Search Results (143)

The high levels of greenhouse gas emissions from energy-intensive industries have created an urgent need for decarbonization. As major sources of pollution, industries are increasingly being forced to reconsider the fuels they use in their processes. Interest in hydrogen combustion, particularly in high-temperature applications, has grown due to its physical properties and the absence of carbon dioxide emissions. Despite its potential, hydrogen combustion presents technical challenges, such as flame stability, burner adjustment requirements, control of nitrogen oxides (NO_x) emissions and material compatibility. This review examines the use of hydrogen as a fuel in industrial furnaces along three complementary axes. First, it analyzes combustion fundamentals, blending limits and mitigation strategies, including oxy-fuel and MILD combustion, and assesses their deployment maturity across the steel, cement, glass, ceramics, and refining and chemicals sectors, together with economic and regulatory constraints. Second, it reviews advances in Computational Fluid Dynamics (CFD) modeling of hydrogen flames, addressing turbulence-chemistry interaction, reaction kinetics, radiative heat transfer, NO_x formation and model validation. Third, it surveys camera-based diagnostics combined with Artificial Intelligence and computer vision for flame monitoring and combustion optimization. By synthesizing recent literature, the review identifies the principal knowledge gaps, notably standardized CFD validation datasets and robust monitoring under industrial conditions, providing a critical reference for researchers and industry. Full article

Natural-gas-fired boilers remain widely used for building and industrial heat, making NOx control relevant even as energy systems decarbonize. This comprehensive review synthesizes the published literature on staged combustion, flue-gas recirculation (FGR), premixed combustion, oxy-fuel combustion, humidified combustion, catalytic combustion, flameless/MILD combustion, and integrated systems. The evidence indicates that staged burners and moderate external FGR are the most mature retrofit options, whereas lean premixed combustion is generally better suited to new or deeply retrofitted small and medium boilers. Humidification coupled with waste-heat recovery can reduce NOx while increasing total heat recovery, but water management, corrosion, fouling, and auxiliary demand must be considered. Oxy-fuel/FGR systems facilitate CO₂ capture but impose substantial oxygen-production, recycle, and CO₂-conditioning requirements. Hydrogen blending widens lean operability while increasing flashback sensitivity and altering thermal-NO and NNH chemistry. Technology selection should therefore balance NOx, CO, efficiency, stability, auxiliary resources, retrofit constraints, and long-term reliability. Full article

The cement industry is one of the most challenging sectors to decarbonize due to the coexistence of high-temperature thermal demand and process-related emissions from limestone calcination. This study presents an energy and emissions assessment of cement manufacturing based on representative mass and energy balances derived from literature benchmarks and industrial operating data. Typical cement production requires 2.8–3.6 GJ of thermal energy and 80–120 kWh of electricity per tonne of final product, resulting in total emission in the range 500–850 kg CO₂/t cement, of which 55–65% originate from clinker calcination. Moving from this baseline, possible decarbonization pathways are evaluated, including energy efficiency improvements, clinker substitution through supplementary cementitious materials use of alternative fuels, electrification, hydrogen utilization and carbon capture technologies. The analysis shows that energy efficiency measures provide relatively limited reductions (10–30 kg CO₂/t cement), while alternative fuels and clinker substitution can achieve larger but still partial benefits. Hydrogen emerges as a promising option for decarbonizing the combustion-related share of emissions, with a potential reduction ranging from 50 to 200 kg CO₂/t cement, particularly when integrated with oxy-fuel combustion systems. Deep decarbonization ultimately requires carbon capture and storage (CCS), the only technology capable of addressing the substantial process emissions inherent to clinker production and use of hydrogen can be relevant too. Full article

