Combined CO2 Capture Research Articles

The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual Function Materials (DFM)

Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru as a promising catalytic solution for combining both approaches. The Ru-Na2CO3 DFM deposited on Al2O3 captures CO2 from a flue gas and catalytically converts it to synthetic natural gas (i.e., methane) using H2 generated from renewable sources. The Ru in the DFM, in combination with H2, catalytically hydrogenates both adsorbed CO2 and the bulk Na2CO3, forming methane. The depleted sites adsorb CO2 through a carbonate reformation process and in addition adsorb CO2 on its surface. This material functions well in O2- and H2O-containing flue gas where the favorable Ru redox property allows RuOx, formed during flue gas exposure, to be reduced during the hydrogenation cycle. As a combined CO2 capture and utilization scheme, this technology overcomes many of the limitations of the conventional liquid amine-based CO2 sorbent technology.

Thermodynamic modeling of NH3-CO2-SO2-K2SO4-H2O system for combined CO2 and SO2 capture using aqueous NH3

A new application of aqueous NH3 based post-combustion CO2 and SO2 combined capture process was proposed to simultaneously capture CO2 and SO2, and remove sulfite by solid (K2SO4) precipitation method. The thermodynamic model of the NH3-CO2-SO2-K2SO4-H2O system for the combined CO2 and SO2 capture process was developed and validated in this work to analyze the heat of CO2 and SO2 absorption in the NH3-CO2-SO2-H2O system, and the K2SO4 precipitation characteristics in the NH3-CO2-SO2-K2SO4-H2O system. The average heat of CO2 absorption in the NH3-CO2-H2O system at 40°C is around −73kJ/mol CO2 in 2.5wt% NH3 with CO2 loading between 0.2 and 0.5 C/N. The average heat of SO2 absorption in the NH3-SO2-H2O system at 40°C is around −120kJ/mol SO2 in 2.5wt% NH3 with SO2 loading between 0 and 0.5S/N. The average heat of CO2 absorption in the NH3-CO2-SO2-H2O system at 40°C is 77, 68, and 58kJ/mol CO2 in 2.5wt% NH3 with CO2 loading between 0.2 and 0.5 C/N, when SO2 loading is 0, 0.1, 0.2S/N, respectively. The solubility of K2SO4 increases with temperature, CO2 and SO2 loadings, but decreases with NH3 concentration in the CO2 and SO2 loaded aqueous NH3. The thermodynamic evaluation indicates that the combined CO2 and SO2 capture process could employ the typical absorption/regeneration process to simultaneously capture CO2 and SO2 in an absorber, thermally desorb CO2 in a stripper, and feasibly remove sulfite (oxidized to sulfate) content by precipitating K2SO4 from the lean NH3 solvent after the lean/rich heat exchanger.

On-site concurrent carbon dioxide sequestration from flue gas and calcite formation in ossein effluent by a marine cyanobacterium Phormidium valderianum BDU 20041

In the recent past, there has been an upsurge in the use of microalgae to capture CO2. Microalgae are the most productive biological systems for generating biomass; they produce much more biomass than terrestrial organisms. In the present study, a cyanobacterium was exploited for combined CO2 capture and ossein effluent treatment. Phormidium valderianum BDU 20041, a non-heterocystous filamentous marine cyanobacterium was grown in an open tank (∼550L) in ossein effluent using flue gas (coal burnt) after cooling. After 10days with unscrubbed flue gas, the organism’s biomass productivity, specific growth rate, CO2 fixation rate, and lipid content were 30mgL−1d−1, 0.10μd−1, 56.4mgCL−1d−1, and 12.74%, respectively. The predominance of C14 and C18 fatty acids in the total lipid content revealed its suitability as a potential biofuel. Results of this study show that flue gas from a coke oven can be used for mass cultivation of P. valderianum BDU 20041, which efficiently captures CO2 and remediates ossein wastewater. Calcite formation by the organism in effluent was confirmed by scanning electron microscopy and energy dispersion spectroscopy studies. Biomass production employing flue gas coupled with the biomineralization of CO2 in ossein effluent at a point source offers a novel self-sustaining strategy to mitigate CO2 through outdoor cultivation and the subsequent generation of a biodiesel feedstock.

CO2 utilization with a novel dual function material (DFM) for capture and catalytic conversion to synthetic natural gas: An update

Dual function materials (DFMs) for CO2 capture and conversion couple the endothermic CO2 desorption step of a traditional adsorbent with the exothermic hydrogenation of CO2 over a catalyst in a unique way; a single reactor operating at an isothermal temperature (320°C) and pressure (1atm) can capture CO2 from flue gas, and release it as methane upon exposure to renewable hydrogen. This combined CO2 capture and utilization eliminates the energy intensive CO2 desorption step associated with conventional CO2 capture systems as well as avoiding the problem of transporting concentrated CO2 to another site for storage or utilization. Here DFMs containing Rh and dispersed CaO have been developed (>1% Rh 10% CaO/γ-Al2O3) which have improved performance compared to the 5% Ru 10% CaO/γ-Al2O3 DFM (0.50 g-mol CH4/kg DFM) developed previously. Ruthenium remains the catalyst of choice due to its lower price and excellent low temperature performance. The role of CO2 adsorption capacity on the final methanation capacity of the DFM has also been investigated by testing several new sorbents. Two novel DFM compositions are reported here (5% Ru 10% K2CO3/Al2O3 and 5% Ru 10% Na2CO3/Al2O3) both of which have much greater methanation capacities (0.91 and 1.05 g-mol CH4/kg DFM) compared to the previous 5% Ru 10% CaO/γ-Al2O3 DFM.

