Gas Combustion Research Articles

Numerical simulation and optimization of gas premixing structures for tail gas incinerators

It is a common practice for chemical refinery tail gases to be treated in an incinerator and then released into the atmosphere. However, tail gas combustion is a key component in ensuring that the treatment process meets the relevant standards. In this paper, a vertical tail gas incinerator gas premixing structure design is proposed, aiming to improve the gas mixing effect. Based on the basic structure of the right-hand gas distribution pipe and the single-layer fan mixer at the throat, three new structures are proposed. The five new gas-premixing structures were combined into eight new structures. A series of numerical simulations were performed for one prototype premixed structure and five new premixed structures, respectively. The gas premixing structures were screened, evaluated, and optimized using gas mixing inhomogeneity and pressure loss as control parameters. Finally, the premixing structure with the best combination for the mixing unit was selected. This study is of great significance for improving the effectiveness of tail gas incineration in chemical refineries and protecting the ecological environment.

Industrial Decarbonization through Blended Combustion of Natural Gas and Hydrogen

The transition to cleaner energy sources, particularly in hard-to-abate industrial sectors, often requires the gradual integration of new technologies. Hydrogen, crucial for decarbonization, is explored as a fuel in blended combustions. Blending or replacing fuels impacts combustion stability and heat transfer rates due to differing densities. An extensive literature review examines blended combustion, focusing on hydrogen/methane mixtures. While industrial burners claim to accommodate up to 20% hydrogen, theoretical support is lacking. A novel thermodynamic analysis methodology is introduced, evaluating methane/hydrogen combustion using the Wobbe index. The findings highlight practical limitations beyond 25% hydrogen volume, necessitating a shift to “totally hydrogen” combustion. Blended combustion can be proposed as a medium-term strategy, acknowledging hydrogen’s limited penetration. Higher percentages require burner and infrastructure redesign.

Energy production from landfill gas, emissions and pollution indicators–Opportunities and barriers to implementing circular economy

The goal of this research was to test the air emissions resulting from landfill gas combustion in a 250-kW cogeneration unit, in the context of pollutant emission due to the produced electricity. The test results mainly revealed emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, carbon oxides, and dust. The volume of emissions of individual pollutants was compared with the emission values reported from the emission balancing database. The highest emission burdens concerned the production of one MWh of electricity for carbon dioxide 579.80 kgCO2∙MWh−1, carbon monoxide 2.57 kgCO2∙MWh−1, and nitrogen oxides 1.77 kgNOx∙MWh−1. It is worth noting that small cogeneration installations are not covered by emission standards and so they are not equipped with a device for reducing gaseous and particulate pollution. The tests revealed a difference between the actual emissions from the tested installation and the values reported to the national database. The innovation of this study is that it demonstrates the real emission burden of renewable energy in the context of sustainable development. The results can be used as input material for discussion to apply gaseous and particulate pollution reduction systems for cogeneration installations powered by landfill gas, including various types of biogases.

Experimental Investigation of Sulfur and Nitrogen Oxide Emissions and Corrosion Propensity During the Combustion of Coals and Biomass Fuels

ABSTRACT The increasing use of biomass in Indonesian coal-fired power plants, mainly through co-firing, presents challenges due to different fuel characteristics, which can affect gas emissions, ash deposition, and combustion efficiency. This study assesses flue gas emissions (SO2 and NOx) and corrosion tendencies of various biomass types and coal. The study begins with characteristic testing and ash analysis of coal and biomass samples, including proximate, ultimate, and calorific value analyses, to determine their suitability as fuels. Preliminary calculations predict flue gas emissions and ash deposit formation, followed by laboratory-scale combustion experiments using a DTF to assess flue gas and ash deposit characteristics. The results show that sulfur in biomass is converted to the gas phase up to 99%, while in coal, it is converted up to 95% at high temperatures. NOx levels are primarily affected by the nitrogen contents of the fuels; for instance, Coal-B at 0.88 wt% produces less NOx than solid recovered fuel (SRF) and refused derived fuel (RDF) with 1.73 wt% and 1.51 wt%, respectively, yet still generates higher emissions than the other three biomass types. In general, wood chips (WC), rise husk (RH), and palm kernel shell (PKS) emit 30–80% less flue gas compared to coal. However, ash deposition results indicate that PKS, SRF, and RDF exhibit corrosion tendencies due to the dominance of albite (NaAlSi3O8) in the mineral phase. Additionally, the high chlorine content in SRF (0.544 wt%) and RDF (0.224 wt%) leads to the formation of sticky ash deposits, which potentially impact heat transfer surfaces. These findings contribute to identifying suitable biomass types for both co-firing or dedicated combustion in coal-fired power plants.

