutants from all electricity generating stations are in compliance with all air quality standards, except for Co, Pb and Ni. The IGCC with capture revealed the lowest nitrogen dioxide (NO2) ground-level concentration compared to all other scenarios. Moreover, IGCC systems both with and without pre-combustion CO2 capture revealed no ground-level concentration of trace elements. This is because the IGCC system operates with an acid gas cleaning process that removes most of the trace contaminants from the syngas.

A systematic kinetic study to evaluate the effect of tetrahydrofuran on the clathrate process for pre-combustion capture of carbon dioxide

THF (Tetrahydrofuran) is the most commonly employed promoter for the gas hydrate formation pertaining to applications like carbon dioxide capture and energy storage (for natural gas and hydrogen). In this work, THF was investigated as a promoter for pre-combustion capture of carbon dioxide (CO2) from fuel gas mixture (CO2/H2) in a systematic manner. 0.5, 1.0, 3.0 and 5.56 mol% THF solution were employed with different driving force conditions to study the effect of pressure, temperature and composition of gases in hydrate. The kinetic performance of the CO2/H2/THF gas hydrate system was evaluated by reviewing the IT (induction time), normalized gas uptake, normalized rate of hydrate formation and the hydrate phase composition. The optimum operating conditions and optimum THF concentration in this study was found to be 6.0 MPa, 282.2 K, and 5.56 mol% THF respectively. 5.56 mol% THF solution yielded an average gas uptake of 13.9 mmol of gas/mol of water for hydrate growth and an average normalized rate of hydrate formation of 1679.8 mmol s−1 m−3.

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 ...

Simulation of an integrated gasification combined cycle with chemical-looping combustion and carbon dioxide sequestration

Chemical-looping combustion is an interesting technique that makes it possible to integrate power generation from fuels combustion and sequestration of carbon dioxide without energy penalty. In addition, the combustion chemical reaction occurs with a lower irreversibility compared to a conventional combustion, leading to attain a somewhat higher overall thermal efficiency in gas turbine systems. This paper provides results about the energetic performance of an integrated gasification combined cycle power plant based on chemical-looping combustion of synthesis gas. A real understanding of the behavior of this concept of power plant implies a complete thermodynamic analysis, involving several interrelated aspects as the integration of energy flows between the gasifier and the combined cycle, the restrictions in relation with heat balances and chemical equilibrium in reactors and the performance of the gas turbines and the downstream steam cycle. An accurate thermodynamic modeling is required for the optimization of several design parameters. Simulations to evaluate the energetic efficiency of this chemical-looping-combustion based power plant under diverse working conditions have been carried out, and a comparison with a conventional integrated gasification power plant with precombustion capture of carbon dioxide has been made. Two different synthesis gas compositions have been tried to check its influence on the results. The energy saved in carbon capture and storage is found to be significant and even notable, inducing an improvement of the overall power plant thermal efficiency of around 7% in some cases.

Enhanced Precombustion Capture of Carbon Dioxide by Gas Hydrate Formation in Water-in-Oil Emulsions

In this work, we reported enhanced kinetics of gas hydrate formation in water-in-oil (W/O) emulsions for the precombustion capture of carbon dioxide. The experiments were carried out at 274.2 K and in the pressure range of 3.0–6.0 MPa. The parameters of induction time, gas uptake, rate of hydrate growth, CO2 recovery, and separation factor were determined to evaluate the performance of the W/O emulsions for CO2 capture from a fuel gas (40 mol % CO2/H2). It was found that shorter induction time and higher gas uptake were obtained while the water–oil volume ratio (WOR) was reduced from 70% to 20%, and gas hydrates were observed to grow faster at low WORs. The CO2 recovery and CO2 concentration in the hydrate phase decreased with WOR decreasing from 70% to 20%. At a fixed WOR, higher pressure resulted in shorter induction time and higher gas uptake, but CO2 concentration in the hydrate phase decreased. The highest value of CO2 concentration in the hydrate phase achieved 84 mol % at 3.0 MPa and WOR = 70%, and the highest value of gas uptake obtained in W/O emulsions was 39.5 mmol of gas/mol of water at 3.0 MPa and WOR = 20%. This gas uptake was much higher than that obtained in stirred reactors in the presence of CP or THF and was comparable with that obtained in the fixed bed of silica sand in the presence of THF or TBAB. The result indicated that the W/O emulsions employed in this work are a viable option to enhance hydrate formation for the precombustion capture of carbon dioxide.

