Carbon Conversion Research Articles

Ce3+/Ce4+ Ion Redox Shuttle Stabilized Cuδ+ for Efficient CO2 Electroreduction to C2H4

AbstractThe CO2 electroreduction reaction has advantages in clean and pollution‐free carbon conversion, but it still faces challenges in carbon utilization efficiency and improving the selectivity of C2 products. Although the dynamic Cuδ+ state is known to favor the C−C coupling process, the suitable Cuδ+ species for electrocatalytic reduction of CO2 are difficult to maintain under the conditions of strong reduction and large current. Herein, we propose a Ce doping strategy to stabilize the Cuδ+ state (Ce/CuOx) during the CO2RR process, which enables a high Faradaic efficiency of 60 % for multi‐carbon products (40 % for C2H4, 14 % for CH3CH2OH, and 6 % for CH3COOH), and 25 h stability at −1.2 V versus the reversible hydrogen electrode. In situ infrared spectroscopy, in situ X‐ray photoelectron spectroscopy combined with density functional theory calculations reveal that the Cuδ+ is stabilized by the redox ion pairs of Ce, which reduces the energy barrier of *CO coupling, and improves the Faraday efficiency of electrocatalytic CO2 reduction of C2H4. This work provides a new idea to make full use of lanthanide variable value metals for advanced catalysis and clean energy conversion.

Atomic-Scale Tailoring C-N Coupling Sites for Efficient Acetamide Electrosynthesis over Cu-Anchored Boron Nitride Nanosheets.

Electrochemical conversion of carbon and nitrogen sources into valuable chemicals provides a promising strategy for mitigating CO2 emissions and tackling pollutants. However, efficiently scaling up C-N products beyond basic compounds like urea remains a significant challenge. Herein, we upgrade the C-N coupling for acetamide synthesis through coreducing CO and nitrate (NO3-) on atomic-scale Cu dispersed on boron nitride (Cu/BN) nanosheets. The specific form of Cu, such as single atom, nanocluster, and nanoparticles, endows Cu/BN different adsorption capacity for CO and NO3-, thereby dictating the catalytic activity and selectivity for acetamide formation. The Cu nanocluster-anchored BN (Cu NCs/BN) catalyst achieves an industrial-level current density of 178 mA cm-2 for the C-N coupling reaction and an average acetamide yield rate of 137.0 mmol h-1 gcat.-1 at -1.6 V versus the reversible hydrogen electrode. Experimental and theoretical analyses uncover the pivotal role of the strong electronic interaction between Cu nanoclusters and BN, which activates CO and NO3-, facilitates the formation of key *CCO and *NH2 intermediates, and expedites the C-N coupling pathway to acetamide. This work propels the development of atomic structure catalysts for the efficient conversion of small molecules to high-value chemicals through electrochemical processes.

Effect of biochar on the co-conversion of carbon-nitrogen and humification of kitchen waste composting process

Composting was an effective technique to treat kitchen waste into high-quality fertilizer or soil amendment. During the composting process of kitchen waste, different degradation rates of carbon and nitrogen resulted in carbon loss, nitrogen emission and low product quality. Consequently, the aim of this study was to investigate the mechanisms and effects of biochar (5%, 10% and 15%) on synergistic conversion of nitrogen and carbon and humification processes in kitchen waste composting. The findings revealed that the addition of 10% and 15% biochar prolonged the thermophilic phase (>55°C) by a minimum of three days compared to CK. Additionally, the final NH4+-N concentration in the 10% and 15% treatment groups exhibited a 66.7% reduction in comparison to the control. Besides, the 15% addition proved more efficacious in reducing the NH4+-N content. The increase in biochar facilitates the adsorption of ammonia nitrogen and influences the structure of the microbial community, especially Bacteroides and Pseudoxanthomonas, thus promoting nitrogen mineralisation and humification, which provides energy and carbon for the survival and metabolism of more microorganisms. The compost with 15% biochar exhibited higher levels of SBR1031, resulting in a 73.8% increase in the conversion of nitrogen to NO3--N compared to the control. The aforementioned behaviour facilitates a synergistic conversion of nitrogen and carbon. Therefore, the addition of biochar promotes synergistic carbon and nitrogen transformations in terms of nitrogen conservation, organic matter decomposition, microbial species and their interactions, which is essential for the production of value-added compost fertilizers.

