Combustion Research Articles

Energy and Economic Assessment of Oxy-Fuel Combustion CO2 Capture in Coal-Fired Power Plants

Oxy-fuel combustion technology replaces air with a mixture of pure O2 and recycled flue gas for coal combustion, which leads to difficulties in the waste heat recovery of flue gas in the boiler tail of coal-fired power plants. This paper proposes a new integration scheme for waste heat recovery of flue gas in coal-fired power plants with oxy-fuel combustion CO2 capture. By introducing an oxygen preheater, a recycled flue gas preheater, and a low-pressure economizer, the waste heat of flue gas is fully recovered to preheat oxygen, recycled flue gas, and feed water, respectively. The proposed scheme simultaneously ensures the safe operation of the recycled fan and improves the thermal performance of the coal-fired power plants. Compared to the air combustion configuration, the boiler’s efficiency and gross power efficiency in the oxy-fuel combustion configuration are increased by 0.42% and 1.29%, respectively. Due to power consumption for the added equipment, the net power efficiency is reduced by 10.41%. A techno-economic analysis shows that the cost of electricity for oxy-fuel combustion in coal-fired power plants has increased from USD 46.45/MWh to USD 80.18/MWh, and the cost of the CO2 avoided reaches USD 43.24/t CO2.

Progress in spontaneous ignition of hydrogen during high-pressure leakage with the considerations of pipeline storage and delivery

High-pressure pipeline storage presents a promising method for widespread and efficient hydrogen transfer. However, challenges arise in mitigating pressurized hydrogen leakage due to hydrogen embrittlement issues associated with conventional pipeline materials. Experimental findings indicate that pressurized hydrogen is prone to spontaneous combustion, even at relief pressures as low as approximately 2 MPa - well below the permissible pipeline pressure in most countries. Despite this, there remains a lack of consensus regarding the mechanism of spontaneous ignition from high-pressure hydrogen leakage, and current research in this area is deemed insufficient. This study aims to analyze and discuss the presumed mechanisms of spontaneous ignition comparatively, review the progress in the study of spontaneous ignition of hydrogen in high-pressure leakage based on diffusion ignition theory, and statistically compare and discuss the influences of significant factors existing in pipelines (e.g., macro size factors and internal structure) and/or pipe failures (e.g., rupture factors) on spontaneous ignition. It is hoped that this article will provide scholars involved in the development of hydrogen energy and the theories of spontaneous combustion with a systematic understanding of these phenomena.

A mini-review for identifying future directions in modelling heating values for sustainable waste management.

Global estimations suggest energy content within municipal solid waste (MSW) is underutilized, compromising efforts to reduce fossil CO2 emissions and missing the opportunities for pursuing circular economy in energy consumption. The energy content of the MSW, represented by heating values (HVs), is a major determinant for the suitability of incinerating the waste for energy and managing waste flows. Literature reveals limitations in traditional statistical HV modelling approaches, which assume a linear and additive relationship between physiochemical properties of MSW samples and their HVs, as well as overlook the impact of non-combustible substances in MSW mixtures on energy harvest. Artificial intelligence (AI)-based models show promise but pose challenges in interpretation based on established combustion theories. From the variable selection perspectives, using MSW physical composition categories as explanatory variables neglects intra-category variations in energy contents while applying environmental or socio-economic factors emerges to address waste composition changes as society develops. The article contributes by showing to professionals and modellers that leveraging AI technology and incorporating societal and environmental factors are meaningful directions for advancing HV prediction in waste management. These approaches promise more precise evaluations of incinerating waste for energy and enhancing sustainable waste management practices.

