Methane Ammonia Research Articles

The Effect of Methane–Ammonia and Methane–Hydrogen Blends on Ignition and Light-Around in an Annular Combustor

Abstract The use of hydrogen and ammonia in gas turbines, either alone or blended with natural gas, poses various technical challenges for combustion systems, including ignition. Depending on the fuel composition, the laminar flame speed and the ratio of unburned to burned gas density (dilatation ratio) of hydrogen and ammonia flames can be well outside the range seen in natural gas flames. Previous studies in annular combustion chambers have provided evidence of the importance of these properties in determining the ignition dynamics including light-around times. So far, these studies have mostly considered hydrocarbon fuels, have been limited to only a few runs, and have not yet systematically investigated variations in the dilatation ratio and the flame speed but rather have considered them as a lumped parameter. To investigate these effects in more detail, experiments characterizing the light-around times were carried out on an atmospheric annular combustor in which the dilatation ratio and the laminar flame speed was independently varied. This was achieved by varying the equivalence ratio and employing a variety of different hydrocarbon fuels (ethylene, propane, and methane) and fuel blends of methane–ammonia and methane–hydrogen. Light-around times were evaluated from global chemiluminescence measurements obtained using an azimuthal array of photomultipliers placed round the combustor chamber as well as high speed imaging. To improve statistical certainty, more than 3000 ignition and light-around times were measured with 30 repetitions obtained for each operating condition. To provide some insight into the light-around dynamics in specific cases, 900 of the 3000 sets included high-speed OH* chemiluminescence images. Light-around times for premixed pure hydrocarbon flames showed a similar dependence on the laminar flame speed as reported in previous studies. For the range of ammonia fuel blends investigated, an increase in laminar flame speed leads to a predictable increase in the flame propagation speed, as in the case of hydrocarbon fuel. Furthermore, collapse of this dependence for all blends could be achieved when corrected for an effective Lewis number, noting that all Lewis numbers for these blends were above unity. However, for hydrogen fuel blends, a decrease in dilatation ratio was found to decrease the light-around time counter to existing experimental results on the ignition of hydrocarbon fuels for which we currently do not have an explanation.

Experimental Study on the Effect of Hydrogen Addition on the Laminar Burning Velocity of Methane/Ammonia–Air Flames

Variations in methane–ammonia blends with hydrogen enrichment can modify premixed flame behavior and play a crucial role in achieving ultra-low carbon emissions and sustainable energy consumption. Current combustion units may co-fire ammonia/methane/hydrogen, necessitating further investigation into flame characteristics to understand the behavior of multi-component fuels. This research aims to explore the potential of replacing natural gas with ammonia while making only minor adjustments to equipment and processes. The laminar burning velocity (LBV) of binary blends, such as ammonia–methane, ammonia–hydrogen, and hydrogen–methane–air mixtures, was investigated at an equivalence ratio of 0.8–1.2, within a constant volume combustion chamber at a pressure of 0.1 MPa and temperature of 298 K. Additionally, tertiary fuels were examined with varying hydrogen blending ratios ranging from 0% to 40%. The results show that the laminar burning velocity (LBV) increases as the hydrogen fraction increases for all mixtures, while methane increases the LBV during blending with ammonia. Hydrogen-ammonia blends are the most effective mixture for increasing LBV non-linearly. Enhancement parameters demonstrate the effect of ternary fuel, which behaves similarly to equivalent methane in terms of adiabatic flame temperature and LBV achieved at 40% hydrogen. Experimental data for neat and binary mixtures were validated by different kinetics models, which also showed good consistency. The ternary fuel mixtures were also validated with these models. The Li model may qualitatively predict well for ammonia-dominated fuel. The Shrestha model may overestimate results on the rich side due to the incomplete N2Hisub-mechanism, while lean and stoichiometric conditions have better predictions. The Okafor model is always overestimated.

Characterization of Fourier Transform Infrared, Cavity Ring-Down Spectroscopy, and Optical Feedback Cavity-Enhanced Absorption Spectroscopy Instruments for the Analysis of Ammonia in Biogas and Biomethane.