Experimental and modeling insights into the kinetics of calcium looping CO2 capture process: Assessment of limestone treatment

This investigation aimed to offer a precise and detailed understanding of the intricate mechanisms governing the rapid and diffusion stages of carbonation within the calcium looping process, while also exploring the effects of treatment on mineral limestone (Raw limestone) as the primary sorbent for CO2 capture. Two modified samples treated with acetic acid (Acidified limestone) and hydrophobic silica nanoparticles (Silica-mixed limestone), were analyzed to provide deeper insights into the kinetics of the slow and fast stages of the carbonation reaction. The Acidified limestone had a significant influence on the carbonation conversion rates of both the rapid and slow stages, resulting in a notable enhancement in conversion efficiency. Notably, the carbonation conversion rates in the 20th cycle were measured as 0.201, 0.348, and 0.231 for the Raw, Acidified, and Silica-mixed limestones, respectively. An increase in the number of reaction cycles led to an increased percentage contribution of the diffusion stage, a decrease in transition time and consequently, a reduction in the overall carbonation conversion rate. Specifically, the share percentage of carbonation conversion for the diffusion stage in the 20th cycle was determined as 31.55%, 34.88%, and 30.36% for the Raw, Acidified, and Silica-mixed limestones, respectively. The results obtained from the modeling application demonstrated a reduction in the maximum absolute error with an increase in the reaction cycles. Additionally, the prediction results indicated that the carbonation conversion rates for the Raw and Acidified limestones in the 100th cycle were determined to be 0.07 and 0.12, respectively.

Predominance of aminated water interfaces on transition-metal nanoparticulate to enhance synergetic removal of carbonyls and inhibition of CO2 production

In the context of the air quality co-benefits of carbon neutrality, conventional strategies for the end-of-pipe control reduction of volatile organic compounds (VOCs) towards carbon dioxide (CO2) need to be revised more realistically. This study explored the synergetic removal of carbonyls with low carbon emission by amine-functionalized manganese dioxide (MnO2), obtained with a method involving freezing-thawing cycles. Molecular-level characterization revealed that an ordered array of interfacial water dimers (H5O2+, a class of water-proton clusters) on the MnO2 surface enhanced the robust bonding of metal sites with amino groups. Amine-functionalized MnO2 can be negatively charged under environmental acidity to further interfacial proton-coupled electron transfers. Cooperativity in the interfacial chemical processes facilitated the selective conversion of carbonyl carbons to bicarbonated amides (NH3+HCO3−) as a reservoir of CO2. Compared with a commercially used 2,4-dinitrophenylhydrazine (DNPH) control, the nearly complete removal of a priority carbonyl mixture containing formaldehyde, acetaldehyde, and acetone was attained synergically. The secondary organic compounds in the gas phase and CO2 off-gas were suppressed.

Ether chain-modified Alkanolguanidine for CO2 capture and subsequent conversion

Capturing CO2 and converting it into valuable chemicals has attracted considerable attention in recent years. Herein, a kind of ether chain-modified alkanolguanidines (ECMAs) was designed and synthesized as a dual functional reagent for carbon dioxide capture and conversion. Due to the presence of basic sites and CO2-philic ether chains, these ECMAs demonstrated almost equimolar CO2 capture at room temperature and atmospheric pressure through the synergy of physical and chemical absorption. Even for diluted CO2 (15 % CO2), 0.7 mol CO2 per mole capture reagent can still be achieved, showing their potential application in post-combustion capture. The synthesized ECMAs can also serve as catalyst in the cycloaddition reaction of CO2 with various epoxides, affording 75–99 % yield of corresponding cyclic carbonates under 3 MPa CO2 with tetrabutylammonium iodide (TBAI) as co-catalyst. Moreover, these ECMAs can be applied to the integrated CO2 capture and conversion, in which the ECMAs can react with CO2, forming the alkyl carbonate zwitterion as active CO2 species in the capture step. And in the subsequent cycloaddition reaction with propylene oxide, 52 % yield of propylene carbonate was obtained.

