Oxy-fuel biomass gasification coupled with green hydrogen synthesis offers a promising route for utilizing surplus renewable electricity. However, existing studies focus on steam gasification for maximum hydrogen yield, overlooking CO-selective conversion and the role of inherent oxygen. Here, corn straw and rice husk are gasified under oxy-fuel conditions in a fluidized bed with in-situ sampling. Increasing oxidizing intensity first raises then lowers cold gas efficiency, while higher temperature enhances carbon conversion. Introducing CO2 increases CO yield via the Boudouard reaction, achieving optimal cold gas efficiencies of 65.8 % for corn straw at 15 % CO2 and 68.0 % for rice husk at 10 % CO2; excessive CO2 inhibits O2-mediated oxidation. In corn straw, abundant acetyl/carboxyl groups in hemicellulose undergo decarboxylation and reforming, generating CO2/ H2O, with residual oxygen retained as quinone-type C=O. In rice husk, stable methoxy and beta-O-4 aryl ether linkages in lignin favor homolytic cleavage to CO, while SiO2 encapsulation of cellulose suppresses reactive oxygen release. Furthermore, inherent oxygen actively modulates CO2 gasification efficiency: aliphatic C=O in corn straw promotes decarboxylation, generating competing CO2 that reduces net CO yield from the Boudouard reaction; aromatic C-O in rice husk lignin suppresses side reactions and complements CO2 to enhance CO production. This structure-dependent cooperation or competition between inherent oxygen and CO2 gasification provides a theoretical basis for the zero-carbon route coupling oxy-fuel biomass gasification with green hydrogen to produce green alcohols.

Boron possesses superior gravimetric and volumetric energy densities, yet its practical application is often constrained by complex ignition mechanisms and particle agglomeration. This study investigates the combustion dynamics of naturally agglomerated boron powder using a temperature controllable combustion system. A noncontact optical diagnostic approach, integrating grayscale analysis and pseudo-color thermometry, was developed to quantify ignition delay, luminous intensity, and spatial temperature distributions. Experiments were conducted under varying initial temperatures (900 degrees C, 1000 degrees C, and 1100 degrees C) and oxygen-enriched environments (60%, 70%, 80%, 90%, 100% O2). Results indicate that increasing the initial ambient temperature significantly shortens ignition delay time, whereas oxygen concentration serves as the primary driver for combustion intensity and duration. Specifically, raising the oxygen concentration from 60% to 100% resulted in a fourfold reduction in combustion duration and a marked increase in luminosity. These findings provide critical insights into the coupled effects of temperature and oxidizer concentration on boron kinetics and demonstrate the utility of digital imaging diagnostics for the optimization of boron-based propulsion systems.

The dual-CO2/H2O-reflux supercritical composite working fluid cycles (SCWFCs) can extend the operating flexibility of oxy-fuel power systems, but feasible cycle points must also satisfy flame-stability and combustor-burnout constraints. A multiscale evaluation was performed for CH4 and representative CO/H2 syngas fuels by coupling steady-state cycle analysis, one-dimensional flame calculations, and Chemical Reactor Network (CRN) combustor assessment. Flammability limits, ignition delay time, and laminar flame speed were examined at the fundamental combustion-characteristic scale, while fuel burnout was evaluated under representative combustor organizations and flow-distribution strategies. Dual CO2/H2O reflux widened the admissible operating space relative to single-species reflux, although the surviving windows depended strongly on fuel composition and diluent identity. The SCWFC mechanism, which integrates supercritical water (SCW) and supercritical carbon dioxide (sCO2) elementary chemistry, gave the most consistent behavior from subcritical to supercritical conditions among the tested mechanisms. Under supercritical conditions, finite-rate combustion trends could not be directly transferred among fuel/diluent pairs. CO mitigation was governed first by boundary-condition adjustment and then by multi-stage pressure combustor integration. Combustion organization and reflux-zone design produced stronger CO suppression for CH4 than for syngas. These results provide a constrained cross-scale basis for selecting SCWFC operating windows and guiding combustor design.