Novel traceable analytical methods and reference gas standards were developed for the detection of trace-level ammonia in biogas and biomethane. This work focused on an ammonia amount fraction at an upper limit level of 10 mg m-3 (corresponding to approximately 14 μmol mol-1) specified in EN 16723-1:2016. The application of spectroscopic analytical methods, such as Fourier transform infrared spectroscopy, cavity ring-down spectroscopy, and optical feedback cavity-enhanced absorption spectroscopy, was investigated. These techniques all exhibited the necessary ammonia sensitivity at the required 14 μmol mol-1 amount fraction. A 29-month stability study of reference gas mixtures of 10 μmol mol-1 ammonia in methane and synthetic biogas is also reported.

Treatment of Iraqi Municipal Wastewater by up-flow Anaerobic Sludge Blanket Reactor UASB

In this work, the Upflow Anaerobic Sludge Blanket “UASB” reactor treated effluent wastewater to investigate the process performance on a pilot plant scale. Municipal wastewater at high and medium strength with different organic load rate OLR (0.6-9) kg COD m-3day-1 with the flow of 20 l/h, up-flow velocity 0.4 m/h, hydraulic retention time HRT 9 h at a temperature of (20-30 ºC) was evaluated. The wastewater concentration, including TSS, COD was measured, and the removal efficiencies of chemical oxygen demand (COD) and total suspended solid TSS were calculated and summarized as 45-85% and 70-75%, respectively, depending on organic load rate OLR. Effluent volatile fatty acids VFA was measured, and the results were in the range between 12-90 mg/L depending on OLR with a slight change in pH (8.3-8.4), which means the conversion of COD to methane and increase ammonia concentration.

High-pressure phase transition of methane hydrate in water–methane–ammonia system

The phase transition of methane hydrate in water–methane–ammonia system was investigated under pressures up to 20 GPa using synchrotron X-ray powder diffraction (XRD) combined with diamond anvil cells. The XRD experiments revealed that the sI cage structure (MH-I) of methane hydrate transforms into an sH cage structure (MH-II) at approximately 1 GPa, further transforms into a filled-ice Ih structure (MH-III) at approximately 2 GPa, and remains in this structure under pressures up to at least 20 GPa. Ammonia was observed as ammonia hemihydrate phase-II above 3.8 GPa. It is therefore considered that methane hydrate can coexist with aqueous ammonia below 3.8 GPa and coexist with ammonia hemihydrate phase-II above 3.8 GPa. The transition pressures of methane hydrate in the investigated system were consistent with those in water–methane system. These results indicate that, although ammonia is thought to inhibit methane hydrate formation, methane hydrate can be stable in water–methane–ammonia system up to at least 20 GPa and at room temperature. The pressure range in this study covered the pressure conditions inside icy moons, indicating that methane hydrate has a potential to be the main constituent of them.

Direct reforming of Methane–Ammonia mixed fuel on Ni–YSZ anode of solid oxide fuel cells

To control the temperature distribution in the Ni–YSZ (yttria-stabilized zirconia) anode of solid oxide fuel cells (SOFCs) by efficiently utilizing the heat generated by electrochemical reactions, the supply of methane–ammonia mixed fuel is proposed. The reaction characteristics of reforming/decomposition of the mixed fuel on a Ni–YSZ catalyst are experimentally investigated. A mixture gas of methane, steam, ammonia, and balance argon is supplied to a packed bed catalyst placed in a quartz tube in an electric furnace. The crushed Ni–YSZ anode of SOFCs is used as the catalyst. The exhaust gas composition is analyzed by gas chromatography and the streamwise temperature distribution of the catalyst bed is measured by an infrared camera. It is found that ammonia decomposition preferentially proceeds and steam methane reforming becomes active after sufficient ammonia has been consumed. A low-temperature region is formed by steam methane reforming owing to its strongly endothermic nature. Its position moves downstream while its magnitude decreases as the ammonia concentration in the fuel increases. This shows that the local temperature distribution can be controlled by tuning the ratio of methane to ammonia in the mixed fuel. It is also found that, at a certain mixture ratio, the mixed fuel realizes a hydrogen production rate higher than that for only methane or ammonia.