Advances and Applications of Carbon Capture, Utilization, and Storage in Civil Engineering: A Comprehensive Review

This paper thoroughly examines the latest developments and diverse applications of Carbon Capture, Utilization, and Storage (CCUS) in civil engineering. It provides a critical analysis of the technology’s potential to mitigate the effects of climate change. Initially, a comprehensive outline of CCUS technologies is presented, emphasising their vital function in carbon dioxide (CO2) emission capture, conversion, and sequestration. Subsequent sections provide an in-depth analysis of carbon capture technologies, utilisation processes, and storage solutions. These serve as the foundation for an architectural framework that facilitates the design and integration of efficient systems. Significant attention is given to the inventive application of CCUS in the building and construction industry. Notable examples of such applications include using carbon (C) in cement and promoting sustainable cement production. Economic analyses and financing mechanisms are reviewed to assess the commercial feasibility and scalability of CCUS projects. In addition, this review examines the technological advances and innovations that have occurred, providing insight into the potential future course of CCUS progress. A comprehensive analysis of the environmental and regulatory environments is conducted to evaluate the feasibility and compliance with the policies of CCUS technology deployment. Case studies from the real world are provided to illustrate effectiveness and practical applications. It concludes by emphasising the importance of continued research, policy support, and innovation in developing CCUS technologies as a fundamental component of sustainable civil engineering practices. A tenacious stride toward carbon neutrality is underscored.

Sugarcane bagasse and iron ore tailings thermochemical conversion towards sustainable iron recovery with biogenic carbon and hydrogen production

The recovery of valuable chemical elements from industrial waste is essential for production processes' economic and environmental sustainability. The interaction between the iron ore tailings and sugarcane bagasse, both wastes, has the potential to provide a secondary iron source for future iron and steelmaking processes. This study evaluated the use of volatiles from sugarcane bagasse (SCB) and iron ore tailings (IOT) to the synergistic promotion of carbon deposition, H2 production and conversion of weak magnetic iron oxides in strong magnetic iron phases. The experiments were carried out at 400, 600, 800, and 1000 ºC with different SCB/IOT ratios under an N2 atmosphere. In all tests, SCB and IOT were heated simultaneously in separate beds to prevent direct contact between the materials. The combination of 600 ºC and higher SCB/IOT ratio resulted in a product with 96.7% magnetite, 98% magnetic fraction recovery, and 3.5% deposited carbon. The use of lower SCB/IOT ratio provided an increase in H2 production. Regardless of the mass ratio, heating the IOT and SCB simultaneously up to 1000 ºC led to significant mineralogical transformations, reaching reduced phases such as wüstite, fayalite and metallic iron, which impaired magnetic separation efficiency. The results indicate an alternative for recovering iron from IOT using biomass waste as a renewable reducing agent for the steel industry.

Impregnated layer solution combustion synthesized CaO-based composite pellets with enhanced CO2 sorption property

The impregnated layer solution combustion synthesis (SCS) technique was employed to synthesize CaO-based sorbents supported by inert stabilizers so as to improve the cyclic CO2 uptake stability. Four different inert stabilizers were evaluated for their impact on the cyclic CO2 uptake stability of sorbents. It found that the Mg-based inert stabilizer significantly outperforms the other three in improving cyclic CO2 sorption capabilities of sorbents synthesized by the impregnated layer SCS method. Moreover, MgO-supported sorbent pellets were prepared via graphite hydrophobic layer-assisted casting, with the magnesia load within the pellets being regulated between 15 and 45 wt %. It is the addition of MgO stabilizer that significantly improves the performance of CaO-based sorbents, with the improvements being notably more pronounced at higher MgO loads. The calcium-based sorbent pellets containing 45 wt % MgO show extremely stable CO2 sorption performance; after 17 cycles, the carbonation conversion rate is 73.6%, about three times the rate of pellets without MgO loading. The uniform dispersion of MgO inert stabilizer inside pellets improves high-temperature sintering resistance and, concurrently, enhances the mechanical property. Furthermore, the use of waste cigarette butts as impregnated layer templates, rather than other organic additives, will significantly reduce the cost of synthesizing MgO-supported CaO-based sorbents.Graphical

