Adsorption removal of mercury from flue gas by metal selenide: A review.

Mercury (Hg) pollution has been a global concern in recent decades, posing a significant threat to entire ecosystems and human health due to its cumulative toxicity, persistence, and transport in the atmosphere. The intense interaction between mercury and selenium has opened up a new field for studying mercury removal from industrial flue gas pollutants. Besides the advantages of good Hg° capture performance and low secondary pollution of the mineral selenium compounds, the most noteworthy is the relatively low regeneration temperature, allowing adsorbent regeneration with low energy consumption, thus reducing the utilization cost and enabling recovery of mercury resources. This paper reviews the recent progress of mineral selenium compounds in flue gas mercury removal, introduces in detail the different types of mineral selenium compounds studied in the field of mercury removal, reviews the adsorption performance of various mineral selenium compounds adsorbents on mercury and the influence of flue gas components, such as reaction temperature, air velocity, and other factors, and summarizes the adsorption mechanism of different fugitive forms of selenium species. Based on the current research progress, future studies should focus on the economic performance and the performance of different carriers and sizes of adsorbents for the removal of Hg0 and the correlation between the gas-particle flow characteristics and gas phase mass transfer with the performance of Hg0 removal in practical industrial applications. In addition, it remains a challenge to distinguish the oxidation and adsorption of Hg0 quantitatively.

A comprehensive review of deactivation and modification of selective catalytic reaction catalysts installed in cement kilns.

After the ultralow emission transformation of coal-fired power plants, cement production became China's leading industrial emission source of nitrogen oxides. Flue gas dust contents at the outlet of cement kiln preheaters were as high as 80-100 g/m3, and the calcium oxide content in the dust exceeded 60%. Commercial V2O5(-WO3)/TiO2 catalysts suitable for coal-fired flue gas suffer from alkaline earth metal Ca poisoning of cement kiln flue gas. Recent studies have also identified the poisoning of cement kiln selective catalytic reaction (SCR) catalysts by the heavy metals lead and thallium. Investigation of the poisoning process is the primary basis for analyzing the catalytic lifetime. This review summarizes and analyzes the SCR catalytic mechanism and chronicles the research progress concerning this poisoning mechanism. Based on the catalytic and toxification mechanisms, it can be inferred that improving the anti-poisoning performance of a catalyst enhances its acidity, surface redox performance-active catalytic sites, and shell layer protection. The data provide support in guiding engineering practice and reducing operating costs of SCR plants. Finally, future research directions for SCR denitrification catalysts in the cement industry are discussed. This study provides critical support for the development and optimization of poisoning-resistant SCR denitrification catalysts.

Usage of Chlorella and diverse microalgae for CO2 capture - towards a bioenergy revolution.

To address climate change threats to ecosystems and the global economy, sustainable solutions for reducing atmospheric carbon dioxide (CO2) levels are crucial. Existing CO2 capture projects face challenges like high costs and environmental risks. This review explores leveraging microalgae, specifically the Chlorella genus, for CO2 capture and conversion into valuable bioenergy products like biohydrogen. The introduction section provides an overview of carbon pathways in microalgal cells and their role in CO2 capture for biomass production. It discusses current carbon credit industries and projects, highlighting the Chlorella genus's carbon concentration mechanism (CCM) model for efficient CO2 sequestration. Factors influencing microalgal CO2 sequestration are examined, including pretreatment, pH, temperature, irradiation, nutrients, dissolved oxygen, and sources and concentrations of CO2. The review explores microalgae as a feedstock for various bioenergy applications like biodiesel, biooil, bioethanol, biogas and biohydrogen production. Strategies for optimizing biohydrogen yield from Chlorella are highlighted. Outlining the possibilities of further optimizations the review concludes by suggesting that microalgae and Chlorella-based CO2 capture is promising and offers contributions to achieve global climate goals.

Comparative corrosion behavior of three titanium alloy base materials and their welds in a simulated chimney environment.

