Combustion Of Powders Research Articles

Sodium fluoroaluminate promoting the combustion of micron-sized aluminum powder with different particle sizes in carbon dioxide

To improve the ignition and combustion performance of micron-sized aluminum powder (m-Al) in CO2, a self-made pipe furnace experimental platform was established to study the effects of sodium fluoroaluminate (Na3AlF6) on the ignition delay times, combustion processes, combustion efficiencies, and combustion products of 1–2, 5, and 30 μm aluminum (m-Al1, m-Al5, and m-Al30) powders in CO2 at 1000 °C. The combustion phenomenon was recorded by a high speed camera. The ignition delay time was obtained by post-processing the sequential images. m-Al containing Na3AlF6 has a lower initial reaction temperature and a shorter ignition delay time than those of m-Al without Na3AlF6 addition. The effect of Na3AlF6 content on the ignition delay time is different for m-Al with different sizes. The ignition delay times for m-Al1 and m-Al5 increase with increasing the Na3AlF6 content, while the corresponding values of m-Al30 first increase and then decrease. The combustion products were subjected to the analyses of morphology, composition, and combustion efficiency. The oxidation shell of Al is fluorinated by Na3AlF6, thereby promoting its ignition and burning. The combustion efficiency of m-Al is significantly enhanced, especially for m-Al30. The effect mechanism of Na3AlF6 on the ignition and combustion of m-Al in CO2 was discussed.

Compound utilization of construction and industrial waste as cementitious recycled powder in mortar

This paper investigates the utilization of powder recycled from construction and industrial waste in the construction industry. To alleviate the negative environmental impact of cement industry, recycled concrete powder (RCP) and spontaneous combustion gangue powder (SCGP) were used as supplementary materials to substitute part of the cement. Six recycled mortar mixes were designed with various contents of RCP and SCGP. In this test, the total replacement ratio of the recycled powder (RCP and SCGP) varied from 0 to 50%. The mechanical and durability properties of the recycled mortar were investigated in combination with microstructure analysis. The findings reveal that 15% RCP and 15% SCGP is a suitable combination for the recycled mortar to maintain mechanical properties comparable to those of the control mix. When the total substitution ratio of RCP and SCGP does not exceed 30%, their incorporation leads to better durability properties of the recycled mortar compared to those of the mix containing one type of recycled powder. Consistent with the mechanical and durability analyses, the microstructure analysis reveals that the combination of 15% RCP and 15% SCGP contributes to a dense structure of the mortar, which benefits from the synergetic effect of the relatively high pozzolanic reactivity of SCGP and the filling ability of RCP.

Preparation of Cu–Cu2O–CuO by solid combustion ignited by dielectric barrier discharge and its activity towards p-nitrophenol reduction

Dielectric barrier discharge induces solid powder combustion at room temperature and atmosphere to prepare a high-activity catalyst for p-nitrophenol reduction.

Combustion of metal powder with dinitrogen tetroxide

Here we present analysis of a novel reactive material system that employs dinitrogen tetroxide (N 2 O 4 ) as a liquid oxidizer with metal powder fuels. The oxidizer was added to micron scale aluminum and zirconium powders by a remote injection system. When ignited with a high voltage spark, the mixtures were observed to possess reactivity comparable to nanocomposite reactive materials, with open-tube flame expansion velocities from 500 to 1400 m/s depending on fuel/oxidizer ratio and tube diameter. Temperatures were observed to range from 3000 to 3500 K as measured with gray body fits to 16-channel time-resolved pyrometer and time-integrated spectrometer data. These values were significantly below calculated adiabatic flame temperatures, which we attribute to local deviations from stoichiometry and kinetic/energetic limitations similar to those observed in studies of particles burning in high pressures gaseous oxidizers. Al/N 2 O 4 reactivity was found to be most likely limited by the vaporization of the metal from the particle surface and Zr/N 2 O 4 was limited by slower burning and complex interactions involving the solubility of nitrogen and oxygen in the molten Zr. We also discuss the potential for these materials to be used to create an “on/off” reactive material, since N 2 O 4 can be added remotely and driven to evaporate via vacuum or purge of inert gases to return it to a safe condition.

