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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Direct Air Capture of CO 2 with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)

We report a bench-scale direct air capture (DAC) process comprising CO 2 absorption with aqueous amino acid salts (i.e., potassium glycinate, potassium sarcosinate), followed by room-temperature regeneration of the amino acids by reaction with solid meta-benzene-bis(iminoguanidine) (m-BBIG), resulting in crystallization of the hydrated m-BBIG carbonate salt, (m-BBIGH 2 )(CO 3 )(H 2 O) n (n = 3–4). The CO 2 is subsequently released by mild heating (60–120 °C) of the carbonate crystals, which regenerates the m-BBIG solid quantitatively. This low-temperature crystallization-based DAC process circumvents the need to heat the aqueous amino acid sorbents, thereby minimizing their loss through thermal and oxidative degradation. The CO 2 cyclic capacity for the sarcosine/m-BBIG system, measured over three consecutive absorption/regeneration cycles, is in the range of 0.12–0.20 mol/mol. The regeneration energy of m-BBIG, comprising the enthalpy of CO 2 and water release, and the sensible heat, is 360 kJ/mol (8.2 GJ/ton CO 2 ). Alternatively, the aqueous amino acids can be regenerated by boiling under reflux, with measured cyclic capacities of up to 0.64 mol/mol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Simulating a Mesoscale Convective System Using WRF with a New Spectral Bin Microphysics: Part 1: Hail vs Graupel

A modified Fast Spectral Bin Microphysics scheme (FSBM-2) embedded into the Weather Research and Forecasting Model (WRF) is used to simulate a mesoscale deep convective system observed during the Midlatitude Continental Convective Clouds Experiment (MC3E). FSBM-2 uses modified source codes as compared to the current FSBM (FSBM-1). In contrast to FSBM-1, FSBM-2 can simulate hail of several cm in diameter and includes additional processes such as spontaneous breakup of raindrops and aerosol regeneration by drop evaporation. It is shown that allowing large hail particles of diameters exceeding about 1 cm substantially increases the agreement between the simulated and observed squall-line structures both in the convective and stratiform regions. In contrast, if graupel particles are used to represent high-density hydrometeors in convective areas, the ratio of convective-to-stratiform areas diverges from the ratio seen in observations and maximum radar reflectivities are substantially underestimated. Analysis of snow size distributions in the stratiform area shows an important link between the ice crystals formed by homogeneous freezing in the convective area to ice particle number concentration in the stratiform region. Simulated raindrop size distributions in the stratiform area below the melting level from FSBM-2 show a good agreement with observations. The regeneration of CCN by droplet evaporation and detrainment of these CCN to the stratiform region increases the concentration of CCN there up to 8-9 km altitude; the additional CCN penetrate clouds and produce new droplets, leading to some convection intensification. Key words: Mesoscale convective systems (MCS), squall lines, spectral bin microphysics, large hail, in-cloud nucleation, size distributions of hydrometeors in MCS.

Shpund, Kobby↗
DOE OSTI2010

Solar chameleons

We analyze the creation of chameleons deep inside the Sun (R{approx}0.7R{sub sun}) and their subsequent conversion to photons near the magnetized surface of the Sun. We find that the spectrum of the regenerated photons lies in the soft x-ray region, hence addressing the solar corona problem. Moreover, these back-converted photons originating from chameleons have an intrinsic difference with regenerated photons from axions: their relative polarizations are mutually orthogonal before Compton interacting with the surrounding plasma. Depending on the photon-chameleon coupling and working in the strong coupling regime of the chameleons to matter, we find that the induced photon flux, when regenerated resonantly with the surrounding plasma, coincides with the solar flux within the soft x-ray energy range. Moreover, using the soft x-ray solar flux as a prior, we find that with a strong enough photon-chameleon coupling, the chameleons emitted by the Sun could lead to a regenerated photon flux in the CAST magnetic pipes, which could be within the reach of CAST with upgraded detector performance. Then, axion helioscopes have thus the potential to detect and identify particle candidates for the ubiquitous dark energy in the Universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

LeTID-Affected Cells from a Utility-Scale Photovoltaic System Characterized by Deep Level Transient Spectroscopy