Investigation of the Different Carbonate Phases and Their Formation Kinetics during Mg(OH)2 Slurry Carbonation

Carbon mineralization is recognized as one of the safest and most permanent methods for storing anthropogenic CO2. Combining CO2 capture and storage eliminates energy-intensive sorbent regeneration and uncertainties associated with geological sequestration of CO2. Carbonation of Mg(OH)2 in a gas–solid system has been investigated, but both the reaction kinetics and the overall conversion were limited. Derived from silicate minerals or industrial wastes, a Mg(OH)2 slurry can react with dissolved CO2 to form a variety of magnesium carbonate phases with differing amounts of hydroxide and crystallized H2O incorporated within the carbonate crystal. In this study, slurry-phase Mg(OH)2 carbonation was investigated at moderate temperatures and CO2 pressures (up to 200 °C and 15 atm). Mg(OH)2 carbonation in the slurry phase involved heterogeneous dissolution of Mg(OH)2 and CO2, in addition to homogeneous precipitation of magnesium carbonates. The reaction conditions responsible for hydrated and anhydrous carbonate...

CO2-selective membranes for hydrogen production and CO2 capture – Part I: Membrane development

Syngas operations require separation of CO2 and hydrogen for hydrogen production at refineries and petrochemical plants, and potentially for combined hydrogen production and CO2 capture at integrated gasification combined cycle (IGCC) power plants. Membranes that selectively permeate CO2 have attracted significant interest, because the purified hydrogen is retained at high pressure, thus avoiding costly downstream recompression. In this work, Polaris™ thin film composite membranes were evaluated for CO2 removal from syngas: these membranes are highly permeable to CO2 and reject the other major components of syngas, including hydrogen, carbon monoxide and methane. Part I of this study describes the three-stage development of Polaris membranes for CO2/H2 separation, including: laboratory parametric tests of membrane stamps using pure- and mixed-gas streams, pilot-scale tests of membrane modules using real syngas at a coal-fired gasification plant, and field demonstration of a membrane system producing liquid CO2. The gasification plant where the field tests were conducted is at the National Carbon Capture Center (NCCC) in Wilsonville, AL. The membrane demonstration system processed 227 kg/h of syngas (equivalent to a 0.15MWe IGCC power plant) containing ~9% CO2, and produced a liquid CO2 stream containing 95+% CO2. Part II of this study will explore the potential opportunities for the use of CO2-selective membranes in commercial hydrogen purification and CO2 capture, including the results of techno-economic analyses for various process designs.

Thermodynamic analysis of a membrane-assisted chemical looping reforming reactor concept for combined H2 production and CO2 capture

There is great consensus that hydrogen will become an important energy carrier in the future. Currently, hydrogen is mainly produced by steam reforming of natural gas/methane on large industrial scale or by electrolysis of water when high-purity hydrogen is needed for small-scale hydrogen plants. Although the conventional steam reforming process is currently the most economical process for hydrogen production, the global energy and carbon efficiency of this process is still relatively low and an improvement of the process is key for further implementation of hydrogen as a fuel source. Different approaches for more efficient hydrogen production with integrated CO2 capture have been discussed in literature: Chemical Looping Combustion (CLC) or Chemical Looping Reforming (CLR) and membrane reactors have been proposed as more efficient alternative reactor concepts relative to the conventional steam reforming process. However, these systems still present some drawbacks. In the present work a novel hybrid reactor concept that combines the CLR technology with a membrane reactor system is presented, discussed and compared with several other novel technologies. Thermodynamic studies for the new reactor concept, referred to as Membrane-Assisted Chemical Looping Reforming (MA-CLR), have been carried out to determine the hydrogen recovery, methane conversion as well as global efficiency under different operating conditions, which is shown to compare quite favorably to other novel technologies for H2 production with CO2 capture.

Effect of H2O on Mg(OH)2 carbonation pathways for combined CO2 capture and storage

Mg-bearing sorbents, derived from silicate minerals and industrial wastes, can act as combined carbon capture and storage media in various energy conversion systems. Mg(OH)2 carbonation in the slurry phase occurs spontaneously and recent results show improved gas–solid carbonation with comparable materials in the presence of H2O vapor; however, the reaction mechanism is still poorly understood at high temperature and pressure conditions. This study investigated the pathways of H2O enhanced Mg(OH)2 carbonation at elevated temperatures and CO2 pressures (up to 673K and 1.52MPa) in the presence of steam and in the slurry phase. For a given reaction temperature, carbonation conversion showed dramatic increase with increasing H2O loading. Comprehensive solid analyses via thermogravimetric analysis, X-ray diffraction, and UV-Raman allowed for qualitative and quantitative compositional characterization of reacted solids. The results suggest that a hydrated environment facilitates the formation of intermediate hydrated magnesium carbonate species. The hydrated carbonates form relatively quickly and can transform into anhydrous carbonates while subjected to greater H2O loading, higher temperature, and/or longer reaction time.

