Aluminum Dust Research Articles

Observation of self-excited oscillations in DC glow discharge dusty plasma

We present a detailed experimental study of discharge current oscillations in a planar cathode plasma with poly dispersed alumina dust particles. Our experimental measurements suggest that surface density of dust particles play an important role together with cathode spots, in deciding self excited oscillating regime or stable dust cloud regime. Experiments conducted with dust particles density below the critical limit shows self excited oscillations. Operating above the critical limit, a dust cloud levitated in the sheath region was observed.

Aluminum dust concentration detection based on LSTM-Kalman filter

Industrial dust emissions present serious hazards, including respiratory issues and explosion risks. Traditional dust concentration detection methods are often compromised by environmental factors. This study introduces a novel FFT-KF-LSTM-NET model to predict high-concentration aluminum powder levels, utilizing 128 sets of electrostatic induction measurement data. By applying the Fast Fourier Transform (FFT) to eliminate low-frequency interference, integrating Long Short-Term Memory (LSTM) networks for advanced time series analysis, and using the Kalman Filter (KF) for rapid model convergence, this approach significantly enhances prediction accuracy. The model achieves an 82% improvement in Mean Squared Error (MSE), reducing it to 0.1336, outperforming traditional methods. Furthermore, by modeling the voltage signal generated by charged dust particles in the electrostatic induction sensor's sensing area and using the first derivative of the voltage signal as a learning feature, the model's prediction speed is increased from 1.5 s-2 s–0.5 s, with improved anti-interference capabilities. These advancements position the FFT-KF-LSTM-NET model as a crucial tool for real-time, reliable dust concentration detection in industrial environments.

Experimental study of discharge current oscillations with dust particles

We present a detailed experimental study of discharge current oscillations in a planar cathode plasma with poly-dispersed alumina dust particles. The dominant frequency of oscillation depends on the discharge voltage, operating pressure, and amount of dust particles placed on the cathode. The power-law variation in the dominant frequency with different external operating parameters is presented. Experimental observations suggest that the dominant mechanism behind the generation of these oscillations is the cathode spot injection of sub-micron-sized dust particles. The cathode spots also aid in the generation of fine dust particles. The threshold limit on dust particle density dispersed on the cathode suggests that below the threshold limit, the fine particles depleting the electrons play an important role and lead to the generation of self-excited oscillations. Operating above the threshold limit, a stable dust cloud was observed together with the suppression of self-excited oscillations.

Effect of L-glutamic acid as hydrogen generation inhibitor on aluminum waste

Aluminum on reaction with water generates hydrogen, aluminum waste (AW) under moist condition causes hydrogen blast. To inhibit the evolution of hydrogen during the reaction of aluminum with water, environmentally friendly L-glutamic acid (GA)was utilized. The results of hydrogen generation experiment show that 0.3 g GA with 0.5 g AW and 0.5 g sodium borohydride (NH) has the ability to suppress the hydrogen generation reaction. The XRD, FTIR and SEM analysis indicate the presence of protective covering film of GA is formed on the surface of AW, blocking the reaction to occur between aluminum with water. This study addresses the lack of research on inhibitors for hydrogen fire blasts when removing wet aluminum dust.

Delayed admission to hospital with proper prehospital treatments prevents severely burned patients from sepsis in China: A retrospective study

BackgroundSepsis is one of the major causes of morbidity and mortality in burn patients. However, the optimal timing of admission which can minimize the probability of sepsis is still unclear. This study aims to determine the optimal time period of admission for severely burned patients and find out the possible reasons for it. Method185 victims to the Kunshan factory aluminum dust explosion accident, which happened on August 2nd, 2014, were studied. The optimal cutpoint for continuous variables in survival models was determined by means of the maximally selected rank statistic. Univariate and multivariate analyses were further conducted to verify that admission time was not a risk factor for sepsis. Subgroup analyses were performed to find out possible contributing factors for the result. ResultThe cutoff point for admission time was determined as seven hours, which was supported by the survival curve (p < 0.001). Multivariate analysis showed that, in our study population, delayed admission time was not a risk factor for sepsis (HR = 0.610, 95 %CI = 0.415 - 0.896, p = 0.012). Subgroup analyses showed that “Tracheotomy before admission” (p = 0.002), “Whole blood transfusion” (p < 0.001), “Hemodynamic instability before admission” (p = 0.02), “Has a burn department in the hospital” (p = 0.009), “Has a burn ICU in the hospital” (p < 0.001), “Acute heart failure (AHF)” (p = 0.05), “acute respiratory distress syndrome (ARDS)” (p = 0.05) and “GI bleeding” (p = 0.04) were all statistically significant. ConclusionIn our study population, we found that delayed admission time was not a risk factor associated with a reduced incidence of sepsis among severely burned patients. This might be attributed to variations in prehospital treatments (whole blood transfusion and tracheotomy), whether the hospital had a burn department/ICU, and certain complications (AHF, ARDS and GI bleeding). It can be inferred that early prehospital care plays a crucial role in reducing sepsis risk among severe burn patients.