Distributed Regime and Swirler Effects on Methane and Coke Oven Gas Combustion Characteristics

Distributed Regime and Swirler Effects on Methane and Coke Oven Gas Combustion Characteristics

Investigating the Impact of Steam Enhancement on Combustion in a Swirl-Assisted Jet-Stabilized Gas Turbine Combustor

Abstract A newly developed gas turbine combustor system based on the swirl-assisted jet-stabilized concept using Jet A-1 and natural gas as reference fuel is tested under wet conditions to evaluate its combustion characteristics in the presence of steam. The effect of steam injection into the gas turbine combustor under both spray and superheated liquid fuel injection conditions is studied experimentally on an atmospheric test rig. To evaluate the effect of steam injection on combustion performance, the water-to-gas ratio (WGR) is varied from 0 to 32%. With increasing WGR = 0 to 16% and at stoichiometric condition, NOx reductions of -82% to -100% were observed during Jet A-1 and natural gas combustion, respectively. It is shown that the reduction of the combustion zone temperature due to the steam acting as a heat sink is the main cause of the NOx decrease. The operating range of the burner remained fairly constant for Jet A-1 until WGR = 20%, while it decreased significantly with increasing WGR for natural gas combustion. While the effect of the WGR on CO was modest, the greatest effect of the WGR was on the heat release zone intensity at a constant air to fuel ratio. In reducing the NOx levels of Jet A-1 and natural gas combustion, both thermal and chemical effects of steam injection were observed. However, steam acting as a heat sink and lowering the flame temperature, thereby reducing the thermal NO formation rate, was the dominant factor in NOx reduction.

Fine particulate matter from burning oil and gas and neurological symptoms among oil spill cleanup workers

Fine particulate matter from burning oil and gas and neurological symptoms among oil spill cleanup workers

A comprehensive investigation on flame flickering characteristics of premixed conical flame at different inclination angles

To thoroughly investigate how the inclination angle affects the flickering of premixed conical flames, a series of experiments and simulations were carried out. Propane-air conical flames were established on a Bunsen burner, and various inclination angles were tested, resulting in a wide range of flame flickering frequency data. The findings revealed that the further the inclination angle deviates from 0°, the lower the flickering frequency. Consequently, an empirical correlation that factors in the inclination angle was developed. To gain a more comprehensive understanding of the flame flickering behavior under different gas inclination angles, researchers utilized Particle Image Velocimetry (PIV) and numerical simulation to visualize the velocity fields of a typical flame. The results demonstrated that deviated inclination angles not only alter the shear strength between the burnt gas and surrounding gas but also significantly change the flame flickering mode. These factors lead to various Kelvin-Helmholtz instability patterns and vortex shedding modes, ultimately impacting flickering frequency.

Experimental Study of Natural Gas and Hydrogen Co-Firing Characteristics Using Different Types of Single Nozzles of F-Class Practical Gas Turbine Combustors