Simultaneously comparing various CO2-mineralized steelmaking slags as supplementary cementitious materials via high gravity carbonation

The integration of accelerated carbonation with the utilization of steelmaking slags presents a vital strategy for CO2 mineralization towards net-zero scheme. This study simultaneously evaluates basic oxygen furnace slag (BOFS), refining slag (RFS), and electric arc furnace reducing (EAFRS) and oxidizing slags (EAFOS) as potential partial replacements for ordinary Portland cement, at substitution levels ranging from 5 % to 15 % as supplementary cementitious materials (SCMs). These slags were pretreated through aqueous accelerated carbonation in a high-gravity rotating packed bed. We assessed several parameters, including carbonation conversion, CO2 capture capacity, workability, strength, and durability. The results demonstrated that EAFRS achieved the highest CO2 capture capacity, reaching 0.193 kg-CO2/kg-slag with a maximum carbonation conversion of 46 % under 197 times high-gravity conditions and a liquid-to-solid ratio of 20. While the incorporation of carbonated slags had minimal impact on the setting properties of cement pastes, higher substitution ratios necessitated increased water demand. The strength of blended cement containing 5 %, 10 %, and 15 % of carbonated BOFS, RFS, and EAFRS met standard requirements at 28th day. Additionally, a mathematical model was developed to predict the mechanical strength of cement mortars. The introduction of carbonated BOFS, RFS, and EAFRS facilitated hydration due to the formation of calcium carbonates, although it resulted in slower strength development kinetics. Notably, the replacement of cement with carbonated EAFOS exhibited a higher expansion rate, likely due to its elevated silicon dioxide and alkaline species content, which may lead to alkali-aggregate reactions, resulting in expansion and cracking.

Investigation on co-gasification performances of sewage sludge and polyolefins by thermogravimetric analyze and two-stage fixed bed reactor

Co-gasification of biomass with hydrogen-rich feedstock is a promising method to improve H2 yield. Thus, in this work, co-gasification performances and corresponding promotion/inhibition effects of sewage sludge (SS) and three types of polyolefins (PE, PP and PS) were investigated in the thermogravimetric analyze and two-stage fixed bed reactor. Thermogravimetric experiments results indicated that with the addition of polyolefins, the initial temperature of blends progressively elevated, while its terminal temperature declined, suggesting that adding polyolefins facilitated the decomposition of samples. The thermal degradation of blends was distinguished into two stages, and in the first stage, a negative interaction was found at 25 % polyolefins mass ratio, but a positive interaction was occurred at 50 % and 75 % polyolefins mass ratios. Meanwhile, in the second stage, a negative interaction was obtained for blending with PE, whereas an opposite result was observed for blending with PP or PS. Therefore, temperature, feedstock and mixing ratio interacted on synergy effects between SS and polyolefins. Besides, two-stage fixed bed experiments results suggested that a higher gasification temperature was beneficial for the production of syngas, particularly the H2 yield, and blending with polyolefins into SS enhanced the H2 content, with PE performing best. The synergy interactions between SS and polyolefins accelerated the concentrations of H2 and CH4, while declining the CnHm yield, demonstrating a stronger re-cleavage of macromolecules. Furthermore, the low heat value of syngas and carbon conversion efficiency for all the samples separately elevated and reduced with rising gasification temperature and polyolefins mass ratios. At 800 °C, the highest gasification efficiency of samples could be achieved with the addition of 50 % PP or PS. This study provides a basis for the application of SS and polyolefins co-gasification.

Ce3+/Ce4+ Ion Redox Shuttle Stabilized Cuδ+ for Efficient CO2 Electroreduction to C2H4.

