Methane Percentage Research Articles

English

The purpose of this study is to evaluate the biogas productivity potential of residues of the transformation of halieutics products. Experiments were conducted in two digesters of PUXIN model of 20 m3, where the temperature is 35°C. Multirae analyser was used to know the composition of biogas produced. A gas counter was also used for counting the amount of biogas produced during the experiment. There was also a balloon of storage of 10 m3 downstream from the digester, for storing the biogas produced. The total volume with 2970 kg of substrate was 9.67 m3. The maximum daily volume of produced biogas was 1.561 m3 at the 5th day after the installation of the gas counter. The potential biogas is then, 3.25 m3/T of wastes. While the potential biogas found in earlier study is 53 m3/T of wastes. For analyses of produced biogas, maximum percentages of methane, oxygen, carbon monoxide and hydrogen sulfide are, respectively 91%, 20.9%, 196 ppm and 44.7 ppm. Method of cooking halieutics products with biogas takes much time than that using wood of heating.   Key words: Substrate, biogas, potential biogas, digester.

Anaerobic membrane reactor: Biomethane from chicken manure and high-quality effluent

Chicken manure was treated in a pilot scale reactor anaerobic membrane bioreactor constituted by a completely mixed reactor combined with an ultrafiltration tube-shaped membrane in a side-stream configuration. The process operated under mesophilic condition and the inhibition of high concentration of ammonia was avoided using an ammonia stripping system. The experimental plan included a preliminary evaluation, where organic loading rates between 1.0 and 7.6 kgVS/m3/day were tested. The organic load higher than 4 kgVS/m3/d caused the accumulation of volatile fatty acids and process instability. Application of the ammonia stripping was also evaluated. The best performances were achieved using a retention time of 21 days, an organic load between 1.4 and 2.0 kgVS/m3/d, and the recirculation of stripped permeate. Reduction of the ammonia permeate content by 90% through stripping and utilization of a mixture of chicken manure/water/permeate in a ratio of 0.22/0.72/0.72 w/w led to a specific biogas production of 0.59 m3biogas/kgVS and methane content of 66–69%. The ammonia thus removed can be recovered by sulphuric acid treatment as ammonium sulphate, which can be used as a fertilizer. The proposed configuration allowed satisfactory biogas production with appropriate methane percentages, recovery of ammonium sulphate, and a high-quality effluent.

Improving the energy balance of ethanol industry with methane production from vinasse and molasses in two-stage anaerobic reactors

Abstract Thermophilic anaerobic digestion is a viable option for processing sugarcane vinasse that recovers energy in the form of methane. However, restarting real-scale vinasse-treating reactors, at the resumption of the sugarcane harvest season, can lead to difficulties, making it desirable to keep them in continuous operation in the off-season. Thus, was evaluated the thermophilic anaerobic conversion of sugarcane vinasse in a two-stage upflow anaerobic sludge blanket (UASB) reactor (reactors R1 and R2), employing sugarcane molasses in the off-season for methane production, followed again by vinasse in the following harvest season. UASB reactor R2 yielded a higher methane percentage in biogas and higher volumetric methane production rates and methane yield than R1, accounting for a 58% increase in energy production in the two-stage system compared to the single-stage system using vinasse. It is observed that the molasses is an important source of carbon for the energy production using the thermophilic UASB reactors (18.01 MJ L−1 molasses), compared to alcoholic fermentation (8.30 MJ L−1 molasses). The methane produced in the reactors system (R1 + R2), after the off-season, can generate 5.1 kWh d−1 per m3 of vinasse, or 17% of the electricity needed to process a ton of sugarcane.

