Effect Of Oxygen Enrichment Research Articles

Numerical modeling for structure and NOx formation characteristics of oxygen-enriched syngas turbulent non-premixed jet flames

The present study numerically investigated the effect of oxygen enrichment on the precise structure and NOx formation characteristics of turbulent syngas non-premixed flames. The turbulence-chemistry interactions were represented by a Lagrangian flamelet model. In context with the Lagrangian flamelet model, the NO concentration was obtained directly from the flamelet calculation based on full NOx chemistry, with radiative heat loss being accounted for through the flamelet energy equation. Computations were performed for three different syngas compositions with a designated nitrogen dilution level. Numerical results indicated that, for the CO-rich composition with the lowest LHV yielding the highest scalar dissipation rate and shortest flight time, the flame structure was dominantly influenced by turbulence-chemistry interactions. On the other hand, with regard to the H2-rich composition with the highest LHV yielding the lowest injection velocity and longest flight time, the flame structure was strongly influenced by radiative cooling. The peak NO level was remarkably elevated by increased oxygen level due to the elevated temperature of the oxygen-enriched flame. In the enhanced oxygen level (30%), the H2-rich case produced the highest NO level due to a higher temperature and longer residence time within the hot flame zone, while the CO-rich case yielded the lowest NO level due to a lower temperature and shorter residence time. It was also found that, by enhancing the oxygen level, contributions of NNH and N2O to total NO emission rapidly decreased while the contributions of the thermal NO path were progressively dominant for all cases.

Modelling and Analysis of Oxygen Enrichment to Hot Stoves

The paper presents some research work on applying the oxygen enrichment technique to hot stoves that was carried out in one European RFCS project. In the presented work, both theoretical and practical work was studied. A dynamic model was used to investigate the effects of oxygen enrichment on hot stoves’ performance under the condition that only blast furnace gas was used as the fuel gas. The modelling results showed that SOE will enhance the combustion process in hot stoves by increasing hot blast temperature and shortening the on-gas time, which were further verified by industrial trials performed at an iron-making plant. In addition, CFD modelling was performed by simulating different oxygen levels and lance positions at the burner to avoid the hot spot formation during the combustion.

Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

Effects of Oxygen Enrichment on Combustion Instability under Super Lean and High EGR Conditions

Effects of Oxygen Enrichment on Combustion Instability under Super Lean and High EGR Conditions

Combined effect of oxygen enrichment and exhaust gas recirculation on the performance and emissions of a diesel engine fueled with biofuel blends

ABSTRACTThe present study investigates the combined effect of oxygen enrichment and exhaust gas recirculation (EGR) on the performance and emission characteristics of a cardanol biofuel blend, namely B20M10 (20% cardanol, 70% diesel and 10% methanol by volume). The tests are conducted on a four-stroke single-cylinder diesel engine at different loading conditions. Intake air is enriched by 7% of the atmospheric oxygen concentration and exhaust gas is recirculated by 10, 15 and 20% of the total intake charge. Research results reveal that the oxides of nitrogen (NOx) emission decreases as the percentage of EGR increases from 0 to 20%. The results shows 11.8% lower NOx B20M10 at 7% oxygen enrichment and 20% EGR when compared to B20M10 without oxygen enrichment and 0% EGR. Higher carbon monoxide (CO), unburnt hydrocarbon (HC) and smoke, and lower brake thermal efficiency are obtained for higher EGR percentages. From the studies it can be stated that B20M10 cardanol biofuel blend with 7% intake air oxygen enrichment and 15% EGR shows better reduction in NOx emissions with minimum penalty of performance and other emission characteristics.

Numerical simulation and optimization of an industrial fluid catalytic cracking regenerator

Fluid catalytic cracking (FCC) is one of the most important conversion processes in petroleum refineries. FCC regenerator is a key part of an FCC unit to recover the solid catalyst reactivity by burning off the deposited coke on the catalyst. In this paper, a three-dimensional multi-phase, multi-species reacting flow computational fluid dynamics (CFD) model was established to simulate the flow and the reactions inside an FCC regenerator. The Euler-Euler approach, where the two phases (gas and solid) are considered to be continuous and fully inter-penetrating, is employed. A modified drag force model was applied on the CFD model with appropriate influential cluster diameters of particle grouping phenomenon. The developed CFD model was validated by using plant data. With the validated CFD model, the flow characteristics and the inner-phase and inter-phase reactions were studied. The results showed that the effect of oxygen enrichment on the catalysts recovery efficiency was limited when the oxygen enrichment exceeded 5%.