This study investigates the corrosion behavior of titanium alloys (TA2, TC4, TB6) in a 3 % sulfuric acid flue gas environment using electrochemical tests and microscopic analyses (SEM/EDS, XRD, metallographic microscopy). Results show that TA2 base metal has lower corrosion resistance compared to its weld metal, while TC4 and TB6 exhibit opposite trends. Specifically, TC4 and TB6 base metals have lower corrosion current densities (0.9 and 0.5 µA/cm2) and higher corrosion potentials then their weld metals (1.93 and 2 µA/cm2). In contrast, TA2 base metal showed higher corrosion current density (2 µA/cm2) than its weld metal (0.35 µA/cm2) and HAZ metal (0.16 µA/cm2). Microscopic analyses reveal ß phase transitions in TC4 and TB6 weld areas, leading to larger grain sizes and reduced corrosion resistance. Conversely, TA2 retains finer grains post-welding, enhancing its corrosion resistance. These insights clarify weld corrosion effects and provide valuable guidance for industrial applications of titanium alloys, particularly in designing and maintaining titanium alloy chimneys.

Effect of Tourmaline Addition on the Anti-Poisoning Performance of MnCeOx@TiO2 Catalyst for Low-Temperature Selective Catalytic Reduction of NOx.

In view of the flue gas characteristics of cement kilns in China, the development of low-temperature denitrification catalysts with excellent anti-poisoning performance has important theoretical and practical significance. In this work, a series of MnCeOx@TiO2 and tourmaline-containing MnCeOx@TiO2-T catalysts was prepared using a chemical pre-deposition method. It was found that the MnCeOx@TiO2-T2 catalyst (containing 2% tourmaline) exhibited the best low-temperature NH3-selective catalytic reduction (NH3-SCR) performance, yielding 100% NOx conversion at 110 °C and above. When 100-300 ppm SO2 and 10 vol.% H2O were introduced to the reaction, the NOx conversion of the MnCeOx@TiO2-T2 catalyst was still higher than 90% at 170 °C, indicating good anti-poisoning performance. The addition of appropriate amounts of tourmaline can not only preferably expose the active {001} facets of TiO2 but also introduce the acidic SiO2 and Al2O3 components and increase the content of Mn4+ and Oα on the surface of the catalyst, all of which contribute to the enhancement of reaction activity of NH3-SCR and anti-poisoning performance. However, excess amounts of tourmaline led to the formation of dense surface of catalysts that suppressed the exposure of catalytic active sites, giving rise to the decrease in catalytic activity and anti-poisoning capability. Through an in situ DRIFTS study, it was found that the addition of appropriate amounts of tourmaline increased the number of Brønsted acid sites on the catalyst surface, which suppressed the adsorption of SO2 and thus inhibited the deposition of NH4HSO4 and (NH4)2HSO4 on the surface of the catalyst, thereby improving the NH3-SCR performance and anti-poisoning ability of the catalyst.

Enhancement of fine particle removal through flue gas cooling in a spray tower with packing materials.

The efficient removal of fine particles from coal-fired flue gas poses challenges for conventional electrostatic precipitators and bag filters. Recently, a novel approach incorporating deep cooling of the flue gas has been proposed to enhance the removal of gaseous pollutants and particles. However, the achievable efficiency and underlying mechanisms of particle capture within the gas cooling system remain poorly understood. This study aims to elucidate the effectiveness of gas cooling in enhancing the removal of particles through a laboratory-scale spray tower equipped with packing materials. The results demonstrate a significant increase in particle removal efficiency, from 63.4 % to over 98 %, as the temperature of the spray liquid decreases from 20℃ to -20℃. Notably, this enhancement is particularly pronounced for particles sized 0.1-1 µm, with efficiency rising from approximately 40 % to 95 %, effectively eliminating the penetration window. Moreover, we find that the spray flow rate positively influences particle removal capability, while the height of the packing section exhibits an optimal value. Beyond this optimal height, particle removal performance may decline due to an inadequate liquid-to-packing ratio. To provide insight into the capture process, we introduce a single-droplet model demonstrating that particle capture is primarily enhanced through the augmented thermophoretic force.

Exploring alkali-treated corn cob for high-rate removal of NOX and SO2 from flue gas: Focus on carbon release capacity, removal performance, and comparison with conventional carbon sources.