Assessment of Composition Changes, Stability Degree and the Potential of Biogas Formation of Sewage Sludge Composts During Maturation Process

The aim of this study was to assess the degree of stabilization of composted sewage sludge (SSC) during maturation using tests in aerobic and anaerobic conditions, determining the potential for biogas formation and its composition, as well as changes of mobile and bioavailable forms of metals in SSC after treatment. The samples were taken in the second phase of composting, during the maturation process. The biological stability of SSC samples was determined by detecting an incubation test (GS21) and respiration index (AT4). The potential for biogas formation and composition changes of SSC during maturation were analyzed. It was found that the chemical composition of the tested samples depended on the degree of their maturity. It was found that the both tested methods (AT4, GS21) of assessing the stability of waste are sufficient. Treatment under anaerobic conditions did not significantly change the composition of the samples, with the exception of total organic carbon (TOC). A high percentage of methane in biogas for samples at the beginning of the maturation process indicates a high content of biodegradable organic matter in SSC. In addition, the decrease of mobile and bioavailable forms of heavy metals percentage, during the SSC maturation, was found. In order to confirm the results of current study, a long-term field studies should be carried out on the effects of SSCs tested on soils and plants.Graphic

Prediction of Methane and Ethane Gas Hydrate Formation and Their Mixture in a Porous Medium

The purpose of this paper is to study the thermodynamic modeling of the conditions for methane and ethane gas hydrate formation and their mixtures in a porous and non-porous environment. In this paper, the Van der Waals- Platteeuw thermodynamic model was used for prediction of gas hydrate formation conditions. Also, the SRK and PTV equations of state were used for calculations of driving force. In this research, the results of thermodynamic modeling in a porous were compared with the non-porous environment and laboratory data in the literature. Studies have shown that the results of the modeling are in good agreement with the laboratory data and the percentage of errors is low. The results also showed that with increasing pressure of porous and non-porous media, the equilibrium temperature increases. In addition, the effect of the pore diameter of porous media on the results of modeling was investigated for methane, ethane and their mixtures during gas hydrates formation. The results showed that by increasing the pressure for any size of the pore diameter of the porous medium, hydrate formation temperature increases. In addition, by increasing the pore diameter of the porous medium, hydrate formation temperature methane, ethane and their mixture increase at a constant pressure. The results also showed that the equilibrium temperature of the non-porous medium is higher than the equilibrium temperature of the non-porous medium. This shows that the hydrate formation in the porous medium has a deterrent effect and leads to lower temperatures and higher temperatures conditions for gas hydrate formation. The results showed that by increasing the percentage of methane in a porous or non-porous medium, the temperature of hydrate formation of the binary gas mixture of methane and ethane decreases.

Effect of mixing duration on biogas production and methanogen distribution in an anaerobic digester

ABSTRACT Mixing has been shown to have effect on biogas production in anaerobic digestion systems. To further examine this impact, a study was designed to evaluate nearly continuous mixing (mixing for 15 min followed by no mixing for 15 min, CON), intermediate mixing (mixing for 15 min followed by no mixing for 45 min, INT) and no mixing (unmixed, NO) on biogas production in three 208 L pilot-scale tank reactors. The experiments were conducted in triplicates at a controlled temperature of 37 ± 1°C, with a total solids percentage of 5%, a hydraulic retention time (HRT) of 21 days, and an organic loading rate (OLR) of 2 kg VS m−3 d− 1. Digesters with NO mixing had greater solids build up in the bottom quarter of the digester after four weeks’ retention time. The methane percentage in biogas produced from digesters with INT and CON mixing were 63% and 62%, respectively, which were 4% and 5% higher than that from digesters with NO mixing (58%). The specific methane yield for digesters with NO, INT and CON mixing was 1.15, 1.15, and 1.49 m3-methane per kg-VS destroyed, however, those differences were not statistically significant (p > 0.05). Digesters had the least amount of Methanosarcinales of the methanogens measured under all treatments. However, the Methanosarcinales, Methanosarcinaceae, Methanomicrobiales, and the total amount of methanogens were less in digesters with INT mixing compared to NO and CON mixing treatments.