Photovoltaic modules from a utility-scale field experienced power loss by light- and elevated temperature-induced degradation (LeTID). Samples of one of the affected monocrystalline silicon cells were cored and extracted from the module packaging and encapsulation. One of the cell fragments was processed using a regeneration cycle of applying short-circuit-rated current in forward bias at 85 degrees C for 2 weeks, while the other fragment was kept in its outdoor-degraded LeTID state. Both samples were scribed to form 2-mm diameter isolated areas using a femtosecond-pulse-width laser micromachining system. Both isolated areas contained front grid line segments which were wire bonded to larger contact pads, and the samples were probed in a cryostat linked to a deep-level transient spectroscopy (DLTS) system. Using DLTS, a majority-carrier, hole-trap defect was detected on each sample with an activation energy of 0.42 eV. The LeTID-degraded sample, however, had a larger signal corresponding to a trap density of 1.1x10^13 cm-3, which was about five times larger than the 2.1x10^12 cm-3 trap density of the regenerated sample.

charge carrier lifetime↗
DOE OSTI2020

Performance of a CO 2 sorbent for indoor air cleaning applications: Effects of environmental conditions, sorbent aging, and adsorption of co-occurring formaldehyde

Indoor air cleaning systems that incorporate CO 2 sorbent materials enable HVAC load shifting and efficiency improvements. This study developed a bench-scale experimental system to evaluate the performance of a sorbent under controlled operation conditions. A thermostatic holder containing 3.15 g sorbent was connected to a manifold that delivered CO 2 -enriched air at a known temperature and relative humidity (RH). The air stream was also enriched with 0.8-2.1 ppm formaldehyde. The CO 2 concentration was monitored in real-time upstream and downstream of the sorbent, and integrated formaldehyde samples were collected at different times using DNPH-coated silica cartridges. Sorbent regeneration was carried out by circulating clean air in countercurrent. Almost 200 loading/regeneration cycles were performed in the span of 17 months, from which 104 were carried out at reference test conditions defined by loading with air at 25°C, 38% RH, and 1000 ppm CO 2 , and regenerating with air at 80°C, 3% RH and 400 ppm CO 2 . The working capacity decreased slightly from 43-44 mg CO 2 per g sorbent to 39-40 mg per g over the 17 months. The capacity increased with lower loading temperature (in the range 15-35°C) and higher regeneration temperature, between 40 and 80°C. The CO 2 capacity was not sensitive to the moisture content in the range 6-9 g/m 3 , and decreased slightly when dry air was used. Loading isothermal breakthrough curves were fitted to three simple adsorption models, verifying that pseudo-first-order kinetics appropriately describes the adsorption process. The model predicted that equilibrium capacities decreased with increasing temperature from 15 to 35°C, while adsorption rate constants slightly increased. The formaldehyde adsorption efficiency was 80%-99% in different cycles, corresponding to an average capacity of 86 ± 36 µg/g. Formaldehyde was not quantitatively released during regeneration, but its accumulation on the sorbent did not affect CO 2 adsorption.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Middleware for a Heterogeneous CAV Fleet

This paper introduces CAN to ROS, a model-based code generation tool used in development, testing, and deployment of a heterogeneous fleet of vehicles with robotic sensing in ROS. Code generation supports two main features: (1) self-configuration for deployment in a heterogeneous vehicle fleet, and (2) quick iteration for testing and development of reading vehicle sensors and robotic control. This tool features the ability to detect the vehicle it is in and regenerate and rebuild itself at runtime to provide the proper two-way bridge between ROS and the sensed on-board vehicle sensor network. Code generation relies on a per-model defined JSON to map a CAN database (DBC) to the desired ROS topic names and message types. The live ROS publishing of CAN messages allows for instant feedback, and the code regeneration allows for adjustments in DBC or vehicle JSON to iteratively hone in on new vehicle signals. Generated ROS nodes are written in C++ for runtime use in lightweight embedded computers. This has been tested in vehicles from three different Original Equipment Manufacturers (OEMs), and can be extended to support a wide array of vehicles. By using a unifying ROS specification, a heterogeneous set of vehicles can be unified into a fleet with abstracted model-specific details; this opens the door for developing cross-model software applications for vehicle control, connected vehicle applications, or fleet monitoring systems.