Surface-modified spherical activated carbon materials for pre-combustion carbon dioxide capture

Carbon beads exhibiting potential in practical pre-combustion CO2 capture were prepared.

Life cycle assessment of a hypothetical Canadian pre-combustion carbon dioxide capture process system

The methodology of life cycle assessment was applied for evaluating the environmental performance of a Saskatchewan lignite integrated gasification combined cycle (IGCC)-based electricity generation plant with and without the pre-combustion CO2 capture process. A comparison between the IGCC systems (with and without CO2 capture) and the competing lignite pulverized coal electricity generating station was conducted to reveal which technology offers more positive environmental effects. The results showed significant reduction of GHG emissions where both post- and pre-combustion CO2 capture processes are applied. With the application of the CO2 removal technology, GHG emissions were reduced by 27–86%. The performances of the IGCC systems were superior to those of the pulverized coal systems. However, in terms of other environmental impacts, multiple environmental trade-offs are involved depending on the capture technology. For the post-combustion CO2 capture process system, it was observed that the environmental impact was shifted from the air compartment to the soil and water compartments. The IGCC systems showed the same tendency of shifting from air pollution to soil and water pollution, but the amount of pollution is less significant. This is likely because the IGCC system operates at higher efficiencies; hence, it requires less fuel and produces fewer emissions.

Enhanced kinetics for the clathrate process in a fixed bed reactor in the presence of liquid promoters for pre-combustion carbon dioxide capture

In this work, we present enhanced kinetics of hydrate formation for the clathrate process in the presence of two liquid promoters namely THF (tetrahydrofuran) and TBAB (tetra-n-butyl ammonium bromide) in a FBR (fixed bed reactor) for pre-combustion capture of CO2. Silica sand was used as a medium to capture CO2 from CO2/H2 gas mixture by hydrate crystallisation. Experiments were performed at different temperatures (274.2 K and 279.2 K) and 6.0 MPa to determine the total gas uptake, induction time and rate of hydrate formation. The observed trends indicated that higher driving force resulted in higher gas consumption and significantly reduced induction time. For the same driving force, higher gas consumption and shorter induction time was achieved by THF as compared to TBAB. 5.53 mol% THF attained higher gas consumption than 1.0 mol% THF whereas 3.0 mol% TBAB attained lower gas consumption than 0.3 mol% TBAB. A highest gas uptake of 51.95 (±5.183) mmol of gas/mol of water and a highest rate of 51.21(±8.91) mol.min−1.m−3 were obtained for 5.53 mol% THF at 6.0 MPa and 279.2 K. Overall, this study indicated better hydrate formation kinetics with the use of THF in an FBR configuration for CO2 capture from a fuel gas mixture.

Thermodynamic and Kinetic Verification of Tetra-n-butyl Ammonium Nitrate (TBANO3) as a Promoter for the Clathrate Process Applicable to Precombustion Carbon Dioxide Capture

In this study, tetra-n-butyl ammonium nitrate (TBANO3) is evaluated as a promoter for precombustion capture of CO2 via hydrate formation. New hydrate phase equilibrium data for fuel gas (CO2/H2) mixture in presence of TBANO3 of various concentrations of 0.5, 1.0, 2.0, 3.0, and 3.7 mol % was determined and presented. Heat of hydrate dissociation was calculated using Clausius-Clapeyron equation and as the concentration of TBANO3 increases, the heat of hydrate dissociation also increases. Kinetic performance of TBANO3 as a promoter at different concentrations was evaluated at 6.0 MPa and 274.2 K. Based on induction time, gas uptake, separation factor, hydrate phase CO2 composition, and rate of hydrate growth, 1.0 mol % TBANO3 solution was found to be the optimum concentration at the experimental conditions of 6.0 MPa and 274.2 K for gas hydrate formation. A 93.0 mol % CO2 rich stream can be produced with a gas uptake of 0.0132 mol of gas/mol of water after one stage of hydrate formation in the presence of 1.0 mol % TBANO3 solution. Solubility measurements and microscopic images of kinetic measurements provide further insights to understand the reason for 1.0 mol % TBANO3 to be the optimum concentration.

