Flame Reactor Research Articles

Flame synthesis of nanoparticles based on high flux electrostatic atomization burner.

This study presents an innovative electrostatic spray flame synthesis (ESFS) reactor that combines the advantages of electrostatic spray and flame synthesis for precise spray control and efficient single-step continuous synthesis. To overcome the limitations of conventional ESFS systems, which often suffer from low atomized precursor flux, we successfully demonstrated a high-flux disk electrostatic atomizer coupled low-swirl flame reactor, achieving a precursor flux of up to 30 ml/h about 30 times higher than that of typical ESFS devices. The atomized precursor being rapidly carried away from the burner is undergoing high-temperature pyrolysis and particle formation through lifted premixed turbulent flames. The ESFS system provides extensive control over parameters such as flame temperature, equivalence ratio, residence time, initial droplet sizes, and precursor concentrations. For illustrative purposes, the ESFS system was utilized to synthesize silica nanoparticles, demonstrating the capability of synthesizing nanoparticles with various properties. By manipulating the collection position and height, the particle size has made a substantial leap from the nanoscale to the micrometer level. This remarkable achievement underscores the system's enormous potential for precise particle size regulation and one-step synthesis of complex structured thin films.

A review of flame aerosol synthesis technology for the synthesis of nanoparticles and functional energy materials

The outstanding performance of nanomaterials in chemical, magnetic, electrical, catalytic, and mechanical properties has paved the way for the huge market in material fabrication, energy storage, electronics, and many other industries. Traditional synthesis methods are relatively stunted in industrial applicability and scalability due to complex manufacturing processes and long preparation times, hampering the development and commercialisation of nanomaterials. On the other hand, the flame synthesis method emerges as an inexpensive, efficient, and easily scalable method for the commercial production of nanoparticles. The present review aims to highlight the research status and applications of the nanomaterials synthesised by the flame aerosol method. The advancement of flame aerosol synthesis technologies is reviewed, with emphasis on the state-of-the-art flame reactor configuration and design. Critical flame parameters that govern the formation of nanoparticles in the flame are reviewed to provide an understanding of the formation criteria and growth of nanomaterials in the flame environment. The properties and characteristics of carbon-based, platinum group metal, metal oxide, bimetallic nanoparticles, perovskite and high entropy oxide nanomaterials produced by flame synthesis are extensively reviewed. In addition, commercial manufacturing of flame-synthesised materials along with applications of the nanomaterials in the field of thermal or photocatalytic energy storage, fuel cells, and gas sensing are presented.

Kinetic Modeling of the Devolatilization of Pulverized Coal, Poplar Wood, and Their Blends in a Thermogravimetric Analyzer and a Flat Flame Reactor.

Devolatilization kinetics of coal, poplar wood, and blends containing 10 and 20 wt % of biomass were characterized. Measurements were carried out under inert atmosphere with heating rates between 10 K min-1 and ∼106 K s-1 using a thermogravimetric analyzer (TGA) and a flat flame reactor (FFR). Measured data were simulated using the chemical percolation devolatilization (CPD) model and a global kinetic scheme based on two competitive reactions integrating a refined differential reaction model. The CPD model failed to simulate TGA results but reproduced FFR data relatively well. As for the global model, selecting kinetic parameters from the literature turned out to lead to unsuitable predictions. Fitted values of the activation energies Ea,i, pre-exponential factors Ai, mass stoichiometric coefficients Yi, and the reaction model factor n were therefore inferred using a genetic algorithm-based optimization procedure, leading to obtain an excellent agreement between simulated and measured data. The assessed Ea,i values were found to be lower for wood than for coal, which is consistent with the higher energy required to break the strong C-C bonds holding the highly cross-linked aromatic structures of coal. Besides, blending coal with 20 wt % of wood induced a decrease of Ea,i values, which went from 99.79 to 86.1 kJ mol-1 and from 186.72 to 171.57 kJ mol-1 for the first and second reactions prevailing at low and high temperatures, respectively. Finally, the fact that the activation energy of the first devolatilization reaction was found to be lower with the blend containing 20% of wood than for wood illustrated the probable existence of synergies, as also exemplified by the characteristic devolatilization times for blended samples, which were found to be relatively similar to and even lower than that of wood.