Abstract Recent research on co-firing natural gas and hydrogen, a carbon-free clean fuel, aims to reduce greenhouse gas emissions from aging gas turbine power generation, a key energy issue. This approach can enhance old gas turbines and increase the proportion of combined cycle power plant utilization as coal-fired power plants in Korea gradually shut down. This study seeks optimal operating conditions for mixed fuels without modifying the F-class gas turbine combustor. Experiments were conducted using four different types of fuel nozzles (F-Class DLN combustors) under varying loads and co-firing rates. The test used actual machine operating conditions from 30% to 100% thermal load, with hydrogen co-fired with natural gas up to 70% at each load. OH high-speed imaging and an OH-PLIF technique analyzed flame structure and characteristics. Dynamic pressure was measured to check combustion instability, and exhaust gas emissions were evaluated for combustion characteristics. Key findings include critical co-firing rates for each nozzle based on NOx emission levels and combustion dynamics. As the hydrogen co-firing rate increased, flame length decreased, and NOx levels rose rapidly beyond 30%vol. Dynamic pressure oscillations showed no significant variations compared to natural gas combustion. This study successfully derived a characteristic operation map for a single nozzle based on the hydrogen co-firing rate.

Boosting the photocatalytic performance of swiftly produced carbon nitride: Impact of cyano group and oxygen doping within the matrix

We present a significant advancement in the synthesis of carbon nitride framework (CN) using a rapid electric bunsen burner (EBB) method, achieving notable outcomes within a mere 10-min timeframe. The resulting material, designated as U10, exhibits amplified porosity and a semi-scrolling structure with a thickness measuring at 2.1 nm. In comparison to conventionally synthesized urea-derived carbon nitride (UCN) through a box furnace, the U10 demonstrates significantly heightened photocatalytic activity in both hydrogen (H2) production and the removal of organic dye (methylene blue) from aqueous solutions. To ensure the robustness and reliability of this synthetic approach, two additional precursors were subjected to testing, and their rates of H2 production were analyzed. The exceptional photocatalytic performance of the U10 material arises from its distinctive structural attributes and the synergistic influences of oxygen doping (O-doping) and the cyano (-CΞN) functional group, which are introduced during the rapid synthesis strategy. This innovative and streamlined strategy for synthesizing CN not only conserves energy and time but also significantly reduces production costs, rendering it a feasible method for the large-scale production of carbon nitride material.

Important contributions of natural gas combustion to atmospheric nitrate aerosols in China: Insights from stable nitrogen isotopes

Important contributions of natural gas combustion to atmospheric nitrate aerosols in China: Insights from stable nitrogen isotopes

Numerical Study on Optimization of Combustion Cycle Parameters and Exhaust Gas Emissions in Marine Dual-Fuel Engines by Adjusting Ammonia Injection Phases

Decarbonizing maritime transport hinges on transitioning oil-fueled ships (98.4% of the fleet) to renewable and low-carbon fuel types. This shift is crucial for meeting the greenhouse gas (GHG) reduction targets set by the IMO and the EU, with the aim of achieving climate neutrality by 2050. Ammonia, which does not contain carbon atoms that generate CO2, is considered one of the effective solutions for decarbonization in the medium and long term. However, the concurrent increase in nitrogen oxide (NOx) emissions during the ammonia combustion cycle, subject to strict regulation by the MARPOL 73/78 convention, necessitates implementing solutions to reduce them through optimizing the combustion cycle. This publication presents a numerical study on the optimization of diesel and ammonia injection phases in a ship’s medium-speed engine, Wartsila 6L46. The study investigates the exhaust gas emissions and combustion cycle parameters through a high-pressure injection strategy. At an identified 7° CAD injection phase distance between diesel and ammonia, along with an optimal dual-fuel start of injection 10° CAD before TDC, a reduction of 47% in greenhouse gas emissions (GHG = CO2 + CH4 + N2O) was achieved compared to the diesel combustion cycle. This result aligns with the GHG reduction target set by both the IMO and the EU for 2030. Additionally, during the investigation of the thermodynamic combustion characteristics of the cycle, a comparative reduction in NOx of 4.6% was realized. This reduction is linked to the DeNOx process, where the decrease in NOx is offset by an increase in N2O. However, the optimized ammonia combustion cycle results in significant emissions of unburnt NH3, reaching 1.5 g/kWh. In summary, optimizing the combustion cycle of dual ammonia and diesel fuel is essential for achieving efficient and reliable engine performance. Balancing combustion efficiency with emission levels of greenhouse gases, unburned NH3, and NOx is crucial. For the Wartsila 6L46 marine diesel engine, the recommended injection phasing is A710/D717, with a 7° CAD between injection phases.