Simulation and Experimental Study on the Explosion Characteristics of Aluminum Dust in the 5-L Explosion Container

ABSTRACT The CFD software was applied to conduct numerical simulation of the aluminum powder explosion and the study focused on analyzing the pattern of dust diffusion in the 5-L column explosion model containing aluminum powder at a concentration of 700 g/m 3 , and then comparing the simulated pressure change over time with experimental data. The research also examined how different levels of aluminum dust concentration affect the pressure of explosions, the rate at which explosion pressure increases, and the speed of the flame reaching the wall. The findings indicate that, during the pressure time course, the simulation process yields explosion pressure and rate of rise in explosion pressure values for a specific concentration of aluminum dust that deviate by 2% to 19% from experimental results. This suggests that the model utilized in this study possesses a certain level of reliability and it is observed that the variation patterns of explosion pressure and rate of rise in explosion pressure for aluminum dust at different concentrations differ between simulation and experimentation. In the experimentation, at concentrations of 500 g/m 3 and 900 g/m 3 , the explosion pressure and rate of rise both reached their maximum values. Furthermore, the speed of the flame reaching the wall is directly related to the level of concentration.

Hazard evaluation of ignition sensitivity and explosion severity for aluminum and aluminum powder-petroleum ether mixtures

The safety implications of aluminum powder and petroleum ether have garnered significant attention as two typical materials in the production process of energetic materials. To investigate the effect of the common solvent petroleum ether on the ignition and explosion characteristics of aluminum powder, ignition energy, flame propagation characteristics, and explosion pressure of three aluminum powder sizes and their mixtures with petroleum ether through a Hartmann tube test device and a 20 L spherical explosion vessel test system. Findings show that the ignition energy of aluminum powder initially decreases and then increases with the increase of petroleum ether content. At the petroleum ether concentration of 5.5 % and 11 %, the minimum ignition energies of the mixed systems of Al-Flake, Al-T4, and Al-T2 are 1–20 mJ, 5–30 mJ, 450–485 mJ, and 1–20 mJ, 5–25 mJ, 440–480 mJ, respectively. Lower than the minimum ignition energy of the original sample (1–30 mJ, 10–40 mJ, 470–510 mJ), indicating that the aluminum powder dust containing low concentration solvent (5.5%, 11 %) is more sensitive to an electric spark. The ignition energy of the mixed system is rather increased when the content of petroleum ether is further increased to 16.5 %. On the contrary, the probability of ignition and the electric spark sensitivity are decreased. With the addition of petroleum ether to Al-Flake and Al-T4, the flame propagation speed slightly decreases and the phase duration lengthens. The flame propagation characteristics and combustion state of Al-T2 with large particles remained largely unchanged after the addition of petroleum ether. During the 20 L spherical explosion vessel test, the maximum explosion pressure and explosion index of the mixed samples initially increase and then decrease with the increase in petroleum ether concentration. A small quantity of petroleum ether intensifies the reaction intensity of aluminum dust. At an aluminum powder dust concentration of 250 g m-3, the explosion pressure and explosion index of Al-Flake and Al-T4 peak at a petroleum ether content of 5.5 %, while Al-T2 reaches its peak at 11 %.