This investigation explored the potential of utilizing alkali-treated corn cob (CC) as a solid carbon source to improve NOX and SO2 removal from flue gas. Leaching experiments unveiled a hierarchy of chemical oxygen demand release capacity: 0.03 mol/L alkali-treated CC > 0.02 mol/L > 0.01 mol/L > 0.005 mol/L > control. In NOX and SO2 removal experiments, as the inlet NOX concentration rose from 300 to 1000 mg/m3, the average NOX removal efficiency increased from 58.56 % to 80.00 %. Conversely, SO2 removal efficiency decreased from 99.96 % to 91.05 %, but swiftly rebounded to 98.56 % by day 18. The accumulation of N intermediates (NH4+, NO3-, NO2-) increased with escalating inlet NOX concentration, while the accumulation of S intermediates (SO42-, SO32-, S0) varied based on shifts in the population of functional bacteria. The elevation in inlet NOX concentration stimulated the growth of denitrifying bacteria, enhancing NOX removal efficiency. Concurrently, the population of nitrate-reducing sulfur-oxidizing bacteria and sulfate-reducing bacteria expanded, aiding in the accumulation of S0 and the removal of SO2. The comparison experiments on carbon sources confirmed the comparable NOX and SO2 removal efficiencies of alkali-treated CC and glucose, yet underscored differences in intermediates accumulation due to distinct genus structures.

Optimization of municipal solid waste incineration for low-NOx emissions through numerical simulation.

With urbanization, municipal solid waste (MSW) generation is increasing. Traditional landfill methods face land shortages and environmental pollution. Waste incineration, which reduces waste and recovers resources, has become a key management method. However, nitrogen oxides (NOx) produced during incineration severely impact the environment, requiring improved control technologies. This study optimized three denitrification technologies-air staging, flue gas recirculation (FGR), and selective non-catalytic reduction (SNCR)-using numerical simulations. The research provides support for improving waste incinerator efficiency and stability while reducing NOx emissions, aiding the sustainable development of waste incineration technology. By optimizing the primary and secondary air distribution ratios, the initial NOx generation was reduced by 8.39%. When 20% of the recirculated flue gas was introduced as secondary air, NOx generation was reduced by 23.54%, and boiler efficiency increased to 83.78%. The study examined the impact of different sludge mixing ratios on the temperature and NOx emissions within the context of municipal solid waste (MSW) incineration. Initially, the study aimed to address the environmental concerns of NOx emissions during the incineration process by exploring how the introduction of sludge at various mixing ratios would affect combustion parameters. The results showed that a sludge mixing ratio between 3 and 13% optimized the combustion process with 7% being the most effective in balancing temperature control and NOx emissions. Specifically, the best value of the sludge mixing ratio refers to achieving an optimal reduction in NOx emissions while maintaining stable incinerator operation. The chemical compositions of the sludge included key elements such as carbon (C), hydrogen (H), nitrogen (N), sulfur (S), and oxygen (O), with approximate proportions of C: 31.2%, H: 4.7%, N: 2.5%, S: 0.6%, and O: 31.8%.

Decoupling the influence of NOx in flue gas on the application of nano-amorphous selenium for mercury removal.

Nitrogen oxides are inevitable hazardous components in coal-fired flue gas. This study designed a series of experiments and combined theoretical calculations to systematically investigate the effect of NOx on the removal of element mercury (Hg0) by nano-amorphous selenium (nano-a-Se). It was found that the impact of NOx on the removal of Hg0 by nano-a-Se primarily involves two mechanisms: competitive adsorption between NOx and Hg0, and the induced reduction effect of NOx on chemisorbed mercury (HgSe). NO inhibits the removal of Hg0 by nano-a-Se, and competitive adsorption is identified as the main influencing factor. Whereas the inhibitory effect of NO2 on the adsorption of Hg0 by nano a-Se can be counteracted due to its oxidizing effect on Hg0. Therefore, although NO2 presents stronger competitiveness than NO in the competitive adsorption with Hg0, it still shows a promoting effect on Hg0 removal, with 50 ppm NO2 restoring 5.7 % of the Hg0 removal efficiency. Additionally, the mechanism of NOx-induced reduction of HgSe was investigated in detail. NO2 is more capable of inducing the reduction of Hg(II) from HgSe to Hg0. This study presents new insights into the underlying influence mechanism, which could provide valuable references for the application of other selenium-based adsorbents.

Application of a microalga, Tetradesmus obliquus PF3, for NO and CO2 removal from actual flue gas via cultivating in wastewater.

