High Purity CO2 Research Articles

Molecular-scale investigation of the oxidation behavior of chromia-forming alloys in high-temperature CO2

Current and future power systems require chromia-forming alloys compatible with high-temperature CO2. Important questions concerning the mechanisms of oxidation and carburization remain unanswered. Herein we shed light onto these processes by studying the very initial stages of oxidation of Fe22Cr and Fe22Ni22Cr model alloys. Ambient-pressure X-ray photoelectron spectroscopy enabled in situ analysis of the oxidizing surface under 1 mbar of flowing CO2 at temperatures up to 530 °C, while postexposure analyses revealed the structure and composition of the oxidized surface at the near-atomic scale. We found that gas purity played a critical role in the kinetics of the reaction, where high purity CO2 promoted the deposition of carbon and the selective oxidation of Cr. In contrast, no carbon deposition occurred in low purity CO2 and Fe oxidation ensued, thus highlighting the critical role of impurities in defining the early oxidation pathway of the alloy. The Cr-rich oxide formed on Fe22Cr in high purity CO2 was both thicker and more permeable to carbon compared to that formed on Fe22Ni22Cr, where carbon transport appeared to occur by atomic diffusion through the oxide. Alternatively, the Fe-rich oxide formed in low purity CO2 suggested carbon transport by molecular CO2.

Utilizing high-purity carbon dioxide sources for algae cultivation and biofuel production in the United States: Opportunities and challenges

Carbon dioxide (CO2) supply is an important consideration for algae production systems, and using high-purity CO2 eliminates the need for purification processes. This study assessed the challenges and opportunities inherent in using waste high-purity CO2 to produce algae in the United States. The United States’ upper Midwest region is rich in high-purity CO2 from corn ethanol production. However, its climate is not as favorable for algae production as that on the Gulf Coast. This study assessed the tradeoffs between these factors by comparing algae biofuel production with and without high-purity CO2 across these two regions. Monthly algae cultivation was modeled in open ponds co-located with high-purity CO2 sources in the Midwest and along the Gulf Coast, where many steam methane reforming and ammonia production facilities are located. This revealed that, by avoiding the energy-intensive carbon-capture process, an algae site that sources carbon from a high-purity CO2 source would achieve a 9–39% reduction in life-cycle greenhouse gas (GHG) emissions and a 9–37% reduction in life-cycle fossil energy use compared to a similar site using dilute CO2 for algae cultivation. The results also suggest that during warm months an algae pond in the Midwest would achieve results that are comparable to GHG emissions from a pond on the Gulf Coast. Furthermore, several Midwest algae ponds investigated in this study create less local water stress than those located along the Gulf Coast. The abundant high-purity CO2 from corn ethanol plants thus creates a potential opportunity for algae cultivation in the Midwest. This study illustrated the interplay between algae productivity, CO2 delivery, GHG emissions, and water stress in siting algae ponds.

Hybrid-energy approach enabled by heat storage and oxy-combustion to generate electricity with near-zero or negative CO2 emissions

We assess a hybrid-energy approach that modifies a steam-turbine power plant to use renewable energy sources (electricity, plus options for geothermal and solar heat), plus fossil fuel (natural gas and coal) and/or waste biomass (e.g., Douglas fir woodchips). Heat storage allows heat to be created during periods of excess energy supply and for that heat to be converted to electricity when demanded. Excess electricity, such as from variable renewable energy (VRE), is used to generate oxygen for oxy-combustion furnaces that create very-hot, high-purity CO2 that heats granular rock beds in insulated vessels. Cool CO2 leaving the beds is dried, sent to compressors powered by excess VRE electricity, before being sent by pipeline to geologic CO2 storage. Very-hot CO2 transfers high-grade heat from storage to the power plant in a closed loop that returns medium-grade heat back to storage, allowing low- and medium-grade renewable-heat sources to be stacked beneath combustion heat, with all heat sources being converted to electricity at the same (high) thermal efficiency. Reliable, on-demand power may be generated with near-zero CO2 emissions with fossil fuel and with negative CO2 emissions with waste biomass. Our analyses show that with fossil fuel, up to 35% of gross power can be derived from renewable sources, while for waste biomass, it can be entirely derived from renewable sources. Because our approach has the potential to ensure that grids have a continuous supply of clean energy and because electricity is only generated once, when demanded, it could serve as an efficient alternative to bulk energy storage.