Conventional thermal or plasma-only methane decomposition suffers from numerous limitations in catalytic conversion and product formation, hindering efficient H2 and CNTs co-production. Herein, a catalyst-assisted dielectric barrier discharge (DBD) plasma process over a Ni-based catalyst is reported that overcomes this limitation at a moderate temperature of 450 degrees C. With the catalyst positioned within the plasma discharge zone, the system simultaneously achieves relatively high CH4 conversion and H2 selectivity. Multi-scale characterization coupled with reactive molecular dynamics simulations reveals a dual role of plasma: as a reaction driver, plasma initiates the first C-H bond cleavage (CH4*CH3*+H*) while the catalyst surface mediates terminal dehydrogenation (M-CH*M-C+H*), thereby suppressing hydrocarbon by-product formation; and as a nanostructure regulator, the plasma-induced triggers deformation of Ni nanoparticles, templating the tip-growth of multiwalled carbon nanotubes (MWCNTs) with a narrowed average diameter of 42.0 nm. The CNTs exhibit a graphitic structure with tunable defect density governed by plasma ion etching.

The integration of biomass oxy-fuel combustion with renewable energy sources presents a viable and sustainable pathway for the production of green methanol, offering a significant strategy to advance carbon neutrality goals. The high volatile content and alkali-rich nature of biomass limit the applicability of pulverized coal oxy-fuel combustion principles to biomass systems. This study investigates the oxy-fuel combustion characteristics of typical biomass fuels in a circulating fluidized bed experimental system, with particular focus on CO2 gasification etching effects and in-situ biochar structural evolution. Results indicate that the oxy-fuel atmosphere enhances carbon enrichment by 15.8% for corn straw and 11.2% for rice husk, respectively, while improving burnout efficiency. The process preferentially attacks N-5 structures, promoting fuel-nitrogen release. High oxygen concentration and CO2 gasification etch internal pores of in situ biochar, cleave aromatic layers, and facilitate outward migration of alkali metals that catalyze combustion. Thermal effects drive deep CO2 etching into microporous structures, enhancing carbon ordering, whereas temperatures above 800 degrees C accelerate large aromatic ring decomposition and carbon matrix collapse. The molten silicate network in rice husk biochar exerts a certain inhibitory effect on oxidative etching. In the late combustion stage, the carbon framework exhibits apparent ordering and structural refinement, accompanied by pore wall collapse and channel merging. The findings offer theoretical and data-driven support for implementing carbon-negative, high-value biomass utilization strategies alongside oxy-fuel combustion technology.

As a reliable peak-shaving power source, coal-fired boilers’ flexible operation technology has become a key support for achieving the low-carbon transition. To enhance the peak-shaving capacity of the boiler, it is urgent to explore the transient mechanisms of flow, combustion, and heat transfer under dynamic conditions. In this study, the heat transfer characteristics of the burner under varying load conditions and the combustion characteristics in boilers under low and dynamic load conditions are investigated by CFD numerical simulation technology based on a 10 MW coal-fired test bench. The results indicate that at load rates of 2%/min and 4%/min, heat flux density remains mostly consistent across the upper wall of the furnace. At 6%/min, the heat flux near dense pulverized coal flow exceeds that near fresh coal flow. At 60% load, the flow fields are symmetrical, optimizing flame filling and distribution. As the load drops to 40%, the upper flow field begins to distort, and by 20% load, turbulence and uneven temperature distribution arise. At 20% load, the one-layer burner demonstrates superior flow field stabilization compared to the two-layer configuration, with particle concentration remaining lower near the wall above the burner but higher in the cold ash hopper, while high-temperature zones predominantly concentrate in the furnace center with minimal areas exceeding 1900 K. A boiler designed for concentration separation enhances airflow and decreases wall particle concentration at 20% load, resulting in a more uniform temperature distribution with high-temperature zones further from the walls.