This study investigates how O₂ concentration affects the combustion performance and kinetic response of Changji and Fushun oil shales under CO₂-based oxy-fuel atmospheres. Coupled TGA–DSC–MS analysis was performed to characterize thermal decomposition, heat release and absorption, gaseous product evolution, and apparent kinetic parameters. The results show that raising the O₂ concentration facilitates oil shale combustion. The TG–DTG and heat flow profiles move to lower-temperature regions as O₂ concentration increases. At 20 °C·min⁻¹, increasing the O₂ concentration from 35% to 100% reduced T_p1 and T_p2 from 357.3 and 519.7 °C to 331.2 and 491.5 °C for CJ oil shale, and from 352.3 and 484.0 °C to 326.6 and 429.7 °C for FS oil shale, respectively. These shifts were accompanied by decreases in ignition and burnout temperatures and an increase in the comprehensive combustion index. Fushun oil shale shows a more concentrated main mass-loss and heat-release region than Changji oil shale. It also exhibits lower ignition and burnout temperatures, indicating stronger overall combustion reactivity. By contrast, Changji oil shale displays more evident mass loss and thermal responses at high temperatures, suggesting a greater contribution from carbonate mineral decomposition in the later reaction stage. MS results further show that CO₂, H₂O, SO₂, and NO₂ release mainly occurs within 300–600 °C. Their release peaks shift toward lower temperatures as the O₂ concentration increases, indicating that oxygen-enriched atmospheres promote the oxidative conversion of organic carbon, hydrogen-containing structures, and S- and N-containing functional groups. The Vyazovkin nonlinear iso-conversional analysis provides conversion-dependent apparent activation energies rather than a single global kinetic parameter. The substantial variation in E_α with conversion highlights the overlapping and multi-stage nature of oil shale combustion. When the O₂ concentration is raised from 21% to 75%, E_α generally follows an upward trend; under pure O₂, however, it drops sharply. This non-monotonic variation suggests that O₂ concentration changes not only the combustion rate but also the dominant reaction routes at different conversion stages. These findings provide experimental support for selecting suitable oxy-fuel combustion conditions and improving the clean and efficient utilization of oil shale. Full article

This study proposes and evaluates an integrated coal-based hydrogen–electricity cogeneration concept that combines oxygen transport membrane (OTM) technology, coal partial gasification (CPG), and pressurized oxy-fuel combustion (POFC) with inherent CO₂ capture. Six system configurations, comprising a no-capture baseline, a conventional cryogenic air separation route, and four OTM-based variants differing in membrane operating mode (4-end vs. 3-end) and feed air heating strategy, are systematically compared through Aspen Plus process simulation coupled with a 4E (energy, exergy, environmental, and economic) assessment. The two leading CCS configurations, namely, Case 1 (CASU benchmark) and Case 2 (heat-integrated 4-end OTM configuration), show comparable thermodynamic performance, with overall efficiencies of approximately 50.9% and exergy efficiencies of approximately 48.6%. Their small efficiency difference falls within the propagated auxiliary load uncertainty, indicating that they should be regarded as thermodynamically comparable rather than strictly ranked by first-law efficiency. In the techno-economic assessment, Case 2 delivers the lowest credit-based levelized hydrogen cost among the CCS routes, while both allocation-based and credit-based costs are reported in the main text for comparison. Sensitivity analysis confirms that the comparative ranking is robust to single-parameter and combined adverse market perturbations, while the absolute economic viability remains contingent on hydrogen price, CO₂ credit availability, and membrane-related assumptions. Full article

Biomass oxy-fuel combustion based on circulating fluidized bed (CFB) technology is one of the important pathways to achieving carbon neutrality due to its potential in carbon capture and negative carbon emissions. Combining biomass, as a substitute for coal, with oxy-fuel combustion technology can enrich CO₂ while helping to control NOx emissions and carbon stock. In this study, a three-dimensional numerical model of a 20 t/h biomass CFB boiler was established based on the computational particle fluid dynamics (CPFD) method. Under an oxy-fuel atmosphere of 30% O₂/65% CO₂/5% H₂O, the combustion characteristics of three typical biomass fuels—corn straw, rice husk, and poplar wood—were systematically compared, with emphasis on the furnace temperature distribution and the formation and emission of CO, NO_X, and SO₂. The results show that the axial temperature profiles all exhibit a rapid increase to a peak, followed by a gradual decrease. The peak temperatures in descending order are poplar wood (1091 K), corn straw (1084 K), and rice husk (1047 K), and the differences are mainly attributed to variations in volatile content, ash content, and calorific value. CO is primarily concentrated in the dense phase zone; it increases first and then decreases along the furnace height. CO generated from poplar wood combustion has the highest concentration at the furnace outlet, while the steady-state outlet mass fraction of NO is the lowest for poplar wood. Corn straw combustion yields the highest NO emission. Overall, the carbon stock of the three fuels is very low, and total CO emission is extremely low. NO concentration is jointly regulated by fuel nitrogen content and CO reduction, while SO₂ emission is directly related to fuel sulfur content—corn straw and rice husk show significantly higher SO₂ emission than poplar wood due to their higher sulfur content. In summary, fuel characteristics play a decisive role in the temperature field and pollutant formation during oxy-fuel combustion. This study provides a theoretical basis for the fuel selection and operational optimization of biomass oxy-fuel CFB boilers. Full article