Greenhouse gas (GHG) emissions, particularly anthropogenic emissions, are the primary drivers of climate change. The cultivation of microalgae represents a highly promising strategy for mitigating atmospheric GHG levels. The growth characteristics and GHG mitigation capabilities of Tetradesmus obliquus PF3 were investigated in domestic wastewater at a thermal power plant. The maximum cell density and productivity were 1.52 ± 0.01 g L-1 and 0.33 ± 0.01 g L-1 day-1, respectively. Utilizing a serial configuration of two reactors, the elimination efficiency of NO and CO2 attained values of 78 ± 4% and 14 ± 4%, respectively. NO concentration at the outlet was less than 24.6 ± 2.9 mg m-3, meeting the latest Chinese discharge limits. Besides, the recovery efficiency of NO and CO2 increased to 77 ± 8% and 2.24 ± 0.04%, respectively, compared to that of the single reactor (40 ± 3%, 0.9 ± 0.0%). A removal efficiency of over 90% was achieved for TN and TP in domestic wastewater. The concentrations of COD (76.5 mg L-1), NH4+-N (0.9 mg L-1), TN(6.31 mg L-1), and TP (0.35 mg L-1) in effluent were below the thresholds of 100 mg L-1, 25 mg L-1, none data, and 3 mg L-1, respectively, complying with the Chinese Discharge Standard (Class II criteria set forth) for Municipal Wastewater Treatment Plants Pollutants. The harvested biomass exhibited a high content of carbohydrates and proteins, making it a viable feedstock for biofuels and bio-fertilizers. Our results demonstrate that Tetradesmus obliquus PF3-based flue gas treatment technology can simultaneously realize GHG removal, wastewater bio-remediation, and biomass recovery.

SO3 removal by submicron absorbents synthesized via inhibition method: The product layer grows like parallel peaks.

Injecting calcium hydroxide powder into the flue gas is an effective strategy for SO3 removal. However, commercial calcium hydroxide has several disadvantages, including large particle size, low efficiency, and unsuitability for excessive grinding. In this work, sub-micron calcium hydroxide was synthesized by an inhibition method and its performance for SO3 removal from flue gas was investigated on a pilot-scale platform (120 Nm3/h). When the concentration of sodium alginate solution was 100 mg/L, the average particle size of calcium hydroxide decreased from 13.66 µm to 0.84 µm, which improved the SO3 removal (92.1 %) and conversion of the absorbent. The results of the fixed-bed experiments indicate that the absorption kinetics of the reaction is consistent with the Bangham model. In addition, density functional theory verifies that calcium hydroxide captures SO3 by chemisorption. The AFM image shows that the calcium sulfate whiskers produced during the reaction grow like parallel peaks on the adsorbent surface. The calculations suggest that the driving force for SO3 adsorption originates from Ca-p orbital (Ca(OH)2) and O-s orbital (SO3) hybridization. This study complements the island growth mechanism for gas-solid two-phase reactions and provides an effective method for removing SO3 from flue gas in coal-fired power plants. In addition, it will provide an important reference for the development of submicron adsorbents.

FGD-Gypsum Waste to Capture CO2 and to Recycle in Building Materials: Optimal Reaction Yield and Preliminary Mechanical Properties.

The use of waste to capture CO2 has been on the rise, to reduce costs and to improve the environmental footprint. Here, a flue gas desulfurization (FGD) gypsum waste is proposed, which allows us to obtain a CaCO3-based solid, which should be recycled. The CO2 capture stage has primarily been carried out via the direct carbonation method or at high temperature. However, a high energy penalty and/or long reaction times make it unattractive from an industrial perspective. To avoid this, herein an indirect method is proposed, based on first capturing the CO2 with NaOH and later using an aqueous carbonation stage. This allows us to capture CO2 at a near-ambient temperature, improving reaction times and avoiding the energy penalty. The parameters studied were Ca2+/CO32- ratio, L/S ratio and temperature. Each of them has been optimized, with 1.25, 100 mL/g and 25 °C being the optimal values, respectively, reaching an efficiency of 72.52%. Furthermore, the utilization of the produced CaCO3 as a building material has been analyzed. The density, superficial hardness and the compressive strength of a material composed of 10 wt% of CaCO3 and 90 wt% of commercial gypsum, with a water/solid ratio of 0.5, is measured. When the waste is added, the density and the mechanical properties decreased, although the compressive strength and superficial hardness are higher than the requirements for gypsum panels. Thus, this work is promising for the carbonation of FGD-gypsum, which involves its chemical transformation into calcium carbonate through reacting it with the CO2 of flue gasses and recycling the generated wastes in construction materials.