Influence of NaCl Additive on the Reduction Process of MoO3 to Mo2C by High-Purity CO Gas

Influence of NaCl Additive on the Reduction Process of MoO3 to Mo2C by High-Purity CO Gas

Environmental Performance of Alternative Green Polyol Synthesis Routes: A Proposal for Improvement

This study verified the environmental effectiveness of potentially less aggressive routes for the synthesis of poly(propylene/ethylene oxide) glycol (PPG). The analysis was developed in two stages. Firstly, the environmental performance of the conventional PPG processing route was compared to alternative variants—vegetal PPG and CO2-based PPG—applying the life cycle assessment technique to measure the primary energy demand, global warming potential, acidification, photochemical oxidation, and freshwater ecotoxicity impact categories. The synthesis of vegetable polyols from bio-based assets, such as vegetable oils, and the application of CO2 conversion routes as an alternative to technologies supported by petroleum and natural gas were studied. The use of CO2 recovered through carbon capture and usage practices resulted in environmental gains for PPG production. The processing routes within vegetal assets were not an environmentally attractive option as the performance was worse than the conventional arrangement by 144% for the global warming impact category, an increase related to the deforestation carried out to expand soybean cultivation in Brazil. Secondly, improvement scenarios to mitigate the environmental impacts of alternative routes were performed. The hypothesis of using cleaner inputs to obtain a more ecofriendly route was tested. The analysis concluded that the use of high-purity CO2 brings fewer benefits compared to other capturing sources that need a purification process before feeding the PPG synthesis.

Carbon capture in ultra-high performance concrete using pressurized CO2 curing

This study demonstrates a novel means of carbon capture and storage (CCS) in ultra-high performance concrete (UHPC) to reduce its carbon footprint. A two-pronged approach of developing eco-friendly UHPC was employed by 1) replacing cement in the mix with ground granulated blast furnace slag (GGBS) and 2) capturing CO2 in fresh UHPC mixes. The replacement levels of cement with GGBS were 30, 50 and 70% by weight. Samples were cured in fresh state inside a pressurized chamber using high purity CO2 for the first 16 h. The curing pressure in the chamber was maintained constant at 3 bars for the entire duration of curing. A replicate batch was allowed to cure at room temperature under ambient conditions. The ambient and carbonated samples were investigated for compressive strength, phase composition using thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD). Hydration kinetics under normal conditions were monitored using isothermal calorimetry (ITC). The CO2 uptake by the samples was determined from TGA results. Carbon curing resulted in a slight decrease in the compressive strength of the UHPC mixes but substantially improved the degree of carbonation (DOC) of the mixes. Replacement of cement with GGBS further increase the DOC values. Carbon uptake was highest (80 kg CO2 per m3 of UHPC) when using 30% by wt. GGBS, but decreased with higher GGBS content. The findings of this study are envisaged to provide a new approach towards CCS and generate further interests in developing ‘greener’ version of UHPCs.

Automated Programmable Generation of Broad pH Range Volatile Ionic Eluents for Liquid Chromatography.

Many of the universal detectors in liquid chromatography, including mass spectrometry, must completely volatilize the chromatographic eluent first before further processing and detection of the analytes. A basic requirement is that the eluent does not contain a nonvolatile dissolved component. However, separation of biomolecules must be conducted in mostly aqueous media of compatible pH and ionic strength if their biological activity must survive the separation process. Combinations of ammonia with acetic and formic acids are commonly used as eluent for this purpose but generally maximum concentrations that can be tolerated are relatively low. Further, buffering is good only over a limited pH range. We describe a system where the eluent is generated in an automated pressure-programmed manner from high-purity gaseous NH3 and CO2 through gas-permeable membrane devices. This can be aided by the prior presence of formic/acetic acids in the mobile phase to extend the attainable low pH limit. We outline the fundamental pH, ionic strength, and buffer intensity considerations and demonstrate the application of such eluents in the separation of amino acids, proteins, and monoclonal antibodies. We also demonstrate the use of dissolved CO2 as an ion-pairing agent in the separation of chiral amines.

Technoeconomic and Life Cycle Analysis of Synthetic Methanol Production from Hydrogen and Industrial Byproduct CO2.