Dual-range emission spectroscopy for temperature measurement of laminar aluminum dust flames

Understanding the temperature fields/profiles in aluminum dust flames is critical to the design of aluminum-based sustainable fuels and the development of aluminum combustion simulation tools. Although emission spectroscopy has been applied in aluminum flames, the signals in most works were integrated along the recording path and over the whole flame and, therefore, the measurements could not provide information of the flame spatial structure. In addition, the details of the diagnostic method were scarcely introduced. This work develops a dual-range emission spectroscopy diagnostic system for 1D measurements of the liquid temperature and the flame temperature of aluminum flames. The important aspects for diagnostics, such as the instrument specifications, signal acquisition strategy, data processing, accuracy and precision, are introduced and quantified in detail. The continuous spectrum from the liquid phase of Al(L) and/or Al2O3(L), rovibrational AlO spectrum from the micro-diffusion flame, and 2D flame luminosity are recorded simultaneously. Based on Planck's law, a linear fitting method is implemented to derive a continuous spectrum temperature. A nonlinear minimization framework based on the stick spectrum is introduced to fit the AlO spectra and derive a AlO temperature. The accuracy and precision are quantified by a comparison of the average temperatures against the equilibrium temperatures and the standard deviations. The effectiveness of this technique for temperature measurements of aluminum dust flames is verified by the agreement of the continuous spectrum temperature and the AlO temperature in the post-flame region. The 1D distribution of the continuous spectrum temperature indicates the boiling of Al and the dissociation/condensation of Al2O3 from upstream to downstream through the flame. The 1D temperature distributions also present a lag of the continuous spectrum temperature compared to the AlO temperature, indicating that the continuous spectrum temperature is dominated by the Al fuel droplets and the Al2O3 caps, instead of the Al2O3 nanometric droplets.

The effect of particle size on aluminum dust dispersion based on numerical simulation

This study aimed to investigate the dispersion pattern of aluminum dust with different particle sizes in 20 L vessels by numerical simulations. Using coupled Eulerian and Lagrangian methods, the system of Navier–Stokes equations and DPM momentum balance equations were solved to obtain the dispersion process of aluminum dust with different particle sizes (25, 38, 45, 60, and 75 μm). A standard deviation of particle concentration (Spc) was proposed to characterize dispersity of dust; the smaller Spc is, the better the dispersity of dust is. On the basis of Spc, after the sample reached uniform distribution, the dust with large particle size could maintain uniform dispersion for a certain time period. By contrast, the dust with small particle size, which was more affected by the central turbulence than large dust particles, had difficulty in maintaining uniform dispersion. In addition, the use of rebound nozzles for dust dispersion led to a large turbulence intensity gradient, which significantly influenced the dust dispersion process, especially on the small particle sizes. A large amount of dust was concentrated in the near-wall region, resulting in the concentration of dust in the center of the chamber being lower than expected.

Simulation of dust grain charging under hypervelocity impact plasma environment

Dust plasma readily forms during hypervelocity impact, which serves as a source of plasma macroscopic charge separation and strong electromagnetic fields. In this study, we examine the dynamic evolution of surface charging of aluminum dust grains with micrometer or submicrometer sizes in a hypervelocity impact plasma environment based on the theory of orbital motion limited. As dust grains traverse the expanding plasma, plasma density and temperature decrease with increasing distance from the impact point. This leads to longer relaxation times for charging equilibrium (ranging from picoseconds to microseconds) and reduced equilibrium charges. The model incorporates thermionic and secondary electron emission effects on dust grain charging processes while also examining the impacts of five heating and cooling mechanisms on the thermal equilibrium temperatures of dust grains. Near the impact point, thermal equilibrium temperatures exceed aluminum's boiling point, which results in phase transition ablation processes. As dust grain temperatures increase, thermionic emission currents may dominate charging dynamics and influence final equilibrium charge numbers. High-temperature dust grains tend to acquire positive charges. Moreover, we observe that the radius of dust grains considerably affects charging processes, and smaller grain radii correspond to low equilibrium charges and longer relaxation times.