Thermodynamic analysis of combined cycle gas turbine power plant with post-combustion CO2 capture and exhaust gas recirculation

Natural gas is expected to make up a significant proportion of the future global energy mix. Therefore, reducing greenhouse gas emissions from gas-fired processes is very essential for most countries, before emission reduction targets can be met. This article aims to carry out thermodynamic analysis of combined cycle gas turbine power plant with post-combustion CO2 capture through modelling and simulation. The combined cycle gas turbine power plant and the CO2 capture plant were simulated in Aspen Plus®. The combined cycle gas turbine power plant model was validated with simulation data from GateCycle® and the CO2 capture plant model was validated with experimental data from the pilot plant at the University of Texas at Austin. The CO2 capture plant was scaled up from pilot plant to commercial scale to process flue gas from a 250 MWe combined cycle gas turbine power plant. The integrated model for combined cycle gas turbine and CO2 capture plant was further used for performance study. Exhaust gas recirculation has been proposed to increase CO2 concentration in flue gas and reduce the flue gas flow rate. Its effect on combined cycle gas turbine power plant performance and capture plant sizing has been investigated. The analysis indicated that exhaust gas recirculation can reduce penalty on thermal efficiency without any major modification to the original power plant.

Hydrogen Production from Glucose and Sorbitol by Sorption‐Enhanced Steam Reforming: Challenges and Promises

Concerning energy and environmental sustainability, it is appealing to produce hydrogen from sugars or sugar alcohols that are readily obtained from the hydrolysis of cellulosic biomass. Nevertheless, the conversion of such compounds for hydrogen production poses great technical challenges. In this paper, we report that hydrogen purity and yield can be significantly improved by integrating in situ CO(2) capture into the steam reforming reaction of the model compounds-glucose and sorbitol. The experimental assessment was conducted at a steam-to-carbon ratio of 1.8 for sorbitol and 6 for glucose from 450-625 °C. As predicted by thermodynamic analysis, combining CO(2) capture and reforming reactions at favorable operating conditions yielded very high purity hydrogen, for instance, 98.8 mol % from sorbitol and 99.9 mol % from glucose. However, there are trade-offs between hydrogen purity and yield in practice. The lower operating temperatures in the examined range helped to increase the hydrogen purity and reduce the CO content in the gas product, whereas a high hydrogen yield was more likely to be obtained at higher temperatures. Coupling CO(2) capture lowered the risk of coke formation during the steam reforming of glucose. Coke accumulated in the reactor for the sorption-enhanced steam reforming of glucose was mostly from the slow pyrolysis of glucose before it came into contact with the catalyst-acceptor bed. This problem may be solved by improving heat transfer or reconstructing the reactor, for instance, by using a fluidized-bed reactor.

Energy conversion performance of black liquor gasification to hydrogen production using direct causticization with CO2 capture

This paper estimates potential hydrogen production via dry black liquor gasification system with direct causticization integrated with a reference pulp mill. The advantage of using direct causticization is elimination of energy intensive lime kiln. Pressure swing adsorption is integrated in the carbon capture process for hydrogen upgrading. The energy conversion performance of the integrated system is compared with other bio-fuel alternatives and evaluated based on system performance indicators. The results indicated a significant hydrogen production potential (about 141MW) with an energy ratio of about 0.74 from the reference black liquor capacity (about 243.5MW) and extra biomass import (about 50MW) to compensate total energy deficit. About 867,000tonnes of CO2 abatement per year is estimated i.e. combining CO2 capture and CO2 offset from hydrogen replacing motor gasoline. The hydrogen production offers a substantial motor fuel replacement especially in regions with large pulp and paper industry e.g. about 63% of domestic gasoline replacement in Sweden.

Efficient energy systems with CO2 capture and storage from renewable biomass in pulp and paper mills

This paper investigates the impact of combining CO2 capture and storage with alternative systems for biomass-based combined heat and power production (CHP) in Kraft pulp and paper mills. We compare heat, power, and CO2 balances of systems with alternative configurations of the CHP and CO2-capture systems. Because the captured CO2 comes from renewable biomass, the studied systems yield negative CO2 emissions. It is shown that pulp mills and integrated pulp and paper mills have the potential to become net exporters of biomass-based electricity while at the same time removing CO2 from the atmosphere on a net basis. The study shows that that the overall best CO2 abatement is achieved when CO2 capture is carried out within a biomass integrated gasifier with combined cycle where the syngas undergoes a CO-shift reaction. This configuration combines efficient energy conversion with a high CO2 capture efficiency. Furthermore, cost curves are constructed, which show how the cost of CO2 capture and storage in pulp and paper mills depends on system configuration and the CO2 transportation distance.