Methane decomposition is increasingly recognized as pivotal technology for simultaneous production of H2 and carbon nanomaterials, yet its industrial implementation is severely constrained by high operating temperatures and rapid deactivation to thermal catalytic systems. By integrating in-situ optical emission spectroscopy with multi-scale characterization, it is demonstrated that plasma serves a four-fold function in the Fe-based catalytic system: (1) excitation of CH4 into a controllable radical pool, (2) enhancement of radical adsorption energy on Fe surfaces through plasma-induced electronic polarization, (3) implementation of a hydrogen-mediated "pathway pruning" mechanism wherein H* abstracts H from CHx* species, preventing gas-phase polymerization while simultaneously accelerating surface-catalyzed carbon assembly, and (4) in-situ etching of amorphous carbon and promotion of surface hydrogen-assisted dehydrogenation on M-H sites. These coupled mechanisms synergistically suppress electrode carbon deposition, enabling sustained discharge stability and maintaining the plasma discharge in high-efficiency tip-discharge regime. Consequently, at 700 degrees C, the plasma-catalytic system achieves methane conversion of 42.67 % (compared to 25 % in pure plasma at 700 degrees C, and 19.25 % in pure thermal catalytic at 750 degrees C), hydrogen selectivity of 57.88 %, carbon yield of 105 mg center dot gcat enhanced graphitization. This work provides a quantitative mechanistic blueprint for designing next-generation plasma-catalytic systems that overcome the limitations of conventional thermal processes.

Volatile organic compound (VOC) emissions from industrial processes are highly complex, encompassing aromatics, oxygenated VOCs, halogenated hydrocarbons, alkanes, and other species with diverse physicochemical properties. Carbon-based adsorptive removal technologies have been widely adopted for VOC control owing to their operational simplicity, structural tunability, and ability to simultaneously remove multiple VOCs. However, the multi-scale structures of current carbon adsorbents, spanning from adsorption sites to pore networks, remain difficult to tailor simultaneously for VOC molecules with diverse physicochemical characteristics, giving rise to pronounced competitive adsorption in multicomponent VOC systems. Herein, we review multicomponent VOC co-adsorption in carbon materials from a multiscale structure–property matching perspective, extending beyond conventional single-component VOC adsorption to emphasize the origins and regulation of competitive adsorption in multicomponent systems. First, the origins, coupling mechanisms, and the influence of inorganic components on competitive adsorption in multicomponent VOC systems are elucidated. Building on this understanding, pore-structure and surface-chemistry regulation strategies are systematically reviewed. From these, the corresponding structure-performance relationships, predictive models, and simulation methods are summarized to provide design principles for efficient multicomponent VOC removal. Finally, challenges and future directions for the co-adsorption and removal of multicomponent VOCs on carbon materials are proposed. This review is expected to guide the rational design and development of advanced carbon adsorbents toward efficient multicomponent VOC removal.

Pressurized char-O2/H2O combustion offers a promising strategy for efficient carbon conversion and mitigating CO2 emissions, yet the dynamic competition for O2 consumption between char heterogeneous and CO/H2 homogeneous combustion pathways remains poorly understood. This study develops a multiscale kinetic model using the finite volume method (FVM) to simulate single-particle char combustion in a multi-component system under pressurized O2/H2O conditions, uniquely integrating dynamic char structure evolution and boundary layer chemical reactions. Validated against experimental data, the model quantifies the effects of pressure, H2O concentration, and temperature, as well as their coupling effect, on the O2 competition mechanism. Key findings reveal that increasing H2O concentration from 0 % to 40 % reduces the char center temperature by 220.8 K. Radial non-uniformity in heterogeneous reaction rates within the char shows pore diffusion limits. Higher H2O reduces the peak char-O2 combustion rate but boosts the peak CO-O2 rate. When the temperature and H2O concentration change, H2 combustion is the primary pathway for O2 competition, while when the pressure changes, CO combustion is the main path of competition for O2 & sdot;H2O modifies the O2 competition mechanism through a cascade effect encompassing "surface adsorption competition -> gasification product generation -> boundary layer combustion". Pressure changes the spatial distribution of reaction products through the molecular diffusion volume-dependent selective diffusion inhibition effect. Temperature determines the competition weights of CO and H2 combustion through different activation energies of homogeneous reactions. Collectively, these factors drive the dynamic transition of the primary competing pathway between H2 and CO combustion.