Effects of elevated oxygen content and temperature on the laminar burning velocity of the blast furnace gas in oxygen-enriched air condition

Oxygen-enriched air combustion holds promise as an effective method for harnessing blast furnace gas (BFG) in the steel industry. In this study, the laminar burning velocities of blast furnace gas were measured using the heat flux method under elevated oxygen mole fractions (0.3–1.0) and temperatures (303–353 K). Subsequently, the measured data were used to evaluate the GRI-Mech 3.0, Li, FFCM-1, and Konnov 2023 mechanisms. Comparisons between experimental and calculated laminar burning velocities revealed that the Konnov 2023 mechanism well predicts the experimental data at all conditions, while the predictions of the other three mechanisms deviate from the experimental data. The laminar burning velocities of blast furnace gas increased with elevated oxygen mole fraction and temperature. Interestingly, the peak of laminar burning velocity shifts from the fuel-rich side to the fuel-lean side with an increase in oxygen mole fraction, which is mainly due to the fuel-lean shift peak of adiabatic flame temperature and the higher diffusive properties of the gas mixture at fuel-rich side. The reaction CO+OH<=>CO2 + H emerges as the most significant reaction influencing laminar burning velocities. The elevated oxygen mole fraction reduces the dependence of the power exponent α on the fitted temperature range. Corresponding oxygen mole fractions for the blast furnace gas are determined to be 0.59 at φ = 0.8 and 0.93 at φ = 0.9, respectively, at which the laminar burning velocity of the BFG/O2/N2 mixture equals that of the CH4/Air mixture.

Comparison of Water- and Amine-Based Carbon Capture Processes for Air and Oxyfuel Combustion Technologies

Comparison of Water- and Amine-Based Carbon Capture Processes for Air and Oxyfuel Combustion Technologies

Experimental study on combustion characteristics of engineered bamboo considering smoldering and self-extinction

Bamboo and wood materials have the characteristics of low carbon and high strength, making them the best building material for building green buildings. Compared to traditional building materials, the easy to burn characteristic has become an obstacle to the promotion and widespread application of bamboo and wood materials, so it is urgent to study their combustion characteristics. This article investigated the combustion characteristics of engineered bamboo at different heat fluxes, taking into account the smoldering and self-extinction characteristics through cone calorimeter experiments. The combustion performance, mass loss rate, heat release rate, etc. were studied, and the self-extinction phenomenon of the specimens was explored. The results indicated that the direction of heating had a certain impact on the combustion characteristics of glued laminated bamboo (LBL), and the fire resistance of parallel strand bamboo (PSB) was better than that of LBL. When the heat flux exceeded 50 kW/m2, the color of the flame on the surface of the specimen would change from bright yellow to strong orange, which is an important sign that the flame will self-extinguish. The self-extinction of flames at different heat fluxes was caused by insufficient supply of combustible gas generated by bamboo pyrolysis, with slightly different specific reasons. The multi-layer structure of glued laminated bamboo also makes it more difficult to self-extinguish than PSB, cross-laminated timber (CLT), and solid wood is the most prone to self-extinguish. The impact of adhesive layer delamination was not considered in this experiment, and further research is needed.

An Active and Regenerable Nanometric High‐Entropy Catalyst for Efficient Propane Dehydrogenation

AbstractPropane dehydrogenation (PDH) is crucial for propylene production, but commercially employed Pt‐based catalysts face susceptibility to deactivation due to the Pt sintering during reaction and regeneration steps. Here, we report a SiO2 supported nanometric (MnCoCuZnPt) high‐entropy PDH catalyst with high activity and stability. The catalyst exhibited a super high propane conversion of 56.6 % with 94 % selectivity of propylene at 600 °C. The propylene productivity reached 68.5 molC3H6 ⋅ gPt−1 ⋅ h−1, nearly three times that of Pt/SiO2 (23.5 molC3H6 ⋅ gPt−1 ⋅ h−1) under a weight hourly space velocity of 60 h−1. In a high‐entropy nanoparticle, Pt atoms were atomically dispersed through coordination with other metals and exhibited a positive charge, thereby showcasing remarkable catalytic activity. The high‐entropy effect contributes to the catalyst a superior stability with a low deactivation constant of 0.0004 h−1 during 200 hours of reaction under the industrial gas composition at 550 °C. Such high‐entropy PDH catalyst is easy regenerated through simple air combustion of deposited coke. After the fourth consecutive regeneration cycle, satisfactory catalytic stability was observed, and the element distribution of spent catalysts almost returned to their initial state, with no detectable Pt sintering. This work provides new insights into designing active, stable, and regenerable novel PDH catalysts.