The growing global demand for energy and rising greenhouse gas emissions require effective mitigation strategies, including carbon capture and storage (CCS) technologies. This study reviews 16 widely used simulation tools, including Aspen Plus, MATLAB, Fluent, and gPROMS, for steady-state and dynamic modeling of post-combustion, pre-combustion, and oxy-fuel combustion carbon capture processes. The tools are evaluated using five criteria: chemical process simulation capability, dynamic modeling functionality, thermodynamic property management, heat transfer accuracy, and tool integration features. The results reveal distinct strengths across platforms. Aspen Plus and Aspen Plus Dynamics perform strongly in chemical process simulation and thermodynamic property modeling, reflecting their robustness in reaction modeling and property estimation. gPROMS excels in dynamic modeling, demonstrating strong capability for time-dependent and transient process analysis. MATLAB achieves the highest score in tool integration, highlighting its flexibility in coupling with optimization solvers, control systems, and external programming environments. Fluent shows strong performance in heat transfer modeling, particularly for detailed thermal analysis in oxy-fuel combustion systems. Most existing studies focus on individual carbon capture technologies rather than simulation tool capabilities. Following the PRISMA 2020 guidelines, a systematic search of Scopus yielded 53 peer-reviewed papers on CCS simulation, which were analyzed to identify dominant tools and inform the AHP-based evaluation. This work addresses that gap by clarifying tool-specific advantages, supporting informed model selection to improve the efficiency and sustainability of CCS process design. Full article

To elucidate the combustion behavior and molecular-scale reaction mechanisms of Fushun oil shale kerogen under oxy-fuel atmospheres, ReaxFF molecular dynamics simulations were performed based on a previously constructed kerogen model. Five reaction systems were established: 21% O₂/79% N₂, 21% O₂/79% CO₂, 35% O₂/65% CO₂, 55% O₂/45% CO₂, and 75% O₂/25% CO₂. Under programmed heating, the evolution of chemical bonds, gaseous products, char, tar and gas transformation, and system potential energy was systematically analyzed. The results show that, at the same O₂ concentration, CO₂ delays low-temperature oxidation, shifting C–C and C–H bond cleavage and O₂ consumption to higher temperatures. At elevated temperatures, however, CO₂-related pathways promote carbon skeleton fragmentation and CO formation. Increasing O₂ concentration from 21% to 75% advances O₂ participation and H₂O formation, suppresses low-temperature CO accumulation, accelerates char consumption, and drives the system toward complete oxidation dominated by small-molecule gases. Potential energy analysis further indicates that higher O₂ concentrations advance the intense exothermic oxidation stage. A four-stage oxy-fuel combustion mechanism is proposed, providing molecular-level insight into the coupled effects of CO₂ and O₂ concentration. Full article

The rapid increase in atmospheric ${\mathrm{CO}}_2$ concentration has made carbon capture an essential strategy for mitigating climate change. This review systematically summarizes ${\mathrm{CO}}_2$ capture technologies following the complete process chain. First, three major routes based on combustion stages are introduced: pre-combustion (e.g., coal gasification, biomass co-firing), combustion-based (oxy-fuel combustion and chemical looping combustion), and post-combustion capture. For post-combustion capture, which is the most widely applicable to existing emission sources, three core separation methods are further elaborated: absorption (amine blends, ionic liquids, deep eutectic solvents), adsorption (zeolites, activated carbon, MOFs, COFs, solid amine sorbents), and membrane separation (polymeric, inorganic, and mixed matrix membranes). Key strategies for performance enhancement—such as functionalization, pore engineering, and composite systems—are highlighted. Despite significant advances, large-scale deployment remains challenged by high costs, high energy consumption, and inadequate material stability. Future research should prioritize low-cost, energy-efficient, and robust capture materials and processes to enable net-zero and negative carbon emissions. Full article