Process loss prevention of petrochemical process: A case study of the flashing accident of the storage tank on acrylonitrile-butadiene-styrene powder in Taiwan

Qualitative analysis, process hazard analysis, thermal evaluation, and fault tree analysis were applied to a flashing accident involving a storage tank that contained acrylonitrile-butadiene-styrene (ABS) powder in Taiwan. The accident was caused by combustible powder attached to the inner wall of the tank reaching a high temperature and then melting. Thereafter, the molten powder became glue-like and dropped onto the ABS powder, burning at the tank bottom, causing decomposition of the styrene and butadiene derivatives as well as other combustible gases. The high concentration of combustible powder and low ignition temperature triggered the powder, initiating a dust explosion. Finally, we analyzed the findings of each method and examined the properties of ABS powder, realizing that the root cause of the accident included an insufficient understanding of the characteristics of ABS and the failure to comply with the management procedures of hot work. Recommendations and countermeasures were proposed that could proactively ameliorate process safety.

Ignition of zirconium powders placed near an electrostatic discharge

Abstract Electrostatic discharge (ESD) or spark produced by breakdown of a gap while discharging a capacitor is a common ignition stimulus for powders of reactive and energetic materials. It is a safety hazard, but is also used to initiate pyrotechnic formulations and as a characterization method of reactivity of energetic materials. In previous experimental studies, the powder served as one of the ESD electrodes. Ignition was found to be caused by Joule heating, with the main heat release by current passing through points of contact between particles. However, ignition may occur when the ESD does not pass directly through the powder. ESD generates a shock wave, which can lift the powder from a substrate even if the substrate is not an electrode. ESD also generates a plasma kernel heated to ca. 10,000 K, which exists for hundreds of µs, often much longer than the ESD current. Here, the effect of the ESD-induced shock and plasma on a reactive powder was studied experimentally for the first time. A thin layer of Zr powder was placed on a substrate located under a spark gap between two pin electrodes. Photo-sensors and high-speed video were used to document ignition and combustion events. The ESD energy and distance from the spark gap and powder were varied. At close distances, particles ignited consistently. Distance limits were determined, beyond which ignition was no longer observed. Higher ESD energies as well as longer ESD pulses led to ignition at greater distances. Ignition involved two distinct processes. First, submicron particles were lifted from the substrate on a time scale of single microseconds, interacted directly with the plasma kernel, and combusted. Optical emissions from this combustion lasted 100 – 600 µs, as expected for the burn time of submicron Zr particles in air. The second ignition event occurred several milliseconds later. It involved a flame propagating through Zr powder aerosol or combustion of individual lifted particles. This event was caused by coarser Zr particles radiatively heated during ESD. Importantly, the powder was aerosolized by convective flows caused by the rising plasma kernel making it possible for the self-heating of particles oxidizing in air to eventually lead to their ignition and combustion. Observed times for these delayed ignition and combustion events were in the order of tens of milliseconds.

Combustion of titanium and chromium powders in the co-flow of a nitrogen-argon mixture

The combustion of the titanium and chromium powders in the co-current filtration mode was considered. We considered an original equipment that allows us to study the combustion of metal powders in a co-flow gas stream. It was demonstrated that the proportion of argon in a binary gas mixture has a greater influence on the burning temperature of titanium powder than the specific flow rate of the gas mixture. It was found that the actual burning temperature of chromium in the forced filtration mode is higher than the adiabatic temperature and the phenomenon of superadiabatic heating takes place. This method has high energy efficiency and allows you to get nitrides without the use of high pressures. It was found that co-current filtration promotes the formation of Cr2N nitride.