Flame dynamic insights into pollutant production characteristics of NH[formula omitted]/H[formula omitted]/air combustion during turbulent flame–wall interaction

A turbulent premixed NH3/H2/air flame with Damköhler number Da = 0.004 has been simulated using direct numerical simulations (DNS) with detailed chemistry. The flame is propagating in a fully-developed turbulent channel flow with friction Reynolds number Reτ = 313. The global and local production speeds of NO, N2O and NH3 have been analyzed. Special attention is paid on the flame dynamic insights into the pollutant production characteristics during the flame–wall, flame–turbulence and flame–flame interaction process. Finally, important findings have been concluded: (1) The unburned NH3 is reduced in the turbulent case due to the smaller quenching distance; (2) The N2O consumption speed would decrease just before flame quenching on the wall in the turbulent case, due to the thickened flame thickness, which is contradictory to the laminar case; (3) Effect of flame curvature on pollutant production speeds should be combined with the effect of flame surface density; (4) Low Damköhler number flame tends to produce more N2O and less NO, due to the more frequent flame–flame interaction events. These findings would help to better understand the pollutant production characteristics of turbulent premixed NH3/H2/air flames in lab-scale burners with strong flame–wall interactions.Novelty and Significance StatementThe novelty of this research is summarized into 3 points: (1) It is, to our knowledge the first time, pollutant production characteristics are investigated in detail for the premixed NH3/H2/air flame propagating in a fully developed turbulent boundary layer; (2) The effects of flame–wall, flame–turbulence and flame–flame interactions, the underlying reasons and controlling mechanisms are investigated in detail, which has not yet been (comprehensively) done in previous studies; (3) Novel and important findings have been concluded for the wall effects, turbulence effects (including flame curvature and surface density function effects) and flame–flame interaction effects. Some of these findings have never been reported before, but important for the comprehensive understanding of the pollutant production characteristics. It is significant because understanding the turbulence and wall effects on NO, N2O and NH3 production characteristics in the premixed NH3/H2/air flames is crucial for the future clean combustion energy system design.

Characteristics, Sources Analysis, and Environmental Impacts of VOCs Based on Photochemical Loss in Summer in Zhengzhou

To clarify the pollution characteristics and sources of atmospheric VOCs in Zhengzhou City in the summer, multi-site offline sampling and laboratory analyses of atmospheric VOCs in Zhengzhou were carried out in August 2022. The observed and initial VOC volume fraction levels, OFP, SOAFP, and sources were compared. During the study period, the average values of three-site observation and initial φ（VOCs） during the study period were （31.83 ±13.51）×10-9 and （35.92 ±15.30）×10-9,respectively. Olefins （52.5 %） and aromatic hydrocarbons （29.7 %） were the components with a higher photochemical loss rate, and the spatial variations of the observed TVOCs concentration at each site were： Zhengzhou University （ZZU） &gt; Gangli Reservoir （GLR） &gt; Jingkaiqu （JKQ）, and the concentrations of alkanes and OVOCs at each site were higher. Olefins and aromatic hydrocarbons were the components that contributed greatly to the formation of O3 and SOA. Motor vehicle sources, solvent-use sources, and industrial sources were the main contributing sources of atmospheric VOCs in Zhengzhou. Compared with the source analysis results based on the initial concentration, the contribution rates of motor vehicle sources, industrial sources, and solvent use sources were relatively high, and the contribution rates of combustion sources, plant sources, and oil and gas volatilization sources were relatively low.