Oxygen enriched combustion and co-combustion of lignites and biomass in a 30 kWth circulating fluidized bed

Oxygen enriched combustion is a promising retrofitting option for existing power plants to improve CO2 capture. In this study, the effect of oxygen enrichment of air as oxidant was investigated with a 30kWth fluidized bed combustor. Tests were conducted with two different Turkish lignites, one biomass and their blends. Biomass share was increased up to 20%. The oxygen concentration in the oxidant was kept between 21 and 30%.Oxygen enrichment supports combustion in all cases. Biomass addition to lignites appears to have an increasing synergetic effect on combustion as the oxygen enrichment and biomass portion in the mix increases. It was found that oxygen enrichment increases NO and SO2 formation in all cases. As the biomass share increases NO emissions increase in all oxygen cases while the opposite is true for SO2 emissions.

Effects of oxygen enrichment on laminar burning velocities and Markstein lengths of CH4/O2/N2 flames at elevated pressures

Laminar burning velocities and Markstein lengths of CH4/O2/N2 mixtures were measured in a constant volume combustion chamber over a wide range of O2 contents and equivalence ratios at elevated pressures. The laminar burning velocities were extracted using an accurate nonlinear methodology with properly chosen flame radii to reduce the systematic uncertainty. Chemical kinetic simulation was conducted using three different chemical reaction mechanisms with the PREMIX code. In general, numerical results agree well with the experimental data under most conditions. However, GRI Mech 3.0 and Aramco Mech 1.3 slightly under-predict the laminar burning velocities at high O2 content, and Han Mech overestimates the experimental data at low O2 content. With oxygen enrichment, the laminar burning velocity is dramatically enhanced by thermal effect, and diffusion effect makes a small positive contribution, while kinetic effect is negligible. Furthermore, Markstein length decreases with the oxygen enrichment ratio because of the combined effects of the density ratio and flame thickness. Moreover, for high O2 content mixtures, the flame becomes unstable mainly due to the effect of hydrodynamic instability.

The effect of oxygen enrichment on soot formation and thermal radiation in turbulent, non-premixed methane flames

Non-premixed oxy-fuel combustion of natural gas is used in industrial applications where high-intensity heat is required, such as glass manufacturing and metal forging and shaping. In these applications, the high flame temperatures achieved by oxy-fuel combustion increase radiative heat transfer to the surfaces of interest and soot formation within the flame is desired for further augmentation of radiation. However, the high cost of cryogenic air separation has limited the penetration of oxy-fuel combustion technologies. New approaches to air separation are being developed that may reduce oxygen production costs, but only for intermediate levels of oxygen enrichment of air. To determine the influence of oxygen enrichment on soot formation and radiation, we developed a non-premixed coannular burner in which oxygen concentrations and oxidizer flow rates can be independently varied, to distinguish the effects of turbulent mixing intensity from oxygen enrichment on soot formation and flame radiation. Local radiation intensities, soot concentrations, and soot temperatures have been measured using a thin-film thermopile, planar laser-induced incandescence (LII), and two-color imaging pyrometry, respectively. The measurements show that soot formation increases as the oxygen concentration decreases from 100% to 50%, helping to moderate a decrease in overall flame radiation. An increase in turbulence intensity has a marked effect on flame height, soot formation and thermal radiation, leading to decreases in all of these. The soot temperature decreases with a decrease in the oxygen concentration and increases with an increase in turbulent mixing intensity. Overall, the results suggest that properly designed oxygen-enriched burners that enhance soot formation for intermediate levels of oxygen purity may be able to achieve thermal radiation intensities as high as 85% of traditional oxy-fuel burners utilizing high-purity oxygen.

Effects of oxidizer flexibility and bluff-body blockage ratio on flammability limits of diffusion flames

Concerns about global warming have encouraged the interest in hydrocarbon combustion techniques that allow easy capture of carbon dioxide. One technique for achieving this objective is through the use of pure oxygen instead of air for combustion or what is called oxy-combustion carbon capture technology. The main goal of the manuscript is to study flammability limits, visual flame appearance and exhaust emissions of diffusion flame stabilized over a bluff body over ranges of operating and design conditions. The operating conditions include flow Reynolds number, equivalence ratio and oxidizer composition. The design parameter considers the change of blockage ratio (BR) of the bluff body namely, BR=0.36, 0.5, 0.67 and 0.82. Based on this, three sets of experiments were performed utilizing compressed natural gas (CNG) as a fuel to be burned with three different oxidizers including air, oxygen-enriched-air and oxy-fuel mixtures (O2 plus CO2 with a controlled oxygen fractions, OF). The three sets of experiments were performed to identify ranges for stable flame operation considering different oxidizers under different operating conditions. Stability limits, visual flame appearance and extinction limits of these flames are quantified and analyzed. Furthermore, three different regions were observed; precisely, jet flames, central-jet dominated flames and recirculation zone flames, depending on the ratio between oxidizer and fuel momentum. The flame color changed from yellow for air combustion, to bright white for oxygen-enriched-air combustion and finally to blue with yellow tips for oxy-combustion. The flame length was the highest for air combustion, then lower for oxy-combustion and the lowest for oxygen-enriched-air combustion. This was attributed to the effect of oxygen-enrichment which results in increase in the flame speed making flame length shorter. For the sake of comparison, the flammability limits of the three sets were reported and the results revealed that oxygen-enriched-air-flames have higher stability than air-flames and oxy-flames, respectively.