The CO2 electroreduction reaction has advantages in clean and pollution-free carbon conversion, but it still faces challenges in carbon utilization efficiency and improving the selectivity of C2+ products. Although the dynamic Cuδ+ state is known to favor the C-C coupling process, the Cuδ+ species suitable for electrocatalytic reduction of CO2 are difficult to maintain under the conditions of strong reduction and large current. Herein, we propose a Ce doping strategy (Ce/CuOx) to protect the Cuδ+ state in the CO2RR process, which enables a high Faradaic efficiency of 60% for multi-carbon products (40% for C2H4, 14% for CH3CH2OH, and 6% for CH3COOH), and 25 h stability at -1.2 V versus the reversible hydrogen electrode. In-situ infrared spectroscopy, in-situ XPS combined with density functional theory calculations reveal that the Cuδ+ is stabilized by the redox ion pairs of Ce, which reduces the energy barrier of *CO coupling, and improves the Faraday efficiency of electrocatalytic CO2 reduction of C2H4. This work provides an idea to make full use of lanthanide variable value metals to maintain the stability of dynamic Cuδ+ state and improve the performance of electrocatalytic CO2 reduction to C2H4.

Enhancing Mycoprotein Yield: Metabolic Modulation of Chitin Synthase in Fusarium venenatum.

Fusarium venenatum is being extensively utilized for microbial protein production. However, its high dietary fiber content results in substantial carbon loss. Inhibition of chitin biosynthesis presents a promising strategy to improve the mycoprotein yield. Through transcriptomic and bioinformatics analyses, chitin synthase gene FvChs3 was identified as crucial for chitin synthesis in F. venenatum. Knockout of the FvChs3 gene resulted in mycelial expansion and a 26% reduction in the chitin content of strain ΔFvChs3. Ethanol production from fermentation decreased by 47%, while the carbon conversion efficiency and protein conversion increased by 16% and 36%, respectively. Transcriptomic analysis revealed an upregulation of nitrogen metabolism in ΔFvChs3, while genes related to the glycolysis pathway for ethanol synthesis were downregulated. Further knockout of pyruvate decarboxylase gene FvPDC6 in ΔFvChs3 accelerated growth, leading to improvements in carbon and protein conversion of 29% and 40%, respectively. This research lays the foundation for enhancing fungal protein production.

Reactive carbon capture using saline water: evaluation of prospective sources, processes, and products.

Reactive carbon capture (RCC) processes involve the capture of carbon dioxide (CO2) and conversion to a value-added product using a single sorbent/reaction medium. Not only can RCC processes generate valuable byproducts that can reduce the cost of carbon capture, but RCC tends to have lower energy demand than processes involving the transfer of CO2 between the mediums used for capture and subsequent reactions. Saline water has been proposed as a potential medium for RCC due to it's relative abundance and low cost. Additionally, the composition and chemistry of many saline water sources: (1) elevates the CO2 content (as compared to atmospheric concentrations), (2) provides various cations that can form valuable products with CO2, and (3) enhances the kinetics of chemical reactions used to convert CO2 to stable byproducts. In addition to established industrial processes for converting CO2 into inert or valuable byproducts, we found 20 new processes and technologies that have been developed specifically to capture and convert CO2 using saline water. Both preexisting and emerging processes can be broadly classified as electrochemical or chemical titration processes. When assessing the potential viability of applying any of these processes for large scale carbon capture, several factors must be considered, such as the net carbon footprint of the process, the market size, location of customers and value of the end product, the energy demand and chemical costs of the process, and any other environmental impacts. The feasability of many emerging saline-based RCC processes is difficult to determine, as many technologies were tested using synthetic saline waters and/or concentrated CO2 sources. Notwithstanding the early stage of development of many saline-based RCC technologies, the major limitation to implementation of this approach to carbon capture is the mismatch in the scale of the markets for products of saline-based RCC and the scale of carbon capture needed to meet climate goals. However, because the products of many of the processes reviewed here are stable and non-hazardous, these technologies may also be used for carbon sequestration efforts where the products are managed as waste, in which case the carbon capture potential of these technologies can surpass the market-imposed limitations on RCC. Thus, the potential benefits of saline water-based RCC identified in this review encourage further study and development of these technologies.