A New Porous Material to Enhance the Kinetics of Clathrate Process: Application to Precombustion Carbon Dioxide Capture

In this work, the performance of a new porous medium, polyurethane (PU) foam in a fixed bed reactor for carbon dioxide separation from fuel gas mixture using the hydrate based gas separation process is evaluated. The kinetics of hydrate formation in the presence of 2.5 mol % propane as thermodynamic promoter was investigated at 4.5, 5.5, and 6.0 MPa and 274.2 K. Significantly higher gas consumption and water conversion to hydrate was achieved when PU foam was employed. PU foam as a porous medium can help convert 54% of water to hydrate in two hours of hydrate formation. In addition the induction times were very low (<3.67 min at 6.0 MPa). A normalized rate of hydrate formation of 64.48 (±3.82) mol x min(-1) x m(-3) was obtained at 6.0 MPa and 274.2 K. Based on a morphological study, the mechanism of hydrate formation from water dispersed in interstitial pore space of the porous medium is presented. Finally, we propose a four step operation of the hydrate based gas separation process to scale up.

Medium pressure hydrate based gas separation (HBGS) process for pre-combustion capture of carbon dioxide employing a novel fixed bed reactor

This work presents an effective medium pressure hydrate based gas separation (HBGS) process for pre-combustion carbon dioxide capture in a novel fixed bed column. 2.5mol% propane was added to the fuel gas mixture as an additive to decrease the operating pressure of the HBGS process. Hydrate formation kinetics was investigated at three different pressures (4.5, 5.5 and 6.0MPa respectively) and at 274.15K. The performance of silica sand and silica gel as a medium was evaluated. In silica sand bed, multiple nucleation events were observed. In silica gel bed, the gas uptake and water conversion to hydrates was significantly low at any given driving force than that obtained in silica sand bed. Experiments at different water saturation levels (50, 75 and 100%) in silica sand bed were investigated at 6.0MPa and 274.15K. It was found that at 50% water saturation, gas consumed for hydrate formation and water conversion to hydrates was almost three times that at 100% saturation. Water to hydrate conversions of up to 64.3% was achieved after 4h of hydrate formation for the 50% water saturated silica sand bed. Our study presents an opportunity to scale up the HBGS process for CO2 capture with enhanced kinetics by employing a fixed bed reactor configuration. Decomposition experiments at a driving force of ΔT of 10K and 23K were carried out to recover the gas consumed for hydrate formation and it was found that ΔT of 23K was sufficient to recover the hydrated gas.

Investigation of transport and mechanical properties of hollow fiber membranes containing ionic liquids for pre-combustion carbon dioxide capture

Polymeric hollow fiber supported ionic liquid membranes were fabricated utilizing Matrimid® and 1-hexyl-3-methylimidalzolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]) as the selected polymeric and ionic liquid materials, respectively. The fibers were spun via a dry–wet nonsolvent-induced phase separation procedure, employing a single layer spinneret extrusion system. Four different types of membranes were fabricated using four morphologically different hollow fiber supports. These membranes take advantage of the fiber morphology combined with a supported ionic liquid to enable more efficient mass transfer than flat membranes. Initially the membranes had a low separation performance for CO2/H2; however, upon changing the porosity and support morphology, better permeance and selectivity were achieved. Transport properties of CO2 and H2 are reported for hollow fiber membranes containing an ionic liquid in the temperature range from 37 to 150°C. The glass transition temperature, Young's modulus, and tensile strength are also reported. The volume fractions of polymer, macro-voids, and micro-voids were determined using a combination of density measurements and an SEM image analysis technique. These quantities were then used to calculate both the bulk fiber porosity and the porosity of the micro-porous region. The surface porosity was also estimated by image analysis. It was observed that the transport and mechanical properties of the fiber were influenced by porosity.