An insight into the role of the metal precursor and its concentration in the Spray Flame Synthesis (SFS) of FexOy@C nanoparticles for Fischer–Tropsch Synthesis (FTS) application

The effect of metal precursor composition on the synthesis of iron oxide nanoparticles in a spray flame reactor was studied. Three compounds, iron nitrate, iron acetylacetonate, and ferrocene, were tested at 0.1 M and 0.2 M concentrations. Variation of the iron precursor showed significant effects in crystallinity, crystallite size, and iron oxides content; the ferrocene produced the highest hematite content, and the nitrate showed the greatest magnetite contribution. Besides, all the particle characteristics changed when the concentration was duplicated, which was found mainly determined by the positive influence of the iron catalytic effect on the flame energy. FTS catalysts were prepared by the FexOy@C samples carburization, obtaining different active phase (χ-Fe5C2) contents from 52% to 92% and depending on the iron precursor employed. Catalysts exhibited good performances for FTS with CO conversions up to 70% and selectivity to C5+ products from 59% to 71%.

Special features of soot formation in a standard premixed ethylene/air flame diluted with DME

This paper presents the experimental and calculated results of the investigation of soot formation in a standard premixed ethylene/air flame with the addition of 15–100% dimethyl ether. The soot volume fraction was measured using the laser light extinction method at a wavelength of 520 nm. The flame temperature versus height above the burner was measured using standard Pt-Rh thermocouples. It was experimentally shown that the addition of 15% dimethyl ether to ethylene/air flame resulted in a 20% increase of soot volume fraction. The further replacement of ethylene by 60% dimethyl ether decreased the soot volume fraction at 5 fold relatively to a pure ethylene/air flame. Kinetic modeling of soot volume fraction growth with height above the burner was carried out based on the kinetic mechanisms developed by CREСK group (http://creckmodeling.chem.polimi.it/). The calculations were carried out using open software package OpenSMOKE ++, which includes the modeling of gas-dynamic processes in the premixed laminar flame reactor. Good agreement between the experimental and calculated data was obtained. The analysis of kinetic mechanism used in this study allowed determining the peculiarity of kinetic pathways of benzene formation, which is proposed as an initial substance for soot precursor. It was found, that increase of soot concentration at 15% dimethyl ether addition to the ethylene/air flame is caused by intensification of channel of benzene formation via C3H3 recombination, which additionally produced from C3H4-p (propyne). In turn, the increase of C3H4-p concentration occurred due to reactions of acetylene with CH3 radical formed during DME decomposition. These results obtained in a standard ethylene/air flame could be used for development and validation of various kinetic mechanisms of soot formation.

Fluorescent carbon dots synthesis in premixed flames: Influence of the equivalence ratio

Flame synthesis could represent a controllable method for production of carbon dots (CDs) with tunable emission properties, alternative to process involving oxidation agents and wet chemistry processing. To control final properties of CDs, a thorough analysis of different reactor parameters has to be conducted. Here we investigate the effect of combustion operative conditions, namely equivalence ratio, for CD production in a premixed flame reactor. CDs with specific optical properties have been synthesized at different equivalence ratios, burning both pure ethylene and ethylene/benzene mixtures. Carbon particulate matter was thermophoretically collected at the exhaust of the flame reactor. Successively, after dichloromethane washing, CDs were simply obtained by N-methyl-pyrrolidone extraction and filtration (<20 nm). In ethylene flames, CDs with fluorescence ranging from green to yellow, as equivalence ratio increases, were synthesized. In ethylene/benzene flames, produced CDs emit fluorescence from blue to green and equivalence ratio seems to play even a more marked role, inducing significant change in the emission spectra with small changes of equivalence ratio. Globally, their quantum yield ranges between 2 and 11%. CDs have been found generally stable for mild change of temperature (up to 80 °C), mild basic pH (pH = 8–10) and over long time at room temperature (up to 240 days). Overall, equivalence ratio demonstrates to be a powerful and simple tool to produce tunable CDs by flame synthesis on large scale.

LES of nanoparticle synthesis in the spraysyn burner: A comparison against experiments

The synthesis of iron oxide nanoparticles from iron nitrate in the SpraySyn spray flame reactor was investigated by experiment and simulation. The focus was on the spray and flame structure, the particle growth by nucleation and coagulation, and the unresolved effects and their impact on the dispersed phase. The reacting flow was modeled in large eddy simulations with the premixed flamelet generated manifolds technique, including modifications for aerosol nucleation. Particle dynamics were described with a sectional model and a subgrid scale coagulation kernel. The particle size distributions at different distances from the burner surface were obtained using a particle mass spectrometer. The experiments and simulations are in good agreement for the flame centreline velocity and both size distribution and mean size of the particles (for particles larger 1 nm - the approximate detection limit of the experiment). Furthermore, simulations enabled to interpret the temporal evolution of the particle size distribution.