The use of renewable synthetic fuels is a suitable alternative for combustion-based systems. Their implementation can reduce pollutant emissions such as soot, CO and CO₂, but ${\mathrm{NO}}_{\mathrm{x}}$ remains difficult to abate. The objective of this study is to evaluate the combination of Oxymethylene Ether-3 (OME₃) with the oxy-fuel concept, hence operating without N₂ and minimizing nitrogen oxides formation. For this purpose, advanced numerical simulations were used to investigate the effects of this strategy on combustion thermodynamics, efficiencies, and exhaust products. This model was adapted for the OME₃ use, obtaining a reduction in soot production due to the fuel characteristics, but an increment of ${\mathrm{NO}}_{\mathrm{x}}$ emission. To overcome this issue, the oxy-fuel concept was implemented to remove N₂ from the combustion process. The numerical analysis provides insights into combustion performance to enhance the comprehension of the factors responsible for emission reductions. Preliminary results have shown the feasibility to eliminate NO_x while maintaining a near-zero soot production. Further evaluations pointed out a reduction of 90% and 30% of CO and HC, respectively, with a slight improvement (1%) of the combustion efficiency (98%) and Gross Indicated Efficiency (GIE) (36%). Overall, the present study demonstrates the feasibility of the concept and highlights its potential for further optimization and experimental validation. Full article

Oxy-fuel combustion is a near-zero emission technology that utilizes high-concentration O₂ in place of air, combined with recycled flue gas, to achieve efficient combustion and enable effective CO₂ capture. In this study, air (21% O₂/79% N₂) was used as the control atmosphere, and rice straw combustion experiments were conducted using thermogravimetric analysis and differential scanning calorimetry and differential scanning calorimetry coupled with mass spectrometry (TG-MS) at heating rates of 10, 20, and 30 °C/min under oxy-fuel conditions of 30% O₂/70% CO₂, 50% O₂/50% CO₂, and 70% O₂/30%CO₂. The combustion behavior, pollutant emissions, reaction kinetics, and underlying mechanisms were systematically evaluated. The results show that CO₂ in oxy-fuel atmospheres exhibits a higher thermal inertia, due to its greater density and specific heat capacity, thereby enhancing flame stability. Oxy-fuel atmospheres reduce the ignition temperature (Tᵢ) and burnout temperature (T_f), shorten the combustion duration, shift DTG and DSC peaks to lower temperatures, and result in sharper peaks along with an increased ignition index (Cᵢ), burnout index (C_b), and comprehensive combustion index (S). Mass spectrometry (MS) analysis reveals that oxy-fuel atmospheres combined with heating rates of 20–30 °C/min suppress O₂ diffusion and thermal NO formation, reducing NO_x emissions by over 75% and simultaneously inhibiting the release of SO₂ and COS. Kinetic analysis using the FWO and Friedman methods shows that the activation energy decreases from 210.5 kJ/mol and 219.1 kJ/mol under air conditions to 110.5 kJ/mol and 114.6 kJ/mol in oxy-fuel atmospheres, representing a reduction in reaction barriers of 47.5% and 47.7%, respectively. The reaction mechanisms were identified as three-dimensional diffusion-controlled processes at heating rates of 20–30 °C/min, and random nucleation followed by growth under high O₂ concentration conditions at a heating rate of 30 °C/min. Optimizing the combustion atmosphere and heating rate enhances the rice straw combustion efficiency and reduces pollutant emissions, thereby providing theoretical support for its clean and efficient utilization. Full article