42 ENGINEERING↗
DOE OSTI2026

Data for Rewiring Yeast Metabolism for Producing 2,3-Butanediol and Two Downstream Applications: Techno-Economic Analysis and Life Cycle Assessment of Methyl Ethyl Ketone (MEK) and Agricultural Biostimulant Production

Rising concerns for sustainability and global climate change have driven the development of sustainable production pathways for biofuels and chemicals from lignocellulosic biomass via integrated biological and chemical processes. We constructed an engineered Saccharomyces cerevisiae capable of producing 2,3-butanediol (2,3-BDO) from glucose without accumulating ethanol and glycerol, which hinder downstream processing of 2,3-BDO, through extensive metabolic reprogramming. Specifically, we introduced heterologous 2,3-BDO biosynthetic enzymes and deleted the major isozymes of ethanol and glycerol biosynthetic enzymes. In addition, we introduced an NAD+ regenerating Pyruvate-Malate (PM) cycle and enhanced the NAD+ regenerating capability of the PM cycle to resolve the redox imbalance from the deletion of ethanol and glycerol production pathways. The resulting engineered yeast produced 109.9 g/L of 2,3-BDO with a productivity of 1.0 g/L/h and a yield of 0.36 g/g glucose in a fed-batch fermentation. We also conducted techno-economic analysis (TEA) and life cycle assessment (LCA) of the production of methyl ethyl ketone (MEK) through catalytic dehydration of 2,3-BDO. A TEA based on the experimental results indicated that the minimum product selling price (MPSP) was estimated to be $1.90/kg. Regarding cradle-to-grave LCA, 100-year global warming potential (GWP100) and fossil energy consumption (FEC) were found to be 0.37 kg CO2 eq/kg and 3.1 MJ/kg, respectively. These results demonstrated the feasibility of cost-competitive and sustainable bio-based MEK production via yeast fermentation. In addition, we explored the possibility of using the fermentation broth containing 2,3-BDO as a biostimulant inducing drought tolerance in plants. As a result, the yeast 2,3-BDO fermentation broth can induce drought tolerance in Arabidopsis thaliana without a complicated purification process.

Economics↗
DOE OSTI2014

Final Scientific/Technical Report for DOE/EERE project Advanced Magnetic Refrigerant Materials

A team led by GE Global Research developed new magnetic refrigerant materials needed to enhance the commercialization potential of residential appliances such as refrigerators and air conditioners based on the magnetocaloric effect (a nonvapor compression cooling cycle). The new magnetic refrigerant materials have potentially better performance at lower cost than existing materials, increasing technology readiness level. The performance target of the new magnetocaloric material was to reduce the magnetic field needed to achieve 4 °C adiabatic temperature change (ΔT adiabatic ) from 1.5 Tesla to 0.75 Tesla. Such a reduction in field minimizes the cost of the magnet assembly needed for a magnetic refrigerator. Such a reduction in magnet assembly cost is crucial to achieving commercialization of magnetic refrigerator technology. This project was organized as an iterative alloy development effort with a parallel material modeling task being performed at George Washington University. Four families of novel magnetocaloric alloys were identified, screened, and assessed for their performance potential in a magnetic refrigeration cycle. Compositions from three of the alloy families were manufactured into regenerator components. At the beginning of the project a previously studied magnetocaloric alloy was selected for manufacturing into the first regenerator component. Each of the regenerators was tested in magnetic refrigerator prototypes at a subcontractor at at GE Appliances. The property targets for operating temperature range, operating temperature control, magnetic field sensitivity, and corrosion resistance were met. The targets for adiabatic temperature change (ΔT adiabatic ) and thermal hysteresis were not met. The high thermal hysteresis also prevented the regenerator components from displaying measurable cooling power when tested in prototype magnetic refrigerators. Magnetic refrigerant alloy compositions that were predicted to have low hysteresis were not attainable with conventional alloy processing methods. Preliminary experiments with rapid solidification methods showed a path towards attaining low hysteresis compositions should this alloy development effort be continued.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Evaluation of Solid Sorbents as a Retrofit Technology for CO 2 Capture