Chemical looping gasification of waste plastics for syngas production using NiO/Al2O3 as dual functional material

This study investigates the chemical looping gasification (CLG) of typical waste plastic, polypropylene (PP), using NiO/Al2O3 as a dual functional material, i.e. oxygen carrier (OC) and catalyst. The whole PP-CLG process comprises PP gasification, coke steam oxidation, and OC air regeneration with the first one being the key step for syngas production. Four operation modes for PP gasification were studied and compared, which were distinguished by whether PP and OC were premixed, and whether the heating rate was fast or slow. Significant differences in the product distribution, PP conversion ratio, and the roles that NiO/Al2O3 played were observed under different modes. The highest syngas yield (64.7 mmol/g-PP), carbon conversion (64.9 %), and minimum coke deposition (19.3 %) during PP gasification were achieved through a combination of premixing and fast heating (Type A). Benefitting from its extensive lattice oxygen supply and the effective catalytic cracking capabilities of NiO/Al2O3, Type A accelerated volatile conversion, demonstrated elevated CO selectivity, and reduced tar content, thereby enhancing PP-syngas conversion efficiency. Direct CLG of PP was genuinely realized in Type A, which is different from the traditional pyrolysis-reforming scheme for syngas production. Characterizations further illustrated that the NiO/Al2O3 in Type A produced coke that was the easiest to remove, experienced less sintering, and exhibited the highest lattice oxygen utilization ratio. The findings are expected to provide practical guidance for the choice of a suitable reaction pathway maximizing the waste plastics to syngas conversion.

Enhanced syngas production via plastic rubber chemical looping gasification: Role of iron–nickel oxide oxygen carriers

To meet the growing demand for efficient waste management solutions, a novel method called Plastic Rubber Chemical Loop Gasification (PRCLG) offers an innovative and effective approach to the thermal treatment of rubber and plastic waste, producing high-purity fuel and hydrogen-rich syngas. In this study, iron-nickel oxide was synthesized and used as an oxygen carrier to facilitate the PRCLG process. The impact of these oxygen carriers on syngas production was thoroughly investigated, and the evolution of the oxygen carrier's activity was analyzed through changes in the microenvironment during the gasification process. Experimental results showed that under pyrolysis conditions at 750 °C, the syngas yield was 1142 mL/g. After introducing a controlled atmosphere with 1.5 mL/h of water vapor, the syngas yield increased to 2150 mL/g. Further enhancement of the syngas yield using a catalyst resulted in a yield of 3562 mL/g, with a carbon conversion rate of 94%. The study confirmed that optimal syngas yields were achieved at 750 °C, highlighting the importance of precise temperature control. Over ten cycles spanning 600 min, the iron-nickel oxide oxygen carrier exhibited stable performance, demonstrating its durability and effectiveness. This innovative PRCLG method not only provides a solution for the disposal of rubber and plastic waste but also contributes to the production of valuable energy resources, aligning with sustainable development goals and advancing waste-to-energy technologies.

Kinetic analysis and model evaluation for steam co-gasification of coal-biomass blended chars using macro-TGA

A macro-thermobalance (macro-TGA) was applied to investigate the steam co-gasification characteristics of the chars produced from Huainan coal (HN), two types of biomasses, sawdust (SD) and wheat straw (WS), and coal-biomass blends at 900–1200 °C under rapid heating conditions. The gasification reaction kinetics were determined by the homogeneous reaction model (VM), shrinking core model (SCM) and random pore model (RPM), and the optimal model was selected by deviation calculation. The results show that the char gasification reactivity increased with the increase of temperature. The promotion effect of biomass semi-coke on coal char mainly occurred in the stage when the carbon conversion rate was greater than 0.5, which is mainly attributed to the migration of active AAEMs to the surface of coal char to catalyze the gasification reaction in the later stage. However, with the increase in temperature, this promoting effect is weakened due to the increasing influence of mass transfer effects over chemical rate control, and increased volatilization of the inorganic species. The RPM model is suitable for describing the coal char gasification process, while the SCM was the model that best fitted the biomass semi-coke and coal/biomass blends, which elucidates the kinetic mechanisms governing the gasification process.