CO2 capture and utilization provides an alternative pathway for low-carbon hydrocarbon production. Given the ample supply of high-purity CO2 emitted from ethanol and ammonia plants, this study conducted technoeconomic analysis and environmental life cycle analysis of several systems: integrated methanol-ethanol coproduction, integrated methanol-ammonia coproduction, and stand-alone methanol production systems, using CO2 feedstock from ethanol plants, ammonia plants, and general market CO2 supply. The cradle-to-grave greenhouse gas emissions of methanol produced from the stand-alone methanol, integrated methanol-ethanol, and integrated methanol-ammonia systems are 13.6, 37.9, and 84.6 g CO2-equiv/MJ, respectively, compared to 91.5 g CO2-equiv/MJ of conventional methanol produced from natural gas. The minimum fuel selling price (MFSP) of methanol ($0.61-0.64/kg) is 61-68% higher than the average market methanol price of $0.38/kg, when using a Department of Energy target renewable hydrogen production price of $2.0/kg. The methanol price increases to $1.24-1.28/kg when the hydrogen price is $5.0/kg. Without CO2 abatement credits, the H2 price needs to be within $0.77-0.95/kg for the MFSP of methanol to equal the average methanol market price. With a CO2 credit of $35/MT according to tax credit per metric ton of CO2 captured and used, the methanol price is reduced to $0.56-0.59/kg.

Study of Amine Functionalized Mesoporous Carbon as CO2 Storage Materials

Carbon sequestration via the carbon capture and storage (CCS) method is one of the most useful methods of lowering CO2 emissions in the atmosphere. Ethylenediamine (EDA)- and triethylenetetramine (TETA)-modified mesoporous carbon (MC) has been successfully prepared as a CO2 storage material. The effect of various concentrations of EDA or TETA added to MC, as well as activated carbon (AC), on their CO2 adsorption capacity were investigated using high-purity CO2 as a feed and a titration method to quantitatively measure the amount of adsorbed CO2. The results showed that within 60 min adsorption time, MCEDA49 gave the highest CO2 capacity adsorption (19.68 mmol/g), followed by MC-TETA30 (11.241 mol/g). The improvement of CO2 adsorption capacity at low TETA loadings proved that the four amine functional groups in TETA gave an advantage to CO2 adsorption. TETA-functionalized MC has the potential to be used as a CO2 storage material at a low concentration. Therefore, it is relatively benign and friendly to the environment.

Thermodynamic analysis of syngas production from biodiesel via chemical looping reforming

In this study, thermodynamic analysis of the syngas production using biodiesel derived from waste cooking oil is studied based on the chemical looping reforming (CLR) process. The NiO is used as the oxygen carrier to carry out the thermodynamic analysis. Syngas with various H2/CO ratios can be obtained by chemical looping dry reforming (CL-DR) or steam reforming (CL-SR). It is found that the syngas obtained from CL-DR is suitable for long-chain carbon fuel synthesis while syngas obtained from CL-SR is suitable for methanol synthesis. The carbon-free syngas production can be obtained when reforming temperature is higher than 700 °C for all processes. To convert the carbon resulted from biodiesel coking and operate the CLR with a lower oxygen carrier flow rate, a carbon reactor is introduced between the air and fuel reactors for removing the carbon using H2O or CO2 as the oxidizing agent. Because of the endothermic nature of both Boudouard and water-gas reactions, the carbon conversion in the carbon reactor increases with increased reaction temperature. High purity H2 or CO yield can be obtained when the carbon reactor is operated with high reaction temperature and oxidizing agent flow.

A Pilot Plant in Dunkirk for DMX Process Demonstration

The DMX process is a second-generation CO2 capture process using a phase change solvent. The development of this process including lab scale and minipilot experimentation has been carried out by IFPEN within different projects such as OCTAVIUS & VALORCO. These studies highlighted the main advantages of the DMX process : high cyclic solvent capacity (from 0.1 to 1 mol CO2/mol solvent), low heat required for regeneration (less than 2.3 GJ/tCO2 for 90 % capture rate), high CO2 purity, no degradation of the solvent (up to 160°C) allowing to carry out the regeneration step at higher temperature and pressure, producing CO2 at higher pressure (up to 6-7 bara), no corrosion of the solvent allowing the use of Carbon Steel material for the construction of the future industrial units. First techno-economic evaluations have shown an OPEX reduction and a CO2 capture cost reduction up to 30 % compared to the first-generation processes using amine-based solvents. DMX process is very promising but it needs now to be demonstrated in an industrial scale pilot plant in order to increase its TRL from 4 to 7. This demonstration, which is the last step before the commercialisation of this process by AXENS, will be carried within the 3D (DMX Demonstration in Dunkirk) project on an industrial pilot plant to be built at the ArcelorMittal steel mill in Dunkirk (France) In this paper, are presented the design of the industrial pilot plant; first experimentation plan is also presented and explained. Planning of the demonstration and expected commercialisation will be discussed.