Data-driven models for the prediction of H2 generation through chemical reaction and performance evaluation of on-board hydrogen fuelled sintering tube furnace

Hydrogen is emerging as a sustainable fuel for the future. In this present work, data-driven modelling tools viz. Radial Basis Function Neural Network (RBFNN) and Least Square Fit (LSF) method, are employed to determine the rate of production of H2 gas by the chemical reaction between aluminium and water in the presence of aq. NaOH. Reactions are carried out at NaOH concentrations of 1M–5M, water temperatures 303K–333K. Hydrogen gas obtained at 333K/4M is found to have a yield of ⁓88 % of the theoretical yield. The activation energy of the reaction is found to be 57.62 kJ mol−1. The fitted models are validated with experimental results for two unknown conditions. The correlation coefficient obtained for the RBFNN model is 0.999, which indicates the high reliability of the model. On-board production of H2 gas by the chemical reaction was used for heating a sintering tube furnace. The hot products of the combustion of hydrogen and air at various fuel-air ratios were used to heat the sintering tube furnace. The maximum thermal efficiency obtained for the furnace is 76.22 % at a fuel-air ratio of 1:60 corresponds to a fuel-air equivalent ratio (λ) of 0.57.

Quantitative Risk Assessment of an Oil-Gas-Hydrogen-Electricity Integrated Energy Station in China.

This paper presents a quantitative risk assessment (QRA) study of an oil-gas-hydrogen-electricity integrated energy station in China. A comprehensive assessment of the station was made in terms of consequences and risks, respectively. Consequence analysis shows that the severity of hazardous chemical leakage accidents in the station is in the order of natural gas, hydrogen, gasoline, and diesel fuel, especially in the liquefied natural gas (LNG) and compressed natural gas (CNG) storage tank areas, which may cause major accidents in the event of leakage. The results of the risk assessment showed that the individual and societal risks of the integrated oil-gas-hydrogen-electricity energy station exceeded the risk acceptance criteria. Moreover, the catastrophic rupture of LNG and CNG storage tanks is the main cause of the unacceptable risk. Additional mitigation measures for them, mainly including the installation of emergency manual shut-off valves, the installation of combustible gas detection and alarm devices, and pressure relief protection devices, can effectively reduce the risk to an acceptable level.

Energy efficiency of hydrogen production during dark fermentation

It is widely known that most of the world's energy is produced from non-renewable energy sources such as crude oil and coal. Hydrogen is an ideal fuel candidate with a high energy content and clean combustion product. Biohydrogen is an environmentally friendly, renewable biofuel with high energy density, making it a viable alternative to fossil fuels in the future. At the same time, despite the large number of articles on the intensification of both dark fermentation and anaerobic bioconversion in general, the operating costs of the proposed intensification methods are not well covered in the literature. The goal of the work was to estimate the conversion coefficient of thermal and electrical energy spent on the functioning of the process of dark fermentation of various organic wastes into the energy of produced hydrogen. A block diagram of the energy flows of the dark fermentation system and the structure of the energy consumption of the system were developed. The obtained literature and experimental data suggest that the conversion coefficient of energy into biohydrogen in the process of dark fermentation is less than 1, so to obtain 1 kWh of hydrogen it is necessary to expend more than 1 kWh of energy. At the same time, the use of a vortex layer apparatus for dark fermentation of the food waste model made it possible to increase the energy output of the process by more than 7 times, thereby bringing the values of the conversion coefficients of thermal and electrical energy closer to 1. Despite the fact that the energy efficiency of most known methods for producing hydrogen is higher than the energy efficiency of dark fermentation, it is worth noting that the raw material for producing hydrogen in the dark fermentation process is organic waste, and not high-energy fuel (natural gas, methane, coal) or water in the case of electrolysis. In addition, the use of a vortex layer apparatus for pre-treatment of the dark fermentation substrate made it possible to achieve electricity conversion coefficient values 40% higher than with water electrolysis.

Effects of Vent Size and Pressure on Hydrogen Explosion Dynamic Characteristics.

Explosion venting is an effective method to reduce the explosion damage; in order to study the mechanism of an explosion venting process in internal and external space, this paper investigates the influence of vent parameters on hydrogen-air explosion in a rectangular duct through numerical simulation. The model including the internal and external space is first constructed, and then the explosion dynamic behaviors of the full flow field are analyzed under different vent pressures and sizes. The study aims to reveal the coupling effect of the flame, pressure, and flow field on hydrogen explosion venting. The results indicate that the explosion intensity increases with the growth of the vent pressure and the reduction of the vent size. The maximum external overpressure increases to 2.6 and 2.3 times as the vent pressure increased to 10 times or vent size reduced by 90%. The flame and combustible gas mixture evolve from a mushroom cloud into a jet form as the vent size decreases, and vortexes formed at the flame front suppress flame propagation. However, the flame speed increases significantly as the flame passes the vent under the impact of larger pressure gradient, which results in a more violent turbulence intensity and secondary external explosion.