Streamer propagation in the atmosphere of Titan and other N2:CH4 mixtures compared to N2:O2 mixtures

Streamers, thin, ionized plasma channels, form the early stages of lightning discharges. Here we approach the study of extraterrestrial lightning by studying the formation and propagation of streamer discharges in various nitrogen-methane and nitrogen-oxygen mixtures with levels of nitrogen from 20% to 98.4%. We present the friction force and breakdown fields Ek in various N2:O2 (Earth-like) and N2:CH4 (Titan-like) mixtures. The strength of the friction force is larger in N2:CH4 mixtures whereas the breakdown field in mixtures with methane is half as large as in mixtures with oxygen. We use a 2.5 dimensional Monte Carlo particle-in-cell code with cylindrical symmetry to simulate the development of electron avalanches from an initial electron-ion patch in ambient electric fields between 1.5Ek and 3Ek. We compare the electron density, the electric field, the front velocities as well as the occurrence of avalanche-to-streamer transition between mixtures with methane and with oxygen. Whereas we observe the formation of streamers in oxygen in all considered cases, we observe streamer inceptions in methane for small percentages of nitrogen or for large electric fields only. For large percentages of nitrogen or for small fields, ionization is not efficient enough to form a streamer channel within the length of the simulation domain. In oxygen, positive and negative streamers move faster for small percentages of nitrogen. In mixtures with methane, electron or streamer fronts move 10–100 times slower than in mixtures with oxygen; the higher the percentage of methane, the faster the fronts move. On Titan with methane percentages between 1.4% and 5%, a successful streamer inception would require a large electric field of 4.2 MV m−1 (3Ek). Such large fields might not be present and explain the non-detection of Titan lightning by the Cassini/Huygens mission.

Investigation of the combustion characteristics of briquettes prepared from olive mill solid waste blended with and without a natural binder in a fixed bed reactor

This paper aims at studying the combustion in a homemade combustion chamber of biofuel briquettes prepared from olive mill solid wastes. Two different samples of briquettes compressed under 150 MPa and 35 °C were investigated: with binder (BOMSW) by adding corn starch and without binder (OMSW). Three combustion regimes were considered: 18, 36, and 55 m3/h, respectively. Seven K-thermocouples were used for temperature measurements. Moreover, the gaseous emission analysis was undertaken. Results show that the flame front propagation velocity reaches maximum values of 11 mm s−1 and 8.54 mm s−1 for OMSW and BOMSW, respectively. We find that the NOx content was higher in the case of the OMSW. On the contrary, the percentages of methane, carbon monoxide, and sulfur dioxide were more significant with the BOMSW. The combustion efficiency was evaluated and gives a higher value with BOMSW. We concluded that the used binder affects seriously the combustion efficiency and the gaseous emissions.

Anaerobic Membrane Bioreactor for Urban Wastewater Valorisation: Operative Strategies and Fertigation Reuse

In European scenario, the potential source for water supply from treated wastewater is actually estimated in 1,100 Mm3/y (EU-ENV, 2015). Anaerobic processes compared with conventional aerobic ones, cause a net reduction of the operative costs and possible reuse for fertigation purposes. The tested anaerobic pilot (HRT 6 h and T 30°C) is constituted from a UASB reactor (16 L). Increment of influent organic loading rate (OLR) was studied for 1 year from 1 to 2 kgCOD/m3/d by feeding raw wastewater (Period 1), methanol (Period 2) and fermented supernatant from cellulosic sludge (Period 3).The biogas production was assessed equal to 0.13 m3biogas/kgCOD (Period 1), to 0.57 m3biogas/kgCOD (Period 2) and to 0.24 m3biogas/kgCOD (Period 3) with methane percentages constant around 33%. UASB effluent has not the final quality to comply limit values for water reuse and fertigation, especially for microbiological parameters. Further treatments could be necessary to achieve the removals of bacteria, such as E.Coli, recalcitrant organic traces and metals. Therefore, some advanced post treatments have been studied in this paper after UASB treatments, like UV disinfection, UV coupled with H2O2 and GAC adsorption. The innovative solution is coupling UASB reactor with anaerobic submerged sidestream AnMBR (UF hollow fiber membrane with 0.03 µm of nominal pore-size and 0.5 m2 of surface area KOCH, Puron single bundle). Membrane cleaning was carried out using sodium hypochlorite solution (400 ppm) each 45 days to remove organic fouling and to recover the initial permeability of the membrane. The average operative flux at process temperature was equal to 8.8±1.9 L/h/m2 and operating TMP of 44.6±8.5 mbar was detected. The removal of E.Coli was investigated in the effluent from UASB and in the permeate from AnMBR process. At clean membrane conditions, complete removal of bacteria (99±1%) was found. Furthermore, the determination of microplastics distribution was carried out both in the experimental anaerobic pilot and in the conventional full scale aerobic treatment plant. The effluent microplastics were quantified and the removal role of the different operative units was studied.