Tunable Syngas Production from Biomass: Synergistic Effect of Steam, Ni-Cao Catalyst, and Biochar

The acquisition of tunable syngas through the inherently separated generation of high purity H2 and CO from biomass will further establish the role of biomass-derived syngas as a versatile platform for liquid fuels and value-added chemical synthesis. The influence of steam, Ni-CaO catalyst, and biochar on the tunable syngas generated from sewage sludge via a two-stage sorption-enhanced (TSSE) thermochemical conversion process was studied in this study. The presence of steam and Ni-CaO catalyst shows unprecedented performance in enhancing the H2 generation at the first stage, and the control experiments indicate that the steam performs a higher selectivity to H2 than the Ni-CaO catalyst. The introduction of biochar supplements carbon source for CO production, remarkably promoting the CO generation at the second stage, which could be further pronounced by the addition of Ni-CaO catalyst. A synergistic effect of steam, Ni-CaO catalyst, and biochar contributes to a significant enhancement in H2 and CO generation with an inherently separated generation of H2 (88.2 vol% of purity) and CO (55.6 vol% of purity). And the combined use of steam, Ni-CaO catalyst, and biochar could lead to a superior syngas quality with high LHVsyngas and energy recovery efficiency.

Negative Emissions in the Chemical Sector: Lifecycle Co₂ Accounting for Biomass and CCS Integration into Ethanol, Ammonia, Urea, and Hydrogen Production

The chemical sector is hydrocarbon intensive, using primarily fossil fuels as both fuel and feedstock. To achieve carbon-neutrality, it is likely that negative CO₂ emissions will be needed to offset the carbon embodied in chemical products. This study presents first-order estimates of the decarbonization potential of combining bioenergy and biofeedstock use with carbon capture and storage (bio-CCS) for ethanol, ammonia, urea, and hydrogen. For each, net CO₂ of emissions minus atmospheric removals was estimated over the whole life cycle including chemical synthesis, upstream supply chains, product use, and waste disposal. With aggressive bio-CCS using technologies that are currently commercially available, CO₂ negative production was estimated to be possible for all chemicals modelled, except urea. With the use of biomass for both feedstock and fuel and capture of both high-purity and dilute CO₂ streams, the estimated net CO₂ was -30 g/MJ for maize bioethanol; -50 g/MJ for stover bioethanol; -50 g/MJ for merchant hydrogen; -1.2 t/t N for ammonia and 0.2 t/t N for urea. The potential for negative CO₂ emissions is higher in cases where more CO₂ can be captured during chemical production. However, all cases were sensitive to assumptions regarding the specific configuration and upstream supply chains.

Initial operation of a continuous lab-scale MBTSA pilot using activated carbon adsorbent

A lab-scale moving-bed temperature-swing adsorption (MBTSA) pilot has been designed and constructed. The pilot has primarily been designed for the evaluation of various adsorbent materials at realistic conditions where gas composition and steam content of the inlet gas can be varied. The desorption compartment consists of a modular heat exchanger where a hot fluid is used to heat the adsorbent indirectly. Initial experiments using a commercial activated carbon adsorbent show that capture rates above 95% can easily be achieved. However, obtaining high CO2 purity of the gas released from the regenerator will need proper balancing of the under-pressure used to pull out the CO2. In addition, properly balanced recycling of N2 rich gas entering at the top of the regenerator and CO2 rich gas from the top of the cooling section back to the adsorber inlet will be important

Prediction of sorption enhanced steam methane reforming products from machine learning based soft-sensor models

Carbon dioxide-abated hydrogen can be synthesised via various processes, one of which is sorption enhanced steam methane reforming (SE-SMR), which produces separated streams of high purity H2 and CO2. Properties of hydrogen and the sorbent material hinder the ability to rapidly upscale SE-SMR, therefore the use of artificial intelligence models is useful in order to assist scale up. Advantages of a data driven soft-sensor model over thermodynamic simulations, is the ability to obtain real time information dependent on actual process conditions. In this study, two soft sensor models have been developed and used to predict and estimate variables that would otherwise be difficult direct measured. Both artificial neural networks and the random forest models were developed as soft sensor prediction models. They were shown to provide good predictions for gas concentrations in the reformer and regenerator reactors of the SE-SMR process using temperature, pressure, steam to carbon ratio and sorbent to carbon ratio as input process features. Both models were very accurate with high R2 values, all above 98%. However, the random forest model was more precise in the predictions, with consistently higher R2 values and lower mean absolute error (0.002-0.014) compared to the neural network model (0.005-0.024).