ADA completed a DOE-sponsored program titled Evaluation of Solid Sorbents as a Retrofit Technology for CO 2 Capture under program DE-FE0004343. During this program, sorbents were analyzed for use in a post-combustion CO 2 capture process. A supported amine sorbent was selected based upon superior performance to adsorb a greater amount of CO 2 than the activated carbon sorbents tested. When the most ideal sorbent at the time was selected, it was characterized and used to create a preliminary techno-economic analysis (TEA). A preliminary 550 MW coal-fired power plant using Illinois #6 bituminous coal was designed with a solid sorbent CO 2 capture system using the selected supported amine sorbent to both facilitate the TEA and to create the necessary framework to scale down the design to a 1 MWe equivalent slipstream pilot facility. The preliminary techno-economic analysis showed promising results and potential for improved performance for CO 2 capture compared to conventional MEA systems. As a result, a 1 MWe equivalent solid sorbent system was designed, constructed, and then installed at a coal-fired power plant in Alabama. The pilot was designed to capture 90% of the CO 2 from the incoming flue gas at 1 MWe net electrical generating equivalent. Testing was not possible at the design conditions due to changes in sorbent handling characteristics at post-regenerator temperatures that were not properly incorporated into the pilot design. Thus, severe pluggage occurred at nominally 60% of the design sorbent circulation rate with heated sorbent, although no handling issues were noted when the system was operated prior to bringing the regenerator to operating temperature. Testing within the constraints of the pilot plant resulted in 90% capture of the incoming CO 2 at a flow rate equivalent of 0.2 to 0.25 MWe net electrical generating equivalent. The reduction in equivalent flow rate at 90% capture was primarily the result of sorbent circulation limitations at operating temperatures combined with pre-loading of the sorbent with CO 2 prior to entering the adsorber. Specifically, CO 2 -rich gas was utilized to convey sorbent from the regenerator to the adsorber. This gas was nominally 45°C below the regenerator temperature during testing. ADA’s post-combustion capture system with modifications to overcome pilot constraints, in conjunction with incorporating a sorbent with CO 2 working capacity of 15 g CO 2 /100 g sorbent and a contact time of 10 to 15 minutes or less with flue gas could provide significant cost and performance benefits when compared to an MEA system.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Bench-scale Development of an Advanced Solid Sorbent-based CO 2 Capture Process for Coal-fired Power Plants

It is increasingly clear that CO 2 capture and sequestration (CCS) must play a critical role in curbing worldwide CO 2 emissions to the atmosphere. Development of these technologies to cost-effectively remove CO 2 from coal-fired power plants is very important to mitigating the impact these power plants have within the world’s power generation portfolio. Currently, conventional CO 2 capture technologies, such as aqueous-monoethanolamine based solvent systems, are prohibitively expensive and if implemented could result in a 75 to 100% increase in the cost of electricity for consumers worldwide. Solid sorbent CO 2 capture processes – such as RTI’s Advanced Solid Sorbent CO 2 , Capture Process – are promising alternatives to conventional, liquid solvents. Supported amine sorbents – of the nature RTI has developed – are particularly attractive due to their high CO 2 loadings, low heat capacities, reduced corrosivity/volatility and the potential to reduce the regeneration energy needed to carry out CO 2 capture. Previous work in this area has failed to adequately address various technology challenges such as sorbent stability and regenerability, sorbent scale-up, improved physical strength and attrition-resistance, proper heat management and temperature control, proper solids handling and circulation control, as well as the proper coupling of process engineering advancements that are tailored for a promising sorbent technology. The remaining challenges for these sorbent processes have provided the framework for the project team’s research and development and target for advancing the technology beyond lab- and bench-scale testing. Under a cooperative agreement with the US Department of Energy, and part of NETL’s CO 2 Capture Program, RTI has led an effort to address and mitigate the challenges associated with solid sorbent CO 2 capture. The overall objective of this project was to mitigate the technical and economic risks associated with the scale-up of solid sorbent-based CO 2 capture processes, enabling subsequent larger pilot demonstrations and ultimately commercial deployment. An integrated development approach has been a key focus of this project in which process development, sorbent development, and economic analyses have informed each of the other development processes. Development efforts have focused on improving the performance stability of sorbent candidates, refining process engineering and design, and evaluating the viability of the technology through detailed economic analyses. Sorbent advancements have led to a next generation, commercially-viable CO 2 capture sorbent exhibiting performance stability in various gas environments and a physically strong fluidizable form. The team has reduced sorbent production costs and optimized the production process and scale-up of PEI-impregnated, fluidizable sorbents. Refinement of the process engineering and design, as well as the construction and operation of a bench-scale research unit has demonstrated promising CO 2 capture performance under simulated coal-fired flue gas conditions. Parametric testing has shown how CO 2 capture performance is impacted by changing process variables, such as Adsorber temperature, Regenerator temperature, superficial flue gas velocity, solids circulation rate, CO 2 partial pressure in the Regenerator, and many others. Long-term testing has generated data for the project team to set the process conditions needed to operate a solids-based system for optimal performance, with continuous 90% CO 2 capture, and no operational interruptions. Data collected from all phases of testing has been used to develop a detailed techno-economic assessment of RTI’s technology. These detailed analyses show that RTI’s technology has significant economic advantages over current amine scrubbing and potential to achieve the DOE’s Carbon Capture Program’s goal of >90% CO 2 capture rate at a cost of < $40/T-CO 2 captured by 2025. Through this integrated technology development approach, the project team has advanced RTI’s CO 2 capture technology to TRL-4 (nearly TRL-5, with the missing variable being testing on actual, coal-fired flue gas), according to the DOE/FE definitions for Technology Readiness Levels. At a broader level, this project has advanced the whole of the solid sorbent CO 2 capture field, with advancements in process engineering and design, technical risk mitigation, sorbent scale-up optimization, and an understanding of the commercial viability and applicability of solid sorbent CO 2 capture technologies for the U.S. existing fleet of coal-fired power plants.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Development of Mixed-Salt Technology for CO 2 Capture from Coal Power Plants