Numerical Investigation and Simulation of Hydrogen Blending into Natural Gas Combustion

Numerical Investigation and Simulation of Hydrogen Blending into Natural Gas Combustion

Study on radiation heat transfer characteristics of aeroengine combustion chamber

The thermal radiation of gaseous combustion products in an aero-engine combustion chamber has obvious non-ash-body characteristics. In this paper, based on the OpenFOAM platform, a numerical study on multi-field coupled turbulence-combustion-radiation radiative heat transfer was carried out for a certain type of aero-engine combustion chamber using the mean weighted sum of grey gas (WSGG) gas radiation model, which can accurately describe the non-ash characteristics of the gas. The results show that the radiation heat transfer characteristics are influenced by several factors such as equivalent ratio, combustion pressure and wall emissivity, among which the equivalent ratio is dominant. Increasing the equivalence ratio from 0.11 to 0.4 resulted in a 189% increase in average incident radiation at the combustion chamber wall and a 233% increase in average incident radiation at the exit. Increasing the equivalent ratio, combustion pressure or wall emissivity will increase the average radiation intensity in the combustion chamber and the inhomogeneity of radiation distribution at the exit of the combustion chamber. The radial radiation distribution factor (RRDF) also increases with the increase of equivalent ratio, combustion pressure and wall emissivity.

Urban sources of methane characterised by long-term eddy covariance observations in central Europe

Multiyear eddy covariance measurements of methane and carbon dioxide were performed in Innsbruck, Austria, a mid-sized European city in the Alps. Annual mean methane and carbon dioxide fluxes were on the order of 21.6 nmol/m2/s and 11.7 μmol/m2/s respectively. Methane fluxes increased significantly with decreasing temperature and showed a negligible weekend to weekday effect. Accompanying non-methane volatile organic compound (NMVOC) measurements provided additional constraints on urban methane sources during an intensive 6-week campaign in 2021. Positive matrix factorization analysis identified a unique and dominant methane source. Contributions from biomass burning and vehicle emissions were found to be small. No evidence was found for a large unknown biogenic source. A second intensive campaign in 2023 revealed that the measured ethane to methane enhancement in turbulent plumes showed a typical ratio of 5.2 ± 0.6%, close to the unburned ratio of natural gas (5%) in Austria. The analysis suggests that urban methane fluxes are likely to be dominated by end-user releases rather than natural gas leaks in the pipeline system. Long-term eddy flux observations also allowed identifying the existence of urban super-emitters, which brought area weighted methane fluxes up to 39 nmol/m2/s in 2022. On average, the 100 y global warming potential of methane emitted by natural gas combustion activities is 6% relative to the total urban CO2 flux, and ∼12% relative to CO2 emissions from the residential, commercial and public sectors in Innsbruck.

Computer simulation of heat and mass transfer processes during water vapor condensation from natural gas combustion products on smooth cylindrical tubes

Computer simulation of heat and mass transfer processes during water vapor condensation from natural gas combustion products on smooth cylindrical tubes

Modeling, optimization and control of a ceramic tunnel kiln for consistent product quality under changing production demands

This study presents a detailed physics-based model focusing on an industrial tunnel kiln under feedback control. Initially, an empirical sintering model is integrated into the kiln model to accurately predict the product outlet density, a quality-defining parameter reflecting firing process efficacy. Afterwards, the initial steady-state burner valve positions are determined using industrial temperature data. Subsequently, the interactions between gas temperatures and burner valve positions are quantified through the investigation of the Relative Gain Array. A systematic derivation of optimal set-points for different production rates is then carried out, aiming at minimizing energy consumption while meeting end-product quality specifications. The PID controllers are tuned using a dynamic optimization approach, which involves the minimization of integral criteria. Finally, a case study is conducted to evaluate the efficacy of the optimal set-points under varying production rates. The results demonstrate exceptional system response, thus indicating that firing curves should adapt to production rates for consistently producing quality products.