Carbon capture in power sector of China towards carbon neutrality and its comparison to renewable power.

CO2 capture from coal power plants is an important and necessary solution to realizing carbon neutrality in China, but CCS demonstration deployment in power sector is far behind expectations. Hence, the reduction potential of energy consumption and cost for CCS and its competitiveness to renewable powers are very important to make roadmaps and policies toward carbon neutrality. Unlike the popular recognition that capturing CO2 from flue gases is technically and commercially mature, this paper notes that it has been proved to be technically feasible but far beyond technology maturity and high energy penalty leads to its immaturity and therefore causes high cost. Additionally, the potential energy penalty reduction of capture is investigated thermodynamically, and future CO2 avoidance cost is predicted and compared to renewable power (solar PV and onshore wind power). Results show that energy penalty for CO2 capture can be reduced by 48%-57%. When installation capacity reaches a similar scale to that of solar PV in China (250 GW), CO2 capture cost in coal power plants can be reduced from the current 28-40 US$/ton to 10-20 US$/ton, and efficiency upgrade contributes to 67%-75% in cost reduction for high coal price conditions. In China, CO2 capture in coal power plants can be cost competitive with solar PV and onshore wind power. But it is worth noting that the importance and share of CCS role in CO2 emission reduction is decreasing since renewable power is already well deployed and there is still a lack of large-scale CO2 capture demonstrations in China. Innovative capture technologies with low energy penalties need to be developed to promote CCS. Results in this work can provide informative references for making roadmaps and policies regarding CO2 emission reductions that contribute towards carbon neutrality.

Research progress on elemental mercury (Hg0) removal in flue gas using non-thermal plasma technology.

Elemental mercury (Hg0) removal is a crucial target for mercury pollution control in flue gas. This article focuses on Hg0 removal in flue gas using corona discharge (CD) and dielectric barrier discharge (DBD) technologies, and provides a mechanistic perspective on the development and influencing factors of non-thermal plasma (NTP) technology for Hg0 removal. The influence factors include reactor configurations, power supplies, energy density, residence time, oxidation methods, gas composition, and the synergy between NTP and catalysis/adsorption, etc. This study reveals that the use of a pulsating electrical power supply significantly increases electron densities in both CD and DBD systems, thereby ensuring high energy efficiency and economic viability. Cl2 proves to be more effective than HCl as a chlorine source for Hg0 removal. NO significantly reduces Hg0 oxidation efficiency, while the effects of SO2 and H2O remain unclear. Energy density distribution is closely related to plasma devices, power supplies, and overall reactor configurations. Direct oxidation proves to be more effective than indirect oxidation for Hg0 removal. The combination of NTP with adsorption/catalysis technologies shows significantly better Hg0 removal efficiency compared to using NTP alone. This study can provide theoretical support for enhancing Hg0 removal mechanisms and optimizing process control parameters in industrial applications of NTP technology.

New insights and reaction mechanisms in the design of catalysts for the synergistic removal of NOx and VOCs from coke oven flue gas: Dual regulation of oxidative properties and acidic sites.

The acid and redox sites of the MnCo catalysts are simultaneously fine-tuned by the addition of V. A dual-function catalyst, designated as V0.5Mn5Co5, has been constructed for the synergistic removal of NOx and volatile organic compounds under coke-oven flue gas conditions, which exhibits > 95 % NOx conversion and > 80 % N2 selectivity at 180-300 °C. Meanwhile, it removes 70 % of ethylene at 240 °C. Besides it has excellent sulfur and water resistance. The characterization results indicate that this acid-redox dual sites modulation strategy appropriately weakens the oxidation capacity of the catalysts while increasing the surface acidity of the catalysts. The catalyst mainly performs SCR reaction through the E-R mechanism, and N2O is generated through the transition dehydrogenation of NH3 and NSCR reaction. Ethylene is first adsorbed on the catalyst surface then oxidized to form carbonate species, and finally decomposed to CO2. Ethylene oxidation follows the MvK mechanism. There is a competitive adsorption between NH3 and C2H4, and a mutual inhibition between the SCR reaction and the ethylene oxidation reaction. V0.5Mn5Co5 exhibits excellent synergistic removal of NOx and VOCs in coke oven flue gas compared with commercial VWTi catalysts, which indicates great promise for industrial application.