Control of NOx and other emissions in micro gas turbine combustors fuelled with mixtures of methane and ammonia

Methane–ammonia mixtures have potentials as low-carbon fuels for gas turbines, however significantly high fuel NOx production in their flames present challenges to their application. This study aims to provide deep insight into the physical and chemical processes involved in the formation and control of emissions from the combustion of CH4NH3–air with up to 30% ammonia by heat fraction in gas turbine combustors. Hence, laser diagnostics techniques such as Particle Image Velocimetry (PIV), and Planar Laser Induced Fluorescence (PLIF) imaging, in addition to Fourier Transform Infrared (FTIR) gas analysis were employed to study the flow field, flame structure and emissions characteristics of a micro gas turbine swirl combustor fuelled with CH4NH3–air mixtures. The control of emissions from the flames was further studied using Large Eddy Simulation (LES) of a model swirl combustor. The results show that NOx emissions from premixed CH4NH3–air in single-stage combustion were more than 5000 ppmv at equivalence ratios, Φ = 0.8–1.1, which is about twice more than the values already reported for NH3–air. Trends in NOx emissions correspond with the trends in OH radicals concentration in the combustor owing to the relevance of OH radicals in fuel NOx production. Emissions control leading to significantly low emissions such as 49 ppmv of NOx, 2 ppmv of CO and approximately zero N2O, HCN and NH3 emissions with a 99.8% combustion efficiency was achieved using rich-lean combustion. An optimum Φ of the primary combustion zone for low NOx emission was identified, which varied from 1.30 to 1.35 depending on the ammonia fraction. For Φ richer (leaner) than the optimum Φ, NOx emission increased due to an increase in NOx production in the secondary (primary) combustion zone. Rich-lean combustion of CH4NH3–air emitted less NOx than that of NH3-air because the higher flame speed of CH4NH3–air mixtures ensured lower NOx production in the secondary combustion zone.

Enhanced Isotopic Ratio Outlier Analysis (IROA) Peak Detection and Identification with Ultra-High Resolution GC-Orbitrap/MS: Potential Application for Investigation of Model Organism Metabolomes.

Identifying non-annotated peaks may have a significant impact on the understanding of biological systems. In silico methodologies have focused on ESI LC/MS/MS for identifying non-annotated MS peaks. In this study, we employed in silico methodology to develop an Isotopic Ratio Outlier Analysis (IROA) workflow using enhanced mass spectrometric data acquired with the ultra-high resolution GC-Orbitrap/MS to determine the identity of non-annotated metabolites. The higher resolution of the GC-Orbitrap/MS, together with its wide dynamic range, resulted in more IROA peak pairs detected, and increased reliability of chemical formulae generation (CFG). IROA uses two different 13C-enriched carbon sources (randomized 95% 12C and 95% 13C) to produce mirror image isotopologue pairs, whose mass difference reveals the carbon chain length (n), which aids in the identification of endogenous metabolites. Accurate m/z, n, and derivatization information are obtained from our GC/MS workflow for unknown metabolite identification, and aids in silico methodologies for identifying isomeric and non-annotated metabolites. We were able to mine more mass spectral information using the same Saccharomyces cerevisiae growth protocol (Qiu et al. Anal. Chem 2016) with the ultra-high resolution GC-Orbitrap/MS, using 10% ammonia in methane as the CI reagent gas. We identified 244 IROA peaks pairs, which significantly increased IROA detection capability compared with our previous report (126 IROA peak pairs using a GC-TOF/MS machine). For 55 selected metabolites identified from matched IROA CI and EI spectra, using the GC-Orbitrap/MS vs. GC-TOF/MS, the average mass deviation for GC-Orbitrap/MS was 1.48 ppm, however, the average mass deviation was 32.2 ppm for the GC-TOF/MS machine. In summary, the higher resolution and wider dynamic range of the GC-Orbitrap/MS enabled more accurate CFG, and the coupling of accurate mass GC/MS IROA methodology with in silico fragmentation has great potential in unknown metabolite identification, with applications for characterizing model organism networks.