Gasification of waste tires in a circulating fixed-bed reactor within the scope of waste to energy

Thermochemical decomposition of waste tires was evaluated in order to produce solid and gaseous products within the aim of waste-to-energy concept. Pyrolysis and gasification occur in an “oxygen-starved” environment to “thermally degrade” organic wastes. Waste tires form a large volume of a landfill space that may lead to serious environmental issues and management complexities. Proximate and ultimate analyses reported that approximately 80% carbon in waste tire can be converted to different solid, liquid and gaseous forms for energy gain. Pyrolysis and gasification experiments were carried out in a circulating fixed-bed reactor with cyclone separator at varying temperatures between 600 and 800 °C. Dried air (0.05–0.5 L/min) and pure oxygen (0.01–0.015 L/min) were fed to gasification reactor as partially oxidizing agents. Pyrolysis gasification (PyroGasification—PG) was conducted to produce “syngas” which mainly contains carbon monoxide and hydrogen. One and 4 h of cooking time for the first-step pyrolysis were applied in a nitrogen-rich medium before gasification to enrich carbon amount in fuel. A syngas rich in H2, CH4 and CO with a high calorific value of almost 4900 kcal/m3 was obtained in gasification experiments performed with 0.05 L/min of dried air. Volumetric percentages of hydrogen and methane in syngas were around 35% and 40%, respectively. More than 65% mass and 80% volume reductions which are very important for waste management hierarchy and minimization were achieved by gasification of waste tires.

Underground coal gasification – A numerical approach to study the formation of syngas and its reactive transport in the surrounding strata

In this work, a method to study the formation of syngas during the underground coal gasification (UCG) process and its reactive transport in the surrounding strata is proposed. It combines a thermodynamic equilibrium stoichiometric model of the cavity reactions with a coupled thermo-hydraulic-chemical–mechanical (THCM) framework of COMPASS code for the transport of UCG products away from the cavity. With the input information of coal properties obtained from the South Wales coalfield, gasification reagents (air and steam) and thermodynamic conditions (initial temperature and pressure), the thermodynamic equilibrium model developed provides the maximum yield of gasification products and temperature from a UCG system. Gasification results giving the syngas composition with the highest percentage of methane and carbon dioxide, are then used as the chemical (gas) and thermal boundary conditions for the coupled thermo-chemical model of the THCM framework to analyse the variations of temperature and gas concentrations, in strata surrounding the UCG reactor. For that purpose, a set of numerical simulations considering three porous media (coal, shale and sandstone) with different physico-chemical properties is conducted. The gasification results demonstrate that increasing the amount of steam injected in the UCG reactor decreases the temperature of the system as well as the concentration of carbon monoxide and nitrogen, while benefiting the production of hydrogen, methane and carbon dioxide. The numerical simulations performed using the THCM model indicate that multicomponent gas diffusion and advection are competing transport mechanisms in porous media with intrinsic permeability higher than 1 mD (sandstone), while the gas diffusion becomes a dominant transport process in porous media with an intrinsic permeability lower than 1 mD (coal and shale). Moreover, the simulation results of reactive transport of methane and carbon dioxide in different porous media demonstrate the significance of considering the adsorption effect in the gas transport in the overall UCG process. In particular, the retardation of the gas front due to gas sorption is the most pronounced in coal, followed by shale and then sandstone. In conclusion, the model presented in this study demonstrates its potential application in managing the environmental practices, reducing pollution risk and securing greater public and regulatory support for UCG technology.