Industrial heavy-duty gas turbines are facing the risks of flame blow-off and thermoacoustic oscillations, while submerged combustion within porous media effectively broadens the flammability limits and suppresses thermoacoustic instabilities. However, keeping a stable flame submerged within the porous media under pressurized and high-velocity gas turbine conditions remains a significant challenge. The porous media burners reported in previous studies are adapted for low-speed operation, with a maximum cross-sectional velocity of 8 m/s at atmospheric pressure and 0.5 m/s under pressurized conditions. To adapt porous media combustors for gas turbine applications, this study investigates the effects of "V-graded" pore size gradient topology on flame temperature, stability, and emissions under pressurized (0.1-0.5 MPa) and high-velocity (5-25 m/s) conditions. The results demonstrate direct observation of excess enthalpy flames within the porous media reaching temperatures near 2000 degrees C. The Lambda-graded structure exhibits stronger heat recirculation efficiency and higher flame temperatures, while the V-graded structure achieves a wider flammable limit with the lowest fuel-lean equivalence ratio below 0.3. At high velocities, three structures maintain NO and CO emissions below 50 ppm@15%O2, with the Vgraded structure demonstrating superior performance in controlling the total emissions of NO and CO. The Vgraded structure with high flow resistance exhibits stronger vibration amplitudes compared to other structures. Significant deformation occurs in foam ceramics located within the high-temperature region of the combustion zone, whereas the ordered ceramics exhibit excellent thermal shock resistance.

The development of functional biochar with high-capacity and rapid CO2 adsorption/desorption capabilities is pivotal for compressed CO2 energy storage systems, effectively mitigating renewable energy intermittency and advancing carbon-neutral power grid infrastructure. A porous biochar with hierarchically structured pores and deliberately incorporated nitrogen functional groups is fabricated through hydrothermal treatment followed by chemical activation in this study. A multimodal approach combining experimental adsorption analyses with molecular dynamics and density functional theory simulations systematically elucidates the structure-activity relationships governing CO2 adsorption-desorption equilibrium. The UHTCK biochar demonstrates narrowly distributed micropores (centered at 0.7 nm) within an ideal hierarchical architecture, achieving a CO2 adsorption capacity of 6.01 mmol/g at 0 °C with 92.05% regeneration efficiency after 20 cycles. Edge functionalization enhances surface polarity, facilitating electrostatic-driven weak interactions (e.g., hydrogen bonding) that promote monolayer CO2 confinement in micropores. Mesopores exhibit wall-proximal CO2 accumulation, while nitrogen-doped mesopores optimize diffusion kinetics. Mechanistic analysis reveals that high microporosity enables substantial CO2 storage, while nitrogen-functionalized surfaces and mesopores thermodynamically balance the adsorption and heat to meet the requirements of adsorption-compression CO2 energy storage systems. Strategic pore-functionality engineering enables ambient-condition rapid CO2 cycling through regulated gas-solid-thermal interactions. This work provides theoretical insights and design principles for developing atmospheric-pressure CO2 capture materials, offering transformative potential for next-generation energy storage systems.