Combined Effect of Oxygen Enrichment and Emulsification Techniques on Performance, Emission and Combustion of a WCO Based CI Engine

Combined Effect of Oxygen Enrichment and Emulsification Techniques on Performance, Emission and Combustion of a WCO Based CI Engine

Combined Effect of Oxygen Enrichment and Dual Fueling on the Performance Behavior of a CI Engine Fueled With Pyro Oil–Diesel Blend as Fuel

This paper aims at studying the combined effect of oxygen enrichment and dual fueling on performance, emission, and combustion characteristics of a mono cylinder diesel engine using a blend of cashew nut shell pyro oil (CSO) and conventional diesel oil (called BD—base diesel) as fuel. Experiments were initially conducted using 100% BD as fuel at variable power output conditions. Subsequently, experiments were repeated with CSO40D60 (blend of 40% of CSO and 60% of BD by volume) at different power outputs. In the third phase, the engine was run with oxygen enrichment of 24% by volume in the intake air using CSO40D60 as fuel. Finally, the engine was operated in dual fuel mode of operation with the oxygen concentrations of 24% using CSO40D60 as pilot fuel and ethanol as the primary inducted fuel. Ethanol induction was made up to the maximum possible limit until misfire or knock. The brake thermal efficiency (BTE) was found as 25% with CSO40D60 29.5% and 30.5% with BD at the rated power output of 3.7 kW. The smoke number was noted as 55 filter smoke number (FSN) and 40 FSN, respectively, with CSO40D60 and BD. Hydrocarbon (HC) and carbon monoxide (CO) emissions were found to be higher with CSO40D60 as compared to BD. Ignition delay (ID) and combustion duration (CD) were also noted to be higher with CSO40D60 at all power outputs. Combined oxygen enrichment and ethanol induction sufficiently increased the BTE using CSO40D60 as fuel at all power outputs. At peak power output, the BTE was noted as 34.5%. The lowest smoke number of 36 FSN was found for 24% of oxygen with 34.3% of ethanol energy share at peak power output with CSO40D60 as fuel, whereas it was 40 FSN with BD and 55 FSN with CSO40D60 for 21% of oxygen. Significant improvement in heat release rates was observed by combining ethanol induction and oxygen enrichment techniques using CSO40D60 as fuel. Overall, it is concluded that by combining oxygen enrichment and ethanol induction superior performance and reduced emissions can be achieved at all power outputs using CSO40D60 as fuel.

Numerical study on the effects of oxygen enrichment on methane/air flames

In the study, we numerically simulated premixed laminar methane/air flames enriched by oxygen at flame equivalence ratios of 0.7, 1.0 and 1.2, and over a wide range of enrichment ratios from 0 to 0.79. The effects of oxygen enrichment on flame characteristics were studied through comparing global thermal properties, NO production and flame kinetics. With the addition of oxygen, the flame temperature gradient, inner layer temperature, and average heat release rate are consistently increased, and the flame thickness decreases. According to the predictions of NO emission, a small amount of oxygen addition increased NO production, whereas a large quantity of oxygen decreased NO emission. Moreover, we explored the kinetic effect of oxygen enrichment on flame reaction routes via flame kinetic analyses. The effect of oxygen enrichment was inconspicuous in the pyrolysis routes from CH4 to CH3, in which the related reactions were promoted coequally. Significant differences were found in the pathways of CH3 oxidation, in which the reactions related to the consumption of O, OH, and H had been promoted significantly. Based on the analyses of the variations of reaction progress rate, we found the primary affecting routes of oxygen on methane/air flame. R38 and R84 played central roles in methane oxidation and they were promoted by oxygen addition and consequently contributed to the acceleration of the global reaction of enriched flames.