Synthesis of Porous Composite Material with the Combustion of Titanium and Boron Powders and Nickel-Clad Aluminum Granules

Synthesis of Porous Composite Material with the Combustion of Titanium and Boron Powders and Nickel-Clad Aluminum Granules

Experimental study of dissociation of double gas hydrate at various combustion methods

The dissociation during combustion of a propane-methane gas hydrate double powder is experimentally investigated. Gas hydrate combustion is implemented in four ways: 1) induction heating; 2) radiation and convective heating in a muffle furnace; 3) combustion without forced gas flow; and 4) combustion in the presence of forced air convection u a. The maximum J is achieved by burning granules of gas hydrate powder on a metal surface with induction heating, where J is the specific dissociation rate. The minimum of J corresponds to the combustion of a layer of gas hydrate powder in the absence of forced air flow. With an increase in the velocity air convection u a from 0 to 1.2 m/s the J increases and reaches a maximum. A further increase in u a leads to a decrease in J. For u a > 3.5 m/s combustion does not occur.

Study on Mass Transfer of Ash during Bamboo Powder Combustion

Study on Mass Transfer of Ash during Bamboo Powder Combustion

Chromium nitride synthesis in co-flow filtration mode

In this work, we considered an original setup that allows us to study the combustion of metal powders in a co-flow gas stream, and also presents the results of experimental studies on the combustion of chromium powder in a confined nitrogen-containing gas stream. This method has high energy efficiency and allows to get nitrides without the use of high pressures. The study of chromium combustion is justified by its high melting point at a relatively low exothermicity, which eliminates the influence of melting of the initial powder and synthesis products on the filtration process. This article presents the results of combustion of chromium powder with particle size δ = 63÷80 µm and δ = 500÷1000 μm. X-ray phase studies of the obtained powders were carried out. The effect of nitrogen-containing gas consumption on the degree of nitriding of combustion products is shown. It is established that the forced filtration mode allows the synthesis of non-stoichiometric chromium nitride Cr2N. The nitrogen content in the obtained Cr2N samples reached 9.6%.

3-10 竹粉燃焼時の灰の物質移動に関する研究

3-10 竹粉燃焼時の灰の物質移動に関する研究

A Reevaluation of the Death of Vincent van Gogh: Suicide or Murder? The Need for a Definitive Autopsy.

Vincent van Gogh died on July 29, 1890, from an apparent gunshot wound to the belly sustained approximately 30 hours earlier on July 27. Although little is known how Vincent sustained his mortal wound, art historians have long believed that the death was the result of a suicide, a widely accepted "truth" for the mysterious death of the then unknown and now iconic artist. The basis and validity of this suicide narrative is still very hotly debated among van Gogh scholars to this day. We dug deeper into all the circumstantial evidence and testimonies to arrive at a comprehensive overview of the probability that it was likely impossible for Vincent to self-inflict his mortal wound.We used all the available circumstantial evidence related to the day Vincent van Gogh was wounded to present the information and conclusions as if we were before a judge as expert witnesses to answer the question: suicide or murder? If Vincent did not shoot himself in the belly (a red flag in and of itself), whoever inflicted that penetrating wound into his abdomen murdered him. In our study, results from firing the same model revolver that allegedly killed Vincent from various ranges (direct contact, intermediate, and distant) demonstrated within a reasonable degree of medical probability (greater than 50%) that it was not probable for Vincent van Gogh to shoot himself without a described powder burn.With little forensic evidence to rely on 130 years after the suspicious event, many have suggested a respectful exhumation and graveside autopsy utilizing 21 century techniques to bring resolve to this 19 century cold case. This crime, whether suicide or murder, has generated renewed interest and numerous questions surrounding the suspicious death of the most iconic artist of the 19th century. These missing forensic facts will remain buried with all the secrets Vincent took with him to his grave, unless a definitive autopsy is performed. What an autopsy could add to our forensic fact basis and understanding of this intriguing cold case is enormous and further delineated as the next step to answer these difficult, otherwise unanswerable questions and allow us to finally sign off on his death certificate with certainty.It is clearly impossible to definitively prove suicide or murder, but it is also impossible to disprove murder given the data and arguments offered in this analysis. A physician's opinion is based on the material available to him, and in this case, "our opinion as to the cause and manner of death is based on the limited amount of forensic information available. It is, therefore, our opinion, based on that limited information that in all medical probability, the cause of death is not a self-inflicted wound by Vincent van Gogh, and, thus, in all medical probability, a homicide."