SRI International (SRI), in collaboration with Stanford University, OLI Systems (OLI), Politecnico de Milano (PoliMi), and Aqueous Systems Aps (ASApS) performed a 45-month effort to develop a promising Mixed-Salt Process (MSP) for carbon dioxide capture. The MSP combines existing ammonia and potassium-carbonate technologies with improved absorption steps for rate enhancement and ammonia emission reduction and a novel selective regeneration process with a high-pressure CO 2 product to introduce a new and advanced transformational solvent-based technology. The striking advantages of the SRI MSP include: low heat of reaction, high loading of CO 2 , high-pressure regeneration of > 99% pure dry CO 2 , low sensitivity to impurities, low process cost, use of a non-degradable low-cost solvent with a very low carbon footprint for its production, low emissions, and reduced water use compared to the state-of-the-art ammonia-based and amine technologies. The overall objective of the project was to develop and test a solvent-based CO 2 capture technology that can capture CO 2 from existing or new pulverized coal (PC) power plants at low cost. Our specific goal was to test SRI’s newly developed MSP at the large bench-scale level to demonstrate that the process could capture CO 2 at high efficiency (> 90%) with very high CO 2 loading (> 10 wt.%), require less than 2 GJ/tonne for solvent regeneration, and produce a CO 2 stream at high pressure with a purity > 95 vol.%. This 45-month MSP development program was designed to conduct (1) extensive test campaigns with different process flowsheet variants, and (2) detailed thermodynamic, kinetic, and process modeling. These tests and models were very important to identify any issues associated with the process in the early stages and then resolve them before moving into the next scale-up (> 1 MWe scale) testing. The technology development plan consisted of balanced experimental and process modeling activities as shown in Figure i. Such an approach reduces the risks associated with the process operability at large scales and provides capital and operating expenditure (CAPEX/OPEX) predictions with improved accuracies. Under the MSP development program at SRI, we performed an aggressive testing campaign with individual subsystems as well as integrated CO 2 capture and regeneration system to identify the best operating conditions. The project was carried out in two budget periods (BP1 & BP2).

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2018

Development of Mixed-Salt Technology for CO 2 Capture from Coal Power Plants (Final Report)

SRI International (SRI), in collaboration with Stanford University, OLI Systems (OLI), Politecnico de Milano (PoliMi), and Aqueous Systems Aps (ASApS) performed a 45-month effort to develop a promising Mixed-Salt Process (MSP) for carbon dioxide capture. The MSP combines existing ammonia and potassium-carbonate technologies with improved absorption steps for rate enhancement and ammonia emission reduction and a novel selective regeneration process with a high-pressure CO 2 product to introduce a new and advanced transformational solvent-based technology. The striking advantages of the SRI MSP include: low heat of reaction, high loading of CO 2 , high-pressure regeneration of > 99% pure dry CO 2 , low sensitivity to impurities, low process cost, use of a non-degradable low-cost solvent with a very low carbon footprint for its production, low emissions, and reduced water use compared to the state-of-the-art ammonia-based and amine technologies. The overall objective of the project was to develop and test a solvent-based CO 2 capture technology that can capture CO 2 from existing or new pulverized coal (PC) power plants at low cost. Our specific goal was to test SRI’s newly developed MSP at the large bench-scale level to demonstrate that the process could capture CO 2 at high efficiency (> 90%) with very high CO 2 loading (> 10 wt.%), require less than 2 GJ/tonne for solvent regeneration, and produce a CO2 stream at high pressure with a purity > 95 vol.%. This 45-month MSP development program was designed to conduct (1) extensive test campaigns with different process flowsheet variants, and (2) detailed thermodynamic, kinetic, and process modeling. These tests and models were very important to identify any issues associated with the process in the early stages and then resolve them before moving into the next scale-up (> 1 MWe scale) testing. Such an approach reduces the risks associated with the process operability at large scales and provides capital and operating expenditure (CAPEX/OPEX) predictions with improved accuracies. Under the MSP development program at SRI, we performed an aggressive testing campaign with individual subsystems as well as integrated CO 2 capture and regeneration system to identify the best operating conditions. The project was carried out in two budget periods (BP1 & BP2).