Infrared Spectroscopy of Disilicon-Carbide, Si2C: The ν3 Fundamental Band

The ν3 antisymmetric stretching mode of disilicon-carbide, Si2C, was studied using a narrow line width infrared quantum cascade laser spectrometer operating at 8.3 μm. The Si2C molecules were produced in an Nd:YAG laser ablation source from a pure silicon sample with the addition of a few percent methane diluted in a helium buffer gas. Subsequent adiabatic expansion was used to cool the gas down to rotational temperatures of a few tens of kelvin. A total of 183 infrared transitions recorded in the spectral range between 1200 and 1220 cm-1 were assigned to the fundamental ν3 mode of Si2C. In addition, pure rotational transitions of Ka = 1 and 2 between 278 and 375 GHz were recorded using a supersonic jet spectrometer for submillimeter wavelengths. Molecular parameters for the ( v1 v2 v3) = (001) vibrationally excited state were derived and improved molecular parameters for the vibrational ground-state (000) were obtained from a global fit data analysis, which includes our new laboratory data and millimeter wavelength data from the literature. We found the rotational levels Ka = 0 and Ka = 2 in the vibrationally excited (001) state being perturbed by a Coriolis-type interaction with energetically close lying levels of the symmetric stretching and triple-excited bending mode (130). The data analysis was supported by quantum chemical calculations performed at the coupled-cluster level of theory. All experimental results were found to be in excellent agreement with the theory.

The use of sugar beet pulp stillage for co-digestion with sewage sludge and poultry manure.

The anaerobic mesophilic co-digestion of sugar beet pulp stillage with poultry manure and municipal sewage sludge was investigated in this study. The sugar beet pulp stillage (SBPS) mono-digestion failed owing to an accumulation of volatile fatty acids, leading to a pH value lower than 5.5. A 20% addition of poultry manure to stillage allowed for stable digestion performance despite high volatile fatty acid (total volatile fatty acids) concentrations of 5500-8500 g m-3 with propionic acid being the predominant one and constituting 72%-76% total volatile fatty acids. For this mixture, the maximum methane production of 418 dm3 kgVSfed-1 was achieved when the reactor was operated at a solids retention time of 20 days and an organic loading rate of 4.25 kgVS m-3 d-1. The co-digestion of stillage with 60% municipal sewage sludge gave the average methane yield of around 357 dm3 kgVSfed-1 for all operational conditions applied, however, the methane percentage of biogas (up to 70%) was far greater than the corresponding values obtained for sugar beet pulp stillage-poultry manure co-digestion. Neither ammonia nor volatile fatty acids destabilised the biogas production, and the volatile fatty acid profile showed the dominance of acetic acid (72%-82% total volatile fatty acids) followed by propionic and butyric acids.

Effect of the volume of methane released into respiration chambers on full system methane recovery

The respiration chamber method is considered to be the most precise approach for measuring enteric methane emissions in cattle. A set of experimental runs was carried out in which increasing volumes of pure methane (168.5, 194.9, 234.9, 264.9, 301.0, 339.8, and 375.7 L per run) were gravimetrically released into open-circuit respiration chambers to simulate the volumes of methane eructated by cattle of different weights. The aim was to assess the effect of the volume of methane released into the chambers on percentage of methane recovered at the exit by the infrared methane analyzer. It was found that as the volume of methane released into the respiration chambers was decreased, methane recovery percentages were concomitantly reduced. The recovery percentages ranged from 103.7% down to 18.3% and from 102.7% down to 31.6% for chambers one and two, respectively. It can be concluded that the slow stabilization of methane inside the large volume chamber, when injected at low rates from the cylinder, led to low recoveries of the gas at an air extraction rate of 300 L/min. As a result, the recovery of methane was constrained, leading to underestimation of the actual volumes released from the pure methane cylinders. Poor mixing of air inside the chambers did also constrain the recovery of methane with the experimental approach employed. The possible implications for methane measurements in respiration chambers under in vivo conditions with cattle are discussed.