Unsteady 3-D RANS simulations of dust explosion in a fan stirred explosion vessel using an open source code

Dust explosion is a constant threat to industries which deal with combustible powders such as woodworking, metal processing, food and feed, pharmaceuticals and additive industries. The current standards regarding dust explosion venting protecting systems, such as EN 14491 (2012) and NFPA 68 (2018), are based on empirical correlations and neglect effects due to complex geometry. Such a simplification may lead to failure in estimating explosion overpressure, thus, increasing risk for injuries and even fatalities at workplaces. Therefore, there is a strong need for a numerical tool for designing explosion protecting systems. This work aims at contributing to the development of such a tool by (i) implementing a premixed turbulent combustion model into OpenFOAM, (ii) verifying the implementation using benchmark analytical solutions, and (iii) validating the numerical platform against experimental data on cornflour dust explosion in a fan-stirred explosion vessel, obtained by Bradley et al. (1989a) under well-controlled laboratory conditions.For this purpose, the so-called Flame Speed Closure model of the influence of turbulence on premixed combustion is adapted and implemented into OpenFOAM. The implementation of the model is verified using exact and approximate analytical solutions for statistically one-dimensional planar and spherical turbulent flames, respectively. The developed numerical platform is applied to unsteady three-dimensional Reynolds Averaged Navier-Stokes simulations of the aforementioned experiments. The results show that the major trends, i.e. (i) a linear increase in an apparent turbulent flame speed St,b with an increase in the root mean square (rms) turbulent velocity u' and (ii) and an increase in St,b with an increase in the mean flame radius, are qualitatively predicted. Furthermore, the measured and computed dependencies of St,b(u') agree quantitatively under conditions of weak and moderate turbulence.

Propagation of the Explosion of a Solid Propellant in a Rigid and Resistant Partitioned Structure

ABSTRACT The aim of this work is to present a novel numerical study applied to the chain propagation of the explosion of a special kind of propellant and the formation of overpressures inside a rigid and resistant partitioned vessel. A calculation methodology is developed to simulate the transmission of the explosion from one compartment to another adjacent compartment by the means of the hot flow through the shared orifice and finally to generalize this novel methodology for propellants to rigid and resistant complex multi-partitioned structures. The basic characteristics of the model have been developed for the ignition and the combustion of classical propulsive powders in a one-compartment vessel and adapted to a solid propellant such hexogen with appropriate parameters linked to simplified kinetics. A simple representation of the combustion phenomena based on energy transfers and the action of specific molecular species is presented. The model allows the study of various parameters such as the initial thermodynamic conditions, the location of the ignition energy, and the size of the inner openings or the vent areas. The model calculations have been compared with data obtained in the course of experimental works and indicate interesting preliminary trends.

SHS in the Si–CO2 System: Composition/Structure of Combustion Products

Composition/structure of products formed upon frontal combustion of Si powder in gaseous carbon dioxide at P(CO2) = 0.4–5.0 MPa were characterized by chemical analysis, XRD, and SEM/EDS. Combustion products were found to contain SiC, unreacted Si, and SiO2. Our results may turn interesting to those engaged in fabrication of heat-resistant Si–O–C ceramics.

Synthesis of porous composite material at combustion of titanium and boron powders and nickel-clad aluminum granules

Self-propagating high-temperature synthesis (SHS) was carried out in the Ni-Al-Ti-B system. The aim of the study was to obtain a composite material with ceramic and intermetallic frameworks and with a developed porous structure in the combustion mode in one process step from the «boron-titanium-large nickel-clad aluminum granules» powder system pressed by sequential batch compaction. The synthesis process featured by a stage nature where a highly exothermic reaction between titanium and boron formed a boride matrix with developed open porosity and acted as a «chemical furnace» to maintain the reaction in clad granules resulting in nickel aluminides. The aluminide melt impregnated the porous diboride matrix. The synthesis stages are reflected in the process thermograms. The final structure of the product features multi-scale porosity characterized by large round pores (~100÷160 μ m in diameter) with the location corresponding to the position of clad granules in the original powder system. Small (0.1-5.0 μ m) and some average-sized (up to 15 μ m) diboride matrix pores are filled with nickel aluminides. The resulting material has a composite structure in analogy with interpenetrating frameworks - ceramic (TiB 2 ) and aluminide (NiAl, Ni 3 Al). The diboride matrix is formed by randomly oriented small hexagonal crystals with a size of mainly ~0.2÷1.0 μm across. Diboride crystalline grains increase in size to 2-6 um in diameter and 0.5-2.0 μm in thickness near the macropores becoming strongly plate-shaped. The main size of intermetallic layers filling the pores between the diboride crystalline grains is ~0.2÷1.0 μm.