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2018

Enhancement of the Extraction of Uranium from Seawater

Due to the limited uranium resources available for recovery through mining and ore processing and to the environmental problems associated with these operations, the future of nuclear power depends, to a large extent, on the feasibility of recovery of uranium from the ocean. While the amounts of uranium in the ocean are sufficient to fulfill the nuclear industry for many thousands of years, recovery of uranium from the ocean is hampered by its low concentration (3.3 parts per billion) and the presence of many other solutes in seawater at comparable or much higher concentrations. Thus, the only hope for economically viable recovery of uranium from the ocean lies in the development of adsorbents with high capacity and high selectivity for uranium as present in the seawater environment (pH 8.1, U(VI) oxidation state, anionic carbonate complexes). Moreover, it is quite unlikely that economically viable recovery of uranium could be achieved if the adsorbent could be used only once. Thus it is essential to develop adsorbents that can be used through multiple cycles of uranium adsorption followed by elution of the uranium to regenerate the adsorbent without significant degradation of their capacity and selectivity for uranium. Adsorbents used in the large majority of studies aimed at recovery of uranium from seawater are based on the use of radiation grafting to produce polymeric supports, in particular polyethylene, with attached amidoxime groups. This configuration has been concluded to offer the best candidate for use in recovery based on studies which were performed in the early 1980’s. Substantial progress has been made in improving the amidoxime-based adsorbents. The basic approach undertaken by the authors of the proposal, on the other hand, has been to test ligands which have not been included in the scoping studies of the 1980’s or have been developed since then. So far, 18 such ligands have been tested, of which three, including B2MP (an organic phosphate), DAOx (an organic oxalate), and Br-PADAP (an azo compound) have been selected for further investigation. In addition, Winged Nylon 6 has been identified as a promising polymeric support in view of its large surface area and high chemical stability. Furthermore, improved grafting techniques intended to achieve high grafting density under “green chemistry” conditions, i.e., in aqueous media, have been developed. These techniques include the use of surfactants to enhance the solubility of ligands in water and the use of a homopolymerization inhibitor to promote grafting rather than homopolymerization. Furthermore, unlike amidoxime-based adsorbents, which require a chemical treatment step following the radiation grafting to convert a nitrile group to amidoxime, the adsorbents developed by the authors do not require an additional step after grafting. Highly effective regeneration has been demonstrated for the phosphate-grafted polymeric adsorbent over at least 21 adsorption/elution cycles without significant loss of capacity. The currently proposed study is intended to build upon the progress made so far in developing alternative systems for removal of uranium from seawater. It will focus on the following objectives: Continued searches will be conducted for high-capacity, high-selectivity ligands based on systematic characterization of structural features favorable to uranium adsorption. (For instance, phosphates have been found to be much more effective than the corresponding phosphonates). At the same time, development and testing of the three ligands selected so far will continue, focusing on issues such as high grafting densities and effective regeneration. Testing will be conducted in non-spiked sweater (3.3 µg/L U) and lightly spiked seawater (up to 10 µg/L U). The authors have recently been able to refurbish an ICP-MS spectrometer for this purpose. Improved grafting techniques will be developed and refined for specific ligands. These techniques will include the use of surfactants to allow grafting of ligands with low solubility in water, the use of homopolymerization inhibitors, modifying the chemical structure of ligands to introduce C=C bonds, investigating possible modification of the surface of the polymeric support, and mechanistic analysis of the effects of grafting conditions, in particular accumulated dose and dose rate. Improvements in the characterization of adsorbents before and after contact with seawater will be implemented using techniques such as XPS, SEM-EDS, and zeta potential measurements to investigate the mechanism of uranium adsorption. Effective techniques of multi-cycle regeneration of promising adsorbents without degradation of their performance will be developed and refined through testing of mild, preferably near-neutral eluant solutions. The kinetics of adsorption and desorption of uranium will be investigated. This study is of great operational value and it will also greatly contribute to improved understanding of adsorption/desorption mechanism on promising adsorbents.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Combined Sorbent/WGS-based CO 2 Capture Process with Integrated Heat Management for IGCC Systems