Hydrate-based pre-combustion capture of carbon dioxide in the presence of a thermodynamic promoter and porous silica gels

In this study, the feasibility of the hydrate-based pre-combustion capture of carbon dioxide in the presence of a thermodynamic promoter and porous silica gels was examined through stability condition measurements, gas uptake measurements, and microscopic analyses. When a fuel gas mixture of H2 (60%) and CO2 (40%) was used for gas hydrate formation, the addition of tetrahydrofuran (THF) yielded significantly enhanced hydrate stability conditions. Silica gels with a nominal diameter of 100.0nm demonstrated increased gas consumption during gas hydrate formation, indicating higher conversion of water into gas hydrate. With only one step of hydrate formation, CO2 concentrations of higher than 90% were achieved in the hydrate phase for all cases. It can be concluded that the hydrate phase composition is affected primarily by the cage occupancies of guest gases in the hydrate lattices whereas the vapor phase composition is strongly influenced by the conversion of water to gas hydrate and also partially by the cage occupancy of CO2 in the hydrate phase. From powder X-ray diffraction (PXRD) patterns and Raman spectra, it was confirmed that the H2 (60%)+CO2 (40%) gas mixture forms structure I hydrate and the inclusion of THF induces the formation of structure II hydrate.

Pre-combustion capture of carbon dioxide in a fixed bed reactor using the clathrate hydrate process

Hydrate based gas separation (HBGS) process with silica sand and silica gel as contact medium was employed to capture CO2 from fuel gas mixture. Gas uptake measurement at three different pressures (7.5, 8.5 and 9.0 MPa) and 274.15 K were conducted for hydrate formation kinetics and overall conversion of water to hydrate, rate of hydrate formation were determined. Water conversion of up to 36% was achieved with silica sand bed compared to 13% conversion in the silica gel bed. Effect of driving force on the rate of hydrate formation and gas consumption was significant in silica sand bed whereas it was found to be insignificant in silica gel bed. Hydrate dissociation experiments by thermal stimulation (at constant pressure) alone and a combination of depressurization and thermal stimulation were carried out for complete recovery of the hydrated gas. A driving force of 23 K was found to be sufficient to recover all the hydrated gas within 1 h. This study indicates that silica sand can be an effective porous media for separation of CO2 from fuel gas when compared to silica gel.

Performance of a Multiple-Injection Dry Low NOx Combustor With Hydrogen-Rich Syngas Fuels

An oxygen-blown integrated coal gasification combined cycle (IGCC) plant with precombustion carbon dioxide capture and storage (CCS) is one of the most promising means of zero-emission generation of power from coal. In an IGCC plant with CCS, hydrogen-rich syngas with a wide variation of hydrogen contents is supplied to a gas turbine. Such hydrogen-rich syngas poses a great challenge to a low NOx combustor based on premixed combustion technology, because its high flame speed, low ignition energy, and broad flammability limits can cause flashback and/or autoignition. On the contrary, a diffusion combustor suffers from the high flame temperature of syngas and the resulting high NOx emission. The authors applied a “multi-injection burner” concept to a preliminary burner for hydrogen-rich syngas simulating that from IGCC with CCS. In a preliminary experiment under atmospheric pressure, the multi-injection burner worked without any flashback or any blowout. A prototype multicluster combustor based on the results of that preliminary study was made to be a dry low NOx combustor for hydrogen-rich syngas of IGCC with CCS. It was tested in experiments, which were carried out under medium pressure (0.6 MPa) using test fuels simulating syngas from IGCC with a 0% carbon capture rate, a 30% carbon capture rate, and a 50% carbon capture rate. The test fuels contained hydrogen, methane, and nitrogen, and had a hydrogen content ranging from 40% to 65%.The following conclusions were drawn from the test results: (1) the tested combustor allows the stable combustion of fuels simulating 0%, 30%, and 50% CCS, (2) a convex perforated plate swirler is effective to suppress combustion oscillation, which allows NOx emissions to be less than 10 ppm through the variation of fuel simulating 0%, 30%, and 50% CCS, (3) the extended stable combustion region and enhanced entrainment and mixing due to the convex perforated plate improves the cooling of the combustor liner metal to be less than the liner metal temperature criterion.