Numerical analysis of NOx formation mechanisms and emission characteristics with different types of reactants dilution during MILD combustion of methane and coke oven gas

A numerical study is conducted to emulate the MILD combustion conditions in actual industrial furnaces and to explore the effects of different types of reactants dilution on NOx formation mechanisms and emission characteristics of methane and coke oven gas (COG) combustion. A well-stirred reactor (WSR) is utilized to generate high-temperature flue gas that dilutes and preheats the fuel and the oxidizer at different dilution ratios. The model with two plug-flow reactors and one opposed-flow diffusion flame reactor is selected for the simulations. The OH radical profile analysis indicates that COG combustion maintains a larger reaction zone due to high hydrogen concentration as compared to methane combustion. The results show that there exists a critical oxygen percentage that divides MILD combustion into two different combustion regimes based on the inlet temperature Tin of the reactants. And the critical oxygen percentage to achieve MILD combustion is about 9.5% and 7.5% for methane and COG, respectively. Moreover, the effect of different dilution types on the NOx emissions indicates that the NOx emission index (EINO) value for the fuel dilution case is about 0.2 g-NO/kg-fuel whereas the value for the oxidizer dilution case is around 0.4 g-NO/kg-fuel at the dilution ratio of 0.9. The comparison between the EINO values for fuel dilution and oxidizer dilution cases suggests that the fuel dilution is more effective to reduce NOx emission than the oxidizer dilution. The relative contribution analysis of different NOx formation routes reveals that the dominant NOx formation route is the prompt route for methane combustion whereas the N2O intermediate and NNH routes are also important for COG combustion. The results provide a good insight into the NOx formation mechanism and assist in the design of a low NOx burner of MILD combustion.

Effects of Reaction Mechanisms and Differential Diffusion in Oxy-Fuel Combustion Including Liquid Water Dilution

The influence of chemistry and differential diffusion transport modeling on methane oxy-fuel combustion is analyzed considering different diluent characteristics. Analyses are conducted in terms of numerical simulations using a detailed description of the chemistry. Herein, different reaction mechanisms are employed to represent the combustion of methane. Simulations were performed with the computational fluid dynamics (CFD) code CHEM1D following different numerical setups, freely propagating flame, counter flow flame, and propagating flame in droplet mist reactors. The employed method is validated against experimental data and simulation results available in the literature. While the counter-flow flame reactor is exclusively used in the validation stage, different scenarios have been established for propagating flame simulations, as in single- or two-phase flow configuration. These comprehend variations in diluent compositions, reaction mechanisms, and different models to account for diffusion transport. Conducted investigations show that the choice for a specific reaction mechanism can interfere with computed flame speed values, which may agree or deviate from experimental observations. The achieved outcomes from these investigations indicate that the so-called GRI 3.0 mechanism is the best option for general application purposes, as a good balance is found between accuracy and computational efforts. However, in cases where more detailed information and accuracy are required, the CRECK C1-C3 mechanism demonstrated to be the best choice from the evaluated mechanisms. Additionally, the results clearly indicate that commonly applied simplifications to general flame modeling as the unitary Lewis number and mixture averaged approach strongly interfere with the computation of flame propagation speed values for single- and two-phase flows. While the application of unitary Lewis number approach is limited to certain conditions, the mixture averaged approach demonstrated a good agreement with the complex model for flame speed computations in the various tested scenarios. Such an outcome is not limited to oxy-fuel applications, but are straightly extensible to oxy-steam and air-blown combustion.

Multi-line SiO fluorescence imaging in the flame synthesis of silica nanoparticles from SiCl4

Flame synthesis is a powerful and scalable method for generating nanoparticles for a wide range of applications. The chemical interaction of the flame and the precursor combined with the spatial and temporal temperature distribution determine the product properties. For controlled nanoparticle synthesis that can also be scaled to industrial production rates, detailed knowledge of the underlying chemical kinetics and their interaction with the reactive flow is essential. Laser diagnostics has the capability to analyze the process by probing the concentration of important intermediates in shock tubes and reactive flows. The gas-phase synthesis of silica nanoparticles from SiCl 4 in a premixed H 2 /O 2 low-pressure flame reactor is studied by laser-induced fluorescence imaging of SiO mole fractions and temperature. The literature value-based spectroscopy model of SiO used for fitting the LIF spectra are validated based on absorption cross-sections measurements in a shock tube, where SiO is formed under precisely defined conditions (temperature, pressure, mole fraction) using a well-known kinetics mechanism for SiH 4 /CO 2 /Ar decomposition. Based on literature sources, a reaction mechanism is assembled to describe the oxidation of SiCl 4 in the flame, which is then compared to the measured SiO mole fractions distribution to shed light on the current state of the understanding of SiCl 4 combustion chemistry and to direct further refinements.