Anaerobic co-digestions of agro-industrial waste blends using mixture design

Batch assays were performed under a stressed condition during the anaerobic digestion process to assess the effect of component proportions on the quantity and pattern of biochemical methane yield of two sets of mixtures, consisting of poultry droppings (PD) with sugarcane bagasse (SB) and press mud (PM) for set A and PD with sugar beet roots and tops (SBRT) and PM for set B. Augmented simplex centroid design was used to design the mixture composition for the anaerobic co digestion. The reactor performances were assessed under identical conditions using cumulative methane yield (CMY) and percentage volatile solids destruction (PVSD) as the criteria. The maximum volume of methane were obtained 48.5 NL CH4 kg−1 VS at mixture proportion of 66.67% of PM, 16.665% of PD and 16.665% of SB for set A and 44 NL CH4 kg−1 VS at mixture proportion of 50% of PM and 50% of PD for set B. Synergistic effect were observed by adding a greater proportion of PM for both the sets of A and B. Antagonistic effect were obtained by adding a greater proportion of SB for set A and a higher proportion of SBRT for set B. Response surface methods and modeling were used to find out optimum mixture combinations for maximizing the methane production. From the optimization plots, the use of PD having the antagonistic effect was found for both the sets of A and set B.

Hydrogen and Methane Production from Food Residue Biomass Product (FORBI)

This study concerns the production of hydrogen and methane from a Food Residue Biomass (FORBI) product (Papanikola et al. in 5th international conference on sustainable waste management systems, Athens, 2017), generated from pre-sorted HFW in a CSTR and in a PABR respectively. FORBI is generated by drying and shredding the fermentable fraction of household food waste collected door-to-door in the Municipality of Halandri, Greece. Hydrogen production from FORBI through anaerobic fermentation under acidogenic mesophilic conditions was carried out using a 4 L CSTR, operated at 12 h HRT under an organic loading of 15 g TS L−1. The H2-CSTR was operated for 40 days. During the operation of H2-CSTR the production of biogas reached up to 0.1026 Lbiogas gFORBI−1 and the percentage of hydrogen in the gas up to 48.2%. The conversion of FORBI into methane was carried out through the operation of a 77 L PABR operated under mesophilic methanogenic conditions at various operating parameters (OLR, HRT, T). Two different approaches were adopted for the pre-treatment of the feedstock. For the two first phases of the experimental procedure, a liquid extraction step was carried out before feeding the bioreactor with the separated liquid fraction, while in the subsequent three phases, a whole suspension of FORBI was used as feed. The mean biogas production rate was 0.158 ± 0.02 Lbiogas gFORBI−1 and the mean methane percentage in the biogas was 67.5 ± 2.1%, in the first two phases. The mean biogas production rate was 0.519 ± 0.03 Lbiogas gFORBI−1 and the mean methane percentage in the biogas was 66 ± 2.8%, when a whole suspension of FORBI was fed to the PABR.

Upgrading Physicochemical Properties using Torrefaction Process and Anhydrous Weight Loss Modelling for Palm Mesocarp Fiber

Abstract Torrefaction is a thermal process for upgrading biomass properties in order to promote biomass utilization for sustainable energy production. It is performed under inert condition at temperature range 200 - 300°C with residence times between 15 – 60 minutes. Torrefied product usually have high energy content, low moisture content and hygroscopic nature which overcome the limitation of raw biomass as biofuel. Therefore, the objective of this study is to investigate the characteristics of torrefied palm mesocarp fiber (PMF) and evolution of volatiles components during torrefaction at 240°C, 270°C, and 300°C in an inert condition. The condensable and non-condensable gases were analyzed using high performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC-MS) respectively. Concurrently, a kinetic model using two reactions in series namely Di Blasi and Lanzetta model is developed to predict the evolution of solid and volatile products during torrefaction process for PMF samples. Based on torrefaction experiments, the mass and energy yields are decreased due to the severe decomposition of biomass at higher temperature but the higher heating value of biomass is increased by 27%. Meanwhile the proximate analysis shows that fixed carbon and ash content are increased by 45% and 25% respectively but volatile matter is decreased by 20%. In addition, the ultimate analysis shows that the elemental ratios of hydrogen to carbon (H/C) and oxygen to carbon (O/C) are decreased by 88% and 20% respectively. For the volatile analysis, 70 – 80% of the total volatile yield is made up from non-condensable gases with high percentage of carbon monoxide (CO) and methane (CH4), while the condensable gases formed was 20-30%. Finally, the anhydrous weight loss model is successfully developed for representing the decomposition of PMF where the kinetic parameters estimated from the model give a good agreement with the residual mass obtained from thermogravimetric analysis.