Effect of Oxygen Enrichment on Laminar Burning Velocity of Methanol and Ethanol – Oxygen – Nitrogen Mixtures

The effect of oxygen enrichment on the laminar flames speed for (methanol and ethanol – oxygen – nitrogen) premixed mixtures have been detected practically. Measurement system is designed to measure the laminar flame speed using a tube – method and optical technique (photodiode). Where the flame front position had been located by photodiode. The laminar flame speed measured at atmospheric pressure,301K initial temperature, three level of oxygen concentration (0.21, 0.23 & 0.25), and equivalence ratios from 0.7 to 1.2. All experimental work was carried out at constant pressure in order to use density ratio method for the calculation of laminar burning velocity. Also the dependencies of flame thickness and Zel’dovich number on oxygen enrichment and equivalence ratio were explored. Using Oxygen enrichment techniques increases the laminar burning velocity and decreasing the flame thickness and Zel’dovich number. The maximum value of burning velocity occurs at equivalence ratio (1.1) at all Oxygen level. While the maximum increasing percentage in laminar burning velocity occurs at equivalence ratio (0.7) by (60.5% and 87.7%) for methanol and ethanol respectively. Oxygen enrichment, mixture strength and type of alcohols dependence of burning velocity is represented by empirical relation. Validation of the present work results is approved by comparison with the available published data for (methanol and ethanol – air) mixtures, and show good agreement between them, which indicates that the measurements and the calculations employed in the present work are successful and precise.

Thermal Behavior and Hydrogen Production of Methanol Autothermal Reforming Performed Using Oxygen Enrichment and Cu/ZnO/Al2O3/Cr2O3/CeO2 Catalyst

A fixed-bed reactor designed for the autothermal reforming (ATR) of methanol under adiabatic conditions was constructed to experimentally determine the profile of temperature and catalyst activity generated using the Cu/ZnO/Al2O3/Cr2O3/CeO2 catalyst. The effect of oxygen enrichment in this experiment was investigated, and the experimental results showed that an increase in oxygen concentration correlated with an increase in the temperature of the catalytic bed; by contrast, this increase in oxygen concentration resulted in a reduction of the startup time of the catalyst. Moreover, the reaction temperature was determined to vary with the position within the catalytic fixed bed. © 2015 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

The influence of flue gas recirculation on oxy-oil combustion in an existing furnace

Oxy-fuel combustion has received increasing attention as one of the major solutions for CO2 capture. This study aimed to obtain a better understanding on the oxy-oil firing process and to gain experience handling flue gas recirculation. A 300 kWth multi-fuel combustion test furnace at National Cheng-Kung University in Tainan, Taiwan was chosen as the experimental facility. This experimental study had successfully converted a conventional air-fired furnace to operate on oxy-fuel firing with various operating conditions. Oxygen-enriched combustion and oxy-fuel combustion tests were conducted. The effects of oxygen enrichment, flue gas recirculation, fuel type, and thermal loading on the operational characteristics of the furnace such as temperature distribution, pressure variation, and emission characteristics were examined and discussed. Several concerns about a conventional air-fired furnace adapted for oxy-fuel combustion were scrutinized, including optimization of flue gas recirculation for better combustion efficiency, higher SO2 concentration in the flue gas under oxy-fuel operation, and air leakage coming from negative pressure operation. These findings provided valuable data to improve the performance of oxy-fuel combustion and to allow better conceptual designs in future development.

STUDY OF EFFECTIVENESS OF USE OF OXYGEN FOR HEATING OF HIGH-TEMPERATURE LINING HEATING STANDS OF STEEL-TEEMING LADLES

The effect of oxygen enrichment of blast on technical and economic parameters of operation of the stand and quality of lining heating has been studied on the base of the comprehensively determined mathematic model of thermal panels for heating of steel ladle linings. The enrichment of the blast with oxygen leads to saving of natural gas and increases efficiency.

Effect of Oxygen Enrichment of Intake Air on the Performance and Emission of Single Cylinder CI Engine Fueled with Cardanol Blends

In this study, the effect of intake air enrichment on the performance and emission characteristics of a single-cylinder direct-injection diesel engine fueled with non edible oil namely Cardanol—diesel-methanol blend (B20M10) are investigated. With increase of intake air oxygen concentration, CO and HC decreased while brake thermal efficiency and NOx considerably increased. The maximum Brake Thermal Efficiency of 33.98% is obtained for B20M10 with 7% oxygen enrichment of intake air. Maximum NOx emission 20% is obtained for B20M10 with 7% oxygen enrichment for the full load condition. Decreases of 20% and 14.5% in CO emission are obtained for B20M10, over B20M10 with 7% oxygen enrichment, where as 76.8% and 74% decrease in hydrocarbon emission is obtained over B20M10 without oxygen enrichment.

Effect of Oxygen Enrichment on Mineral Texture in Sintered Ore with Gaseous Fuel Injection

Effect of Oxygen Enrichment on Mineral Texture in Sintered Ore with Gaseous Fuel Injection

気体燃料吹込みでの焼結鉱組織に及ぼす酸素富化の影響

気体燃料吹込みでの焼結鉱組織に及ぼす酸素富化の影響