Sulfide-carbonate-mineralized functional bacterial consortium for cadmium removal in flue gas.

Sulfide-carbonate-mineralized functional bacterial consortium was constructed for flue gas cadmium biomineralization. A membrane biofilm reactor (MBfR) using the bacterial consortium containing sulfate reducing bacteria (SRB) and denitrifying bacteria (DNB) was investigated for flue gas cadmium (Cd) removal. Cadmium removal efficiency achieved 90%. The bacterial consortium containing Citrobacter, Desulfocurvus and Stappia were dominated for cadmium resistance-nitrate-sulfate reduction. Under flue gas cadmium stress, ten cadmium resistance genes (czcA, czcB, czcC, czcD, cadA, cadB, cadC, cueR, copZ, zntA), and seven genes related to sulfate reduction, increased in abundance; whereas others, nine genes related to denitrification, decreased, indicating that cadmium stress was advantageous to sulfate reduction in the competition with denitrification. A bacterial consortium could capable of simultaneously cadmium resistance, sulfate reduction and denitrification. Microbial induced carbonate precipitation (MICP) and biological adsorption process would gradually yield to sulfide-mineralized process. Flue gas cadmium could transform to Cd-EPS, cadmium carbonate (CdCO3) and cadmium sulfide (CdS) bioprecipitate. The functional bacterial consortium was an efficient and eco-friendly bifunctional bacterial consortium for sulfide-carbonate-mineralized of cadmium. This provides a green and low-carbon advanced treatment technology using sulfide-carbonate-mineralized functional bacterial consortium for the removal of cadmium or other hazardous heavy metal contaminants in flue gas.

Comprehensive transcriptomic and metabolomic insights into simultaneous CO2 sequestration and nitrate removal by the Chlorella vulgaris and Pseudomonas sp. consortium.

Simultaneous CO2 sequestration and nitrate removal can be achieved by co-cultivation of Chlorella vulgaris with Pseudomonas sp. However, a comprehensive understanding of the synergistic mechanism between C. vulgaris and Pseudomonas sp. remains unknown. In this study, transcriptomics and metabolomics analysis were employed to elucidate the synergistic mechanism of C. vulgaris and Pseudomonas sp. Transcriptomic and metabolomic analyses identified 3664 differentially expressed genes and 314 metabolites. Transcriptome analysis revealed that co-culture with Pseudomonas sp. promoted the photosynthesis of C. vulgaris by promoting the synthesis of photosynthetic pigments and photosynthesis-antenna proteins. Furthermore, it stimulated pathways associated with energy metabolism from carbon sources, such as the Calvin cycle, glycolytic pathway, and TCA cycle. Additionally, Pseudomonas sp. reduced nitrate levels in the co-culture system by denitrification, and microalgae regulated nitrate uptake by down-regulating the transcript levels of nitrate transporter genes. Metabolomic analysis indicated that nutrient exchange was conducted between algae and bacteria, and amino acids, phytohormones, and organic heterocyclic compounds secreted by the bacteria promoted the growth metabolism of microalgae. After supplementation with differential metabolites, the carbon fixation rate and nitrate removal rate of the co-culture system reached 0.549 g L-1 d-1 and 135.4 mg L-1 d-1, which were increased by 20% and 8%, respectively. This study provides a theoretical insight into microalgae-bacteria interaction and its practical application, as well as a novel perspective on flue gas treatment management.

Comprehensive Analysis of Biomass from Chlorella sorokiniana Cultivated with Industrial Flue Gas as the Carbon Source.