Microstructure and Chemical Composition of Particles from Small-scale Gas Flaring

ABSTRACT Among globally relevant combustion sources, such as diesel emission and biomass burning, gas flaring remains the most uncertain. In this study, small-scale turbulent gas flaring was used to characterize particulate emissions produced under different operating conditions, such as various burner diameters and exit velocities. The composition of the fuel was also varied by modifying the percentage of methane, ethane, propane, butane, N2, and CO2, which are the predominant constituents in the upstream oil and gas industry. A broad suite of physical, chemical, and microscopic techniques was employed for analysis, and scanning electron microscopy showed the generated soot agglomerates to be composed of primary spherules that were 30 ± 10 nm in diameter. Additionally, high-resolution transmission electron microscopy, used to determine the length, tortuosity, and separation of individual graphene fringes on the primary particles, revealed a fullerenic, multiple-nuclei internal structure. Single-particle analysis revealed the dominance of elemental carbon vs. oxidized and metal-contaminated particles, and infrared spectroscopy showed the presence of alkanes and aromatics with oxygenated compounds. Intercomparing the microstructure and the composition, we also concluded that the vast majority of particles are hydrophobic.

Probability Density Function Modeling of Turbulence/Chemistry Interactions in Methane Flame Enrichment by Hydrogen

The present investigation illustrates a computational study of the turbulent diffusion flame in a cylindrical burner that is confined by two coaxial jets (methane/hydrogen and air). This is to improve the reactive mixture, the reactants combustion and to reduce the concentration of carbon monoxide as pollutant chemical species. The coupled models LES/PDF are, hereby, used to surmount the turbulence/chemistry interaction in the transport equations of chemical species. The predicted mixture fraction, the progress variable, and the carbon monoxide mass fraction are selected to validate the coupled models with respect to the experimental references data. Furthermore, the same scalar parameters which are considered in the previous numerical validation are evaluated from different fuel compositions of the hydrogen and the methane percentage to supply the combustion chamber. The computed results are carried out by FLUENT-CFD; where, they prove that hydrogen addition reduces the carbon monoxide concentration in the combustion products and improves the reactants combustion caused by the rich mixture.

Experimental Study of Turbulent Burning Velocity of Premixed Biogas Flame

Biogas is a renewable source of energy produced by anaerobic digestion of organic material and composed mainly of methane (CH4) and carbon dioxide (CO2). Despite its lower heating value, biogas can still replace fossil fuels in several engineering stationary power generation and other industrial applications. Although numerous published studies were devoted to advance our understating of biogas combustion, experimental data of some parameters such as turbulent burning velocity (St) under certain operating conditions is still lacking. The present study aims to experimentally determine biogas turbulent burning velocity under normal temperature and pressure conditions. Turbulent premixed biogas–air flame was ignited at the center of a 29 L fan-stirred spherical combustion chamber of nearly homogeneous and isotropic turbulence. Test conditions consisted of varying turbulence intensity and biogas surrogate composition. Outwardly propagating biogas flames were tracked and imaged using Schlieren imaging technique. The results showed that, by increasing turbulence and reducing methane percentage in the surrogate, the flammability of the mixture shrinked. In addition, the curve fits of biogas turbulent burning velocity versus the equivalence ratio exhibited two different trends. The peak of turbulent burning velocity shifted away from nearly lean equivalence ratio toward the stoichiometric at a fixed turbulence intensity and higher CH4 percentage in the surrogate. However, for the same biogas surrogate composition, the peak of turbulent burning velocity shifted away from stoichiometric toward leaner equivalence ratio with increased turbulence intensity.