Room-temperature CO2 conversion to carbon using liquid metal alloy catalysts without external energy input

Conversion of CO2 to carbon using a catalyst typically requires significant energy input such as heat, pressure, or electricity. This is due to its strong bonds and the energy needed to initiate the reaction. The energy requirement for CO2 conversion may also lead to carbon emissions if sources are fossil-based. There is less exploration at low temperatures and without an external energy CO2 conversion to solid carbon. Here, we show a liquid metal alloy (In0.2Ga0.8) used as a catalyst for converting CO2 to carbon at room temperature without external energy. The carbon formed was characterized, and the calculated free energy of the reduction reaction was −530 kJ mol−1.The catalyst coated over a ceramic surface observed similar phenomena of CO2 conversion to carbon at room temperature. The conversion was five times higher at catalyst-coated ceramic membranes than at bulk catalysts. The CO2 conversion efficiency was 60 % at the catalytic membrane for continuous flow of CO2 at room temperature. EDX and XPS studies confirmed the formation of carbon at the catalyst surface. Our study may open the topic of membrane-based catalysis of CO2 for practical carbon conversion at lower operating costs at the industrial scale to achieve net-zero emissions.

Microwave-assisted chemical looping gasification of sugarcane bagasse biomass using Fe3O4 as oxygen carrier for H2/CO-rich syngas production

Chemical looping gasification (CLG) is a promising approach for sustainable biomass utilization. The selection of an appropriate heating method is a key challenge in the CLG process. This study investigated microwave-assisted CLG of sugarcane bagasse using Fe3O4 as an oxygen carrier. The effects of microwave power (580, 680, 780, 880, and 980 W) and oxygen carrier to biomass mass ratio (mOC:mSCB) (0:6, 1:5, 2:4, 3:3, 4:2, and 5:1) on product distributions, syngas compositions, syngas efficiencies, and syngas HHVs were studied. Results showed that with increase in microwave power and mOC:mSCB ratio, syngas yield, syngas efficiency, and syngas HHV initially increased and then finally decreased. The optimal conditions were found to be 880 W power and a 3:3 ratio. The optimal syngas yield of 88.23 wt% was achieved in the air reactor at 880 W with a 5:1 ratio. Pyrolysis yielded H2 and CO-enriched syngas, while gasification increased CO concentration. The highest CO + H2 concentration of 64.96 vol% was obtained in the fuel reactor at 880 W with a 3:3 ratio. The maximum thermal efficiency (49.55 %), cold gas efficiency (49.48 %), carbon conversion efficiency (54.42 %), and HHV (16.31 MJ/Nm3) were observed in the fuel reactor at 880 W and a 3:3 ratio. Microwave-assisted heating achieved an impressive heating rate of 1166.40 °C/min at 980 W and 5:1 in air reactor. This study shows that microwave heating can be utilized as efficient heating in CLG for sustainable biomass utilization.

Entrained-flow gasification characteristics of plastic waste pyrolysis oil

Plastic waste (PW) pyrolysis is a promising method in chemical recycling technology; however, PW pyrolysis oil cannot be used directly because of its high contaminant content. Entrained-flow gasification (EFG) is a suitable method for removing contaminants from pyrolysis oil and enhancing the conversion compared with fixed bed or fluidized bed gasification. We examined the basic characteristics of PW pyrolysis oil through EFG with the variation of O2/fuel ratios from 0.6 to 1.4 and steam/fuel ratio from 0.4 to 0.7 at 600–900°C in a lab-scale reactor. The H2 composition and Cold Gas Efficiency (CGE) showed the highest when the O2/fuel ratio was 0.8. The Carbon Conversion Efficiency (CCE) showed the highest values when the ratio was 1.4. C2-C3 gases tended to decrease at higher temperatures because of the thermal cracking of hydrocarbons. In the experiments with the variation of steam/fuel ratio, CO2 concentration decreased with increasing temperature from 600 to 800°C because of the reverse water-gas-shift reaction. The residence time was calculated to review the reaction conditions and was found to be 4.2–7.3 seconds. The experimental data from a lab-scale EFG can serve as fundamental data for the scale-up of integrated pyrolysis and gasification systems.