Experimental investigation on the suppression of aluminum dust explosion by sodium carbonate powder

To prevent the potential explosion accidents in industries involving aluminum powder, the effectiveness of Na2CO3 in inhibiting aluminum dust explosions was investigated using thermal methods and explosion tests. Furthermore, the surface morphologies and chemical compositions of the resultant explosion products were characterized to illustrate the inhibition mechanism of Na2CO3 powder. The results revealed a marginal increase in ignition temperatures and a decrease in combustion peak temperature as the proportion of Na2CO3 increased. Notably, within the range of 0–450%, a notable reduction was observed in both the maximum explosion pressure (from 0.68 to 0.06 MPa) and the maximum pressure rising rate (from 91.93 to 2.87 MPa/s). In particular, as the percentage of Na2CO3 increased, a gradual decrease in flame brightness and average flame velocity was observed. Moreover, a negative relationship was observed between ignition temperature and apparent activation energy with maximum explosion pressure and maximum pressure rising rate. An analysis of the explosion residues indicated the presence of Na2CO3, NaOH, Al2O3, Al(OH)3, Na(AlO)2, Na2O and unburned aluminum. The inhibition mechanisms of Na2CO3 involved heat absorption, isolation, and the consumption of free radicals. These results offer valuable insights that can aid in mitigating the risks associated with aluminum dust explosion.

Application of microencapsulated fibrous carrier inhibitors in suppressing flake aluminum dust explosion: Performance and mechanism

Flake aluminum powder (FAl), due to its larger specific surface area and higher reactivity, posing a potential threat to the process safety of involved enterprises. To mitigate the explosion caused during the production of FAl, a green composite inhibitor, Sep@CS@PA-Na, was successfully prepared in the aqueous phase using microencapsulation technology with sepiolite (Sep), chitosan (CS), and sodium phytate (PA-Na) as raw materials. The suppression of FAl explosions in a vertical combustion duct system by inhibitors with different inerting ratios (α) was investigated. The results showed that after adding Sep@CS@PA-Na with an α of 0.75, the maximum flame propagation velocity (Vmax), the average flame velocity (Vavg), and the velocity of the flame reaching the pipeline top (Vtop) decreased by 79.6%, 75.1%, and 86.2%, respectively, and the reduction of the maximum flame front pressure (Pmax) and the maximum flame pressure rise rate ((dP/dt)max) were 90.4% and 89.8%, respectively, and the peak temperature (Tp) dropped to 505°C. Combined with TG-DSC and explosion product analysis, Sep@CS@PA-Na possessed both gas-phase reaction and surface reaction suppression functions, which were mainly reflected in the dilution effect, quenching effect, and barrier effect. This work will provide technical support for the emergency prevention and control of energetic metal dust explosions.

Effect of silver inhibition on the ceramic foam as flame suppression

Aluminium dust explosions pose significant safety and economic challenges in various industrial processes. Due to this, the current research explores an innovative approach by inhibiting the silver nanoparticles (Ag NPs) to ceramic porous form substrate as a flame suppressant in order to mitigate the risks associated with these explosions. The antimicrobial and non-toxic qualities of silver are also attractive to be applied in medical and food technology. However, the interfacial adhesion between the metallic (nanosilver) and non-metallic (silica-based-ceramic) is still vaguely studied due to the mechanical and surface energy mismatch between the organic surface and the inorganic layers. From this study, the physicochemical and mechanical properties of the silver-coated ceramic foam were analyzed using X-ray diffraction, field emission scanning electron microscopy with energy dispersive X-ray, thermogravimetric analysis, and compression test. From the mechanical testing, it was found that the percentage increase of maximum load for silver-ceramic foam from the original ceramic foam was about 60%. The results indicate that silver-coated foam has a better compressive strength of 0.93 MPa as compared to 0.58 MPa by the original ceramic. The inhibition effect of Ag NPs powder on the explosion pressure evolution and flame spread mechanism of aluminium powder at different concentrations and particle sizes was tested using the Hartmann experimental system.