A Next-Generation Iot-Integrated Arduino System for Intelligent Home Environment Monitoring

To stay informed about home living conditions, a home environment monitoring device was developed using an Arduino platform. Utilizing the Arduino UNO hardware and an array of sensors, the device captures real-time data on indoor temperature, humidity, light levels, and the presence of combustible gases. This information is then uploaded to a monitoring platform, allowing for adjustments to the surrounding environment based on the collected data. Testing has demonstrated that the design effectively gathers and reliably uploads home environment data, meeting the requirements for remote monitoring of living conditions. The device offers several advantages, including low cost, minimal power consumption, a simple structure, and easy installation. DOI: https://doi.org/10.52783/pst.797

Theoretical Study of CH4 and CO2 Separation by IRMOFs.

Porous materials such as isoreticular metal-organic frameworks (IRMOFs) can be applied in several areas that explore the physical adsorption. An area that has gained prominence is fuel gas storage, as it provides the storage of a large amount of gas at low pressure and the purification of combustible gas due to the selectivity of the different chemical environments of its pores. IRMOFs represent an ideal study group due to their wide range of pore sizes resulting from the use of different organic ligands. In this context, exploring IRMOFs that adsorb more efficiently stands out, mainly for optimizing the ligand, pressure, and temperature. This work focused on the adsorption and separation of CH4 and CO2 using various IRMOFs. The results suggest that IRMOF-6 is the most suitable for separation and purification and that enhanced purification occurs when the temperature is reduced and the system pressure is increased. This better performance is associated with the higher adsorption energies for this MOF, with CO2 being higher than CH4, which tends to become even more evident when the system pressure increases.

Analysing temperature distributions in turbine first-stage rotor blades of a helicopter turboshaft engine

In helicopter turboshaft engines, turbine blades operate under extreme conditions. With increasing engine power, the gas temperature following the combustion chamber can reach approximately 1300 K. The turbine rotors endure significant centrifugal forces due to their high rotational speeds. Additionally, they experience thermal and aerodynamic loads from the flow of combustible gases, which non-uniformly impact the turbine blades at high temperatures. Furthermore, the mechanical properties of turbine blade materials are limited and strongly influenced by operating temperatures. This article presents a numerical investigation focusing on the temperature distribution of first-stage turbine rotor blades that do not feature internal cooling channels. The results indicate the regions of peak temperatures and evaluate rotor blade strength. Comparative analysis between theoretical and numerical calculations of blade temperature distribution reveals minor disparities: approximately 30 degrees at the blade shroud, 8 degrees at the mid-span section, and 15 degrees at the hub. These variations amount to less than 3% at the shroud, 1% at the mid-span section, and 1.5% at the hub.

The Application of the Particle Element Method in Tubular Propellant Charge Structure: Lumped Element Method and Multiple-Element Method

Due to the orderly arrangement of tubular propellant, the permeability of combustion gases is improved, which is beneficial for enhancing the safety of the combustion system. However, current internal ballistic gas-solid flow calculation methods adopt a quasi-fluid assumption, which cannot accurately account for the characteristics of long tube shapes. Additionally, tubular propellants exhibit both overall movement and parameter distribution characteristics, necessitating the decoupling of gas and solid phases. These two deficiencies in previous studies have limited the effectiveness of gas-solid flow simulations for tubular propellant. This paper proposes a numerical calculation model suitable for tubular propellant charging based on the particle element method for internal ballistic two-phase flow. Firstly, considering the overall movement characteristics of tubular propellants, the concept of blank particle elements is introduced to represent pure gas phase regions. Then, based on computational requirements, the tubular propellants are divided to form the lumped element method and the multiple-element method. The moving boundary method is used to calculate the movement process of the propellant bed particle group and is compared with experimental results to verify the applicability of the two methods in tubular propellant beds. Analysis results show that the particle element method can effectively capture changes in the flow field inside the chamber and the position of tubular propellants. The lumped element method can quickly obtain the flow field distribution characteristics inside the chamber, while the multiple-element method can capture parameter distribution characteristics at different positions of the tubular propellants while ensuring overall movement.