Impact of a Tapered Design in the Performance of Diffusion Flame Reactors

Several research projects developed processes for precise nanoparticle positioning with high production rates. Among the gas phase manipulation strategies, the study of the inertial properties received special attention for the fabrication of nanostructured systems. In particular, aerodynamic focusing technique has allowed particles concentration onto a single streamline, improving collimated particle beam formation and opening new perspectives for nanoparticles production in the gas phase. In this paper, the influence of the reactor design was investigated, particularly in respect to the gas phase characteristics, aiming to improve the nanoparticles focusing. It was observed that a concentrated beam can be obtained in the new tapered reactor design without significantly affect the production rate and temperature profile. In addition, the coupling of aerodynamic lenses to the tapered reactor was also investigated, showing that the flow can be better focused at the cost of an increase in the average temperature and pressure drop.

Self-preserving size distribution and collision frequency of flame-made nanoparticles in the transition regime

Coagulation of polydisperse primary particles is the dominant agglomerate growth mechanism in flame reactors and in the low-temperature or high-pressure regions of combustion engines. Here, the evolution of agglomerate size distribution (SD) and collision frequency function of coagulating soot and silica primary particles is investigated with simultaneous surface growth or coalescence using discrete element modeling (DEM). The growth of polydisperse soot and silica nanoparticles is captured from the free molecular up to the transition regime in excellent agreement with microscopy and mobility measurements in diffusion flames and flame spray pyrolysis (FSP) reactors. The broad agglomerate size distributions of soot and silica formed in the free molecular regime narrow by coagulation in the transition regime, attaining their mobility-based quasi-self-preserving or signature SD with the same geometric standard deviation of 1.48 ± 0.03, in excellent agreement with soot or silica SDs measured from diffusion flames and the CAST generator or from a FSP reactor, respectively. The coagulation rate of both soot and silica agglomerates is about twice as much higher as that of monodisperse agglomerates in the transition regime, regardless of material or combustion conditions. The DEM-derived collision kernel enhanced by a factor of 1.82 ± 0.35 can be interfaced with method of moments and monodisperse population balance models to improve the design of aerosol flame reactors and combustion engines.

Low- and high-temperature study of n-heptane combustion chemistry

n-Heptane has been used extensively in various fundamental combustion experiments as a prototypical hydrocarbon fuel. While the formation of polycyclic aromatic hydrocarbon (PAH) in n-heptane combustion has been studied preferably in premixed flames, this study aims to investigate the combustion chemistry of n-heptane in less-studied diffusion flame and highly rich high-temperature homogeneous oxidation configurations by using a counterflow burner and a flow reactor, respectively. This work addresses the formation of higher-molecular species in the mass range up to about 160 u in both configurations. Samples are analyzed by time-of-flight (TOF) molecular beam mass spectrometry (MBMS) using electron-impact (EI) and single-photon ionization (PI). Highly resolved speciation data are reported. Laminar flow reactor experiments cover a wide temperature range. Especially the measurements at low temperatures provide speciation data of large oxygenates produced in the low-temperature oxidation of n-heptane, which are scarce in the literature. Important precursor molecules for PAH and soot formation, such as C9H8, C10H8, C11H10, and C12H8, are formed during the high-temperature combustion process in the counterflow flame, while oxygenated growth species are observed under low-temperature conditions, even at the fuel-rich equivalence ratio of ϕ=4.00.Numerical modeling for both conditions is performed by using a newly developed kinetic model of n-heptane, which includes the n-heptane and PAH formation chemistry with state-of-the-art kinetic knowledge. Good agreement between model predictions and experimental data of counterflow flame and flow reactor is observed for the major species and some intermediates of n-heptane oxidation. While the concentrations of benzene and toluene measured in the counterflow burner are well-reproduced, the numerical results for flow reactor data are not satisfactory. Differences are found between the formation pathways of fulvene, from whose isomerization benzene is produced in diffusion flame and flow reactor.