Southern Research has developed a combined CO 2 capture water-gas shift (WGS) process for integrated gasification combined cycle (IGCC) applications. A highly efficient regenerable magnesium based sorbent was prepared to remove CO 2 . It offers high and stable CO 2 capacity with minimum requirement for temperature and pressure swings. Under optimized conditions, the sorbents achieved up to 8 mmol/g of CO 2 working capacity and remained stable over 500 cycles of adsorption and regeneration. The selected WGS process achieved 96% CO per pass conversion and remained isothermal during the test duration that lasted over 500 cycles. The approach showed potential to reduce cost of electricity (COE) compared to the baseline carbon capture approaches. The process is for bench-scale and pilot development. In a commercial embodiment, syngas from the gasifier is cooled to warm gas conditions. It then enters the CO 2 sorbent-shift reactor that uses an efficient MgO-based CO 2 sorbent and a commercial catalyst to shift the CO to CO 2 and capture 90% + of the carbon. Using a dual-bed arrangement, the sorbent is regenerated periodically by a combination of pressure and temperature swing to maintain steady state conditions and produce a 95+ % CO 2 stream for sequestration. The hydrogen rich syngas is sent to the IGCC for power production. In addition to consolidating CO 2 capture with WGS, the proposed process reduces parasitic energy losses by operating at warm gas temperatures and reduces parasitic plant load (i.e., steam and auxiliary power) by reducing energy required for regeneration. The project consisted of 3 budget periods (BP) of laboratory-scale research and testing with go/no-go decisions after BP-1 and BP-2. In the 12 month BP-1, it was shown show that one promising sorbent maintained the required CO 2 capacity and durability of >1.5 mmol/g over 100 cycles. Also based on sorbent and WGS experiments in separate reactors and combined reactor modeling, it was shown that the process had the potential to capture 90% of the CO 2 at a lower than conventional amine-based approach. In the 18 month BP-2, a lab scale combined sorbent/WGS reactor system was built, commissioned, and tested with the promising sorbent from BP-1. 90% carbon capture was demonstrated over 100 cycles and it was shown that the process continued to have potential to capture 90% of the carbon at a cost that was less than the conventional amine-based approach. In the 6 month BP-3, a long term test was conducted using the best SR sorbent. The required durability of > 2 mmol/g was demonstrated after 500 cycles. Also, 90% carbon capture and 96% CO conversion was maintained over 1000 cycles. A technical and economic feasibility study was carried out to compare the proposed pre-combustion approach to a gasification plant employing a conventional pre-combustion approach and a conventional pulverized caol (PC) plant employing a conventional post combustion CO 2 capture approach.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