Given the bottlenecks of traditional experiments, such as the inability to resolve the independent roles of subreactions, high costs, long cycles, and difficulty in achieving multi-variable combination optimization, this study leverages a 10 kW multi-stage controlled entrained flow experimental system (EFR-MRS) and combines experiments with numerical simulations. It not only explores the NOx emission reduction characteristics and synergistic activation mechanism of pulverized coal reburning modified by syngas coupled with recirculated flue gas but also verifies the reliability of the reburning model. Furthermore, focusing on syngas components (H2: 6 %-60 %, CO: 25 %-80 %, CH4: 2 %-20 %) and the mixing of recirculated flue gas, orthogonal experiments are employed to analyze their influence laws on NOx reduction efficiency. In terms of numerical simulation, a reburning reaction model is established targeting the heterogeneous-homogeneous coupling reaction characteristics of nitrogen oxide reduction in pulverized coal reburning. A refined numerical model is constructed by coupling CHEMKIN with FLUENT: the heterogeneous reaction module is based on the Langmuir-Hinshelwood (LH) mechanism; the homogeneous reaction module integrates the detailed nitrogen chemistry mechanism of coal reburning, covering intermediate generation, free radical chain reactions, and concentration regulation pathways. Meanwhile, regarding the catalytic effect of alkaline metal oxides (Al2O3, CaO, Fe2O3, etc.) in ash, the correlation between mineral catalytic activity parameters and char reaction kinetic equations is established through user-defined functions (UDFs) on the FLUENT platform. On this basis, by designing multiple combined operating conditions of syngas (with adjustable CH4/H2/CO ratios) and recirculated flue gas, the optimal ratio for nitrogen oxide emission reduction is efficiently screened, significantly reducing the cost and cycle of traditional experiments.

In Integrated Gasification Combined Cycle (IGCC) systems, the combustion of syngas may potentially lead to combustion instability and excessive NOx emissions. The technique of micromix combustion with radial staging offers innovative solutions to this problem. The present work examines the effects of radial fuel staging on a swirl micromix flame by integrating experiments with numerical simulations to investigate how the staging ratio influences flame stability and emissions. The results indicate that increasing the staging ratio results in a more concentrated heat release intensity. When the staging ratio is greater than 1.0 at low flow rates, the outer flame's OH* intensity and stability significantly decrease. As the staging ratio increases, the pressure in the combustion chamber gradually rises. Meanwhile, the vibration frequency and intensity of high-frequency pressure decrease. The flame can be attributed to three main zones: the inner recirculation zone, the outer recirculation zone, and the flame overlap zone. These zones exhibit frequencies of approximately 220 Hz, 430 Hz, and 1000 Hz, respectively. As the staging ratio increases, NOx emissions increase, while CO emissions remain nearly constant. Novelty and significance statement: Micromix combustion technology represents an emerging solution for achieving low nitrogen oxide combustion in syngas gas turbines. In micromix combustion technology, the introduction of fuel staging strategies shows potential for further mitigating thermoacoustic coupling risks in micromix flames. However, the influence mechanisms of fuel staging on micromix flame heat release, combustor pressure oscillations, and pollutant emissions remain unclear. In this study, an integrated approach combining experimental and numerical simulation methods was employed. For the first time, experimental measurements were conducted to obtain the pressure oscillations, static/dynamic structural characteristics, and NOx/CO emission evolution patterns of syngas micromix flames under radial fuel staging configurations, complemented by numerical simulations to analyze low-pollutant emission mechanisms. This research will contribute to the application of fuel staging technology in micromix combustion systems, enabling better realization of stable lowNOx combustion for hydrogen-containing fuels.

The integration of CO2 capture and electrochemical CO2 reduction reaction (ECO2RR) enables low-energy conversion of CO2 from the emission end to the product end. To effectively address issues such as the consumption of products from new ammonia-based carbon capture technology and the high energy consumption of CO2 regeneration, this study prepared a Cu single-atom catalyst (SACu/CNTs) and proposed using NH4HCO3 as the electrolyte for ECO2RR. The Cu-N3 structure of the catalyst is confirmed by X-ray absorption fine structure testing. Benefiting from the double hydrolysis characteristics of NH4HCO3 solution, Faraday efficiency (FE) of 60 % for CO is achieved at -1.4 V. In-situ Raman spectroscopy confirms that the adsorption of NH4+ on the catalyst and the coverage of H+ resulted in suboptimal CO selectivity. By dynamically regulating the valence state of Cu using a pulsed potential to avoid NH4+ and H+ coverage, FE of CO is increased to 78 %. Density functional theory (DFT) calculations indicate that the eta CO of the Cu-N3V-SAC structure of the catalyst is 1.161, indicating a suitable adsorption strength for CO. The decrease in the coordination number of N enhances the adsorption strength for *COOH, the rate-determining step of the reaction shifts from CO2 -> *COOH to *CO -> CO. Using the carbon capture product NH4HCO3 as the electrolyte for ECO2RR demonstrates potential application prospects. This study provides new ideas and theoretical support for catalyst design in integrated carbon capture and utilization (ICCU).