Phase-selective laser–induced breakdown spectroscopy in flame spray pyrolysis for iron oxide nanoparticle synthesis

The flame spray pyrolysis of iron oxide nanoparticles using the new reference nozzle SpraySyn is a key step towards the understanding of the coupling of physicochemical steps such as precursor atomization, spray evaporation, combustion, particle formation and growth. Owing to the countless available solvents and precursors, systematic investigations are necessary to fully understand the impact of precursor formulation on the reaction route and, hence, the particle properties. In this work, the recently developed phase-selective laser-induced breakdown spectroscopy (PS-LIBS) technique is applied to an external mixing spray flame reactor in order to study iron oxide particle formation along the axial centerline of the spray under varying precursor solutions. The addition of 2-ethylhexanoic acid (EHA) to precursors is investigated and significant differences in the evolution of the atomic emission spectra are observed, enabling the differentiation between droplet-to-particle and gas-to-particle routes in situ. The observations from PS-LIBS are in good agreement with TEM images and XRD, where haematite (α-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) were observed. Raman spectroscopy (RS) in particle-free spray-flames revealed a significant gas-phase temperature difference of about ΔT∼500 K under addition of EHA to the spray and demonstrated accurate temperature measurements up to droplet rates of 103 Hz. The experimental results allow deep insights into the spray flame combustion and particle nucleation kinetics. Moreover, they can be coupled with population balance models and be used for the validation of numerical simulations.

Excitation–Emission Matrix Spectroscopy for Analysis of Chemical Composition of Combustion Generated Particulate Matter

Analysis of particulate matter (PM) is important for the assessment of human exposures to potentially harmful agents, notably combustion-generated PM. Specifically, polycyclic aromatic hydrocarbons (PAHs) found in ultrafine PM have been linked to cardiovascular diseases and carcinogenic and mutagenic effects. In this study, we quantify the presence and concentrations of PAHs with lower molecular weight (LMW, 126 < MW < 202) and higher molecular weight (HMW, 226 < MW < 302), i.e., smaller and larger than Pyrene, in combustion-generated PM using excitation-emission matrix (EEM) fluorescence spectroscopy. Laboratory combustion PM samples were generated in a laminar diffusion inverted gravity flame reactor (IGFR) operated on ethylene and ethane. Fuel dilution by Ar in 0% to 90% range controlled the flame temperature. The colder flames result in lower PM yields however, the PM PAH content increases significantly. Temperature thresholds for PM transition from low to high organic carbon content were characterized based on the maximum flame temperature (Tmax,c ∼ 1791 to 1857 K) and the highest soot luminosity region temperature (T*c ∼ 1600 to 1650K). Principal component regression (PCR) analysis of the EEM spectra of IGFR samples correlates to GCMS data with R2 = 0.988 for LMW and 0.998 for HMW PAHs. PCR-EEM analysis trained on the IGFR samples was applied to PM samples from woodsmoke and diesel exhaust, the model accurately predicts HMW PAH concentrations with R2 = 0.976 and overestimates LMW PAHs.

Contactless Flame Reactor State Parameter Investigation Using a Broadband mmWave Radar

In this article, we present a novel contactless method for the state parameter surveillance of flame reactors that are used in the production of nanoparticle powders. By means of a highly stable and broadband millimeter-wave radar system and a precise signal phase processing, the change in three different state parameters, i.e., pressure, vapor content, and nanoparticle density, is monitored. Besides fundamentals regarding the signal processing, the influences of the state parameters on the radar signal are considered theoretically and investigated with measurement results that are presented and discussed in detail.

Effect of Spray Parameters in a Spray Flame Reactor During FexOy Nanoparticles Synthesis

Synthesis and characterization of FexOy nanoparticles were carried out in order to study reaction parameters influence in a spray flame reactor. FexOy powders were prepared with three different precursors aiming to understand how the reactor conditions, dispersion gas flow, and precursor solution flow affect morphology, shape, particle size distribution, crystalline phases, and residue content of the obtained materials. Thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD), and Raman spectroscopy were employed to characterize the materials. In addition, magnetic behavior of the obtained samples was evaluated. It was found that the evaluated parameters influenced the residue contents obtaining weight changes from 10 to 35%. Particle size distribution centers also showed differences between 17 and 24 nm. By XRD, Raman, and TEM, the presence of hematite (a-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) was evidenced and explained based on the gas and liquid content in the flame. Additionally, the saturation magnetization was measured for selected samples, obtaining values between 26 and 32 emu g−1. These magnetic measurements were correlated with the crystalline phase composition and particle size distributions.