Insight into high-temperature fast pyrolysis characterization, product distribution and interaction effect of municipal solid waste and its components under steam-containing hydrogen-rich syngas atmosphere

This research delves into the field of fast hydropyrolysis of mixed municipal solid waste (MSW), with the goal of understanding product distribution and interactions in a hydrogen-rich condition. Through experimental investigations on MSW and its components, this study thoroughly examines the impact of pyrolysis temperature and gasification atmosphere (30 % H2+30 % CO+20 % CO2+20 % H2O) on the yields and distribution of the three-phase products. As the temperature increases, the gas yield gradually increases, while the yields of tar and char gradually decrease. The introduction of a hydrogen source increases the methane content in the combustible gas, which generally reaches its maximum at 850 °C, and promotes aromatic formation in tar, making aromatics the main component of pyrolysis oil. Notably, aromatics have the highest-octane number in gasoline. This study highlights gasification as a promising technology for converting organic waste into valuable fuel, advancing waste management and energy recovery.

Passive turbulent jet ignition of jet fuel in a rapid compression machine

Turbulent jet ignition is a promising alternative to conventional spark ignition systems to achieve rapid combustion of difficult-to-ignite mixtures. Jet ignition can facilitate combustion of lean mixtures at low pressure and temperature by ejecting hot reacting jets of unburned gases, intermediate species, and combustion products into the main chamber to accelerate overall ignition. These jets ignite the main chamber at multiple locations, reducing the time required for the main chamber charge to be consumed. The focus of this research is to gain an improved fundamental understanding of the turbulent jet ignition process of F-24 and air at low pressure and temperature conditions with lean (φ = 0.5) and stoichiometric (φ = 1.0) mixtures using 3D RANS simulations. A Rapid Compression Machine with pressure transducers in the pre-chamber and main chamber was modeled, and distinct events during the jet ignition process were determined from pressure measurements and their time derivatives of a single compression stroke. By understanding events during the jet ignition process with jet fuel, these results give insight into achieving stable combustion of heavy fuels at low pressure and temperature conditions with high levels of dilution.

Distinguishing the vertical air-staging low-NOx function of secondary air for suspension combustion within an industrial-scale coal-fired reversal grate furnace

The numerous coal-fired grate furnaces in China, which were designed to partition primary air on the grate and arrange secondary air in the freeboard for air-staging combustion, suffered from poor burnout and high NOx. However, secondary air was conventionally closed or set at marginal openings in real operations and no investigation was reported to explain why. Upon these off-design secondary-air circumstances, industrial-scale tests and modeling investigations were performed for a 75 t/h coal-fired reversal grate furnace at secondary-air ratios of 0 %, 3 %, 6 %, 10 %, and 16 %, respectively. The primary aims were to (i) uncover its combustion and NOx formation characteristics with varying secondary air and (ii) confirm whether secondary air acted on a real air-staging function in reducing NOx. Flow-field deflection and asymmetric combustion were found in the furnace, with the upward gas entirely deflecting towards the rear side. The front-half furnace was filled with a large but weak recirculation zone without effective combustion, acting on a huge dead zone to waste the furnace-space utilization. With increasing the secondary-air ratio, the upward gas deflection deteriorated continuously. Layer combustion worsened while suspension combustion first strengthened and then weakened. NOx emissions displayed an ascent-to-descent trend. Carbon in slag raised while carbon in fly ash decreased. Among the five case setups, the 0 % setting (i.e., fully closing secondary air) exhibited the lowest NOx emissions and burnout loss. Compared with the habitual 6 % setup, fully closing secondary air not only reduced NOx emissions by 22 % but also improved a little burnout. These trends meant that opening secondary air only strengthened suspension combustion for burning well fly ash while raised both NOx and total burnout loss. Secondary air thus failed to role as an air-staging function in reducing NOx.