Biomass oxy-fuel gasification can supply renewable CO-rich syngas as a potential feedstock for downstream green H2-coupled alcohol fuel synthesis while valorizing O2 co-produced by water electrolysis. This study clarifies how operating conditions, CO2/H2O gasifying agents, inherent oxygen and AAEMs regulate gas-solid product evolution during corn straw and rice husk conversion. The results show that oxy-fuel gasification suppresses tar yields below 0.25%, leaving gaseous products and residual biochar as the main carbon carriers. CO2 promotes CO formation by enhancing solid-carbon conversion and consuming amorphous/defective carbon, whereas excessive CO2 weakens CO selectivity. H2O increases H2 concentrations to 14.56% and 13.08%, but over-addition lowers CO fraction and syngas heating value. Feedstock-dependent behavior is associated with inherent oxygen speciation and surface reactivity, while K shows a stronger association with C-O site cycling than Ca under the tested conditions. These findings guide biomass oxy-fuel gasification design for green hydrogen-based fuel production.

Integrated CO2 capture and utilization requires dual-functional materials (DFMs) that remain stable under flue-gas-relevant conditions. Red mud (RM), an Fe- and Al-rich industrial waste, was used with Al to modify CaO for cyclic CO2 capture and H2-assisted RWGS conversion. After 20 cycles, CaO/Al/RM retained 64.6% of its initial CO2 capture capacity, compared with 47.9% for AcCaO, while the CO-yield decline was reduced from 58.1% to 34.8%. The modified material maintained a CO yield of 5.80 mmol·g−1 and a CO2 conversion of approximately 80%. RM-derived Al-containing phases contributed to structural stabilization, whereas redox-active FeOx species promoted CO2 conversion during H2-assisted regeneration. Under 15% H2O, the initial capture capacity increased by approximately 5%, and the capacity decay decreased from 35% to 17%. Under 6% CO2, the material retained CO2 capture and CO yields of 7.3 and 6.2 mmol·g−1, respectively, after 20 cycles. The study is expected to provide reference and technical support for the preparation of low-cost DFM and the practical application of ICCU in power plants.

The direct-fired supercritical CO2 (DFSC) cycle is a novel, efficient, low-carbon emission power generation technology. This paper reviews various DFSC cycle layouts and their performance. Energy efficiencies for gas and solid fuel layouts are 49.32–65.7% and 18.25–53.19%, respectively. The supercritical CO2 (sCO2) combustor is a key hot end component for achieving high efficiency of the DFSC cycle system and green operation. This work traces the evolution of sCO2 combustors and studies their design features, including geometry, cooling method, and nozzles. Given the two problems of CO emissions and combustion stability, a conceptual sCO2 combustor is proposed from the aspects of nozzle structure, combustion organization method, and oxidizer composition, which provides ideas and references for the future development of sCO2 combustors. Numerical combustion is significant for understanding sCO2 oxy-fuel combustion characteristics, thus assisting the combustor design. Therefore, starting from the sCO2 combustion kinetics, this paper summarizes the optimization methods of the kinetic models (chemical reactions, equation of state, thermodynamic and transport parameters, mixing rules) and compares the basic combustion characteristics with the kinetic models. On this basis, further summarizing the sCO2 turbulent combustion characteristics. Limited by the high-precision numerical simulation’s computational efficiency and cost, an effective way to study sCO2 oxy-fuel combustion and combustor design with machine learning assistance is proposed. Future research should focus on experiments and developing efficient, high-fidelity numerical simulation frameworks.