Developing the environmentally friendly technologies of combustion of gas hydrates. Reducing harmful emissions during combustion

In recent years, there has been a sharp increase in interest in the development of environmentally friendly technology for burning methane gas hydrate. In addition to solving energy problems, gas hydrates will help to make significant progress in solving environmental problems. The use of gas hydrate combustion technology is shown to reduce harmful emissions. In this work, experimental studies on the combustion of double hydrate powder of propane-methane have been performed at five different ways of combustion organization. Powder heating was realized using: 1) induction heating; 2) radiation and convective heating; 3) using a hot metal body; 4) combustion without forced gas flow and 5) combustion in the presence of forced and free air convection. Currently there has been neither a comprehensive study of the combustion of double gas hydrates, nor a comparison of the combustion efficiency for different methods; besides, no data on emissions have been obtained. The maximum dissociation rate is implemented with the use of induction heating. Using a gas analyzer the concentration of gases during the gas hydrate combustion has been measured. Comparison of different ways of combustion allows optimizing the combustion efficiency of gas hydrates.

Experimental Study of Influence of Fuel Ratio on Combustion Characteristics of Diesel-Wetted Wood Powder

In this study, experiments were conducted to examine the influence of the fuel ratio (i.e., the ratio of diesel mass to wood powder mass) on the combustion characteristics of diesel-wetted wood powder, in which 0# diesel and poplar wood powder were used and well mixed. The fuel ratios were set to 0, 0.5, 1.0, 1.5, and 2.0. Fire behaviors, temperature distributions, mass loss rates, and CO concentrations were measured and analyzed. The results showed that because of the coupled effect of evaporation and the capillary force, the ignition point of diesel-wetted wood powder (less than 3°C) dropped dramatically as compared with that of pure wood powder (higher than 280°C) and pure diesel (higher than 107°C). At the early stage of combustion, diesel is lifted upwards by the capillary force, increasing both the concentration of diesel vapor and the temperature at the surface. When the surface temperature reaches that of the pyrolysis of wood powder, considerable pyrolysis gas emerges and combusts. As the flammable gas is consumed gradually, carbon combusts prominently when plenty of oxygen diffuses to its surface. Regarding the influence of the fuel ratio, the results showed that in cases with lower fuel ratios, the combustion was not self-sustainable. When the fuel ratio was relatively high, the temperature at the flame center was lower owing to incomplete combustion. More CO could be found in cases with higher fuel ratios in the early and late stages of combustion. The results could help to improve knowledge regarding combustion of fuel-wetted wood powder.

Characterization of Ti powders mixed with TiO2 powders: Thermal and kinetic studies

The fire and explosion risks of metal powders admixed with solid inertants have been extensively investigated for many years. However, it remains unclear why such solid mixtures have high potential fire and explosion risk even when mixed with high percentages of non-combustible solids. This paper investigates how to interpret these risks, from a microscopic perspective, with thermal and kinetic parameters including initial ignition temperature, mass unit exothermic energy, activation energy and risk index of spontaneous combustion. The results show that the initial ignition temperature based on TG (Thermogravimetry) analysis is related to ignition sensitivity, and increased with percentage of admixed solid inertant. The unit mass exothermic energy based on DSC (Differential scanning calorimetry) analysis is related to flame spread velocity. Activation energy and the risk index of spontaneous combustion can be used to explain the reactivity and spontaneous combustion hazard, respectively, of metal powders. We conclude that thermal and kinetic parameters may provide another way to describe the fire and explosion risk of combustible powders, especially for nano metal powders due to the laboratory safety in the normative tests for explosion parameter determination.