Effect of sludge-based suppression materials on the explosive flame characteristics of aluminium dust

A study was conducted to investigate the inhibitory effect of sludge-based phosphate-containing composite powder explosion suppressants (MPP/AMS) on aluminium dust explosion and combustion. The experiment compared the inhibition characteristics of ordinary sewage sludge particles, high-temperature alkali-modified sludge particles, phosphate-containing particles, and phosphate-modified sludge particles. The study utilized a flame propagation experimental device and an explosion pressure testing device for comprehensive research. The experimental recording devices revealed that sludge-based composite powder explosion suppressants effectively inhibit aluminium powder explosion and combustion. Thermodynamic analysis of the rapid oxidation stage was performed using the Coats Redfern (C-R) method, and validation was conducted using the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) methods. The results theoretically explain that sludge-based composite powder explosion suppressants can effectively suppress aluminium powder explosions and exhibit a blocking effect. Surface morphology and material element characterization experiments were conducted before and after the explosion, combined with pyrolysis characteristics. The analysis demonstrated that the inhibition mechanism of sludge-based composite powder explosion suppressants on aluminium powder explosion primarily involves two aspects: physical inhibition (MPP coating inhibition, porous adsorption isolation) and chemical inhibition (decomposition heat absorption, product oxidation). The theoretical findings provide evidence of the superior inhibitory effects of sludge-based composite powder explosion suppressants, offering new insights for the resource utilization of sludge waste and the development of novel explosion suppression materials.

A comparative investigation of the explosion mechanism of metal hydride AlH3 dust and Al/H2 mixture

Aluminum hydride (AlH3) is an excellent hydrogen storage material, whereas hydrogen is easily released because of the low-temperature dehydrogenation characteristic. Therefore, the explosion mechanism of AlH3 dust is explored by comparison with the Al/H2 mixture. The findings indicate that since the residual aluminum after hydrogen evolution combusts more completely, AlH3 has a higher explosion pressure value than Al/H2 mixture. However, the explosion pressure rise rate and average flame propagation velocity of AlH3 dust are lower than those of Al/H2 mixture. It is attributed to the initial free hydrogen state and initial higher hydrogen concentration of Al/H2 mixture. The key radicals that generate main explosion residues Al2O3 are AlO and O. AlH3(+M) ≤> AlH + H2(+M) has the greatest sensitivity on the formation of O and AlO. Hydrogen combustion expedites the phase transition process of aluminum dust, while their competition for oxygen is not conducive to the formation of Al2O3.

Health Risk Assessment of Inhalable Dust Exposure during the Welding and Grinding Process of Subway Aluminum Alloy Components

The subway factory industry is developing rapidly in China, but there are some occupational health risk assessments of inhalable dust in this industry. Therefore, this study aimed to explore the contamination level and health risks of dust in an aluminum alloy body workshop of subway factories in Hunan Province, China. A total of 160 dust samples were collected from the welding and grinding areas. The main elements of PM10 were analyzed. The health risks of aluminum dust and PM2.5 were evaluated. The Monte Carlo method was adopted to compare the sensitivity of the Hazard Quota (HQ) of aluminum dust and carcinogenic risk (CR) of PM2.5 to the exposure parameters for workers. The results showed that the PM10 concentration in the grinding area was higher, while the PM2.5 concentration in the welding area was higher. The metal element with a mass fraction of 27.7% was aluminum. In both areas, the probability of the aluminum dust HQ exceeding 1 was approximately 17% and 68%, respectively. The PM2.5 CR exceeded the acceptable upper limit value (1.0 × 10−4). The main risk factor of aluminum dust HQ was concentration, while the main risk factors of PM2.5 CR were concentration and exposure duration. These findings provide basic data for enhancing health risk management in the subway industry.

Numerical study on flame propagation of nano- and micron-sized aluminum dust combustion in air

A code was developed for numerical simulations of both nano- and micron-sized aluminum dust combustion in air. This code incorporates a combustion model that provides a comprehensive framework for modeling the burning of an aluminum particle under a transition regime, enabling accurate modeling of aluminum dust combustion across a wide range of particle sizes. The pseudo-transient approach was employed to solve the steady multiphase governing equations of aluminum dust combustion. The predicted variation trend of burning velocity with varying dust concentration exhibits good agreement with experimental measurements for both nano- and micron-sized aluminum dust combustion. Analyses exploring the effects of dust concentration, oxygen volume fraction and thermophoretic force on aluminum dust combustion were conducted. Simulation results indicate that introducing thermophoretic force in micron-sized aluminum dust combustion further enhances burning velocities and increases flame thicknesses compared to nano-sized aluminum dust combustion, primarily attributed to reduced gas entrainment of micron-sized aluminum particles.