Experimental and numerical study of the laminar burning velocity of CH4–NH3–air premixed flames

With the renewed interest in ammonia as a carbon-neutral fuel, mixtures of ammonia and methane are also being considered as fuel. In order to develop gas turbine combustors for the fuels, development of reaction mechanisms that accurately model the burning velocity and emissions from the flames is important. In this study, the laminar burning velocity of premixed methane–ammonia–air mixtures were studied experimentally and numerically over a wide range of equivalence ratios and ammonia concentrations. Ammonia concentration in the fuel, expressed in terms of the heat fraction of NH3 in the fuel, was varied from 0 to 0.3 while the equivalence ratio was varied from 0.8 to 1.3. The experiments were conducted using a constant volume chamber, at 298 K and 0.10 MPa. The burning velocity decreased with an increase in ammonia concentration. The numerical results showed that the kinetic mechanism by Tian et al. largely underestimates the unstretched laminar burning velocity owing mainly to the dominance of HCO (+H, OH, O2) = CO (+H2, H2O, HO2) over HCO = CO + H in the conversion of HCO to CO. GRI Mech 3.0 predicts the burning velocity of the mixture closely however some reactions relevant to the burning velocity and NO reduction in methane–ammonia flames are missing in the mechanism. A detailed reaction mechanism was developed based on GRI Mech 3.0 and the mechanism by Tian et al. and validated with the experimental results. The temperature and species profiles computed with the present model agree with that of GRI Mech 3.0 for methane–air flames. On the other hand, the NO profile computed with the present model agrees with Tian et al.’s mechanism for methane–ammonia flames with high ammonia concentration. Furthermore, the burned gas Markstein length was measured and was found to increase with equivalence ratio and ammonia concentration.

<b><i>In vitro</i> degradation and gas production of glycerin generated in the biodiesel production chain

This study was realized to evaluate the production of gas and volatile fatty acids when glycerin was used to replace four forage species through the use of a semi-automated technique in vitro. The experimental design included 4 treatments and 4 replications. The treatments consisted of increasing levels of glycerin (0, 30, 50 and 70%), which was used to replace the forage plants Elephant grass, sugar cane silage, corn silage and Brachiaria grass. Replacement of the Brachiaria and Elephant grasses with glycerin linearly reduced the production of methane and carbon dioxide and ammonia nitrogen and had a positive effect on forage quality (p < 0.05). With the addition of glycerin, the values for acetate concentration decreased (p < 0.05); however, when added glycerin there was increased in propionic and butyric acid concentration (p < 0.05). Substitution of forage species for glycerin by tests for semi-automatic technique in vitro reduce the production of greenhouse gases (CH4 and CO2) which reduction in energy loss, and increase volatile fatty acids propionic and butyric.

Determination of carbon number distributions of complex phthalates by gas chromatography-mass spectrometry with ammonia chemical ionization.

An assay method for phthalate esters with a complex mixture of isomer of varying carbon numbers, such as di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP), using gas chromatography-mass spectrometry (GC-MS) positive chemical ionization (PCI) with 5% ammonia in methane is described. GC-MS-PCI-NH3, unlike GC-MS electron ionization (EI) (GC-MS-EI) that produces generally m/z 149 ion as the main base peak and low intensity M(+) peaks, produces higher intensity (M + 1) ions that allow the determination of total (R + R') carbon number distributions based on the various R and R' alkyl groups of the di-esters moiety. The technique allows distinguishing among the various commercial DINP and DIDP plasticizers. The carbon number distributions are determined in the acceptable range of <0.1 mole percent to >85 mole percent (m/m). Several examples of analysis made on commercial DINP and DIDP are presented. The use of only 5% instead of 100% ammonia simplifies use of GC-MS-PCI-NH3 but still produces sufficient M + 1 ion intensities that are appropriate for the assay. In addition, use of low concentrations of ammonia mitigates potential safety aspects related to use of ammonia and provides less corrosion for the instrument hardware.

¡Un tetraedro en mi bolsa!