Suppression effects of different extinguishing agents on vent gases fires from lithium-ion batteries after thermal runaway: A comprehensive experimental and numerical study

During the thermal runaway process of lithium-ion batteries, the release of vaporized electrolyte and combustible gases can lead to the formation of a jet flame, posing a significant fire or explosion risk. In order to deal with the threat of lithium-ion battery vent gas fires to the safety of energy storage power stations, it's crucial to identify effective fire extinguishing agents for lithium-ion battery systems. This study employs a combination of experimental and numerical simulation methods to assess the suppression capabilities of CO2, N2, and HFC-227ea on vent gas/air premixed flames originating from lithium-ion batteries with various cathode materials. Laminar flame speed of vent gas/air/extinguishing agent premixed flames at specific equivalence ratios were measured using a Bunsen burner device under ambient temperature and atmospheric pressure conditions. Additionally, numerical calculations of laminar flame speed and adiabatic flame temperature were conducted using CHEMKIN-Pro, accompanied by an analysis of the chemical inhibition mechanism of HFC-227ea. The findings reveal that although HFC-227ea may slightly elevate the adiabatic flame temperature at lower equivalence ratios, its overall fire extinguishing efficacy surpasses that of CO2 and N2. These results offer valuable insights for selecting appropriate fire extinguishing agents for energy storage power stations, thereby enhancing the safety standards of energy storage systems.

Computational analysis of piston shape effects on in-cylinder gas flow, fuel-charge mixing, and combustion characteristics in a two-stroke rod-less spark ignition opposed-pistons engine

Compared with the traditional in-cylinder direct-injection spark ignition engine, the side-injection and side-spark-ignition characteristics of the two-stroke opposed-piston engine increase the ignition kernel offset and flame propagation distance. Increasing the flame propagation speed can to some extent solve the drawbacks caused by the non-central arrangement of spark plugs. The combustion chamber structure plays a crucial role in gas flow, fuel-charge mixing, and combustion characteristics. Therefore, three pistons were designed and comparatively analyzed in this study. The results show that: The pancake piston is beneficial to maintaining the intake swirl strength due to its simple and smooth spherical arc structure. The swirl strength of the pit and pit-guided piston decreases obviously, and the tumble strength can be maintained well. Compared to pancake and pit-guided pistons, the average TKE for the pit piston increased by approximately 25%, with a more concentrated distribution at the spark timing. The pancake piston exhibits the best scavenging performance, reducing the residual exhaust gas ratio by 2.1% and fresh air loss by 3.3% to the pit piston. A stable ignition core can be formed at the spark timing, but significant differences are observed in the flame propagation process for three pistons. Compared to the pit-guided piston, the pit piston has a 0.3% decrease in the indicated thermal efficiency, but a 13.1% decrease in combustion duration, which reduces knock tendency.

Numerical investigation of NO generation reaction pathway with novel embedded flue-gas internal recirculation combustion loop consisting of flue-gas and CH4-air mixture

The novel embedded flue-gas internal recirculation (FIR) combustion technology has garnered increasing attention in gas burners due to its notable advantages in combustion efficiency and ultra-low NOx emissions. In this study, we design FIR channels for a gas burner and investigate the impact of recirculation ratio (R) on temperature, combustion efficiency, concentrations of free radicals (H, O, CH), and NO concentration via Computational Fluid Dynamics (CFD) method. In addition, this paper explores and elucidates the dynamics of four NO production pathways, namely, thermal NO, prompt NO, N2O, and NNH, as well as the contributions of the four pathways to total NO. Observations indicate a constrained range of FIR recirculation ratios, specifically between 23.2 % and 35 %. The combustion efficiency of the FIR burner is 96 % and 99.8 % at R = 23.8 % and R = 35.0 %, which is superior to conventional burners. Moreover, as R increases, both pathways for NO generation from N2O and NNH are intensified as R exceeds 23.8 %. In the embedded FIR combustion system, the contribution of N2O to total NO increases from 0.23 % to 0.78 %, while the percentage of prompt NO decreases to 0.19 %. These findings provide a development direction and technical guidance for the practical implementation of the embedded FIR technology.