High-temperature oxidation of transient-liquid phase bonded Ni-based alloys in 1 bar and 250 bar carbon dioxide

ABSTRACT Compact microchannel heat exchanger designs for supercritical CO2 power cycles are valued for equipment size reduction and increased heat transfer. They can be fabricated via transient-liquid phase (TLP) bonding, which utilises a lower melting point interlayer for bonding facilitation of etched thin plates. Haynes 230 and 282 TLP bonded stacks were exposed to high-purity CO2 at 1 bar/700 °C to 4000 h and 250 bar/720 °C (supercritical) to 1500 h. All samples obeyed parabolic kinetics after an oxide build-up stage of 500–1000 h. Mass gains were similar for the base and TLP bonded alloys, and oxide thicknesses and scales did not significantly differ around the TLP bond regions. There were some slight oxide compositional differences for the H282 TLP samples at 250 bar. There was a slight pressure effect on mass gain, as samples exposed at the higher pressure experienced higher initial mass gains, but then slower continued oxide growth.

CO2 Desorption Performance from Imidazolium Ionic Liquids by Membrane Vacuum Regeneration Technology.

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity CO2 is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO2 solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption–desorption process. CO2 absorption–desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310 K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry’s constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works.

High-performance composite cathode for electrolysis of CO2 in tubular solid oxide electrolysis cells: A pathway for efficient CO2 utilization

High temperature solid oxide electrolysis cells (SOECs) have a tremendous potential to provide a practical pathway for onsite on demand production of high purity CO by recycling waste CO2 at industry relevant production scale. CO is an important feedstock for production of numerous chemicals required for the pharmaceutical, food and plastics industry. Recently, SOECs are also being developed to produce renewable fuels and energy carriers to allow transport and storage of renewable energy. Despite promising pre-commercial demonstrations, some key technical challenges need to be addressed to make this technology economically feasible. These include lowering capital costs with low cost materials and cell designs, and improvements in the electrode performance and lifetime, the cathode. The conventional Nickel-YSZ cathode is found to be promising in terms of performance during initial operation; however, a continuous supply of valuable reducing gas is needed to prevent oxidation of Ni to NiO, and accelerated degradation has been observed due to Ni migration and deactivation. In the present study we have evaluated the performance of A-site deficient doped lanthanum ferrites ((La0.60Sr0.40)0.95Co0.20Fe0.80O3-x) - Gd0.20Ce0.80O1.95) dual phase mixed ionic and electronic conducting cathode for CO2 electrolysis in a symmetrical tubular cell without the addition of reductant or protective gas during the cell operation. A polarization resistance as low as 0.36 ohm-cm2 was observed at 1.2 V after 350 h of CO2 electrolysis at 800 °C. The electrochemical performance of the electrode is also compared with state-of-the-art Ni-YSZ cathode using similar cells and experimental conditions.

Two-stage VSA/PSA for capturing carbon dioxide (CO2) and producing hydrogen (H2) from steam-methane reforming gas

A two-stage vacuum/pressure swing adsorption (VSA/PSA) process has been investigated for CO2 capture and then H2 production from steam methane reforming (SMR) gas mixture. The target is to produce ultra-pure hydrogen and high-purity CO2. Many fundamental research studies have been carried out to validate the accuracy of numerical calculation, such as isotherm measurement, fitting and process modelling. The results indicate that the first stage process could produce 95.31% CO2 with the recovery of 90.93% and the second stage could produce 99.9952% H2 with an overall recovery of 71.16%. Variable analysis, optimal conditions and comparison with other processes are discussed in detail.

Ambient weathering of magnesium oxide for CO2 removal from air

To avoid dangerous climate change, new technologies must remove billions of tonnes of CO2 from the atmosphere every year by mid-century. Here we detail a land-based enhanced weathering cycle utilizing magnesite (MgCO3) feedstock to repeatedly capture CO2 from the atmosphere. In this process, MgCO3 is calcined, producing caustic magnesia (MgO) and high-purity CO2. This MgO is spread over land to carbonate for a year by reacting with atmospheric CO2. The carbonate minerals are then recollected and re-calcined. The reproduced MgO is spread over land to carbonate again. We show this process could cost approximately $46–159 tCO2−1 net removed from the atmosphere, considering grid and solar electricity without post-processing costs. This technology may achieve lower costs than projections for more extensively engineered Direct Air Capture methods. It has the scalable potential to remove at least 2–3 GtCO2 year−1, and may make a meaningful contribution to mitigating climate change.