Pressurized oxy-fuel combustion is a potential carbon capture technology in coal-fired power generation. Pre-oxidation is an effective means to reduce NOx emissions during coal combustion. In this study, a pressurized horizontal furnace experimental system was used to explore the effects of pre-oxidation temperature (750-1000 degrees C), O2 concentration (0.5-10 %), gasifying agent and residence time (1-7 min) on the generation of CO, CO2, CH4 and NOx in the devolatilization stage of pulverized coal and the generation of NOx when char was burned in an O2/CO2/H2O atmosphere at 1.3 MPa. The contribution of the devolatilization the char combustion stage to NOx generation was comprehensively analyzed, and a pre-oxidation strategy suitable for pressurized oxy-fuel combustion NOx reduction was proposed. The results showed that pre-oxidation of pulverized coal at low oxygen concentration in the devolatilization stage can promote the generation of reductive CO and inhibit the generation of NOx. The NOx generation was the lowest at 2 % O2 concentration at 1.3 MPa pressure and 800 degrees C. In the combustion stage of the char obtained by pre-oxidation, the modified char obtained by 2 % O2 concentration has the least NOx generation. The NOx emission level in the whole combustion process can be controlled by increasing the reaction temperature in the pre-oxidation stage, extending the residence time as much as possible within the devolatilization degree of 80 %, and reasonably regulating the O2 in a low concentration range to increase the devolatilization degree in the pre-oxidation stage. This work provided evidence that targeted pre-oxidation under pressurized conditions synergistically suppresses NOx formation across both devolatilization and char combustion stages, advancing the design of low-NOx pressurized oxy-fuel systems.

The technology of powdered coal injection with recirculating flue gas and natural gas conditioning for reburning represents an advanced and innovative approach to enhancing the efficiency of coal powder reburning. By consuming excess oxygen in the recirculated flue gas, natural gas fosters an environment enriched with reducing agents, which stimulates the reactivity of reburning coal powder and augments its effectiveness in reducing nitrogen oxides (NO). This technology has been comprehensively investigated through experiments conducted in a segmented multi-reactor flow system, simulating conditions akin to those in industrial boilers. To achieve a high level of NO abatement, complete combustion of coal powder, and operational cost-effectiveness, a series of optimal operating parameters has been identified: the temperature in the reburning zone (T1) should be controlled at approximately 1573 K; the reburning fuel ratio (Rf) should be maintained around 20%; the excess air coefficient (λfuel) in the reburning zone should be approximately 0.228; the residence time in the reburning zone (t2) should be 0.6 s, and the burnout zone residence time (t3) should also be 0.6 s; finally, the oxygen concentration in the recirculating flue gas should be regulated to around 10%. This configuration ensures that reactive intermediates such as CO∗, OH∗, H, and CHi generated through natural gas modification enhance the physicochemical structure of coal char, thus amplifying the coal char's capacity for the chemical reduction of NO. Precise control of these parameters is expected to facilitate ultra-low NO emissions, while minimizing the consumption of costly active gases and ensuring the economic efficiency of the system.

Oxy-fuel combustion of biomass, when integrated with renewable energy sources, offers a promising pathway for producing high-value green methanol, thereby alleviating pressures related to carbon neutrality. However, fundamental kinetic data for biomass oxy-fuel combustion remain insufficient and require further validation. This study investigated the oxy-fuel combustion kinetics of typical biomass under both slow and fast heating conditions using thermogravimetric analysis and a micro fluidized-bed reactor, respectively. Kinetic results indicate that under slow-heating conditions, biochar combustion in an oxy-fuel atmosphere exhibits accelerated reaction rates. The activation energies for corn straw biochar and rice husk biochar decrease by 13.08 kJ/mol and 8.79 kJ/mol, respectively, compared to combustion in air, with corresponding reaction orders of 1.284 and 1.325. Under fast-heating conditions, the activation energies for volatile release are 74.76 kJ/mol for corn straw and 85.66 kJ/mol for rice husk. Although the trend in activation energy for biochar combustion remains consistent with that under slow heating, a more pronounced reduction is observed for rice husk biochar. Low-heating-rate kinetics capture activation energy dynamics, while high-rate data access the intrinsic reaction. This study provides a scientific foundation and critical data to support the development and application of biomass oxy-fuel combustion technology.