To address global carbon reduction demands, oxy-fuel combustion in circulating fluidized beds (oxy-CFB) has emerged as a highly promising carbon capture technology, offering extensive fuel flexibility and facilitating bioenergy with carbon capture and storage (BECCS). However, its commercialization is hindered by significant energy penalties and complex scale-up challenges. This review comprehensively analyzes the fundamental multiphase mechanisms, heat transfer behaviors, and multi-pollutant emission characteristics of oxy-CFB systems, drawing upon multiscale modeling advancements and operational data from pilot to 30 MW_th industrial demonstrations. Replacing air with an O₂/CO₂/H₂O mixture fundamentally alters gas–solid hydrodynamics and char conversion pathways, necessitating active fluidization state re-specification. Despite shifting optimal desulfurization temperatures and introducing recarbonation risks, the technology demonstrates inherent advantages in synergistic pollutant control, including the complete elimination of thermal NO_x. While atmospheric oxy-CFB is technically viable, transitioning to pressurized operation is critical to minimizing system efficiency penalties. Furthermore, integrating oxygen carrier-aided combustion (OCAC) and developing advanced predictive control strategies are essential to managing multi-module thermal inertia and enabling rapid dynamic responsiveness for modern power grids. Full article

In this study, thermogravimetric analysis was employed to investigate the non-isothermal combustion behavior and kinetic characteristics of poplar biomass under air and oxy-fuel (O₂/CO₂) atmospheres. The effects of heating rate and oxygen concentration on combustion performance, gaseous emissions, and kinetic parameters were systematically analyzed. Results show that poplar biomass combustion consists of four distinct stages: moisture evaporation, devolatilization with volatile oxidation, char and fixed carbon oxidation, and final burnout. Increasing the heating rate intensifies the combustion process, shifting characteristic temperatures to higher values and significantly enhancing the comprehensive combustion index. Compared with air combustion, oxy-fuel conditions reduce ignition temperature and the temperature corresponding to the maximum combustion rate, leading to an earlier ignition and a more concentrated reaction interval. Higher oxygen concentrations further improve overall combustion performance and promote more complete carbon conversion. Gas emission analysis indicates that oxy-fuel combustion effectively suppresses NO₂ and SO₂ formation, demonstrating notable emission-reduction potential. Kinetic analysis using the Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa isoconversional methods shows that the activation energy varies with conversion degree and is generally higher under oxy-fuel atmospheres than in air. Overall, oxy-fuel combustion enhances biomass reactivity while achieving coordinated emission control through increased oxygen partial pressure and improved heat and mass transfer, supporting its practical application in biomass energy systems. Full article

Hydrogen is a promising clean energy vector capable of decarbonizing future energy systems. This study explores blue hydrogen production via a modified autothermal reforming process, integrated with oxy-fuel combustion and carbon capture technologies. The process achieves approximately 99.8% carbon dioxide capture while co-generating electricity, improving both environmental and economic performance. A detailed techno-economic analysis for Alberta, Canada, shows that hydrogen can be produced at a competitive cost of $1.70 per kilogram, depending on natural gas supply pressure, with CO₂ emissions of just 3.82 kg-CO₂/kg-H₂, meeting stringent international low-carbon thresholds. Key parameters like natural gas supply pressure, oxygen-to-methane ratio, and turbine pressure ratio were optimized for flexibility, efficiency, and cost-effectiveness. Sensitivity analysis identified financial, policy, and grid decarbonization factors as key drivers of production costs. Compared to other methods, this process stands out for its superior environmental and economic outcomes, particularly in regions with ample natural gas and carbon capture infrastructure. The study underscores the importance of process innovation in advancing sustainable blue hydrogen. Full article

The production of high-performance glass fibers relies critically on achieving a homogeneous melt with a specific thermal history, which is directly determined by the precise control and optimization of the melting equipment. To enhance the melting efficiency and material quality, this study investigates the optimization of the electric assistance system in a 200 t/d oxygen-enriched glass fiber melting furnace. By integrating CFD (Computational Fluid Dynamics) simulation techniques, a furnace model encompassing both the combustion zone and molten glass phase is developed. The study focuses on the impact of an oxy-fuel combustion + electric assistance system on the glass melting process. The influence of different input voltages on the furnace is analyzed through temperature, velocity, and flow fields. Glass melting efficiency and quality are evaluated using residence time, melting factor, and homogenization factor, considering both the residence time of molten glass and quality factors. The results indicate that a voltage scheme with the highest input voltage at the furnace inlet, combined with a relatively high voltage at the furnace outlet, is optimal, leading to the superior glass melting quality and the longest furnace service lifespan. Full article