CO2 Capture Strategies via Mineralization with Industrial Waste Brines

Large coal-fired power plants (>500 MW) account for 30% of global CO2 emissions, and long-term management of this CO2 to is urgently needed mitigate global temperature increases. Sequestration of CO2 within stable mineral carbonates (e.g., CaCO3) represents an attractive emission reduction strategy because it offers a leakage-free alternative to geological storage of CO2 in an environmentally friendly form. We have previously described a mineralization process in which divalent cations are sourced from various waste streams (e.g., produced water and brackish water) and alkalinity is induced via regenerable ion-exchange materials (Bustillos et. al. Frontiers in Energy Research. 2020, 8, 352). In our process, aqueous carbonate-bearing streams with pH > 8 are produced by contacting fresh water and carbon dioxide with various ion-exchange materials (e.g., Na form zeolites or ion exchange resins). These streams are mixed with produced water containing varying concentrations (~0.01 – 1.0 M) of Ca2+ leading to the precipitation of solid calcium carbonate (PCC). This process has the advantages of using regenerable solids in a simple and continuous process to increase the pH of water by ion exchange instead of relying on the consumption of costly and unsustainable sources of alkalinity (e.g., sodium hydroxide). While once-through column experiments showed the above benefits, the same were yet to established in a steady-state process with recycle streams. In this work, we set up a process simulation to quantify the energy requirements and CO2 emissions associated with the process and seek optimal produced water compositions and CO2 concentrations (5 – 20 vol%). The process simulation was set up in ASPEN Plus using eRNTL as the thermodynamic property method and sequential modular strategy. Ion exchange alkaline solution was simulated using sodium hydroxide and validated against the experimental data obtained from once-through kinetic experiments. Nanofiltration and reverse osmosis membrane steps were also implemented for the separation of divalent cations and production of fresh water and a regeneration stream following mineralization. Sensitivity analysis was carried out using a range of produced water compositions (0.01 – 1.0 M Ca2+, 0.001 – 0.15 M Mg2+, 0.5 – 3.5 M Na+ and 0.0004 – 0.002 M Fe2+) according to the United States Geological Survey (USGS) database. Calcium carbonate yields increased with increasing CO2 concentrations and were maximized using produced water compositions with larger Ca2+ concentrations. Maximum calcium carbonate yields produced at 5 vol%, 12 vol% and 20 vol% CO2 were 2.3 mmol/L, 5.5 mmol/L, and 9.3 mmol/L, respectively, with the formation of brucite (a magnesium hydroxide phase, Mg(OH)2) and goethite (an iron hydroxide phase, FeOOH) as the primary contaminant phases (99% calcite, 0.6% brucite, 0.4% goethite), which agree with phases detected by XRD experimentally. These results indicate high purity calcium carbonate can be precipitated using industrial waste streams. Consequentially, energy consumption and net CO2 emissions were minimized where precipitated calcium carbonate was maximized for all produced water compositions and CO2 concentrations. Minimum energy consumptions were 0.21 kWh/ton CO2 processed, with 98% of the energy input required coming from the membrane filtration steps. Produced water compositions with large Na+ concentrations (> 0.5 M) were effective at reducing energy consumptions due to faster regeneration time of ion exchange materials. Additionally, calculated net CO2 emissions were negative for the process and ranged from -0.02 kg/ton CO2 to -0.15 kg/ton CO2 processed, indicating a low emission process. We will also present techno-economic assessment showing the economic benefits of the current process as an alternative to the addition of stoichiometric bases to induce alkalinity for the precipitation of CaCO3.

Simonetti, Dante↗
DOE OSTI2023

Gradient Amine Sorbents for Low Vacuum Swing CO 2 Capture at Ambient Temperature

The growing concerns over CO 2 emissions have led to the development of various methods for CO 2 capture. CO 2 capture by amine-based sorbents has been achieved by temperature (thermal) swing adsorption (TSA) process, pressure swing adsorption (PSA) process, and temperature pressure or vacuuming swing adsorption (TPSA or TVSA) process for CO 2 capture. Amine sorbents for energy-efficient TSA, PSA, VSA, TPSA or TVSA CO 2 capture should possess a capability which allow adsorbed CO 2 to desorb and amine sorbent to be regenerated at low temperatures or low vacuums. Development of such amine sorbents would significantly decrease energy consumption and sorbent degradation during the regeneration step. The objective of this project is to develop a low vacuum swing adsorption (VSA) process for the capture of CO 2 from air. The focus is on the development of amine sorbent which allows CO 2 to adsorb in the form of weakly adsorbed CO 2 . The weakly adsorbed CO 2 species can be collected from the sorbent by applying a low vacuum at ambient temperature. Specifically, no heating (i.e., thermal energy) is needed for regeneration of amine sorbents. This novel sorbent allows VSA to be operated at ambient temperature without a significant energy demand. This process eliminates the energy-intensive heating and cooling process in temperature swing adsorption (TSA) process. Ambient temperature operation could prolong the lifetime of sorbent and minimize the maintenance cost. Extensive sorbent studies with in-situ infrared spectroscopy have revealed the modifications of conventional amine sorbents with additives can increase the fraction of weakly adsorbed CO 2 . The amine sorbents with loaded CO 2 can be regenerated in part by the following approaches: (i) mild heating to temperatures below 70 °C, (ii) flowing purging gas over modified amine sorbents at temperatures below 40 °C, (iii) vacuuming at pressure below 0.2 atm and temperatures below 40 °C. The performance of these modified amine sorbents has been tested in a 60 grams VSA unit at ambient temperatures. The results show that weakly adsorbed CO 2 which can be desorbed from modified amine sorbents with purging gas at 100 cc/min can also be evacuated at a vacuum of 1 psia at room temperature. A preliminary techno- economic analysis indicates the major cost of the VSA process with modified amine sorbents stems from the operation of vacuum pumps. Thus, developing an excellent sealing with minimum leakage for the VSA unit is the most critical task for further the development of this VSA technology.

36 MATERIALS SCIENCE↗