A pesar de que el tetraedro es bastante frecuente en la vida cotidiana, una buena parte de la población, incluyendo a muchos estudiantes de nivel superior y medio superior, ignora o ha olvidado no sólo sus características geométricas, sino también su nombre correcto (Arroyo-Carmona, 2005). Por ejemplo, es común escuchar frases como: “déme un jugo de triangulito”, “es un triángulo” o “la pirámide”, para referirse a un producto en empaque tetraédrico o a una forma tetraédrica.1 Al respecto, al buscar en la red dos productos alimenticios que se comercializan en empaques tetraédricos, en sus portales electrónicos a ambos empaques se les menciona como… ¡“triangulares”!. Así, con el fin de contribuir a mejorar la enseñanza-aprendizaje de la geometría tetraédrica se presenta la construcción rápida y sencilla de un tetraedro a partir de una bolsa de plástico.

Methane generation during anaerobic fermentation of four livestock slurries

In order to promote livestock slurry recycling,the characteristics of methane generation from pig manure,cow dung,chicken dung and duck dropping during anaerobic fermentation were analyzed by using glass anaerobic fermentation equipment.On specific dates,the methane volume,pH and ammonia nitrogen content of fermentation liquid were measured within 20 days.The results show that after 20 days fermentation,total generated methane from cow dung,duck dropping,pig manure,chicken dung is respectively 2 649 mL,2 515 mL,1 964 mL and 1 278 mL.The volume of methane generated from per unit total solids is respectively 47.60 mL·g-1,45.23 mL·g-1,37.27 mL·g-1and 33.49 mL·g-1.Pig manure prone to acidification during anaerobic fermentation,pH of fermentation liquid decreases to 5.62 at the first 10 days,thereby reducing methane generation.For the chicken manure under anaerobic condition,methane generation weakens with increasing ammonia nitrogen.It is therefore concluded that both pH and ammonia nitrogen soured by fermentation of raw materials are the key factors influencing methane generation of livestock slurries.

Effects of Protease-resistant Antimicrobial Substances Produced by Lactic Acid Bacteria on Rumen Methanogenesis

Effects of protease-resistant antimicrobial substances (PRA) produced by Lactobacillus plantarum and Leuconostoc citreum on rumen methanogenesis were examined using the in vitro continuous methane quantification system. Four different strains of lactic acid bacteria, i) Lactococcus lactis ATCC19435 (Control, non-antibacterial substances), ii) Lactococcus lactis NCIMB702054 (Nisin-Z), iii) Lactobacillus plantarum TUA1490L (PRA-1), and iv) Leuconostoc citreum JCM9698 (PRA-2) were individually cultured in GYEKP medium. An 80 ml aliquot of each supernatant was inoculated into phosphate-buffered rumen fluid. PPA-1 remarkably decreased cumulative methane production, though propionate, butyrate and ammonia N decreased. For PRA-2, there were no effects on CH 4 and CO 2 production and fermentation characteristics in mixed rumen cultures. The results suggested that PRA-1 reduced the number of methanogens or inhibited utilization of hydrogen in rumen fermentation.

Global Kinetic Parameters for Determining the Autoignition Limits and Induction Periods for Mixtures of Methane, Ammonia, Oxygen, and Nitrogen

Formally kinetic constants for the autoignition of methane–ammonia–oxygen–nitrogen mixtures were determined. The results obtained allow one to estimate the critical conditions and autoignition delays of the examined mixtures to assess the explosion hazard of reactors for the synthesis of hydrocyanic acid.

Spectrophotometry of Jupiter in the Wavelength Range 320–1100 nm: Long-Term Observations of Variations over the Disk

Based on long-term spectrophotometric observations of Jupiter in the wavelength range 320–1100 nm, we investigate the variations of aerosol extinction (at λ 320–600 nm) and methane–ammonia absorption (at λ 600–1100 nm) over Jupiter's disk. We give estimates of the optical parameters for the upper cloud layer of the planet, the overlying stratospheric haze, and a Rayleigh atmosphere.