Thermal insulation performance of green concrete using bio and industrial wastes: An experimental approach

The research concentrates on improving the thermal conductivity of green concrete. Cement is a high thermal conductivity material, so the aim of the research is to reduce the amount of cement for the concrete production. The aluminum dust is having low thermal conductivity based on earlier studies as well as it was proved in this research. The Portland cement has been replaced by fine aluminum dust with 5 % interval and is to be determined the optimum mix proportion. Another problem is that structural strength is lost due to improper water curing, so Calotropis gigantea milk was added to concrete to improve the curing properties. Calatropis gigantea acts as bio self-curing agent of concrete which can treat on its own without external curing without compromising its strength and durability. The dosage of Calatropis gigantea milk is taken in different percentage of cement weights, like 0.1%, 0.2%, 0.3%, 0.4% and 0.5%. The tests found in the research are workability, compressive strength, and thermal conductivity for green concrete and conventional concrete then which are compared between them. The green self-curing concrete technology can be recommended for tall structures, remote constructions, and energy saving buildings.

Inhibition characteristics research of aluminum alloy polishing dust explosion through addition of ultrafine Al(OH)3 inerting agent

Investigations into the deactivation of explosion sensitivity and reduction of flame propagation for aluminium alloy polishing wastes were carried out by the addition of ultrafine Al(OH)3 inerting agent. Meanwhile, high-purity aluminium powders with similar mean diameters were also used as a comparative study. The explosion propagation characteristics of high-purity aluminium dust and aluminium alloy polishing waste dust under different inerting ratios (ε) were tested and investigated using a standardised Hartmann tester and a developed experimental platform. The results show that the minimum ignition energy of high-purity aluminium powder is between 40 and 45 mJ, and the minimum ignition energy of aluminium alloy polishing waste is between 500 and 550 mJ, which is one order of magnitude higher than that of high-purity aluminium powder. The lower explosion limit concentration of aluminium alloy polishing waste dust is 150 g/m3, which is 53.33% of that of high-purity aluminium powder. According to the analysis of the SEM image, the main reason is that the spherical particles of high-purity aluminium dust have a folded surface and good dispersion. Compared with the smooth fibre surface of aluminium alloy polishing waste dust, the former is easier to contact with air and the contact area is larger. Therefore, in engineering practice, it is not appropriate to use high-purity aluminium dust-related explosion parameters as the basis for the risk assessment of combustion and explosion at aluminium alloy polishing work sites. In addition, as the dust concentration decreases, the combustion intensity of high-purity aluminium dust and aluminium alloy polishing waste dust also decreases, and the flame propagation appears to be a discontinuous phenomenon. The peak flame propagation velocity of aluminium alloy polishing waste is 7.368 m/s at a concentration of 300 g/m3, which is 56.85% of that of high-purity aluminium powder. As the inerting ratio increases, the propagation velocity of the explosion flame slows down. When the inerting ratio reaches 30%, the minimum ignition energy of aluminium alloy polishing waste is inerted to 1 J, and self-sustained flame propagation cannot be formed. The results show that the ultra-fine Al(OH)3 powder has a significant inerting effect and is a realistic possibility in the production of aluminium alloy polishing.

Effect of metal coating on physicochemical properties of ceramic foam for flame suppression application

Combustible dust may result in a catastrophic dust explosion with much larger accident consequences than gas explosions. In this study, porous materials are explored as a promising solution for mitigating explosions. This study focussed on the investigation of aluminium powder explosion in the influence of ceramic foam, with and without coating with non-precious nickel nanopowders. The microscopic properties and structural characteristics of the ceramic foam were analyzed using X-ray spectroscopy, X-ray diffractometry, and scanning electron microscopy. The findings revealed that the nickel-coated ceramic foams are non-uniform and almost spherical in shape, with obvious agglomerations of metallic-silica present on the strut structure. Compared to non-coated ceramic, it can be said that nickel-coated ceramic foams demonstrate a significant reduction in maximum overpressure by approximately 10%. This suggests that the interconnected micro-network structure of the nickel-ceramic walls aids in quenching the flame of the aluminium dust explosion and hence, suppressing the overpressure.