INVESTIGATION OF LPG SOOTING DIFFUSION FLAME BY RAINBOW SCHLIEREN DEFLECTOMETRY

Rainbow schlieren deflectometry was employed to characterize the flame structure of unsteady laminar liquefied petroleum gas (LPG) jet diffusion flame. The schlieren images were acquired at 4000 Hz sampling rate for sooting LPG flame at Re = 500, and Abel inversion was employed to estimate local field refractive index difference. The a priori relationship between the refractive index difference and temperature was established using the opposed flow flame reactor concept. The peak temperature observed in the near-field region varies with axial location from 1000 K to 1700 K, which falls in the range of typical sooting flame. The sooting flame has depicted a typical flicker behavior of the unsteady laminar diffusion flame. Flicker behavior and flame puff formation could be attributed to the interaction of buoyancy-sustained outer vortical structure with the flame surface. It was observed that additional air entrainment during puff formation leads to higher temperatures in the puff (1700 K), which leads to better oxidation of carbon soot and its precursors at down-stream locations, a unique feature of sooting flames. Irrespective of whether space–time evolution at any axial location or frequency spectrum analysis of temporal signal of hue at any spatial location or the amplitude–time signal of decomposed mode from proper orthogonal decomposition (POD) analysis of color schlieren images, is employed the global unique flicker frequency of 13.33 Hz was observed in the near-field LPG diffusion flame. Interestingly the first two dominant energy modes of POD analysis correspond to flow features indicating strong ambient air entrainment pointing towards the role of outer vortical structures on flame flickering phenomena.

Nanostructure transition of young soot aggregates to mature soot aggregates in diluted diffusion flames

In this study, the structural properties of soot produced in diffusion flames are analyzed to elucidate the formation of mature aggregates from large young particles. Soot samples are generated in a laminar diffusion inverted gravity flame reactor (IGFR) operated on methane, ethane, and ethylene with Ar dilution to reduce the flame temperature. Soot produced in temperature ranges from 1495K to 1568 K contains 100 nm–300nm particles with (i) isotropic or (ii) multiple core structures, supporting a soot maturation pathway where one young soot particle evolves into a mature fractal aggregate via an internal nucleation route. During the process, these large amorphous particles can form internal voids as the particle loses mass due to pyrolysis or oxidation. Transmission electron microscopy (TEM) shows that young soot aggregates contain a higher fraction of shorter fringes and highly curved aromatics (11% vs. 23%), which is in agreement with their higher organic carbon content (3.3%–5.4% vs. 12.1%–28.8% wt.). Increasing the flame temperature reduces the curvature of polycyclic aromatic hydrocarbons (PAHs) and allows for more efficient layer stacking as indicated by a higher percent of stacked fringes. For these gaseous fuels, carbonization appears to be primarily a function of the flame temperature and independent of the fuel composition.

Characterizations of Ag doped ZnO particles via flame pyrolysis method for degradation of methylene blue

Flame pyrolysis is widely used for the fabrication of particles because of great crystallinity and fine size distribution of the products. In this research, ZnO-Ag particle materials have been favourably made by flame pyrolysis. The impacts of Ag loading varying from 0 to 20 wt% on the photocatalytic activity of ZnO-Ag particle under ultraviolet (UV) and sunlight irradiations were studied. ZnO-Ag particles were fabricated based on zinc acetate dihydrate (Zn(CH3COO)2.2H2O) 0.1 M and silver nitrate (AgNO3) as a precursor inside a flame reactor. Crystallinity and morphology of ZnO-Ag particles were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. SEM analysis showed that the particles had irregular sphere-like shapes. The XRD patterns showed that the produced ZnO had a wurtzite structure with different crystallite sizes. XRD analysis also confirmed the existence of Ag particles in ZnO-Ag particles after the addition of Ag greater or equal to 5 wt%. The existence of Ag was indicated by the appearance of the XRD peak at 38.1°. The peak at 38.1° increased with the increase of Ag loading. Finally, the photocatalytic activity was evaluated by estimating the degradation of methylene blue aqueous solution under UV and sunlight irradiations. It noted that the most excellent photocatalytic performance was achieved at 5 wt% Ag loading for both irradiations.