Analysis of organophosphorus pesticides by gas chromatography–mass spectrometry with negative chemical ionization: a study on the ionization conditions

The present paper is aimed to study the optimal ionization conditions of 19 organophosphorous pesticides to be analyzed by gas chromatography (GC) with mass spectrometric (MS) detection in negative chemical ionization (NCI). Isobutane, methane, ammonia in methane, and pure ammonia were used as ionizing gases. The effect of the source temperature on the mass spectrum was evaluated for each pesticide considered in this study and for each ionizing gas. The influence of the electron energy, of the emission intensity and of the gas pressure was also studied for ammonia and ammonia in methane. The MS profiles have shown that NCI fragmentation induced by methane, isobutane and ammonia, generally leads to fragmentation by electron capture. Furthermore, significant differences in the mass spectra of several pesticides were recorded by changing the ionizing gas. Finally, the use of pure ammonia leads to a marked reduction of the background noise, with a parallel improvement of the overall sensitivity of the method, with values of the limit of detection (LOD) lower (<1 μg l −1) than those obtained by methane or isobutane.

Tailoring the diameter of decorated C–N nanotubes by temperature variations using HF-CVD

Patterned films of decorated nitrogenated carbon (C–N) nanotubes were catalytically synthesised by hot filament chemical vapour deposition (HF-CVD) in a nitrogen–methane–ammonia environment. The systematic study of a transition between different kinds of C–N nanostructures as a function of the local substrate temperature ranging from 700 up to 820°C is presented. The morphology, the diameter as well as the properties of the generated tubular structures showed strong dependence on this parameter. By means of electron microscopy a new type of decoration covering all tubular structures was observed. Buckled lattice fringes revealed the disordered graphitic-like character of the hollow C–N nanotubes. Raman spectroscopy confirmed a transition in the microscopic order as a function of temperature. Furthermore field emission in vacuum was studied and showed a spectacular correlation to the deposition temperature and therefore the diameter of the C–N tubes. For arrays of tubes thinner than 50 nm an onset field below 4 V/μm was observed.

Flammability limits, ignition energy, and flame speeds in H 2–CH 4–NH 3–N 2O–O 2–N 2 mixtures

Experiments on flammability limits, ignition energies, and flame speeds were carried out in a 11.25- and a 400-liter combustion vessel at initial pressures and temperatures of 100 kPa and 295 K, respectively. Flammability maps of hydrogen–nitrous oxide–nitrogen, methane–nitrous oxide–nitrogen, ammonia–nitrous oxide–nitrogen, and ammonia–nitrous oxide–air, as well as lean flammability limits of various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures were determined. Ignition energy bounds of methane–nitrous oxide, ammonia–nitrous oxide, and ammonia–nitrous oxide–nitrogen mixtures have been determined and the influence of small amounts of oxygen on the flammability of methane–nitrous oxide–nitrogen mixtures has been investigated. Flame speeds have been measured and laminar burning velocities have been determined for ammonia–air–nitrous oxide and various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures. Lower and upper flammability limits (mixing fan on, turbulent conditions) for ignition energies of 8 J are: H 2–N 2O: 4.5 ∼ 5.0% H 2(LFL), 76 ∼ 80% H 2(UFL); CH 4–N 2O: 2.5 ∼ 3.0% CH 4(LFL), 43 ∼ 50% CH 4(UFL); NH 3–N 2O: 5.0 ∼ 5.2% NH 3(LFL), 67.5 ∼ 68% NH 3(UFL). Inerting concentrations are: H 2–N 2O–N 2: 76% N 2; CH 4–N 2O–N 2: 70.5% N 2; NH 3–N 2O–N 2: 61% N 2; NH 3–N 2O–air: 85% air. Flammability limits of methane–nitrous oxide–nitrogen mixtures show no pronounced dependence on small amounts of oxygen (<5%). Generally speaking, flammable gases with large initial amounts of nitrous oxide or ammonia show a strong dependence of flammability limits on ignition energy.

A theoretical study of the C–H⋯N hydrogen bond in the methane–ammonia complex

The C–H⋯N hydrogen bond in the methane–ammonia complex is studied by determining its bond dissociation energy (BDE) and the n(N)→σ ∗(C–H) interaction. At the MP2(Full)/6-311++G(3df,2p) level of theory with basis set superposition error (BSSE) correction, the BDE was determined to be 2.5 kJ mol −1. The n(N)→σ ∗(C–H) interaction at this level of theory was found to be 3.7 kJ mol −1 by natural bond orbital (NBO) analysis. It was also found that the NBO values are in general higher than the BDE values with BSSE correction when they are compared at the same level of theory.