Chlorella sorokiniana, isolated from a pond adjacent to a cement plant, was cultured using flue gas collected directly from kiln emissions using 20 L and 25000 L photobioreactors. Lipids, proteins, and polysaccharides were analyzed to understand their overall composition for potential applications. The lipid content ranged from 17.97% to 21.54% of the dry biomass, with carotenoid concentrations between 8.4 and 9.2 mg/g. Lutein accounted for 55% of the total carotenoids. LC/MS analysis led to the identification of 71 intact triacylglycerols, 8 lysophosphatidylcholines, 10 phosphatidylcholines, 9 monogalactosyldiacylglycerols, 12 digalactosyldiacylglycerols, and 1 sulfoquinovosyl diacylglycerol. Palmitic acid, oleic acid, linoleic acid, and α-linolenic acid were the main fatty acids. Polyunsaturated fatty acid covers ≥ 56% of total fatty acids. Protein isolates and polysaccharides were also extracted. Protein purity was determined to be ≥75% by amino acid analysis, with all essential amino acids present. Monomer analysis of polysaccharides suggested that they are composed of mainly D-(+)-mannose, D-(+)-galactose, and D-(+)-glucose. The results demonstrate that there is no adverse effect on the metabolite profile of C. sorokiniana biomass cultured using flue gas as the primary carbon source, revealing the possibility of utilizing such algal biomass in industrial applications such as animal feed, sources of cosmeceuticals, and as biofuel.

Temperature-Pressure Swing Process for Reactive Carbon Capture and Conversion to Methanol: Techno-Economic Analysis and Life Cycle Assessment.

A model was developed to conduct techno-economic analysis (TEA) and life cycle assessment (LCA) for reactive carbon capture (RCC) and conversion of carbon dioxide (CO2) to methanol. This RCC process is compared to a baseline commercialized flue gas CO2 hydrogenation process. An ASPEN model was combined with existing TEA and LCA models into a larger TEA/LCA framework in Python. From preliminary experimental data, the model found a levelized cost of $0.79/kg methanol for the baseline process and $0.99/kg for the RCC process. The cradle-to-gate carbon intensity of the baseline process was 0.50 kg-CO2e/kg-methanol, compared to 0.55 kg-CO2e/kg-methanol for the RCC process. However, water consumption for RCC (10.21 kg-H2O/kg-methanol) is greatly reduced compared to the baseline (12.89 kg-H2O/kg-methanol). Future improvements in hydrogen electrolysis costs will benefit the RCC. A target H2/methanol mass ratio of 0.26 was developed for RCC laboratory experiments to reduce methanol cost below the baseline. If a ratio of 0.24 can be achieved, a levelized cost of $0.76/kg methanol is projected, with a carbon intensity of 0.42 kg-CO2e/kg-methanol.

Bilayer Porous Electrocatalysts for Stable and Selective Electrochemical Reduction of CO2 to Formate in the Presence of Flue Gas Containing NO and SO2.

The development of stable and selective electrocatalysts for converting CO2 to value-added chemicals or fuels has gained much interest in terms of their potential to mitigate anthropogenic carbon emissions. Most of the electrocatalysts are tested under pure CO2; however, industrial outlet flue gas contains numerous impurities, such as NO and SO2, which poison the electrocatalysts and alter the product selectivity. Developing electrocatalysts that are resistant to such impurities is essential for commercial implementation. Herein, we prepared bilayer porous electrocatalysts, namely, Sn, Bi, and In, on porous Cu foam mesh (Sn/Cu-f, Bi/Cu-f, and In/Cu-f) by a two-step electrodeposition process and employed these electrodes for the electrochemical reduction of CO2 to formate. It was observed that the bilayer porous electrocatalysts exhibited high CO2 reduction activity compared to catalysts coated on a Cu mesh. Among bilayer porous electrocatalysts, Sn/Cu-f and Bi/Cu-f electrocatalysts showed more than 80% faradaic efficiency (FE) toward formate production, with a formate partial current density of around -16 and -10.4 mA cm-2, respectively, at -1.02 V vs RHE. In/Cu-f electrocatalyst showed nearly 40% formate FE with formate partial current density of -15 mA cm-2 at -1.22 V vs RHE. We investigated the effect of NO and SO2 impurities (500 ppm of NO, 800 ppm of SO2, and 500 ppm of NO + 800 ppm of SO2) on these electrocatalysts' selectivity and stability toward formate. It was observed that the Bi/Cu-f electrocatalyst showed 50 h stability with 80 ± 5% formate FE, and Sn/Cu-f showed 18 h stability with above 80 ± 5% efficiency in the presence of NO and SO2 mixed with CO2. Furthermore, we studied the effect of CO2 concentration with Sn/Cu-f and Bi/Cu-f catalysts in the range of 15-100% CO2, for which formate FEs of 45-80% were observed.